Exxon Valdez Oil Spill 

Restoration Project Final Report 

Response of Seabirds to Fluctuations 

in Forage Fish Density 

Restoration Project 0 1 163M 

Final Report 

Minerals Management Service 

Alaska OCS Region 

OCS Study MMS 2002-068 

Final Report 

John Piatt, editor 

Alaska Science Center 

U.S. Geological Survey 

10 1 1 East Tudor Road 

Anchorage, AK 99503 

December 2002 
The Exxon Valdez Oil Spill Trustee Council administers all programs and 

activities free from discrimination based on race, color, national origin, age, sex, 

religion, marital status, pregnancy, parenthood, or disability. The Council 

administers all programs and activities in compliance with Title VI of the Civil 

Rights Act of 1964, Section 504 of the Rehabilitation Act of 1973, Title I1 of the 

Americans with Disabilities Action of 1990, the Age Discrimination Act of 1975, 

and Title IX of the Education Amendments of 1972. If you believe you have been 

discriminated against in any program, activity, or facility, or if you desire further 

information, please write to: EVOS Trustee Council, 441 West 5~ Avenue, Suite 

500, Anchorage, Alaska 99501-2340; or O.E.O. U.S. Department of the Interior, 

Washington, D.C. 20240. 
EXXON VALDE4 

Response of Seabirds to 

Fluctuations in Forage Fish Density 

. -... ... . . . - - . - - 

EVOSTC Restoration Project 01 163M 

OCS Study MMS 2002-068 
Response of Seabirds to Fluctuations in Forage Fish Density 

Principal Investigator 

& Final Report Editor: 

John F. ~iatt' 

Project Leaders & Report Contributors: 

Alisa A. booki ire'.^, Gary S. ~rew', Ann M. ~ardin~'.', Arthur B. ~ettle~, Alexander S. 

~ita~sk~', Michael A. ~itzow'~~, April ~ielsen', John F. ~iatt', Martin D. ~obards',', 

Michael shultzl, Suzann G. speckmans, Thomas I. Van Stephani ad or' 

l~laska Science Center, U.S. Geological Survey, 

10 1 1 East Tudor Rd., Anchorage, AK 99503 

Kodiak Marine Laboratory, National Marine Fisheries Service, 

30 1 Research Court, Kodiak AK 996 15 

'~ept. of Biological Sciences, University of Durham, 

South Road, Durham DHl 3LE UK 

4~laska Maritime National Wildlife Refuge, U.S. Fish and Wildlife Service, 

2355 Kachemak Bay Drive, Homer, AK 99603 

'~epartment of Zoology, Box 351 800, University of Washington, 

Seattle, WA 981 95 

6~nstitute of Marine Sciences, University of California, 

Santa Cruz, CA 95064 

'~isheries and Marine Institute, Memorial University of Newfoundland, 

St. John's, NF Canada A1 C 5R3 

8~chool of Aquatic and Fishery Sciences, University of Washington, 

1122 NE Boat St., Seattle, WA 98105 

Division of Environmental and Evolutionary Biology, Graham Kerr Building, 

University of Glasgow, Glasgow G12 8QQ Scotland 
Response of Seabirds to Fluctuations in Forage Fish Density 

Restoration Project 0 1 163M 

MMS Alaska Region OCS Study MMS 2002-068 

Final Report 

Studv Historv: Since the late 1970s, seabirds in the Gulf of Alaska (GOA) have shown 

signs of food stress: population declines, decreased productivity, changes in diet, and 

large-scale die-offs. Small-mesh fishing trawls conducted during the past 45 years reveal 

that a major shift in fish community composition occurred in the late 1970s: some forage 

species (e.g., capelin) virtually disappeared, while predatory fish (e.g., pollock) 

populations increased markedly. These ecosystem changes were part of an overall 

"regime shift" in the physical and biological environment of the GOA and had profound 

effects on seabirds. The Ejcwon Valdez Oil Spill (EVOS) occurred more than ten years 

after the regime shift, and it has been difficult to distinguish EVOS effects from effects of 

the regime shift on seabird populations. Restoration Project 01 163M was initiated as part 

of the Apex Predator Ecosystem Experiment (APEX) in 1995 to characterize 

relationships between seabird population dynamics, foraging behavior, and forage fish 

densities in lower Cook Inlet-- the area in which most seabirds were killed by the EVOS. 

The ultimate goal was to achieve a better understanding of relationships between seabirds 

and forage fish in a variable environment, and to assess whether current environmental 

conditions are favorable to seabirds in the GOA. The Cook Inlet Seabird and Forage Fish 

Study (CISeaFFS) is a collaborative project of the Alaska Biological Science Center and 

the Alaska Maritime National Wildlife Rehge (hnded separately under Project 001635, 

Barren Islands Seabird Studies), with major hnding and logistic support from the EVOS 

Trustees (APEX), the U.S. Geological Survey, the Minerals Management Service, U.S. 

Fish and Wildlife Service, Alaska Department of Fish and Game, and the University of 

Washington. 

Abstract: Following the Ejcwon Valdez Oil Spill (EVOS), one concern was that prevailing 

ecological conditions in the Gulf of Alaska (GOA) would not favor recovery of damaged 

seabird populations. To address this issue, we examined relationships between 

oceanography, forage fish and seabirds near three seabird colonies in lower Cook Inlet 

(LCI) in 1995-1999 (some colony work continued until 2001). Upwelling of cold, 

nutrient-rich GOA waters at the entrance to the shallow LC1 estuary supports a high 

density of juvenile pollock, sand lance, and capelin; which in turn are exploited by high 

densities of breeding seabirds (murres, kittiwakes, puffins, etc.) on the east side of LCI. 

Waters on the west side of LC1 are oceanographically distinct (warmer, less saline, 

outflowing), and much less productive for forage fish and seabirds. Patterns of seabird 

foraging behavior, productivity and population change reflected patterns of forage fish 

abundance and distribution, which in turn depended on local oceanography. Most seabird 

parameters varied with forage fish density in a non-linear (e.g., sigrnoidal, exponential) 

fashion, and in some areas and years, productivity was limited by food availability. 
Current and projected ecological conditions favor recovery of seabirds from the EVOS 

at some colonies. In 14 chapters, this report summarizes data and compiles it into 247 

tables, figures and appendices. Chapter 14 provides a thorough synthesis of overall 

project findings. Final analyses and interpretations of data will be published later in 

peer-reviewed journals (in addition to 61 articles already completed). 

Key Words: Cook Inlet, murre, kittiwake, guillemot, forage fish, diet, pollock, capelin, 

sandlance, reproduction, growth rate, hydroacoustic, trawl, seine, Exxon Valdez, 

Kachemak Bay. 

Proiect Data: Description and format of data - Data vary in type and format. 

Oceanographic data (thermographs, CTD) in .hex and .csv files, hydroacoustic data in 

raw .dt4 files and .csv integration summary files, fish and bird data archived in Excel 

and Access databases. Satellite imagery and maps archived in .wmf format or ArcView 

shape files. Custodian - Contact John Piatt, USGS, 101 1 E. Tudor Rd., Anchorage, AK 

99503; ph: 907 786-3549. For Barren Islands colony data contact Vernon Byrd, 

USFWS, 2355 Kachemak Bay Dr., Homer, AK 99603; ph: 907 235-6546. 

Report Citation: 

Piatt, J.F., editor. 2002. Response of seabirds to fluctuations in forage fish density, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 01 163M), 

and Minerals Management Service (Alaska OCS Study MMS 2002-068), Alaska 

Science Center, U.S. Geological Survey, Anchorage, Alaska. 

Chapter Citation: 

Drew, G.S. 2002. Primary and secondary production in lower Cook Inlet. Pages 27-32 

in J.F. Piatt, editor. Response of seabirds to fluctuations in forage fish density, Exxon 

Valdez Oil Spill Restoration Project Final Report (Restoration Project 01 163M) and 

Minerals Management Service (Alaska OCS Study MMS 2002-068). Alaska Science 

Center, U.S. Geological Survey, Anchorage, Alaska. 

Disclaimer: 

The opinion, findings, conclusions, or recommendations expressed in this report are 

those of the authors and do not necessarily reflect the views of the Minerals 

Management Service or the Exxon Valdez Oil Spill Trustee Council, nor does mention 

of products constitute endorsement or recommendations for use by the Federal 

Government. 
Table of Contents 

Chapter Title 

Introduction and Project Overview 

Oceanography of lower Cook Inlet 

Primary and Secondary Production in lower Cook Inlet 

Abundance and Distribution of Pelagic Forage Fish in 

Cook Inlet 

Abundance and Distribution of Nearshore Fish in lower 

Cook Inlet 

Benthic and Intertidal Fishes in Kachemak Bay 

Hydroacoustic Forage Fish Biomass and Distribution in 

Cook Inlet 

Pelagic Seabird Abundance and Distribution in lower 

Cook Inlet 

Common Murre Biology in lower Cook Inlet 

Black-legged Kittiwake Biology in lower Cook Inlet 

Pigeon Guillemot Biology in Kachemak Bay 

Homed Puffin Biology on Duck Island 

Biology of Other Seabird Species in lower Cook Inlet 

Response of Seabirds to Fluctuations in Forage Fish 

Density: Can Seabirds Recover fiom Effects of the Exron 

Valdez oil spill? 

Page 

1-17 

18-26 

27-32 

33-39 

Tables, Figures and Appendices 
Note: Tables are individually numbered, provided in sequence, and grouped aper the 

main body of text, and therefore page numbers are not provided 

Table 1.1. Characteristics and measurement of seabird numerical and functional response 

parameters. 

Table 4.1. Mean catch-per-unit-effort (CPUE and standard error) of all fishes, and major 

fish species, captured per mid-water trawl (n=159) near the Barren Islands, 

Kachemak Bay and Chisik Island in 1996-1999. 

Table 4.2. Species composition of mid-water trawl catches at the Barren Islands, 

Kachemak Bay, and near Chisik Island, 1996- 1999. Species that comprised at 

least 1% of the catch are listed. 

Table 5.1. Sampling time periods and number of beach seine sets conducted at the 

Barren Islands, Chisik Island and Kachemak Bay during 1995-1999. 

Table 5.2. Numbers of fish collected for morphometric measurements. 

Table 5.3. Total beach seine catches at the Barren Islands, Chisik Island and Kachemak 

Bay during June - August, 1995-1999. 

Table 5.4. Beach seine catch composition by actual numbers (A) and by proportions (B) 

of major taxonomic groups at the Barren Islands, Chisik Island, and Kachemak 

Bay, during June-Aug, 1995- 1999. 

Table 5.5. Catch-per-unit-effort (CPUE), standard error, and median catches in beach 

seine sets during June-August, 1995-1999, at the Barren Islands, Chisik Island 

and Kachemak Bay. 

Table 5.6. Frequency of occurrence of different fish species in beach seines at the Barren 

Islands, Chisik Island, and Kachemak Bay, June-August, 1995- 1999. 

Table 6.1. Relative abundance of demersal fishes captured in bottom trawls in Outer and 

Inner Kachemak Bay, 1996- 1999. 

Table 6.2. Seasonal variation in relative abundance of demersal fishes captured in 

Kachemak Bay, 1996-1999. Data from all stations in Kachemak Bay are 

combined. 

Table 6.3. Species composition (% total number) of demersal fishes in bottom trawls, 

1996- 1999, and SCUBA transects, 1997- 1998, in Kachemak Bay. 
Table 6.4. Demersal fish abundance on SCUBA transects in Outer and Inner Kachemak 

Bay, 1997- 1998. 

Table 6.5. All fishes and hermit crabs counted on good SCUBA transects in 1999. 

Table 7.1. Total number of linear kilometers surveyed in Lower Cook Inlet during 

hydroacoustic surveys, 1 995- 1 999. 

Table 7.2. Number of ten-minute transects used for analysis of hydroacoustic surveys in 

Cook Inlet. 

Table 7.3. Hydroacoustic biomass (g/m3) of forage fish in waters near Chisik, Gull and 

Barren islands, 1995-1 999. 

Table 7.4. Hydroacoustic biomass (g/m3) of forage fish in surface (<30m) waters near 

Chisik, Gull and Barren islands, 1995- 1999. 

Table 7.5. Hydroacoustic biomass (g/m3) of forage fish in inshore transect waters near 

Chisik, Gull and Barren islands, 1995-1 999. 

Table 7.6. Hydroacoustic biomass (g/m3) of forage fish in offshore transect waters near 

Chisik, Gull and Barren islands, 1995-1999. 

Table 8.1. Total number of linear and square kilometers surveyed in Lower Cook Inlet 

during 5 years of surveys for marine birds and mammals, 1995-1 999. 

Table 8.2. Species composition and numbers of seabirds and marine mammals observed 

during 5 years of surveys in Lower Cook Inlet during July and August, 1995- 

1999. 

Table 8.3. Number observed (N) and density (D) per kilometer squared of predominant 

marine bird species and species groups by study area in Lower Cook Inlet, 1995- 

1999. 

Table 9.1. Numbers of Common Murres in population plots at Chisik Island (includes 

Duck Island), 1995 - 1999. 

Table 9.2. Numbers of Common Murres in population plots at Gull Island, 1995- 1999. 

Table 9.3. Numbers of Common Murres in population plots at the Barren Islands, 1995- 

1999. 

Table 9.4. Common Murre hatching success (chicks hatched per egg laid) at Chisik, Gull 

and Barren islands, 1995- 1999. 
Table 9.5. Common Murre fledging success (chicks fledged per chick hatched) at Chisik, 

Gull and Barren islands, 1995- 1999. 

Table 9.6. Common Murre breeding success (chicks fledged per egg laid) at Chisik, Gull 

and Barren islands, 1995- 1999. 

Table 9.7. Timing of Common Murre egg laying at Chisik, Gull and Barren Islands, 

1995- 1999. 

Table 9.8. Timing of Common Murre hatching at Chisik, Gull and Barren Islands, 1995- 

1999. 

Table 9.9. Summary of Common Murre chick diet composition (% number) at Chisik, 

Gull and Barren islands, 1995- 1999. 

Table 9.10. Summary of adult Common Murre diet composition (% mass) at Chisik, 

Gull and Barren islands, 1995- 1999. 

Table 9.1 1. Common Murre attendance expressed as "bird-minutes" or the combined 

minutes both parents spent at the nest site per hour during incubation at Chisik, 

Gull, and Barren Islands, 1995- 1999. 

Table 9.12. Common Murre attendance expressed as "bird-minutes" or the combined 

minutes both parents spent at the nest site per hour during chick-rearing at Chisik, 

Gull, and Barren Islands, 1995- 1999. 

Table 9.13. Common Murre chick-feeding rates (feeds per hour) at Chisik, Gull, and 

Barren Islands, 1995-1 999. 

Table 9.14. Common Murre foraging trip durations (minutes) when chick provisioning 

(resulted in chick feeding) at Chisik, Gull, and Barren Islands, 1995-1999. 

Table 9.15. Pooled growth rate (g Imm wing growth) of Common Murre chicks at Chisik 

and Gull Islands, 1995- 1999. 

Table 9.16. Size, condition, and estimated age of Common Murre fledglings at Chisik 

Island, 1997- 1999, summarized by capture bout date. 

Table 9.17. Size, condition, and estimated age of Common Murre fledglings at Gull 

Island, 1997- 1999, summarized by capture bout date. 

Table 9.18. Size and condition of Common Murre fledglings at the Barren Islands 1996 - 

1999, summarized by capture bout date. 
Table 9.19. Common Murre fledging age (days) at Chisik and Gull Islands, 1995-1999 

(n = fledglings). 

Table 9.20. Common Murre adult size and condition, Chisik Island 1997-1999, 

summarized by capture bout date. 

Table 9.2 1. Common Murre adult size and condition, Gull Island 1997- 1999, 

summarized by capture bout date. 

Table 9.22. Baseline concentrations of corticosterone in Common Murres at Gull and 

Chisik islands, 1997-1999 

Table 10.1. Number of adult Black-legged Kittiwakes counted in plots from middle 

incubation to the start of fledging at Chisik (plots 1 -7), Gull (plots 1-1 0) and 

Barren islands (plots 1 -4), 1995- 1999. 

Table 10.2. Black-legged Kittiwake productivity (chicks fledged per nest site) at Chisik, 

Gull and Barren islands, 1995-1999. 

Table 10.3. Black-legged Kittiwake laying success (number of nest structures with >=1 

egg, per nest structure) at Chisik, Gull and Barren islands, 1995-1999. 

Table 10.4. Black-legged Kittwake clutch size (eggs laid per nest with eggs) at Chisik, 

Gull and Barren islands, 1995- 1999. 

Table 10.5. Black-legged Kittiwake hatching success (chicks hatched per egg laid) at 

Chisik, Gull and Barren islands, 1995-1999. 

Table 10.6. Black-legged Kittwake brood size at hatching (chicks hatched per nest with 

chicks) at Chisik, Gull and Barren islands, 1995-1999. 

Table 10.7. Black-legged Kittiwake fledging success (chicks fledged per chick hatched) 

at Chisik, Gull and Barren islands, 1995-1999. 

Table 10.8. Black-legged Kittiwake clutch size (eggs laid per nest with eggs) at Chisik, 

Gull and Barren islands, 1995-1 999. 

Table 10.9. Black-legged Kittiwake egg laying chronology at Chisik, Gull and Barren 

islands, 1995-1999. 

Table 10.10. Black-legged Kittiwake chick hatching chronology at Chisik, Gull and 

Barren islands, 1995- 1999. 

Table 10.1 1. Black-legged Kittiwake productivity index at Gull and Chisik Islands, 

1995- 1999. 
Table 10.12. Black-legged Kittiwake attendance expressed as "bird-minutes" or the 

combined minutes both parents spent at the nest site per hour during chick-rearing 

at Chisik, Gull and Barren islands, 1995-1999. 

Table 10.13. Black-legged Kittwake chick-feeding rates (feeds per hour) at Chisik, Gull 

and Barren islands, 1995-1 999. 

Table 10.14. Black-legged Kittiwake foraging trip durations (minutes) when chick 

provisioning resulted in chick feeding at Chisik, Gull and Barren islands, 1995- 

1999. 

Table 10.15. Growth rates (gld) of Black-legged Kittiwake chicks by rank at Gull and 

the Barren islands, 1995-1999. 

Table 10.16. Baseline concentrations of corticosterone in Black-legged Kittwakes at 

Gull and Chisik islands, 1997- 1999. 

Table 10.17. Summary of Black-legged Kittiwake chick diet composition (% mass) at 

Chisik, and Gull islands, 1995-1999. 

Table 10.18. Average feeding frequency, meal size, energy density, and energy 

provisioning rates to Black-legged Kittiwake broods at Gull, Chisik, and Barren 

islands, Cook Inlet, Alaska 1995 - 1999. 

Table 10.19. Summary of adult Black-legged Kittwake diet composition (% mass) at 

Chisik, Gull and Barren islands, 1995-1999. 

Table 10.20. Black-legged Kittiwake adult size and condition, Chisik Island 1997-1999, 

summarized by capture bout date. 

Table 10.2 1. Black-legged Kittiwake adult size and condition, Gull Island 1997-1 999, 

summarized by capture bout date. 

Table 10.22. Black-legged Kittiwake adult mass, Barren Islands 1997-1999, summarized 

by capture bout date. 

Table 11.1. Duration of counts made at Pigeon Guillemot colony sites in Kachemak Bay. 

Table 11.2. Age - wing length data used to age unknown-age Pigeon Guillemot chicks. 

Table 11.3. Results of replicated counts at individual Pigeon Guillemot colony sites in 

Kachemak Bay, 1996- 1999. 
Table 1 1.4. Results of replicated counts of Pigeon Guillemots at different areas of 

Kachemak Bay, 1996- 1999. 

Table 1 1.5. Results of annual surveys of Pigeon Guillemots along the south shore of 

Kachemak Bay, 1995- 1999. 

Table 1 1.6. Median hatch date of Pigeon Guillemot eggs in Kachemak Bay, 1995-1 999. 

Table 1 1.7. Percent composition (by number) of prey items in Pigeon Guillemot nestling 

diets at Kachemak Bay, Alaska, 1995- 1999. 

Table 11.8. Growth parameters of alpha and singleton Pigeon Guillemot chicks in 

Kachemak Bay, 1995-1 999. 

Table 1 1.9. Growth parameters of beta Pigeon Guillemot chicks in Kachemak Bay, 

1995- 1999. 

Table 1 1.10. Mayfield parameters and estimates of reproductive success for Pigeon 

Guillemots in Kachemak Bay, 1995- 1999. 

Table 1 1.1 1. Fledging age of Pigeon Guillemot chicks in Kachemak Bay, 1996-1998. 

Table 1 1.12. Age-dependant observed mortality rate of Pigeon Guillemot chicks in 

Kachemak Bay, 1995-1 999. 

Table 11.1 3. Measurements of adult Pigeon Guillemots in Kachemak Bay, 1995-1999. 

Table 12.1. Horned Puffin breeding success on Duck (Chisik) Island. 

Table 12.2. Diet composition (% number) of Horned Puffin chicks at Duck (Chisik) 

Island in 1995- 1999. 

Table 12.3. Mean size and energy value of sandlance in Horned Puffin chick diet. 

Table 12.4. Characteristics of meal loads delivered by Horned Puffins to their chicks. 

Table 12.5. Horned Puffin daily food delivery rates at Duck Island 

Table 12.6. Linear growth rates of Horned Puffin chicks on Duck Island in different 

years. 

Table 12.7. Horned Puffin chick fledging age on Duck Island. Fledging age (+/- 3 days) 

is calculated from productivity and growth data of known age chicks. 

Table 12.8. Measurements of Horned Puffin fledglings caught en route to the ocean. All 

measurements in mm except mass, which is in grams. 
Table 12.9. Census counts of Horned Puffins on Duck Island. 

Table 12.10. Whole island census counts of Tufted Puffin on Duck Island. 

Table 13.1. Glaucous-winged Gull productivity and hatching chronology at Chisik and 

Gull Islands, 1995-1999. 

Table 13.2. Number of adult Glaucous-winged Gulls counted in plots from middle 

incubation to the start of fledging at Chisik (plots 1-7) and Gull Islands (plots 1- 

lo), 1995-1999. 

Table 13.3. Total numbers of individual Glaucous-winged Gulls seen at Chisik and Gull 

Islands 1995-1999. 

Table 13.4. Pelagic Cormorant productivity and hatching chronology at Gull Island, 

1995-1 999. 

Table 13.5. Pelagic and Red-faced Cormorant productivity index on Gull Island 1995- 

1999. 

Table 13.6. Numbers of Pelagic Cormorant individuals and nests in population plots on 

Gull Island 1995-1999. 

Table 13.7. Numbers of Tufted Puffins in population plots at Gull Island 1997- 1999. 

Table 13.8. Tufted Puffin chick growth rates at Gull Island 1997 for five individual 

chicks. 

Table 14.1. Ranked variability in seabird parameters among years (expressed as "mlm 

Ratio", the ratio of maximum to minimum values, and as C.V., the Coefficient of 

Variation) and functional relationship with prey density. 

Table 14.2. Variability in breeding success of Black-legged Kittiwakes and Common 

Murres in different geographic areas. 

Table 14.3. Preliminary estimate of population parameters for seabirds at Chisik and 

Gull Islands. 
List of Figures: 

Note: Figures are individually numbered, provided in sequence, and grouped ajier the 

main body of text and tables, and therefore page numbers are not provided 

Figure 2.1. Location of the Cook Inlet study area in south-central Alaska. 

Figure 2.2. Bathymetric map of the greater Cook Inlet area. 

Figure 2.3. Currents in Cook Inlet overlayed upon bathymetry. 

Figure 2.4. Locations of CTD transects and long term monitoring stations in Cook Inlet 

Figure 2.5. NOAA 12 AVHRR Channel 4 sea surface temperature for Cook Inlet, July 

22, 1995. 

Figure 2.6. NOAA 12 AVHRR Channel 4 sea surface temperature for Cook Inlet, July 

16, 1996. 

Figure 2.7. NOAA 12 AVHRR Channel 4 sea surface temperature for Cook Inlet, July 

27, 1997. 

Figure 2.8. NOAA 12 AVHRR Channel 4 sea surface temperature for Cook Inlet, July 

14, 1998. 

Figure 2.9. NOAA 12 AVHRR Channel 4 sea surface temperature for Cook Inlet, July 3, 

1999. 

Figure 2.10. All CTD casts conducted in Cook Inlet during 1995-1999. 

Figure 2.1 1. Comparison of vertical temperature profiles on three different transects of 

Cook Inlet in 1996. 

Figure 2.12. Comparison of vertical salinity profiles on three different transects of Cook 

Inlet in 1996. 

Figure 2.13. Inter-annual variation in vertical temperature profiles of Kennedy Entrance 

in lower Cook Inlet (Transect C). 

Figure 2.14. Inter-annual variation in vertical salinity profiles of Kennedy Entrance in 

lower Cook Inlet (Transect C). 

Figure 2.1 5. Seasonal development of thermal stratification at the Eldred Passage station 

in Kachemak Bay, during 1997 to 1999. 

. . . Xlll 
Figure 2.16. Seasonal variability in surface and bottom temperatures near Hesketh 

Island, Kachemak Bay, during 1997 to 1999. 

Figure 2.17. Seasonal variability in sea surface temperatures at the three study sites 

during 1995 to 1999. 

Figure 2.18. Continuously recorded fluctuations in sea surface temperature at Seldovia 

Harbor, Kachemak Bay, from June 1994 to December 2000. 

Figure 2.19. Temperature anomalies in the Gulf of Alaska and Cook Inlet, 197 1 - 1999. 

Figure 3.1. Locations of transects (red lines) and monitoring stations (red dots) where 

phytoplankton biomass was measured in Cook Inlet, 1997- 1999. 

Figure 3.2. Fluorometer measurements of chlorophyll concentrations on vertical profiles 

of transects A, B and C in Cook Inlet (see Fig. 3.1). 

Figure 3.3. Fluorometer measurements of chlorophyll concentrations on vertical profiles 

of transect B (see Fig. 3.1), collected during the summers of 1997, 1998, and 

1999. 

Figure 3.4. Nutrient and chlorophyll concentrations across transect B in 1997. 

Figure 3.5. Seasonal fluctuations in phytoplankton concentrations at Inner Bay and 

Eldred Passage monitoring sites in Kachemak Bay. Fluorometry profiles were 

collected throughout the summers of 1998 and 1999. 

Figure 3.6. Seasonal variability in nutrient concentrations at 5, lO,25, and 50 meter 

depths at the Eldred Passage monitoring station. Data collected from April 15 to 

August 15, 1997. 

Figure 3.7. Zooplankton biomass (settled volume) in samples collected in Cook Inlet at 

mid-water trawl stations, along CTD transects, and at monitoring stations in 

Kachemak Bay, during 1997- 1999. 

Figure 3.8. Zooplankton biomass (settled volume) on transect B across lower Cook Inlet 

in 1997- 1999. 

Figure 3.9. Seasonal variation in zooplankton biomass (settled volume) at the Inner Bay 

and Eldred Passage monitoring sites in Kachemak Bay, 1997- 1999. 

Figure 4.1. Stations sampled with mid-water trawl in lower Cook Inlet, 1996-1999. 

Shown are locations of "good tows" used in calculations of CPUE, and additional 

"poor tows" used for mapping distribution of species (Figs. 4.6-4.9). 
Figure 4.2. Mean catch-per-unit-effort (+ standard error) for all fishes captured from 

1996 to 1999 at the Barren Islands, Kachemak Bay and near Chisik Island. 

Figure 4.3. Species composition (% total numbers) of mid-water trawl catches near the 

Barren Islands, Kachemak Bay and Chisik Island in 1996-1 999. The bottom graph 

shows the species composition in each area for all years combined 

Figure 4.4. Length frequency histograms for the most common fish species caught in 

mid-water trawls in Cook Inlet, 1996-1999. Data are combined from all years and 

areas. 

Figure 4.5. Depths at which sand lance, herring, gadids and osmerids were caught in 

mid-water trawls in Cook Inlet. Data were binned into 5 m depth intervals, and 

plotted as mean CPUE (+ standard error). 

Figure 4.6. Geographic distribution of mid-water trawl catches of all species, sand lance, 

herring, pollock, and capelin in lower Cook Inlet, 1996-1999 (CPUE, fish per km 

trawled, data combined for all years). 

Figure 4.7. Geographic distribution of mid-water trawl catches of prickleback, cod, pink 

salmon, longfin smelt, and Pacific sandfish in lower Cook Inlet, 1996- 1999 

(CPUE, fish per km trawled, data combined for all years). 

Figure 4.8. Geographic distribution of mid-water trawl catches of king salmon, eulachon, 

red salmon, prowfish, and Pacific lamprey in lower Cook Inlet, 1996-1999 

(CPUE, fish per km trawled, data combined for all years). 

Figure 4.9. Geographic distribution of mid-water trawl catches of euphausiid, shrimp, 

jellyfish and squid in lower Cook Inlet, 1996-1999 (CPUE, fish per km trawled, 

data combined for all years). 

Figure 5.1. Mean (columns), standard error (error bars), and median (dots) seine catches 

at Chisik Island, Kachemak Bay, and the Barren Islands. 

Figure 5.2. Shannon-Wiener index of diversity and species richness for Chisik Island, 

Kachemak Bay, and the Barren Islands. 

Figure 5.3. Species composition of beach seine catches at Chisik Island, Kachemak Bay 

and the Barren Islands, 1995-1999. 

Figure 6.1. Stations sampled by bottom trawl and SCUBA in Kachemak Bay, 1996- 

1999. 

Figure. 7.1. Routes for hydroacoustic surveys of fish and seabird censuses conducted in 

lower Cook Inlet during August, 1995. Triangles indicate location of seabird 

colonies. 
Figure 7.2. Routes for hydroacoustic surveys of fish and seabird censuses conducted in 

lower Cook Inlet during late July, 1996. Triangles indicate location of seabird 

colonies. Zig-zag lines near shore are coastal transects added in 1996. 

Figure 7.3. Routes for hydroacoustic surveys of fish and seabird censuses conducted in 

lower Cook Inlet during July-August, 1997- 1999. Triangles indicate location of 

seabird colonies. Zig-zag lines near shore are coastal transects added in 1996. 

Figure 7.4. Fish density in all waters and in waters <30 m deep near Chisik, Gull and 

Barren islands, 1995- 1999. 

Figure 7.5. Fish density in inshore and offshore waters near Chisik, Gull and Barren 

islands, 1995- 1999. 

Figure 7.6. Fish density by 20 m depth strata near Chisik, Gull and Barren islands, 1995- 

1999. 

Figure 7.7. Frequency of occurrence of different densities of fish in 10-min by 5 m 

blocks near Chisik, Gull and Barren islands, 1995-1 999. 

Figure 7.8. Distribution of acoustic backscattering signals in lower Cook Inlet, 6-30 m 

strata. 

Figure 7.9. Distribution of acoustic backscattering signals in lower Cook Inlet, 3 1 -60m 

strata. 

Figure 7.10. Distribution of acoustic backscattering signals in lower Cook Inlet, 6 1 - 100 

m strata. 

Figure 7.1 1. Distribution of acoustic backscattering signals in lower Cook Inlet, all 

strata. 

Figure 8.1. Distribution and abundance of Common Murres in lower Cook Inlet, 1995- 

1999. 

Figure 8.2. Distribution and abundance of Black-legged Kittiwakes in lower Cook Inlet, 

1995-1999. 

Figure 8.3. Distribution and abundance of Pigeon Guillemots in lower Cook Inlet, 1995- 

1999. 

Figure 8.4. Distribution and abundance of Horned Puffins in lower Cook Inlet, 1995- 

1999. 
Figure 8.5. Distribution and abundance of Tufted Puffins in lower Cook Inlet, 1995- 

1999. 

Figure 8.6. Distribution and abundance of Cormorants (spp.) in lower Cook Inlet, 1995- 

1999. 

Figure 8.7. Distribution and abundance of Glaucous-winged Gulls in lower Cook Inlet, 

1995-1 999. 

Figure 8.8. Distribution and abundance of Marbled and Brachyramphus Murrelets in 

lower Cook Inlet, 1995-1999. 

Figure 8.9. Distribution and abundance of Kittlitz's Murrelet in lower Cook Inlet, 1995- 

1999. 

Figure 8.10. Distribution and abundance of various fish-eating or diving seabirds in 

lower Cook Inlet, 1996. 

Figure 8.1 1. Distribution and abundance of various plankton- or surface-feeding seabirds 

in lower Cook Inlet, 1996. 

Figure 1 1.1. Pigeon Guillemot colonies studied during 1995- 1999 in Kachemak Bay. 

Figure 11.2. Pigeon guillemot colony census sites in western Kachemak Bay. 

Figure 1 1.3. Pigeon guillemot colony census sites in eastern Kachemak Bay. 

Figure 12.1. Linear regression of Homed Puffin chick age on wing length (n=67 

chicks). 

Figure 12.2. Homed Puffin bill measurements. A=cutting edge, B=bill depth, C=culmen, 

D=bill width. 

Figure 12.3. Homed Puffin chick diet composition (% number of all prey items (n=2658) 

collected in 1995-1 999). 

Figure 12.4. Seasonal colony attendance of Homed Puffins at Duck Island. 

Figure 12.5. Diurnal attendance patterns of Homed Puffins in North Cove, Chisik. 

Average attendance on 8,9 and 10 July, 1997. 

Figure 14.1. Summary of fish abundance indices (acoustic biomass, trawl CPUE, seine 

CPUE) observed around Chisik, Gull and Barren islands, Cook Inlet, during 

1 995- 1999. 
Figure 14.2. Summary of Common Murre breeding and behavioral parameter values 

observed at Chisik, Gull and Barren islands, Cook Inlet, during 1995-1999. 

Figure 14.3. Summary of Black-legged Kittiwake breeding and behavioral parameter 

values observed at Chisik, Gull and Barren islands, Cook Inlet, during 1995-1999. 

Figure 14.4. Functional response of Common Murre breeding and behavioral parameters 

to variation in food supply. 

Figure 14.5. Functional response of Black-legged Kittiwake breeding and behavioral 

parameters to variation in food supply. 

Figure 14.6. Frequency of different levels of breeding success for Common Murres and 

Black-legged Kittiwakes in Alaska. 

Figure 14.7. Variability in breeding success versus breeding success in Common Murres 

and Black-legged Kittiwakes around the world. 

Figure 14.8. Ranked variability (Coefficient of Variation) in breeding and behavioral 

parameters for Common Murres and Black-legged Kittiwakes among colonyyears in Cook Inlet. 

Figure 14.9. Population trends for populations of Common Murres and Black-legged 

Kittiwakes at Chisik, Gull and Barren islands. 

Figure 14.10. Historical productivity of Black-legged Kittiwakes at Chisik, Gull and 

Barren islands, 1970- 1999. 

Figure 14.1 1. Normalized deviations from average of seabird breeding and behavioral 

parameters at Chisik, Gull and Barren islands, 1995-1999. Deviations have been 

arbitrarily ranked by magnitude from most positive (left) to most negative (right). 

Figure 14.12. Average parameter index versus population trend for Common Murres 

(COMU) and Black-legged Kittiwakes (BLKI) at Chisik, Gull and Barren islands. 

Figure 14.13. Historical breeding success (bs) of Black-legged Kittiwakes in the Gulf of 

Alaska (GOA) and Bering Sea (BS), categorized by functional relationships with 

food supply as "Deprived" (bs<0.015 chickslpair), "Limited" (0.0 15<bs<0.46 

chickdpair), and "Unlimited" (bs>0.46 chickdpair). 
List of Appendices: 

Note: Appendices are individually numbered, provided in sequence, and grouped afrer 

the main body of text, tables, andfigures, and therefore page numbers are not 

provided 

Appendices 2.1-2.2 1. Vertical CTD profiles from transects A, B, C in Cook Inlet and 

three fixed stations in Kachemak Bay, 1995-1999. Profiles include temperature, 

salinity, and density at all sites. Turbidity and chlorophyll concentration are also 

reported on transects or stations where sensors for these parameters were attached 

to the CTD in 1997-1999. 

Appendix 2.22. Temperature-logger deployment and recovery information for lower 

Cook Inlet 1995- 1999. 

Appendix 4.1. Station information for all mid-water trawls in Cook Inlet, 1996- 1999. 

Appendix 4.2. Catch-per-mid-water trawl near the Barren Islands, 1996- 1999. 

Appendix 4.3. Catch-per-mid-water trawl in Kachrnak Bay, 1996-1 999. 

Appendix 4.4. Catch-per-mid-water trawl near Chisik Island, 1996- 1999. 

Appendix 4.5. Non-fish species captured in each mid-water trawl, 1997-1999. 

Appendix 4.6. Length-weight regressions for seven forage species that comprised at least 

5% of species catch composition in one aredyear. Data are combined for all 

years and areas. 

Appendix 6.1. Station information for bottom trawls in Kachemak Bay, 1996- 1999. 

Appendix 6.2. All species captured in "good" bottom trawls in Kachemak Bay, 1996- 

1999. Mean and standard deviation of CPUE are given for each year. 

Appendix 6.3. SCUBA station information in Kachemak Bay, 1997- 1999. Areas include 

Seldovia (SE), Moosehead (MH), and Cohen. 

Appendix 6.4. All fishes and hermit crabs recorded on "good" SCLBA dives in 

Kachemak Bay, 1997- 1998. Mean CPUE and standard deviation are listed for 

each year. 

Appendix 9.1. Common Murre population plot count windows between mid-incubation 

(MI) and the start of fledging (SOF). 

Appendix 9.2. Rules used for analysis of Common Murre productivity data. 
Appendix 9.3. Information included on forms for collection and analysis of Common 

Murre productivity and nesting chronology data. 

Appendix 9.4. Common Murre chick meals by number (N) and percent composition (YO) 

at Chisik Island, 1995-1999. 

Appendix 9.5. Common Murre chick meals by number (N) and percent composition (YO) 

at Gull Island, 1995-1999. 

Appendix 9.6. Common Murre chick meals by number (N) and percent composition (YO) 

at the Barren Islands, 1995-1999. 

Appendix 9.7. Prey items in adult common murre stomachs collected at Chisik Island, 

lower Cook Inlet during 1995 - 1999. 

Appendix 9.8. Prey items in adult common murre stomachs collected at Gull Island, 

lower Cook Inlet during 1995 - 1999. 

Appendix 9.9. Prey items in adult common murre stomachs collected at the Barren 

Islands, lower Cook Inlet during 1995 - 1999. 

Appendix 9.10. Summary of Common Murre population plot counts for lower Cook 

Inlet. 

Appendix 9.11. Summary of Common Murre colony population estimates for lower 

Cook Inlet. 

Appendix 10.1. Black-legged Kittiwake calculated population plot count windows, 

defined as the period between mid-incubation (MI) and the start of fledging 

(SOF) and the actual range of count dates used at Chisik and Gull Islands, 1995- 

1999. 

Appendix 10.2. Summary of Black-legged Kittwake population plot counts at breeding 

colonies in Lower Cook Inlet. Counts are the mean of all count-days for a season. 

Appendix 10.3. Summary of Black-legged Kittiwake whole-colony counts in lower 

Cook Inlet. 

Appendix 10.4. Summary of Black-legged Kittiwake productivity and productivity 

indexes at Chisik, Gull and Barren Islands, lower Cook Inlet, Alaska. 

Appendix 10.5. Prey items in Black-legged Kittiwake regurgitations (chick meals) 

collected at the Barren Islands, lower Cook Inlet, during 1995-1999. 
Appendix 10.6. Prey items in Black-legged Kittiwake regurgitations (chick meals) 

collected at Gull Island, lower Cook Inlet, during 1995- 1999. 

Appendix 10.7. Prey items in Black-legged Kittiwake regurgitations (chick meals) 

collected at Chisik Island, lower Cook Inlet, during 1995- 1999. 

Appendix 10.8. Prey items in adult Black-legged Kittiwake stomachs collected at the 

Barren Islands, lower Cook Inlet during 1995-1 999. 

Appendix 10.9. Prey items in adult Black-legged Kittiwake stomachs collected at Gull 

Island, lower Cook Inlet during 1995 - 1999. 

Appendix 10.10. Prey items in adult Black-legged Kittiwake stomachs collected at 

Chisik Island, lower Cook Inlet during 1995 - 1999. 

Appendix 1 1 .l. Boundaries of Pigeon Guillemot colony census sites in Kachemak Bay. 

Appendix 12.1. Morphometrics of breeding adult Homed Puffins at Duck Island. 

Appendix 13.1. Summary of glaucous-winged gull population estimates on plots in 

lower Cook Inlet colonies. 

Appendix 13.2. Glaucous-winged Gull calculated population plot count windows, 

defined as the period between mid-incubation and the start of fledging and the 

actual range of count dates used at Chisik and Gull Islands, 1995-1 999. 

Appendix 13.3. Summary of glaucous-winged gull population estimates in selected 

lower Cook Inlet colonies. 

Appendix 13.4. Summary of Double-crested (DCCO), Pelagic (PECO), and red-faced 

cormorant (RFCO) population estimates on plots in lower Cook Inlet colonies. 

Appendix 13.5. Calculated and actual count windows for Pelagic Cormorant population 

plots on Gull Island 1995- 1999. 

Appendix 13.6. Summary of Double-crested (DCCO), Pelagic (PECO), and red-faced 

cormorant (RFCO) population estimates in selected lower Cook Inlet colonies. 

Appendix 13.7. Count windows used for Tufted Puffin population plot counts as 

compared to estimated breeding chronology determined from chick measurements 

in 1997, Gull Island. 
Chapter 1. Introduction and Project Overview 

John Piatt 

The Cook Inlet Seabird and Forage Fish Study (CISeaFFS, or 'Sisyphus') was established 

in 1995 with EVOSTC (APEX), USGS, MMS and FWS support to measure the foraging 

(functional) and population (numerical) responses of seabirds to fluctuating forage fish 

densities around three seabird colonies in lower Cook Inlet. This involved at-sea surveys 

for forage fish (hydro-acoustics, trawling, seining) and seabirds (line transects), and some 

characterization of oceanography (AVHRR satellite imagery, CTD profiles, moored 

thermographs), while simultaneously measuring aspects of seabird breeding biology (egg 

and chick production, chick growth, population trends) and foraging behavior (diets, 

feeding rates, foraging time) at adjacent colonies. Seabird data from colonies at Chisik and 

Gull islands were collected by USGS, data from the Barren Islands were collected by the 

Alaska Maritime National Wildlife Refuge (APEX Project 001635, Barren Islands Seabird 

Studies). Field work reported on here was conducted during 1995-1999 (although colony, 

stress and survival work continued until 2001). Findings are presented here in 247 tables, 

figures and appendices. A synthesis of results for murres and kittiwakes is provided in 

Chapter 14. This report is not a final synthesis of all results, rather, it is a milestone on the 

way to publication of results in peer-reviewed scientific publications (see progress below). 

This report provides a compilation and summary of major data sets from Cook Inlet 

research and it accompanies a digital archive of all raw and summary data collected on this 

project. Further detailed analyses and syntheses of fish and seabird data in the archive will 

follow in peer-reviewed journal articles. 

CISeaFFS Publications to Date: The following 6 1 peer-reviewed articles have been 

submitted or published at the time of writing this final report, and stand as part of this 

report. PDF versions are at: www.absc.usgs.gov/research/seabird~fo~ or 

can be obtained from the Principal Investigator. Most of these papa arise directly from 

work conducted in Cook Inlet or Prince William Sound with hding from the EVOSTC 

and USGS, or they are related publications (indicated with *) that were written by 

investigators supported wholly or in large part with EVOSTC funds in 1995-200 1. 

Authors supported under EVOSTC funded projects include: Abookire, Drew, Figurski, 

Harding, Henkel, Kettle, Kitaysky, Litzow, Neuman, Nielsen, Piatt, Robards, Romano, 

Shultz, Van Pelt, and Zador. 

Abookire, A.A. and B.L. Norcross. 1998. Depth and substrate as determinants of 

distribution of juvenile flathead sole (Hippoglossoides elassodon) and rock sole 

(Pleuronectes bilineatus) in Kachemak Bay, Alaska. Journal Sea Research 

39:113-123.* 

Abookire, A.A., J.F. Piatt and M. Robards. 2000. Nearshore fish distributions in an 

Alaskan estuary in relation to stratification, temperature and salinity. Estuarine and 

Coastal Shelf Science 5 1: 45-59. 
Abookire, A.A. and J.F. Piatt. 2003. Structure of forage fish communities in relation to 

oceanographic conditions in lower Cook Inlet, Alaska. Submitted to Marine 

Ecology Progress Series. 

Abookire, A.A., J.F. Piatt, and B.L. Norcross. 2001. Summer habitat of juvenile 

groundfishes in Kachemak Bay, Alaska. Alaska Fisheries Research Bulletin 8(1): 

45-56. 

Abookire, A.A., J.F. Piatt, and S. Speckman. 2002. A near-surface, daytime occurrence of 

two mesopelagic fish species (Stenobrachius leucopsarus and Leuroglossus 

schmidti) in a glacial fjord. Fishery Bulletin 100: 376-380.* 

Anderson, P.J., and J.F. Piatt. 1999. Community reorganization in the Gulf of Alaska 

following ocean climate regime shift. Marine Ecology Progress Series 189: 1 17- 

123. 

hstrong, R.H., M.F. Willson, M.D. Robards, and J.F. Piatt. 1999. Sand lance: 

Annotated Bibliography. Pp. 45-327 in Robards, M. D., Willson, M. F. 

Armstrong, R.H., Piatt, J.F., (4s). Sand lance: a review of biology and predator 

relations and annotated bibliography. Research Paper PNW-RP-52 1. Portland, OR, 

U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station. 327 p. 

Benson, J., R. Suryan, and J.F. Piatt. 2003. Assessing chick growth fiom a single visit to a 

seabird colony. Marine Ornithology, in review. 

Congdon, B.C., J.F. Piatt, K. Martin and V.L. Friesen. 2000. Mechanisms of population 

differentiation in marbled murrelets: historical versus contemporary processes. 

Evolution 54: 974-986.* 

Harding, A. M. 200 1. The breeding ecology of Homed Puffins Fratercula corniculata. 

M.Sc. Thesis, University of Durham, England. 74 pp. 

Harding, A.A., T. van Pelt, J.F. Piatt, and A.S. Kitaysky. 2002. Reduction of provisioning 

effort in response to experimental manipulation of chick nutritional status in the 

homed puffin Fratercula corniculata. Condor 104: 842-847. 

Harding, A.M.A, J.F. Piatt and K.C. Hamer. 2003. Breeding ecology of Homed Puffins 

(Fratercula corniculata) in Alaska: Annual variation and effects of El Niiio. 

Canadian Journal of Zoology 8 1 : 1004- 101 3. 

Harding, A.H., J.F. Piatt, G.V. Byrd, S.A. Hatch, N. Konyukhov, E.U. Golubova and J.C. 

Williams. 2003. Measuring variability in colony attendance of crevice-nesting 

Homed Puffin throughout the North Pacific: Implications for population 

monitoring. Submitted to J. Wildlife Management. 

Kitaysky, A.S. 1999. Metabolic and developmental responses of alcid chicks to 

experimental variation in food intake. Physiological and Biochemical Zoology 72: 

462-473. * 

Kitaysky, A.S., J.C. Wingfield, and J.F. Piatt. 1998. Dynamics of food availability, body 

condition and physiological stress response in breeding Black-legged kittiwakes. 

Functional Ecology 13577-584. 

Kitaysky, A., J. Wingfield, and J. Piatt. 2001. Corticosterone facilitates begging and 

affects resource allocation in the Black-legged Kittiwake. Behavioural Ecology 

12:619-625. 
Kitaysky A.S., Kitaiskaia E.V., Wingfield J.C., Piatt J.F. 2001. Dietary restriction causes 

chronic elevation of corticosterone and enhances stress-response in Red-legged 

kittiwake chicks. J. Comp. Physiol. (B) 171 :70 1 -709.* 

Kitaysky, A.S., J.F. Piatt, J.C. Wingfield, and M. Romano. 1999. The adrenocortical 

stress-response of Black-legged Kittiwake chicks in relation to dietary restrictions. 

Journal of Comparative Physiology (B):303-3 10. 

Kitaysky, A.S., G.L. Hunt, Jr., E.L. Flint, M.A. Rubega, M.B. Decker. 2000. Resource 

allocation in breeding seabirds at the Pribilof islands. Marine Ecology Progress 

Series 206:283-296.* 

Kitaysky, A.S., E.V. Kitaiskaia, J.F. Piatt, and J.F. Wingfield. 2002. Benefits and costs of 

increased levels of corticosterone in seabird chicks. Submitted to J. Comp. 

Physiol. * 

Kitaysky, A.S., E.V. Kitaiskaia, J.F. Piatt, and J.F. Wingfield. 2003. Benefits and costs of 

increased levels of corticosterone in seabird chicks. Hormones and Behavior, in 

review. 

Kuletz, K. and J.F. Piatt. 1999. Juvenile Marbled Murrelet nurseries and the productivity 

index. Wilson Bulletin 1 1 1 :257-26 1. 

Kuletz, K.J., D.Irons, J.F. Piatt, B. Agler and D.C. Duffy. 1997. Long-term changes in 

populations and diets of piscivorous birds and mammals in Prince William Sound, 

Alaska. Proceedings, Forage Fishes in Marine Ecosystems. Alaska Sea Grant 

College Program, University of Alaska Fairbanks, AK-SG-97-01: 703-706. 

Litzow, M.A. 2000. Food limitation in a generalist seabird: reproductive consequences of 

food quality and prey switching in the Pigeon Guillemot (Cepphus columba). 

M.Sc. Thesis, University of California, Santa Cruz, CA. 36 pp. 

Litzow, M. A. and J.F. Piatt. 2003. Variance in prey abundance influences time budgets of 

breeding seabirds: evidence from pigeon guillemots. J. Avian Biol34: 54-64. 

Litzow, M.A., J.F. Piatt, and J.D. Figurski. 1998. Hermit crabs in the diet of Pigeon 

Guillemots at Kachemak Bay, Alaska. Colonial Waterbirds. 2 1 :242-244. 

Litzow, M.A., J.F. Piatt, A. Abookire, M. Robards. 2002. Quality-predictability tradeoffs 

for piscivores: covariation of fish energy density and availability in the nearshore 

North Pacific. Submitted to Ecol. Letters. 

Litzow, M. A., J.F. Piatt, A. K. Prichard and D. D. Roby. 2002. Response of pigeon 

guillemots to variable abundance of high-lipid and low-lipid prey. Oecologia 132: 

286-295. 

Litzow, M. A., J.F. Piatt, A.A. Abookire, A.K. Prichard, and M.D. Robards. 2000. 

Monitoring temporal and spatial variability in sandeel (Ammodytes hexapterus) 

abundance with pigeon guillemot (Cepphus columba) diets. ICES Journal of 

Marine Science 57: 976-986. 

Newman, S.H., J.F. Piatt, and J. White. 1997. Hematological and plasma biochemical 

reference ranges of Alaskan seabirds: their ecological significance and clinical 

importance. Colonial Waterbirds 20:492-504.* 

Ostrand, W. D., K. 0. Coyle, G. S. Drew, J. M. Maniscalco, and D. B. Irons. 1998. 

Selection of forage fish schools by murrelets and Tufted Puffins in Prince William 

Sound, Alaska. Condor. 100:286-297. 
Ostrand, W.D, G. S. Drew, R. M. Suryan, and L. L. McDonald. 1998. Evaluation of 

radio-tracking and strip transect methods for determining foraging ranges of 

Black-legged Kittiwakes. Condor. 100:709-7 1 8. 

Ostrand, W. D., T. A. Gotthardt, S. Howlin, J. Kem, and M. D. Robards. 2000. Habitat 

selection by Pacific sand lance in Prince William Sound, Alaska. Submitted to 

Fishery Bulletin. 

Piatt, J. 1995. Water ova the bridge. American Scientist 83:396-398.* 

Piatt, J.F. 1997. Alternative interpretations of oil spill data. Bioscience 47:202-203. 

Piatt, J.F., and P. J. Anderson. 1996. Response of Common Murres to the Exxon 

Valdez oil spill and long-term changes in the Gulf of Alaska marine 

ecosystem. Pp. 720-737 in: Exxon Valdez Oil Spill Symposium 

Proceedings. Rice, S. D., R. B. Spies, D. A. Wolfe and B. A. Wright (Eds). 

American Fisheries Society Symposium 18, Bethesda, Maryland. * 

Piatt, J.F., and R. G. Ford. 1996. How many seabirds were killed by the Exxon 

Valdez oil spill? Pp. 712-71 9 in: Exxon Valdez Oil Spill Symposium 

Proceedings. Rice, S. D., R. B. Spies, D. A. Wolfe and B. A. Wright, 

(Eds). American Fisheries Society Symposium 18, Bethesda, Maryland.* 

Piatt, J.F. and A.S. Kitaysky. 2002. Homed Puffin (Fratercula corniculata). In 

The Birds of North America, No. 61 1 (A. Poole and F. Gill, Eds.). The 

Birds of North America, Inc., Philadelphia, PA. Pp. 1-27.* 

Piatt, J.F. and A.S. Kitaysky. 2002. Tufted Puffin (Fratercula cirrhata). In The Birds of 

North America, No. 708 (A. Poole and F. Gill, Eds.). The Birds of North America, 

Inc., Philadelphia, PA. Pp. 1-32.* 

Piatt, J.F. and T.I. van Pelt. 1997. Mass-mortality of guillemots (Uria aalge) in the Gulf 

of Alaska in 1993. Marine Pollution Bulletin 34: 656-662.* 

Piatt, J.F., N.L. Naslund, and T.I. van Pelt. 1999. Discovery of a new Kittlitz's Murrelet 

nest: Clues to habitat selection and nest-site fidelity. Northwestern Naturalist 80:8- 

13.* 

Piatt, J.F., D.D. Roby, L. Henkel, and K. Neuman. 1998. Habitat use, diet, and breeding 

biology of Tufted Puffins in Prince William Sound, Alaska. Northwestern 

Naturalist 78: 102- 109. 

Piatt, J.F., G. Drew, T.Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711 998 ENS0 event in lower Cook Inlet, 

Alaska. PICES Scientific Report No. 10:93- 100. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fisheries 

Bulletin 97: 962-977. 

Robards, M.D. 2000. Ecology and demographics of Pacific sand lance, Ammodytes 

hexaptems Pallas, in lower Cook Inlet, Alaska. M.Sc. Thesis, Memorial University 

of Newfoundland, St. John's, Canada. 105 pp. 

Robards, M.D., J.F. Piatt, and G.A. Rose. 1999. Maturation, fecundity and intertidal 

spawning of Pacific Sand Lance (Ammodytes hexaptems) in the northern Gulf of 

Alaska. Journal of Fish Biology 54: 1050- 1068. 
Robards, M.D., G.A. Rose, and J.F. Piatt. 2002. Growth and abundance of Pacific sand 

lance, Ammodytes hexapterus, under differing oceanographic regimes. 

Environmental Biology of Fishes. 64: 429-44 1. 

Robards, M.D., J. Anthony, J.F. Piatt, and G. Rose. 1999.Changes in proximate 

composition and somatic energy content for Pacific sand lance (Ammodytes 

hexapterus) relative to maturity and season in Kachemak Bay, Alaska. Journal of 

Experimental Marine Biology and Ecology. 242: 245-258. 

Robards, M. D., Willson, M. F. Armstrong, R.H., Piatt, J.F., (eds). 1999. Sand lance: a 

review of biology and predator relations and annotated bibliography. Research 

Paper PNW-RP-52 1. Portland, OR, U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station. 327 p. 

[http://www.fs.fed.us/pnw/pubs.htm] 

Robards, M.D., and J.F. Piatt. 1999. Biology of the Genus Ammodytes - The Sand 

Lances. Pp. 1-1 6 in Robards, M. D., Willson, M. F. Armstrong, RH., Piatt, J.F., 

(eds). Sand lance: a review of biology and predator relations and annotated 

bibliography. Research Paper PNW-RP-52 1. Portland, OR, U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 327 p. 

Romano, M.D. 2000. Effects of diet on growth and development of nestling seabirds. 

M.Sc. Thesis, Oregon State University, Corvallis OR. 59 pp. 

Seiser, P. E., L. K. Due, A. D. McGuire, D. D. Roby, G. H. Golet, and M. A. Litzow. 

2000. Comparison of pigeon guillemot, Cepphus columba, blood parameters from 

oiled and unoiled areas of Alaska eight years after the Exxon Valdez oil spill. 

Marine Pollution Bulletin 40: 152- 164. 

Shultz, M., J.F. Piatt, et al. 2003. Timing of breeding in seabirds. Submission to J. him. 

Ecol. 

Speckman, S.G. and J.F. Piatt. 2000. Historic and current use of Lower Cook Inlet, 

Alaska, by Belugas, DeZphinapterus leucas. Marine Fisheries Review. 62(3): 22- 

26. 

Speckman, S.G., J.F. Piatt, and A.M. Springer. 2003. Deciphering the social structure of 

Marbled Murrelets from behavioral observations at sea. Waterbirds 26(3): 266- 

274.* 

Speckman, S.G., A.M. Springer, J.F. Piatt and D.L. Thomas. 2000. Temporal variability 

in abundance of Marbled Murrelets at sea in southeast Alaska. Waterbirds 364- 

377.* 

Van Pelt, T.I. 2000. Reproductive costs and their expression in the Common Guillemot 

Uria aalge. M.Sc. Thesis, University of Glasgow, Scotland. 119 pp. 

Van Pelt, T.I., and J.F. Piatt. 1995. Deposition and persistence of beachcast seabird 

carcasses. Marine Pollution Bulletin 30:794-802.* 

Van Pelt, T.I., J.F. Piatt, and G.B. van Vliet. 1999. Vocalizations of the Kittlitz's 

Murrelet. Condor 10 1 :395-398.* 

Van Pelt, T., J.F. Piatt, B.K. Lance, and D.D. Roby. 1997. Proximate composition and 

energy density of some North Pacific forage fishes. Comparative Biochemistry and 

Physiology 118(A): 1393-1398. * 
Willson, M.F., R.H. Armstrong, M.D. Robards, and J.F. Piatt. 1999. Sand lance as 

cornerstone prey for predator populations. Pp. 17-44 in Robards, M. D., Willson, 

M. F. Armstrong, R.H., Piatt, J.F., (eds). Sand lance: a review of biology and 

predator relations and annotated bibliography. Research Paper PNW-RP-52 1. 

Portland, OR, U.S. Department of Agriculture, Forest Service, Pacific Northwest 

Research Station. 327 p. 

Zador, S., and J.F. Piatt. 1998. Time-budgets of Common Murres at a declining and 

increasing colony in Alaska. Condor 10 1 : 149- 1 52. 

Introduction 

Some seabird populations in the Gulf of Alaska declined markedly during the past few 

decades (Hatch and Piatt 1995; Piatt and Anderson 1996). Whereas human impacts such 

as those from the Exxon Valdez oil spill can account for some proportion of these declines 

(Piatt et al. 1990~; Piatt and Naslund 1995), natural changes in the abundance and species 

composition of forage fish stocks have also affected seabird populations (Decker et al. 

1994; Piatt and Anderson 1996). Marine fish communities in the Gulf of Alaska changed 

dramatically during the past 20 years (Anderson et al. 1994). Coincident with cyclical 

fluctuations in sea-water temperatures, the abundance of small forage fish species such as 

capelin (Mallotus villosus) declined precipitously in the late 1970's while populations of 

large predatory fish such as walleye pollock (Theragra chalcogramma) and cod (Gadus 

macrocephalus) increased dramatically. Correspondingly, capelin virtually disappeared 

fiom seabird diets in the late 197OVs, and were replaced by juvenile pollock and other 

species in the 1980's (Piatt and Anderson 1996). Seabirds and marine mammals exhibited 

several signs of food stress (population declines, reduced productivity, die-offs) 

throughout the 1980's and early 1990's (Merrick et al. 1987; Piatt and Anderson 1996). 

Similar trends in oceanography, seabird population biology and prey availability have been 

noted in the Bering Sea, although the cycle there appears to be offset by 4-5 years from 

events in the Gulf of Alaska (Decker et al. 1994, Springer 1992). 

Factors that regulate seabird populations are poorly understood, but food supply is clearly 

important (Cairns 1992b). In many cases, anthropogenic impacts on seabird populations 

cannot be distinguished fiom the consequences of natural variability in food supplies (Piatt 

and Anderson 1996). Thus, 'management' of seabird populations remains an uncertain 

exercise. For example, how can we enhance recovery of seabird populations lost to the 

Exxon Valdez oil spill if food supplies in the Gulf of Alaska limit reproduction? Would 

commercial fishery closures reduce or increase food availability to seabirds? What are the 

minimum forage fish densities required to sustain seabirds, and how do we maintain those 

critical densities? 

We attempted to answer some of these questions in our study of seabird and forage fish 

interactions in lower Cook Inlet. Upwelling of oceanic water at the entrance to Cook 

Inlet creates a productive marine ecosystem that currently supports about 2-3 million 

seabirds during summer. More seabirds breed here than in the entire northeast Gulf of 
Alaska (including Prince William Sound) and concentrations at sea (up to 90 kg/km2) are 

among the highest in Alaska (Piatt 1994). For these reasons, the greatest damage to 

seabirds from the Exxon Valdez oil spill occurred in lower Cook Inlet (Piatt et al. 1990). 

Functional relationships between seabird predators and their prey are poorly known 

because the vast majority of seabird research has been conducted on colonies without 

benefit of concurrent studies at sea on prey availability and seabird foraging behavior 

(Hunt et al. 1991). The response of seabirds to environmental change can vary widely 

among species, and is influenced by a host of physical and biological factors. Differential 

adaptations of seabirds for exploiting plankton and fish, widely-varying foraging abilities 

and breeding strategies, and complex relationships between oceanography and prey 

dispersion, abundance, and behavior all serve to complicate our interpretation of changes 

in seabird population biology. Therefore, in order to assess the potential for recovery of 

seabirds affected by the Exxon Valdez oil spill, a concurrent, multi-disciplinary study of 

oceanography, forage fish, and seabirds was required. 

Coordinated studies of seabird breeding biology and feeding ecology in relation to local 

prey abundance are remarkably few (for examples, see Safina and Burger 1985, 1988; 

Monaghan et al. 1989, 1994; Hamer et al. 1991, 1994; Uttley et al. 1994). Following a 

collapse of capelin stocks and concern about the possible consequences for Atlantic 

Pufis (Fratercula arctica) (Brown and Nettleship 1984), detailed studies of the 

relationships between oceanography, capelin (Mallotus villosus), cod (Gadus morhua), 

common murres (Uria aalge), Atlantic puffins and baleen whales were conducted in 

eastern Newfoundland in 198 1-1985 (Montevecchi and Piatt 1984, 1987; Piatt and 

Nettleship 1985; Burger and Simpson 1986; Schneider and Piatt 1986; Cairns et al. 1987, 

1990; Piatt 1987, 1990; Schneider and Methven 1988; Methven and Piatt 1989, 1991; 

Piatt et al. 1989; Schneider 1989; Burger and Piatt 1990; Schneider et al. 1990; Nettleship 

199 1 ; Piatt and Methven 1992). 

Results of these studies provide an empirical basis for hypotheses about relationships 

between seabirds and their prey in a variable marine environment (Table I. I). 

Relationships between population biology and feeding ecology can be quantified within an 

established hmework of predation theory (Holling 1959; Murdoch and Oaten 1975; Piatt 

1987). Adult survival, reproductive success and population growth (the "numerical 

response") of higher vertebrates depends largely on the rate at which food (energy) can be 

extracted from the environment (the "functional response"). 

For individual seabirds, the functional response incorporates all parameters relating to the 

capture of prey (Table 1.1). Studies have demonstrated or hypothesized that these 

parameters are non-linear functions of prey density that operate over time-scales of hours 

to days, and spatial scales of meters to kilometers. For example, foraging time declines 

with increasing prey density (Cairns et al. 1987; Monaghan et al. 1989, 1994) allowing 

more free time for other activities (Burger and Piatt 1990). Similarly, as prey densities 

increase, foraging ranges may contract by 10's of km (Cairns et al. 1990; Monaghan et al. 
1994) resulting in a considerable reduction in foraging energy expenditure (Cairns et al. 

1987) and greater prey harvests in the vicinity of colonies (Cairns et al. 1990). 

Numerical response parameters for seabirds (Table 1.1) are, in the absence of stochastic 

mortality events (e.g., oil mortality), a direct function of food availability over longer time 

scales (months and years) and larger spatial scales (100's to 1000's of kilometers). Thus, 

population change in seabirds reflects day-to-day foraging success integrated over 

reproductive time-periods and the area over which populations are distributed (Cairns 

1987, 1992a,b; Piatt 1987). 

The numerical and functional responses of individual species to changes in prey density are 

almost always non-linear, frequently sigmoidal, and species-specific with regard to 

absolute density thresholds (Holling 1959; Murdoch and Oaten 1972; Piatt 1990; Piatt and 

Methven 1991). In other words, some seabird species may prosper at low levels of prey 

density while others require much higher densities (Piatt 1987, 1990). Cairns (1 987) 

further hypothesized that components of the numerical and functional response in 

individual species of seabirds are sensitive to different levels (thresholds) of prey density. 

For example, adult survivorship is probably quite high over a wide range of medium to 

high prey densities, but at some low, critical level, adult survival diminishes rapidly. In 

contrast, when seabirds are constrained to forage locally during the breeding season and 

food demands are high (for both adults and chicks), then moderate to high prey densities 

are required to maintain high breeding success. 

Some species may be able to buffer against variation in their numerical and functional 

response by adjusting their foraging effort as prey densities fluctuate (Piatt 1987, 1990; 

Burger and Piatt 1990; Uttley et al. 1994; Monaghan et al. 1994). Other species may have 

little buffering capacity because they are pushed to their limits even under normal 

circumstances (Goudie and Piatt 1991; Hamer et al. 1994). Thus, in some species (e.g., 

murres), chick feeding rates or breeding success may not be affected over a wide range of 

prey densities because adults simply spend more time foraging to compensate for the 

change in prey density. Components of numerical and functional responses that may be 

buffered (Table 1.1) are therefore less sensitive indicators of prey fluctuations (Burger and 

Piatt 1990). 

Numerical and functional responses are scale-dependent, and may be evident only when 

examined over appropriate temporal or spatial scales (Schneider and Piatt 1986; Piatt 

1987, 1990). Weather, wind, and oceanographic processes profoundly influence the 

biology and distribution of prey species (Schneider and Methven 1988; Methven and Piatt 

1991), and may largely determine the temporal and spatial scales at which seabird foraging 

occurs (Schneider 1989). Although physical processes can influence the density and 

availability of prey to seabirds, they should not change the basic direction and form of 

numerical and functional responses (Table 1. I), and probably have minimal effects on 

thresholds-- which are largely a species-specific function of seabird body size and behavior 

(Piatt 1987, 1990; Goudie and Piatt 1991). 
The challenge in this project was to measure the form and scale of seabird responses to 

prey fluctuations in light of variability in the marine environment. Quantifying responses of 

higher vertebrates in the field can be difficult because of logistical difficulties in measuring 

key parameters (Goss-Custard 1970), and the lack of power to manipulate predator and 

prey densities over the full range of possibilities (Piatt 1990). For seabirds, it required the 

coordination of studies on breeding biology and behavior at colonies, and studies of 

seabird and prey dispersion at sea in relation to local oceanography. 

1) To describe and quantify the numerical and functional responses of seabirds (Table 

1.1) to seasonal and annual fluctuations in local prey density at three colonies in 

lower Cook Inlet. 

2) To describe spatial distributions of seabirds and prey, and measure the absolute 

densities of some prey schools, around three seabird colonies in lower Cook Inlet. 

3) To test a number of hypotheses (Table 1.1) about how responses of different 

seabird species vary with regard to prey characteristics and oceanographic 

conditions. 

4) To gather baseline data for future reference in lower Cook Inlet on: i) seabird 

populations, breeding biology, diets, and distribution; ii) prey distribution, relative 

abundance, and composition; and, iii) basic oceanographic parameters. 

Methods 

Specific methods employed for each component of the study are described in detail in each 

of the following chapters. The general strategy employed for the study is described below. 

Measuring Responses: A variety of techniques were used to measure the numerical and 

functional responses of seabirds to prey density (Table 1.1). The basic elements of the 

study required: 

1) The distribution and abundance of prey species was measured hydro-acoustically 

(using a Biosonics DT4000 digital echosounder) and with trawls (bottom, 

midwater) over an area extending at least 45 km away fiom each of the colonies. 

(e.g., Piatt 1987, 1994; Piatt et al. 1990a; Hunt et al. 1993). Because potential 

foraging area increases geometrically with distance fiom the colony, the areal 

extent of surveys was chosen to balance the need for sampling of important 

foraging areas within the range of birds against the practical limitations of time and 

resources. Fish catches were needed to groundtruth the hydroacoustic surveys, and 

to assess species and age-class composition of remotely-detected prey schools 

(Piatt 1987; Schneider and Methven 1988). Prey specimens collected fiom trawls 

and seabird chicks were examined to assess prey species composition, sex-ratios, 
body condition, and energetic content. In addition to trawling, we sampled 

nearshore fish schools using beach seines, cast-nets and SCUBA transects. 

2) Concurrent measures of physical parameters such as wind speed, sea state, sea 

surface temperature and salinity, and salinity-temperature profiles of the water 

column (e.g., Schneider and Methven 1988; Piatt et al. 1990a; Hunt et al. 1993). 

3) Measuring components of the numerical response (Table 1.1). Most of these 

parameters were measured at the colony by direct observation or measurement 

(e-g., Gaston et al. 1983; Harris and Wanless 1988; Wanless et al. 1982). 

Estimating survival was a more time-consuming activity and required the banding 

and re-sighting of adults in subsequent years (Sydeman 1993; Hatch et al. 1994). 

4) Measuring components of the functional response (Table 1.1). Diet components 

required collection of adult and chick prey items, at colonies and at sea (e.g., Piatt 

1987; Burger and Piatt 1990). Study of aggregation behavior required 

simultaneous surveys of seabird and prey dispersion at sea (Piatt 1990, 1994; Piatt 

et al. 1990a). Aspects of seabird foraging behavior (mge, activity budgets, chick 

feeding rates) were studied by direct observation of birds at nest-sites (e.g., 

Monaghan et al. 1994; Uttley et al. 1994). 

Study Desim: The approach used in this study was to quantifl the numerical and 

functional responses of seabirds at spatial scales ranging fiom fine (m to km, Gull Island in 

Kachemak Bay) to moderate (1 0s- 100s km, lower Cook Inlet). Similarly, and where 

possible, variability in response parameters was measured at small (daily, seasonal) and 

moderate (annual) temporal scales. At fine and moderate spatial scales, two species of 

seabird (common murre and black-legged kittiwake) were studied in detail at three 

different colonies in lower Cook Inlet. Ancillary data were collected on 6 other seabird 

species. In total, the study included two surface-feeding seabirds (lattiwake and glaucouswinged gull), three pelagic-diving seabirds (common murre, horned and tufted puffins), 

and three benthic-diving seabirds (guillemot, pelagic and double-crested cormorant). Some 

of these species forage mostly near shore (4 km) whereas others feed more offshore (& 

60 km; Piatt 1994). 

Studies were conducted at and around Gull, Chisik and Barren islands in lower Cook Inlet 

(see Fig. 8-1). Gull and Chisik islands provided an excellent contrast for studies of 

numerical and functional responses because they: i) share a similar suite of breeding 

species; ii) have markedly different population dynamics (Slater et al. 1994); and, iii) differ 

in their local oceanographic regimes. Whereas Gull Island seabird populations had 

increased by 40-80% in the 2 decades prior to this study, Chisik Island populations had 

declined by similar magnitudes over the same time period. The Barren Islands share a 

similar suite of species and breeding success had varied between poor and excellent in the 

2 decades prior to this study (Manuwal 1980; Roseneau et al. 1994). 
Hypothesis Testing: The data gathered fiom this study on numerical and functional 

responses of seabirds to variations in prey density (Table 1.1) can be used to test a variety 

of hypotheses about how seabirds respond to changes in their marine environment. 

Specific hypotheses will be addressed in peer-reviewed publications. For example, at the 

largest scales of study, we wanted to know whether long-term changes in forage fish 

abundance were due to changes in marine climate (Anderson et al. 1994), and whether 

these changes were responsible for seabird population declines (Piatt and Anderson 1996). 

Analysis of a 45-year data set on forage fish supports at least the first of these hypotheses 

(Anderson and Piatt 1999). We have already examined hypotheses about how 

oceanographic conditions influence prey density and distribution in the water column (e.g., 

Robards et al. 1999,2002, Abookire et al. 2000), seabird foraging success (e.g., Litzow et 

al.. 2000, Harding et al. 2002), and, in turn, the reproductive biology and physiology of 

seabirds (e.g., Kitaysky et al. 1998, Piatt et al. 1999). Hypotheses about the exact form of 

numerical and functional responses (Cairns 1987), and differences between species in their 

responses (Piatt 1990, Goudie and Piatt 1991) will be examined in the preliminary 

synthesis of chapter 14, and in subsequent publications. 

Summarv of Results 

Populations, productivity, diets and foraging behavior of Common Murres and Blacklegged Kittiwakes were studied at three seabird colonies in lower Cook Inlet (Chisik, Gull 

and Barren islands). Ancillary data were also collected on Tufted and Homed Puffins, 

Cormorants (spp.) and Glaucous-winged Gulls. Pigeon Guillemots were studied in 

Kachemak Bay only. Oceanographic measurements, seabird and hydroacoustic surveys, 

trawls, and beach seines were conducted in waters around (<45 km) each colony. In all 

years, offshore and southern waters of Cook Inlet were dominated by juvenile walleye 

pollock, important prey for murres and puffins. Nearshore waters of Cook Inlet were 

dominated by sandlance, which were consumed by adult kittiwakes and murres in 

proportion to their local abundance. Both species fed chicks more prey that were rich in 

fat (e.g., capelin, herring). The CPUE of forage fish in either mid-water trawls or beach 

seines around Chisik Island was typically 1-2 orders of magnitude less than around the 

Barren Islands, with Kachemak Bay yielding intermediate CPUE's. Acoustically-measured 

forage fish biomass was also lowest around Chisik Island, highest in Kachemak Bay and 

along the Kenai Peninsula, and moderate around the Barren Islands. Water temperatures 

throughout the summers of 1995-1999 were similar and near the long-term average, but 

temperatures in winter of 1997198 were about 1-2 C higher than in previous years owing 

to warming from El Ni5o. 

The breeding biology of seabirds differed markedly among colonies owing to persistent 

geographic differences in forage fish abundance described above. Birds at Chisik Island 

struggled to reproduce, while those at Gull and Barren islands usually had few problems 

rearing young. Within each colony, breeding and behavioral parameters varied among 

years to a lesser degree than among sites (1995-1999). Breeding success in all species was 

lower in 1998 than in other years; presumably a lingering effect of the previous winters' El 
Niiio event. Murres on Chisik Island nearly failed-- the first time we observed a murre 

failure at any colony since studies began in 1995. Measures of corticosteroid hormones in 

1998 suggested that murres on Chisik were highly stressed even before they attempted to 

lay eggs in July. A large die-off of murres was observed in Cook Inlet in April and May of 

1998, and although most birds affected were subadults, this die-off foreshadowed a poor 

breeding season. Breeding success of kittiwakes at Gull, Barren and Chisik islands was 

also lower in 1998 than in any other years, and kittiwakes failed at both Chisik and the 

Barrens. Population censuses revealed that seabirds at Chisik Island continued in a longtenn decline, whereas populations at Gull and Barren islands were stable or increasing. 

Behavioral studies revealed that seabirds worked harder (longer foraging trips, less 

discretionary time) at colonies where nearby fish densities were lower (Chisik). 

Preliminary results of survival studies suggest that the survival rate of adult kittiwakes on 

Chisik Island was substantially higher on Chisik than Gull Island, while survival of murres 

appeared to be similar between the islands. 

Results showed that seabird parameters (breeding success, foraging effort, population 

trend, etc.) varied most between islands and to a lesser degree between years. We attribute 

this regional variability and temporal stability in seabird biology to distinct, persistent 

oceanographic regimes around each colony that determined the availability of fish to birds 

within those areas. While each colony responded differently to the ENS0 perturbation of 

1997198, responses were commensurate with the underlying physical and biological regime 

observed in each area. As predicted, the numerical and functional responses of seabirds to 

food density were non-linear in most cases. For example, kittiwake hatching, fledging and 

breeding success were all sigmoidal functions of prey density. Breeding success was not 

correlated with prey density in murres because when food got scarce, murres reallocated 

discretionary "loafing" time to foraging, thereby buffering the ability to rear chicks under 

poor feeding conditions. For murres, "loafing" time was a sigmoidal function of prey 

density. Examination of the response curves for each parameter of breeding in murres and 

kittiwakes suggests that food supplies at Gull and Barren islands- but not at Chisik- are 

above threshold limits and are presently adequate to support recovery of losses from the 

Exxon Valdez oil spill. 

The Cook Inlet Seabird and Forage Fish Project would not have been possible without the 

help of a great many people. At the Alaska Science Center (BRD, USGS), Leslie HollandBartels, Dede Bohn, Eric Knudsen, Lyman Thorsteinsen, William Seitz, Dirk Derksen; and 

at the Alaska Maritime NWR (USFWS), Dave Roseneau, Vernon Byrd and Dan Boone; 

provided unflagging support for the project. We also appreciated the ongoing support 

provided by the EVOS Trustee Council & Scientists (Robert Spies, Andy Gunther, Molly 

McCammon, Stan Senner, Phil Mundy); APEX colleagues David Dm, Bruce Wright, 

Dan Roby, David Irons, Lew Haldorson, Kathy Kuletz, Bill Ostrand; MMS (Steve Treacy, 

Joel Hubbard), ADF&G (James Brady, Bill Bechtol, Jim Blackbume); NMFS (Paul 

Anderson); UAF (Alan Springer, Kathy Turco, Brenda Norcross, Alex Prichard, Peter 

McRoy) and UW (John Wingfield). We are grateful to the captains and crews of the MN 
Tiglax (Capt. Kevin Bell), RNPandalus (Capts. Paul Desjardins and Mark Hauptman) 

and RN David Grey (Greg Snedgen) for enthusiastic support at sea. The field work was 

conducted by an indefatigable crew including (besides the contributors to this report): 

Carrie Alley, Mayurni Arimitsu, Jeb Benson, David Black, Margi Blanding, Dan Boone, 

Alice Chapman, Elizabeth Chilton, Brad Congdon, Brian Duggan, Mitch Eaton, Jared 

Figurski, Lilly Goodman, Mike Gray, Celia Hall, Greg Hoffman, Keith Hobson, Brenda 

Holliday, Brad Keitt, Roman Kitaysky, Matt Kopec, Mark Kosmerl, Cliff Lascink, Jennifer 

Litzow, Vinay Lodha, Jonathon Maletta, Kali Mangel, Ann Meckstroth, Jeff Moy, Holly 

Ober, Leigh Ochikubo [Chan], Ramie1 Papish, Jennifer Pierson, Mike Post, Cynthia 

Restrepo, Ed Roberts, Marc Romano, Dan Ruthraff, Martin Schultz, Pam Seiser, Rebecca 

Seymour, John Shook, Brian Smith, Greg Snedgen, Bill Stahl, Robert Suydam, Kim Trust, 

Pam Tuomi, Cindy van Damme, Shiway Wang, Jenny Wetzel, Jo Wilding, Sadie Wright, 

and Stephanie Zuniga. We are particularly gratehl to Ray Highsmith, Mike and Connie 

Geagel, and Sarah Baxter for assistance and hospitality at the Kasitsna Bay Marine Lab 

(UAF), and the Ray Baxter Marine Lab, in Kachemak Bay; to Vern Byrd, Trina Fellows 

and other staff of the AMNWR for logistic support and assistance in Homer; to Bob and 

Dorea Woods at the Snug Harbour Cannery, and Eric Randal, for support and hospitality 

on Chisik Island. We appreciate post-field season analyses of specimens and data by Alan 

Springer and Kathy Turco. Quality of the research was improved with guidance from 

advisors of students who worked on the project, and we thank Tim Birkhead (U. 

Shefield), Jim Estes (UCSC), Vicki Friesen (Queen's U.), Keith Hamer (Durham U.), Pat 

Monaghan (Glasgow U.), Dan Roby (OSU), George Rose (Memorial U. Newfoundland), 

Gordy Swartanan (UW), and John Wingfield (UW) for their input and support. We 

thank all the folks who commented on individual chapters as they were prepared, and in 

particular, Eric Knudsen and Charles Monnett, who reviewed the final report in its 

entirety. 

Literature Cited 

Anderson, P.J., and J.F. Piatt. 1999. Community reorganization in the Gulf of Alaska 

following ocean climate regime shift. Marine Ecology Progress Series 189: 117-123. 

Boersma, P.D., J.K. Parrish, and A.B. Kettle. 1993. Common Murre abundance, 

phenology, and productivity on the Barren Islands, Alaska: The Exxon Valdez oil 

spill and long-term enviro~unental change. Third ASTM Symposium on 

Environmental Toxicology and Risk Assessment: Aquatic, Plant, and Terrestrial. 

American Society for Testing and Materials, Philadelphia, ASTM STP 1219. 29 

PPBrown, R.G.B., and D.N. Nettleship. 1984. Capelin and seabirds in the Northwest 

Atlantic. Pp. 184-194 in: Nettleship, D.N., G.A. Sanger, and P.F. Springer (eds.), 

Marine birds: their feeding ecology and commercial fisheries. Canadian Wildl. 

Serv. Special Publication. Ottawa; 2 12-220. 

Burger, A.E. and M. Simpson. 1986. Diving depths of Atlantic Puffins and Common 

Murres. Auk 103:828-830. 

Burger, A.E. and J.F. Piatt. 1990. Flexible time budgets in breeding Common Murres: 

Buffers against variable prey availability. Studies in Avian Biology 14:7 1-83. 
Burger, A.E., R.P. Wilson, D. Gamier, and M.T. Wilson. 1993. Diving depths, diet, 

and underwater foraging of Rhinoceros Auklets in British Columbia. Can. J. Zool. 

7 112528-2540. 

Cairns, D.K. 1987. Seabirds as indicators of marine food supplies. Biol. Oceanogr. 

5:261-271. 

Cairns, D.K. 1992a. Bridging the gap between ornithology and fisheries science: use 

of seabird data in stock assessment models. Condor 94:811-824. 

Cairns, D.K. 1992b. Population regulation of seabird colonies. Current Ornithol. 9:37- 

61. 

Cairns, D.K., K.A. Bredin, and W.A. Montevecchi 1987. Activity budgets and 

foraging ranges of breeding Common Murres. Auk 104:2 1 8-224. 

Cairns, D.K., Montevecchi, W.A., Birt-Friesen, V.L., and S.A. Macko. 1990. Energy 

expenditures, activity budgets and prey harvest of breeding Common Murres. 

Stud. Avian Biol. 14:84-92. 

Croll, D.A., A.J. Gaston, A.E. Burger, and D. Konnoff. 1992. Foraging behavior and 

physiological adaptation for diving in Thick-billed Murres. Ecology 73: 344-356. 

Decker, M.B., G.L. Hunt, Jr., and G.V. Byrd. 1994. The relationship between seasurface temperature, the abundance of juvenile walleye pollock (Theragra 

chalcogramma), and the reproductive performance and diets of seabirds at the 

Pribilof Islands, in the southeastern Bering Sea. Pp. 425-437 in Climate change 

and northern fish populations (Beamish, R.J., ed.). Can. Spec. Publ. Fish . Aqua. 

Sci. 

Gaston, A.J., D.G. Noble, and M.A. Purdy. 1983. Monitoring breeding biology 

parameters for murres Uria spp.: Levels of accuracy and sources of bias. Journal 

of Field Ornithology 54:275-282. 

Goss-Custard, J.D. 1970. The responses of redshank (Tringa totanus (L.)) to spatial 

variations in the density of their prey. J. Anim. Ecol. 39:91- 1 13. 

Goudie, R.I., and J.F. Piatt. 1991. Body size and foraging behaviour in birds. 

Proceedings of the 20th International Ornithological Congress, 2-9 Dec., 1990, 

Christchurch, New Zealand, Vol. 2: 8 1 1 -8 1 6. 

Hamer, K.C., R. W. Fumess, and R. W .G. Caldow. 199 1. The effects of changes in 

food availability on the breeding ecology of great skuas Catharacta skua in 

Shetland. J. Zool. Lond. 223: 175-1 88. 

Hamer, K.C., P. Monaghan, J.D. Uttley, P. Walton and M.D. Burns. 1994. The 

influence of food supply on the breeding ecology of Kittiwakes Rissa tridactyla in 

Shetland. Ibis 135: 

Harris, M.P., and S. Wanless. 1988. The breeding biology of guillemots Uria aalge on 

the Isle of May over a six year period. Ibis 130: 172-192. 

Hassell, M.P. and R.M. May. 1974. Aggregation of predators and insect parasites and 

its effect on stability. J. Anim. Ecol. 43567-594. 

Hatch, S.A., and J.F. Piatt. 1995. Seabirds in Alaska. Pp. 49-52 in Our Living 

Resources: A report to the Nation (LaRoe, E.T., Fams, G.S., Puckett, C.E., 

Doran, P.D., and Mac, M.J., Eds.). U.S. Dept. of the Interior, National Biological 

Service, Washington, D.C. 530 pp. 
Hatch, S.A., G.V. Byrd, D.B. Irons, and G.L. Hunt. 1993. Status and ecology of 

kittiwakes (Rissa tridactyla and R. brevirostris) in the North Pacific. Pages 140- 

153 in K. Vermeer, K.T. Briggs, K.H. Morgan, and D. Siegel-Causey, editors, 

The Status, Ecology, and Conservation of Marine Birds of the North Pacific. 

Special Publication, Canadian Wildife Service, Ottawa. 

Hatch, S.A., B.D. Roberts, and B.S. Fadely. 1993. Adult survival of Black-legged 

Kittiwakes Rissa tridactyla in a Pacific colony. Ibis 135: 247-254. 

Hayes, D.L. 1995. Recovery monitoring of pigeon guillemot populations in Prince William 

Sound, Alaska. Final Report for Exxon Valdez oil spill restoration project 94173.71 

PP. 

Hobson, K.A., J.F. Piatt, and J. Pitocchelli. 1994. Using stable isotopes to determine 

seabird trophic relationships. J. Anim. Ecol. 63:786-798. 

Holling, C.S. 1959. The components of predation as revealed by a study of small 

mammal predation of the European pine sawfly. Can. Entomol. 9 1 :293-320. 

Hunt, G.L., J.F. Piatt, and K.E. Erikstad. 1991. How do foraging seabirds sample their 

environment? Proceedings of the 20th International Ornithological Congress, 2-9 

Dec., 1990, Christchurch, New Zealand, Vol. 4:2272-2279. 

Hunt, G.L., N.M. Harrison, and J.F. Piatt. 1993. Aspects of the pelagic biology of 

planktivorous auklets. Pages 39-55 in K. Vermeer, K.T. Briggs, K.H. Morgan, 

and D. Siegel-Causey (eds.), The Status, Ecology and Conservation of Marine 

Birds in the North Pacific", Canadian Wildlife Service Special Publication, 

Ottawa. 

Manuwal, D.A. 1980. Breeding biology of seabirds on the Barren Islands, Alaska, 

1976- 1979. Unpubl. Rep., U.S. Fish and Wildlife Service, Office of Biological 

Services, Anchorage, Alaska. 195 pp. 

Merrick, R.L., T.R. Loughlin, and D.G. Calkins. 1987. Decline in abundance of the 

northern sea lion, Eumetopias jubatus, in Alaska, 1956-86. Fishery Bulletin 

85:35 1-365. 

Methven, D.A. and J.F. Piatt. 1989. Importance of capelin (Mallotus villosus) in the 

summer diet of cod (Gadus Morhua) at Witless Bay, Newfoundland. Journal 

Conseil Exploration de la Ma 45:223-225. 

Methven, D.A. and J.F. Piatt. 1991. Seasonal abundance and vertical distribution of 

capelin (Mallotus villosus) in relation to water temperature at a coastal site off 

eastern Newfoundland. ICES Journal of Marine Science 48: 187- 193. 

Monaghan, P., J.D. Uttley, M. Bums, C. Thane, and J. Blackwood. 1989. The 

relationship between food supply, reproductive effort, and breeding success in 

Arctic Terns Sterna paradisea. Journal of Animal Ecology 58:261-274. 

Monaghan, P. P. Walton, S. Wanless, J.D. Uttley, and M.D. Bums. 1994. Effects of 

prey abundance on the foraging behaviour, diving efficiency and time allocation of 

breeding Guillemots Uria aalge. Ibis 136:2 14-222. 

Montevecchi, W.A. and J. Piatt. 1984. Composition and energy contents of mature 

inshore spawning capelin (Mallotus villosus): implications for seabird predators. 

Comparative Biochemistry and Physiology 78A(1): 15-20. 
Montevecchi, W.A. and J.F. Piatt. 1987. Dehydration of seabird prey during transport 

to the colony: Effects on wet weight energy densities. Can. J. Zool. 

65:2822-2824. 

Murdoch, W.W. and A. Oaten. 1975. Predation and population stability. Adv. Ecol. 

Res. 9:l-125. 

Nettleship, D.N. 1991. The diet of Atlantic Puffin chicks in Newfoundland before and 

after the initiation of an international capelin fishery, 1967-1984. Proceedings of 

the 20th International Ornithological Congress, 2-9 Dec., 1990, Christchurch, 

New Zealand, Vol. 4: 2263-227 1. 

Piatt, J.F. 1987. Behavioural Ecology of Common Murre and Atlantic Puffin Predation 

on Capelin: Implications for Population Biology. Ph.D. Thesis, Department of 

Biology, Memorial University of Newfoundland, St. John's, Nfld. 3 1 1 pp. 

Piatt, J.F. 1990. Aggregative response of Common Murres and Atlantic Puffins to 

their prey. Studies in Avian Biology 14:36-5 1. 

Piatt, J.F. 1994. Oceanic, shelf, and coastal seabird assemblages at the mouth of a 

tidally-mixed estuary (Cook Met, Alaska). OCS Study MMS 93-0072, Final Rep. 

for Minerals Management Service, Anchorage, Alaska. 

Piatt, J.F., and D.A. Methven. 1992. Threshold foraging behavior of baleen whales. 

Marine Ecology Progress Series 84:205-210. 

Piatt, J.F. and D.N. Nettleship. 1985. Diving depths of four alcids. Auk 102: 293-297. 

Piatt, J.F., and P. J. Anderson. 1996. Response of Common Murres to the Exxon 

Valdez oil spill and long-term changes in the Gulf of Alaska marine ecosystem. 

Pp. 720-737 in: Exxon Valdez Oil Spill Symposium Proceedings. Rice, S. D., R. 

B. Spies, D. A. Wolfe and B. A. Wright (Eds). American Fisheries Society 

Symposium 18, Bethesda, Maryland. 

Piatt, J.F. and N.L. Naslund. 1995. Abundance, distribution and population status of 

Marbled Murrelets in Alaska. Pp. 285-294 in: Ralph, C.J., G. Hunt, M. Raphael, 

and J.F. Piatt (Eds.). Ecology and Conservation of the Marbled Murrelet. General 

Technical Report PSW-GTR-152. Albany, CA: Pacific Southwest Research 

Station, Forest Service, U.S. Department of Agriculture. 420 pp. 

Piatt, J.F., J.L. Wells, A. MacCharles, and B. Fadely. 1990a. The distribution of 

seabirds and their prey in relation to ocean currents in the southeastern Chukchi 

Sea. Canadian Wildlife Service Occasional Papers 68:2 1-3 1. 

Piatt, J.F., B.D. Roberts, and S.A. Hatch. 1990b. Colony attendance and population 

monitoring of Least and Crested Auklets on St. Lawrence Island, Alaska. Condor 

92: 109-1 16. 

Piatt, J.F., C.J. Lensink, W. Butler, M. Kendziorek, and D. Nysewander. 1990~. 

Immediate impact of the Exxon Valdez oil spill on marine birds. Auk 107:3 87- 

397. 

Piatt, J.F., D.A. Methven, A.E. Burger, R.L. McLagan, V. Mercer, and E. Creelman. 

1989. Baleen whales and their prey in a subarctic coastal environment. Canadian 

Journal of Zoology 67: 1523- 1530. 

Prichard, A. 1997. Evaluation of pigeon guillemots as bioindicators of nearshore 

ecosystem health. Master's thesis. University of Alaska, Fairbanks. 
Roby, D.D., J.L. Ryder, G. Blundell, K.R. Turco, and A. Prichard. 1996. Diet 

composition, reproductive energetics, and productivity of seabirds damaged by the 

Exxon Valdez oil spill. Annual report for Exxon Valdez oil spill restoration Project 

95 1636.36 pp. 

Roseneau, D.G., A.B. Kettle, and G.V. Byrd. 1994. Results of the Common Murre 

restoration monitoring project in the Barren Islands, Alaska, 1993. Project No. 

93049 Final Report to the EVOS Trustees Council, USFWS, Homer, Alaska. 93 

PP. 

Royer, T.C. 1993. High-latitude oceanic variability associated with the 1 8.6-year nodal 

tide. Journal of Geophysical Research 98:4639-4644. 

Safina, C. and J. Burger. 1985. Common tern foraging: seasonal trends in prey fish 

densities and competition with bluefish. Ecology 66: 1457-1463. 

Safina, C. and J. Burger. 1988. Prey dynamics and the breeding phenology of common 

terns (Sterna hirundo). Auk 105:720-726. 

Schneider, D.C. 1989. Identifjmg the spatial scale of density-dependent interaction of 

predators with schooling fish in the southern Labrador Current. J. Fish. Biol. 35: 

109-1 15. 

Schneider, D. and J.F. Piatt. 1986. Scale-dependant aggregation and correlation of 

seabirds with fish in a coastal environment. Marine Ecology Progress Series 

32:237-246. 

Schneider, D.C., and D.A. Methven. 1988. Response of capelin to wind-induced 

thermal events in the southern Labrador Current. J. Mar. Res. 46: 105-1 18. 

Schneider, D.C., R. Pierotti, and W. Threlfall. 1990. Alcid patchiness and flight 

direction near a colony in eastern Newfoundland. Stud. Avian Biol. 14:23-35. 

Slater, L., J.W. Nelson, and J. Ingrum. 1994. Monitoring studies of lower Cook Inlet 

seabird colonies in 1993 and 1994. U.S. Fish and Wildl. Serv. Rep., AMNWR 

94/17. Homer, AK. 43 pp. 

Springer, A.M. 1992. A review: Walleye pollock in the North Pacific- how much 

difference do they really make? Fisheries Oceanogr. 1 :SO-96. 

Sydeman, W. J. 1993. Survivorship of common murres on southeast Farallon Island, 

California. Ornis Scandinavica 24: 135- 14 1. 

Uttley, J.D., P. Walton, P. Monaghan, and G. Austin. 1994. The effects of food 

abundance on breeding performance and adult time budgets of Guillemots Uria 

aalge. Ibis 136:205-213. 

Wanless, S., D.D. French, M.P. Hams, and D.R. Langslow. 1982. Detection of annual 

changes in the numbers of cliff-nesting seabirds in Orkney 1976-80. Journal of 

Animal Ecology 5 1:785-795. 

Wanless, S., J.A. Moms, and M.P. Harris. 1988. Diving behaviour of Guillemot Uria 

aalge, puffin Fratercula arctica and Razorbill Alca torda as shown by radio 

telemetry. J. Zool. Lond. 216:73-81. 

Wanless, S., M.P. Hams, and J.A. Moms. 1991. Foraging range and feeding locations of 

Shags Phalacrocorax aristotelis during chick rearing. Ibis 133 :30-36. 
Chapter 2. Oceanography of lower Cook Inlet 

Gary Drew and John Piatt 

Introduction 

Cook Inlet is a broad (ca. 50- 100 km) and shallow (mostly <50m) tidal estuary that 

extends 350 km northeastward from the Gulf of Alaska (GOA) continental shelf (Fig. 

2.1). Primary and secondary production in lower Cook Inlet is extraordinarily high 

(Larrance et al. 1977) and, in turn, this productivity supports large commercial and sport 

fisheries, thriving marine mammal populations, and some of the largest seabird colonies 

in the northern GOA. Indeed, more seabirds breed and forage in lower Cook Inlet than 

may be found along the entire northeast gulf coast, including Prince William Sound (Piatt 

1994). This high productivity is in large part a function of the local oceanography and a 

consequence of persistent upwelling of cold, nutrient-rich gulf waters into the lower 

estuary (Muench et al. 1978). 

Because of this link between oceanography, forage fish and seabirds, we collected some 

basic oceanographic data on an opportunistic basis as well as on some transects designed 

specifically for the purpose of examining water mass characteristics in lower Cook Inlet. 

In this chapter, we present a summary of our findings and a selection of data to illustrate 

main points. We plan to publish these main findings on oceanography in peer-reviewed 

journals. In the meantime, oceanographic data collected during this project are being used 

primarily to characterize habitats used by fish and seabirds, and to help explain temporal 

and spatial variability in abundance of fish and seabirds in lower Cook Inlet (for example, 

see Robards et al. 1999,2002; Piatt et al. 1999; Abookire et al. 2000,2001,2002). All 

oceanographic data collected on the project have been archived and are available for 

analysis by other investigators. 

Background 

There have been few dedicated studies of oceanography in lower Cook Inlet, and most 

work was conducted during the 1970s (Burbank 1977, Larrance et al. 1977, Muench et al. 

1978, Schumacher and Reed 1980). Additional information may be found in works on 

the northern GOA that included some research in lower Cook Inlet (e.g., Royer 1981, 

1982, Xiong and Royer 1985, Reed and Schumacher 1986). These few resources are 

adequate to draw a picture of the important oceanographic processes affecting lower 

Cook Inlet. 

At a coarse scale, Cook Inlet can be viewed as a large inland extension of the continental 

shelf in the northern Gulf of Alaska (Fig. 2.2). The ocean floor rises fiom about 5000m 

to 200m at the shelf break. At this spatial scale, there is little variation in bathymetry on 

the relatively wide (up to 200 km) continental shelf. The shelf break defines the northerly 

extent of a counterclockwise rotating subarctic gyre that is responsible for westerly 

offshore currents (Reed and Schumacher 1986). Offshore water circulation is dominated 

by the Alaska Current (Alaska Stream) which generally flows parallel to the continental 
slope. Although the Stream may affect inshore circulation, coastal features seem to be 

separate, or at least different, than those offshore (Reed and Schumacher 1986). 

Closer to the mainland, the Alaska Coastal Current (ACC) drives inshore currents on the 

continental shelf (Royer 198 1). The ACC is primarily a density driven current that 

reaches peak velocity in the fall coinciding with maximum freshwater runoff from rivers 

along the gulf coast (Royer 1981, Royer 1982). Winds are also thought to be important 

in constraining the flow of the ACC in a narrow stream and in producing coastal 

convergence (Reed and Schumacher 1986). 

The persistent, westward-flowing ACC is thought to be the primary factor responsible for 

summer-long upwelling in lower Cook Inlet (Muench et al. 1978). As the ACC enters 

lower Cook Inlet, it first must squeeze through Kennedy and Stevenson entrances, and 

then is pushed up onto the relatively shallow estuary shelf at the mouth of the inlet, and 

onto shallow shelves around the Barren islands and along the Kenai Penisinsula (Fig. 

2.3). Within Cook Inlet itself there is a complex circulatory pattern (Fig. 2.3). In general, 

there is an inflow of mixed ACC water on the east side, and an outflow of less saline, 

warm and turbid water along the west side of the inlet. These water masses are separated 

by a distinct "mid-channel rip" (Burbank 1977). The extent of the northern intrusion of 

seawater on the east side appears to be a hction of tidal mixing (Burbank 1977). Most 

of the water entering Cook Inlet on the east side traverses the inlet and is carried back out 

on the west side. 

In this chapter, we will present some results of oceanographic investigations in lower 

Cook Inlet from 1995 to 1999, and compare our findings with those of previous studies. 

More extensive datasets are summarized in Appendices 2.1-2.2 1. 

Sea Surface Temperature 

Images of sea-surface-temperature (SST) were developed using data from advanced very 

high-resolution radiometer (AVHRR) sensors aboard NOAA Polar Orbiting Satellites. 

We have archived hundreds of "good" (relatively cloud-free) images from all years of our 

study. For this report, we selected the best single images available in the month of July 

during the years 1995- 1999. This period coincided with our annual seabird and foragefish sampling cruise. Raw AVHRR data was calibrated and georeferenced at the Alaska 

Science Center and then added to a geographic information system (GIs) for Cook Inlet. 

We originally used the multichannel sea surface temperature (MCSST) algorithm on the 

data, but results suggested some electronic contamination in channel 5. Consequently, 

we used surface temperatures derived solely from channel 4. 

Water Profrles 

We collected temperature and salinity data during the summers of 1995- 1999 using a 

Seabird Electronics SBE 19 SEACAT Conductivity, Temperature and Depth (CTD) 

recorder. Density was calculated from temperature and salinity. Prior to data collection in 

1998, we modified our CTD by adding a fluorometer (to measure phytoplankton standing 
crop; Wet Labs Inc., Wetstar) and a turbidity sensor (to measure sediments in the water; 

D&A Instrument Co., OBS-3). Therefore, all CTD casts conducted in 1998 and 1999 

included data fiom the additional sensors (see Chapter 3). Several hundred CTD profiles 

were collected in conjunction with mid water trawls (Chapter 4) and on several crossinlet transects (Fig 2.4). These transects were located near seabird colonies to 

characterize local marine habitats and they were sampled once annually (1995-1999). In 

addition, repeated samples were taken at three stations (Fig 2.4), Station Z (1 995- 1996), 

Eldred Passage (1 997- 1999), and Inner Bay (1 998- 1999) in order to investigate withinyear variability in water characteristics and primary production. 

Temperature Loggers 

One or two temperature data loggers (Onset Electronics StowAway and TidbiT) were 

placed 3-10m below the low tide line near each of the 3 colonies, Chisik Island (Snug 

Harbor), Gull Island (Kachemak Bay) and East Arnatuli Island (Barren Islands). The 

loggers were programmed to collect data at regular time intervals (varying hm 1 to 15 

minutes), and data were averaged by day for analyses presented here. These loggers were 

placed at each of the study sites in order to provide general information on the timing and 

magnitude of annual temperature cycles (see Appendix 2.22). Additionally, several 

loggers were placed near spawning sites to provide temperature data during spawning of 

sandlance, and a pair of loggers was placed at 10m and lOOm near Hesketh Island to 

describe the annual cycle of stratification and mixing in Kachemak Bay. 

Other Data 

We compiled data on water temperatures fiom two other sources. Continuously-recorded 

sea surface temperature data were obtained fiom a monitoring station situated in Seldovia 

Harbor, situated a few km hm our sampling station at Eldred Passage on the south side 

of Kachemak Bay (Fig. 2.4). Temperatures have been recorded year-round at this site 

since 1964, and since 1994, temperature data were collected every hour, 365 days a year. 

For more information on this data, go to the NOAA web site: http:Nco-ovs.nos.noaa.g~v 

and find ancillary observations for station 9455500. We also compiled data hm the 

GAKl station off the south Kenai Peninsula (near Seward) in the Gulf of Alaska, where 

vertical profiles of sea temperature and salinity fiom the surface to 250 m have been 

taken regularly since 1971. Both temperature and salinity data can be downloaded fiom 

the University of Alaska web site: http://www.ims.uaf.edu:8000/gakl. 

Results and Discussion 

Geographic Variability in Sea Surface Temperature 

Sea surface temperature imagery (Figs. 2.5-2.9) confirms the important elements of 

oceanography that have been described fiom in situ measurements. On their westward 

approach to the entrance of Cook Inlet, waters south of the Kenai Peninsula tend to be 

stratified with relatively warm water at the surface. These warm surface wate- evident 

in most AVHRR images taken during summer- along with our water profiles in 

Kennedy Entrance (see following section) and historical data hm the existing Gulf of 

Alaska CTD line (GAK 1 ; Xiong and Royer 1984) suggest that an extensive low-salinity 
lens may overlay more oceanic waters over the northern GOA shelf during summer 

months. As these waters approach the relatively shallow underwater land bridge 

connecting the Kenai Peninsula with the Barren Islands and the Kodiak Archipelago (Fig. 

2.3), cooler waters are upwelled and mixed (Reed and Schumacher 1986). More 

extensive mixing and cooling of surface layers occurs as the current enters lower Cook 

Inlet and pushes water up onto the shallow estuary shelf (Figs. 2.5-2.9). 

Transport of this cold, upwelled water into lower Cook Inlet- described in some detail 

by all previous investigators (Burbank 1977, Muench et al. 1978, Reed and Schumacher 

1986 j can be clearly seen in all years moving up the east side of the inlet fiom 

Kennedy entrance to as much as 50 km north of Kachemak Bay. We observed this 

pattern in all AVHRR images taken at all times of year, although the east-west and northsouth extent of the cold-water plume varied with tide state and time of year. Coastal 

divergence or upwelling is also clearly evident along the tip of the Kenai Peninsula and 

around the Chugach Islands (Burbank 1977). Similar coastal upwelling is usually 

observed around the Barren Islands, and along the northeast coast of Shuyak Island in the 

Kodiak Archipelago. As noted by Burbank (1 977), upwelled surface waters appear to 

bypass middle and inner Kachemak Bay, which remains stratified during summer. 

Satellite images support the drogue studies of Burbank (1977) which suggested that the 

majority of westward transport of northward flowing waters to the western side of Cook 

Inlet occurs just north of Kachemak Bay. The limit of seawater intrusion into the inlet 

appears to be just south of Kalgin Island. 

AVHRR images also confirm Burbank's (1977) conclusions about oceanography on the 

west side of the inlet. Water in the upper inlet is warm and weakly stratified during 

summer owing to the large volume of freshwater entering the upper reaches of Cook Inlet 

(e.g., from the Matanuska, Susitina, and Kenai rivers). This warm, low-salinity water 

flows southward (Fig. 2.3) until it meets the northward-moving cold plume, where all 

waters are pushed to the western side of the inlet and continue to flow southward into 

Karnishak Bay and then eventually around Cape Douglas and into Shelikof Strait. The 

boundary between cool, inflowing water and warm, outflowing waters is best seen in Fig. 

2.7, and this boundary is always marked by a "mid-channel rip" where these water 

masses converge and where seaweed, logs and debris are gathered at the surface in 

extensive rip lines (Burbank 1977). This convergence is strongest during flood tide as the 

northward intrusion of clear and partially mixed seawater tends to wedge itself between 

the less dense water west of the mid-channel, and less-dense coastal water that flows 

north from Kachemak Bay (e.g., Fig. 2.7). 

Surface temperatures were generally warmer in 1997 and 1998 (Figs. 2.5-2.9; note that 

all AVHRR images were constructed with the same temperature scale). Temperatures in 

these years were influenced by the 1997-1998 El NinoISouthern Oscillation (ENSO) 

event, the strongest ENS0 event on record. The warm sea surface temperature anomalies 

(SSTA) in the GOA during the spring and summer of 1997 were partly related to 

concurrent large-scale atmospheric anomalies (Lau 1997). The principal processes 

involved in producing the warm SSTA were enhanced warm-air advection and insolation 

as revealed by the anomalous distributions of low-level temperature, geopotential height, 
relative humidity, and cloud cover (Overland et al. 1999). Warming in winter 1997- 1 998 

was likely due to heat propagation by Kelvin waves, and anomalously warm temperatures 

were observed in the GOA not only at the surface, but throughout the water column 

(Royer and Weingartner 1999). It is not clear whether residual effects of this heating 

account for the warm surface temperatures observed in Cook Inlet during summer of 

1998. 

Vertical Temperature and Salinity Profiles 

AVHRR imagery provides a useful tool for describing the oceanography of Cook Inlet, 

but subsurface features can only be inferred hm satellite images of surface layers. 

Vertical CTD profiles of the water column allow us to fully characterize water masses 

and marine habitats in Cook Inlet. From 1995 through 1999,856 CTD casts were 

conducted in Cook Inlet (Fig. 2.10). Here we present only results from 3 cross-inlet 

transects to examine spatial variation in water characteristics, and from one station in 

Kachemak Bay to examine seasonal variation. Complete sets of spatial and temporal 

profiles from all permanent stations and years and can be found in Appendices 2.1-2.2 1. 

Our 3 cross-inlet transects (A,B, and C; Fig. 2.4) were similar in location to transects 

described in Burbank (1977) that crossed the inlet just south of Chisik Island ("line 30", 

Fig. 98 in Burbank 1977), westward hm Kachemak Bay ("line 20"), and a dog-leg 

transect from the Kenai Peninsula to the Barren Islands and across to Cape Douglas ("line 

00"). CTD data collected during fishing trawls is being analyzed separately with respect 

to fish distributions (e.g., Abookire et al. 2000). 

Again, our results corroborate findings of previous studies (Burbank 1977, Muench et al. 

1978, Reed and Schumacher 1986) and conclusions made hm AVHRR images. Cold, 

high-salinity water enters lower Cook Inlet around the Barren Islands and is generally 

mixed or weakly stratified at this point (Transect A, Figs. 2.12 and 2.13). This cold, 

mixed plume extends northward through (Transect B) and past (Transect C) outer 

Kachemak Bay, becoming a narrow tongue at its northern extent. Waters on the west side 

of Cook Inlet are weakly stratified, and surface temperatures are 1-2 C warmer than to the 

east- as revealed in AVHRR images (above). However, CTD profiles reveal the full 

extent of differences between east and west, as the entire water column in the west is 

much warmer and much less saline than waters to the east, especially off Kachemak Bay 

and further north. Furthermore, the convergent front ("mid-channel rip") separating the 

east and west water masses is prominently situate& as the name suggests- in the 

middle of Cook Inlet. As noted by Burbank (1977), the higher density GOA water can be 

seen (particularly in Fig. 2.12) to slide beneath the lower density west-inlet water at the 

convergent front. 

We examined inter-annual variability in temperatures at depth from profiles (Fig. 2.13) 

across Kennedy Entrance (Transect C)(Inter-annual variability on other transects can be 

seen in Appendices 2.1 - 2.9). As discussed above, water temperatures were anomalously 

high in 1997 and 1998. Warm water was mostly near the surface in 1997, and profiles 

from 1998 indicated that water below 50rn was approximately 1-2 degrees C warmer in 

1998 than in any other year. These results are consistent with observations elsewhere 

that surface layers in the North Pacific were affected by ENS0 in 1997 through 

atmospheric coupling ("tele-connection effect"), whereas the entire water column was 
affected by ENS0 through transport effects in winter of 1997- 1998 (Overland et al. 1999, 

Royer and Weingartner 1999). In some years, a surface lens of relatively warm, fresh 

water was seen to overlay colder, more saline GOA water. We believe that this occurred 

sporadically as remnants of stratified GOA water entered Kennedy Entrance (e.g., see 

Fig. 2.7) and before it was thoroughly mixed by turbulent upwelling. Except for very 

nearshore, we never observed stratification in mixed GOA waters north of the Barren 

Islands on transects A or B, (Appendices 2.1 to 2.9). 

Temporal Variability in Temperature and Stratification 

Sites in Kachemak Bay that were sampled with a CTD repeatedly during summer, Station 

Z (1995- 1996), Eldred Passage (1 997- 1999) and Inner Bay (1 998- 1999), exhibited 

similar seasonal patterns in warming and stratification (Appendices 2.15-2.21). We 

conducted more CTD casts at Eldred Passage than anywhere else, and we use these 

results to illustrate that Kachemak Bay usually remained well mixed until mid- to late 

May (Julian date 1 5 1 = May 3 1) when waters became thermally stratified (Fig. 2.15). 

Waters remained stratified until mid- to late September (Julian date 258 = September 15), 

which was usually beyond the time we conducted CTD casts in Kachemak Bay. 

However, continuously recording temperature loggers placed near the surface and bottom 

at Hesketh Island (near Eldred Passage) clearly indicated when thermal stratification 

began and ended in Kachemak Bay (Fig. 2.16). When near-surface (10 m) and bottom 

(>80m) temperatures were the same, then the water column must have been completely 

mixed and uniform from top to bottom. When stratification developed, then surface and 

bottom temperatures diverged, usually by about 2-4 degrees C (Fig. 2.16). It is evident, 

therefore, that mixing events (presumably storms) in late August and September, 1997, 

nearly eliminated stratification several times until about October 15 (Julian date 288), 

after which waters remained mixed for the duration of fall, winter and spring. 

Unfortunately, the surface temperature logger failed in summer 1998 so we cannot assess 

when stratification developed again in the bay. However, we can see (Fig. 2.16) that 

mixing and permanent loss of stratification occurred earlier in 1998 than in 1997, i.e., 

around the first week of September. Waters remained well-mixed throughout fall, winter 

and spring, and thermal stratification developed rapidly again around June 20 (Julian date 

171); evident also from the vertical CTD profiles (Fig. 2.1 5). 

Continuously recording temperature loggers that were placed at our 3 main study sites 

(Gull, Chisik and Barren islands) corroborated our findings fiom AVHRR imagery and 

CTD profiles. Surface temperatures near Chisik Island (Snug Harbor) were about 1-2 

degrees C higher than temperatures at Gull Island throughout summer (Fig. 2.17). In turn, 

temperatures at Gull Island were often more than 1-2 degrees higher than temperature at 

the Barren islands. Surface temperatures were least variable on a day-to-day basis at 

Chis&, presumably because shallow waters there are relatively well-mixed by tides and 

less influenced by intrusions of cold Gulf water that occur on the east side. At Gull 

Island, surface temperatures were more variable throughout summer (Julian date 160 - 

250 corresponds to June 9 - September 6) than those at Chisik, presumably because of 

frequent wind-mixing of surface stratification, complex circulation in the bay and 

variable amounts of freshwater outflow that would all tend to modify the composition 

and mixing of surface layers in the bay (Burbank 1977). At the Barren Islands, surface 
temperatures were very consistent on a day-to-day basis until about mid-July, when they 

became highly variable. Erratic temperature fluctuations after that time may have been 

related to the-appearance and break-up of warm stratified surface layers around the 

Barrens (e.g., contrast the location of warm surface layer near Barrens in Fig. 2.7 with 

more distant warm layer in Fig. 2.9). 

Data collected at the NOAA tide monitoring station in Seldovia (Fig. 2.18) corroborate 

our data from temperature loggers in Kachemak Bay, and allow us to examine annual 

temperature cycles throughout the duration of our study. The seasonal pattern of 

warming and cooling was remarkably similar among years and as indicated in logger 

data as well (Fig. 2.17j mean summer (Jun-Aug) temperatures at Seldovia varied little 

(Fig. 2.18A). However, the unusually warm winter (FebApr) of 1998 and cool winter 

(Feb-Mar) of 1999 are evident in the Seldovia time series (Fig. 2.18B). 

Over a larger time scale (197 1- 1999) it appears that our study was conducted during a 

warm phase in the Gulf of Alaska (Fig. 2.19). Water temperatures in the Gulf of Alaska 

have been anomalously warm since the late 1970s, following a marked climatic and 

biological regime shift that occurred in association with changes in location and strength 

of the Aleutian low pressure system (Anderson and Piatt 1999). Temperatures in surface 

layers of the Gulf (GAKI) do not reveal the shift as well as deeper waters (Fig. 2.19). 

This is because surface layers in the GOA south of the Kenai peninsula are often strongly 

stratified with a warm, low-salinity surface layer (e.g., Figs. 2.7-2.9) and temperatures 

may be influenced as much by freshwater runoff, winds and insolation (Royer 1981, 

1982) as they are by long-term changes in temperature of the Alaska Coastal Current 

(ACC). In contrast, bottom temperatures at GAKl clearly indicate long-term temperature 

trends in the ACC (Royer and Weingartner 1999). Because stratification of GOA water is 

broken down by turbulent mixing at the entrance to Cook Inlet, surface water 

temperatures in Kachemak Bay in general, and Seldovia in particular, seem to reflect 

temperatures in deep GOA waters during both summer and winter (Fig. 2.19). 

Conditions during our study (1 995- 1999) were closer to average than those observed for 

much of the 1980s, with exception of the 1997-1998 ENOS event, which elevated both 

surface and bottom water temperatures in the Gulf and in Seldovia (Fig. 2.19). 

Conclusions 

The physical oceanography of lower Cook Inlet is largely defined by five features: 1) 

bathymetry of the shallow estuary basin, 2) extreme semi-diurnal tidal oscillations, 3) a 

persistent current (ACC) that enters Cook Inlet on the east side and pushes cold, saline 

GOA waters up onto the shallow estuary shelf, 3) a persistent outflow of relatively warm, 

low salinity water along the west side, and, 4) a persistent convergent front between these 

water masses in mid-channel. Cook Inlet has the second highest tidal fluctuations in 

North America, and strong tides can affect rates of current flow, the degree of penetration 

of upwelled water, and the location and strength of the convergent front (Burbank 1977). 

Currents in the lower inlet are strongly influenced by constraints of bathymetry and the 

persistent coastal current. These factors result in upwelling of nutrient-rich GOA waters 

that is highly predictable in time and space. In turn; this supports high levels of primary 
productivity and standing stocks of fish, seabirds and marine mammals (as documented 

in the following Chapters). 

In general, our 3 main study areas could be clearly distinguished fiom each other because 

of the persistent oceanographic features that defined them. Annual variability within each 

area was relatively small compared to the oceanographic differences between them. We 

observed an extreme annual perturbation in the form of the 1997- 1998 ENSO, which was 

the strongest on record (Overland et al. 1999). Although effects of ENS0 are greatly 

attenuated by the time they reach high latitudes of Alaska, we documented some clear 

changes in oceanography and biology (Piatt et al. 1999, and following chapters in this 

report). The warm surface waters that we observed in Cook Inlet during 1997 appeared 

to be the result of an atmospheric tele-connection with the tropics, rather than a direct 

effect of the ENS- which was just developing in the central Pacific at that time (Lau 

1997, Overland et al. 1999). Effects included a decrease in wind stress and surface 

mixing, reduced cloud cover and increased insolation; all of which served to increase 

temperatures at the surface by several degrees (Overland 1999). Although the highest 

sea-surface temperatures anomalies were observed in 1997, the greatest impact of the 

1997-1998 ENS0 was felt in Alaska during the winter of 1997-1998 and spring of 1998 

when water temperatures were anomalously hi+ not just at the surface, but throughout 

the entire water column. Changes to ACC water in the GOA were some of the most 

extreme on record (Royer and Weingartner 1999). The impact of this ENS0 on forage 

fish and marine birds in Cook Met will be documented more fully in future peerreviewed publications. In this report, our main focus is on the regional differences in 

biology among study sites that resulted fiom differences in underlying oceanography. 

Literature Cited 

Abookire, A.A., J.F. Piatt and M. Robards. 2000. The influence of meso-scale 

thermohaline differences on near shore fish distributions in Kachemak Bay, 

Alaska. Estuarine and Coastal Shelf Sci. 5 1 : 45-59. 

Abookire, A.A., J.F. Piatt, and B.L. Norcross. 2001. Summer habitat of juvenile 

groundfishes in Kachemak Bay, Alaska. Alaska Fish. Res. Bull. 8(1): 45-56. 

Abookire, A.A., J.F. Piatt, and S. Speckman. 2002. Distribution of mid-water fish 

communities in relation to oceanographic features in lower Cook Inlet, Alaska. 

Submitted to Marine Ecology Progress Series. 

Anderson, P.J., and J.F. Piatt. 1999. Community reorganization in the Gulf of Alaska 

following ocean climate regime shift. Mar. Ecol. Prog. Ser. 189: 1 17- 123. 

Burbank, D. C. 1977 Circulation studies in Kachemak Bay and lower Cook Inlet. Vol. 3 

in Environmental Studies of Kachemak Bay and Lower Cook Inlet (Trasky, L. L., 

Flag, L. B. and Burbank, D. C., eds). Alaska Department of Fish and Game, 

Anchorage, Alaska. 207pp. 

Lau, N. C. 1997. Interactions between Interactions Between Global SST Anomalies and 

the Midlatitude Atmospheric Circulation. Bull. Arner. Meteor. Soc. 78: 21-33. 

Muench, R. D., H. 0. Mofjeld, and R. L. Charnell. 1978. Oceanographic conditions in 

lower Cook Inlet: Spring and summer 1973. J. Geophys. Res. 83C: 5090-5098. 
Overland, J.E., N.A. Bond, and J.M. Adams. 1999. Atmospheric anomalies in 1997: 

Links to ENSO? Proceedings Of The 1998 Science Board Symposium On The 

Impacts Of The 1997198 El Niiio Event On The North Pacific Ocean And Its 

Marginal Seas. PICES Scientific Report No. 10: 7-1 1. 

Piatt, J.F. 1994. Oceanic, shelf, and coastal seabird assemblages at the mouth of a tidallymixed estuary (Cook Inlet, Alaska). OCS Study MMS-93-0072, Final Rep. for 

Minerals Management Service, Anchorage, Alaska. 

Piatt, J.F., G. Drew, T.Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711998 ENS0 event in lower Cook Inlet, 

Alaska. Proceedings Of The 1998 Science Board Symposium On The Impacts Of 

The 1997198 El Niiio Event On The North Pacific Ocean And Its Marginal Seas. 

PICES Scientific Report No. 10: 93- 100. 

Reed, K. R. and J. D. Schumacher. 1986. Physical Oceanography. Pp. 57-76 in The 

Gulf of Alaska: Physical environment and biological resources (Hood, D. W. and 

Zimrnerman, S.T., eds). National Oceanic and Atmospheric Administration, 

Minerals Management Service OCS Study MMS 860095. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fish. Bull. 

97: 962-977. 

Robards, M.D., G.A. Rose, and J.F. Piatt. 2002. Growth and abundance of Pacific sand 

lance, Ammodytes hexapterus, under differing oceanographic regimes. Env. Biol. 

Fishes. In press. 

Royer, T. C., 198 1. Baroclinic transport in the Gulf of Alaska. Part I1 Fresh water driven 

coastal current. J. Mar. Res. 39: 251-266 

Royer, T. C. 1982. Coastal fresh water discharge in the northeast Pacific. J. Geophys. 

Res. 87C: 20 17-202 1. 

Royer, T.C., and T. Weingartner. 1999. Coastal hydrographic responses in the northern 

Gulf of Alaska to the 1997-98 ENS0 event. Proceedings Of The 1998 Science 

Board Symposium On The Impacts Of The 1997198 El Niiio Event On The North 

Pacific Ocean And Its Marginal Seas. PICES Scientific Report No. 10: 77-8 1. 

Schumacher, J.D. and R.K. Reed. 1980. Coastal flow in the northwest Gulf of Alaska: 

the Kenai Current. J. Geophys. Res. 85: 6680-6688. 

Smith, W. H. F., and D. T. Sandwell . 1997. Global Sea Floor Topography from 

Satellite Altimetry and Ship Depth Soundings. Science 277: 1956-1962. 

Xiong, Q. and T.C. Royer. 1984. Coastal temperature and salinity in the northern Gulf of 

Alaska, J. Geophys. Res. 89: 8061-8066. 
Chapter 3. Primary and Secondary Production in lower Cook Inlet 

Gary Drew 

Introduction 

Cook Inlet is one of the most productive marine areas in Alaska (Sambrotto and Lorenzen 

1986). Little is known about factors influencing primary and secondary production 

there-- or of linkages with higher trophic-level forage fish and seabirds. Whereas the 

main objective of our research in Cook Inlet was to study functional relationships 

between seabirds and forage fish, we managed to collect ancillary (not directly funded) 

data on primary and secondary production in later years of the project. Sufficient data 

were collected to describe some spatial and temporal patterns of primary and secondary 

productio* neither of which has been well-documented in lower Cook Inlet. Here we 

present some preliminary findings of this research with minimal discussion. Results will 

be written up later for publication in peer-reviewed journals (lower priority than bird and 

fish papers). 

Most of the information on primary and secondary productivity in Cook Inlet comes fiom 

research conducted during the 1970s as part of the Outer Continental Shelf 

Environmental Assessment Program (OCSEAP). From these studies, we know that 

primary productivity in lower Cook Inlet peaks in spring (April-May) but remains high in 

outer Kachemak Bay throughout summer (Larrance and Chester 1979) owing to a 

continuous re-supply of nutrients by persistent upwelling in Lower Cook Inlet (Winant 

and Olson 1976, Larrance et al. 1977). Indeed, production in lower Cook Inlet is often > 

lg c/m2/d throughout summer, yielding annual production levels in excess of 300 g 

c/m21y (Sambrotto and Lorensen 1986). These are high levels of production for an inner 

shelf, and match or exceed values associated with upwelling regions of the Bering Sea 

and California Current (Springer and McRoy 1992). Spring and summer populations are 

dominated by diatoms and microflagellates, with chrysophytes, dinoflagellates and green 

algae appearing less fiequently and in much lower abundance (Larrance et al. 1977). 

There is a transition in phytoplankton species fiom west to east across the inlet and a 

seasonal succession of species as well (Larrance et al. 1977). Phytoplankton standing 

stocks are probably grazed heavily by zooplankton carried in to lower Cook Inlet by the 

Alaska Coastal Current (ACC) (Sambrotto and Lorensen 1986). 

There is a diverse zooplankton community in lower Cook Inlet. Cross-shelf Ekman flow 

of oceanic Alaska Stream water and meander of the Alaska StrearnIACC results in 

zooplankton communities with both coastal and oceanic origins (Damkaer 1977, Cooney 

1986). Cooney (1984) calculated that zooplankton of oceanic origin may account for as 

much as 83% of all zooplankton in shelf and coastal regions of the GOA. The persistent 

counterclockwise motion of both the ACC and the Alaska Stream assures that species 

composition is similar in most coastal areas of the northern Gulf of Alaska (GOA) 

(Cooney 1986). Some of the highest standing stocks of zooplankton in the GOA are 

found in Cook Inlet during spring and summer, following the spring phytoplankton 
bloom. Peak densities in excess of 1000 mg/m3 are not unusual. The high biomass of 

zooplankton in the northern GOA is important directly as a food source for higher trophic 

level animals, and indirectly as a food source for larval fishes that, in turn, become prey 

(Vogel and McMurray 1986). 

In this study, we did not have the funding or resources to mount a full-scale study of 

primary and secondary production in Cook Inlet. However, with minimal additional 

effort, we were able to sample widely distributed stations for phytoplankton and 

zooplankton during the course of trawl surveys for forage fish. We also sampled some 

fixed stations. Our main objective was to assess spatial variation in phytoplankton and 

zooplankton standing stocks in lower Cook Inlet; ultimately to better understand factors 

influencing the distribution of seabirds and forage fish. A secondary objective was to 

assess seasonal variability in phytoplankton and zooplankton standing stocks, and relate 

this to environmental features (winds, stratification, upwelling, nutrients). 

Phytoplankton 

Phytoplankton concentrations were measured two ways: by measuring chlorophyll 

pigment in samples collected directly fiom filtered water and by using a chlorophyll 

pigment sensor attached to a conductivity-temperature-depth (CTD) recorder. Direct 

collections were made in 1997 at the Eldred Passage station and on the Cook Inlet 

Transect (Fig 3.1). Eldred Passage and Inner Bay stations were sampled using a CTDmounted sensor throughout the summers of 1998 and 1999 at approximately one-week 

intervals. The Cross Inlet transect was sampled once each summer, in July of 1997, 1998 

and 1999, using a CTD-mounted sensor. 

For collections, we used a Niskin bottle to obtain water samples at the surface, 5 m, 10 m, 

25 m, and 50 m. Water samples were filtered for coarse debris and a one-liter sample 

was stored in blacked-out nalgene bottles for later filtration. Within a few hours, samples 

were subjected to vacuum filtration in a darkened room to isolate phytoplankton from the 

sample. Filter disks were frozen and sent to the University of Alaska-Fairbanks for 

analysis. Samples fiom the Cook Inlet Transect were treated similarly, except that we 

collected only fiom 10 m depths at each station, and samples were cooled in ice until they 

could be filtered. Samples fiom 1998 were analyzed for phytoplankton chlorophyll 

concentrations by Peter McRoy at the University of Alaska-Fairbanks WAF). A lack of 

dedicated funds precluded analysis of samples fiom subsequent years. 

We validated results obtained using the fluorometer with results obtained from sample 

collections (above) at Eldred Passage during 1998. As the fluorometer proved an 

accurate and convenient tool for measuring phytoplankton abundance, we used it 

exclusively for that purpose in 1999. We used a WETStar fluorometer (WET Labs Inc.) 

attached to our SBE 19 CTD Profiler (Seabird Electronics Inc.). Flurometry data was 

downloaded from the CTD with other data from the profiler. 
Nutrients 

Water samples for nutrient analyses were collected throughout the summer of 1997 at the 

Eldred Passage station and along the Cross Inlet Transect in June (Fig. 3.1). Nutrient 

samples were also collected from the Eldred Passage and Inner Bay stations in 1998 and 

1999. After filtering out phytoplankton hm water samples (above), a 50 ml subsample 

was extracted fiom the water sample, labeled and frozen for future analysis. Samples 

from 1997 were analyzed for total nitrates, ammonia, silicates and phosphates by Peter 

McRoy at the University of Alaska-Fairbanks (UAF). A lack of dedicated funds 

precluded analysis of samples hm subsequent years. 

Zooplankton 

We began collecting zooplankton in 1997. Samples were collected opportunistically at 

most mid-water trawl stations (see Chapter 4), seasonally at Eldred Passage and Inner 

Bay stations, and at all stations occupied during CTD transects across portions of Cook 

Inlet (Fig 3.1). Eldred Passage was sampled throughout the summers of 1997- 1999. The 

Inner Bay station was sampled throughout the summers of 1998- 1999. The Cross Inlet 

transect was sampled once each summer, in July of 1997, 1998 and 1999. The transect 

was lengthened slightly in 1998. This is the only transect that provides us with 

simultaneously-collected data on spatial variation in oceanography, nutrients, 

phytoplankton and zooplankton. 

Zooplankton were collected using a plankton ring net with a 60 cm diameter mouth 

opening. The net was 3 m long and had a mesh size of 333 pm. Tows were all conducted 

vertically, from a depth of 50 m in most instances, or fiom 5 m off the bottom where the 

bottom was <50m deep. Samples were rinsed out of collection buckets with a minimum 

of seawater and then fixed with a 1 to 1 mix of 10% formalin, yielding a final fonnalin 

concentration of 5%. Settled volumes were measured on all samples at the Alaska 

Science Center. More recently, zooplankton samples have been analyzed for species 

composition and abundance. However, results of this work are not yet completed. 

Results and Discussion 

Phytoplankton biomass varied among years and areas, but with such a short time series, 

we can draw few conclusions from these data. One consistent feature, however, was the 

lack of phytoplankton biomass in the western half of lower Cook Inlet (Figs. 3.2). 

Standing stocks of phytoplankton were highest in stratified waters (Chap. 2 and 

Appendices) of outer Kachemak Bay in most years, although high production was 

observed in mixed waters off Kachemak Bay in 1998 (Fig. 3.3). These results are 

consistent with previous observations of Larrance and Chester (1979). The west side of 

the inlet is relatively depauperate in phytoplankton owing to high sediment loads in the 

water (see also Appendices 2.7-2.9) that prevent light from penetrating surface layers, 

thereby severely limiting phytoplankton productivity (Larrance et al. 1977). Analyses of 

water samples collected on our cross-inlet transect of 27 June, 1997, confirmed the crossinlet pattern of phytoplankton distribution observed with the fluorometer and 

demonstrated that low concentrations of phytoplankton on the west side were not due to 

nutrient depletion (Fig. 3.4). 
As demonstrated in time-series data from two stations in Kachemak Bay, phytoplankton 

production began in late April to early May (Fig. 3.4). Peak blooms were generally early 

in the season, though substantial levels of phytoplankton biomass were present until the 

end of August in 1998. Following stratification in early June (see Chapter 2 and 

Appendices 2.17-2.21), most production occurred in the upper 30m of the water column 

(Fig. 3.4). There were multiple peaks in phytoplankton biomass over the summer, 

presumably after nutrient supplies were replenished following storm-induced mixing of 

the water column. We collected data on nutrient concentrations in 1997 at Eldred Passage 

(Fig. 3.6), but unfortunately the corresponding phytoplankton samples were lost. 

Nonetheless, these data indicate that significant depletion of nutrients occurs in surface 

layers at Eldred Passage during summer, particularly nitrates and silicate. Alternatively, 

differences in the timing of various phytoplankton species blooms may also have been a 

factor. 

More than 200 zooplankton samples were collected throughout lower Cook Inlet at each 

fish trawl station (Chapter 4), on CTD transects and at fixed stations in Kachemak Bay 

(Fig. 3.5). Zooplankton standing stocks were generally highest in stratified waters of 

outer Kachemak Bay (Fig. 3 -5) in all years. In 1998, however, zooplankton biomass was 

exceptionally high in the area of cold-water upwelling outside Kachemak Bay; coinciding 

with the high measurements of chlorophyll-a made on the same transect (Fig. 3.8). 

Zooplankton biomass was similarly correlated spatially with phytoplankton biomass on 

the cross-inlet transect in 1997 and 1999 (compare Fig. 3.8 with Fig. 3.3). 

Zooplankton standing stocks varied seasonally also, exhibiting peaks in biomass hm 

mid-May to mid-June (Fig. 3.9). Zooplankton biomass grew quickly and peaked at about 

the same time that phytoplankton biomass was peaking in stratified waters of Kachemak 

Bay (Fig. 3.5). Zooplankton biomass at Eldred Passage and Inner Bay stations exhibited 

similar patterns in abundance within each season (Fig. 3.5). 

In summary, our findings corroborate those of Larrance et al. (1977) from 20 years 

earlier. The key to initiation of a phytoplankton bloom in lower Cook Inlet is 

stratification of the water column. In addition, water transparency must be adequate to 

permit 1% of the light incident to the surface to penetrate deeper than about 10m 

(Larrance et al. 1977)- a constraint that severely limits phytoplankton production on the 

west side of Cook Inlet. As summer progresses and stratification Wer develops in 

Kachemak Bay, nutrient depletion begins to limit phytoplankton production. 

Phytoplankton blooms may occur repeatedly during summer following storms or 

advection of nutrient-rich surface waters into Kachemak Bay (Larrance et al. 1977). 

Outside of Kachemak, but still east of the mid-channel rip (Chapter 2), mixing and water 

exchange are more frequent. This results in high nutrient loads all summer and allows for 

potential blooms to occur at any time in mixed waters, such as we observed in July of 

1998. In turn, persistently high levels of phytoplankton production support a large 

standing stock of zooplankton in lower Cook Inlet during spring and summer (Cooney 

1986). The areal distribution of zooplankton also reflected that of phytoplankton with 

high standing stocks in mixed waters on the east side, and a generally low biomass in 
waters west of the mid-channel rip. We have not completed our analysis of zooplankton 

species composition and biomass. Final results will be available by April of 2002, and we 

expect to compile and publish our findings within a year or two after that time. 

Peter McRoy (University of Alaska, UAF) provided us with the protocols and equipment 

for collection of water and phytoplankton samples. Analyses for nutrient and chlorophyll 

concentrations were also conducted in his laboratory at UAF. We would like to 

acknowledge the capable assistance of Greg Snedgen (Captain, RN David Grey) and 

crews of the Alaska Dept. of Fish and Game vessel RN Pandalus. At one time or 

another, all members of the project assisted in data collection, however, in particular we 

would like to thank Martin Robards, Dave Black, Alisa Abookire, and Suzan Speclanan 

for their time and attention to detail. 

Literature Cited 

Cooney, R.T. and K. Coyle. 1982. Trophic implications of cross-shelf copepod 

distributions in the southeastern Bering Sea. Mar. Biol. 70: 187-196. 

Cooney, R. T. 1984. Some thoughts on the Alaska Coastal current as a feeding habitat 

for juvenal salmon. Pp. 256-268 in The influence of ocean conditions on the 

production of salmonids in the North Pacific (W.C. Percy, ed). Sea Grant Program, 

ORESU- W-83-00 1, Oregon State University, Corvallis, OR. 

Cooney, R. T. 1986. Zooplankton. Pp. 285-303 in The Gulf of Alaska: Physical 

environment and biological resources. @.W. Hood and S.T. Zirnrnerman, eds). 

National Oceanic and Atmospheric Administration, Minerals Management Service 

OCS Study MMS 860095. 

Damkaer, D. M. 1977. Initial zooplankton investigations in Prince William Sound, Gulf 

of Alaska, and lower Cook Inlet. Env. Assess. Alaska Cont. Shelf, Reports of 

Principal Investigators, 1977, 10: 137-274. 

Larrance, J. D., and A. J. Chester. 1979. Source, composition and flux of organic 

detritus in lower Cook Inlet. Outer Cont. Shelf Env. Assess. Prog., Final Reports of 

Principal Investigators 46: 1-7 1. 

Larrance, J. D., D. A. Tennant, AJ. Chester, and P.A. Ruflio. 1977. Phytoplankton and 

primary productivity in the northeast Gulf of Alaska and lower Cook Inlet: Final 

report. Env. Assess. Alaska Cont. Shelf, Reports of Principal Investigators, 1977, 

10: 1-136. 

Muench, R. D., H. 0. Mofjeld, and R. L. Charnell. 1978. Oceanagraphic conditions in 

lower Cook Inlet: Spring and summer 1973. J. Geophys. Res. 83C: 5090-5098. 

Sambrotto, R. N. and C. J. Lorenzen 1986. Phytoplankton and primary productivity. Pp. 

249-282 in The Gulf of Alaska: Physical environment and biological resources. 

(Hood, D. W. and Zimrnerman, S.T., eds). NOAA, Minerals Manage. Sew. OCS 

Study MMS 860095. 
Smith, S.L. and J. Vidal. 1984. Spatial and temporal effects of salinity, temperature and 

chlorophyll on the communities of zooplankton in the southeastern Bering Sea. J. 

Mar. Res. 42: 221-257. 

Springer, A.M., C.P. McRoy, and K.R. Turco. 1989. The paradox of pelagic food webs in 

the northern Bering Sea - 11. Zooplankton communities. Cont. Shelf Res. 9: 359-386. 

Springer, A. M. and C.P. McRoy. 1993. The paradox of pelagic food webs in the northern 

Bering Sea- 111. Patterns of primary production. Cont. Shelf Res. 13: 575-599. 

Vogel, A. H., and G. McMurry. 1986. Seasonal population density distribution of 

copepods, euphosiids, arnphipods, and other holoplankton on the Kodiak Shelf. 

Outer Cont. Shelf Env. Assess. Prog., Final Reports of Principal Investigators 46: 

423-659. 

Winant, C. D., and J. R. Olson. 1976. The vertical structure of coastal currents. Deep 

Sea Res. 23:925-936. 
Chapter 4. Abundance and Distribution of Pelagic Forage Fish in Cook Inlet 

Alisa Abookire and John Piatt 

Introduction 

We undertook a study of forage fish primarily because of their ecological role in 

supporting populations of marine birds at our three study colonies in lower Cook Inlet. 

We wanted to know where fish were concentrated in lower Cook Inlet and which species 

were most common. The term "forage fish" is generally applied to abundant, schooling 

fishes that serve as prey for a variety of marine mammals, seabirds and larger fishes. The 

most abundant forage fishes in the Gulf of Alaska are Pacific sand lance (Ammodytes 

hexaptem), capelin (Mallotus villosus), eulachon (Thaleichthys pacificus), Pacific 

herring (Clupea pallasi), juvenile walleye pollock (Theragra chalcogramma) and 

lanternfishes (Myctophidae)(Springer and Speckman 1997). Most of these fishes occupy 

pelagic habitats and are best sampled with mid-water trawl nets. We therefore used a 

modified herring trawl to collect forage fish around our three study colonies. These 

samples provided us with information on the distribution, relative abundance and species 

composition of fish schools in the study area, and served to corroborate hydro-acoustic 

data on fish abundance (Chapter 7). In addition, trawl collections were subsampled to 

assess the size-class of fishes available to predators. 

Forage fish populations undergo fluctuations in abundance at a variety of temporal and 

spatial scales (Bechtol 1997, Anderson and Piatt 1999). Most pelagic forage fish have 

relatively short life spans. Populations are prone to fluctuate rapidly owing to early 

maturation, high fecundity, high rates of predation and sensitivity to habitat degradation 

(Anderson and Piatt 1999). Irrespective of changes in abundance, populations may also 

shift their distributions with short- and long-term changes in the marine environment 

(Cushing 1995). While we know how some species are distributed with respect to 

environmental gradients (e.g., Swartzman et al. 1992, 1994), little is known about habitat 

preferences of forage fish in Alaska. Species that are sensitive to environmental 

perturbation include Pacific herring and capelin because both have relatively specialized 

intertidal or shallow subtidal spawning sites (Meyer 1997). Whether due to direct effects 

of oil, or other environmental factors that predate the Exxon Valdez oil spill in 1989, a 

reduction in abundance of fatty forage fishes is believed to be limiting the recovery of 

seabirds in the Gulf of Alaska (Piatt and Anderson 1996). When we initiated our study, 

however, it was not clear which forage fish species were commonly available to seabirds 

in the Gulf of Alaska. 

Therefore, some primary objectives of this study were to: 1) measure the relative 

abundance of forage fishes within foraging range of seabirds at three colonies in lower 

Cook Inlet, 2) assess the species composition of forage fish schools in each of the three 

study areas, and, 3) assess the spatial distribution (both vertical and horizontal) of the 

common forage fish species in each area, and relate distribution to environmental 

characteristics. This report provides preliminary results that address each of these 
objectives. We will continue to analyze trawl data in the future, including statistical 

evaluation of temporal and spatial patterns of abundance, and of relationships between 

forage fish and their habitats. We plan to publish several peer-reviewed papers on the 

ecology of forage fish in lower Cook Inlet in addition to papers already completed that 

have used these trawl data (Robards et al. 1999b, Abookire et al. 2002). 

Methods 

Fish collections 

We conducted 241 mid-water trawls in lower Cook Inlet during the summers of 1996- 

1999. Trawling was concentrated within a 45 km foraging range of three seabird 

colonies in lower Cook Inlet: the Barren Islands, Gull Island in Kachemak Bay, and 

Chisik Island (Fig. 4.1). Trawls (n=213) were done in conjunction with systematic 

hydro-acoustic surveys of forage fish around each seabird colony (see Chapter 7, and Fig. 

7.5 for details on survey tracks) and were conducted during July 16-25, 1996; July 19 - 

August 2, 1997; July 2 1 -August 9, 1998; and July 25 - August 1 1, 1999. On these 

surveys, we trawled only where significant sign of fish biomass was noted with the 

hydro-acoustic echosounder. Fish abundance was recorded with a Biosonics DT4000 

echosounder using a 120 kHz transducer. Acquisition threshold was set at -70 dB. 

When a significant fish sign was detected on the echosounder we drove over the entire 

signal and then returned to the location where the signal began and towed a mid-water 

trawl through the hydroacoustic signal. We fished some or all of the acoustic signal, 

depending on strength of targets while fishing. Of the 2 13 trawls on acoustic sign, only 

159 were considered "good" trawls, suitable for interspecies and interannual comparisons 

of catch-per-unit-effort and percent composition. In addition, we conducted 23 trawls in 

Kachemak Bay and near Chisik Island on 20-25 June, 1997. These extra trawl data, and 

"poor" trawls fiom above, are used here only for the purpose of examining species 

distributions, and not for interannual comparisons. 

We fished fiom the RN Pandalus, a 22 meter stem trawler. The mid-water trawl was a 

modified herring trawl with a 30 foot-wide mouth and a 118'' cod-end liner with a plastic 

1000 pm mesh collecting bucket. Tow duration varied among years. In 1996, the 

average tow duration was 25 minutes. In order to catch more single-species schools and 

to better coordinate hydroacoustic signal with catch, we decreased the tow duration to 15 

minutes in 1997 and 10 minutes in 1998 and 1999. A transducer was mounted on the 

headrope and used at all times to determine the depth of the net. A Temperature Depth 

Recorder (TDR, Wildlife computers model # MK7) was mounted on the headrope and 

used during every tow to determine the exact depth of the net while fishing (Appendix 

4.1). Tow start and end time and location were recorded with a Global Positioning 

System unit when trawl doors were at the water surface. Each tow was flagged as good 

(G), questionable (Q), or bad (B) based on efficiency of gear and presumed success in 

catching the acoustic target. In some case* such as around Chisik Islam- we trawled 

areas with little or no acoustic sign. Catch-per-unit-effort (CPUE) was calculated as the 

number of fish captured per 1000 m trawled (for CPUE of all species, see Appendices 

4.2-4.4). Distance of trawl was determined from GPS readings of position taken at the 

start and end of the trawl. 
Fish measurements 

All fishes were identified, counted, and fork length was measured (to the nearest 1 mm) 

with an electronic Limnoterra Fish Measuring Board (FMB). If >I00 individuals of the 

same species were captured in a single tow, a random subsample of 50 to 100 was 

measured. After each tow, the total weight of all fish comprising each species was 

measured with a Pesola scale aboard ship. Individual fish weights were taken in a variety 

of ways. In 1996 no fish were weighed. In 1997 individual fish weights were taken 

aboard the ship with Pesola scales. In 1998 and 1999, at least 30 individual fish per sizeclass of each species were frozen and weighed on land (after thawing) with an Ohaus 

electronic scale. 

For each study area, 50 fish specimens of each species and size-class were archived 

(hzen individually in whirl-pak bags) for later use in seabird feeding studies or analysis 

of fish energetics, stable isotopes, or genetics. Larval fishes were preserved in 5% 

fonnalin for possible further identification. Beginning in 1997, jellyfish, euphausids, and 

shrimps were weighed and squids were counted (Appendix 4.5). Euphausids and squid 

were also frozen for energetics and fixed in 5% fonnalin for identification. 

Statistical analyses of fish data 

Shannon-Wiener Index of Diversity (Krebs 1989) and species richness (the total number 

of species) were calculated for mid-water trawl data by year and area. Length-frequency 

histograms and length-weight regressions were calculated for the following common 

species: Pacific sand lance, Pacific herring, walleye pollock, capelin, Pacific cod (Gadus 

macrocephalus), longfin smelt (Spirinchus thaleichthys), pink salmon (Oncorhynchus 

gorbuscha), and Pacific sandfish (Trichodon trichodon). These species were chosen 

because each one comprised at least 5% of the species composition in one area-year (see 

Table 4.2). Length-frequency histograms were binned into 5 mm fork-length intervals, 

using data combined from all areas and years. Log(1ength) versus log(weight) linear 

regressions were calculated for the common species above (Appendix 4.6). 

Results 

Relative abundance 

A total of 266,446 fish were captured in 159 "good" tows. There was an order of 

magnitude difference in relative catch rates of forage fishes among the three areas. 

Overall CPUE was highest at the Barren Islands (3264 f 1018 fish/lan), moderate in 

Kachemak Bay (1 180 f 373 fish/lan) and lowest near Chisik Island (238 f 78 fish). 

In general, this pattern of relative catches among areas was consistent among years (Fig. 

4.2), except in 1999 when CPUE was similar at the Barrens and Kachernak Bay. The high 

CPUE observed at the Barrens was due mostly to high catches of sand lance recorded 

near the Kenai Peninsula (inside of the Chugach Islands) rather than to catches in open 

waters around the Barrens. Indeed, variability in catch of sand lance among years 

accounted for most (?=0.94) of the variation in total CPUE among years (Table 4.1). 
Catch composition 

Sand lance were the most common (71%) forage fish caught in rnid-water trawls in lower 

Cook Inlet. While they were occasionally superceded in importance by other species in 

some years, they comprised the highest proportion of catches over all years combined, 

and in all three study areas Pigure 4.3). Other abundant fishes in the Cook Inlet study 

area were Pacific herring (18%), walleye pollock (8%) and capelin (2%). In general, 

differences in catches among the three colony areas persisted among years. Fish schools 

in the Barrens sampling area often consisted of single-species aggregations; for example 

pollock or capelin offshore and sand lance or hemng nearshore. Similarly, catches in 

Kachemak Bay were often dominated by one or two species (especially sand lance). In 

contrast, we rarely recorded single-species fish catches near Chisik Island. Mid-water 

catches near Chisik were usually small, and, while they were often dominated by one 

species (e.g., sand. lance, pollock), they usually also included many other species such as 

capelin, longfin smelt, salrnonids, pricklebacks (Lumpenus spp.), larval flatfishes 

(Pleuronectidae), and pacific lamprey (Lampetra tridentatus). Chisik exhibited the 

highest species richness, with more than twice as many species caught there than at the 

Barrens. Species diversity was also highest at Chisik (Table 4.2). 

Fish size 

Most species captured in the mid-water trawl were "forage size" (i.e., defined by us as 

fish smaller than 200 mm in length because they are suitable for eating by seabirds). The 

majority of walleye pollock, Pacific cod, and other gadoids captured in lower Cook Inlet 

had fork lengths 400 mm, with uni-modal size distributions representing only young-ofthe-year (YOY) age-classes (Figure 4.4). Similarly, we caught only YOY salmon. 

Walleye pollock with lengths >200 mm (n=3 13, up to 61 6 rnm in length) were captured 

almost exclusively in Kachemak Bay. Three size classes of herring were captured (Figure 

4.4) that corresponded to different age-classes (Stokesbury et al. 1999): young-of-theyear (size < 80 mm), one-year olds (ca. 80-150 mm) and older adults (150-20W mm). 

The largest hemng captured were 255 mm in length. Most adult herring were captured in 

Kachemak Bay; only one was captured near Chisik and none at the Barrens. Sand. lance 

captured in trawls included mostly y-o-y (<90 rnrn), but also some one-year-old (I+, ca. 

90-130 mm), 2+ (ca. 125-145 mm) and older age-classes (Robards et al. 1999a,c). 

Capelin and longfin smelt size-frequencies were bimodal, suggesting mostly YOY and 

1+ age-classes, as well as a few older fish. Pacific sandfish are relatively slow-growing, 

and catches included a few aged 1-2 (<lo0 mm), but mostly fish aged 3-6 years (Paul et 

al. 1997). The largest sand fish caught was 232 mm in length. Length-weight regressions 

for all common species (areas and years combined) are provided in Appendix 4.6. 

Distribution 

In order to assess patterns of vertical distribution we examined depths at which fish were 

caught, using data combined over all years and areas. Highest catches of sand lance, 

juvenile herring, eulachon and longfin smelt were recorded in surface waters less than 40 

m in depth (Fig. 4.5). There were occasional catches at 40-80 meters involving 1000s of 

sand lance. Non-juvenile forage-size herring (80-200 mm, see Fig. 4.4) were most 

abundant at depths of 40 to 50 m. Walleye pollock and capelin were distributed 
throughout the water-column, but largest catches were concentrated at depths greater than 

40 m. Similarly, juvenile Pacific cod were caught at all depths, but were most abundant 

at depths less than 40 m. 

To assess the geographic distribution of species, we plotted CPLE of all common fishes 

at each station we trawled in lower Cook Inlet. The highest CPUEs for all species 

combined were associated with the cold core upwelling area (see Chapter 2) between the 

Barrens and outer Kachernak Bay and with coastal areas of the Kenai Peninsula, 

including the shores of Kachemak Bay (Fig. 4.6). Species were segregated into different 

geographic areas. Sand lance and herring tended to concentrate in coastal areas and in the 

northern part of the study area (Fig. 4.6). Pollock and capelin were more abundant 

offshore and in the southern part of the study area (Fig. 4.6). Other common taxa showed 

a distinct preference for either Kachemak Bay or Chisik Island waters (Fig. 4.7-4.9). 

Jellyfish were widely abundant in the cold core area (Fig. 4.9). 

Conclusions 

Abundance and species composition of forage fish schools differed among the three study 

areas of lower Cook Inlet. Fish were an order of magnitude more abundant around the 

Barren Islands and in Kachemak Bay than they were around Chisik Island. However, 

CPUE data must be interpreted cautiously because trawl locations were not random; they 

were selected on the basis of having exceptionally strong acoustic targets. While we 

believe that the inter-area comparisons of relative abundance are probably of correct 

magnitude and direction, we have less confidence that inter-annual variability within each 

study area reflected real temporal trends. Temporal fluctuations were best measured on 

hydro-acoustic surveys (Chapter 7). 

Catches at the Barrens were typically dominated by one species of forage fish; usually 

sand lance or juvenile herring near the coast, and juvenile pollock offshore. Species 

richness was lowest at the Barrens. In contrast, waters around Chisik typically contained 

small, mixed-species schools of fish and this was reflected in high species richness and 

diversity of catches. Kachemak Bay was more moderate in its abundance and diversity of 

species. Spatial patterns in the mid-water forage fish community of Cook Inlet mirror 

those found in the near-shore fish community (Robards et al. 1999b), presumably for the 

same reason. Productivity of phytoplankton, zooplankto- and apparently fis& is 

enhanced in eastern lower Cook Inlet by upwelling of nutrient-rich Alaska Coastal 

Current waters into the lower inlet and outer Kachemak Bay (Chapters 2, 3). 

Sand lance abundance in lower Cook Inlet increased dramatically in 1998 and high 

catches were sustained in 1999. We speculate that this have been related to the El NiiioSouthern Oscillation (ENSO) event of 1997- 1998. Effects of the ENS0 were felt most 

strongly in Cook Inlet during the winter (late January through April) of 1998, when SSTs 

were as much as 1-2 " C warmer than normal (see Chapter 2). Sand lance spawn in 

October and larvae hatch by late December (Robards et al., 1999~). Therefore, the 

warmer ENS0 waters in winter 1998 may have enhanced sand lance growth and survival 

during winter, and subsequent abundance during the following summer. We have begun 
to consider the biological impacts of the 1997- 1998 ENS0 in lower Cook Inlet (Piatt et 

al. 1999) and plan to explore the data further to assess impacts of the ENS0 event on fish 

growth, recruitment and community composition. 

Differences among forage fish species in their vertical distribution in the water column 

and proximity to different seabird colonies should have important consequences for 

seabirds. In particular, sand lance is most abundant near the surface and occurs in close 

proximity to Gull Island in Kachemak Bay, and to a lesser extent in proximity to seabirds 

hm the Barrens (if they fly to the Kenai Peninsula). In contrast, pollock and capelin are 

found most often at depths greater than 30 m, and in abundance just north of the Barrens. 

We examine how adult seabird diets and meals delivered to chicks reflect this regional 

pattern of forage fish availability in Chapters 9, 10, and 14. Presumably, inter-species 

differences in vertical and inlet-wide distribution of forage fishes reflect differences in 

habitat choice among species. In future publications, we will be looking at how different 

species are distributed with respect to environmental variables such as temperature, 

salinity, bottom depth, distance to shore, zooplankton biomass, etc. (e.g., Swartzman et 

al. 1992, 1994; Abookire et al. 2000,2002). 

We are grateful to David Black, Gary Drew, Jared Figurski, Cliff Lascink, Becka 

Seymour and Suzann Speckman for assistance with fish collections. We thank captains 

Paul Desjardins and Mark Hottman, and crew of the ADF&G vessel R/V Pandalus: Brad 

Hanis, Rick Gustin, Mike Pamsh and Eric Hofseth. We thank the Alaska Department of 

Fish and Game (Comm. Fish. Div.) and Alaska Maritime National Wildlife Refuge 

(USFWS) for logistic support in Homer. 

Literature Cited 

Abookire, A.A., J.F. Piatt and M. Robards. 2000. The influence of meso-scale 

thermohaline differences on near shore fish distributions in Kachernak Bay, 

Alaska. Estuarine and Coastal Shelf Science 5 1: 45-59. 

Abookire, A.A., J.F. Piatt, and S. Speckman. 2002. Distribution of mid-water fish 

communities in relation to oceanographic features in lower Cook Inlet, Alaska. In 

prep. for submission to Marine Ecology Progress Series. 

Anderson, P.J. and Piatt, J.F. 1999. Community reorganization in the Gulf of Alaska 

following ocean climate regime shift. Marine Ecology Progress Series. 

189(26): 1 17- 123. 

Bechtol, W.R. 1997. Changes in forage fish populations in Kachemak Bay, Alaska, 

1976- 1995. In Forage Fishes in Marine Ecosystems. Proceedings of the 

International Symposium on the Role of Forage Fishes in Marine Ecosystems. 

(C.W. Mecklenburg, ed.), p. 441 -456. 13- 16 Nov. 1996. Anchorage, Alaska. 

Alaska Sea Grant College Program Report No. 97-01. University of Alaska, 

Fairbanks, AK. 

Cushing, D.H. 1995. Population production and regulation in the sea: a fisheries 

perspective. Cambridge Univ. Press, Cambridge, England. 
Krebs, C.J. 1989. Ecological Methodology. Harper & Row, New York. 

Meyer, R.M. 1997. Forage fishes in marine ecosystems: Introduction to the symposium. 

Pp. 1-9 in Forage Fishes in Marine Ecosystems. Proceedings of the International 

Symposium on the Role of Forage Fishes in Marine Ecosystems, Alaska Sea 

Grant College Program Report No. 97-01. University of Alaska, Fairbanks, AK. 

Paul, J.M., A.J. Paul, T.J. Vogeler and J.P. Doyle. 1997. Biological investigations on 

Pacific Sandfish (Trichodon trichodon) in the Northern Gulf of Alaska. Pp. 87-94 

In Forage Fishes in Marine Ecosystems. Alaska Sea Grant College Program 

Report No. 97-01. University of Alaska, Fairbanks, AK. 

Piatt, J.F. and Anderson, P. 1996. Response of common murres to the Exxon Valdez oil 

spill and long-term changes in the Gulf of Alaska marine ecosystem. Am. Fish. 

SOC. Symp. 18:720-737. 

Piatt, J.F., G. Drew, T.Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711998 ENS0 event in lower Cook Inlet, 

Alaska. PICES Scientific Report No. 10: 93- 100. 

Robards, M.D., Anthony, J.A., Rose, G.A., and Piatt, J.F. 1999a. Changes in proximate 

composition and somatic energy content for Pacific sand lance (Ammodytes 

hexapterus) from Kachemak Bay, Alaska relative to maturity and season. Journal 

of Experimental Marine Biology and Ecology. 242:245-258. 

Robards, M.D., Piatt, J.F., Kettle, A.B., and Abookire, A.A. 1999b. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fish. Bull. 

97(4): 962-977. 

Robards, M.D., Piatt, J.F., and Rose, G.A. 1999c. Maturation, fecundity, and intertidal 

spawning of Pacific sand lance (Ammodytes hexapterus) in the northern Gulf of 

Alaska. J. Fish. Biol. 54: 1050- 1068. 

Springer, A.M. and Speckman, S.G. 1997. A forage fish is what" Summary of the 

symposium. In Forage Fishes in Marine Ecosystems. Proceedings of the 

International Symposium on the Role of Forage Fishes in Marine Ecosystems. 

(C.W. Mecklenburg, ed.), p. 773-805. 13-16 Nov. 1996. Anchorage, Alaska. 

Stokesbury, K. D. E., R. J. Foy, and B. L. Norcross. 1999. Spatial and temporal 

variability in juvenile Pacific herring, Clupea pallasi, growth in Prince William 

Sound, Alaska. Environ. Biol. Fish. 56: 40W18. 

Swartzman, G., C. Huang, and S. Kaluzny. 1992. Spatial analysis of Bering Sea 

groundfish survey data using generalized additive models. Can. J. Fish. Aqua. Sci. 

49: 1366-1378. 

Swartzman, G., W. Stuetzle, K. Kulman, and M. Powojowski. 1994. Relating the 

distribution of pollock schools in the Bering Sea to environmental factors. ICES J. 

Mar. Sci. 5 1 : 48 1-492. 
Chapter 5. Abundance and Distribution of Nearshore Fish in lower Cook Inlet 

Martin Robards, John Piatt and Arthur Kettle 

Introduction 

Inshore habitats are routinely used by a variety of small forage fish (e.g., capelin 

Mallotus villosus and sand lance Ammodytes hexapterus) both for spawning and feeding 

during summer. The near shore zone also serves as an important nursery area for 

juveniles of many large marine fish species (Poxton et al. 1983, Orsi and Landingham 

1985, Bennett 1989, Blaber et al. 1995, Dalley and Anderson 1997). Aside from the 

commercial importance of these large species (e.g., Pacific salmon [Oncorhynchus spp.], 

walleye pollock (Theragra chalcogramma), and herring [Clupea pallasi]), their juvenile 

age-classes can also serve as important forage for marine predators in Alaska. Declines in 

a variety of predator populations in the Gulf of Alaska have been linked to shifts in 

abundance and composition of forage fish stocks over the past 45 years (Francis et al. 

1998, Anderson and Piatt 1999). In order to examine the relationship between seabirds 

and forage fish more closely, we studied variability in abundance and composition of 

nearshore fish communities in areas used by breeding seabirds in lower Cook Inlet. 

Studies conducted elsewhere have shown that nearshore fish assemblages can change 

markedly over time (e.g., Horn 1980, Allen 1982, Nash and Gibson 1982, Nash 1988, 

Bennett 1989), but little was known about temporal or spatial variation of nearshore 

fishes in Alaska prior to our study. Therefore, one of our primary objectives was to 

assess variability in abundance, distribution and diversity of nearshore fish communities 

in three oceanographically distinct areas of lower Cook Inlet. Ultimately, we will use 

these data to assess prey availability to marine birds and to better understand factors 

influencing seabird population biology (e.g., Litzow et al. 2000,2002). Data collection in 

the first few years of study was also focused on the biology of sand lance (Robards et al. 

1999b,c, 2002), one of the single most important forage fish in northern oceans (Robards 

et al. 1999d). We have published some important results of our nearshore fish research, 

showing variability in nearshore fish communities over time-scales of decades, years, 

months and days (Robards et al. 1999a). Species composition and CPUE of seine catches 

also differed significantly with tides and time of day. Geographic differences in 

oceanography also influences the distribution and abundance of forage fish schools 

within lower Cook Inlet (Robards et al. 1999a), and at smaller spatial scales within 

Kachemak Bay (Abookire et al. 2000, submitted). 

In this report, we summarize some of the important results of our nearshore forage fish 

study; documenting the abundance, diversity and distribution of forage fish near shore in 

lower Cook Inlet. We will continue to analyze and publish results of our nearshore fish 

research, both for its importance in understanding nearshore fish ecology, and as vital 

background information to our studies of seabird foraging ecology in lower Cook Inlet. 
Study Sites and Habitats 

Kachemak Bay lies along the southeastern shore of Cook Inlet. The bay is 38 km wide at 

its entrance and 62 km long. The upper 6 km consists of mud flats that are exposed 

during low tide. Depths are relatively shallow, ranging fiom about 35 to 90 m, with some 

deeper areas (100 to 165 m) present off Gull Island along the south-central side of the 

bay. Water entering the bay originates fiom the Gulf of Alaska and is largely oceanic 

(Burbank 1977). Chisik Island, on the western side of Cook Inlet, is situated at the mouth 

of Tuxedni Bay and receives freshwater fiom local glacier-fed rivers. Water passing 

outside the island is also relatively fiesh because it receives significant glacier-fed input 

fiom large rivers at the head of Cook Inlet (Burbank 1977, Feely and Massoth 1982). 

Nearshore habitats around Chisik Island contain few sandy substrates and consist 

primarily of glacial silt and mud flats interspersed with mky substrates that are exposed 

at low tides. Near the entrance to Cook Inlet, the Barren Islands are in a transition zone 

between deep Gulf of Alaska waters and the shallow Cook Inlet estuary. The Alaska 

Coastal Current enters Cook Inlet north of the Barren Islands, leading to intense 

upwelling of cold, nutrient-rich waters onto the shallow southeastern Cook Inlet shelf 

(Burbank 1977). Because of the upwelling and strong tidal action, waters in this area are 

turbulent and well mixed. 

Field Collections 

We used beach seines to sample nearshore fish communities. These nets effectively and 

non-selectively sample shallow, inshore waters with sandy or smooth bottoms (Cailliet et 

al. 1986). Thirty meters of rope were attached to the ends of each net for deployment and 

retrieval. Nets were deployed from a small boat and set parallel to shore, about 25 m hm 

the beach as described by Cailliet et al. (1986). The net was then retrieved by hauling on 

both end ropes until the net was pulled ashore. Samples were collected about every two 

weeks in Kachemak Bay during May - September, and once per month throughout the 

winter of 1996 and 1997 (Table. 5.1). Samples from Chisik Island and the Barren Islands 

were collected every two weeks for the duration of their respective field seasons. To 

standardize comparisons among sites and years, we used data collected only between 1 

June and 3 1August in each year for analyses presented in this report. An archived beach 

seine database contains results of all other sets made in these three areas. 

We used slightly different beach seine nets among different locations and years due to 

ongoing design modifications andlor logistic constraints. While these differences 

undoubtedly introduced some variability in CPUE into our catch results, we believe that 

among-net differences in catch efficiency were small relative to among-site differences 

(but see below). All nets were basically the same, having: 1) a symmetric design with 

deepest vertical netting at the center and shallowest netting at the two ends, 2) a deeper, 

center panel of net with 3-6 mm stretched mesh, 3) two tapering wing panels with 6- 13 

mm stretched mesh on each side of the center panel. We used four different nets, and they 

differed mostly in their dimensions rather than design. In the following, we present in 

order for each net: Depth at center, depth where wings meet center panel, depth at end of 

wings, length of total net, length of wing panels, length of center panel, stretched mesh 
size of wing panels, stretched mesh size of center panel. Measurements of net dimensions 

varied slightly with when they were measured (at purchase, after use in field, among 

years) and by whom they were measured. The "Kachemak" (K) net (3.9m, 3.3m, 2.2m, 

44m, 14.7m, 14.7m, 6-13mm, 3mm) was longer and shallower than other nets, and had a 

small mesh (3mm) strip running along the entire bottom of the net. The "Puget Sound" 

(P) net was the most shallow (2.4m, 2m, lm, 37m, 18m, lm, 6mm, 3mm). The "Apex" 

(A) net was deeper in the middle and wings (5.4m, 4.4m, 1.5m, 35m, 13m, 9m, 6mm, 

3mm). The "Chisik" net (C) was of similar depth to A, but half the length of nets A or P 

(5.5m, 4.5m, 1.4m, 18m, 6.7m, 4.5m, 6mm, 3mm). 

Net "K" was used in Kachemak Bay in 1995-1999, and at Chisik in 1995. Net "P" was 

used at the Barrens in 1996 only, and net "A" was used there in 1997-1999. Net "A" was 

used at Chisik in 1996- 1997, and net "C" was used there in 1998-1999. In 1998, net "A" 

was used briefly in Kachemak Bay during late May through mid-June, allowing for 

comparison of catch efficiency with net "K", which was used on the same beaches within 

a few weeks. Excluding two sets with extreme high catches of herring or sand lance, we 

compared total catch and species richness of 26 sets using net "A" to 28 sets on the same 

beaches using net "K". Sets with "A" nets were conducted on 30 May and 11 June; sets 

with "K" nets were conducted on 13 and 26 June. Sets were usually repeated at high and 

low tide on the same day, and consecutive sets were often conducted at the same tide 

state to reduce site variance. A comparison of the average catch at 10 sites using the "A" 

net versus the "K" net showed that both nets caught similar quantities of fish ("K" catch 

= 0.72 ["A" catch]; 3 = 0.74; p<0.01). We can control for variable effects of tide state 

and use of single sets (see Robards et al. 1999a), and use only data fkom sites where 

duplicate data are available from a site at only one tide stage (low). This use of selected 

data (comparing 10 sets using net "K" to 10 sets using net "A" at 5 sites) made little 

difference in the result ("K" catch = 0.67 ["A" catch]; 3 = 0.92; p<0.01). Since the "A" 

and "K" nets were most divergent in dimension and design, we conclude that use of 

different seine nets contributed little to the observed variability in CPUE between sites or 

years (see below). 

However, this may not be true of catch composition and diversity. Using the data from 54 

sets at 10 sites, there was a weak relationship (3=0.26) between nets "A" and "K" in the 

average number of species caught per site (No. species in "K" = 0.91 [no. species in "A"] 

+ 3.5). In other words, net "K" generally caught 3-4 species more than net "A" at any 

given site. This difference likely increased later in summer as more species were 

encountered. Examination of the species lists revealed that catches of pelagic schooling 

fish (such as herring, salmonids, smelts, juvenile gadids, sand lance, etc.) were similar in 

both nets, whereas benthic fishes (such as flatfish, sculpins, etc.) were much more 

frequently caught in the "K" net. Thus, some caution is needed for comparisons of 

species diversity among sites. 

Two sites were sampled at the Barren Islands. Most sets were made at East Amatuli 

Cove, but 6 sets were also made at West Amatuli beach. Eight sites were sampled on 

Chisik Island, and 38 in Kachemak Bay during 1995-1996. After analyses of these data 

for temporal and spatial variability in catch per unit effort and species composition 
(Robards et al. 1999a), we reduced our sampling effort to cover only 12 of the original 

sites in Kachemak Bay during 1997- 1999. Beach seining was generally conducted within 

a window spanning 1.5 h on either side of high and low tides. In general, when sampling 

long-term monitoring sites on the Barrens, Kachemak and Chisik, beaches were sampled 

twice in rapid succession, using sets made on adjacent beach front. For other beaches in 

Kachemak Bay, a single set was conducted at each site as this usually provided good 

representation of species richness and dominant species rank (Allen et al. 1992, Robards 

et al. 1999a). 

Fish Measurements 

All fishes were identified, sorted and counted. Exceptionally large catches were subsampled. Fork length was measured to the nearest 1 mm. If >I00 individuals of the same 

species were captured in a single tow, a sub-sample of 50- 100 fish was measured 

(occasionally more fish were measured if needed for other project objectives). Weights 

were taken on a sub-sample of forage species (e.g., herring, sand lance, pollock). 

Weights were occasionally measured on other species. Due to the key trophic role of 

sand lance in the Gulf of Alaska (Blackburn and Anderson 1997), a much greater 

emphasis was put on assessing variability in this species, and we measured large samples 

of adult (age groups > 1) and juvenile (age group 0) age classes (as later confirmed from 

otolith interpretations). Morphometric data are not presented in this report. 

Statistical Analyses of Fish Data 

The relative importance of fish species in seine catches was examined two ways: By 

calculating catch-per-unit-effort (CPUE, total number of fish per seine set) and frequency 

of occurrence (percentage of total sets in which a species was caught). Shannon-Wiener 

index of diversity (Krebs 1989) and species richness (the total number of species) were 

calculated for beach seine data by year and area. 

Results 

Relative Abundance 

A total of 847,452 fish, including at least 75 species, were captured in 87 1 hauls (Tables 

5.3 and 5.4). Pacific sand lance dominated the nearshore community in Kachemak Bay 

and at the Barren Islands and comprised more than 75 % of all fish caught. There were 

two orders of magnitude difference in catch-per-unit-effort (CPUE) between Chisik 

Island and the Barren Islands. CPUE in Kachemak Bay was intermediate to Chisik and 

the Barrens in 1995 and 1996, and similar to the Barrens in 1998- 1999 (Table 5.5, 

Fig.5.1). 

CPUE differed markedly among years at the Barren Islands and Kachemak Bay. Mean 

CPUE at the Barren Islands declined steadily since sampling commenced in 1996. 

Median catch data suggest a more abrupt decline between 1997 and 1998. In contrast, 

mean catches in Kachemak Bay increased markedly between 1997 and 1998, although 

median catches actually show only a slight increase at that time. Chisik Island catches 

were the lowest amongst our study areas. Mean and median catches were much less 
variable than those recorded at the other two sites, and patterns of annual variation were 

similar. 

Community Composition 

Overall, diversity was highest at Chisik Island (Fig. 5.2). Catches at Kachernak Bay and 

the Barren Islands (except 1999) were dominated by sand lance. Of the three study sites, 

community composition was most consistent among years in Kachemak Bay: Sand lance 

comprised more than 75 percent of the total catch in all years. Herring was the second 

most important species in all years except 1999. The dominance of sand lance within this 

community increased over the study period and this was reflected in a steady decline of 

the Shannon-Wiener index (Fig. 5.2) and an increase in the proportion of sand lance in 

catches (Fig. 5.3). Frequency of occurrence, however, changed little among years (Table 

5.6). More than twice as many species were recorded in Kachemak than either Chisik or 

Barren islands (Fig. 5.2). By frequency of occurrence (Table 5.6), consistently common 

taxa in Kachemak Bay included also dolly varden, juvenile gadids, greenlings, sculpins, 

and sole. 

Nearshore fish communities at Chisik Island were diverse and the composition of catches 

was also the most variable among years (Fig. 5.3). Only a single set was conducted in 

1995, and so we will not discuss this further. Diversity was particularly high in 1996 and 

1998, but different taxa were prominently represented within the community in each year. 

Data for 1997 suggested lower diversity (Fig. 5.3), but this was largely the result of two 

large catches of unidentified larval fish (Fig. 5.3). In general, the community at Chisik 

was not dominated by any one species. Important taxa in some years included herring, 

sand lance, and salmonids; and to a lesser extent osmerids, pricklebacks, sculpins and 

flatfish. 

Barren Islands catches were dominated by fewer species, and catch composition differed 

markedly among years (Fig. 5.3). Catches in 1996 were very large and comprised almost 

entirely of sand lance, although gadids, osmerids, lingcod, and sculpins were taken 

frequently (Table 5.6). Sand lance abundance and frequency of occurrence diminished 

considerably in 1997 and 1998, while gadids, osmerids, lingcod and sculpins continued to 

contribute to overall diversity. Finally, in 1999, catches of sand lance plummeted while 

the frequency or abundance of other taxa (e.g., salmon, gadids, lingcod, sculpins) 

remained similar to that found in other years. One large catch of unidentified larval fish 

dominated the picture for CPUE (Fig. 5.3). In summary, inter-annual changes in catch 

composition and species diversity at the Barren Islands were driven mostly by dramatic 

changes in abundance of sand lance among years of study. 

Discussion and Conclusions 

The relative abundance and distribution of fish species in lower Cook Inlet appears to be 

largely determined by oceanography and sediment influx (Robards et al. 1999). 

Upwelling of nutrient-rich waters around the Barren Islands leads to high local 

productivity (Chapters 2 and 3), which in turn results in high abundance of forage fish 

species. Mixed water entering Kachemak Bay is also nutrient rich and becomes locally 
stratified, resulting in the highest standing stocks of phytoplankton to be found in lower 

Cook Inlet (Larrance et al. 1977). This apparently translates into high forage fish 

abundance, as it does at the Barrens. In addition, Kachemak Bay harbors a variety of 

nearshore habitats and oceanographic conditions that help support a high diversity of fish 

species (Robards et al. 1999, Abookire et al. 2000). In contrast to the Barrens and 

Kachemak Bay, water flowing past Chisik Island comes from northern Cook Inlet, and it 

carries high sediment loads from the glacial rivers that feed into it (Feely and Massoth 

1982). The silt-load and resulting low light-penetration limit phytoplanktion production 

in this area to about one-tenth the levels observed in Kachemak Bay (Larrance et al. 

1977). Furthermore, the glacial silt and mud that blanket most of the local substrates are 

probably unfavorable for many fish species. In particular, sand lance prefer clean, sandy 

substrates near shore (Pinto et al. 1984). 

Herring, gadids (walleye pollock and Pacific cod), osmerids (capelin), and sand lance are 

important forage fish for seabirds in Cook Inlet (Chapters 9- 12). Based on beach seine 

data, it is clear that Kachemak Bay supports the most robust community of forage fish in 

lower Cook Inlet. Although sand lance dominated the community, other forage fish 

populations were also abundant and reasonably stable among years; in particular herring 

and capelin. This offers some buffer to potential predators as individual species fluctuate 

in abundance among years. For example, while herring virtually disappeared in 1999, 

there were still large numbers of sand lance for predators to feed upon. In contrast, Chisik 

Island waters support low numbers of fish and the community changed markedly among 

years. There would appear to be few choices of prey that offer predators either plentiful 

food supplies or temporal stability in population size. Finally, nearshore areas around the 

Barren Islands generally supported large numbers of sand lance and gadids; although 

1999 was an exception. Like Kachemak, the Barrens offer high abundance of a few key 

prey species. One major difference, however, is that while numerous adult sand lance 

reside year-round in Kachemak Bay- and spawn on local beaches during autumn-- only 

juvenile sand lance are found at the Barrens (Robards et al. 1999a). Sand lance 

populations at the Barrens may be more dependent on currents to bring YOY sand lance 

near shore during summer, and hence populations there may be more variable. 

In this report we have provided a basic summary of findings on the abundance and 

distribution of forage fish near shore in Cook Inlet. We will continue to analyze beach 

seine data and publish our findings in peer-reviewed journals. In particular, we will 

continue to examine the distribution of individual fish species and communities with 

respect to environmental features (substrate, temperature, salinity, currents, etc., as in 

Robards et al. 1999a, 2002, Abookire et al. 2000, 2002), and we will continue to analyze 

the diets and biology ofbirds with respect to forage fish availability information gleaned 

from beach seine surveys (e.g., Litzow et al. 2000,2002). 

Although we measured fish at each site and among years (Table 5.2), morphometric data 

have not been summarized in this report. Data for sand lance have been analyzed with 

regard to size, weight and growth rates for different areas in 1995-1997 (Robards et al. 

1999b, 1999c, 2000). This work revealed that there was rapid growth of young-of-year 

(YOY) fish during the summer months, and markedly different growth patterns among 
areas. For example, sand lance bm the Chisik area exhibited slower growth during 

summer, and fish were much smaller at a given age than fish in Kachemak Bay (Robards 

et al. 2002). These findings complicate any interpretation of morphometrics data for other 

species, and we have not completed our analyses of these data. 

Limitations of Study 

We note some limitations of using beach seine data to make inferences about near shore 

fish "communities". Sampling of nearshore habitats with beach seines was limited to 

sandy and cobble substrates. Strong currents or inshore swells over 0.5 m also prevented 

effective retrieval of nets. Therefore, fish inhabiting muddy or rocky substrates, mussel 

(Mytilus edulis) and kelp beds, or the surf zone were under-represented in our study. The 

surf zone is preferentially used by some species because of low numbers of predators and 

food-rich waters (Bennett 1989). 

Also, we used four different nets during the course of our studies in three different areas 

of Cook Inlet. Comparison of catch efficiency (see Methods) suggested that use of 

different nets could account for some of the variability that we observed in CPUE and 

catch composition. However, CPUE appeared to differ much less than 2-fold among nets 

whereas CPUE differed 10- or 100-fold among areas. Nonetheless, annual variability in 

CPUE within sites sometimes varied less than Zfold, and we would tend to discount the 

importance of such minor fluctuations when different nets were involved. Similarly, it 

appeared that the "K" net, used in Kachemak Bay every year, tended to catch more 

species than other ne& perhaps owing to the small-mesh liner running along the net 

bottom. We would expect to have caught more species at the Barrens and Chisik if we 

had used a similar net-design at those locations. On the other hand, one reason we caught 

more than twice as many species in Kachemak Bay than at either Chisik or the Barrens is 

because we fished far more sets (671,94, 106, respectively) at far more sites (38,6,2, 

respectively). 

We thank everyone who spent time on the end of a beach seine or sitting in a lab 

measuring fish. In particular, thanks to Alisa Abookire for coordinating all seine 

operations in 1998-1999, and conducting all sets in Kachemak Bay. Thanks also to 

Arthur Kettle (Barrens) and Ann Harding (Chisik) for coordinating seine operations at 

their respective colonies in all years of the study. We thank those who often put their 

backs into the effort, including Dave Black, Jared Figurski, Brad Keitt, Mike Litzow, 

Kelly Mangel, April Nielsen, Martin Schultz, Mike Shultz, Thomas van Pelt, Sadie 

Wright, Stephani Zador, and Stephanie Zuniga. Finally, we acknowledge those residents 

of Kachemak Bay who helped and supported this research effort, including the Baloughs, 

Geagels, and staff of the Alaska Maritime National Wildlife Refuge. 
Literature Cited 

Abookire, A.A., J.F. Piatt and M. Robards. 2000. The influence of meso-scale 

thennohaline differences on near shore fish distributions in Kachemak Bay, 

Alaska. Estuarine and Coastal Shelf Science 5 1: 45-59. 

Abookire, A.A., J.F. Piatt, and S. Speckman. 2002. Distribution of mid-water fish 

communities in relation to oceanographic features in lower Cook Inlet, Alaska. 

Submitted to Marine Ecology Progress Series. 

Allen, D. M., S. K. Service, and M. V. Ogburn-Matthews. 1992. Factors influencing the 

collection efficiency of estuarine fishes. Trans. Am. Fish. Soc. 12 1: 234-244. 

Allen, L. 1982. Seasonal abundance, composition, and productivity of the littoral fish 

assemblage in upper Newport Bay, California. Fish. Bull., US 80: 769-790. 

Bennett, B. A. 1989. The fish community of a moderately exposed beach on the 

southwestern cape coast of South Africa and an assessment of this habitat as a 

nursery for juvenile fish. Estuarine Coastal Shelf Sci. 28: 293-305. 

Blaber, S. J. M., D. T. Brewer and J. P. Salini. 1995. Fish communities and the nursery 

role of the shallow inshore waters of a tropical bay in the Gulf of Carpentaria, 

Australia. Estuarine Coastal Shelf Sci. 40: 177-193. 

Blackburn, J. E. and P. J. Anderson. 1997. Pacific sand lance (Arnmodytes hexapterus) 

growth, seasonal availability, movements, catch variability, and food in the 

Kodiak-Cook Inlet area of Alaska. Pages 409-426 in Baxter, B. R. (ed), 

Proceedings of the Symposium on the Role of Forage Fish in the Marine 

Ecosystem. Alaska Sea Grant College Program AK-SG-97-01. 

Blackburn, J. E., K. Anderson, C. I. Hamilton, and S. J. Starr. 1980. Pelagic and 

demersal fish assessment in the Lower Cook Inlet estuary system. U.S. 

Department of Commerce, NOAA, OCSEAP Final Report, Biological Studies 12: 

259-602. 

Burbank, D. C. 1977. Circulation studies in Kachemak Bay and lower Cook Inlet. Vol. 

3. Environmental Studies of Kachemak Bay and lower Cook Inlet (Trasky, L. L., 

L. B. Flagg, and D. C. Burbank., eds.). Alaska Dept. Fish and Game, Anchorage, 

AK. 207pp. 

Cailliet, G. M., M. S. Love, and A. W. Ebeling. 1986. Fishes: A field and laboratory 

manual on their structure, identification, and natural history. Wadsworth 

Publishing Company, Belmont, California, 132- 134. 

Dalley, E. L. and J. T. Anderson. 1997. Age-dependent distribution of demersal juvenile 

Atlantic cod (Gadus morhua) in inshoreloffshore northeast Newfoundland. Can. J. 

Fish. Aquat. Sci. 54: 168-176. 

Feely, R. A. and G. J. Massoth. 1982. Sources, composition, and transport of suspended 

particulate matter in Lower Cook Inlet and northwestern Shelikof Strait, Alaska. 

NOAA Technical Report ERL-415 PMEL-34,28pp. 

Francis, R. C., S. R. Hare, A. B. Hollowed, and W. S. Wooster. 1998. Effects of 

interdecadal climate variability on the oceanic ecosystems of the NE Pacific. 

Fish. Oceanogr. 7: 1-21. 
Horn, M. H. 1980. Die1 and seasonal variation in abundance and diversity of shallowwater fish populations in Morro Bay, California. Fish. Bull., US 78: 759-770. 

Krebs, C.J. 1989. Ecological Methodology. Harper & Row, New York. 

Litzow, M.A., J.F. Piatt, A.A. Abookire, A.K. Prichard, and M.D. Robards. 2000. 

Monitoring temporal and spatial variability in sandeel (Ammodytes hexapterus) 

abundance with pigeon guillemot (Cepphus columba) diets. ICES Journal of 

Marine Science 57: 976-986. 

Litzow, M. A., J. F. Piatt, A. K. Prichard and D. D. Roby. 2002. Pigeon guillemot 

breeding biology in relation to oceanography and prey abundance: A natural 

experiment. Oecologia. In press. 

Nash, R. D. M. 1988. The effects of disturbance and severe seasonal fluctuations in 

environmental conditions on north temperate shallow-water fish assemblages. 

Estuarine Coastal Shelf Sci. 26: 123- 135. 

Nash, R. D. M. and R. N. Gibson. 1982. Seasonal fluctuations and compositions of two 

populations of small demersal fishes on the west coast of Scotland. Estuarine 

Coastal Shelf Sci. 15,485-495. 

Orsi, J. A. and J. H. Landingham. 1985. Numbers, species, and maturity stages of fish 

captured with beach seines during the spring 198 1 and 1982 in some nearshore 

marine waters of southeastern Alaska. U.S. Dept. Comm., NOAA Tech. Mem. 

NMFS FMC-86,34pp. 

Pinto, J.M., W.H. Pearson, and J.W. Anderson. 1984. Sediment preferences and oil 

contamination in the Pacific sand lance Ammodytes hexapterus. Mar. Biol. 89: 

193-204. 

Poxton, M. G., A. Eleftheriou, and A. D. McIntyre. 1983. Food and growth of 0-group 

flatfish on nursery grounds in the Clyde Sea area. Estuarine Coastal Shelf Sci. 17: 

319-337. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999a. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fisheries 

Bulletin 97: 962-977. 

Robards, M.D., Piatt, J.F., and Rose, G.A. 1999b. Maturation, fecundity, and intertidal 

spawning of Pacific sand lance (Ammodytes hexapterus) in the northern Gulf of 

Alaska. J. Fish Biol. 54: 1050- 1068. 

Robards, M.D., J.A. Anthony, G.A. Rose, and J.F. Piatt. 1999c. Changes in proximate 

composition and somatic energy content for Pacific sand lance (Ammodytes 

hexapterus) relative to maturity, season, and location. .J. Exp. Mar. Biol. Ecol. 

242: 245-258. 

Robards, M.D., G.A. Rose, and J.F. Piatt. 2002. Growth and abundance of Pacific sand 

lance, Ammodytes hexapterus, under differing oceanographic regimes. 

Environmental Biology of Fishes. In press. 

Robards, M. D., Willson, M. F. Armstrong, R.H., Piatt, J.F., (eds). 1999d. Sand lance: a 

review of biology and predator relations and annotated bibliography. Research 

Paper PNW-RP-521. Portland, OR, U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station. 327 p. 

[http://www. fs. fed.us/pnw/pubs.htrn] 
Chapter 6. Benthic and Intertidal Fishes in Kachemak Bay 

Alisa Abookire 

Introduction 

Most of the seabirds that we studied in Cook Inlet eat pelagic schooling fishes that can be 

sampled with a beach seine or mid-water trawl. The diet of the Pigeon Guillemot 

(Cepphus columba), however, consists of both demersal and pelagic forage fishes, as well 

as invertebrates (Litzow et al. 1998). Demersal and pelagic forage fish differ in their 

distribution and energy density (Van Pelt et al. 1997), and it is believed that Guillemots 

selectively forage upon the lower quality demersal fish because they are a more localized, 

reliable prey (Golet et al. 2000, Litzow 2000). 

Specifically because of our interest in assessing the entire prey base of Pigeon 

Guillemots, we sampled demersal fish in Kachemak Bay with bottom trawls fiom 1996 to 

1999 and SCUBA transects fiom 1997 to 1999. Our primary objectives were to: 1) 

measure the relative abundance of forage-sized demersal fish available to Pigeon 

Guillernots breeding at several different colonies, 2) measure seasonal and annual 

variability in abundance of demersal fish, and, 3) relate temporal and spatial patterns in 

demersal fish abundance to environmental parameters. 

Habitat selection by demersal fish and the effect of local oceanography on temporal and 

spatial patterns of abundance in Kachemak Bay have been explored in a numbers of 

publications (Abookire 1997, Abookire and Norcross 1998, Abookire et al. 2000,2001). 

The influence of demersal forage fish abundance and distribution on the diet and 

reproductive success of Pigeon Guillemots has also been thoroughly documented (Litzow 

2000, Litzow el al. l998,2000,2002a, 2002b). Thus, we have fulfilled our primary 

research objectives and documented our findings in peer-reviewed publications. 

In this report, we provide simple summary documentation and results of trawl surveys (to 

accompany the database archive), and document results of SCUBA surveys for demersal 

fish that were originally intended to complement bottom trawl surveys, but in the end, 

were insufficient for use in assessing prey availability to Pigeon Guillemots. Nonetheless, 

they may prove useful for documenting nearshore fish communities in Kachemak Bay. It 

is unlikely that we will pursue Mer analysis or publication of these data in the 

foreseeable future. 

Methods 

Bottom trawls 

Bottom trawls were conducted in late summer of 1996- 1999. From August 7 to 9, 1996, 10 

stations were sampled in Kachemak Bay at Halibut Cove, Peterson Bay, China Poot Bay, 

Neptune Bay, and Eldred Passage (Fig. 6.1). On June 30-July 2, July 17-1 8 and August 

13-17 of 1997 those 10 stations were repeated, and on August 17, 1997, three new 
stations were established and sampled near the Seldovia Bay Pigeon Guillernot colony. 

Details on all trawling stations are provided in Appendix 6.1. In 1998 we changed vessels 

and captains, and we towed a video camera at each site prior to trawling in order to assess 

the bottom for rocks or boulders (which could tear the trawl net). The camera was 

integral to selecting trawl stations. If the site had a smooth bottom and less than 50 % 

kelp cover, then we trawled it. These videos may be used to help characterize demersal 

habitat and view sediment types in Pigeon Guillemot foraging areas. 

On July 1-2, July 18, and August 14, 1998, we trawled all 13 stations from 1997 except for 

stations H1 (inner Halibut Cove) and Y2 (by Elephant Rock), which were omitted due to 

rocks. Stations M1 and S1 were replaced with M4 and S4 due to rocks and obstructions 

(reefs) seen with the camera. Additionally, four deep (25 m) stations were added; one in 

Halibut Cove (H3), Neptune Bay (N3), and two outside Seldovia Bay (S5a and S5b). 

Stations were chosen such that depth ranges 8-10 m, 10-15 m, 15-20, and 20-25 m were 

represented proportionately between the colony sites, for a total of 15 sites. These depths 

were chosen because although Pigeon Guillemots forage in water depths fiom 6 to 45 m, 

they most fiequently forage at depths of 15-20 m (Clowater and Burger 1994). 

In 1999, we trawled on 17 and 20 August at the same sites that were sampled in 1998. 

The only exception is that Y3 (near little Tutka Bay in Eldred Passage) was omitted after 

two attempts which each resulted in gear damage. The deep site in Seldovia Bay was 

S5b, as field notes fiom August 1998 indicate that S5a had an excess of shell debris and 

kelp which clogged the net. Sampling in June and July was not continued in 1999 due to 

low CPUE in trawls, which limited statistical analyses of catches among years. 

Standard tow duration in 1996 was 10 minutes. Tow duration was reduced to 5 minutes in 

1997-1999. Station depth did not exceed 25 m. We towed a 3.05 m plumb staffbeam trawl 

equipped with a double tickler chain (Gunderson and Ellis 1986). Net body was 7 mm 

squm mesh with a 4 mm mesh cod end liner. Tows were flagged as good or bad based on 

the efficiency of the trawl. If the trawl was twisted, broke a weak-link, tom, or if the net 

was full beyond the cod-end, then the tow was flagged as a bad tow (Appendix 6.1). 

All fishes were identified to species, counted and measured to the nearest mm fork length. 

Length data are not reported here, but are available in the database archive. All species of 

fish that were recorded from bottom trawls in 1996- 1999, and were measured, are listed 

in Appendix 6.2. 

We analyzed data only for fish with fork length less than 15 cm, mostly because the beam 

trawl we used tended to capture small fish. Fish were classified as either less than 

forage-size (< 8 cm) or forage-size (8 - 15 cm). Fish data were standardized to CPUE for 

an area of 1000 m2. The area towed was calculated as the effective width of net (0.74; 

Gunderson and Ellis 1986), multiplied by the width of our trawl (3.05 m), multiplied by 

tow length as determined by Global Positioning System data. Spatial comparisons were 

made between Outer and Inner Kachemak Bay, as Homer Spit (Figure 6.1) divides the 

Bay into two oceanographically distinct areas (Abookire et al. 2000). 
SCUBA transects 

SCUBA dive transects were surveyed at 10 stations around Seldovia and 10 stations 

around Moosehead Point (Figure 6.1) to assess forage fish relative abundance and species 

composition near two Guillemot colonies. Although the objectives were the same in 

1997 and 1998, dive sites differed among years. Some of the site names may be similar 

between 1997 (e.g., Moose 5) and 1998 (e.g., MH 5), but the sites in 1997 were not 

repeated in 1998 for logistic and sampling reasons. In 1997, SCUBA dives occurred on 

August 18,25, and 26, and stations were all < 10 m deep. In 1998, SCUBA dives 

occurred on June 27-29, July 14-1 5, and August 17-19, and stations were chosen so that 5 

stations in each area were < 10 m and 5 were < 20 m. Each diving team took 5 sites in an 

area (Appendix 6.3). 

In 1999, SCUBA data were used to determine the predictability of demersal prey at two 

stations that were not sampled in previous years, but were known foraging sites for 

Pigeon Guillemots (M. Litzow, unpub. data). The first SCUBA site was in Seldovia Bay 

and was sampled on July 18, 19,20, and 22, for a transect length of 100 m (Appendix 

6.3). In 1999, the first two Seldovia dives are "bad" because they did not follow the exact 

compass bearing as dives 3 and 4. Dives and 3 and 4 (July 20 and 22) were exact 

replicates. The second site was South of Cohen Island in Eldred Passage, and it was 

sampled on July 18 and 22, 1999, for a transect length of 60 m. Heavy kelp forest 

prevented us fiom swimming the desired 100 m transect length. Sampling was done 

around low tide. Sediment type (Cobble, gravel, sand, fine sand, silt) was recorded at 

start, middle, and end of each transect. Percent kelp cover of the entire transect was also 

recorded (Appendix 6.3). 

All fishes on SCUBA transects were visually categorized as less than forage-size (< 8 

cm), forage-size (8 - 15 cm), and greater than forage-size (> 15 cm). All species of fish 

recorded on SCLJBA dives in 1997- 1998 are listed in Appendix 6.4. Hermit crabs were 

recorded and categorized with the same three size classes as fish. 

No fish larger than forage-size (> 15 cm) are analyzed in this report, as larger fish are 

more likely to detect and avoid a diver. Sand lance and schooling fish were recorded, but 

removed from analysis of SCLJBA data because zeros of these species are not reliable 

data. The fish data for 1997 and 1998 are standardized to transect length of 30 m, so that 

fish counts from 60 m transects were divided in half. Spatial comparisons were made 

between Outer and Inner Kachemak Bay, as Homer Spit (Figure 6.1) divides the Bay into 

two oceanographically distinct areas (Abookire et al. 2000). 

Results 

Bottom trawls 

We caught 5,901 demersal fish (size < 15 cm) in 95 trawls from 1996 to 1999. More 

small fishes were captured than forage-size; 2.0 times more in the Outer Bay and 2.8 

times more in the her Bay. Although the Inner Bay appeared to consistently catch more 

small fish, relative abundance (CPLE) of forage-size and small demersal fishes was not 
different between Outer and Inner Kachemak Bay (Table 6.1). Seasonally, relative 

abundance did increase hm early July to August (Table 6.2). 

Beam trawl catches were composed of 41 % flatfishes (Pleuronectidae), 21 % cod 

(Gadidae), 15 % sculpins (Cottidae), 7 % pricklebacks (Stichaeidae), and 5 % ronquils 

(Bathymasteridae) (Table 6.3). Most of the remaining species were greenlings 

(Hexagrammidae) and rockfish (Sebastes spp.) (see Appendix 6.2 for a complete list). 

Demersal fish communities in the Outer and Inner Bay had different percentages of the 

same main fish groups. Demersal fish composition in the Outer Bay had more sculpins 

and rockfish, while a higher percentage of cod and pricklebacks occurred in the Inner 

Bay (Table 6.3). 

SCUBA transects 

We counted 33 1 forage-size and 350 smaller fish in 72 SCUBA dives from 1997 to 1998. 

High variability in fish counts on SCUBA transects (Table 6.4) made spatial comparisons 

of relative abundance inconclusive. 

Species observed on SCUBA transects comprised 39 % sculpins (Cottidae), 23 % 

pricklebacks (Stichaeidae), 10 % cod (Gadidae), 9 % flatfishes (Pleuronectidae), 9 % 

gunnels (Pholidae), and 6 % greenlings (Hexagrammidae) (see Appendix 6.4 for a 

complete list). Demersal fish communities in the Outer and Inner Bay had different 

percentages of the same main fish groups. Demersal fish composition in the Outer Bay 

had more sculpins and pricklebacks, while a higher percentage of gunnels, flatfish, cod 

and greenlings occurred in the Inner Bay (Table 6.3). 

In 1999, a total of 16 fish were counted on the "good" SCUBA transects near Cohen 

Island and 371 fish in Seldovia Bay (Table 6.5). Numbers were very low at the Cohen 

site, such that temporal comparisons of relative abundance cannot be made. Preliminary 

assessment of the Seldovia dives suggests that demersal fish have high site fidelity and 

low variability in distribution. 

Discussion and Conclusions 

Spatial differences in demersal fish abundance were not detected at the scale of 

Kachemak Bay (see Abookire et al. 2000), presumably because bottom waters in Outer 

and Inner Kachemak Bay had similar substrates, temperatures and salinities. Observed 

seasonal differences in fish abundance were likely related to the life-history of each 

species rather than any one physical parameter. On a scale of days, demersal fish 

displayed low spatial variability in abundance. Such observations were not unexpected, 

as the arctic shanny (Stichaars punctatus, Keats et al. 1993), some greenlings 

(Hexagrammidae, Hart 1973), and sculpins (Cottidae: DeMartini 1978 , Vdovin et al. 

1994) display territorial behavior (e-g., males often guard the eggs) and thus tend to have 

dispersed and stable spatial distributions. 

In all years, we observed more small fish than forage-size fish in all of Kachemak Bay, 

and in both the Outer and Inner bays. Kachemak Bay is a year-round nursery area for 
flatfishes (Abookire and Norcross 1998), and it appears to be a nursery for other 

groundfish as well (Robards et al. 1999). Many species of demersal fishes were captured 

in this study, and different demersal fish communities were detected between Outer and 

Inner Kachemak Bay. Trawls and SCUEIA data concur that a higher percentage of 

sculpins are found in the Outer Bay whereas gadids are more common in the Inner Bay. 

While SCUBA transects recorded a higher percentage of pricklebacks in the Outer Bay, 

bottom trawl catches and beach seines (see Abookire et al. 2000 , Litzow et al. 2000) 

showed a higher percentage in the Inner Bay. 

Demersal fishes can be challenging to sample, and there are pros and cons to both of the 

methods we used. The bottom trawl we used was a beam trawl, which is effective, 

consistent and yields good quantitative results. However, in near-shore environments 

with many habitats (especially rocks and reefs), gear damage is a common problem. 

Heavy kelp cover in areas such as Seldovia Bay prevented us from trawling because the 

kelp clogged the cod-end and fish were not captured effectively. Additionally, strong 

tidal currents, such as those in Kachemak Bay, can flip the cod-end into the mouth of the 

net or twist the net so that it does not fish properly. To counter this, we simply trawled 

during neap tides, but this constrained our time-window for sampling. 

SCUBA diving is a good compliment to trawls, because it permits one to sample reefs, 

kelp beds and other habitats otherwise impossible to sample with nets. However, strong 

tiderips in Kachemak Bay restricted diving to periods of slack water (one hour centered 

around high or low tide). This time-constraint, coupled with cold water temperatures, 

made it a challenge to sample more than 3-5 sites in one day. SCUBA is also limited by 

the depth which can be safely sampled, and repetitive dives compound the depth 

constraint. SCUBA is a partially subjective method of surveying fish that relies on a 

knowledgeable diver who can accurately identify fish and estimate fish sizes visually. 

Finally, SCUBA is quite costly and labor intensive, and yields a dataset with many zeros 

and high variability around values of relative abundance. Although we found SCUBA to 

be of limited value for comparing relative abundance among areas, it was useful in 

assessment of fish behavior, habitat characteristics, and species composition. 

One of the benefits of a multi-year study is that auxiliary species are recognized and 

range extensions can be recorded. The presence of several unusual fishes was noted in the 

summer of 1998, coinciding with the arrival of the warm ENS0 water in Kachemak Bay. 

Pacific sanddab (Citharichthys sordidus) were captured at three bottom trawl stations in 

1998, when only one individual had previously been recorded in Kachemak Bay from 

September 1994 (Abookire 1997). In 1998, Wendell's warbonnet (Chirolophis snyderi) 

was observed in both a bottom trawl and SCUBA dives, and one yellowmouth rockfish 

(Sebastes reedi) was captured in a bottom trawl. Kelp clingfish (Remicola muscarum) 

extended their northern range and were observed on 1998 SCUBA dives and then in five 

beach seine sets in 1999 (see Chapter 4). Another northern range extension was noted for 

the painted greenling (Oxylebiuspictus), which was captured on August 20, 1999 in a 

bottom trawl and on May 15, 1999 in a beach seine. 
We thank Captain Mike Geagel and Captain Greg Snedgen and all who assisted with 

bottom trawls: Mayumi Arimitsu, David Black, Elizabeth Chilton, Brian Duggan, Jared 

Figurski, Roman Kitaysky, Mike Litzow, April Nielson, and Brian Smith. Special thanks 

to Jared Figurski for encouraging the SCUBA component and to Kim Trust (USFWSI 

Anchorage) for all her time and outstanding contributions in diving and loaning us 

SCUBA equipment. We also thank Professor Brenda Norcross (Institute of Marine 

Science, University of Alaska Fairbanks) for use of the beam trawl gear. 

Literature Cited 

Abookire, A.A. 1997. Environmental factors affecting seasonal habitat and distribution 

of flathead sole and rock sole in Kachemak Bay, Alaska. M.S. thesis, University 

of Alaska Fairbanks, Alaska. 87 pp. 

Abookire, A.A., and Norcross, B.L. 1998. Depth and substrate as determinants of 

distribution of juvenile flathead sole (Hippoglossoides elassodon) and rock sole 

(Pleuronectes bilineatus), in Kachemak Bay, Alaska. Journal of Sea Research. 

39: 113-123. 

Abookire, A.A., Piatt, J.F., and Robards, M.D. 2000. Nearshore fish distributions in an 

Alaskan estuary in relation to stratification, temperature, and salinity. Estuarine, 

Coastal, and Shelf Science. 5 l(1): 45-59. 

Abookire, A.A., J.F. Piatt, and B.L. Norcross. 2001. Summer habitat ofjuvenile 

groundfishes in Kachemak Bay, Alaska. Alaska Fisheries Research Bulletin 8(1): 

45-56. 

Clowater, J.S., and Burger, A.E. 1994. The diving behaviour of Pigeon Guillemots 

(Cepphus columba) off southern Vancouver Island. Can. J. Zool. 722363472. 

DeMartini, E.E. 1978. Spatial aspects of reproduction in buffalo sculpin, Enophrys 

bison. Env. Biol. Fish. 3(4): 331-336. 

Golet, G.H., Kuletz, K. J., Roby, D.D., and Irons, D.B. 2000. Adult prey choice affects 

chick growth and reproductive success of Pigeon Guillemots. Auk 1 17: 82-91. 

Gunderson, D.R. and Ellis, I.E. 1986. Development of a plumb staff beam trawl for 

sampling demersal fauna. Fisheries Research. (Amsterdam). 4: 35-4 1. 

Hart, J.L. 1973. Pacific fishes of Canada. Fish. Res. Board Can. Bull. 180,740 p. 

Keats, D.W., Steele, D.H., Green, J.M., and Martel, G.M. 1993. Diet and population 

size structure of the Arctic shanny, Stichaeus punctatus (Pisces: Stichaeidae), at 

sites in eastern Newfoundland and the eastern Arctic. Environmental Biology of 

Fishes. 37: 173- 180. 

Litzow, M. A. 2000. Food limitation in a generalist seabird: Reproductive consequences 

of food quality and prey switching in the pigeon Guillemot (Cepphus columba). 

M.S. Thesis. University of California, Santa Cruz. 36 pp. 

Litzow, M. A. and J. F. Piatt. 2002b. Variance in prey abundance influences time budgets 

of breeding seabirds: evidence from pigeon guillemots. Submitted to J. Avian 

Biol. 

Litzow, M.A., Piatt, J.F., and Figurski, J.D. 1998. Hermit crabs in the diet of Pigeon 

Guillemots at Kachemak Bay, Alaska. Colonial Waterbirds. 21(2):242-244. 
Litzow, M. A., J. F. Piatt, A. A. Abookire, A. K. Prichard and M. D. Robards. 2000. 

Monitoring temporal and spatial variability in sandeel (Ammodytes hexapterus) 

abundance with pigeon Guillemot (Cepphus columba) diets. ICES Journal of 

Marine Science 57: 976-986. 

Litzow, M. A., J. F. Piatt, A. K. Prichard and D. D. Roby. 2002b. Pigeon guillernot 

breeding biology in relation to oceanography and prey abundance: A natural 

experiment. Oecologia. In press. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fisheries 

Bulletin 97: 962-977. 

Van Pelt, T.I., J.F. Piatt, B.K. Lance, and D.D. Roby. 1997. Proximate composition and 

energy density of some North Pacific forage fishes. Comp. Biochem. Physiol. 

118A(2): 1393-1398. 

Vdovin, A.N., Shvydkii, G.V., Afanas'eva, N.I., Rachkov, V.1, and Skokleneva, N.M. 

1994. Spatial and temporal variability of distribution of staghorn sculpin in Peter 

the Great Bay. Russian Journal of Ecology. 25(4): 274-279. 
Chapter 7. Hydroacoustic Forage Fish Biomass and Distribution in Cook Inlet 

Suzann Speckman and John Piatt 

Introduction 

Most fisheries work in the Gulf of Alaska has focused on adults of species that are 

commercially marketable (e.g., Megrey et al. 1990). Less attention has been given to 

species that are not commercially harvestecC such as sand lance (Ammodytes 

haapterus) or capelin (Mallotus villosus)-- even though many of these species are 

important prey items of commercially valuable fishes and critical in the diets of many 

seabirds and marine mammals. In addition, studies of larval fish are common (e.g., 

Stabeno et al. 1995) but studies of juveniles (generally, age-0 to age-1 or 2) are more 

uncommon. These are the age-classes of commercial ground fish such as cod and pollock 

that are commonly consumed by adult fish, seabirds and many marine mammals (Pitcher 

1980, Yang 1995, Brodeur and Bailey 1996, Memck et al. 1997). All these "forage 

fishes" play a valuable role in food-web dynamics by conveying energy from lower to 

higher trophic levels (Springer and Speckman 1997). 

For this study of the biological response of seabirds to fluctuations in prey density, we 

needed to develop a robust index of forage fish abundance around three seabird colonies 

in Cook Inlet. Whereas indices based on fishery catches have been used in some cases to 

assess prey availability to seabirds (e.g., Monaghan et al. 1989, Hamer et al. 1994, 

Anker-N.ilssen et al. 1997), acoustic surveys have been less commonly employed (e.g., 

Safina and Burger 1985, Piatt 1987, 1990). This is partially due to difficulties (and costs) 

in gathering and interpreting acoustic data, and a lack of baseline acoustic data on most 

forage species. Trawl surveys are relatively straightforward to conduct but they can be 

strongly biased if trawl stations are selected on the basis of acoustic signal strength (see 

Chapter 4). Acoustic echo-integration surveys can be used to systematically sample the 

entire water column of relatively large marine areas, and they can be particularly 

effective at showing changes in distribution of forage species over time (e.g, Johannesson 

and Mitson1983, Carscadden and Nakashima 1997). Thus, we used acoustic surveys to 

measure forage fish abundance in lower Cook Inlet during each summer of 1995-1999. 

This portion of the Cook Inlet Seabird and Forage Fish study was designed to assess 

geographic and annual variability in forage fish abundance in lower Cook Inlet. We 

conducted hydroacoustic surveys for forage fish within foraging range (ca. 45 km) of 

three seabird colonies at the Barren, Gull and Chisik islands. Overall objectives of this 

our study were to: 1) quantify forage fish abundance on transects in lower Cook Inlet and 

estimate overall forage fish biomass in each seabird study area; 2) relate the distribution 

of acoustic biomass in Lower Cook Inlet to oceanographic features and other aspects of 

the physical environment, including primary and secondary production, temperature and 

salinity, bottom depth and distance fiom shore, etc.; and, 3) quantify the characteristics of 

forage fish schools that are of importance to marine predators. 
We have begun to relate the distribution and abundance of forage fishes to environmental 

features of Cook Inlet (Robards et al. 1999, Abookire et al. 2000) and similar studies for 

some important forage species in Cook Inlet have been conducted elsewhere; for 

example, pollock (Theragra chalcogramma) and Pacific sand lance (Ammodytes 

hexaptem) in the Bering Sea (Swartzman et al. 1994, 1995, McGurk and Warburton 

1992), and capelin (Mallotus villosus) in the Labrador Current (Schneider and Methven 

1988, Carscadden and Nakashima 1997). The physical environment influences both 

primary and secondary productivity (Parsons et al. 1984) and helps to structure fish 

habitats. In turn, dispersion of forage fish strongly influences the spatial aggregation of 

seabird predators and determines the rate at which prey can be extracted from the 

environement (Schneider and Piatt 1986, Piatt 1990). Fish school characteristics such as 

density, degree of aggregation, distance from the water surface and distance from 

colonies all have important consequences for predators such as seabirds. 

Here we present summary data on the abundance and distribution of forage fish in lower 

Cook Inlet. Summary acoustic biomass estimates are also used in Chapter 14, where 

aspects of seabird biology and behavior are related to prey abundance. Study of the 

relationships between acoustic fish biomass and environmental characteristics, between 

seabirds at sea and fish schools, and of the characteristics of fish aggregations, are all 

underway as part of a Ph.D. dissertation (S. Speckman, Univ. of Washington, School of 

Aquatic and Fishery Sciences). Findings will be published in peer-reviewed journals. 

Methods 

We conducted hydroacoustic surveys for forage fishes in Lower Cook Inlet, defined as 

the area south of Kalgin Island, in late July and August from 1995-1999 (Table 7.1). 

Effort was focused around 3 seabird colony sites: the Barren Islands, Gull Island, and 

Chisik Island. These 3 core study areas support large seabird populations with similar 

suites of species. Local oceanographic regimes, however, differ greatly among the 3 sites 

(Chapter 2) and population dynamics of the seabird communities are notably different 

(Chapter 14). 

In 1995, surveys were concentrated within a 45 km radius around each of the 3 seabird 

colonies (Fig. 7.1). In 1996, coverage was more extensive (Fig. 7.2) and included areas 

in western Cook Inlet and south of the Barren Islands that were not surveyed in 

subsequent years. Furthermore, a series of nearshore coastal transects were added in 1996 

(Table 7.1, Fig. 7.2) and conducted every year thereafter. In 1997- 1999, surveys were 

similar to and slightly more extensive than those in 1995, concentrating within a 45 km 

radius of each of the 3 seabird colonies (Fig 7.3). Transects surveyed from 1997- 1999 

were identical in each of those 3 years, except that the most northerly nearshore transect 

was not surveyed in 1997. In 1996-1999, transects were established in both "nearshore" 

and "offshore" habitats. Nearshore transects followed the contours of mainland or island 

shorelines in zig-zags of 1.8 km length, where waters were generally deeper than 10 m. 

Offshore transects cut across open water from one shore to another, over depths ranging 

from 10 m to >200 m. 
In 1995 and 1997- 1999, surveys were conducted primarily from the WV Pandalus, a 22 

m stem trawler operated by the Alaska Department of Fish and Game. Surveys in 1996 

were conducted from the WV Tiglax, a 36 m vessel operated by the Alaska Maritime 

National Wildlife Rehge, U.S. Fish and Wildlife Service. In all years, surveys in some 

shallow, nearshore areas were conducted bm the WV David Grey, an 11 m Uniflite 

cabin cruiser operated by the Biological Resources Division of the U.S. Geological 

Survey. Ground speed for all vessels was approximately 1 1 - 1 5 km/hr (6-8 knots). 

Hydroacoustic data were collected with a single beam 120 kHz BioSonics DT4000 

system with a 6" beam angle. The transducer was attached to a hydrodynamic sled and 

deployed off the side of the survey vessel 1-2 m below the water surface. All data were 

logged directly to a computer in real time. GPS locations were obtained from a Rockwell 

Precision Lightweight Global-positioning Receiver (PLGR), which have a worst-case 

horizontal position accuracy off 10 m at speeds <36 kph (Anonymous 1995). At the 

beginning of the cruise in each year, the hydroacoustic system (transducer, cable and 

sounder) was calibrated in the field using a tungsten steel sphere of known target 

strength. 

In order to quantify forage fish biomass in each area and year, hydroacoustic transect data 

were first binned into 10-min (horizontal) by 5 m (depth) blocks and integrated using 

EchoViewO (Sonar Data Pty. Ltd., Hobart, Tasmania) to determine SA (mean 

backscattering per m2) of each block. The integration threshold was set at 40 dB in 

1995 and -80 dB in 1996- 1999. The use of 10-min (ca. 2-3 krn of survey) distance bins 

was arbitrary. Until a complete spatial analysis of the data have been completed, we have 

no a priori reason for selecting any particular bin size (Schneider 1989, Rose and Leggett 

1990). For these initial analyses, we chose a 10-min bin size because it may be an 

appropriate scale for some of the species we are examining (e.g., capelin, cod; Rose and 

Leggett 1988, Piatt 1990), and because it is a widely-used transect scale for seabird 

surveys (Gould et al. 1982). In general, distances surveyed among areas and years were 

similar, except for 1997 when data from some transects north of the Barrens were lost. 

Otherwise, variability in the numbers of transects used for analyses (Table 7.2) can be 

accounted for by differences in vessel speed or currents which altered the time required to 

complete transects (e.g., particularly in 1999 when ship speed was faster). 

Relative measures of acoustic biomass (SA) were converted to absolute estimates of fish 

density (fish/m2) by dividing SA by o (backscattering cross-sectional area of single prey) 

for species with the following known target strengths: 

Pollock: TS=20Log(L)-66 (Foote and Traynor 1988) 

Cod: TS=20Log(L)-65 (Rose and Leggett 1988) 

Capelin: TS=20Log(L)-65 (Rose and Leggett 1988) 

Herring: TS=26Log(L)-76 (Thomas and Kirsch 1999a) 

Sand Lance: TS=24.5Log(L)-84 (Thomas and Kirsch 1999b) 

Physoclists: TS=20Log(L)-65.5 (Foote 1987) 
Over all years of the study, the most abundant taxa caught in mid-water trawls (Chapter 

4) were sand lance (60%), gadoids (pollock and cod, 23%), herring (12%), osmerids 

(capelin and smelts, 3%) and "other" (2%). Conversion of relative to absolute biomass is 

problematical in study areas such as ours, where species overlap in geographic 

distribution (as revealed by mid-water trawls, see Chapter 4). However, species groups 

were markedly segregated by depth (Chapter 4). For example, 90% of fish caught in the 

upper 20 m were sand lance, whereas gadoids dominated (90%) at depths of 60- 100m. 

Herring and capelin were found at intermediate depths. 

In order to generate estimates of absolute biomass, therefore, we simply divided SA in 

each depth stratum by a composite o value weighted by the proportion (as determined by 

trawl data combined over four years) and TS of each group in each stratum. For this 

purpose, pollock, cod, capelin, smelts and "other" fish were all assumed to have TS 

values equivalent to a general physoclist (above)-- a sirnplifylng assumption likely to 

cause little bias considering the similarity in TS among these taxa, and compared to the 

rather large difference in sand lance and herring target strengths. Estimates of areal fish 

densities (fish/m2) were further converted to volume biomass density estimates (g/m3) by 

dividing by bin depth (5 m) and multiplying by average weights for fish of mean size 

used in calculating fish density (year, mean length, range, mean weight of all fishes 

combined: 1996,73.4 mm, 19-721 mm, 2.19 g; 1997,75.5 mm, 15-807 mm, 2.41 g; 

1998,79.7 mm, 20-760 mm, 2.37 g; 1999, 84.5 rnm, 23-897 mm, 3.05 g). 

Mean and 90' percentile biomass densities were calculated for each area (around Chisik, 

Gull, and Barren islands) and year (1996-1999). The sample unit was a single 10-min by 

5 m block, and sample sizes therefore reflect not only the number of transects (no. of 10- 

min bins) but also the depth of the water column (to a maximum of 100 m). Mean and 

90' percentile biomass densities were calculated from the entire survey area and water 

column, fiom the entire survey area but only 30 m surface layer, fiom offshore transects 

only, and fiom inshore transects only. To account for the skewed distribution of acoustic 

biomass estimates, means were calculated fiom transformed data as mean (log x+l) 

values, and then transformed back to original density units (Johannesson and Mitson 

1983). In addition to calculating mean densities, sampled blocks were analyzed for the 

frequency of occurrence of fish biomass densities ranging fiom lo-' to 10' g/m3. 

Results and Discussion 

Overall fish density was higher near Gull Island (in Kachemak Bay) than near the 

Barrens or Chisik in all years of study except 1999 (Figure 7.4). Mean acoustic biomass 

densities near Gull were generally 2-3 times greater than near the Barrens, which were 

generally 2-6 times greater than densities near Chisik (Table 7.3). Thus, acoustic surveys 

corroborated both trawl and seine results, and suggested an order-of-magnitude 

difference in forage fish biomass among the waters surrounding each of the three seabird 

colonies under study. 

Acoustic biomass in waters surrounding each colony were roughly similar between 1995 

and 1997, but started to decline in 1998, and declined further in 1999 (Fig. 7.4). Declines 
in abundance were most striking in shallow (Fig. 7.4) and inshore waters (Fig. 7.5). 

Annual changes in abundance were concordant among areas (Chisik vs. Kachemak 

?=0.78; Chisik vs. Barrens ?=0.98; Kachemak vs. Barrens ?=0.87)-- suggesting that 

factors influencing fish abundance were operating at the spatial scale of Cook Inlet. In all 

areas, fish biomass was concentrated in the upper water column (<30 m depth; Fig. 7.4, 

Table 7.4) and in inshore areas (Fig. 7.5, Table 7.5). Offshore densities were generally 

much lower than inshore densities (Fig. 7.5, Table 7.6). Except in 1996, there was little 

difference among inshore and offshore densities near Chisik, whereas densities were 2-6 

times higher inshore in Kachemak Bay (near Gull) and along the Kenai Peninsula (near 

Barrens) than offshore in all years of study. Even with the slight decline in 1998, there is 

little indication that the 1997- 1998 ENS0 event had a strong influence on acoustic 

estimates of forage fish abundance in the summers of either year- even though a 

widespread murre die-off in April of 1998 suggested that fish abundance had been 

reduced during late winter in Cook Inlet (Piatt et al. 1999). 

The average distribution of acoustic biomass at depth is more clearly illustrated by 

grouping data from all years and apportioning it among 20 m depth strata (Fig. 7.6). 

Biomass in all areas was concentrated in the upper 40 m, owing in part to the fact that 

sand lance and herring are most abundant at these depths- whether they are found 

nearshore or in deeper offshore waters (Chapter 4). Juvenile pollock are most abundant 

at depths of 60- 100 m, accounting for the peaks of biomass found at these depths near the 

Barren and Chisik islands. Stokebury et al. (2000) found almost identical results for 

herring and juvenile pollock during July in Prince William Sound. If this degree of 

segregation between gadid and herring/sand lance is typicaL and it was in all years that 

we surveyed fish in lower Cook Inlet- it has important implications for predators that 

must dive to capture prey underwater. 

Another useful way to view the differences in biomass among areas and years is to 

consider the frequency distribution of integration blocks containing differing densities of 

fish (Fig. 7.7). In particular, the fiequencies of blocks containing lo9, lo-', and 10' g/m3 

of biomass are of interest because these include the high-end densities needed to support 

foraging marine birds and mammals (Safina and Burger 1985, Piatt 1990). The 

fiequency of high-density blocks differed markedly among areas. Kachemak Bay 

contained far more high-density blocks than either the Barrens or Chisik areas, and in the 

Chisik area blocks with densities greater than 0.01 g/m3 were rare. The change in 

fiequency of high-density blocks between years was similar among areas, and the shift in 

overall fiequency distributions was well-correlated among areas (Chisik vs. Kachemak 

?=0.57, Chisik vs. Barrens ?=0.67, Kachemak vs. Barrens ?=0.79). This suggests that 

regional (Cook Inlet wide) effects on fish abundance were more important than effects 

operating at local scales. 

The geographic distribution of acoustic biomass within different depth strata is illustrated 

in Figs. 7.8-7.1 1. Shown are the raw backscattering values per unit area (SA), without 

any conversion for target strength of fishes caught on transect. Acoustic backscatter was 

highest in coastal areas and in relatively shallow water (~30m). High biomass densities 

were also observed in deep waters (>60m) surrounding the Barren Islands (Fig. 7.10). 
Integrated over all depths (Fig. 7.1 I), acoustic biomass was concentrated: 1) around the 

coast of the Kenai Peninsula, 2) along the south and north shores of Kachemak Bay, 3) in 

cold, mixed waters (Chapter 2) north of the Barren Islands and to a lesser degree in the 

cold-water plume that extends north past outer Kachemak Bay. In marked contrast to 

waters near the Barrens and in Kachemak Bay, waters adjacent to Chisik Island were 

almost devoid of acoustic signal. In some years (e.g., 1997, 1998), weak targets were 

recorded in the southeast section of the study area, corresponding to the northern 

extension of the cold-water plume at those times. 

In summary, differences in fish biomass among the three study areas reflected differences 

in oceanography (see Chapter 2). The Chisik area, with its relatively warm, turbid waters 

consistently contained the lowest fish biomass. Furthermore, fish aggregations found in 

the Chisik area had consistently lower average school densities and a much lower 

frequency of high-density patches (Fig. 7.7). This seems to reflect overall lower levels of 

primary and secondary production in the Chisik area (Chapter 3), resulting in an area that 

is unable to support a high biomass of forage fish. The high dispersion of forage fish 

around Chisik probably increases their likelihood of finding adequate zooplankton food 

supplies. Kachemak Bay is a stratified and highly productive system (Chapters 2 and 3) 

that consistently supported the highest forage fish biomass and schools with the highest 

fish densities. The Barren Islands, also nutrient-rich and productive, supported 

intermediate levels of fish biomass and school densities. These regional patterns of 

offshore fish abundance are also reflected in nearshore fish communities, with Chisik 

supporting 1-2 orders of magnitude lower fish biomass than Kachemak Bay or the 

Barrens (Chapter 5; Robards et al. 1999). 

The main reason we conducted acoustic surveys was to obtain a single index of prey 

abundance around each seabird colony that we could use to relate with seabird biology 

and behavior in each year of study. This index is provided in Table 7.3, and used in 

Chapter 14 as we examine the response of seabirds to fluctuations in prey density. 

Variability in the distribution of forage fish- both vertical and horizontaL and its 

implication to foraging seabirds (Chapter 8) will be explored more in future analyses and 

publications. We are currently using multivariate statistics to evaluate the influence of 

temperature, salinity, phytoplankton biomass, zooplankton biomass, water depth, and 

thermocline depth on the composition and distribution of forage fish schools in lower 

Cook Inlet (S. Speckman, Ph.D. thesis, in prep.). In addition, we will be characterizing 

fish schools for attributes of importance to predators, such as school density, mean school 

dimensions, school depth, degree of aggregation, etc., and comparing the attributes 

among study areas and over time. These analyses will appear in a Ph.D. dissertation for 

the College of Fisheries Sciences, University of Washington, and we will publish the 

results in peer-reviewed journals. 
Literature Cited 

Abookire, A.A., J.F. Piatt and M.D. Robards. 2000. Nearshore fish distributions in an 

Alaskan estuary in relation to stratification, temperature and salinity. Estuarine, 

Coastal and Shelf Science 5 1: 45-59. 

Anker-Nilssen, T., R.T. Barrett, and J.V. Krasnov. 1997. Long- and short-term responses 

of seabirds in the Norwegian and Barents Seas to changes in stocks of prey fish. 

Pp. 683-698 in Proceedings of the International Symposium on the role of Forage 

Fishes in Marine Ecosystems, Univ. of Alaska Sea Grant Rep. 97-01. University 

of Alaska, Fairbanks. 

Anonymous. 1995. Technical manual: operations and maintenance manual, satellite 

signals navigation sets, ANPSN- 1 1 and ANLPSN- 1 1 (V) 1. Collins Avionics & 

Communications Division, Rockwell International Corporation, Cedar Rapids, 

Iowa, 23 1p. 

Brodeur, R.D. and K.M. Bailey. 1996. Predation on the early life stages of marine fish: a 

case study on walleye pollock in the Gulf of Alaska. Pages 245-260 in Y. 

Watanabe, Y. Yoh, and Y. Oozeki, Eds. Proceedings of an International 

Workshop: Survival Strategies in Early Life Stages of Marine Resources. 1 1- 14 

Oct. 1994, Yokohama, Japan. 

Burger, A.E. and J.F. Piatt. 1990. Flexible time budgets in breeding Common Murres: 

Buffers against variable prey availability. Studies in Avian Biology 14:71-83. 

Carscadden, J., and B.S. Nakashima. 1997. Abundance and changes in distribution, 

biology and behavior of capelin in response to cooler waters of the 1990s. Pp. 

457-468 in Proceedings of the International Symposium on the role of Forage 

Fishes in Marine Ecosystems, Univ. of Alaska Sea Grant Rep. 97-01. University 

of Alaska, Fairbanks. 

Foote, K.G. 1987. Fish target strengths for use in echo integrator surveys. Journal of the 

Acoustical Society of America 82:98 1-987. 

Gould, P.J., D.J. Forsell, and C.J. Lensink. 1982. Pelagic distribution and abundance of 

seabirds in the Gulf of Alaska and eastern Bering Sea. U.S. Dept. of the Interior, 

Fish and Wildl. Serv., Biological Services Program, OBS 82/48. 294 pp. 

Hamer, K.C., P. Monaghan, J.D. Uttley, P. Walton and M.D. Burns. 1994. The influence 

of food supply on the breeding ecology of Kittiwakes Rissa tridactyla in Shetland. 

Ibis 135: 

Johannesson, K. A., and R.B. Mitson. 1983. Fisheries acoustics: A practical manual for 

aquatic biomass estimation. FA0 Fish. Tech. Pap. 240,249 pp. 

Megrey, B.A., A.B. Hollowed, and R.D. Methot. 1990. Integrated analysis of Gulf of 

Alaska walleye pollock catch-at-age and research survey data using two different 

stock assessment procedures. Pages 279-302 in L.L. Low, Ed. Proceedings of the 

Symposium on Application of Stock Assessment Techniques to Gadids. 3 1 Oct. - 

1 Nov., Seattle, WA 

McGurk, M.D. and H.D. Warburton. 1992. Fisheries oceanography of the Southeast 

Bering Sea: relationships of growth, dispersion, and mortality of sand lance 

larvae to environmental conditions in the Port Moller Estuary. Outer Continental 

Shelf Report, U.S. Minerals Management Service, MMS-92-0019. 43 pp. 
Memck, R.L., M.K. Churnbley, and G.V. Byrd. 1997. Diet diversity of Stella sea lions 

(Eumetopias jubatus) and their population decline in Alaska: a potential 

relationship. Canadian Journal of Fishery and Aquatic Sciences 54: 1342- 1348. 

Monaghan, P., J.D. Uttley, M. Burns, C. Thane, and J. Blackwood. 1989. The 

relationship between food supply, reproductive effort, and breeding success in 

Arctic Terns Sterna paradisea. Journal of Animal Ecology 58:261-274. 

Parsons, T.R., M. Takahashi, and B. Hargrave. 1984. Biological Oceanographic 

Processes. 3d Edition. Pergamon Press, Inc., Elmsford, NY. 

Piatt, J.F. 1987. Behavioural Ecology of Common Murre and Atlantic Puffin Predation 

on Capelin: Implications for Population Biology. Ph.D. Thesis, Department of 

Biology, Memorial University of Newfoundland, St. John's, Nfld. 3 1 1 pp. 

Piatt, J.F. 1990. Aggregative response of Common Murres and Atlantic Puffins to their 

prey. Studies in Avian Biology 14:36-5 1. 

Piatt, J.F., G. Drew, T.Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711 998 ENS0 event in lower Cook Inlet, 

Alaska. PICES Scientific Report No. 10:93- 100. 

Pitcher, K.W. 1980. Food of the harbor seal, Phoca vitulina richardsi, in the Gulf of 

Alaska. Fisheries Bulletin 78(2): 544-549. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fishery 

Bulletin 97:962-977. 

Rose, G.A. and W.C. Leggett. 1988. Hydroacoustic signal classification of fish schools 

by species. Can J. Fish. Aqua. Sci. 45597-604. 

Rose, G.A. and W.C. Leggett. 1990. The importance of scale to predator-prey spatial 

correlations: An example of Atlantic Fishes. Ecology 71:33-43. 

Safina, C. and J. Burger. 1985. Common tern foraging: seasonal trends in prey fish 

densities and competition with bluefish. Ecology 66: 1457- 1463. 

Schneider, D.C. 1989. IdentifLing the spatial scale of density-dependent interaction of 

predators with schooling fish in the southern Labrador Current. J. Fish. Biol. 

35:109-115. 

Schneider, D.C. and D.A. Methven. 1988. Response of capelin to wind-induced thermal 

events in the southern Labrador Current. Journal of Marine Research 46: 105- 1 18. 

Schneider, D.C. and J.F. Piatt. 1986. Scale-dependent aggregation and correlation of 

seabirds with fish in a coastal environment. Marine Ecology Progress Series 

32:237-246. 

Stabeno, P. J., A. J. Hermann, N.A. Bond, and S. J. Bograd. 1995. Modeling the impact of 

climate variability on the advection of larval walleye pollock (Tkeragra 

chalcogramma) in the Gulf of Alaska. Pages 7 19-727 in R. J. Bearnish, Ed. 

Climate Change and Northern Fish Populations. National Resource Council of 

Canada, Ottawa, ON. 

Stokesbury, K.D.E., J. Kirsch, E.D. Brown, G.L. Thomas, and B.L. Norcross. 2000. 

Spatial distributions of Pacific herring, Clupea pallasi, and walleye pollock, 

Tkeragra chalcogramma, in Prince William Sound, Alaska. Fish. Bull. 98: 400- 

409. 

Thomas, G.L., and J. Kirsch. 1999a. Unpubl. mss. Ex-situ measurements of Pacific 

Herring Clupea harengus pallis target strength. 
Thomas, G.L., and J. Kirsch. 1999b. Unpubl. mss. A note on the target-strength of 

juvenile Pacific sand lance Ammodytes hexapterus. 

Swartzman, G., E. Silverman, and N. Williamson. 1995. Relating trends in walleye 

pollock (Theragra chalcogramma) abundance in the Bering Sea to environmental 

factors. Canadian Journal of Fisheries and Aquatic Sciences 52:369-380. 

Swartzman, G., W. Stuetzle, K. Kulman, and M. Powojowski. 1994. Relating the 

distribution of pollock schools in the Bering Sea to environmental factors. ICES 

Journal of Marine Science 5 1 :48 1-492. 

Yang, M.S. 1995. Food habits and diet overlap of arrowtooth flounder (Atheresthes 

stomias) and Pacific halibut (Hippoglossus stenolepis) in the Gulf of Alaska. 

Pages 205-223 in Proceedings of the International Symposium on North Pacific 

Flatfish. Alaska Sea Grant College Program, Fairbanks. 26-28 Oct. 1994, 

Anchorage, AK. 
Chapter 8. Pelagic Seabird Abundance and Distribution in lower Cook Inlet 

Suzann Speckman 

Introduction 

Seabird distribution patterns often reflect the availability of suitable prey. Numbers of 

birds at sea are generally low in areas with poor food supplies, and higher in areas where 

forage fish schools form extended aggregations (Schneider and Piatt 1986). Seabirds 

may switch foraging areas to follow prey movements or to forage in areas of higher prey 

abundance (Piatt 1990, Schneider 1990, Logerwell and Hargreaves 1996). Oceanographic 

features such as frontal systems, water temperature and salinity, vertical stratification, 

and bathymetry can also influence seabird distribution (Decker and Hunt 1996, Piatt 

1994) usually by their action in concentrating or dispersing seabird prey species or the 

zooplanton prey those forage fish consume (Swartzman et al. 1994, 1995, Castillo et al. 

1996, Decker and Hunt 1996, Mehlum et al. 1996). 

In this study, we set out to contrast the biology of seabirds at three colonies in lower 

Cook Inlet that have markedly different population dynamics. We measured food 

supplies around each colony (Chapters 4-7) and while we conducted hydroacoustic 

surveys for fish, we also censused all seabirds and marine mammals observed on those 

transects. From these data, we propose to: 1) measure the aggregative response of 

seabirds to prey density at sea, 2) relate the distribution and abundance of marine birds in 

lower Cook Inlet to forage fish distribution and oceanographic features, and, 3) estimate 

the overall population abundance of seabirds and marine mammals in lower Cook Inlet. 

Analyses are still in progress, and here we present summary information on the 

abundance and distribution of important marine taxa in lower Cook Inlet during our years 

of study. The aggregative response is discussed in Chapter 14. The relationship between 

seabirds and their physical and biological environment will be the subject of a Ph.D. 

dissertation at the College of Fisheries, University of Washington (S. Speckman, in 

prep.). 

Methods 

We conducted surveys for marine birds and mammals in Lower Cook Met during late 

July and August of 1995- 1999 (Table 8.1). In 1995, surveys were concentrated within a 

45 km radius around each of the three major seabird colonies found in Lower Cook Inlet: 

Chisik Island on the western side of the Inlet, Gull Island in Kachernak Bay, and the 

Barren Islands, at the mouth of the Inlet between the Kodiak Archipelago and the Kenai 

Peninsula (Fig. 7.1). Owing to logistic constraints, we only surveyed waters in the NE 

quadrant around the Barren Islands. Previous studies had shown that this was the area in 

which fish-feeding seabirds were concentrated (Piatt 1994). In 1996, coverage was more 

extensive, and in addition to the core study areas surveyed in 1995, included areas in 
western Lower Cook Inlet and south and east of the Barren Islands that were not 

surveyed in subsequent years (Fig. 7.2). In 1997-1999, surveys were similar to and 

slightly more extensive than those in 1995, concentrating within a 45 krn radius of each 

of the three seabird colonies (Fig. 7.3) but providing a series of transects that were 

continuous from south to north. The most northerly transect was not surveyed in 1997. 

In 1996-1999, surveys followed transects established in both "nearshore" and "offshore" 

habitats. Nearshore transects followed the contours of mainland or island shorelines, 

where waters were generally deeper than 10 m. Offshore transects cut across open water 

from one shore to another, over depths ranging hm 10 m to >200 m. 

In 1995 and 1997- 1999, surveys were conducted primarily fiom the R/V Pandalus, a 22 

m stern trawler operated by the Alaska Department of Fish and Game. Surveys in 1996 

were conducted from the MN Tiglax, a 36 m vessel operated by the Alaska Maritime 

National Wildlife Refuge, U.S. Fish and Wildlife Service. In all years, surveys in some 

shallow, nearshore areas were conducted from the RN David Grey, an 1 1 m Uniflite 

cabin cruiser operated by the Biological Resources Division of the U.S. Geological 

Survey. Ground speed for all vessels was approximately 11-15 km~hr (6-8 knots). 

Seabird surveys were conducted according to protocols established by the U.S. Fish and 

Wildlife Service for marine birds (Gould et al. 1982, Gould and Forsell 1989). From 

1995- 1999 and for offshore surveys in 1996, all swimming buds and mammals within 

150 m on either side or 300 m forward of the boat were counted and identified to species 

and considered "on transect." For nearshore surveys in 1996, transect width was 200rn. 

Instantaneous counts of birds flying within the transect boundaries were made 3 times 

during each 10-minute time interval (Gould and Forsell 1989). The sum of flying birds 

and birds on the water for a given time period yields a density estimate (birds/km2). 

When possible, birds were recorded in discrete flocks and the following behaviors were 

recorded: flying, swimming on the waters' surface, actively feeding, standing on flotsam 

or jetsam, or holding a fish in the bill. Unusual bud sightings outside the transect 

boundaries or census times for flying birds were recorded as "off transect." Mammals 

were recorded as "off transect" when identified beyond the transect boundary. 

Bird and mammal sightings were recorded by entering them directly into a real-time 

computer data-entry system (DLOG; Glenn Ford, Portland OR) that plots sighting 

positions continuously using GPS coordinates. GPS locations were obtained fiom a 

Rockwell Precision Lightweight Global-positioning Receiver (PLGR). PLGR units have 

a worst-case horizontal position accuracy of +lo m at speeds <36 kph (Anonymous 

1995). DLOG also provides the bottom depth and the distance to the nearest shore for all 

sightings. At all times, 1 person entered data into a laptop computer, located in the 

wheelhouse, while observers surveyed hm the best vantage points of each vessel. On 

the Pandalus, 1-2 observers surveyed fiom the bow, located 3.4 m above the water's 

surface. On the Tiglax, 2 observers surveyed hm the flying bridge, located 8.5 m above 

the water's surface. Observers on the David Grey surveyed from inside the wheelhouse 

(1 m) in 1995-1996, and surveyed from the top of the wheelhouse (2.4 m) in 1997-1999. 

The number of observers ranged fiom 1-3, and the low height of the observation platform 

in 1995 and 1996 was countered by reducing the transect width. Observers actively 
scanned with their eyes ahead of and alongside the survey vessel, and species 

identifications were confirmed using 7- or 10-power binoculars. Sightings were 

immediately called to the data entry person over hand-held VHF radios. All surveys took 

place during weather conditions suitable for sighting small seabirds at 150 m. Ancillary 

data on weather, sea conditions, observation conditions, bud behavior or plumages, and 

species of fish held by birds were collected for each transect. 

For preliminary analyses, bird abundance and density estimates were based on five study 

areas. The three core study areas, Chisik, Kachemak, and the Barrens, were used for all 

years of the study, 1995-1999. Two additional areas were added for 1996: Shuyak, the 

very southernmost area surveyed, and the Central area, in the central and southwestern 

portion of the lower Inlet (Fig. 7.2). Data from transects conducted in 1996 were divided 

into appropriate areas to make them comparable with data from other years. All bud 

distribution maps were plotted using a log(x + 0.5) scale, and unless noted in the legend, 

all maps on a page were scaled so that a given symbol size represents the same number of 

birds in all maps on that page. For the purpose here of describing likely foraging areas, 

bird distribution maps include observations of only birds that were on the water, and do 

not include flying birds. All birds, regardless of activity, were used for the species 

summary table and for calculating densities at sea. 

Results and Discussion 

We surveyed marine birds and mammals along a total of 61 92 lan of transects (ranging 

fiom 763-2052 Myear) during the summers of 1995- 1999 (Table 8.1). Survey area 

comprised a total of 18 16 lan2 over the 5 years of the study. More than 135,000 marine 

birds were observed, representing 45 marine species (Table 8.2). A total of 831 marine 

mammals representing 10 species was also observed (Table 8.2). 

Sea otters comprised the majority (38%) of marine mammals observed in lower Cook 

Inlet during 1995- 1999 (Table 8.2). Other abundant species included harbor seals (2 I%), 

Dall's porpoise (13%), humpback whales (1 I%), harbor porpoises (4%), and Steller's sea 

lions (3%). Fin whales, minke whales, killer whales and northern fur seals were also 

observed in some years. Data on marine mammals have been archived and may be further 

analysed for peer-reviewed publications- although this is not a priority for this project. 

Nothing further about marine mammals will be presented or discussed here. 

Shearwaters, mostly Short-tailed Shearwaters (Puftinus tenuirostris), comprised the 

majority (48.2%) of birds observed. (Table 8.2). Other abundant species included Tufted 

Puffins (13.6%), Black-legged Kittiwakes (9.3%), Common Murres (8.0%), 

Brachyramphus murrelets (6.2%; 8% of which were Kittlitz's Murrelets, B. brevirostris), 

phalaropes (3.0%; 99% of which were Red-necked Phalaropes, Phalaropus lobatus), 

Fork-tailed Storm-Petrels (2.7%), Northern Fulmars (2.3%), Glaucous-winged Gulls 

(1.8%), Homed Pufins (1.3%) and Pigeon Guillemots (1.1 %). The remaining 2.5% of 

birds was composed of less common species including loons, grebes, tubenoses, 

cormorants, sea ducks, jaegers, gulls, terns, and alcids. 
Of all the areas we surveyed, Shuyak in 1996 had the highest marine bird densities with 

324.77 birds/km2 (Table 8.3). Kachemak supported moderate densities of birds in all 

years, and the Central region supported low densities of birds in 1996. Among the three 

core study areas, the highest densities of marine birds were observed around the Barrens 

in all years, and the lowest densities were observed near Chisik in all years (Table 8.3, 

Figs. 8.1-8.1 1). However, most of the difference in density between the Barrens and 

Kachemak Bay was due to a difference in abundance of shearwaters and Tufted Puffins, 

both of which were much more common around the Barrens. There was little difference 

between the Barrens and Kachemak Bay in their densities of common, fish-eating 

seabirds such as kittiwakes, murres and murrelets. 

Shearwaters had the highest densities of any species group observed, with an average of 

274.5 birdsikm2 in the Shuyak area in 1996 (Table 8.3). Of the three core study areas, 

shearwater densities were highest around the Barrens in 4 out of 5 years, and lowest near 

Chisik in 4 out of 5 years. Shearwater distribution in 1996, when the entire lower Inlet 

was surveyed, was well-correlated with the northward-flowing plume of cold, upwelled 

waters that forms north of the Barren Islands (contrast shearwaters in Fig. 8.1 1 with 

AVHRR imagery in Chapter 2). Other oceanic species, such as storm-petrels and 

fulmars, were also found primarily in the oceanic upwelled waters around and to the 

north of the Barren Islands (Fig. 8.1 1). As with shearwaters, their range north of the 

Barrens appears to be constrained by the extent of the cold-water plume, although the 

association does not appear to be as strong. 

Fish-eating seabirds such as murres, puffins, murrelets, guillemots, gulls, and cormorants 

were concentrated (Figs. 8.1-8.9) in coastal areas around the Barren Islands, along the 

Kenai Peninsula and along the North and South shores of Kachemak Bay. These are all 

areas in which forage fish concentrations were highest (see Chapters 4,7). Deep-diving 

species such as murres and Tufted Puffins were also widely distributed in moderate to 

high densities in offshore waters north of the Barrens, particularly in areas with high 

concentrations of juvenile pollock and capelin (Chapters 4,7). Tufted Puffin densities 

were highest around the Barrens in all years, with up to 40 puffins/km2. In the other 

study areas, puffin densities remained at or below 3.4 birds/km2. Murre densities were 

also highest around the Barrens, although densities were similar to those observed in 

Kachemak Bay in most years (Table 8.3). 

Horned Puffins were concentrated around Chisik- the only location where appreciable 

numbers bre* with densities ranging hm 0.99-4.98 birdsh2. Marbled Murrelet 

densities, although highest in Kachemak in all years, were highly variable, ranging hm 

3.4- 12.6 birds/km2 in Kachernak and dropping as low as 0.87 birds/km2 at Chisik. 

Cormorants were recorded in low densities in all areas and years. With the exception of a 

large feeding flock observed in the area offshore of Chisik Island in 1995, cormorants 

were limited to nearshore areas. Marbled Murrelets had a wide distribution, and were 

found in all portions of the study area. They occurred only rarely, however, where waters 

were >I00 m deep (i.e., within about 25 km to the north and east of the Barren Islands). 
Kittlitz's Murrelets were more limited in their distribution, and were concentrated within 

and outside of Kachemak Bay and along the Kenai Peninsula. 

Surface feeder* such as Glaucous-winged Gulls and kittiwake* and Pigeon 

Guillemots were found occasionally in offshore areas but all showed a strong tendency to 

forage within a kilometer of the shore. Kittiwake densities were highest in the Barrens 

(actually along the Kenai Peninsula) in 4 out of 5 years. Glaucous-winged Gull densities 

were variable, peaking in each of the three core study areas in different years. Guillemots 

were largely restricted to the shores of Kachemak Bay and the Kenai Peninsula. In 1997, 

a few guillemots were found in shallow waters on the eastern edge of the Chisik offshore 

area, but no guillemots were seen on Chisik shoreline transects in five years of study. 

Guillemots were dispersed, and densities were always below 2 bir*2. 

In summary, lower Cook Inlet supports some of the highest at-sea densities of marine 

birds in Alaska (Piatt 1994), with densities of over 100 birds/km2 in 3 of 5 years at the 

Barren Islands and over 300 birds/km2 in the Shuyak region. These concentrations are 

supported by high levels of biological productivity, which in turn result largely from 

persistent upwelling of cold oceanic waters around the Barren Islands and Kenai 

Peninsula and the advection of these nutrient-rich waters northward into the inlet by 

prevailing currents (Muench et al. 1978, Chapters 2 and 3). In general, the abundance 

and distribution of marine birds corresponded to patterns of oceanography andlor fish 

distribution. Procellarids (shearwaters, fulmars and storm-petrels) were associated with 

cold, nutrient-enriched upwelled waters. Fish-eating birds- such as murres, kittiwakes 

and murrelet* aggregated in areas with high forage fish biomass concentrations. 

Whereas murres are capable of diving to great depths, few were observed foraging in 

deep waters to the immediate north and east of the Barren Islands. Despite the longer 

travel times, mmes from the Barrens Islands foraged mostly in coastal waters along the 

Kenai Peninsula- perhaps because prey along the Kenai Peninsula are more predictable 

and energetically cheaper to exploit than prey in deep waters adjacent to the Barrens. It 

appears that most murres from Chisik ranged far (>50km) offshore towards Kachemak 

Bay, presumably because of the scarcity of prey closer to home. Black-legged kittiwakes 

foraged almost entirely along the coast. As we observed with murres, the richest foraging 

grounds for kittiwakes in all years were in Kachemak Bay and along the Kenai Peninsula, 

whereas few kittiwakes were observed foraging near Chisik at any time. These patterns 

of murre and kittiwake distribution help explain measures of foraging range and trip 

duration, and ultimately, reproductive success in these species (see Chapter 14). 

Analyses are still in progress, and here we have presented summary information on the 

abundance and distribution of marine birds in lower Cook Inlet. The aggregative response 

of murres and kittiwakes to prey dispersion is discussed in Chapter 14. The relationship 

between seabirds and their physical and biological environment will be the subject of a 

Ph.D. dissertation at the College of Fisheries, University of Washington (S. Speckman, in 

prep.). 
Funding for this project was provided by the Enon Valdez Oil Spill Trustee Council 

(Restoration Project 00 163M), the U.S. Geological Survey, and the Minerals 

Management Service. I am very grateful to all of the observa who helped with seabird 

surveys: J. Figurski, B. Keitt, G. Drew, G. Snedgen, J. Piatt, T. van Pelt, M. Robards, M. 

Arimitsu, B. Congdon, S. Zador, A. Harding, A. Kitaysky, C. Lascink, V. Lodha, D. 

Ruthrauff, R. Seymour, K. Hobson, A. Abookire, R. Suydam, and S. Wright. We thank 

the Captains and crews of the RN Pandalus, P. Desjardins and M. Hottman, Captain K. 

Bell of the RN Tiglax, and G. Snedgen of the RN David Grey. 

Literature Cited 

Anonymous. 1995. Technical manual: operations and maintenance manual, satellite 

signals navigation sets, ANFSN- 1 1 and ANIPSN- 1 1 (V) 1. Collins Avionics & 

Communications Division, Rockwell International Corporation, Cedar Rapids, 

Iowa, 23 1p. 

Castillo, J., M.A. Barbieri, and A. Gonzalez. 1996. Relationships between sea surface 

temperature, salinity, and pelagic fish distribution off northern Chile. ICES 

Journal of Marine Science 53: 139- 146. 

Decker, M.B. and G.L. Hunt, Jr. 1996. Foraging by murres (Uria spp.) at tidal fronts 

surrounding the Pribilof Islands, Alaska, USA. Mar. Ecol. Prog. Ser. 139: 1 - 10. 

Gould, P.J. and D.J. Forsell. 1989. Techniques for shipboard surveys of marine birds. 

U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC. Fish 

and Wildlife Technical Report 25. 22 pp. 

Gould, P.J., D.J. Forsell, and C.J. Lensink. 1982. Pelagic distribution and abundance of 

seabirds in the Gulf of Alaska and eastern Bering Sea. U.S. Department of the 

Interior, Fish and Wildlife Service, Biol. Services Program, OBS 82/48. 294 pp. 

Logerwell, E.A. and N.B. Hargreaves. 1996. The distribution of sea birds relative to 

their fish prey off Vancouver Island: opposing results at large and small scales. 

Fisheries Oceanography 5: 163- 175. 

Mehlum, F., G.L. Hunt, Jr., Z. Klusek, M.B. Decker, and N. Nordlund. 1996. The 

importance of prey aggregations to the distribution of Briimich's guillemots in 

Storfjorden, Svalbard. Polar Biology 16537-547. 

Muench, R.D., H.O. Mofjeld, and RL. Charnell. 1978. Oceanographic conditions in 

Lower Cook Inlet: spring and summer 1973. Journal of Geophysical Research 

83(C 10):5090-5098. 

Piatt, J.F. 1990. Aggregative response of Common Murres and Atlantic Puffins to their 

prey. Studies in Avian Biology 14:36-5 1. 

Piatt, J.F. 1994. Oceanic, shelf, and coastal seabird assemblages at the mouth of a 

tidally-mixed estuary (Cook Inlet, Alaska). OCS Study MMS-92, Final Report 

for Minerals Management Service, Anchorage, Alaska. 

Schneider, D.C. 1990. Seabirds and fronts: a brief overview. Polar Research 8: 17-2 1. 

Schneider, D.C., and J.F. Piatt. 1986. Scale-dependent correlation of seabirds with 

schooling fish in a coastal ecosystem. Mar. Ecol. Progress Series 32:237-246. 
Swartzman, G., E. Silverman, and N. Williamson. 1995. Relating trends in walleye 

pollock (Theragra chalcogramma) abundance in the Bering Sea to environmental 

factors. Canadian Journal of Fisheries and Aquatic Sciences 52:369-380. 

Swartzman, G., W. Stuetzle, K.Kulman, and M. Powojowski. 1994. Relating the 

distribution of pollock schools in the Bering Sea to environmental factors. ICES 

Journal of Marine Science 5 1 :48 1-492. 
Chapter 9. Common Murre Biology in lower Cook Inlet 

Thomas Van Pelt, Michael Shultz and Arthur Kettle 

Introduction 

Immediate impacts of the 1989 TN Exxon Valdez oil spill (EVOS) on Common Murres 

(Uria aalge) in the Gulf of Alaska were well documented (Piatt et al. 1990). Common 

Murres comprised most (74%) of the oiled bird carcasses recovered fiom beaches 

(>30,000; representing 10-30% of the total mortality) and putative short-term effects 

included a reduction in populations at affected colonies, delayed breeding phenology and 

low reproductive success (Piatt et al. 1990, Piatt and Ford 1996). One of the most 

severely affected areas was Cook Met, where large numbers of murres were beginning to 

gather near breeding colonies such as the Barren Islands when oil swept through the 

region in April and May of 1989. However, there is also evidence that an oceanographic 

'regime shift' occurred in the Gulf of Alaska in the early 1980's, resulting in changes in 

seabird diets and reduction of reproductive success in some marine bird and mammal 

populations (Piatt and Anderson 1996, Anderson and Piatt 1999). These changes were 

similar to some hypothesized effects of the EVOS. This raised two important questions: 

1) can effects of the oil spill on murres be separated from natural variability, and, 2) how 

will the regime shift affect the recovery of murre populations impacted by EVOS? 

To address these questions, we conducted detailed studies of murre breeding biology and 

foraging behavior at the three largest murre colonies in lower Cook Inlet: Chisik Island, 

Gull Island and the Barren Islands. We simultaneously measured forage fish distribution 

and abundance in waters around those colonies (Chapters 4-7). The purpose of this 

chapter is to document the methods we used to gather data on murres and present all the 

basic results in summaries by colony (3) and year (5) of study. Prelutllnary results of our 

studies on murres have appeared in several publications (Piatt and Anderson 1996, Zador 

and Piatt 1998, Piatt et al. 1999, van Pelt 2000). An analysis of the response of murres to 

fluctuations in prey density is given in Chapter 14. Major results on breeding biology and 

behavior presented in this chapter will be further analyzed and submitted for publication in 

peer-reviewed journals. 

The Common Murre is a highly colonial seabird with a circumpolar boreal and low-Arctic 

distribution. Only one egg is laid (although lost eggs may be replaced) and both sexes 

share incubation and chick provisioning duties. The chick is fed at the nest for 15-25 days, 

leaves the colony at < 30% of adult mass, and is subsequently cared for by one parent for 

up to six weeks. The murre colony at Chisik Island (west side of Cook Met; 60" 09' N, 

152" 34' W) underwent a steady decline to ca. 10-20% of maximum counts made in the 

early 1970s and currently supports ca. 2500 murres. The colony at Gull Island (east side 

of Cook Inlet; 59" 35' N, 15 1" 19' W) has expanded by about 80% since 1984, and 

currently supports ca. 8500 individuals. The colony at the Barren Islands (58" 55' N, 152" 

10' W) lies at the mouth of Cook Met, and supports a relatively stable or slightly 
increasing murre population that is an order of magnitude larger than the colonies at 

Chisik and Gull Islands (Piatt and Anderson 1996, Zador et al. 1997). The three colonies 

are separated from each other by about 100 krn (Fig. 7.1) and are in oceanographically 

distinct habitats (Chapter 2). Chisik Island is surrounded by stratified, relatively-warm 

estuarine waters whereas Gull Island is surrounded by colder, mixed oceanic waters with 

significant freshwater runoff (Robards et al. 1999). The Barren Islands are surrounded by 

cold, Gulf of Alaska waters because the Alaska Coastal Current enters Cook Inlet north of 

the Barren Islands and cold, nutrient-rich waters are upwelled around the Barrens and 

onto the shallow Cook Inlet shelf (Robards et al. 1999, and Chapter 2). 

Methods 

Exact protocols for monitoring murre populations, breeding biology, attendance and chick 

growth for specific colonies in lower Cook Inlet were developed during the initial years of 

the projects (00163J,M) by Arthur Kettle, Stephani Zador, John Piatt and David 

Roseneau, and standardized for common use by APEX investigators in early 1997. Much 

of the text presented here was taken or adapted from these written protocols (and see also 

Appendices 9.2 and 9.3). 

Population monitoring 

Some population monitoring plots on Gull and Chisik islands had already been established 

by Alaska Maritime National Wildlife Refuge (Homer, Alaska) personnel prior to the 

beginning of our study. To facilitate long-term comparisons, these historical plots were 

maintained. However, in some cases additional plots were created at the beginning of our 

study in 1995, and also in later years. We therefore summarized our data in several 

different ways: 1) using only historical plots, 2) using historical plots and plots created in 

1995, and, 3) using historical plots, 1995 plots, and plots created after 1995. Murre plots 

at the Barrens were established in the early 1990s by the Alaska Maritime Wildlife Refuge 

(Roseneau et al. 1995). 

All plots were photographed, and boundaries were clearly marked on the photographs. 

Using inflatable boats for access, binoculars for viewing, and tally-clickers for counting, all 

murres within the plots were counted 5- 12 times during the season between early 

incubation and the onset of chick fledging. Sea, wind, and visibility conditions were 

recorded for each count. Counts were made between 1000 and 1600 hours at Gull and 

Chisik, and between 1 100 and 2000 hours at the Barrens (times during daylight hours 

when attendance is most stable; see Birkhead and Nettleship 1980, Piatt and McLagan 

1987, Boersma et al. 1995, Roseneau et al. 1995). Two observers counted each plot. If 

the difference between observers was greater than 10% of the total, the count was 

repeated and initial results were discarded. The plot total was taken as the mean of the 

two observer counts. The sample unit is the count-day, with all plot counts for each day 

merged into a total. Plots in population counts therefore serve as an organizational tool 

and not as a statistical unit (in contrast to productivity plots; see below). Plots also allow 

for sampling of the entire colony, and help reduce potential bias fiom counting only one 

area of a colony (Birkhead and Nettleship 1980). 
Murre attendance on cliffs during the day is least variable from the end of egg-laying 

through the start of chick fledging (Birkhead and Nettleship 1980, Piatt and McLagan 

1987). Therefore, following the field season, data were culled to include only counts that 

fell within windows defined (based on the reproductive chronology at each colony, in each 

year) as mid-incubation to the beginning of fledging. Estimates for mid-incubation were 

obtained by adding 15 days to peak laying date; the start of fledging is defined as the date 

on which the first chick was observed to fledge from a productivity plot. Summaries 

presented here use only counts made within the appropriate mid-incubation to fledging 

window (Appendix 9.1). 

Productivity and breeding chronology 

Measures of Common Murre productivity and breeding chronology were derived from 

data recorded during regular observations of nest-sites (Birkhead and Nettleship 1980). 

Nest-sites were grouped into plots, and data were analyzed using plot as the sample unit. 

A minimum of seven plots were subjectively selected (to include different habitat types) at 

each study location (Chisik, Gull, and Barren Islands). Each plot comprised clusters of 8- 

40 nest-sites (sites with eggs) on cliff faces, cliff tops, or sections of flat-topped offshore 

rock. Observations of each plot were made from a marked point that was used each year. 

Plot boundaries- defined by recognizable, permanent features of the substrate were 

clearly marked on photographs taken from the observation point, and on hand-drawn 

maps that show recognizable features of the terrain. If possible, the same plots were used 

each year. When it was possible to identify nest-sites used in previous years, nest-site 

numbers were retained. New nest-sites received new numbers (or the number of an 

adjacent site plus a letter). 

Breeding chronology and breeding success of Common Murres were monitored following 

a modified version of the Type I protocols detailed by Birkhead and Nettleship (1980). 

Using digital color photographs or hand-drawn sketches, each site where a murre was 

present in the pre-laying period was mapped. Plots were monitored using a regular interval 

of 3 days typically, but this ranged from 1-7 days among islands and years. In an effort to 

obtain more precise chick fledging ages at Chisk and Gull islands in 1997 and 1998, plots 

were checked more frequently (1-2 d) just prior to fledging. The presence of the nesting 

adults and nest contents were recorded using the following codes: 

Adult codes 

S Standing and not in incubation or brooding posture. 

L Laying down and not in incubation or brooding posture. 

IP Incubation posture. A distinct posture assumed by most murres when 

incubating eggs. Adult sits forward with back humped, tail held down, and 

wings slightly dropped with tips uncrossed. 

BP Brooding posture. A distinct posture assumed by most murres when 

brooding chicks. Characterized by wing-mantling--the wing sheltering the 

chick is dropped. 

P Adult present. Cannot classify posture as any of the above. 
N No adult present. 

Nest content codes 

E Anegg is seen 

C A chick is seen 

0 There is no egg or chick 

U Undetermined nest content 

Examples: '2s' means 2 adults were standing; 'SL0' means that one adult stood, another 

lay, and there was no egg or chick; 'NC' is an unattended chick; 'N0'- is an empty nestsite. 

Laying date was defined as the first day we either recorded an adult in an incubating 

posture or saw an egg at a site where there had not been one on the previous visit. 

Because murres incubate their eggs closely, rarely revealing the egg to observers, it was 

necessary to infer some egg-laying dates based on first recording of incubating posture at 

sites where an adult was observed in an incubating posture on at least three consecutive 

visits (Murphy and Schauer 1996). For those sites that already had an adult in incubating 

posture or an egg present when first visited or mapped, laying date was back-calculated 

from hatch date, using the normal incubation period of 32-33 d (Gaston and Jones 1998). 

The presence of just-hatched chicks can also be difficult to view directly. Hatching date 

was therefore defined as the first day we either recorded an adult in brooding posture or 

saw a chick at a site where there had not been one on the previous visit. Fledgling age is 

defined as the inclusive number of days from the hatching date to the day before the date 

when the chick was first noted absent. After colony departure, chicks continue to be 

cared for by the male parent for up to two months (Varoujean et al. 1979), but for 

convenience here, and following methods used in other studies of this species, chick 

departure from the nest-site is taken as 'fledging', and chicks that have departed the nestsite as 'fledglings'. Since 15 days is the minimum nest departure age in Common Murres 

(Gaston & Jones 1998), chicks were considered to have 'fledged' successfully if they 

disappeared from the nest-site >= 15 d after hatching; any chicks that disappeared prior to 

this were assumed to have died. 

Hatching success was calculated as the proportion of active nest-sites (sites where the 

presence of an egg was either inferred or directly observed) that produced a chick, and 

breeding success was calculated as the proportion of active nest-sites that fledged a chick 

(Birkhead and Nettleship 1980). Fledging success was defined as the proportion of 

hatched chicks that fledged successfully. Reproductive success was taken as the 

proportion of nest-sites where an egg was laid from which a chick fledged. 

Calculation of productivity 

Owing to logistic constraints, we observed nests at 1-4 day intervals, rather than at the 

daily intervals recommended (Type I 'full scale' method; Birkhead and Nettleship 1980). 

Intervals were usually an odd number of days, and this simplified our estimation of laying 
and hatching dates by minimizing hctional dates. For instance, if a nest-site was 

observed to contain an egg on day and then contained a chick on day 3 (2 d interval 

between checks), the hatching date would be estimated as day 1.5. However, if the nestsite was next visited on day 4 (3 d interval between checks), the hatching date would be 

estimated as day 2. 

We developed a set of objective rules for analyzing our productivity data (rules, formulas, 

and spreadsheets for analysis were initially developed by Arthur Kettle, Alaska Maritime 

National Wildlife Refuge, Homer). Details are given in Appendix 9.2, with supplementary 

information on parameters and codes in Appendix 9.3. A useful feature of these rules is 

that they improve the precision of hatch date calculations, by excluding nest-sites with 

between-check intervals > 7 d for both laying and hatching. Since this rule acts only on 

nest-sites that produce chicks, it can artificially reduce the ratio of eggs to chicks, thereby 

artificially reducing hatching success. The analysis procedure corrects for this problem by 

first determining the proportion of nest-sites that were excluded due to excessive interval 

between checks, then reducing the number of 'egg-only' nest-sites by the same proportion. 

This rule also reduces the sample size of nest-sites per plot and any plot whose number of 

nest-sites fell below eight after application of this rule was excluded fiom analyses. 

As documented in other studies of murre productivity, we observed egg predation on 

many occasions. Thus, it can be assumed that some murre pairs laid and lost their egg in 

the 1-4 d interval between any two successive observation days, suggesting a slight 

overestimate of both hatching and reproductive success (Boekelheide et al. 1990). 

Because our observation effort was similar during the seasons and among years, however, 

this source of error should not affect the trends documented here. A hrther problem arises 

if the observation intervals span the fledging period unevenly, in which case the chick may 

be ruled to have died when in fact it may have fledged. For example, if a nest-site with 

chick was checked on day (hatch date + 12 d), then subsequently checked with no chick 

on (hatch date + 16 d), the chick would be scored as 'disappeared at age 14 d' and 

therefore dead. But in this example, there is some chance that the chick was in fact alive 

on (hatch date +15 d), and therefore successfully fledged. Errors of this kind would tend 

to artificially reduce measures of fledging success and consequently reduce estimates of 

reproductive success. However, there is an equal probability of the observation interval to 

cause a chick to be ruled as 'fledged' when in fact it died (e.g., in a situation similar to 

above example, if a check on (hatch date +13 d) was followed by a check on (hatch date + 

17 d), the chick would be ruled as 'disappeared at age 15 d' and therefore fledged, when 

in fact it could have died on (hatch date +14 d)). We therefore assume these errors to 

cancel each other; there is no evidence that the chick survival rate is non-linear between 

age 10-20 d. However, it is important to acknowledge that productivity measures using 

variable intervals between checks may not be directly comparable to measures presented in 

other studies that used either daily checks, or different intervals between checks. 

Chick diet 

Murres bring single fish to their chicks, held in line with the bill and with the tail outwards, 

leaving about half of the fish visible (Gaston and Jones 1998). Between arrival at the 
colony and delivery to the chick, there is often a brief appeasement display, during which 

the fish is held high in the air and is relatively easily seen, thereby facilitating identification. 

We used binoculars to identify prey items to the lowest possible taxonomic level, and we 

estimated the length of prey items relative to the length of an adult murre's bill gape (gape 

length was then accurately measured hm a random sample of captured adults), in onefifth multiples. Identification was based on the color and shape of the prey, and of the 

caudal, anal, adipose fins of fish. A field guide to Common Murre bill loads and other fish 

keys were used to aid identification of prey (for a copy, go to: 

.www.absc.usgs.gov/research/seabird&foragefish/pructdindex.html). 

Observation periods were of two types: targeted periods dedicated to observations of 

chick diet, and ancillary observations made during all-day adult time-budget watches (not 

at Barrens). We did not include fish haphazardly observed during productivity checks, 

since that could skew observations toward large fish. Each observation was recorded as 

one of the following three categories: (1) 'Did Not See' (a feeding occurred, but because 

the delivery was too fast or was obscured, no identification was possible), (2) Unknown (a 

view sufficient for identification was obtained, but positive identification was not made), 

or (3) the fish was identified to the lowest practical taxonomic level. 'Did Not See' 

category fish were not used for diet summaries. We also recorded the fate of each prey 

item. Only prey that were actually fed to chicks were used for these summaries, since fish 

used for display may differ from those fed to chicks. 

Adult diet 

Diets of adult murres were assessed by collection of a sample of ca. 10 individual murres 

per colony per year. We tried to sample birds during the same period that we conducted 

pelagic surveys each year, i.e., from late July to late August. The exact dates varied fiom 

year-to-year with chronology of breeding and logistic constraints (1 995 1 1 Jul - 21 Aug; 

1996 17 - 25 Jul; 1 997 3 1 Jul - 5 Sep; 1 998 22Aug - 12 Sep; 1999 1 8 - 23 Aug). Flying 

birds were killed by shotgun from an inflatable boat as they were returning to the colony. 

All collections were carried out under the authority of permits issued by the U.S. Fish and 

Wildlife Service and the Alaska Department of Fish and Game. Within four hours of 

death, carcasses were either necropsied in the field, or frozen for later necropsy in the 

laboratory. Stomachs and proventriculi were dissected out, placed individually in 18 oz 

plastic bags mrl-paks) together with a volume of 50% isopropyl alcohol to equal 

double the volume of gastric tissue and contents, then frozen. Stomachs were later 

analyzed under contract by Kathy Turco or Alan Springer (Falco Inc., Fairbanks, Alaska), 

and biomass of prey were assessed based on otolith numbers and size, using a reference 

collection maintained at the University of Alaska, Fairbanks. 

Adult attendance and provisioning 

Adult time budgets were calculated from all-day observations of 8- 12 nest-sites at each 

study location. The same nest-sites were used for all observations within each summer, 

although failed nests were replaced in later watches. During observations, the time was 

recorded for each adult amval, delivery of prey to chicks, exchange of incubation or 

brooding duty, and adult departure. Each observation-day began when nest-site activities 
became clearly visible and ended when it was too dark for observations to continue. On 

Gull Island, some observations were recorded by video and analyzed later; more complete 

details of the video recording system are given in Zador and Piatt (1999). At Chisik Island 

in 1998, a few observations were made using video recording. At the Barren Islands, a 

commute by boat is necessary to access the plot. In 1997- 1999, data were recorded with 

the time lapse video from first to last light. At Chisik and Gull islands, we conducted 

observations on 2-3 observation-days during incubation, and 3 or more observation-days 

during the nestling period. At the Barrens, data were collected on 0 (1995) to 12 (1999) 

days during incubation, and 2 (1995) to 8 (1998) days of chick-rearing. Observations 

were spread out to sample the early, middle, and late parts of the incubation and nestling 

periods. On a few occasions, observation days were synchronized among study locations. 

Where observation nests changed between years, we chose nests near the previous ones, 

to minimize the possibility of confounding among-plot effects with among-year effects. 

Nest attendance was measured in bird-minutes per nest per hour (e.g., a nest with one bird 

attending for a full hour and its mate attending for half of the hour has 90 bird-minutes 

that hour). We calculated separately nest attendance during incubation and during the 

nestling period. Adult provisioning fkequency was measured in feedings per nest per hour. 

Adult duty exchange fkequency was calculated in exchanges per nest per hour. A trip 

from the nest began when an adult left the nest and ended when it returned. Values were 

calculated separately for trips made during incubation, trips during the nestling period, and 

trips that ended with chick provisioning. Only complete trips were counted--not trips that 

were in progress when the observation period started or ended. From preliminary 

analyses, we concluded that neither nest-site or observation day contributed significantly 

to variability in behavioral parameters in a given year and we used nest-site as the sample 

unit. 

Chick growth 

We were not able to repeatedly capture individual pre-fledging chicks to measure standard 

variables such as maximum growth rate and midpoint mass. Instead, we captured chicks of 

unknown age and made single measurements of both mass and wing length (Hanis and 

Wanless 1988, Uttley et al. 1994, Bryant et al. 1999). This was done in at Chisik Island in 

1995, 1996, 1997, and 1999, and at Gull Island in 1995 and 1996. In all years, the 

captures were made in a single bout to ensure that each chick represented a unique and 

independent measurement, and capture bouts were timed to occur near the midpoint of the 

chick-rearing period, so that exceptionally early or late chicks were not over-represented. 

In all years, mass measurements were made using a 300-g spring scale. Wing 

measurements were made 1 millimeter, fkom the carpal joint to the tip of the longest 

feather. Over a range of wing-lengths fkom 25 to 45 mm the relationship between chick 

weight and wing-length was linear in all years; we therefore subsampled data to include 

only those chicks whose wings were between 25 and 45 mm (inclusive) at time of capture 

(Hams and Wanless 1988). We used linear regression to measure the relationship 

between mass and wing length by colony and by year, and we present the regression slope 

standard deviation as the sample unit for comparison between colonies and years. 
Fledgling condition 

We used captures of fledging chicks to obtain estimates of body condition and age at 

fledging. These data represent integrated growth over the first 2-3 weeks of development; 

subtle differences in growth patterns may therefore be missed using this approach, but it 

should reveal large differences between years or colonies and allows comparisons to other 

studies that present fledging mass and condition (Harris and Wanless 1988). Fledging 

chicks were captured either by hand as they made their way across cliff-base rocks toward 

the ocean, or with dipnets from boats roaming near shore. All captures were carried out 

under the authority of permits issued by the US Fish and Wildlife Service and the Alaska 

Department of Fish and Game. Handling times were minimized wherever possible to 

reduce the stress of capture. Capture dates were timed to overlap with the peak in 

numbers of fledglings. For the purposes of summarizing the data, we pooled some 

adjacent days' data into capture 'bouts' in cases where <5 individuals were captured per 

day. Within each capture day, effort was concentrated during the dusk to early night 

period (normal fledging time for murre chicks), using headlamps to aid captures and data 

collection. Mass (k 1 g) was measured using a spring scale, and flattened standard wing 

length k 1 mm (from the carpus to tip of the longest feather) was measured using a 

stopped ruler. Following capture and measurement, fledglings were released either 

directly into the sea, or onto the rocks in the area where captured. Processing each 

fledgling generally took no longer than 1 minute, and fledgling behavior post-handling 

appeared to be no different from fledglings that were not captured. 

Age of fledglings was estimated using a wing length-age regression determined from 

known-age chicks in a separate study at Duck Island (age [dl = -7.01 + 0.388[wing length 

in rnm]; n = 13; F = 59.97; P < 0.001; Van Pelt 2000). Using body size to estimate 

offspring age can be imprecise (Cooch et al. 1999); therefore estimated ages were 

compared with ages determined by chick departure from nest-sites in observed plots. 

Over three colony-years, the ages estimated by wing length did not differ from ages 

measured by chick departure (Chisik 1998 f26 = 0.507, P > 0.3; Chisik 1999 t154 = -1.254, 

P > 0.2; Gull 1999 f68 = -1.107, P > 0.2). Body mass is partly the result of structural body 

size and may not reflect the quantity of body reserves (Chaste1 et al. 1996). We therefore 

scaled mass to body size as an index of body condition, dividing mass by wing length. 

Adult body condition 

Breeding adults were captured using a telescoping fiberglass pole fitted with a noose. All 

captures were carried out under the authority of permits issued by the US Fish and 

Wildlife Service and the Alaska Department of Fish and Game. Handling times were 

minimized wherever possible to reduce the stress of capture. All birds captured were 

actively attending a nest-site, egg, or chick. Captured birds were banded with a unique 

combination of color bands and a metal USFWS band. A small blood sample for sex 

determination was taken from the wing. Blood was collected and stored in a 1.8 ml vial 

that had been pre-filled with a buffering solution. The sex of the bird was later identified 

from red blood cell DNA, using two CHD genes (Griffiths et al. 1996). Body mass (k 5 

g) was measured using spring scales; head-plus-bill and tarsus length * 1 mm using vernier 

calipers; and flattened standard wing length k 1 mm (carpus to distal end of longest 
primary feather) using a stopped ruler. Body mass is partly the result of structural body 

size and may not reflect the quantity of body reserves (Chaste1 et al. 1996). We therefore 

scaled mass to body size as an index of body condition, dividing mass by wing length. 

We attempted to capture adults on a regular schedule to represent condition during 

prelaying, early, middle and late incubation, and early, middle and late chick-rearing. The 

target sample size per capture session was 10 adults. However, due to logistical 

considerations not all captures per session could be made on the same day. For the 

purposes of summarizing the data, we therefore grouped captures into 'bouts' of captures 

made within a few days of each other. 

Adult corticosterone levels 

Simultaneous with captures made for measurement of adult body condition, we took 

blood samples from the alar vein within 3 minutes of capture. Blood was collected in 

microhematocrit capillary 100 microliter tubes, which were then emptied into 0.5 ml 

Eppendorf vials. Blood samples were stored on ice, and then centrifuged within 12 hours, 

after which the plasma was collected and frozen. Plasma samples were later analyzed for 

corticosterone concentrations by radioimmunoassays in J.C. Wingfield's lab at the 

University of Washington (for further details on methods used for assays and analyses, see 

Kitaysky et al. 1999 and references therein). 

Population plots 

Results for each group of census plots are summarized by colony and shown in Tables 9.1- 

9.3. There was no consistent trend across the five years of study at either Chisik or Gull 

Islands, but in 1998 there was a clear drop in numbers at both colonies (Tables 9.1,9.2). 

Murres appeared to be increasing slowly at the Barren Islands (Roseneau et al. 2000). 

When results are put in context with historical data, and examined over longer times 

periods, a downward trend at Chisik Island and an increasing trend at Gull and the Barren 

islands are apparent (Appendix 9.10). We believe that murre population plots at Gull 

Island are now saturated with breeding birds, and population increases are better revealed 

from whole-island counts (Appendix 9.11). Even during the short course of our study, we 

have noticed an increase in murres on parts of the Gull Island colony that were not used in 

previous years. 

Population estimates 

Entire island counts were conducted to estimate the absolute size of populations on each 

island. Two whole-island counts were conducted on Chisik Island and four counts on Gull 

Island between 1995-1999. These data corroborate results of population plots censuses 

and showed that between 1995- 1999, the Gull Island population continued to increase 

(Appendix 1 I). When the data collected between 1995- 1999 are summarized with 

historical counts, they show a continuing decline in the murre population on Chisik as 

numbers went from an estimated 20,000-25,000 murres in 1970 to 3,500 in 1997. On Gull 

Island, the population has fluctuated over the past 23 years but overall the population has 
persisted to increase from 3,200 birds in 1976 to an estimated 10,725 birds in 1999. 

Whole island counts of murre populations at the Barren Islands are problematic, and there 

are no good historic data with which to assess whole-island population trends (Piatt and 

Anderson 1996, Roseneau et al. 1995). 

Productivity 

All measures of productivity tended to be broadly consistent within colonies, but there 

were dramatic departures fiom this in 1998 and 1999. Across the five years of study, 

mean hatching success varied among the Chisik, Gull, and Barren Island colonies (Table 

9.4), and there was no consistent trend across years. However, hatching success was 

markedly depressed at Chisik Island in 1995 and1998, at Gull Island in 1999, and was 

relatively low at the Barren Islands in 1998 (Table 9.4). Fledging success was consistently 

high at the Barren Islands, and tended to be higher at Chisik Island than at Gull Island 

across the four years for which concurrent data were available, with the exception of 1998 

when fledging success at Chisik Island was sharply reduced in comparison to Gull Island 

(Table 9.5). Breeding success followed a similar pattern to the other measures of 

productivity, with the highest average success at the Barren Islands, nearly equal average 

success at Chisik and Gull Islands, no detectable trend across years, and exceptionally low 

success at Chisik Island in 1998 and at Gull Island in 1999 (Table 9.6). 

Breeding chronology 

Mean egg laying dates showed greater variation at Chisik Island (range 6 July to 26 July) 

than at Gull Island (range 9 July to 13 July); birds at Chisik Island tended to lay later than 

at Gull Island, but this trend was inconsistent across years (Table 9.7). Murres at the 

Barren Islands tended to be the first to lay eggs among the three colonies, and their mean 

laying dates were relatively consistent between years (range 1 July to 7 July). Egg laying 

was severely delayed at Chisik Island in 1998 (Table 9.8). The pattern in mean hatching 

dates between colonies and years was similar to the pattern in egg-laying (Table 9.8), as 

expected given a relatively consistent incubation duration of ca. 33 days in this species. 

Chick diet 

Summaries of the taxonomic composition of chick diets are presented in Table 9.9 

(detailed species composition is provided in Appendices 9.4-9.6). Osmerids and sand 

lance were the dominant species across the whole study area, together accounting for 50- 

90% of chick diets. There were some conspicuous differences among the colonies: Chick 

diet at the Barren Islands was overwhelmingly dominated by Osrnerids (capelin), while 

Gull Island chicks were fed a variety of species across years, but in particular, sand lance. 

Chick diets at Chisik Island were consistently dominated by Osmerids (smelts), together 

with a varying mixture of sand lance and gadids. There was a notable trend of increasing 

osmerids in chick diets at Gull Island, fiom 6% in 1995 to 56% in 1999 (Table 9.9; 

Appendix 9.9, and sand lance consumption increased at Chisik Island between 1997- 

1999, fiom 12% to 36% (Table 9.9; Appendix 9.4). 
Adult diet 

Summaries of the taxonomic composition of adult diets are presented in Table 9.10 

(detailed species composition is provided in Appendices 9.g9.10). Pooling data across 

years, osmerids and sand lance dominated diets at all three colonies, accounting for 55% 

to 86% of adult diets (Table 9.10). However, there were some notable differences 

between colonies and years. At Chisik Island, sand lance consistently dominated adult 

diets across all years, while significant consumption of osmerids occurred only in 1996 and 

1999. Gadids were important in 1995, but less so in all other years. At Gull Island, sand 

lance were overwhelmingly dominant in all years except 1998, when osmerids mostly 

replaced sand lance. Gadids were important only in 1997. At the Barren Islands, gadids 

were dominant in 1995-1997, while osmerids increased to dominate in 1998. Sand lance 

were virtually absent from adult diets at the Barren Islands until 1999, when they 

represented over 70% of the diet. 

Adult attendance and provisioning 

Summaries of adult attendance during incubation are given in Table 9.1 1, using nest-site 

as the sample unit (see Methods). Attendance was consistently higher at Gull Island than 

at Chisik Island (Table 9.11). There were no consistent trends across years at either 

colony, and little inter-year variation in attendance at either Gull or Chisik Islands. 

Attendance during incubation at the Barren Islands was relatively high (Table 9.1 l), and 

was consistent between years with the exception of 1997 when attendance was 

exceptionally high. 

Attendance during the chick-rearing phase is summarized in Table 9.12, using nest-site as 

the sample unit. Again, attendance was consistently higher at Gull Island than at Chisik 

Island, although the difference was marginal in 1996 and 1999. Attendance at Chisik 

Island was consistently low, with little variation between years. There was marked 

variation between years at Gull Island (Table 9.12). Mean attendance at the Barren 

Islands was similar to Gull Island, and there was also considerable variation between years 

(Table 9.1 2). 

Chick-feeding rates are shown in Table 9.13, using nest-sites as the sample unit. Trip 

durations are shown in Table 9.14, using nest-sites as the sample unit. Chick-feeding rates 

were consistently higher at Gull Island than at Chisik Island, and trip durations were 

generally shorter at Gull Island than at Chisik Island. Barren Island feeding rates were 

similar to Gull Island, while Barren Island trip durations were intermediate between Gull 

Island and Chisik Island. There was no obvious trend across years in provisioning rates or 

trip durations at any colony; however, there were some years with extreme parameter 

values. Chick-feeding rates at Chisik were relatively low in 1996 and 1998 compared to 

other years, and at Gull Island they were relatively low in 1998 (Tables 9.13). Foraging 

trip durations at Chisik Island were much longer in 1996 than in other years, and at Gull 

Island they were relatively shorter in 1997 than in other years. 
Chick growth 

The 'growth rate' (see Methods) of chicks fiom the Chisik and Gull colonies varied 

considerably among years, with significant differences between years at both colonies 

(Table 9.15; ANCOVA; Chisik F3, 128 = 3.08, P = 0.03; Gull F1,37 = 10.02, P = 0.03). To 

compare between colonies, we pooled data from the two years (1 995- 1996) where 

overlapping data were available. Slopes did not differ (ANCOVA Fl, 1 = 1.73, P = 

0.19). No growth rate data were obtained from the Barren Islands. 

Fledgling condition and age 

The size, condition, and estimated age of fledglings captured when departing the colony 

are given in Tables 9.1 6-9.18. With data fiom all three years pooled, it appears that chicks 

fiom the Barren and Gull Islands fledge in slightly better condition (index 3.1 7-3.18) than 

chicks fiom Chisik Island (index 3.07). There was no apparent trend in condition among 

years or within sites. Chicks fledged at an average age of 18-24 days, based on estimates 

of age derived fiom observations at productivity plots (Table 9.19) or fiom the size of 

fledglings as they departed the colony (Table 9.16-9.18). In general, there was little 

variation and no apparent trend in chick age among colonies and years. Ages were not 

estimated fiom Barrens fledgling data, and productivity data were not collected at fine 

enough resolution to age chicks. 

Adult condition 

Summaries of the size and condition of adults are given in Tables 9.20-9.2 1. Adults were 

not captured at the Barren Islands. Pooling data over all three years, the size and condition 

of adults at Chisik and Gull Islands were virtually identical. There were no apparent size 

differences between years at either colony, but birds at Chisik Island were heavier and 

consequently in better condition in 1997 compared to 1998-1999, while birds at Gull 

Island were in poorer condition in 1997 compared to other years (Tables 9.20-9.21). 

Adult corticosterone levels 

The baseline levels of corticosterone hormone concentrations (nglml) for adults at Chisik 

and Gull Islands are summarized in Table 9.22. There was high variation in corticosterone 

levels across breeding phases and years. Concentrations of corticosterone in adults at 

Chisik Island in 1998 were relatively high throughout the entire breeding season, in 

contrast to other colony-years, when concentrations either increased across the season 

(Chisik and Gull in 1997) or varied across the season (Chisik in 1999, Gull in 1998 and 

1999; Table 9.22). 

Discussion and conclusions 

There were no striking trends in population plot counts during the five years of this study. 

However, there was considerable among-year variation in counts. For example, there was 

a drop in numbers at Chisik Island in 1998 that was probably linked to the ENS0 event of 

1998 (Piatt et al. 1999). This kind of annual variability often precludes analysis of trends 

over short time periods. Consideration of trends over larger time Mes than this study 
(Appendices 9.10,9.11, Roseneau et al. 1995, 1998,2000) suggest that murres are 

increasing at the Barren Islands by 4.4% per annum (1 989- 1999), increasing at Gull Island 

by 8.8% per annum (1984-1999, whole island counts), and decreasing by 8.9% per annum 

at Chisik Island (1 97 1 - 1999). 

With a few exceptions, measures of productivity (hatching, fledging, and breeding 

success) were broadly consistent within colonies and among years. These results follow 

the well-established reproductive patterns observed in this species, with stable and high 

levels of breeding success across a range of moderate to good food availability and 

ecological conditions, but occasional years of exceptionally low productivity when 

conditions fall below some threshold (Boekelheide et al. 1990, Burger and Piatt 1990, 

Piatt and Anderson 1996). Owing to the scarce food supply around Chisik Island (Robards 

et al. 1999, Chapters 4,5 and 7) we expected murres there to do worse than those at Gull 

Island- and not better, as observed. The low attendance measured at Chisik Island must 

reflect increased parental effort in reproduction, and buffering of productivity against low 

food abundance (Burger and Piatt 1990, Uttley et al. 1994, Monaghan 1996). The fact 

that fledglings at Chisik Island were in similar condition to those at Gull Island may also 

be ascribed to buffering efforts. We would expect such increased efforts to come at a 

cost, most likely a reduction in adult condition andlor survival. There were no large 

differences in body condition of adults between the colonies, however, and we are still 

assessing adult survival at both colonies (EVOSTC funded project 01338). Results of that 

work will likely add to our interpretation of work presented here. 

The purpose of this chapter was to document methods used to collect data on Common 

Murres, and to summarize the main results of our studies on this species. The ultimate 

objective is to interpret how various parameters of murre biology and behavior vary with 

food supply. To that end, a preliminary synthesis on the response of murres to fluctuations 

in food supply is presented in Chapter 14. Results presented in this chapter will be further 

analyzed and submitted for publication in peer-reviewed journals. 

Acknowledernents 

The work presented here is the product of many dedicated employees and volunteers. 

Stephani Zador was responsible for initiating field work on Gull and Chisik islands in 

1995, and over the years 1995- 1997, was instrumental in helping to develop and refine 

protocols for murre data collection at all three colonies (in concert with Arthur Kettle, 

who led field work on the Barren Islands in 1995-1999; See Roseneau et al. 2000 for 

acknowledgments of support for Barrens work). Ann Harding collected murre data at 

Chisik in all years of study, and greatly influenced the study design. Her efforts were 

instrumental in making the field work a success on Chisik. We also thank Yumi Arimitsu, 

Jeb Benson, Dave Black, Leigh Ochikubo [Chan], Alice Chapman, Jared Figurski, Mike 

Gray, Greg Hoffian, Brad Keitt, Roman Kitaysky, April Nielsen, Ram Papish, Mike Post, 

Brian Smith, Shiway Wang, Jenny Wetzel, and Sadie Wright for their vital help with field 

work. We are grateful to Vernon Byrd and Brian Smith for their assistance in compiling 
the data archive. Sasha Kitaysky shared his research expertise and wisdom with us. Greg 

Snedgen provided logistic help that increased the safety and efficiency of our work. Brad 

Keitt is thanked for refitting the RN David Grey, and we thank Greg Snedgen for running 

the boat during the 1997- 1999 field seasons. We thank Vernon Byrd and staff of the 

Alaska Maritime National Wildlife Rehge, and Mike Gaegel and staff of the Kasitsna Bay 

Marine Lab for their support. Finally we thank the residents of Chisik Island, Tuxedni 

Channel, Halibut Cove, and Kasitsna Bay. 

Literature Cited 

Anderson, P. J. and J. F. Piatt. 1999. Trophic reorganization in the Gulf of Alaska 

following ocean climate regime shift. Mar. Ecol. Prog. Ser. 1 89: 1 17- 123. 

Birkhead, T.R. and D. Nettleship 1980. Census methods for murres, Uria species: a 

unified approach. Can. Wildl. Serv. Occas. Pap. No. 43. 25 pp. 

Bryant, R., I.L. Jones, and M.J. Hipfner. 1999. Responses to changes in prey availability 

by Common Murres and Thick-billed Murres at the Gannet Islands, Labrador. Can. 

J. ZOO^. 77: 1278-1287. 

Boekelheide, R.J., D.G. Ainley, S.H. Morrel, H.R. Huber, and T.J. Lewis. 1990. 

Common Murre. Pp. 245-275 in: Seabirds of the Farallon Islands (D.G. Ainley and 

R.J. Boekelheide, eds.), Stanford University Press, Stanford. 

Boersma, P.D., J.K. Pamsh, and A.B. Kettle. 1995. Common murre abundance, 

phenology, and productivity on the Barren Islands, Alaska: The Exxon Valdez oil 

spill and long-term environmental change. Pp. 820-853 in Exxon Valdez Oil Spill: 

Fate and effects in Alaskan waters, ASTM STP 1219, (P.G. Wells, J.N. Butler, 

and J.S. Hughes, eds.), Amer. Soc. for Testing and Materials, Philadelphia, PA. 

Burger, A.E. & Piatt, J.F. 1990. Flexible time budgets in breeding common murres: 

buffers against variable prey abundance. Stud. Avian Biol. 14,71-83. 

Byrd, G.V. 1989. Seabirds in the Pribilof Islands, Alaska: trends and monitoring 

methods. M.S. thesis, Univ. of Idaho. 

Chastel, O., H. Weimerskirch, and P. Jouventin. 1995. Body condition and seabird 

reproductive performance: a study of three petrel species. Ecol. 76: 2240-2246. 

Dragoo, D.E. and B.K. Dragoo. 1994. Results of productivity monitoring of kittiwakes 

and murres at St. George Island, Alaska in 1993. U.S. Fish and Wildl. Serv. Rep., 

AMNWR 94/06. Homer, AK. 70 pp. 

Hams, M.P. and S. Wanless. 1988. The breeding biology of guillernots Uria aalge on the 

Isle of May over a six year period. Ibis, 130, 172- 192. 

Hatch, S.A. and M.A. Hatch, 1990. Breeding seasons of oceanic birds in a subarctic 

colony. Can. J. Zool. 68: 1664 - 1679. 

Hunt, G.L., Z. Eppley, B. Burgeson, and R. Squibb. 1981. Reproductive ecology, food, 

and foraging areas of seabirds nesting on the Pribilof Islands, 1975-1979. Pp. 1- 

258 in Environ. Assess. Alaska Contin. Shelf, Final Rep. Princ. Invest., Minerals 

Manage. Serv., Anchorage, AK. 97 pp. 

Gaston, A.J. and I.L. Jones. 1998. The Auks. Oxford University Press, Oxford. 

Griffiths, R., S. Daan and C. Dijkstra. 1996. Sex identification in birds using two CHD 

genes. Proc. Royal Soc. London (B) 263: 125 1 - 1256. 
Monaghan, P. 1996. Relevance of the behaviour of seabirds to the conservation of marine 

environments. Oikos, 77,227-237. 

Murphy, E.C. and J.H. Schauer. 1994. Numbers, breeding chronology, and breeding 

success of common mum at Bluff, Alaska, in 1975- 199 1. Can. J. Zool. 72: 2 105- 

2118. 

Piatt, J. F., C. F. Lensink, W. Butler, M. Kendziorek and D. R. Nysewander. 1990. 

Immediate impact of the Exron Valdez oil spill on marine birds. Auk 107: 387-397. 

Piatt, J.F. and R. McLagan. 1987. Colony attendance patterns of Common Murres (Uria 

aalge) at Cape St. Mary's, Newfoundland. Can. J. Zool. 65: 1530-1534. 

Piatt, J. F. and P. Anderson. 1996. Response of common murres to the Exron Valdez Oil 

Spill and long-term changes in the Gulf of Alaska marine ecosystem. American 

Fisheries Society Symposium 18: 720-737. 

Piatt, J. F. and R. G. Ford. 1996. How many seabirds were killed by the Exron Valdez oil 

spill? American Fisheries Society Symposium. 18: 7 12-7 1 9. 

Piatt, J.F., G. Drew, T.I. Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711998 ENS0 event in lower Cook Inlet, 

Alaska. PICES Scientific Report No. 10:93- 100. 

Robards, M.D., J.F. Piatt, A.B. Kettle, A.A. Abookire. 1999. Temporal and geographic 

variation in fish communities of lower Cook Inlet, Alaska. Fish. Bull. 97: 962-977. 

Roseneau, D.G., A.B. Kettle, and G.V. Byrd, 1995. Common murre restoration 

monitoring in the Barren Islands, 1993. Restoration Project No. 93049. Unpubl. 

final rept., U.S. Fish Wildl. Serv., Homer, AK. 

Roseneau, D.G., A.B. Kettle, G.V. Byrd. 1998. Common murre population monitoring at 

the Barren Islands, Alaska, 1997. Enon Valdez Oil Spill Trustee Council 

Restoration Project 97144 Annual Report, U.S. Fish and Wildlife Service, Alaska 

Maritime National Wildlife Refuge, Homer, Alaska. 

Roseneau, D.G., A.B. Kettle, G.V. Byrd. 2000. Barren Islands seabird studies. Exron 

Valdez Oil Spill Trustee Council Restoration Project Final Report (Restoration 

Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Refuge, Homer, Alaska. 

Uttley, J.D., P. Walton, P. Monaghan and G. Austin. 1994. The effects of food abundance 

on breeding performance and adult time budgets of guillemots Uria aalge. Ibis 

136: 205-213. 

Van Pelt, T.I. 2000. Reproductive costs and their expression in the common guillemot 

Uria aalge. M.Sc. thesis, University of Glasgow, Scotland. 140 pp. 

Varoujean, D.H., S.D. Sanders, M.R. Graybill and L. Spear. 1979. Aspects of Common 

Murre breeding biology. Pacific Seabird Group Bulletin, 6,28-28. 

Zador, S.G. and J.F. Piatt. 1999. Time-budgets of Common Murres at a declining and 

increasing colony in Alaska. Condor 10 1 : 149- 152. 
Chapter 10. Black-legged Kittiwake Biology in lower Cook Inlet 

Michael Shultz, Ann Harding and Arthur Kettle 

Introduction 

Black-legged Kittiwakes (Rissa tridactyla) are among the most abundant nesting seabirds 

in the Gulf of Alaska (GOA) and Cook Inlet (Irons 1996, Sowls et al. 1978). Kittiwakes 

are small, pelagic gulls that breed colonially, build nests on cliffs by the ocean, and feed 

mostly on small forage fish that they capture at the surface. They typically locate prey 

while flying and then seize those prey fiom the surface or after plunging into the upper 

water layer (Irons 1996). Surface feeding species were impacted. less by the Exxon 

Valdez oil spill (EVOS) than diving species. Of the 29,175 oiled birds recovered before 1 

August 1989, only 2.4% were surface feeding gulls (Lams and Rissa spp.) (Piatt et 

a1.1990). There was a large die-off of seabirds in August and September of 198% 

apparently due to starvatio- in which kittiwakes comprised 14% of carcasses recovered 

(Piatt et al. 1990). 

Some seabird populations declined dramatically in the GOA over the past few decades 

(Hatch and Piatt 1995, Piatt and Anderson 1996). A proportion of these declines can be 

attributed to anthropogenic factors such as the EVOS, but natural changes in availability 

of forage fish that began in the late 1970's also affected seabird populations. This major 

ecosystem reorganization, or "regime shift", was characterized by a precipitous decline of 

some forage fish species such as capelin and a marked increase in large, predatory fish 

such as pollock (Piatt and Anderson 1996). Coincident with this regime shift, Blacklegged Kittiwake populations declined at some colonies in the GOA, while other 

populations increased (Hatch and Piatt 1995; Piatt and Anderson 1996; Zador et al. 

1997). 

Because of their abundance in the EVOS area and history of study, kittiwakes were 

chosen for fbrther study to assess the relative importance of natural and EVOS effects on 

seabird populations in the GOA (Irons 1996). They are densely colonial, highly visible 

cliff-nesters, and evidence suggests that they respond readily to both long and short-term 

changes in the environment (Aebischer et al. 1990). The breeding biology of kittiwakes 

has been well studied in many areas of the world, including Prince William Sound (PWS) 

(e.g., Irons 1996) and lower Cook Inlet (e.g., Bailey 1975a,b Manuwal and Boersma 

1978, Dippel and Nysewander 1992, Slater et a1 1984). Despite a wealth of studies at 

colonies, however, only one previous study has examined relationships between breeding 

biology and changes in food supply (Hamer et al. 1991). 

To improve our understanding of relationships between kittiwake biology and food 

supply, we conducted detailed studies of kittiwakes at the three largest colonies in lower 

Cook Inlet: Chisik Island, Gull Island and the Barren Islands. We collected data on 

kittiwake population trends, breeding chronology, breeding success, chick growth, time- 
activity budgets, chick diet and energy provisioning rates, adult diet, stress hormone 

levels, and adult survival, hm 1995-1999. We simultaneously measured forage fish 

distribution and abundance in waters around those colonies (Chapters 4-7). The purpose 

of this chapter is to document the methods we used to gather data on kittiwakes and 

present all the results of our research in summaries by colony (3) and year (5) of study. 

An analysis of the response of kittiwakes to fluctuations in prey density is given in 

Chapter 14. Major results on breeding biology and behavior presented in this chapter will 

be further analyzed and submitted for publication in peer-reviewed journals. 

Methods 

Protocols for monitoring kittiwake populations, breeding biology, attendance, chick 

growth and diets were compiled and refined for use in APEX funded studies by David 

Irons (FWS, Migratory Bird Management, 101 1 E. Tudor Rd., Anchorage), Dan Roby, 

Rob Suryan and Jill Anthony, based on previous protocols that were written by Vern 

Byrd, David Irons, Kirk Lenington, Dan Roby, Rob Suryan, and contributions hm 

Arthur Kettle, Stephani Zador, Ann Harding and John Piatt. Much of the text presented 

here was adapted fiom these written protocols (version 4, June, 1998). 

Study Areas 

We conducted our study fiom 1995-1999 at Chisik and Duck Islands (collectively 

referred to as Chisik), Gull Island (including 60' Rock) and the Barn Islands. The three 

colonies are separated fiom each other by about 100 km (Fig. 7.1) and are in 

oceanographically distinct habitats (Chapter 2). Field crews were present at each colony 

continuously hm late May through August in 1995- 1997, and fiom late May through 

mid-September in 1998-1999. Personnel (led by Arthur Kettle) f?om the Alaska 

Maritime National Wildlife Refuge (AMNWR) conducted studies at the Barren Islands. 

Chisik and Duck Islands are located on the western side of lower Cook Inlet at about 60' 

09' N, 152' 34' W. Both islands are part of the Alaska Maritime National Wildlife 

Refuge. Chisik Island is 2606 ha in area, has a peak elevation of 8 15 m, and is located 

about 0.8 km fiom the mainland. Duck Island is 0.4 km east of Chisik, covers about 2.4 

ha, and reaches a maximum elevation of 49 m. Chisik and Duck Islands support 

approximately 20,000 Black-legged Kittiwakes (Zador et al. 1997) that nest mostly on the 

southern portion of Chisik, with smaller numbers nesting in the central portion of 

Chisik's eastern coast, and along the cliffs of Duck Island. Biologists censused kittiwake 

populations here in the early 1970s (Snarski 1970, 197 1 a-c, 1974) and personnel fiom 

AMNWR monitored populations and reproductive success intermittently through the 

1980s and 1990's (Jones et al. 1980, Kafka 1984, Muhlberg 1984, Beringer and 

Nishimoto 1988, Slater et al. 1995). Recent estimates indicate that Black-legged 

Kittiwake populations have declined by more than 80% at this colony over the last 30 

years (Zador et al. 1997). 

Gull Island is located in Kachemak Bay on the eastern side of lower Cook Inlet. The 

island is 5 km southeast of the Homer Spit (59' 35' 10" N, 151' 19' 45" W) and is owned 

by the Seldovia Native Association. The island consists of four spires of hctured 
bedrock that erupt sharply from the water and are connected only at extreme low tides. 

We also conducted a limited amount of monitoring at 60-foot Rock (59" 33N, 15 1 O 

28W), a small rocky island about 6 km south of the Homer Spit, owned by AMNWR. 

Few birds have nested on 60-Foot Rock in recent years, so we concentrated our efforts on 

Gull Island. Black-legged Kittiwakes have been monitored at Gull Island and on 60-foot 

Rock by private consultants and AMNWR biologists periodically since 1976 (Erikson 

1976, Nishimoto et al. 1987, Nishimoto and Beringer 1989, 1990). Recent estimates 

indicate that Gull Island kittiwake populations have increased by at least 60% over the 

last 25 years (Zador et al. 1997). The Black-legged Kittiwake population at Gull Island is 

currently around 10,000 birds. Kittiwake populations at 60-Foot Rock have also 

increased by 20% over the last 15 years, and the current population is around 180 birds. 

The Barren Islands (58"55'N, 152"OOW) support the largest seabird populations in the 

northern Gulf of Alaska, including ca 12,000 Black-legged Kittiwakes (Bailey 1976). 

Details of seabird populations and the islands can be found in Bailey (1976) and in APEX 

reports by Roseneau et al. (1995,2000). There were no systematic plot censuses prior to 

EVOS funded work. 

Populations 

We monitored numbers of adult birds in population plots to obtain an index of population 

change among years and colonies. All 10 population plots used at Gull Island and 8 plots 

at Chisik Island were historic population plots established and monitored by AMNWR 

personnel. At Gull Island, we monitored 10 historical plots, while at Chisik, 5 new plots 

were established and monitored in addition to historical plots. Plots were counted every 

3-5 days between lOOOh and 1600h, from middle incubation to the start of chick fledging, 

when colony attendance is least variable (Byrd 1989). All population plots were counted 

using binoculars from a boat except for new plots on Chisik, which were counted from 

land (in blinds) using binoculars. Repeated counts of individual plots on a given day 

were treated as replicates, and their totals summed to obtain a single count for that day. 

Each of these "count-days" were treated as samples and averaged to obtain a mean 

population count for the season. 

Productivity 

We used productivity plots to collect data on reproductive parameters of kittiwakes. 

Each plot was selected from "viewable" sections of the colony, had clearly defined 

boundaries, and was used in all years of the study. We tracked individual nest sites 

within plots by using hand drawn maps or computer printouts of photographs taken with 

digital cameras. We drew plot boundaries and labeled nest sites with unique numbers on 

plot maps. Approximately 10 plots containing an average of 30 nest sites were monitored 

on the same day, every 3 days from the nest building stage through chick fledging. We 

considered chicks to be fledged at 32 days of age as little mortality is observed at the 

colony after this time. 

We observed the status of nests and nest contents from observation points on the island 

using binoculars (10x40,8.5~42). By observing nests and their contents on a fixed 

schedule we were able to obtain estimates of laying and hatching chronology, laying 
success, hatching success, fledging success, reproductive success, productivity, and 

clutch size. On some occasions predation events or siblicides were observed. We used 

study plot as the sample unit for estimating each parameter. The mean and standard 

deviation of the plot means were used for annual estimates. Reproductive parameters 

were defined as follows: 

Laying and hatching chronology (median lay and hatch dates) 

Laying Success (% of nest structures where 2 1 egg is laid) 

Hatching Success (% of eggs laid that hatch) 

Fledging Success (% of chicks hatching that fledged) 

Reproductive Success (% eggs laid that fledged chicks) 

Productivity (chicks fledged per nest structure) 

Mean Clutch Size (eggs per nest with eggs) 

Brood Size at Hatch (chicks per nest with chicks at hatch) 

Brood Size at Fledge (fledglings per nest with fledglings) 

We also obtained a productivity index in all years at Gull Island, and in 1997 and 1999 at 

Chisik Island. We conducted one colony-wide census of nest structures, during middle 

incubation, and another colony-wide census of large chicks during late chick rearing. We 

used the ratio of large chicks to original nest structures to obtain an index of productivity. 

Nest Attendance, Meal Delivery Rates, Foraging Trip Duration 

We measured kittiwake activity budgets to quantify feeding rates, foraging trip duration, 

and time spent at the nest. We conducted kittiwake activity watches from 0700-2100 on 

at least 3 different days at Gull and Chisik, and 2-7 days at the Barrens, during the chickrearing period. For each watch we chose a different group of 8- 10 nest sites that were 

highly visible and were representative of the colony in terms of brood status and 

chronology. The first watch was conducted when chicks were approximately 10 days of 

age and each successive watch was performed on chicks 7 to 10 days older than the 

previous watch. Prior to an activity watch, one adult from each nest was captured and 

marked, either with dye or unique color bands to distinguish among pair members. 

During each watch, observers recorded the time of arrivals and departures of each 

member of a pair associated with that particular nest site. This allowed us to quantify the 

total time spent at the nest site for each individual and generate a statistic termed "birdminutes per hour", or the combined number of minutes both pair members spent at the 

nest each hour. For example if one bird only was present at a particular nest site from 

0700-0800, then for that hour block and that nest site, total bird-minutes were equal to 60. 

If both birds of a pair were present for a complete hour block, then bird minutes were 120 

for that hour. If total bird-minutes were less than 60, then both adults were absent for 

some period of time, leaving the chick unattended. 

We also collected data on meal delivery rates. When a parent arrived at the nest site and 

subsequently fed a chick, the time that the bird arrived at the nest site was recorded as the 

meal delivery time. That meal may have been fed to the chick all at once or in many 

small boluses, but this was still considered to be one meal. From this data we calculated 
a meal delivery rate, or the number of meals delivered per nest per hour. From these 

same observations of meal deliveries we also calculated foraging trip durations. The time 

that an individual spent away hm the nest prior to having returned with a meal was 

considered to be a foraging trip bout. 

From preliminary analyses, we concluded that neither nest-site nor observation day 

contributed significantly to variability in behavioral parameters in a given year and so we 

used nest-site as the sample unit. We then calculated a mean per nest site per day for 

each behavioral parameter, and then a grand mean, to generate a parameter value for each 

colony in each year (colony-year). 

Chick Growth Rates 

We used designated areas of the colony to measure growth rates in each year of the study. 

Each area contained 5-10 nest sites with chicks. To minimize disturbance, we did not use 

these areas for other experimentation. We photographed growth rate areas and assigned 

individual nest numbers to each nest site. In order to obtain accurate ages of chicks, nests 

were checked daily just prior to their expected hatch dates. Growth rates on both chicks 

(if two present) in each nest were taken every 4 days. Just after hatching, chicks in twochick nests, were marked (using permanent marking pens on their heads and webbing of 

one foot) to distinguish between alpha and beta chicks. When chicks were large enough, 

we banded them with USFWS metal bands on the right leg. In 1998, at Gull Island, 

colony (royal blue) and cohort (yellow) bands were also affixed to the right leg before 

chicks fledged (colony, over USFWS metal, over cohort). Birds were not banded at the 

Barren Islands. 

The following growth and development measurements were taken for each nestling every 

four days: 

Headbill: The distance from the tip of the mandible in a straight line to the 

posterior edge of the cranium. 

Diagonal Tarsus: (right leg) The distance from the point of the joint between the 

tibialfibula (calf) and tarsus (foot) to the point of the joint between the 

tarsus and the base of the middle phalange (toe) in fiont (achieved by 

bending the foot up and the toes down and measuring diagonally fiom top 

of toes to the bottom of the heel). 

Flat Wing : (right wing) The distance from the bend of the wing (wrist) to the tip 

of the longest primary (tip of the developing teleoptile). We flattened and 

straightened the wing for this measurement. 

10th Primary: (right wing) The length of the outer (10th) primary (fiom 

emergence fiom skin to tip, down not included). 

Mass: Using a Pesola scale we recorded mass to the nearest gram. If the chick 

regurgitated before it was weighed, we weighed the regurgitation and 

added its mass to the mass of the chick. Before releasing the chick we refed it the regurgitation. In circumstances that the chick refused to accept 

the regurgitation, it was collected and used as a chick diet sample. No 
more than one regurgitation was collected from an individual chick in a 

season. 

Fledging Wt.: We measured "fledglings" (day 30 post-hatch, " 1 day) body 

weight, wing length, and outer (10th) primary for a minimum sample of 40 

broods. 

We calculated growth rates as the slope of the linear regressions of mass versus age 

during the linear phase of growth, defined as falling between 6-22 days of age or between 

60-300 g of mass. For calculating mean growth rate in a given year, we treated each 

chick as an individual sample unit. We also calculated growth rates for alpha and 

singleton chicks pooled, and beta chicks. 

Adult Body Condition 

We captured breeding adult kittiwakes to obtain an estimate of their body condition. We 

captured birds at the nest using a 9 m telescoping noose pole. Birds were sampled at predetermined intervals from the pre-laying stage through chick fledging. We did not 

capture birds in 1995 and only a limited number in 1996, however, in 1997- 1999 we 

attempted to capture a minimum of 7 birds during 6 sampling windows throughout 

breeding: pre-laying, early, middle, and late incubation, and early, middle, and late chick 

rearing. Few birds were captured during the pre-lay stage, as birds proved difficult to 

capture when not protecting nest contents. Captured birds were measured as with 

kittiwake chicks, excluding measurements for loh primary length (see Chick Growth 

section). Immediately after capture and prior to measuring, a small blood sample was 

taken for genetic sexing. (For detailed methods of blood collection techniques, see 

Kitaysky et al. 1999a). At Gull and Chisik islands we banded each bird with a colony 

color band over a metal USFWS band on the right leg and a unique 3-band color 

combination on the left leg. Banding of birds prevented recaptures, enabled re-sighting 

of individuals for the study of over-winter survival (results not presented here), and for 

studies of nest attendance patterns (see below). We used the ratio of wing length to body 

mass as an index of body condition. 

Chick Diet 

To assess chick diet composition we collected chick regurgitations every 4 days during 

the chick-rearing period, when chicks were 10 to 30 days old. Many of these samples 

were collected from chicks used for chick growth studies, however no more than one 

sample was collected from any individual chick (except at Barrens). Regurgitations were 

also taken from adults that were bringing back food for their chicks. Other samples were 

collected as part of a dedicated effort to collect diet samples from non-growth rate chicks. 

These samples were collected at random from accessible nests. Diet samples were stored 

in Whirl-PaksB labeled with the date, time, colony, nest identification number, and the 

fresh weight of the sample and then frozen for later analysis of composition. We 

weighed samples (nearest 0.01 gram), prior to freezing, on an Ohaus electronic scale. 

Samples were analyzed for composition and proportional biomass at the University of 

Alaska Fairbanks by Alan Springer and Kathy Turco. 
Energy Provisioning Rates 

A sub-sample of complete chick meals were analyzed for composition and energy content 

(KJ I g) by Patrick Jodice and Daniel Roby of the Cooperative Fish and Wildlife Unit at 

Oregon State University, Corvalis, Oregon. Used in conjunction with meal delivery rates 

determined in this study, it was therefore possible to calculate energy provisioning rates 

(KJ I nest day). 

Adult Diet 

We obtained adult diet samples by collecting stomachs from adult breeding birds at each 

colony. We collected 7- 10 adult kittiwakes with a shotgun adjacent to the breeding 

colony during the late chick rearing period. In most cases birds were weighed and 

measured prior to being frozen, however, in some instances birds were frozen, later 

thawed, and measurements taken during the necropsy process. During necropsies, birds 

were weighed and measured, scored for fat, sexed, aged, breeding status determined by 

brood patch stage, and stomachs were removed. Measurements were taken following 

methods described in "Adult Body Condition" section. Stomachs were preserved in ethyl 

alcohol for later analysis of diet composition from fish otoliths. Samples were analyzed 

for composition and proportional biomass at the University of Alaska Fairbanks, by Alan 

Springer and Kathy Turco. Tissue samples were also taken fiom the liver, heart, and 

breast muscle for stable isotope analysis. 

Stress hormone levels 

We measured circulating levels of stress hormone (corticosterone) in the blood of adult 

kittiwakes throughout the breeding season. This study was initiated on a small scale in 

1996 and in subsequent years an intensive effort was sustained through the course of the 

breeding season. From 1997- 1999, samples were taken from 6 stages of the breeding 

cycle as described in the section on "Adult Body Condition". For some sampling periods 

we measured baseline circulating levels of corticosterone, while for others we conducted 

a full "stress series" (See Kitaysky et. al. 1999 for detailed methods of blood collection 

and analysis procedures). We present only data for baseline corticosterone levels in this 

report 

Results and Discussion 

Population 

We monitored annual variability and trends in population size with counts of birds in 

designated plots (Table 10.1). Population plot count windows are given in Appendix 

10.1. There were no obvious trends during the five years of this study, although 

kittiwakes declined considerably at Chisik Island. When these data are viewed in context 

of historical plot and whole-island counts conducted prior to 1995, however, the 

population at Gull Island appears to have stabilized in recent years, while the population 

at Chisik Island continues to decline (Appendices 10.2 and 10.3). At Gull Island, 

populations increased dramatically (+8.8% per annum) from 1976 to 1988, and since then 

(1 989-1999) numbers have been remarkably stable (essentially no change in 10 years). 

We believe that kittiwake breeding habitat is saturated on Gull Island. It is a small island, 

and it appears that every cliff ledge, nook and cranny is in use by breeding kittiwakes. In 
contrast, kittiwakes continue in a long (1 97 1 - 1999) steady (-4.3% per annum) decline in 

number at Chisik Island. Cliff habitat once occupied by breeding bird* as evidenced by 

old nest cups or xanthophyllous lichens- is becoming more abundant on Chisik Island. 

At the Barrens there are no long-term historical data. However, plot counts conducted 

since 1993 suggest that populations have increased (+5.2% per annum) at the Barrens 

(Roseneau et al. 1995,2000). A different set of kittiwake plots at the Barrens counted 

from 1989 to 1992 also suggest an increase (+8.6%) in kittiwakes (Dipple and 

Nysewander 1992, Nysewander and Byrd, unpubl. data), although counts were highly 

variable and the trend is not statistically significant. 

Productivity 

Black-legged Kittiwake productivity (chicks fledged per nest structure) averaged for all 

colony years, was highest at Gull Island (mean4.48) and lowest at Chisik (mean4.02). 

Productivity at the Barrens was similar to that at Gull Island (mean4.43) (Table 10.2). 

Productivity was lowest in all years at Chisik. Variation in productivity among years was 

greater at the Barrens (0.04-0.72) than at Gull (Gull 0.34-0.65) or Chisik (0.00-0.04). 

Productivity varied inconsistently among colonies in a given year, except for 1998 when 

productivity was the lowest of any year at all three colonies. This was likely due to 

anomalous water conditions associated with an El Nino Southern Oscillation (ENSO) 

event of 1997- 1998 (Piatt et al. 1999). Warm sea-surface temperatures developed 

rapidly during June in the GOA and persisted until MayIJune of 1998. Despite the ENS0 

event and resulting reduction in food supply throughout the GOA, kittiwakes at Gull 

Island still produced 0.32 chickdpair, while they failed reproductively at Chisik and the 

Barrens. This is indicative of the stability of the oceanographic conditions and food 

supply in Kachemak Bay relative to other areas of Cook Inlet (Chapter 2,3). 

As an adjunct to measures of productivity gathered from intensive study plots, we also 

obtained an "index of productivity" at Gull Island in each year, and in two years at Chisik 

Island (1997 and 1999) (Table 10.11). This was based on an all-island nest census 

conducted in mid-incubation and another census of chicks during late chick-rearing. The 

index of productivity was similar to productivity estimates derived from intensive plot 

monitoring (I? = 0.91 ; plot estimate = 1.04[index estimate]). 

Mean laying success (Table 10.3) and clutch size (Table 10.4) were similar among 

colonies, with Gull slightly higher than the Barrens, which was in turn higher than 

Chisik. In some years, however, laying success and clutch size were higher at Chisik 

than at the other colonies. Hatching success was similar between Gull and the Barrens, 

and both were much higher than at Chisik (Table 10.5). In contrast, brood size at hatch 

(number of chicks hatched per nest with chicks) was highest at Chisik Island (Table 

10.6). Fledging success was highest at Gull island and very low at Chisik, where almost 

no chicks have fledged successfully in the last five years (Table 10.7). Brood size at 

fledge (chicks fledged per nest with fledged chicks) followed the same pattern (Table 

10.8). 

The median date of egg-laying varied over 1 1- 19 days in June depending on the colony 

(Table 10.9). For all three colonies, median egg-laying occurred between 5 June and 29 
June. Median lay date was earliest on average at Chisik (mean = 12 June), two days later 

at Gull, and two days later again at the Barrens. Within a season at each colony, median 

hatching tended to be more synchronous than median lay (Table 10.10). Median hatch 

ranged from 2 July - 28 July among colonies. Median hatch was also earliest at Chisik 

and latest at the Barrens, but hatching phenology differed by 4-5 days among colonies. 

Thus, on average, Black-legged Kittiwakes initiated nesting earliest at Chisik Island and 

latest at the Barrens Islands. This consistent pattern may be related to environmental 

regimes: At any given time, water temperatures are warmest at Chisik Island and coldest 

at the Barrens (See Chapter 2). These differences in temperature may influence the timing 

of peaks in plankton and forage fish production, which in turn, may influence timing of 

breeding in kittiwakes. 

In summary, productivity parameters were generally highest for Gull Island, and lowest 

for Chisik Island. Productivity parameters measured early in the season (laying success 

and clutch size) were similar among colonies, but as the season progressed, disparities in 

breeding success among colonies became more pronounced. Productivity varied 

inconsistently among colonies in any given year. Although Gull Island had the highest 

average productivity for all years, kittiwakes at the Barrens were considerably more 

productive in 1995 and 1996. In 1998, productivity parameters were depressed at all 

three colonies, presumably in response to the 1997- 1998 ENS0 event. By any standard, 

kittiwakes at Chisik island failed in all years of study (Irons 1996), presumably owing to 

a lack of food (Robards et al. 1999, Kitaysky et al. 1999b). Relationships between 

reproductive parameters and food supply are examined in Chapter 14. 

Colony Attendance, Feeding Rates, and Foraging Trip Durations 

We collected data on colony attendance, feeding rates, and foraging trip durations in all 

years when a sufficient sample size of nests with chicks were available for behavioral 

watches. Attendance (mean bird-minutes per hour) was lowest at the Barren Islands and 

highest at Gull Island (Gull mean=59.8; Chisik mean=57.7; Barrens mean=54.3) (Table 

10.12). Chick feeding rates were highest at Gull Island and lowest at Chisik (Gull 

mean=0.22; Barrens mean=O. 18; Chisik mean=O. 13)(Table 10.13). Chick feeding rates 

were more variable among years at the Barren Islands than at Gull or Chisik. Foraging 

trip durations were similar at Chisik and the Barren islands, but much shorter at Gull 

Island (Gull mean=196.4; Chisik mean=308.3; Barrens mean=3 14.8) (Table 10.14). 

Differences among colonies were consistent among years and appear to reflect 

differences in foraging effort and range (Chapter 8). Attendance and feeding rates were 

always highest, and foraging trip durations were always shortest at Gull Island- where 

foraging occurred with a few krn of the colony (Chapter 8). Foraging trips were long at 

the Barren islands, because birds had to travel to distant foraging grounds along the 

Kenai Peninsula (Chapter 8). Despite this, Barrens birds managed to maintain adequate 

food deliveries to chicks because food supplies were plentiful along the Kenai Peninsula 

(Chapters 4 and 7). Birds from Chisik traveled longer and further than those from Gull or 

the Barrens (Chapter 8), but were incapable of locating adequate food supplies. 
Chick Growth 

We were not able to obtain growth rate measurements at Chisik Island in 1995, 1998, and 

1999 because of reproductive failure. Chick growth rates were highest at the Barrens and 

lowest at Chisik Island (Table 10.15). Chick growth rates did not reflect differences in 

feeding rates and foraging trip durations. Growth rates at Chisik and Gull Island were 

similar in 1997, despite a large difference in productivity (Gull 0.60, Chisik 0.02 

chickstnest). One explanation is that the only chicks to fledge successfully at Chisik in 

1997 were hm the best quality parents and so they had relatively high growth rates. For 

related reasons, adults that cannot adequately feed young probably also leave them 

unattended and vulnerable to predation. So basically, if a chick survives to be measured 

by us, it is likely to be a well-fed chick. These results suggest that chick growth rates are 

poor indicators of food supply- not because starving birds are unusual, but rather 

because they tend to get eaten by predators, leaving a biased sample of well-fed birds to 

measure. 

Adult Stress Hormone Levels 

We measured circulating levels of corticosterone (stress hormone) in the blood of adult 

kittiwakes throughout the breeding season, from 1997- 1999. Baseline levels of 

corticosterone (ng/ml) were slightly higher on average at Chisik Island, than at Gull 

Island (Table 10.16). If we compare stress hormone levels just during chick rearing at 

both colonies, the differences are greater (Gull mean=8.4, Chisik mean=12.2). In general, 

baseline stress levels increased during the season and particularly during late chickrearing in most years it was measured. Because kittiwakes at Chisik often failed during 

the chick-rearing period, we were not always able to collect samples. Gull Island birds 

had higher baseline levels of corticosterone in 1998, when productivity was very low, 

than in either 1997 or 1999, when productivity was very high. Overall, baseline stress 

levels were not as high as we had predicted at Chisik, the food deprived colony, probably 

because birds there suppress their baseline stress response wtaysky et al. 1999a). A full 

analysis of stress in breeding kittiwakes during 1997-2001 at Gull and Chisik islands is 

currently under way (Kitaysky et al., in prep.). 

Chick Diets 

Chick meals consisted largely of sand lance (Ammodytes hexapterus) at Gull, Chisik and 

Barren islands (Table 10.17). Pacific herring (Clupea harengus pallaszj was the next 

most important prey at Gull and Barren islands, while smelts made up the second largest 

proportion of diet biomass at Chisik. Chick diet composition is shown in detail in 

Appendices 10.1-10.2. Chick meal size was highest at the Barren Islands, slightly lower 

at Gull Island, and the lowest at Chisik Island (Table 10.18). Taking into consideration 

meal size and composition, overall energy provisioning rates (KJ / nest day), were 

highest at Gull Island and below the minimum required for growth at Chisik (Romano 

2000). Kittiwake chicks fed on lower quality diet- or in amounts that impair 

physiological development- have reduced growth and fitness wtaysky et al. 1999, 

Romano 2000). 
Adult Diet 

Adult kittiwake diet varied much more so than chick diets among colonies (Table 10.19), 

and better reflected the local composition of prey stocks (Chapters 4,5). Gull and Chisik 

Island birds fed primarily on sand lance (greater than 50% composition), but consumed 

significant proportions of osmerids (smelt at Chisik, capelin (Mallotus villosus) at Gull), 

invertebrates (mostly euphausiids), gadids (cod), and a wide variety of other fish. At the 

Barren Islands, adult kittiwakes fed primarily on walleye pollock (Theragra 

chalcogramma) (greater than 35% composition), capelin, sand lance and a significant 

fraction of other prey (see also Appendices 10.8-10.10). There were few apparent trends. 

Capelin increased in the diet of kittiwakes at Gull and Chisik Islands fiom 1995 to 1999, 

but were absent from the diet of Barren Island birds in 1999. In general, adult diets were 

more diverse than chick diets, and contained a much higher proportion of low quality 

prey such as cod and pollock (van Pelt et al. 1997). 

Adult Body Condition 

Adult body condition was measured at all three colonies fiom 1997-1999 (Tables 10.20 - 

10.22). The index of adult body condition (mass 1 wing) ranged from 1.1 1 to 1.38 among 

capture bouts, and from 1.24 to 1.30 among colony years. Mean body condition for all 

years was similar among colonies. Body condition did vary slightly within a colony and 

among years, but it is not clear how this relates to other breeding parameters. It is likely 

that body condition is influenced by many different factors and requires careful 

interpretation. When foraging conditions are poor, birds may acquire a large fat reserve 

as a buffer. However, in some instances a large fat reserve may reflect an abundance of 

food. These are two obviously very different scenarios that could both yield high body 

condition indices. One clear result is that body condition declined seasonally in all years 

at Chisik, while at Gull and the Barren islands, it tended to fluctuate through the season. 

This seasonal decline in body condition at Chisik parallels the observed seasonal declines 

in reproductive performance. 

Conclusion 

The main purpose of this chapter was to document methods used to collect data on Blacklegged Kittiwakes and to summarize the main results of our studies on this species. The 

ultimate objective is to interpret how various parameters of kittiwake biology and 

behavior vary with food supply. To that end, a preliminary synthesis on the response of 

kittiwakes to fluctuations in food supply is presented in Chapter 14. Results presented in 

this chapter will be further analyzed and submitted for publication in peer-reviewed 

journals. 

The work presented here is the product of many dedicated employees and volunteers. 

Stephani Zador was responsible for initiating field work on Gull Island in 1995, and over 

the years 1995- 1997, was instrumental in helping to develop and refine protocols for 

kittiwake data collection at all three colonies (in concert with Arthur Kettle, who led field 

work on the Barren Islands in 1995-1999. See Roseneau et al. 2000 for acknowledgments 

of support for Barrens work). Tom Van Pelt was instrumental in providing field work, 
camp support, and logistic coordination throughout the project. We thank Yumi 

Arimitsu, Jeb Benson, Dave Black, Leigh Ochikubo [Chan], Alice Chapman, Jared 

Figurski, Mike Gray, Greg Hoflhan, Brad Keitt, Roman Kitaysky, April Nielsen, Ram 

Papish, Mike Post, Brian Smith, Shiway Wang, Jenny Wetzel, and Sadie Wright for their 

vital help with field work. We are grateful to Vernon Byrd, and Brian Smith for their 

assistance in compiling the data archive. Sasha Kitaysky shared his research expertise, 

comradeship, and wisdom with us. Greg Snedgen gave abundant practical and logistical 

help that greatly increased the safety and efficiency of our work. Brad Keitt is thanked 

for refitting the RN David Grey, and we thank Greg Snedgen for running the boat during 

the 1997-1999 field seasons. We thank Vem Byrd and the staff of the Alaska Maritime 

National Wildlife Refuge for their tremendous logistic support and hospitality in Homer. 

Finally we thank Mike Gaegel and staff of the Kasitsna Bay Marine Lab, the residents of 

Chisik Island, Tuxedni Channel, Halibut Cove, and Kasitsna Bay, for their support. 

Literature Cited 

Aebischer, N.J., Coulson, J. and Colebrook, J. M. 1990. Parallel long-term trends across 

four marine trophic levels and weather. Nature 347:753-755. 

Bailey, E. P. 1975a. Barren Islands survey notes, 1974-1975. Unpubl. Fieldnotes, 1975. 

U.S. Fish Wildl. Serv., Homer, AK. 

Bailey, E.P. 1975b. Breeding bird distribution and abundance in the Barren Islands 

Alaska. Unpubl. Rept., 1975. U.S. Fish Wildl. Serv., Homer, AK. 

Bailey, E. P. 1976. Breeding bird distribution and abundance in the Barren Islands, 

Alaska. Murrelet 57:2-12. 

Beringer, B. and M. Nishimoto. 1988. The status of breeding seabirds at Chisik and Duck 

Islands during the summer of 1987. Unpayable. rep., U.S. Fish and Wildl. Serv., 

Alaska Maritime Natl. Wildl. Refuge, Homer, AK. 12 pp. + appendix. 

Byrd, G.V. 1989. Seabirds in the Pribilof Islands, Alaska: trends and monitoring 

methods. M.S. thesis, Univ. of Idaho. 

Croxall, J.P., McCann, T.S., Prince, P.A. and Rotherry, P. 1988. Reproductive 

performance of seabirds and seals at South Georgia and Sigmy Island, South 

Orkney Islands, 1976- 1987: Implications for southern ocean monitoring studies. 

Pp. 267-285 In Sahrhage, D. (ed.) Antarctic ocean and resources variability. 

Springer-Verlag, Berlin. 

Dipple, C. And D. Nysewander. 1992. Marine bird and mammal censuses in the Barren 

Islands, 1989 and 1990, with specific emphasis on species potentially impacted by 

the 1989 Exlcon Valdez, including supplemental appendices for 199 1 murre data. 

Unpub. Rept., U. S. Fish Wildl. Serv., Homer, AK. 7 lpp. 

Erikson, D. 1976. Distribution, abundance, migration and breeding locations of marine 

birds in Lower Cook Inlet, Alaska. Vol. 8. In Trasky, L.L., L.B. Flagg and D.C. 

Burbank, eds. Environmental studies of Kachemak Bay and Lower Cook Inlet. 

Unpayable. adrnin. rep., AK. Dep. Fish and Game, MarineICoastal Habitat 

Manage. Anchorage. 

Furness, R.W., Greenwood, J.J.D. and Jarvis, P. 1993. Can birds be used to monitor the 

environment? Pp. 1-41. In Furness, R. W. and Greenwood. J.J.D. (eds.), Birds as 

monitors of environmental change. Chapman and Hall, London. 
Irons, D.B. 1996. Size and productivity of Black-Legged Kittiwake Colonies in Prince 

William Sound before and after the Enon Valdez oil spill. American Fisheries 

Society Symposium 18:738-747. 

Jones, R.D., M.R. Petersen, C. Slater and J. Burke-Ogan. 1980. The pelagic birds of 

Chisik and Duck Islands. Final report. U.S. Fish and Wildl. Serv., Biological 

Serv. Prog., Anchorage, AK. 33 pp. 

Kaflca, D.M. 1984. Kittiwake productivity on Chisik and Duck Islands, Cook Inlet, 

Alaska. Unpayable. rep., Univ. of AK., Fairbanks. 14 pp. 

Kitaysky, A.S., J.F. Piatt, J.C. Wingfield, M. Romano. 1999. The adrenocortical stressresponse of Black-legged kittiwake chicks in relation to dietary restrictions. J 

Comp Physiol B (1999) 169:303-3 10. 

Kitaysky, A.S., J.C. Wingfield, and J.F. Piatt. 1999. Dynamics of food availability, body 

condition and physiological stress response in breeding Black-legged Kittiwakes. 

Functional Ecology 13577-584. 

Kushlan, J.A. 1993. Colonial waterbirds as indicators of environmental change. 

Colonial Waterbirds 16:223-25 1. 

Manuwal, D.A. 1978. Dynamics of marine bird populations on the Barren Islands, 

Alaska. Unpubl. Environ. Assess. Alaska Contin. Shelf, Annu. Repts. Princ. 

Invest. Minerals Manage. Serv., Anchorage, AK. 97pp. 

Manuwal, D.A. 1980. Breeding biology of seabirds on the Barren Islands, Alaska. 

Unpubl. Repts. U.S. Fish Wildl. Serv., Off. Biol. Serv., Anchorage, AK 195pp. 

Manuwal, D.A. and D. Boersma. 1978. Dynamics of marine bird populations on the 

Barren Islands, Alaska. Pp. 575-679. in Environ. Assess. Alaska Contin. Shelf, 

Annu. Repts. Princ. Invest., Vol3. NOAA Environ. Res. Lab, Boulder, CO. 

Muhlberg, G. 1984. Chisik and Duck Islands report (draft). Unpayable. rep., U.S. Fish 

and Wildl. Serv., Anchorage, AK. 

Nishimoto, M. and B. Beringer. 1989. Breeding seabirds at Gull Island and Sixty-foot 

Rock during 1987-88. Unpayable. admin. rep., U.S. Fish and Wildl. Serv., Homer, 

AK. 24 pp. + appendices 

Nishimoto, M. and B. Beringer. 1990. Breeding seabirds at Gull Island and Sixty-foot 

Rock during 1989. Unpayable. admin. rep., U.S. Fish and Wildl. Serv., Homer, 

AK. 

Nishimoto, M., D. Debinski, K. Rose and K. Thounhurst. 1987. Breeding seabirds at Gull 

Island and Sixty-foot Rock during 1984-86. Unpayable. admin. rep., U.S. Fish 

and Wildl. Serv., Homer, AK. 19 pp. + appendices. 

Nysewander, D. and C. Dipple. 1990. Population surveys of seabird nesting colonies in 

Prince William Sound, the outside coast of the Kenai Peninsula, Barren Islands, 

and other nearby colonies, with emphasis on changes of numbers and 

reproduction of murres. Bird Study No. 3. Final rept., U.S. Fish Wildl. Serv., 

Homer, AK. 70pp. 

Nysewander, D. and C. Dipple. 1991. Population surveys of seabird nesting colonies in 

Prince William Sound, the outside coast of the Kenai Peninsula,, Barren Islands, 

and other nearby colonies, with emphasis on changes of numbers and 

reproduction of murres. Bird Study No. 3. Final rept., U.S. Fish Wildl. Serv., 

Homer, AK. 40pp. 
Piatt, J.F., C.J. Lensink, W. Butler, M. Kendziorck, and D. Nysewander. 1990. Immediate 

impact of the Exxon Valdez oil spill on marine birds. Auk 107: 387-397. 

Piatt J.F., and P.J. Anderson. 1996. Response of Common Murres to the Exxon Valdez 

oil spill and long-term changes in the Gulf of Alaska marine ecosystem. Pp. 720- 

737 in: Exxon Valdez Oil Spill Symposium Proceedings. Rice, S.D., RB. Spies, 

D.A. Wolfe and B.A. Wright (Eds.). American Fisheries Society Symposium 18, 

Bethesda, Maryland. 

Piatt, J.F., G. Drew, T.I. Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711998 ENS0 event in lower Cook Inlet, 

Alaska. PICES Scientific Report No. 10:93- 100. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fish Bull. 

97(4):962-977. 

Romano, M.D. 2000. Effects of diet on growth and development of nestling seabirds. 

M.Sc. Thesis, Oregon State University, Corvallis Or. 59pp. 

Roseneau, D.G., A.B. Kettle, and G.V. Byrd, 1995. Common murre restoration 

monitoring in the Barren Islands, 1993. Restoration Project No. 93049. Unpubl. 

final rept., U.S. Fish Wildl. Serv., Homer, AK. 

Roseneau, D.G., A.B. Kettle, and G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 

00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 

Slater, L., J.W. Nelson, and J. Ingrum. 1994. Monitoring studies of lower Cook Inlet 

seabird colonies in 1993 and 1994. U.S. Fish and Wildl. Serv. Rep., AMNWR 

94/17. Homer, AK. 43 pp. 

Snarski, D.A. 1970. Kittiwake ecology, Tuxedni National Wildlife Refuge. Alaska Coop. 

Wildl. Res. Unit. Quarterly Rep. July-September 22: 10- 13. 

Snarski, D.A. 1971a. Kittiwake ecology, Tuxedni National Wildlife Refuge. Alaska 

Coop. Wildl. Res. Unit. Quarterly Rep. July-September 21 : 6-8. 

Snarski, D.A. 1971b. Kittiwake ecology, Tuxedni National Wildlife Refuge. Alaska 

Coop. Wildl. Res. Unit. Quarterly Prog. Rep. Jan-March 22: 15-23. 

Snarski, D.A. 1971c. Seabird colony data sheet for Tuxedni National Wildlife Refuge. 

Unpublished. 

Snarski, D.A. 1974. Some aspects of the ecology of the black-legged kittiwake during 

two years of nesting failure. Univ. Alaska., Coop. Wildl. Research Unit, 

Fairbanks. Thesis manuscript. 38 pp. 

Sowls, A.L., S.A. Hatch, and C.J. Lensink. 1978. Catalog of Alaskan seabird colonies 

U.S. Fish and Wildlife Service FWSIOBI - 78/78. Washington, D.C. 

Van Pelt, T., J.F. Piatt, B.K. Lance, and D.D. Roby. 1997. Proximate composition and 

energy density of some North Pacific forage fishes. Comparative Biochemistry 

and Physiology 1 18(A): 1393- 1398. 

Zador, S. G., A. Harding, J.G. Piatt, L. Ochikubo, and A.A. Nielsen. 1997. Monitoring 

populations and productivity of seabirds at colonies in lower Cook Inlet, Alaska, 

1995. USGS Final Rep. To Minerals Management Service, Anchorage, AK. 
Chapter 11. Pigeon Guillemot Biology in Kachemak Bay 

Michael Litzow 

Introduction 

Pigeon Guillemots (Cepphus columba) are loosely colonial breeders, able to raise two 

chicks to adult weight in the nest, and forage near shore on a diverse diet that includes 

invertebrates, demersal fish and pelagic fish (Ewins 1993). Approximately 680 oiled 

Pigeon Guillemot carcasses were recovered following the Exxon Valdez oil spill (Piatt et 

al. 1990) and this number probably represents 10 - 30% of total Pigeon Guillemot 

mortality hm the spill (Piatt et al. 1990, Piatt and Ford 1996). A variety of studies have 

shown that Pigeon Guillemot have experienced more persistent oil spill effects than other 

bird species in Prince William Sound (Osenberg et al. 1994, Wiens and Parker 1995, 

Murphy et al. 1997). As of 1998 guillemot populations in oiled areas of Prince William 

Sound were roughly one third of pre-spill levels, while populations in unoiled areas were 

similar to pre-spill levels (Irons et al. 2000). Further, guillemot populations at six oiled 

islands in Prince William Sound have declined fiom 1990 to 1998, while the population 

at an unoiled site in the Sound has increased over the same time period (Golet et al. in 

press). Adult Pigeon Guillemots in oiled areas of the Sound were still apparently being 

exposed to residual oil in 1999, as indicated by elevated levels of the enzyme CYPlA in 

livers of birds fiom oiled areas (Golet et al. in press). However, these authors concluded 

that the toxic effects of residual oil alone were probably not sufficient to explain 

population-level oil spill effects that have persisted for a decade. 

Another hypothesis to explain persistent oil-spill effects centers on the role that food 

availability may play in recovery. Populations of lipid-rich forage fish in the Gulf of 

Alaska declined rapidly during the late 1970s and 1980s due to changes in oceanographic 

conditions (Anderson and Piatt 1999). These changes in food availability may have 

resulted in population declines for high trophic level predators (Piatt and Anderson 1996, 

Memck et al. 1997), and Pigeon Guillemots may have been among the species affected 

(Hayes and Kuletz 1997). Further, populations of Pacific sand lance (Ammodytes 

hexapterus), a high-lipid fish that is a favored prey of guillemots, may have been reduced 

by the oil spill (Golet et al. in press and references therein). These changes in food 

availability might have slowed recovery of guillemots from population-level oil spill 

effects by reducing the ability of the population to replace oil-killed breeders with new 

recruits (Piatt and Anderson 1996, Golet et al. in press). 

As part of apex predator studies funded by the Exxon Valdez Oil Spill Trustee Council, 

we studied Pigeon Guillemot foraging ecology and reproductive biology in Kachemak 

Bay during 1996- 1999. These followed up on previous studies of guillemot biology and 

diets in Kachemak Bay in 1994- 1995 (Prichard 1997). The objective of our study was to 

assess the role that food availability plays in determining Pigeon Guillemot reproductive 

success. Specifically, we hypothesized that: (I) Pigeon Guillemot chick diets reflect 

spatial and temporal patterns of local prey availability, and (2) Pigeon Guillemot 

reproductive success increases with access to abundant lipid-rich forage fish. Our results 
in testing these two hypotheses are reported elsewhere (Litzow et al. 1998,2000,2002, 

Litzow 2000, Litzow and Piatt 2002). 

The purpose of this chapter is to summarize the methods and results of our study in a 

format useful to other researchers who are interested in the Kachemak Bay population of 

Pigeon Guillemots. Our findings provide a baseline data set that will allow assessment of 

the impact of future natural or anthropogenic changes on that population. In addition to 

our data from 1996-1999 we present data fiom the same area that were collected by Alex 

Prichard during 1995 for his Master's thesis at the University of Alaska, Fairbanks 

(Prichard 1 997). 

Methods 

Study area 

We collected data in Kachemak Bay (59" N, 15 1" W), which is located on the east shore 

of lower Cook Inlet. Pigeon Guillemots nest in approximately 30 small colonies (sensu 

Ewins 1985) of 2 - 15 nests each and in numerous solitary sites on the south shore of 

Kachemak Bay. The bay is bisected into oceanographically distinct inner and outer 

sections by the Homer Spit (Fig. 14.1). The Outer Bay is dominated by input hm the 

Gulf of Alaska and is well mixed and relatively cold and saline, while the Inner Bay is 

influenced by river runoff and tends to be more stratified, wanner, and less saline 

(Abookire et al. 2000). These oceanographic differences create important differences in 

foraging ecology for Pigeon Guillemots nesting in the two areas; breeders in the Inner 

Bay have access to more high-lipid schooling fish than those in the Outer Bay (Abookire 

et al. 2000, Litzow et al. 2000). The basis of our study was to compare differences in 

reproductive biology between the two areas. We studied nests in ten main colonies (Fig. 

1 1. I), as well as many other nests that were solitary or in small groups. We considered 

pairs nesting at China Poot Bay, Moosehead Pt., Peterson Bay, Halibut Cove and Mallard 

Bay to be the Inner Bay population, and all others to belong to the Outer Bay population. 

Population monitoring 

We monitored Pigeon Guillemot populations with two techniques: once-annual surveys 

of the south shore of Kachemak Bay and replicated censuses at known colonies during 

incubation and early chick rearing. Annual shoreline surveys followed methods of 

Sanger and Cody (1 994) and were conducted between 25 May and 1 1 June. In 1995 

counts were made within one hour of an afternoon high tide, and during 1996- 1999 

counts were made within two hours of a morning high tide. We surveyed guillemots 

hm a skiff travelling 48 knots approximately 50 m hm shore. All Pigeon Guillemots 

on land and within 100 m of shore were counted. Surveys began at the entrance to 

Seldovia harbor and ended at the un-named point near Chugachik I. that forms the 

northernmost point of Bear Cove. The coast of all islands and mainland in this area was 

surveyed, excluding Tutka Bay and Sadie Cove. 

We conducted colony censuses during incubation and early chick rearing (29 May - 9 

July) at 26 colony sites (Figure 14.2). The borders of these colony sites are pictured in 

Appendix 14.1. Counts were made within two hours of a morning high tide, and we 
counted all guillemots on land and within 100 m of shore. At most sites we counted 

guillemots for a set time (Table 14.1) and we recorded the highest number of guillemots 

present in the census site during that time, including birds that flew through the site. At 

larger sites (Table 14.1) we counted guillemots from a moving skiff, travelling 4-8 knots 

approximately 50 m from shore. We made two replicate counts at each of these sites, and 

again retained the highest accurate count. At four of these moving count sites (Guillemot 

Meadows, Seldovia Bay, Seldovia Pt., and Hesketh I.) one observer counted guillemots 

on land and inshore of the boat and another observer counted guillemots between the boat 

and a point 100 m from shore. At the other two sites (the Motherlode and Mallard Bay) 

we found it easier for the two observers to cooperate in keeping a running tally of all 

guillemots in the census site as the boat moved through the area. All population counts 

were made when conditions (i.e. weather, sea state, visibility) were good enough to 

ensure that we weren't missing any birds. 

To compare our census results among years we aggregated eleven individual sites into 

five larger census areas (Seldovia Bay, Hesketh I., Yukon I., Neptune Bay, Moosehead 

Pt.; Table 14.1). We pooled counts made at all of the smaller census sites in an area on a 

given day into a single replicate count for that area. The eleven individual sites were 

consistently sampled during 1996- 1999, and the resulting five areas give good spatial 

coverage for the guillemot population on the south shore of Kachemak Bay. 

Chick diet 

Pigeon Guillemots carry single fish in their bills when provisioning chicks, and usually 

rest on the water in front of the colony before delivering to the nest, making prey 

identification relatively easy. We collected data for at least one year at each of ten 

guillemot colonies (Fig. 14.1). We observed chick provisioning at two to five nests 

during feeding watches. Watches were conducted during 3.5 h shifts distributed evenly 

across different tide stages and times of day (0600-2000) in 1995 (n = 30 nests). From 

1996 to 1999 we conducted all-day watches (0600-2200 or 0500-2300; n = 22 nests in 

1996,26 in 1997,24 in 1998, 15 in 1999). Provisioning adults were observed from 

anchored boats (using binoculars) or from blinds (using telescopes). Study colonies were 

all in areas of moderate to high boat traffic, and the presence of an anchored boat had no 

apparent effect on the behavior of observed birds. Each chick meal was identified to the 

lowest possible taxonomic level, and we estimated the length of chick meals relative to 

the length of an adult guillemot bill, in multiples of half bill-lengths. Prey categories 

included Pacific sand lance (Ammodytes hexaptens), salmonid (Salmonidae), sculpin 

(Cottidae), gadid (Gadidae), flatfish (Pleuronectidae), gunnel (Pholidae), Lumpenus 

prickleback (Lumpenus spp.), ronquil (Bathymaster signatus, Ronquilus jordani), arctic 

shanny (Stichaeus punctatus), unidentified blenny (Blennioidea), and hermit crab 

(Anomura). Schooling prey species have a distinctive silver color, and we placed prey 

items that we could not positively identify into "unidentified schooling fish" and 

"unidentified demersal fish" categories. Other items were simply "unidentified". 

We also recorded a variety of ancillary data: the direction that a guillemot arrived from 

when coming to the colony with a meal, the time of day that the bird landed at the colony, 

delivered the meal, landed on the water after delivery, and again departed the colony, and 
the direction that a bird flew away fiom the colony after delivering. We consistently 

recorded times of arrival at the colony and delivery, but the other data were more difficult 

to record. 

Nesting biology 

We visited nests every five days to determine the fate of eggs and chicks and to weigh 

and measure chicks. In 1995 we began visiting nests during early incubation (late May - 

early June) and during 1996- 1999 we began visiting nests during late incubation (mid 

June) in order to minimize disturbance. Most nests were visited by rappelling down to 

them from cliff-tops above. Chicks were assigned a rank based on their age: alpha (the 

older of a two-chick brood), beta (the younger in a brood) or singleton (when only one 

egg in a clutch hatched, or when one chick in a brood died at age I 5 d). Because of the 

cryptic nature of nests, we often discovered nests only after chicks had hatched. In these 

situations we assigned alpha status to the larger chick and estimated chick age based on 

flattened wing length, using measurements from a set of known-age captive-reared chicks 

at the Seward SeaLife Center for comparison (Table 14.2; G. Divoky, pers. comm.). We 

only assigned age based on wing length in situations where length was 1 40 mm. 

We measured nesting phenology in every year of the study. We calculated median hatch 

date as our measure of nesting chronology, using the hatch date of the first chick in a nest 

as our metric. We minimized our visits to nests during pre-lay and incubation in order to 

minimize disturbance-caused nest abandonment, so we did not collect data on lay date. 

We measured Inner Bay chick growth rates during 1995- 1999, and Outer Bay growth 

rates fiom 1995 to 1998. During each visit we weighed chicks with spring-loaded scales 

and measured flattened wing length and the length of the tenth primary. We used growth 

rate (slope of linear regression of mass on age) between the ages of 5 and 20 d for 

comparisons of chick growth (Emrns and Verbeek 1991). We also present growth rate 

for chicks aged 8-18 days to allow comparison with studies that use this metric. Growth 

rates of alpha and singleton chicks are generally similar, while beta chicks typically grow 

more slowly (Ainley et al. 1990, Shultz and Sydeman 1997). We therefore present 

growth data for two classes of chicks (alpha I singleton and beta). 

Reproductive success was measured in every year of the study. Because we rarely 

followed nesting attempts from the day of initiation, a simple calculation of reproductive 

success as the number of chicks fledged per nest would overestimate productivity 

because we would fail to account for nests that had failed before we had a chance to 

discover them. We therefore used the Mayfield method to account for nests that failed 

before discovery (Mayfield 1975, Johnson 1979). This method accounts for eggs and 

chicks that are lost before discovery by calculating a daily survival rate (DSR) for each 

nesting phase. DSR is calculated as: 

1 - (number of losses I number of exposure days). 

The nest was treated as the sample unit, and losses were assumed to have occurred at the 

midpoint between the observation when the loss was first noticed and the previous 

observation. For example, if we observed a nest with two eggs on three consecutive 

visits at five day intervals, and then found that after another five days one egg was gone 
and the other was in the process of hatching, then this nest would have one egg loss in 

27.5 days of egg exposure. 

One of the assumptions of the Mayfield method is constant mortality within a given 

phase of breeding, and this was clearly not true for chicks during our study (see Results). 

Since mortality was greater for young chicks than old chicks we calculated separate DSR 

values for chicks age 1- 15 d and 16-30 d (Prichard 1997). We recognize that this 

approach may have shortcomings, since mortality within the two age classes still varies 

with age. However, these age-dependant changes in mortality within a phase were 

minimized by breaking chick rearing into two phases, and we believe that the resulting 

estimates accurately reflect spatial and temporal changes in reproductive success during 

the study. 

The proportion of individuals surviving through incubation and the two phases of chick 

rearing is then calculated as DSR ", where n = the number of days in incubation or a 

phase of chick rearing. We used a mean value for incubation length (3 1 d, Ewins 1993), 

and n = 15 for each of the chick phases. We calculated chick survival only to 30 d 

because chicks may fledge any time post 30 d (Ewins 1993), and it is dificult to 

determine whether chicks older than 30 d have fledged or been depredated. 

We also calculated the number of eggs layed during a given nesting attempt. Situations 

where two females layed in a single nest were treated as two separate nesting attempts. 

We occasionally observed the laying of replacement clutches after original clutches had 

been lost. In these situations we treated both clutches as a single nesting attempt, so 

some nesting attempts consisted of more than two eggs, the maximum clutch size for 

Pigeon Guillemots (Ewins 1993). Nests are often difficult to see into, and contents can 

occasionally be missed by a biologist dangling from a rappel rope, so we considered a 

replacement clutch to have been layed only in situations when original clutches were 

missing on two consecutive visits. 

Many eggs in the study that survived incubation without obvious damage failed to hatch, 

so we calculated the proportion of surviving eggs that actually hatched as: 

1 - (number of eggs failing to hatch / number of eggs surviving incubation). 

Our estimates of reproductive success (chicks fledged / nesting pair) during 1995-1998 

were then calculated as the product of five parameters: the number of eggs layed per 

nesting attempt, the proportion of eggs that survived incubation, the proportion of 

surviving eggs that hatched, the proportion of chicks surviving to age 15 d and the 

proportion of chicks surviving from age 16 d to 30 d. 

In 1999 we reduced our nest-observing effort and visited many nests only twice. We first 

checked nests during 14-15 June to see if they were active (i.e., contained eggs). We then 

visited active nests during late chick rearing (28 July to 1 August) to see if they contained 

chicks. We calculated an index of reproductive success as: C /A, where C = the number 

of chicks found during the second visit, and A = the number of nests active during the 

first visit. During 1996- 1999 we also calculated brood size at fledge, which is the number 

of chicks fledged from nests where at least one chick fledged. 
Adult measurements 

We incidentally obtained morphometric measurements of breeding adults during studies 

of adult foraging behavior. Adults were captured between 8 June and 11 August, and 

were mostly known or suspected breeders. We measured mass and length of flattened 

wing, 10~ primary, headbill, tarsus and culmen. 

Practical considerations 

Kachemak Bay is a good site for hture Pigeon Guillemot research because of the 

existence of historical data and because the Inner and Outer Bay provide two very 

different habitats that can be studied simultaneously. However, there are drawbacks. 

First, nesting density is lower than in some other areas of Alaska. More importantly, 

Pigeon Guillemots in Kachemak usually nest on high cliffs and nests can often be 

accessed only by rappelling 1-50 m down a cliff face. The rock of these cliffs is typically 

rotten and loose, making rappelling more dangerous. Future study crews should include 

people who are well experienced with rappelling and jumaring, and should use static 

rappel line and helmets. 

Study colonies varied widely in the effort that was required to access nests. If current 

patterns of nest dispersion persist, Seldovia Bay, Moosehead Pt. and China Poot Bay 

should form the foundation of any future studies - these areas provide relatively high 

nesting densities and nests are among the easiest to access. Neptune Bay also provides a 

relatively high concentration of nests, but the colony failed repeatedly in the later years of 

the study. Halibut Cove contains a large nesting population, but nests are dispersed and 

time consuming to access. The Yukon Island colony contains few nests. These nests are 

generally easy to reach, but require dangerous scrambles along high, unstable cliff tops - 

we rigged safety lines between trees, but there were not enough trees to protect the whole 

approach. Many guillemots nest on Hesketh Island, but accessing these nests is too 

difficult to make the area useful for research. 

Population monitoring 

Results for each census site are presented in Table 11.3. We detected no trend in the 

results from the aggregated census areas until 1999, when populations in every area were 

down from the previous year (Table 1 1.4). Total counts for the annual shoreline survey 

fluctuated between 467 and 634 Pigeon Guillemots, but there was no trend in these 

results (Table 1 1.5). 

Nesting phenology 

Median hatch date varied from 28 June to 4 July in the Inner Bay, and from 29 June to 1 

July in the Outer Bay (Table 1 1.6). 
Chick diet 

The taxonomic composition of nestling diets is presented in Table 1 1.7. There was a 

strong spatial pattern to diets in Kachemak Bay as guillemots in the Inner Bay 

consistently fed chicks a higher proportion of sand lance than those in the Outer Bay. 

Chick growth 

Chick growth parameters are presented in Tables 1 1.8 and 1 1.9. Growth parameters of 

alpha and singleton chicks were generally similar between study areas, but beta growth 

rates were consistently higher in the Inner Bay than the Outer Bay. 

Reproductive success 

Clutch size was similar between the two study areas, but guillemots were more often able 

to raise two chicks in the Inner Bay than in the Outer Bay (Table 1 1 .lo.). Reproductive 

success was also consistently higher in the Inner Bay (Table 1 1. lo.), and chicks fledged 

at a younger age in the Inner Bay (Table 1 1.1 1). As noted earlier, chick mortality rates 

declined with chick age (Table 1 1.12). 

Adult measurements 

We did not measure enough adults for powerful comparisons between the two areas 

(Table 1 1.13). 

Discussion and Conclusions 

Population status 

Pigeon Guillemot populations in Kachemak Bay were generally stable during the study. 

The decline in abundance of guillemots at all five census areas in 1999 (Table 1 1.4) was 

similar to a decline in the numbers of breeding Common Murres (Uria aalge) in the same 

year in Kachemak Bay (Chapter 9). The decline in Pigeon Guillemot numbers may 

reflect a decrease in the number of birds attempting to breed in 1999 due to factors such 

as poor winter foraging conditions rather than an actual decline in population. 

Chick growth rates 

There was little difference between study areas in alpha / singleton chick growth rates 

(Table 1 1.8), but growth rates were consistently lower for beta chicks in the Outer Bay 

than in the Inner Bay (Table 1 1.9). Other studies have typically pooled chicks in 

analyses of growth rate, regardless of brood status, and are therefore difficult to compare 

with our results. Emms and Verbeek (1991) reported mean growth rates for Pigeon 

Guillemot chicks age 5-20 d on Mitlenatch I., British Columbia as c. 16 g / d for alpha 

and singleton chicks and c. 12 g / d for beta chicks, values well below those fiom either 

of our study areas. 

Reproductive success 

Our estimates for reproductive success ranged between 0.10 and 0.71 chicks / breeding 

pair, and success was always higher in the Inner Bay than in the Outer Bay (Table 1 1.10). 

These estimates are lower than those reported for Prince William Sound (0.25 - 1.25 

chicks / pair; Oakley and Kuletz 1996) and are also lower than values reported for the 
Farallon Islands, California (mean of 0.9 chicks / pair over 13 years; Ainley et al. 1990). 

Methodological differences may account for some of the difference among studies; 

neither of the other studies used the Mayfield method. This probably did not affect the 

Farallon estimate, since nest sites at that area are well known and all breeding attempts 

can be detected. Prince William Sound, however, is more similar to Kachernak Bay in 

that nest sites are cryptic and often not discovered until some time after nesting has 

begun, so reported values for that area may be overestimates because of the failure to 

account for failed nests that were never detected. 

Our breeding success estimates are also sensitive to three assumptions we made about 

parameter values used in the Mayfield method: duration of incubation, duration of chick 

rearing, and mortality rate within the two phases of chick rearing. Although the duration 

of incubation may vary (Ainley et al. 1990), our value of 3 1 d is based on averages from 

a variety of studies (Ewins 1993) and is probably representative. Our assumption that 

chick rearing lasts 30 d is probably also fairly robust, since chick mortality is low after 

this age - we only ever found two dead chicks age > 29 d. Issues concerning constant 

chick mortality are addressed in Methods; we present relevant data in Table 11.12. 

Predation of eggs, chicks, and breeding adults was difficult to quantifl, but clearly an 

important factor in determining breeding success. Known or suspected nest predators in 

the study area include Steller's Jays (Cyanocitta cristata), Northwestern Crows (Corvus 

caurinus), Common Ravens (Cowus corm), mink (Mustela vison) and river otters (Lutra 

canadensis). Vermeer et al. (1993) estimated reproductive success as 0.41 chicks / pair 

at the Queen Charlotte Islands, in an area with high nest predation rates. 

Acknowledgements 

Field work on Pigeon Guillemots in Kachemak Bay was unusually demanding and more 

than occasionally dangerous, and we are deeply indebted to the field crew who made the 

study possible with their extremely hard work: Yumi Arimitsu, Dave Black, Bryan 

Duggan, Jared Figurski, Matt Kopec, Jennifer Litzow, Jeff Moy, April Nielsen, Cynthia 

Restrepo, Pam Seiser, John Shook, Brian Smith, and Sadie Wright. Our thanks to Brad 

Keitt, Greg Snedgen and Tom Van Pelt for logistic support in the field, and to Sera 

Baxter and Mike and Connie Geagel for their hospitality in Kachernak Bay. Alex 

Prichard kindly provided access to 1995 data, and deserves credit for the laborious work 

of discovering enough nests in 1994 to begin a study. We thank Dan Roby for his advice 

and collaboration during the entire course of the project. 

Literature cited 

Abookire, A. A., J. F. Piatt and M. D. Robards. 2000. Nearshore fish distributions in 

an Alaskan estuary in relation to stratification, temperature, and salinity. 

Estuarine, Coastal and Shelf Science 5 1: 45-59. 
Ainley, D. G., R. J. Boekelheide, S. H. Morrell and C. S. Strong. 1990. Pigeon Guillemot. 

In Seabirds of the Farallon Islands, pp. 276-305. Ed. by D. G. Ainley and R. J. 

Boekelheide. Stanford University Press, Stanford, CA. 450 pp. 

Anderson, P. J. and J. F. Piatt. 1999. Trophic reorganization in the Gulf of Alaska 

following ocean climate regime shift. Marine Ecology Progress Series. 189: 1 17- 

123. 

Ernrns, S. K. and N. A. M. Verbeek. 1991. Brood size, food provisioning and chick 

growth in the Pigeon Guillemot Cepphus columba. Condor 93: 943-951. 

Ewins, P. J. 1985. Colony attendance and censusing of black guillemots Cepphus grylle 

in England. Bird Study, 32: 176-1 85. 

Ewins, P. J. 1993. Pigeon guillemot (Cepphus columba). In The Birds of North America, 

number 49. Ed. by A. Poole and F. Gill. The Academy of Natural Sciences, 

Philadelphia, and The American Ornithologists' Union, Washington D.C. 23 pp. 

Golet, G. H., P. E. Seiser, A. D. McGuire, D. D. Roby, J. B. Fischer, K. J. Kuletz, D. B. 

Irons, T. A. Dean, S. C. Jewett and S. H. Newman. in press. Long-term direct and 

indirect effects of the Exxon Valdez oil spill on Pigeon Guillemots in Prince 

William Sound, Alaska. Marine Ecology Progress Series. 

Hayes, D. L. and K. J. Kuletz. 1997. Decline of Pigeon Guillemot populations in Prince 

William Sound, Alaska, and apparent changes in distribution and abundance of 

their prey. Pages 699-702 in Forage Fishes in Marine Ecosystems. Proceedings of 

the International Symposium on the Role of Forage Fishes in Marine Ecosystems. 

Report no. 97-0 1, Alaska Sea Grant College Program, University of Alaska, 

Fairbanks, AK. 

Irons, D. B., S. J. Kendall, W. P. Erickson, L. L. McDonald and B. K. Lance. 2000. Nine 

years after the Exxon Valdez oil spill: effects on marine bird populations in Prince 

William Sound, Alaska. Condor 102: 723-737. 

Johnson, D. H. 1979. Estimating nest success: the Mayfield method and an alternative. 

Auk 96: 651-661. 

Litzow, M. A. 2000. Food limitation in a generalist seabird: reproductive consequences 

of food quality and prey switching in the Pigeon Guillemot (Cepphus columba). 

M.S. Thesis. University of California, Santa Cruz. 36 pp. 

Litzow, M. A. and J. F. Piatt. 2002. Variance in prey abundance influences time budgets 

of breeding seabirds: evidence fiom pigeon guillemots. J. Avian Biol., under rev. 

Litzow, M. A., J. F. Piatt and J. D. Figurski. 1998. Hermit crabs in the diet of Pigeon 

Guillemots in Kachemak Bay, Alaska. Colonial Waterbirds 21 : 242-244. 

Litzow, M. A., J. F. Piatt, A. A. Abookire, A. K. Prichard and M. D. Robards. 2000. 

Monitoring temporal and spatial variability in sandeel (Ammodytes hexapterus) 

abundance with Pigeon Guillemot (Cepphus columba) diets. ICES Journal of 

Marine Science 57: 976-986. 

Litzow, M. A., J. F. Piatt, A. K. Prichard and D. D. Roby. 2002. Pigeon guillemot 

breeding biology in relation to oceanography and prey abundance: A natural 

experiment. Oecologia. Accepted. 

Mayfield, H. F. 1975. Suggestions for calculating nest success. Wilson Bulletin 87: 456- 

466. 
Merrick, R L., M. K. Chumbley and G. V. Byrd. 1997. Diet diversity of Steller sea lions 

(Eumetopias jubatus) and their population decline in Alaska: a potential 

relationship. Canadian Journal of Fisheries and Aquatic Sciences 54: 1342- 1348. 

Murphy, S. M., R. H. Day, J. A. Wiens and K. R. Parker. 1997. Effects of the Exxon 

Valdez oil spill on birds: comparisons of pre- and post-spill surveys in Prince 

William Sound, Alaska. Condor 99: 299-3 13. 

Oakley, K. L., Kuletz, K. J. 1996. Population, reproduction, and foraging of pigeon 

guillemots at Naked Island, Alaska, before and after the Exxon Valdez Oil Spill. 

American Fisheries Society Symposium, 18: 759-769. 

Osenberg, G. W., R. J. Schmitt, S. J. Holbrook, K. E. Abu-Saba and A. R. Flegal. 1994. 

Detection of environmental impacts: natural variability, effect size, and power 

analysis. Ecological Applications 4: 16-30. 

Piatt, J. F., C. F. Lensink, W. Butler, M. Kendziorek and D. R. Nysewander. 1990. 

Immediate impact of the Exxon Valdez oil spill on marine birds. Auk 107: 387- 

397. 

Piatt, J. F. and P. Anderson. 1996. Response of common murres to the Exxon Valdez Oil 

Spill and. long-term changes in the Gulf of Alaska marine ecosystem. American 

Fisheries Society Symposium 18: 720-737. 

Piatt, J. F. and R. G. Ford. 1996. How many seabirds were killed by the Exxon Valdez oil 

spill? American Fisheries Society Symposium. 18: 712-7 19. 

Prichard, A. K. 1997. Evaluation of Pigeon Guillemots as bioindicators of nearshore 

ecosystem health. M.S. thesis, University of Alaska, Fairbanks. 93 pp. 

Sanger, G. A. and M. B. Cody. 1994. Survey of Pigeon Guillemot colonies in Prince 

William Sound, Alaska. Exxon Valdez Oil Spill Restoration Project Final Report 

(Restoration Project 93034). U.S. Fish and Wildlife Service, Anchorage, Alaska. 

53 PP. 

Shultz, M. T. and W. J. Sydeman. 1997. Pre-fledging weight recession in Pigeon 

Guillemots on Southeast Farallon Island, California. Colonial Waterbirds 20: 436- 

448. 

Vermeer, K., K. H. Morgan, and G. E. J. Smith. 1993. Nesting biology and predation of 

Pigeon Guillemots in the Queen Charlotte Islands, British Columbia. Colonial 

Waterbirds 16: 1 19-1 29. 

Wiens, J. A. and K. R. Parker. 1995. Analyzing the effects of accidental environmental 

impacts: approaches and assumptions. Ecological Applications 5: 1069- 1083. 
Chapter 12. Homed Puffin Biology on Duck Island 

Ann Harding 

Introduction 

The Horned Puffin is one of three North Pacific puffin species, with a summer breeding 

distribution that ranges fiom 50" to 70" North Latitude (Amaral 1977). In contrast to the 

burrow-nesting habits of the Atlantic Puffin Fratercula arctica, Tufted Puffin Fratercula 

cirrhata and the Rhinoceros Auklet Cerorhinca monocerata, the Horned Puffin almost 

always nests among boulders or in rock crevices, making access to chicks difficult and 

complicating study of their breeding biology. Horned Puffins lay a single-egg clutch. The 

average incubation period is 41 days, and both parents share incubation duties (Amaral 

1977). After hatching, the chick is brooded constantly by a single parent for the first 5-7 

days. The chick develops slowly, with a typical nestling period of 38-42 days (Amaral 

1977). Both parents feed the chick, making several food deliveries per day. Sandlance 

(Ammodytes hexapertus) is the most important prey component of Horned Puffin chick 

diet, averaging 65% of the diet throughout the North Pacific (Piatt and Kitaysky 2001). 

From long-term studies of Atlantic Puffins (e.g., Ashcroft 1979, Harris et al. 1997) we 

how that puffins can respond to limiting food supplies with reduced growth rates, 

extended fledging periods, shifts in chick diet, and even complete breeding failure (e.g., 

Barrett and Rikardsen 1992). 

Horned Puffins were not a primary study species for our project in lower Cook Inlet, and 

bred on only lof 3 main study colonies. However, Duck Island (small island adjacent to 

Chisik Island, names used interchangeably throughout report) contained a relatively large 

and accessible population, and so we took the opportunity to include Horned Puffins in 

our larger study of seabird responses to changing food supplies. Thus, we studied the 

breeding biology, chick growth, chick diet and adult attendance of Horned Puffins on 

Duck Island fiom 1995 to 1999. The main objectives of our study were to: 1) Examine 

inter-year variability in Horned Puffin breeding parameters and measure the response of 

Horned Pub to annual fluctuations in prey availability, and, 2) Examine the diurnal 

and seasonal attendance patterns of adult Horned Puffins in order to develop a 

standardized population monitoring protocol. 

These objectives have been met in an M.Sc. dissertation (Harding 2000) and manuscripts 

that have submitted for publication (Harding et al. 2002,2003a,b). This chapter 

summarizes information we gathered on the breeding biology, chick growth, chick diet 

and adult attendance of the Horned Puffin over five years of study (1995-1999) in lower 

Cook Inlet, and briefly examines some of the results in the context of other studies. 

Results presented here also provide an archive of data for future investigations. 
Productivity 

Reproductive success was measured during 1995- 1999. Homed Pufins are sensitive to 

disturbance during the incubation phase of their breeding cycle, and may abandon 

breeding in response to disturbance of their nest sites. Productivity measures therefore 

have to be based more on observations made by following nest-sites hm late incubation 

to fledging. Laying success cannot be practically assessed, and measures of hatching 

success and breeding success may be overestimates and biased towards those eggs that 

have survived until the end of incubation. It is not even practical to measure egg survival 

rates in order to use the Mayfield methods for adjusting hatching success (as in Pigeon 

Guillemots, Chapter 11). 

Towards the end of incubation in each year, the island was searched for active nest-sites 

with visible nest-chambers. The timing of this check was based on knowledge of Homed 

Puffin breeding chronology at Duck Island in previous years. The first check was 

conducted about one week before the expected first hatch date. Most of the east side of 

the island was excluded fiom study due to dangerous rock conditions. Active sites were 

identified with a painted number on an adjacent rock. Site numbers remained consistent 

between years. Nest-sites were visited every 3-5 days during the hatching period and 

every 4-7 days until fledge. During each visit the nest chambers were checked using a 

headlamp, and the presence of adult, egg or chick was recorded. Visits were brief so as to 

minimize disturbance. When sight of an egg or chick was blocked by an adult, the adult's 

brooding posture and the presence of egg shell fragments were used as evidence of hatch. 

In the few nest-chambers where chicks could move out of sight, chick fate and nest-site 

chronology were determined using evidence of chick presence; chick vocalization, guano 

and the presence of dropped fish were recorded. 

Hatching, fledging and breeding success were calculated for each year, using nest-site as 

the sample unit. The timing of the first nest-check during incubation varied between years 

(23 June to 16 July). To control for a possible inter-year bias in recorded egg-loss and 

therefore hatching success, we excluded nest-sites where an egg was followed and lost 

before July 15. It was not possible to follow all chicks to fledging due to the early 

departure date of field crews at the end of each seasons. To enable calculation of fledging 

success and control for the different field-crew departure dates between years, it was 

necessary to have a 'cut-off age for chicks considered to have survived until fledging. 

We investigated chick mortality with age. Considering chicks fiom all 5 years (n=161), 

twenty chicks died in total; with 80% of deaths occurring at age 10 days or less, and with 

zero mortality after 20 days old. Once chicks had survived to 20 days, we observed no 

mortality in the 59 chicks we were able to track to 35+ days old, 30 of whom did not 

fledge until =40 days old. For the purpose of fledging success, we therefore assume that 

chicks =20 days survive until 'fledging'. 

Mean fledging age was calculated by including all chicks hm productivity data and 

known-age measured chicks which left their nest-site at =20 days old. Fledging age were 
determined to f 0-3 days. Due to early departure of field crews, we were only able to 

calculate fledging age in 1996, 1998 and 1999. No meal collections took place at any 

productivity site. Median chick hatch date was used as a measure of annual breeding 

chronology. For the years 1996-1999, median hatch date was calculated by including 

only chicks with a hatch date range of less than 5 days. In 1995, where most hatch date 

ranges were approximately 8 days, median hatch date was calculated using all chicks 

with a hatch date range of less than 9 days. 

Chick meal collection 

The diet of Homed Puffin chicks on Duck Island was sampled between 1995 and 1999. 

Five methods for chick meal collectiodprey identification were used: "Screening"- 

Entrances to nest-sites were blocked using re-usable metal grid screens (Hatch and 

Sanger, 1992). Adults prevented from entering the nest-site may drop the food at the 

screened entrance. Screens were wedged between the boulders to make a strong bamer 

and nest-sites flagged to help relocation. After about 2 h, nest-sites were revisited, 

screens removed and food samples collected. "Gill net"- Gill nets (2-3 cm mesh) or 

mist nets were draped over boulder piles, blocking the entrances to several puffin nestsites. Nets were set and observers hid out of sight. Adults delivering meal loads became 

tangled in the net and dropped their bill loads. The adults were immediately untangled, 

measured and released, and the dropped bill load collected. "Pick ups'- Chick meals are 

often dropped by flying or landing adults. Freshly dropped fish were collected throughout 

each season. Many complete bill loads were collected whilst working in large caves with 

multiple homed puffin nest-sites. Adults amving with fish were often startled by a 

worker's presence and dropped their whole bill-load. "Visual observation"- Bill loads 

held by adults standing on the boulders and cliffs were recorded. The prey species were 

identified using 10 x 42 binoculars and the number of fish in the bill load counted. 

"Experimental halter"- In 1998, a supplemental feeding experiment was conducted to 

examine the ability of adults to adjust provisioning effort. In order to obtain an accurate 

measurement of food delivery, a halter made from black pipe-cleaner wire was designed 

to prevent prey consumption and allow collection of individual prey items. The pipe 

cleaner was twisted around the base of the bill, to prevent bill opening and fish ingestion, 

and fitted loosely around the neck and head to anchor the noose in place. Chick 

movement, breathing and vocalization were not impaired. Halters were fitted at dusk and 

removed after 48 hours. Sites were visited 4-5 times daily at regular intervals during both 

days, and all fish were collected from the nest chamber. The nooses were removed once 

per 24 hours in order to feed chicks with the equivalent amount of food normally 

provided by their parents. 

All prey collected were identified, weighed (using an electronic balance, + 0.01g) and 

measured (fork length in mm). Energy values of prey were calculated using published 

wet mass energy density conversions (Van Pelt et al. 1997, Paul et al. 1998). All meal 

collections were identified as either a complete or incomplete bill load. Loads classified 

as bill-loads were either dropped loads, gill-net loads where no fish were lost, or a visual 

identification of load contents. 
Feeding rates 

Daily meal delivery rates to Homed Puffin chicks were recorded for 2-3 days in both 

1996 and 1997. It was impossible to simultaneously observe many nest-sites because 

Duck Island has a low density of nest sites and the majority of crevice or cave nest-sites 

have multiple or shared entrances. It was possible to observe 4-5 burrow or simple 

crevice nests in two locations on Duck Island. One area was observed from the Cliff 

Blind on the West coast of Duck Island and the other area was located on the slope at the 

West end of North Cove. The North Cove area was observed from the top of the cliff 

path. In both areas, 4-5 active nest-sites were identified and numbered on a photograph. 

Sites were observed from 0630-2200 and all adult amvals, departures and food deliveries 

were recorded. Owing to the speed of delivery it was impossible to identify bill load size 

or meal composition. Since adults were not banded or marked, it was not possible to 

measure individual trip durations or nest-site attendance. The total number of daily meal 

deliveries were calculated per chick. 

Chick Measurements 

Chick growth was measured in all years (1995-1999). Nest-sites with accessible chicks 

were located and numbered with paint. Site numbers remained consistent between years. 

The young were first handled when they were >5 days of age. For the few nest sites with 

accessible chicks that were found later in the season, where hatch date was unknown, 

chicks were aged using the following linear regression (3 = 0.86) of age on wing-length 

(Fig. 12.1) for chicks of known age: chick age (days) = 0.26 wing length (rnm) - 0.54. 

Chicks were visited every 4-7 days during the chick-rearing period, and every 3-5 days 

during the fledging period. During each visit, the following body dimensions were 

measured with Vernier calipers (following Wernham and Byrant, 1998): tarsal length, 

total head plus bill length (measured as the greatest distance from the central back of the 

head to the tip of the upper mandible, with the upper surface of the calipers resting on the 

top of the head), culmen (from the tip of the upper mandible to the anterior edge of the 

growing cere), and straightened wing length using a stopped ruler, and body mass using a 

Pesola balance. Individual chicks were measured by the same person. Repeat 

measurements were always within 0.5 mm for head-bill, 0.2 mm for culmen and tarsus, 

1.0 mm for wing length and 1.0 g for mass. Due to the crevice nesting habits of homed 

pufbs, the number of chicks measured and the number of individual chick visits were 

limited by the accessibility of their nest chamber. Due to the early field crew departure 

date in most years, we were unable to collect many data on fledging measurements or 

peak mass. Blood samples were taken from 14 chicks in 1998 and 21 chicks in 1999. 

Adult Measurements 

Breeding adult Homed Puffins were measured in 1998 and 1999. Adults were either 

captured in their nest chamber during the chick-rearing period or trapped using a gillnet 

placed over the nest entrance during food delivery. Standard body measurements were 

taken (as for chicks). Three extra bill measurements were also made; bill width, at the 

proximal base of the nostril, bill depth and cutting edge (Fig. 12.2). To prevent recapture 

of the supplemental feeding experiment birds during the 1998 breeding season, captured 

adults were banded with a metal AVISE band on the left leg, and a single, numbered 
plastic band on the right leg. Genetic blood samples were taken from 1 1 adults in 1998 

and 18 adults in 1999. 

Fledgling Measurements 

Towards the end of the 1998 and 1999 breeding season, the shoreline was searched at 

night using headlarnps. Fledging chicks were intercepted during their journey to the sea. 

Standard body measurements were taken (as for chicks) before release. Blood samples 

were taken hm six fledglings in 1998. 

Plot census 

In 1996, six population plots were established within North Cove and monitored between 

1996 and 1999. A description of each plot is below. To maintain consistent plot 

boundaries, plots were highlighted on photos taken from the observation site. Photos are 

archived at USGS, Alaska Science Center. The observation site over-looks North Cove 

and is permanently marked with an orange stake. Plot descriptions are as follows: 

Plot 1 : Boulders on the vegetated slope between the two cottonwood trees. Plot boundary 

outlined on photos. Estimated area, 1 lx7m. = 77m2; Plot 2: Area of scree at the base of 

the cliff. Plot boundary marked with blue paint and outlined on photos. Area, 1 lx7m. = 

77m2; Plot 3: Large boulders on the beach. Plot boundary marked with blue paint and 

outlined on photos. Area, 12x6.5m. =78m2; Plot 4: Boulders on the cliff. Plot boundary 

outlined on photos. Estimated area, 25x3m. = 75m2; Plot 5: Area of cliff on the far West 

side of North cove. Plot boundary outlined on photos. Estimated area, 15x5m. = 75m2; 

Plot 6: Area of scree at the base of the cliff. Plot boundary marked with blue paint and 

outlined on photos. Area, 25xl3m. = 325m2. 

The attendance of Homed Puffins at the colony peaked in the evening between 1930 and 

2 145. Between 2030 and 2 145 daily, the number of birds on each plot were recorded at 

15 min intervals. Birds were counted using 10x 42 binoculars. Due to shortening daylight 

hours, counts towards the end of the season were advanced to begin at 201 5. Tufted 

Puffins were counted and recorded separately. 

Colony Census 

Island counts were conducted in 1 995- 1999. During an evening peak in colony 

attendance, the shoreline of Duck Island was circumnavigated on foot, by either one or 

two observers, and all Homed and Tufted Puffins were counted. Birds counted included 

all those visible on land and all individuals rafting (within an estimated 200 m from 

shore). In addition, the number of birds wheeling in flight were estimated. Observer, 

weather, tide and sea conditions, and the count start and end times were recorded. 

Seasonal Colony Attendance 

Seasonal colony attendance of Homed Puffins was recorded in 1997, 1998 and 1999. 

Daily counts were made from 27 June to 3 1 August in 1997, from 26 May to 4 September 

in 1998 and between 23 May and 14 September in 1999. Counts were conducted from the 

marked population plot observation point overlooking North Cove. Birds were counted 

using 10x 42 binoculars. 'Rafting' and 'loafing' birds were counted separately at 15 

minute intervals during the daily evening peak (between 2030 and 2145). Up to 5 counts 

were made during this period each day, and these were used to calculate mean daily 
values for the number of birds counted on water, land and total (land and water 

combined). 'Rafting birds' included all birds on the water inside the cove boundaries and 

within 200 m hm shore; a set buoy was used for reference. 'Loafing birds' included 

birds on all north-facing land visible hm the population plot observation point 

(including the 6 population plots). Due to shortening daylight hours, counts towards the 

end of the season were advanced to begin at 2015. 

Diurnal Colony Attendance 

Diurnal colony attendance was monitored for 2 days in 1996,3 days in 1997 and 1 day 

during the 1998 breeding season. Counts were conducted fiom the marked population 

plot observation site overlooking North Cove. Birds were counted using lox 42 

binoculars. Homed Puffins present in North Cove were counted fiom 0500-2300 at 30 

minute intervals. Two separate counts were conducted at each half hour. 'Rafting birds' 

include all birds on the water inside the cove boundaries and within 200 m. fiom shore, a 

set buoy was used for reference. 'Loafing birds' include all birds on land within the North 

Cove boundaries (including the 6 population plots). 

Results 

Productivity 

Breeding success was high and similar among years (Table 12. I), and there was no 

significant difference in hatching success, fledging success or overall breeding success 

between years. Although no consistent effort was made to resight banded birds, there is 

evidence of nest-site fidelity, with 5 of the 1 1 birds banded in 1998 opportunistically 

resighted in the same burrows in1999. Median chick hatch date ranged fiom 19 July in 

1996, to 29 July in 1998 (Table 12.1). 

Chick Diet 

A total of 2796 prey items were collected during 1995- 1999 (Table 12.2). Sand lance was 

the dominant prey species (Fig. 12.3), constituting over 94% of the chick's diet in each 

year. Most of the other prey consisted of capelin (Mallotus villosus) or salmon species 

(Onchorhynchus sp.). Invertebrates comprised an extremely small part of chick diet, with 

only 2 squid and 8 euphausiid among the total of 2796 prey items collected. There was no 

significant difference in the proportion of sand lance in the chick's diet between years 

(~2=6.36, df4, p >0.05). Sandlance differed in size between years, with relatively small 

individuals delivered to chicks in 1996 and 1997, and larger individuals in 1999 (Table 

12.3). Sandlance length ranged hm a mean of 85.2 mrn in 1996 to 100.2 mm in 1999 

(total range = 31-223mm). Mean mass ranged fiom 2.lg in 1996 to 3.3 g in 1999. 

There was no significant difference in mean mass of fish per bill load (ANOVA: F=0.8, 

de3,57, @.97), or the mean number of prey items per load (ANOVA: F=1.54, 

d63,124, p=0.2) between years 1996 to 1999 (Table 12.4). Mean bill load mass over all 

5 years was 16.4 h 0.8 g (n=63), mean number of prey items per load was 6.2 h 0.3 

(n=132). Daily meal delivery rates were recorded for a total of 5 days in 1996 and 1997; 

means ranging hm 2.6 to 6.8 meals per day are presented in Table 12.5. 
Chick growth 

To compare growth among years, I calculated growth rate (using linear regression) for 

different body components during the linear phase of growth (10-30 days for body mass 

and wing length; 0-15 days for culmen and tarsus length). These data were used to 

calculate a single growth rate, for each body component, for each chick. There was a 

significant difference among years in mass growth rates of chicks (Table 12.6), with 

much slower growth in 1998 than in other years. 

We were only able to measure puffin chick fledging ages in 1996,1998 and 1999. There 

was a significant difference in chick fledging age between the 3 years (ANOVA: 

F=15.66, d62,69, p=<0.001). Means are shown in Table 12.7. Although growth rate was 

lowest in 1998, chicks fledged at the youngest age (34.7 days). 

Adults and fledgling measurements 

A total of 38 breeding adult puffins were caught in 1998 and 1999. Morphometrics are 

presented in Appendix 12.1. Mean adult wing length was 198 mm (SD= 7.32, n=38), 

mean adult body mass was 53 lg (S.D. = 44.27, n=38). Very few fledglings were caught, 

and their measurements are provided in Table 12.8. 

Seasonal and diurnal attendance 

The seasonal colony attendance of Homed Puffins is presented in Fig. 12.4. We are in 

the process of examining seasonal patterns and the annual and daily variability in 

attendance (Harding et al. 2002b). However, some general patterns are apparent: 1) there 

is high variation in daily colony attendance, 2) late incubation is characterized by the 

highest numbers of puffins, 3) the numbers of attending birds drop during the first two or 

three weeks of chick-rearing. Diurnal attendance was monitored for 6 days in total during 

1996, 1997 and 1998. Diurnal attendance for 1997 is shown in Fig. 12.5. A morning and 

a larger evening peak were observed. Puffin numbers were low between 1300 and 1500 

hours. Attendance is highest during the evening peak, between 1930 and 2 130. 

Population plots and colony census 

We are in the process of examining the population plot data for 1996- 1999 (Harding et al. 

2002b). Daily variability in counts is reflected in the seasonal attendance data (Fig. 12.4), 

with the 'land' counts including the 6 population plots. Colony counts of Homed Puffins 

are presented in Table 12.9; Tufted Puffin counts in Table 12.10. We are also examining 

the population counts with respect to phenology and the data from seasonal colony 

attendance. 
Discussion and Conclusions 

Since we have no measure of laying success and only followed eggs fhm late incubation, 

it is difficult to compare the hatching and breeding success on Duck Island with other 

studies on Homed Puffins. The mean fledging success for the 5 years (91.4%) is 

relatively high compared to other studies in which fledging success ranged fhm 25- 

loo%, with a mean of 75% (n=39) (Piatt and Kitaysky 2001). 

Complete breeding failure in the Atlantic Puffin has been frequently reported, and has 

usually been attributed to extremely poor food availability, and often attributed to 

overfishing (eg., Anker-Nilssen 1987, Banett et a1 1987, Barrett and Rikardsen 1992, 

Martin 1989, Lid 198 1). Breeding failure has also been recorded in the Tufted Puffin and 

the Rhinoceros Auklet (Cerorhinca monocerata) (Vermeer 1979, 1980), and in the 

Homed Puffin (Byrd et al. 1993). Although it seems that puffins have some flexibility 

and can extend their chick feeding period during seasons of short food supply, life history 

theory predicts that under seasons of extreme short food supply parents will abandon 

their breeding attempt, reducing the risk of mortality associated with high parental effort. 

Although Common Murres experienced an almost complete breeding failure in 1998, 

suggesting that local feeding conditions were extremely poor, the lack of detectable 

difference in reproductive success for puffins on Duck Island between years suggests that 

Homed Puffins can successfully rear a chick to fledging over a wide range of food 

availabilities. Breeding failure has been rarely recorded in the Homed Puffin, and 

evidence from other studies suggests that the variability in the reproductive success of 

Homed Puffins between years and at different colonies is incredibly low. Homed puffin 

fledging success over 39 colonies years averaged 73% (range = 25- 100) (Piatt and 

Kitaysky 2000). Our data is however limited by lack of knowledge of the proportion of 

birds that attempt to breed between years, and we were unable to measure incubation 

success, a suggested key factor for reproductive success in puffins (Hatch and Hatch 

1 990). 

Chick diet over the 5 years of this study was dominated by sand lance, constituting over 

94% of the diet in each year. Capelin and juvenile salmonids comprised most of the other 

prey, each constituting approximately 2% of the chick diet. Pacific lamprey and sandfish 

are unusual prey species for Homed puffins, but were observed in small numbers in the 

chick diet on Duck Island. The diet of Homed Pu& chicks on Duck Island is high in 

sandlance, even for a species known to specialize, with 60% of chick diet throughout the 

North Pacific range comprised of sandlance (Piatt and Kitaysky 2000). Homed Puffin 

chicks are fed almost entirely fish, with sandlance, capelin and gadids the most important 

prey species across their North Pacific range (Piatt and Kitaysky 2001). Homed puffin 

chicks are fed relatively few other prey species in comparison to the Tufted Puffin (Hatch 

and Sanger 1992). For example, the chick diet of Tufted Puffins on Suklik in 1985 

consisted of 32 fish species and 7 kinds of invertebrate, whereas Homed Puffin chicks 

were fed only 13 fish species and 2 kinds of invertebrates. Sandlance constituted 83% of 

the Homed Puffin chick diet, and only 48% of the Tufted Puffin chick diet (Hatch and 

Sanger 1992). 
The size of sandlance delivered to chicks differed between years, from a mean of 85mm 

in 1996 to 1 Ohm in 1999 (total range=3 1-223). Other studies have recorded ranges in 

sandlance size from 56- 164mm (Wehle 1983) and 25- 164mm, mean=7hm (n=3746) 

(Hatch and Sanger 1992). Chicks in this study received bill loads weighing on average 

16g (range=2.5-35.5g), and comprising an average of 6 prey items (range; 1-22). Other 

studies have recorded a similar number of prey items per bill load from 1- 1 1 (n=15) 

(Wehle 1983) and a mean of 7 (n=619) (Hatch and Sanger 1992). Bill load mass in this 

study is relatively high compared to other studies, which report an average of 9.3 g per 

load (n=12 colony years) (Piatt and Kitaysky 2001). This difference may be explained by 

the different methods of meal load collection. Whereas most studies have collected meal 

loads by blocking nest-sites using re-usable metal grid screens (Hatch and Sanger 1992), 

this study only classified and weighed bill-loads either where a whole load was observed 

dropped or when loads were collected using a gill-net and it was known that no fish were 

lost. The bill load size and mass recorded in this study present a more accurate measure 

than most other studies. Loads collected using the screening methods are probably 

underestimated since adults may eat food if prevented from delivering to the chick, and 

meals may be taken by gulls (pers. obs). 

Due to their habit of nesting in crevices, at often scattered locations, little is known about 

chick feeding frequency in Horned Puffins. Data from this study are limited, ranging 

from a mean of 2.6-6.8 meals a day over 5 days of observation. These are similar 

frequencies to those reported on the Barren Islands (2-6 meals/day) (Manuwal and 

Boersma 1977). 

The large range in chick growth rates observed over the 5 years of this study (mean of 

3.7-12.8g/day) is similar to the range reported in other studies, from a record low of 

3.4g/day in the Semidi Islands to 12.6g/day at the Shamagin Islands (Petersen 1983). In 

1979, puffin chicks on Duck Island grew at 10.7 f 0.7 g/day (n=12) (Jones and Petersen 

1979), approximately the same rate as we observed in 1997. Chick growth rate depends 

on food intake. In an experimental study, Horned puffin chicks fed ad libitum (108glday) 

grew at 1 1.2 * 0.54 SE &day, whereas chicks fed 53g/day grew at 6.45 * 0.46 SE g/day 

(Kitaysky 1999), results suggesting that chicks in 1997 (growth= 10.5glday) may have 

been receiving close to ad libitum food. 

Food limitation is known to reduce the growth rate in puffin chicks (Harris 1984), with 

well documented evidence from both experimental studies (Harris 1978, Hudsen 1979, 

Kitaysky 1996, Kitaysky 1999,IZ)yan and Nilssen 1996) and in the field (eg; Barrett et a1 

1987, Barrett and Rikardsen 1992, Harris 1985, Tzchanz 1979). We assume that the 

amount of food received by a chick to be related to the local availability of prey. Growth 

rates in 1998 were exceptionally low (3.7 g/day), in comparison to chick growth in the 

other 4 years (9.4-12.8g/day), evidence suggesting that food availability was severely 

limiting the growth of chicks in 1998. 
Acknowledgments 

We thank Tom Van Pelt, Leigh Ochikubo, Ram Papish, Mike Gray, Dave Black, Greg 

Hoffman, Alice Chapman, Brian Smith and Jo Wilding for their energy and commitment 

in helping to collect data in the field. The staff, especially Vernon Byrd and Trina 

Fellows, at the Alaska Maritime National Wildlife Rehge (USFWS) and also the staff at 

Lake Clark National Park (NPS) were instrumental in providing access, facilities, 

communication and general support. We are gratefbl to Greg Snedgen for all his practical 

expertise and hard work before, during, and after the field seasons; his contributions 

improved the safety and efficiency of our work. Tom Van Pelt helped throughout with 

camp support and logistic coordination; Mike Shultz and other members of the CISeaFFS 

team also supported our work. John Piatt and Sasha Kitaysky gave vital encouragement 

and guidance. Thanks to Tom Van Pelt for his helphl review of this chapter. The crew of 

the RIV Pandalus helped with the supply of mail, food, he1 and island morale. We thank 

the crew of the MN Georgia Straits for their cheerfulness and logistic support. Bob and 

Dorea Woods at the Snug Harbour Cannery, Columbia Ward Fisheries, helped greatly 

with emergency communications, a watchful eye on our boating, the supply of fbel, mail 

and their friendship. Eric Randal gave essential help in 1995 with transport to Duck 

Island, practical advice on boating and the local waters, friendship and a hot stove. We 

thank Bob and Dorea Woods, Eric and Jill Randal, Machelle Haynes, The Bunker family, 

Tom Gordon, The Kistler family and Sandy Sinclair for helping make both Duck and 

Chisik Island such a wonderful place to live and work in during all the years we were 

there. We also thank the many other past and present residents of Tuxedni Channel who 

made us feel welcome. 

References 

Amaral, M.J. 1977. A comparative breeding biology of the Tufted and Horned puffin in 

the Barren Islands, Alaska. M.S. Thesis, University of Washington, Seattle. 

Anker-Nilssen, T. 1987. The breeding performance of puffins Fratercula arctica on &st, 

northern Norway in 1979- 1985. Fauna Norvegica Sene C., Cinclus 10: 2 1-3 8. 

Ashcroft, R.E. 1979. Survival rates and breeding biology of puffins on Skomer Island, 

Wales. Ornis Scandinavica, 10; 100- 10 1. 

Barrett, R.T. and F. Rikardsen. 1992. Chick growth, fledging periods and adult mass loss 

of Atlantic puffins Fratercula arctica during years of prolonged food stress. 

Colonial Waterbirds 15 (1); 24-32. 

Barrett, R.T., Anker-Nilssen, T., Rikardsen, R., Valde, K., bv, N. and T. Vader.1987. 

The food, growth and fledging success of Norwegian puffin chicks Fratercula 

arctica in 1980-1983. Ornis Scandiavica 18: 73-83. 

Byrd, G.V., Murphy, E.C., Kaiser, G., Kondratyev, A.Y. and Shibaev, Y.V. (1993). 

Status and ecology of offshore fish-feeding alcids (murres and puffins) in the 

North Pacific. In the Status, ecology and conservation of marine birds of the 

North Pacific, (ed. K. Vermeer, K.T. Briggs, K.H. Morgan, and D. SiegelCausey), pp. 176-86. Canadian Wildlife Service, Ottawa. 

Erikstad, K.E., Asheim, M., Fauchals, P., Dahlhaug, L. and T. Tveraa. 1997. Adjustment 

of parental effort in the puffin; the roles of adult body condition and chick size. 

Behavioual Ecology and Sociobiology, 40; 95-100. 
Harding, A. M. 2001. The breeding ecology of Horned Puffins Fratercula corniculata. 

M.Sc. Thesis, University of Durham, England. 74 pp. 

Harding, A.A., T. van Pelt, J.F. Piatt, and A.S. Kitaysky. 2002. Reduction of 

provisioning effort in response to experimental manipulation of chick nutritional 

status in the horned puffin Fratercula corniculata. Condor 104: 842-847. 

Harding, A.M.A, J.F. Piatt and K.C. Hamer. 2003a. Breeding ecology of Horned Puffins 

(Fratercula corniculata) in Alaska: Annual variation and effects of El Niiio. 

Canadian Journal of Zoology 8 1 : 1 004- 1 0 13. 

Harding, A.H., J.F. Piatt, G.V. Byrd, S.A. Hatch, N. Konyukhov, E.U. Golubova and J.C. 

Williams. 2003b. Measuring variability in colony attendance of crevice-nesting 

Horned Puffin throughout the North Pacific: Implications for population 

monitoring. Submitted to J. Wildlife Management. 

Harris M.P. 1978. Supplementary feeding of young puffins Fratercula arctica. Journal of 

Animal Ecology 47, 1 5-23. 

Harris, M.P. 1985. Morphological and Breeding of Puffins at Isla of May and St Kilda, 

Scotland. Biological Conservation 32: 8 1-97. 

Harris, M.P., Freeman, S.N., Wanless, S., Morgan, B.J.T. and C.V. Wernham. 1997. 

Factors influencing the survival of Puffin Fratercula arctica at a North Sea 

colony over a 20-year period. Journal of Avian Biology, 28; 287-295. 

Hatch, S.A. and M.A. Hatch 1990. Components of breeding productivity in a marine bird 

community: key factors and concordance. Canadian Journal of Zoology 68 (8): 

1680- 1690. 

Hatch, S.A. and G.A. Sanger. 1992. Puffins as samplers of juvenile pollock and other 

forage fish in the Gulf of Alaska. Marine Ecology Progress Series, 80; 1-14. 

Hudsen, P.J. 1979. The parent-chick feeding relationship of the puffin, Fratercula arctica. 

Journal of Animal Ecology 48: 898-898. 

Jones, R.D. and Petersen, M.R. 1979. The pelagic birds of Tuxedni wilderness, Alaska. 

Annual report, NOAA-OCSEAP 01 -5-022-2538, Anchorage, Alaska, 41 pp. 

Kitaysky, A.S. 1996. Behavioural, physiological and reproductive responses of alcids 

(Alcidae) to variation in food availability. Ph.D. Thesis, University of California, 

Irvine, CA 161 pp. 

Kitaysky, A.S. 1999. Metabolic and developmental responses of alcid chicks to 

experimental variation in food intake. Physiological and Biochemical Zoology 

72(4); 462-473. 

Lack D. 1968. Ecological adaptations for breeding birds. Methuen, London, UK. 

Lid. G. 198 1. Reproduction of the puffin on Rarst in the Lofoten Islands in 1964- 1980. 

Fauna norvegica Ser. C, Cinclus 4,30-39. 

Manuwal, D.A, and Boersma, P.D. 1977. Dynamics of marine bird populations on the 

Barren Islands, Alaska. In: Env. Assess. Alaskan Cont. Shelf, Ann.Rep. No.4.U.S. 

Dept. Commerce and U.S. Dept. Interior, Outer Cont. Shelf Env. Assess. Prog. 

P294-420 

Martin, A.R. 1989. The Diet of Atlantic puffin and northern Gannet at a Shetland colony 

during a period of changing prey availability. Bird Study 36: 170- 180. 

Qlyan, H.S and Anker-Nilssen, T. 1996. Allocation of growth in food stressed Atlantic 

puffin chicks. The Auk 1 13(4): 830-841. 
Paul, A.J., Paul J.M. and Brown, E.D. 1998. Fall and spring somatic energy content for 

Alaskan Pacific herring (Cupea pallasi Valenciennes 1847) relative to age, size 

and sex. Journal of Experimental Marine Biology and Ecology, 223(1); 133-142. 

Piatt, J.F. and Kitaysky, A. S. 200 1. Horned Puffin (Fratercula corniculata). In The Birds 

of North America (A.Poole and F. Gill, Eds.). Philidelphia: The Academy of 

Natural Sciences; Washington D.C.; The American Ornithologists7 Union, in 

Press. 

Petersen, M.R. 1983. Horned puffin (Fratercula Corniculata). Pp. 40 1 -426 in: The 

breeding biology and feeding ecology of marine birds in the Gulf of Alaska. P.A. 

Baird and P.J. Gould (eds.). U.S. Dep. Commer., NOAA, OCSEAP Final Rep. 

45(1986):3 1-771. 

Sealy, S.G. 1973. Adaptive significance of post hatching development patters and growth 

rates in the alcidae. Ornis Scandiavica 6; 117-124. 

Tschanz, B. 1979 Zur Entwicklung von Papageitaucherkuken Fratercula artica in Frieland 

und Labor bei unzulanglichem und ausreischendem Futerangebot . (Development 

of puffin Fratercula arctica chicks in the field and laboratory with insufficient and 

sufficient food supply.) Fauna Norvegica Series C, Cinclus 2: 70-94. (English 

summary). 

Van Pelt, T.I., Piatt, J.F., Lance, B.K. and Roby, D.D. 1997. Proximate Composition and 

Energy Density of Some North Pacific Forage Fishes. Comparative Biochemistry 

and Physiology, 1 18A (4); 1393- 1398. 

Vermeer, K, 1980. The importance of timing and type of prey to reproductive success of 

rhinoceros auklets Cerorhinca monocerata. Ibis 122:343-350. 

Vermeer, K., Cullen, L. and Porter, M 1979. A provisioning explanation of the 

reproductive failure of Tufted puffins Lunda cirrhata on Triangle Island, British 

Columbia. Ibis 12 1 : 348-354. 

Wernham, C.V. and Bryant, D.M. 1998. An experimental study of reduced parental effort 

and future reproductive success in the puffin Fratercula arctica. Journal of 

Animal Ecology 67; 25-40. 

Whele. D.H.S. 1980. The breeding biology of the puffins: tufted puffin (Lunda cirrhata), 

homed puffin (Fatercula corniculata), common puffin (F. arctica), and 

rhinoceros auklet (Cerorhinca monocerata). Ph. D. thesis, University of 

Fairbanks, Alaska. 
Chapter 13. Biology of Other Seabird Species in lower Cook Inlet 

Michael Shultz and Thomas Van Pelt 

Introduction 

Species background and study area 

This project was focused on four key seabird species; two that bred on all three colonies 

within our study area (the pelagic, deep-diving Common Murre [Chapter 91 and the 

pelagic, surface-feeding Black-legged kittiwake [Chapter lo]), and two found at one or 

more of our study colonies (the pelagic, diving Horned Puffin [Chapter 121 and the 

coastal, diving Pigeon Guillemot [Chapter 1 11). However, we also collected ancillary data 

on several other seabird species that comprise part of the seabird community in lower 

Cook Inlet. These included: 

The Glaucous-winged Gull (Lams glaucescens) is a common resident along the 

northwestern coast of North America. These large, omnivorous gulls are generally an 

inshore species, but they may also forage or scavenge from fishing vessels far out at sea. 

Glaucous-winged Gulls generally nest at high densities in large or small colonies on offshore islands, forming apparently monogamous breeding pairs with a clutch size of 1-4 

eggs (mean clutch size range 2.1-2.9 eggs; Verbeek 1993). 

The Tufted Puffin (Fratercula cirrhata) is an abundant seabird in lower Cook Inlet (Piatt 

1994, Chapter 8) and breeds in large numbers on the Barren Islands and in smaller 

numbers at Gull and Chisik islands. Tufted puffins burrow into soil where they raise one 

young in their nest chambers. They forage widely on a great variety of pelagic prey 

including sand lance, capelin and juvenile pollock (Piatt et al. 1997). Like its congener, 

the Horned Puffin, the Tufted Puffin forages offshore and sometimes far from its breeding 

colonies. 

The Pelagic Cormorant (Phalacrocorax pelagicus) and the Red-faced Cormorant 

(Phalacrocorax urile) are two of the three species of cormorants that breed in Alaska. 

They differ from the third cormorant species, the Double-crested Cormorant 

(Phalacrocorax auritus), in that they are strictly marine birds. All the cormorants tend to 

forage nearshore, and feed heavily on benthic prey. Pelagic Cormorants nest on coastal 

headlands or islands throughout Alaska and the Asian North Pacific. Red-faced 

Cormorants nest in a much smaller region of the North Pacific that stretches from northern 

Japan through the Aleutian Islands. Both species lay clutches of 3-7 eggs, with means 

from 2.9 to 3.8 eggs per nest (Hobson 1997). The Double-crested Cormorant is widely 

distributed across North America, and is commonly found along seacoasts and inland 

waters. Unlike the other cormorant species, these are gregarious birds that can form large 

colonies in diverse terrain: on the ground, on cliff-faces, and in trees or artificial 

structures. The modal clutch size for this species is 4 eggs, with a range of 1-7 eggs per 

nest. 
Our work on these species was conducted at two colonies in Cook Inlet, Gulf of Alaska, 

between May-September in 1995-1999. The colony at Chisik Island (including Duck 

Island; west side of Cook Inlet; 60" 09' N, 152" 34' W) supports a significant population 

of Glaucous-winged Gulls and Double-crested Cormorants, with small populations of 

Pelagic Cormorants and Tufted Puffins. The Gull Island colony (east side of Cook Inlet; 

59" 35' N, 151" 19' W) supports significant populations of Glaucous-winged Gulls, 

Tufted Puffins, and smaller populations of Pelagic and Red-faced Cormorants. The two 

colonies are separated by ca. 100 km and are in oceanographically distinct habitats, with 

Chisik Island surrounded by stratified, relatively warm estuarine waters and Gull Island by 

colder, mixed oceanic waters with significant freshwater runoff (Robards et al. 1999 and 

references cited therein). 

There is increasing evidence that an oceanographic 'regime shift' occurred in the Gulf of 

Alaska in the early 1980'~~ resulting in changes in seabird diets and reduction of 

reproductive success in some marine bird and marine mammal populations (Piatt and 

Anderson 1996; Anderson and Piatt 1999). These changes were similar to some 

hypothesized effects of the TN Enon Valdez oil spill (EVOS) on relatively well-studied 

seabird species such as murres and kittiwakes (see Chapters 9 and 10). It is also likely that 

other members of the seabird communities (e.g. cormorants, gulls, and puffins) have also 

been affected. 

To learn more about foraging, breeding, and population changes in colonies of Glaucouswinged gulls, Tufted Puffins, and Double-crested, Pelagic, and Red-faced Cormorants, we 

gathered data on these species at Chisik and Gull Islands, while we investigated the 

oceanography and forage fish distribution around those colonies. The purpose of this 

chapter is to summarize the methods we used and to present the results of our study in a 

format useful to other researchers. Eventually, these results may be integrated with those 

of other species to develop a synthesis of how the seabird community responds to changes 

in food supply. 

Methods 

Productivity 

Glaucous-winged Gull- We monitored Glaucous-winged Gull reproductive parameters 

from 1995-1999 at Gull and Chisik islands. Since both islands are covered in dense 

vegetation by late June, we found it nearly impossible to accurately determine individual 

chick fates and therefore followed nests only through hatching. On Gull Island, hatching 

success data were collected from 2 plots in 1995 and 5 plots in other years. Plots 

contained approximately 10 nests in 1997-1999, and 15-20 nests in 1995-1996. Plots 

were checked every five days during incubation for nest contents and every 2 - 3 days 

when chicks were expected to hatch. At Chisik Island, 2-3 productivity plots containing 

approximately 10 nests were monitored from 1997- 1999. In 1996, one plot containing 30 

nests was followed. Nests in plots were checked every 3-7 days and their contents 

recorded. In 1995, we estimated hatching success with a two-visit method. During the 
late incubationlearly chick-rearing period, areas on Duck Island known to contain nesting 

gulls were surveyed. Contents of all nests found 24 June were recorded, and nests 

containing eggs were revisited 29 June to determine egg fate. An index of hatching 

success was calculated from the numbers of chicks seen per nest counted. 

We used study plot as the sample unit for estimating each parameter, except at Chisik 

Island in 1996 where nest site was the sample unit. The mean and standard deviation of 

the plot means were used for annual estimates. Reproductive parameters are defined as 

follows: 

Hatching chronology (median hatch date) 

Hatching Success (% of eggs laid that hatch) 

Hatching Productivity (chicks hatched per nest with eggs) 

Clutch Size (eggs per nest with eggs) 

Brood Size at Hatch (chicks per nest with chicks at hatch) 

Pelagic Cormorants- We monitored Pelagic Cormorant productivity at Gull Island from 

1995-1999. In 1995-1997, all nests visible from on top of the island were followed, 

whereas from 1998-1999, nests in 11 productivity plots were followed. Nests were 

checked with 8 X 42 or 10 X 42 binoculars every 4 - 6 days from incubation through 

fledging. Nest contents (i.e. numbers of eggs and chicks) were recorded during each visit. 

Pelagic Cormorant fledging age is highly variable, however around 40 days is typical 

(Hobson et. al. 1997). We assumed chicks to have fledged if they disappeared after 40 

days of age. However, since newly hatched chicks are brooded very closely for the first 

10 days, it was difficult to obtain an accurate hatch date by direct observation. To 

account for this we assumed that a chick had "fledged" if it was present 30 days after the 

first chick observation (typically around 10 days after hatch). 

We calculated productivity estimates with nest as the sample unit from 1995- 1997 and 

plots as the sample unit for 1998 and 1999. Reproductive parameters are defined as 

follows: 

Hatching chronology (median hatch dates) 

Hatching Success (% of eggs laid that hatch) 

Productivity (chicks fledged per nest structure) 

Mean Clutch Size (eggs per nest with eggs) 

Brood Size at Hatch (chicks per nest with chicks at hatch) 

Brood Size at Fledge (fledglings per nest with fledglings) 

We obtained an index of productivity for all Pelagic Cormorant nests on Gull Island from 

1995- 1999 and on cliffs at Moosehead Point (1 km from Gull) in 1995. Adults and nests 

were counted once during mid-incubation and all visible chicks were counted just prior to 

the fledging period. Counts were completed using 8 x 40 or 10 x 40 binoculars with two 

observers in a boat 5 - 30 m off shore. Since nest contents were not visible from the 

water, nest status was inferred fi-om adult posture. Only active nests (i.e. contained 
incubating adults) were counted. Counts were averaged between observers. The same 

nests were surveyed for chicks. All chicks visible from the water were counted, and totals 

were averaged between observers. Productivity was determined from the ratio of chicks 

to nests. 

Red-faced Cormorants- An index of productivity (chicks per active nest) was calculated 

for all Red-faced Cormorant nests on Gull Island from 1995- 1998 using the same 

methodology we used for Pelagic Cormorants. 

Double-crested Cormorant- Data on this species was collected at Chisik in all years 

(1995-1999). However, the colony was located on cliff faces approximately 1250 - 1750 

m away from the observation site, at an elevation of 300 - 450 m above the observation 

site, making observations very difficult. We attempted to overcome this by using a highquality spotting scope with a 20-60x eyepiece, but observers were still unable to 

confidently identify nest contents. We attempted to delineate plot boundaries to measure 

changes in population or nesting effort, but observers had little confidence in both the 

precision of those boundaries and the counting of nests within the boundaries. In 1995, we 

were able to identi@ some Fully Feathered Chicks (FFC); giving a minimum productivity 

of 0.64 fledglings per nest (18 FFC from 28 nests). However, in 1996-1999, observers 

had little confidence in the identification of FFCs. Despite these limitations, we were able 

to estimate the population at around 8-45 nests each year on the high cliffs on the North 

East side of Chisik Island. 

Population monitoring 

We monitored populations of all species on population plots at Gull and Chisik islands, 

from 1995- 1999. Some population monitoring plots had already been established by 

USFWS Alaska Maritime National Wildlife Refuge personnel prior to the beginning of our 

study. To facilitate long-term comparisons, these historical plots were maintained; 

however, in some cases additional plots were created at the beginning of our study (1995), 

and also in later years. We therefore summarize our data separately for historic plots and 

newly created plots. 

All plots were photographed, and boundaries were clearly marked on the photographs. 

Using inflatable boats for access, binoculars for viewing, and tally-clickers to ease 

counting, all birds within the plots were counted 5-12 times during the season between 

mid-incubation and the onset of chick fledging. Sea, wind, and visibility conditions were 

recorded for each count. Counts were made between 1000 and 1600 hours (the time 

during daylight hours when attendance is most stable; see Birkhead and Nettleship 1980; 

D.E. Dragoo, unpubl. data; Boersma et al. 1995; Roseneau et al. 1995). Two observers 

counted each plot; if the difference between observers was greater than 10% of the total, 

the count was repeated. The plot total was taken as the mean of the two observer counts. 

The sample unit is the count-day, with all plot counts for the each day merged into a total. 

Plots in population counts therefore serve only as an organizational tool and not as a 

statistical unit (in contrast to productivity plots; see below). 
Attendance was most consistent from the mid-incubation through the start of chick 

fledging, but logistic complications during the field season meant that not all counts fell 

within this period. Therefore, following the field season, count 'windows' for each 

species and each colony-year were defined (based on the reproductive chronology for that 

year) as mid-incubation to the beginning of fledging. Estimates for mid-incubation were 

obtained by adding half of the incubation period for each species to peak laying date; the 

start of fledging is defined as the first chick observed to fledge from a productivity plot. 

Plot counts outside these windows were retained for archival purposes, but the summaries 

presented here use only counts made within the appropriate mid-incubation to fledging 

window. 

Since we did not monitor Tufted Puffin breeding success, we estimated breeding 

chronology based on chick ages from growth data collected in 1997. We aged chicks by 

assuming they reached asymptotic weight at around 35 days of age (Gaston et al. 1998). 

This was sufficiently accurate for our purposes given that nearly all counts fell well within 

these windows. 

We conducted whole island counts of adult Pelagic and Red-faced Cormorants and nests 

during mid-incubation in most years. Counts were completed using 8 x 40 or 10 x 40 

binoculars with two observers in a boat 5 - 30 m off shore. Two observers counted a 

section of the colony; if the difference between observers was greater than 10% of the 

total, the count was repeated. The section total was taken as the mean of the two 

observer counts. This procedure was repeated until the whole island had been censused. 

We completed whole island censuses of Glaucous-winged Gulls during incubation in 1995, 

1997, and 1998 at Gull and Chisik island. At Gull Island, the counts were completed on 

the same day between 1000- 1400. The same methods were used as for Pelagic and Redfaced Cormorant censuses, except that at Gull Island the counts were conducted from 

land. At Chisik Island, counts were completed from an inflatable boat; on Duck Island 

from land. 

Tufted Puffin chick growth 

The Tufted Puffin population at Gull Island numbers about 100 pairs, and very few of 

these burrows are accessible without disturbing nesting Common Murres (Uria aalge) and 

Pelagic Cormorants. As a result, we obtained chick growth rates for only 5 individuals in 

1997. We checked burrows every 4 days, after chicks were no longer being brooded to 

measure and weigh chicks. We measured mass with a 500 gram Pesola spring balance to 

the nearest 5 grams, flattened wing length with a 100 cm wing-ruler, and culmen (from the 

tip of the upper mandible to the anterior edge of the growing cere and tarso-metatarsus 

("tarsus") lengths with Vernier calipers. 

Results 

Glaucous-winged Gull 

Productivity- Glaucous-winged Gull productivity parameters, averaged for all years, 

were similar between Gull and Chisik Islands (Table 13.1). Clutch size was slightly higher 
at Chisik, while hatching success was slightly lower than at Gull, resulting in similar 

overall productivity (chicks hatched per nest with chicks). Gulls initiated nesting at Chisik 

Island 5 days earlier on average, than at Gull Island (Table 13.1). 

Population- Numbers of Glaucous-winged Gulls in population plots were variable 

among years, but there was no apparent trend in the population at Chisik and Gull Island 

(Table 13.2). When counts from 1995-1999 are compared to historical counts there again 

appears to be no trend in the populations at either colony (Appendix 13.1). Gulls nesting 

on 60 Foot Rock were counted only in 1995, but in light of historical estimates this small 

population may be increasing. Population plot count windows calculated from yearly 

nesting chronology are summarized and compared with the actual count windows in 

Appendix 13.2. In addition to population plot counts, colony censuses were completed in 

1995, 1997, and 1998 at Gull and Chisik islands (Table 13.3). When these data are 

compared to historical counts there is no clear trend in the data from Chisik. At Gull 

Island, the population seems to have stabilized after a fairly rapid increase during the 

1970's and 1980's (Appendix 13.3). 

Pelagic Cormorants 

Productivity- We estimated Pelagic Cormorant productivity in plots and by index 

checks, at Gull Island from 1995- 1999 (Table 13.4). Productivity of Pelagic Cormorants 

in plots was relatively consistent among years, except for 1995, when it was well below 

the average for 1996- 1999 (0.29 vs. 0.7 1 chicks per nest). Much of this low reproductive 

output in 1995 can be accounted for by a small average clutch size. We also checked the 

productivity index in all years at Gull Island (Table 13.5). Productivity estimates using 

index methods were generally much higher than those from plots, except in 1998 when the 

opposite was true. 

Population- There were no Pelagic Cormorants in population plots at Chisik Island from 

1995-1999. Numbers of cormorants in population plots at Gull Island declined from 

1995-1999 (Table 13.6). Plot counts conducted from 1986- 1994 indicate that the 

population had been stable from 1986-1988, declined noticeably in 1989 and then steadily 

increased until 1996 (Appendix 13.4). Population plot count windows calculated from 

yearly nesting chronology are summarized and compared with the actual count windows in 

Appendix 13.5. Whole island counts of adult birds and nests were conducted from 1995- 

1998. These results and those from counts completed from 1976- 1994 show a similar 

pattern as the results from population plot count data (Appendix 13.6). 

Red-faced Cormorants 

Productivity- Estimates of productivity derived from index checks showed a similar 

pattern among years as those for Pelagic cormorants (Table 13.5). However, overall 

productivity averaged among years was slightly higher for Pelagic Cormorants (Pelagic; 

mean=0.98, sd=0.59, n=4; Red-faced; mean=0.88, sd=0.61, n=4) 

Population- Whole island counts of adult birds and nests were conducted from 1995- 

1998. These results and those from counts completed from 1976- 1994 indicate a possible 
decline in the population from a high of 62 individuals in 1976 to a low of 16 in 1997 

(Appendix 13.6) 

Tufted Puffins 

We counted Tufted Puffins in population plots from 1997- 1999 (Table 13.7). Population 

plot count windows are summarized and compared with the actual time windows when 

counts were completed, in Appendix 13.7. We measured puffin chick growth in 1997 at 

Gull Island. The results for individual chicks are summarized in Table 13.8. 

Glaucous-winged Gull 

Gull identificatioe Williamsen and Petyon (1 963) collected a series of gulls from a large 

breeding colony in the Cook Inlet region, near Anchorage, Alaska, that showed 

intermediate plumage characteristics between Herring Gulls (Larus argentatus) and 

Glaucous-winged Gulls. This colony was an inland colony and surrounded several large 

lakes on the Susitna flats. Most of the gulls tended to more closely resemble Herring 

rather than Glaucous-winged Gulls, based on the extent of dark coloration in the subterminal bands of the primaries, iris color, and eye ring color. They later found evidence of 

interbreeding from other colonies around Cook Inlet and concluded that interbreeding 

between the two species is "common and widespread" in the Cook Inlet region. They also 

reported that according to knowledge of breeding distributions at the time, that 

interbreeding was only to be expected in the Cook Inlet region west to the base of the 

Alaska Peninsula and on Forrester and Muir Islands in Southeast Alaska. Patten and 

Weisbrod (1974) later mentioned evidence of inbreeding between these two species, also 

based on plumage and bare part coloration, from the Glacier Bay region. 

Glaucous-winged Gulls nesting on Gull Island also showed characteristics intermediate 

between these species. Most gulls closely resembled Glaucous-winged Gulls, but a hll 

gradient of characteristics between typical Glaucous-winged and Herring Gull phenotypes 

nested on the island. The color of the sub-terminal bands of the primaries varied from 

black to light gray and was not useful for identification. Iris color and orbital ring color 

were also equally variable. Gull Island is an offshore oceanic island that is more typical of 

Glaucous-winged Gull habitat than Herring Gull habitat. 

Productivity- Hatching success at Gull (59%) and Chisik Island (52%) was comparable 

to estimates reported for colonies elsewhere in Alaska: 67% (Patten 1974), 46% (Murphy 

et al. 1974), 62% (Baird 1990), 80% (Hatch and Hatch 1990). Clutch size values (Gull; 

2.3, Chisik; 2.4) were slightly lower than some other colonies in Alaska: 2.9 (Patten 1974) 

2.1 and 2.6 at Squab Island (Murphy et al. 1984), 2.6 (Hatch and Hatch 1990). Chisik 

Island birds initiated nesting earlier and laid larger clutches, however they also had lower 

hatching success than at Gull Island. Although we did not follow gull chicks to fledging, 

the pattern through hatching is similar to that which is seen for Black-legged Kittiwakes at 

Chisik Island: they typically lay clutches comparable and sometimes exceeding those at 
Gull Island, however hatching is noticeably lower at Chisik, and almost none of these 

chicks survive to fledge. This is probably the result of birds arriving at the start of the 

season in relatively good condition, however once they have laid eggs and become 

dependent on local resources, the paucity of food close to Chisik Island results in low net 

reproductive success. 

Pelagic Cormorants 

Productivity- Productivity values derived from plots (62%) were noticeably different 

than those derived from the productivity index counts (98%). Productivity plots 

contained only a small sample of all nests, while the index included all nests on the island. 

The productivity index is a less accurate estimate of productivity than the plot data in that 

the number of "fledglings" is actually the number of large chicks present just prior to 

fledging. Pelagic Cormorants are relatively asynchronous breeders and as a result some 

younger chicks are considered "fledged" when certainly some of these would have died 

before fledging. However, as an index of among year variability and trends in 

productivity, this method may be more desirable in that it accounts for all areas of the 

colony. 

The range of productivity values at Gull Island (plots, 0.29-0.83) was lower than that 

reported for Anacapa Island, California (1.69-2.64, Hobson 1997), but was within range 

for the Farallon Islands (0.0-2.83, Boekelheide et al. 1990). Productivity at the Farallones 

was more variable among years than at Gull Island. The range of mean annual clutch sizes 

at Gull Island (2.17-3.83) were similar to those reported from the Farallon Islands, 

California, indicating that Gull Island cormorants may have lower hatching andlor fledging 

success. Hobson (1997) reported that Bering Sea colonies have greater hatching success 

but lower fledging success than British Columbia colonies. This may be due to greater 

chick predation or the effects of weather and climate or food cycles on chicks. 

Populatioe Historic population plot counts of Pelagic Cormorants at Gull Island dating 

back to 1986 indicate that their numbers have fluctuated considerably. From 1986-1988, 

the population was stable, it dropped dramatically in 1989, steadily increased from 1989- 

1994, and then steadily declined in 1995- 1999. The overall trend from 1986-1999 has 

been a declining one, with a high of 55 birds in plots in 1986 and a low of 18 in 1999. It is 

possible that the dramatic drop in breeding birds in 1989 was due to EVOS effects, but 

this does not explain the continuing long-term decline at this colony. 

Tufted Puffins 

Chick mass growth for Gull Island in 1997 (15.75 g / day), was similar to the range of 

values reported for this species at the Barren Islands in 1976 (16.5 g/day) and 1977 (16.5 

g/day)(Amaral 1977), and to average growth from 11 different studies on the west coast 

(15.2 glday, Piatt et al. 1997). At Gull Island in 1997, food abundance was relatively high 

as evidenced by hydroacoustic surveys (Chapter 7), beach seine catches (Chapter 5) and 

by Common Murre (Urica aalge) and Black-legged Kittiwake (Rissa tridactyla) breeding 

success. 
Acknowledgments 

The work presented here is the product of many dedicated employees and volunteers. 

Stephani Zador was responsible for initiating field work on Gull Island in 1995, and over 

the years 1995- 1997, was instrumental in helping to develop and refine protocols for 

seabird data collection at all three colonies. Tom Van Pelt was instrumental in providing 

field work, camp support, and logistic coordination throughout the project. We thank 

Yumi Arimitsu, Jeb Benson, Dave Black, Leigh Ochikubo [Chan], Alice Chapman, Jared 

Figurski, Mike Gray, Greg Hoffman, Brad Keitt, Roman Kitaysky, April Nielsen, Ram 

Papish, Mike Post, Brian Smith, Shiway Wang, Jenny Wetzel, and Sadie Wright for their 

vital help with field work. We are grateful to Arthur Kettle, Vernon Byrd, and Brian 

Smith for their assistance in compiling the data archive. Sasha Kitaysky shared his research 

expertise, comradeship, and wisdom with us. Greg Snedgen gave abundant practical and 

logistical help that greatly increased the safety and efficiency of our work. Brad Keitt is 

thanked for refitting the RN David Grey, and we thank Greg Snedgen for running the 

boat during the 1997- 1999 field seasons. We thank Vern Byrd and the staff of the Alaska 

Maritime National Wildlife Refuge for their tremendous logistic support and hospitality in 

Homer. Finally we thank Mike Gaegel and staff of the Kasitsna Bay Marine Lab, the 

residents of Chisik Island, Tuxedni Channel, Halibut Cove, and Kasitsna Bay, for their 

support. 

Literature Cited 

Anderson, P. J. and J. F. Piatt. 1999. Trophic reorganization in the Gulf of Alaska 

following ocean climate regime shift. Marine Ecology Progress Series. 189: 1 17- 

123. 

Baird, P.H. 1990. Influence of abiotic factors and prey distribution on diet and 

reproductive success of three seabirds species in Alaska. Ornis Scand. 2 1 : 224- 

235. 

Birkhead, T.R. and D. Nettleship 1980. Census methods for murres, Uria species: a 

unified approach. Can. Wildl. Serv. Occas. Pap. No. 43. 25 pp. 

Boekelheide, R. J., Ainley, D. G., Huber, H. R., and Lewis, T. J. 1990. Pelagic 

Cormorant. In: Seabirds of the Farallon Islands (eds Ainley, D. G. and 

Boekelheide, R. J.), pp. 195-217. Stanford Press, Stanford. 

Boersma, P.D., J.K. Parrish, and A.B. Kettle. 1995. Common murre abundance, 

phenology, and productivity on the Barren Islands, Alaska: The Exxon Valdez oil 

spill and long-term environmental change. Pp. 820-853 in Exxon Valdez Oil Spill: 

Fate and effects in Alaskan waters, ASTM STP 1219, P.G. Wells, J.N. Butler, and 

J.S. Hughes (eds.), Amer. Soc. for Testing and Materials, Philadelphia, PA. 

Chastel, O., H. Weimerskirch, and P. Jouventin. 1995. Body condition and seabird 

reproductive performance: a study of three petrel species. Ecology 76: 2240- 

2246. 

Hatch, J.J., and D.V. Weseloh. 1999. Double-crested Cormorant (Phalacrocorax 

auritus). In The Birds of North America, No. 441 (A. Poole and F. Gill, eds.). 

131 
Hatch, S.A. and M.A. Hatch, 1990. Breeding seasons of oceanic birds in a subarctic 

colony. Can. J. Zool. 68:1664 - 1679. 

Hobson, K.A. 1997. Pelagic Cormorant (Phalacrocoraxpelagicus). In The Birds of 

North America, No. 282. (A. Poole and F. Gill, eds.). 

Hobson, K.A., J. Piatt, and J. Pitocchelli. 1994. Using stable isotopes to determine seabird 

trophic relationships. J. Anim. Ecol. 63: 786-798. 

Gaston, A.J. and Jones, I.L. (1998) The Auks. Oxford University Press, Oxford. 

Murphy, E.C., R.H. Day, K.L. Oakley, and A.A. Hoover. 1984. Dietary changes and 

poor reproductive performance in Glaucous-winged Gulls. Auk 10 1 : 532-54 1. 

Murphy, E.C., A.A. Hoover-Miller, R.H. Day, and K.L. Oakley. 1992. Intracolony 

variability during periods of poor reproductive performance at a Glaucous-winged 

Gull colony. Condor 94: 598-607. 

Patten, S. M., Jr. and Weisbrod, A.R. 1974. Sympatry and Interbreeding of Herring and 

Glaucous-winged Gulls in Southeastern Alaska. Condor 76: 343-344. 

Patten, S. M., Jr. 1974. Breeding ecology of the Glaucous-winged Gull (Larus 

glaucescens) in Glacier Bay Alaska. M.Sc. thesis, Univ. Washington, Seattle. 

Piatt, J.F. 1994. Oceanic, shelf, and coastal seabird assemblages at the mouth of a tidallymixed estuary (Cook Inlet, Alaska). OCS Study MMS 93-0072, Final Rep. for 

Minerals Management Service, Anchorage, Alaska. 

Piatt, J. F. and P. Anderson. 1996. Response of common murres to the Exxon Valdez Oil 

Spill and long-term changes in the Gulf of Alaska marine ecosystem. American 

Fisheries Society Symposium 18: 720-737. 

Piatt, J.F., D.D. Roby, L. Henkel, and K. Neuman. 1998. Habitat use, diet, and breeding 

biology of Tufted Puffins in Prince William Sound, Alaska. Northwestern 

Naturalist 78: 102- 109. 

Robards, M.D., J.F. Piatt, A.B. Kettle, A.A. Abookire. 1999. Temporal and geographic 

variation in fish communities of lower Cook Inlet, Alaska. Fish. Bull. 97: 962-977. 

Roseneau, D.G., A.B. Kettle, and G.V. Byrd, 1995. Common murre restoration 

monitoring in the Barren Islands, 1993. Restoration Project No. 93049. Unpubl. 

final rept., U.S. Fish Wildl. Serv., Homer, AK. 

Verbeek, N.A.M. 1993. Glaucous-winged Gull (Larus glaucescens). In The Birds of 

North America, No. 59 (A. Poole and F. Gill, Eds.). 

Wehle, D.H.S. 1980. The breeding biology of the puffins: Tufted Puffin (Lunda 

cirrhata), Horned Puffin (Frcatercula corniculata), Common Puffin (F. arctica) 

and Rhinoceros Auklet (Cerorhinca monocerata). Ph.D. thesis. University of 

Alaska, Fairbanks. 

Williamson, F.S.L. and Peyton, L.J. 1963. Interbreeding of Glaucous-winged and Herring 

Gulls in the Cook Inlet Region, Alaska. Condor 65: 24-28. 
Chapter 14. Response of Seabirds to Fluctuations in Forage Fish Density: 

Can Seabirds Recover from Effects of the Exxon Valdez oil spill? 

John Piatt 

Introduction 

This chapter contains a synthesis of five years (1995- 1999) of study in lower Cook Inlet. 

Some initial findings have been published (see Chapter 1) and we continued to collect 

data on some seabird parameters (e.g., foraging behavior, reproductive success, survival, 

stress, etc.) in summers of 2000 and 2001. For this synthesis, the focus will be on 

Common Murres and Black-legged Kittiwakes because these were the bird species of 

primary interest in the study, and the species for which data were collected at all three 

colony sites in lower Cook Inlet. 

First, I will review the background for this study and discuss the theoretical 

considerations that went into the study design. Second, I will provide a summary of the 

major findings about the marine ecosystem in lower Cook Inlet (as presented in Chapters 

2-7) and discuss the implications for seabirds. Third, I will summarize how seabirds 

responded to variation in food supply-- the major focus of this study. Finally, I will 

consider what the data suggest about the status of seabird populations in the Gulf of 

Alaska, and the likelihood that seabird populations can recover from effects of the Enon 

Valdez oil spill. 

Background 

Why the Study was Initiated 

Immediate impacts of the Exxon Valdez oil spill (EVOS) on seabirds in 1989 were 

well-documented. Common Murres comprised most (74%) of oiled bird carcasses 

recovered fiom beaches (>30,000) and a variety of direct and indirect evidence suggested 

that about 250,000 seabirds were killed (Piatt and Ford 1996). Putative short-term effects 

on murres included a reduction in populations at affected colonies, delayed breeding 

phenology and low reproductive success (Nysewander et al. 1993). The greatest impact 

was in the Gulf of Alaska and particularly lower Cook Inlet, where large numbers of 

murres were beginning to gather near breeding colonies when oil swept through the 

region in April and May. Models of murre population dynamics (Ford and Wiens et al. 

1982) suggested that it could take 20-70 years for murre populations to recover to a stable 

age distribution if environmental conditions were favorable (Piatt et al. 1990). 

However, evidence accumulated during the 1990's that environmental conditions were 

not favorable to seabirds in years following the oil spill. A "regime shift" had occurred in 

the Gulf of Alaska (GOA) during the late 1970ts, apparently resulting in marked changes 

in seabird diets, lowering of reproductive success and population size, and occasional 
'wrecks' (large-scale die-offs) in some marine bird and mammal populations (Piatt and 

Anderson 1996, Francis et al. 1998). Furthermore, this regime shift appeared to affect 

seabirds in ways similar to hypothesized effects of the spill. This new information raised 

several questions: To what degree were seabirds affected by natural changes in the GOA 

environment before the spill? Could effects of the spill be separated from natural 

variability? In light of the regime shift, what was the current status of seabird populations 

in the GOA and how long would it take murres and other seabirds to recover from effects 

of the spill? 

To address these questions, the EVOS Trustee Council (EVOSTC) initiated the Apex 

Predator Ecosystem Experiment (APEX) in 1994 to assess whether current conditions 

favor a recovery of seabirds from the spill. Initially focussed on Prince William Sound, 

APEX studies expanded in 1995 to include Cook Inlet, where hnding and logistic 

support from the U.S. Geological Survey, U.S. Fish and Wildlife Service, Minerals 

Management Service, and the Alaska Department of Fish and Game made it possible to 

conduct seabird and forage fish studies around three colonies (Chisik, Gull and Barren 

islands) that had been impacted by the oil spill. In Cook Inlet, investigations included 

studies on oceanography and forage fish biology, distribution and abundance; and at 

colonies, studies of seabird foraging behavior, diets, time-budgets, chick growth rates, 

physiological condition and reproductive success. Most data were collected on Common 

Murres and Black-legged Kittiwakes, which breed at all colonies studied in lower Cook 

Inlet. Ancillary data were also collected on other species (Glaucous-winged Gulls, 

Pelagic Cormorants, Tufted and Horned Puffins, and Pigeon Guillemots); of which only 

Glaucous-winged Gulls breed at all colony sites. In this preliminary synthesis, we will 

restrict our analysis and discussion to murres and kittiwakes. Consideration of the entire 

marine bird community will follow when all data have been compiled and analyzed. 

Theoretical Considerations and Study Design 

The main question in 1995 was: Is the recovery of seabirds in Cook Inlet currently 

limited by food supply? The response of seabirds to environmental change can vary 

widely among species, and is influenced by a host of physical and biological factors. 

Differential adaptations of seabirds for exploiting plankton and fish, widely-varying 

foraging abilities and breeding strategies, and complex relationships between 

oceanography and prey dispersion, abundance, and behavior all serve to complicate our 

interpretation of changes in seabird population biology. Therefore, in order to assess the 

potential for recovery of seabirds affected by the Exxon Valdez oil spill, a concurrent, 

multi-disciplinary study of oceanography, forage fish, and seabirds was required. 

Coordinated studies of seabird breeding biology and feeding ecology in relation to prey 

abundance are rare (e.g., Safina and Burger 1985, 1988; Piatt 1987, 1990; Monaghan et 

al. 1989, 1994; Hamer et al. 1991, 1993; Uttley et al. 1994). Nonetheless, results of these 

studies provided an empirical basis for hypotheses about relationships between seabirds 

and their prey in lower Cook Inlet (Chapter 1). Relationships between seabirds and their 

prey can be quantified within an established framework of predation theory (Holling 

1959; Murdoch and Oaten 1975; Piatt 1987). Population change (the "numerical 

response") in higher vertebrates depends largely on the rate at which food (energy) can be 
extracted from the environment (the "functional response"). Predator responses to 

changing prey density are usually non-linear in form and often exhibit threshold 

dynamics. 

The challenge in this study was to measure the form and scale of seabird responses to 

prey fluctuations in light of variability in the marine environment of lower Cook Inlet and 

difficulties in measuring food abundance. Quantifying responses of higher vertebrates in 

the field can be difficult because of logistical difficulties in measuring key parameters 

(Goss-Custard 1970), and the lack of power to manipulate predator and prey densities 

over the full range of possible values (Piatt 1990). 

In this study, we set out from the beginning to study seabirds and prey resources at 

colonies known from historical work to be chronically failing (Chisik I.), thriving (Gull 

I.) and possibly stable or recovering from the oil spill (Barren I.). Our hope was that 

these historic differences did indeed result from regional differences in food supplies, and 

that by studying all three colonies for five years we would obtain enough data to 

construct response curves for important seabird parameters (recognizing that it takes one 

year to obtain one data point per parameter, e.g., breeding success versus food density). 

Further, we hoped that this approach would allow us to examine a variety of parameters 

simultaneously in order to determine which parameters are most strongly influenced by 

food abundance, and how responses might vary among species in terms of thresholds, 

sensitivity and variability. 

Before we examine relationships between seabirds and food supply, I will review our 

general findings about the Cook Inlet marine ecosystem and how seabirds exploit food 

resources in this system. 

The Marine Ecosvstem in Lower Cook Inlet 

Oceanography and Biological Productivity 

The engine that drives productivity in lower Cook Inlet is the persistent upwelling of 

cold, nutrient-rich water at the entrance to Cook Inlet. A plume of cold GOA water that 

extended from the Barrens to Kachemak Bay was evident in all AVHRR images of sea 

surface temperature analyzed in 1995-1999, and persisted throughout summer in all years 

(Chapter 2). High concentrations of nitrates and silicates were associated with this plume, 

and these nutrients supported high levels of primary productivity in the plume and 

especially in stratified waters adjacent to the plume in Kachemak Bay (Chapter 3). 

Phytoplankton production intensified in the upper 30m as stratification developed in 

May, and continued with varying intensity throughout summer-- suggesting a periodic 

replenishment of surface nutrient levels following the mixing of surface layers by wind 

events. Waters on the west side of lower Cook Inlet were oceanographically distinct 

(warmer, less saline, weakly stratified, turbid, outflowing), and much less productive. A 

distinct front between western and eastern waters was always observed on cross-inlet 

transects (Chapter 2), and primary production west of this front never approached levels 

observed east of the front (Chapter 3). 
The east-west difference in oceanography and primary production was reflected at all 

higher trophic levels. The abundance of zooplankton (Chapter 3), forage fish both 

offshore (Chapter 4,7) and nearshore (Chapter 5,7), and seabirds (Chapter 8) was in all 

cases 1-2 orders of magnitude higher on the east side of lower Cook Inlet (Figs. 14.1- 

14.3). In contrast, species diversity was higher in the west and many fish species (e.g., 

sandfish, eulachon, smelt) were largely restricted to these waters (Chapter 4). The growth 

rate of resident forage fish such as sand lance was significantly lower in Chisik waters 

than in Kachemak Bay. Initially, we thought that sand lance growth was similar among 

areas, until examination of otoliths and growth rates revealed that fish of the same length 

were, in fact, one year older at Chisik (Robards 2000). Thus, all evidence suggests that 

lower Cook Inlet is segregated into two distinct oceanographic domains with striking 

differences in productivity and biology among them. 

Whereas the east-west contrast in oceanography and productivity accounted for most of 

the spatial variation in biology observed in lower Cook Inlet, other sources of variability 

were also evident in the eastern domain. The well-mixed, cold waters in the lower inlet-- 

particularly offshore-- were dominated by juvenile pollock and capelin, whereas sand 

lance and herring preferred stratified coastal waters of the Kenai Peninsula and 

Kachemak Bay, and shallow offshore waters north of Kachemak Bay (Chapters 43. The 

overall abundance of zooplankton and fish was much higher in stratified coastal waters of 

Kachemak Bay and along the Kenai Peninsula than in mixed, cold, offshore waters of the 

lower inlet (Chapters 3,7). Finally, fish were markedly variable in the vertical dimension 

as well. Most acoustic biomass was concentrated in the upper 30m in all areas, but in 

Chisik and Barrens waters, schools were also concentrated at depths of 60- 100m. There 

was also a clear segregation of species by water depth; sand lance and herring dominated 

above depths of 40m, whereas pollock and capelin dominated below 60m. 

In summary, the areal patterns of productivity in lower Cook Inlet are largely a hnction 

of the bathymetry and oceanography. The bottom topography of the region steers GOA 

water into the shallow Cook Inlet estuary and ultimately structures nearshore and 

offshore habitats in all areas. The inflow of cold, nutrient-rich GOA water in the eastern 

domain and outflow of warmer, low-salinity water in the western domain creates the 

basic oceanographic setting for plankton, fish and seabirds. Mid-inlet fronts, eddies, 

stratification, mixing, river outflow, and winds all have some influence on local patterns 

of productivity, but the meso-scale (10's to 100's km) pattern is one of stability and 

persistence. Biological patterns of abundance and distribution persisted among years 

because the basic underlying oceanography changed little among years. This suggests 

that food supplies for seabirds are a lot more predictable than one might expect-- at least 

in terms of the meso-scale distribution of forage fish biomass. 

Seabird Foraging Ecology 

The distribution of seabirds at colonies and at sea in Cook Inlet reflects regional patterns 

of productivity and forage fish abundance. More seabirds breed in lower Cook Inlet than 

throughout the entire NE Gulf of Alaska (GOA), including Prince William Sound (Sowls 

et al. 1978). Densities of seabirds at sea were generally high in the eastern cold-water 
domain of lower Cook Inlet, and equaled those observed in extremely productive habitats 

elsewhere in Alaska such as the Bering Shelf edge and Bering Strait. 

Different seabird species foraged in different domains in Cook Inlet, and sometimes in 

different habitats within those domains (Chapter 8). Oceanic species such as Northern 

Fulmars, Fork-tailed Storm-petrels, Ancient Murrelets, and phalaropes were found mostly 

in oceanic waters to the west and south of the Barrens or in frontal waters between the 

west and east domains in lower Cook Inlet. Shearwaters and Tufted Puffins were 

extremely abundant around the Barren and Shuyak islands, and were tightly associated 

with the cold-water plume in the eastern domain. Horned Puffins, which breed in 

abundance only at Chisik and feed almost entirely on sand lance (Chapter 12), foraged 

mostly in waters on the north side of Kachemak Bay where sand lance dominated in trawl 

catches. Pigeon Guillemots, which typically forage close to home and feed largely on 

benthic fish and sand lance found near shore (Chapter 11) were rarely encountered away 

from the coast, and populations were concentrated along the south shore of Kachemak 

Bay and the Kenai Peninsula. Marbled Murrelets, which feed mostly on sand lance, were 

widely distributed in all areas but were particularly abundant along the shores of 

Kachemak Bay and the Kenai Peninsula, and offshore on the north side of Kachemak 

Bay. 

Murres and kittiwakes exhibited markedly different foraging distributions. Murres were 

dispersed throughout the study area, and their distribution was very similar to the overall 

distribution of acoustic biomass (Chapter 7)-- i.e., concentrated in coastal areas of 

Kachemak Bay and the Kenai Peninsula, offshore north and east of the Barren islands, 

and extending north into the Chisik survey area as far as the cold-water plume extended 

in any given year. Thus, murres appear to routinely travel 20-60 km to forage from the 

Barren islands, 10-40 km from Gull Island, and at least 30-60 km from Chisik Island. 

In contrast, kittiwakes were concentrated near shore in all areas, and only a few scattered 

flocks were observed offshore (in the central and northern parts of the cold-water 

plume). Kittiwakes in Kachemak Bay foraged mostly along the south shore, and 

generally within 5-30 km of the colony at Gull Island. Few kittiwakes were observed on 

the water between the Barren Islands and the Kenai Peninsula, and we assume that 

Barrens birds must fly at least 25-40 km before finding prey. Other than a small, coastal 

shoal south of Chisik, there appeared to be no good coastal foraging areas around Chisik 

Island, and birds foraged 25-50 km offshore in the direction of Kachemak Bay. 

Diets of adult murres and kittiwakes reflected food supplies around each colony. Whereas 

more than 90 species of fish were caught near shore, and 40 species were caught in 

offshore trawls, communities were overwhelmingly dominated (>95%) by four species: 

sand lance, herring, pollock and capelin (Chapters 4-6). Diets of adult murres and 

kittiwakes were dominated by the same species in similar proportions to local abundance 

except that herring were generally eaten less and capelin eaten more in proportion to their 

relative abundances (Chapters 9,lO). Sand lance dominated murre and kittiwake diets at 

both Chisik and Gull, while pollock comprised a much larger proportion in diets of birds 

from the Barrens. Less common fish species with restricted distributions were observed 
in diets of local birds (e.g., smelts, eulachon, and sandfish at Chisik, cods in Kachemak). 

The size classes of prey eaten by adults was similar to the size classes caught in trawls 

and seines. Taken together, the evidence suggests that adult murres and kittiwakes 

generally eat what is most available to them within foraging range of their colonies. 

In contrast to adult diets, chick diets were poor indicators of relative prey availability. 

Murres in all areas fed chicks a much higher proportion of osmerids (capelin at Barren 

and Gull islands, smelts at Chisik) than was available in local waters. Sand lance, herring 

and juvenile salmon (at Chisik) comprised most of the remaining chick diets. Similarly, 

kittiwakes chick diets were dominated by sand lance, with herring and osmerids 

comprising most of the remainder. Clearly, adult murres and kittiwakes choose to feed 

their chicks prey that are oily and rich in calories, a behavior frequently observed in other 

seabird species and of obvious adaptive value. In general, and despite colony differences 

in composition, diets of murre and kittiwake chicks were similar among colonies in terms 

of energetic value because where one prey was scarce (e.g., capelin) it was replaced in 

chick diets elsewhere by prey of similar energetic value (e.g., sand lance or smelt). Much 

greater variability was observed in the rates of food delivery than in the energetic content 

of meals (Chapters 9,lO). 

The choice of where to feed, and what to feed upon, has direct consequences for all other 

aspects of seabird breeding biology. For example, kittiwakes from the Barrens must 

travel at least 25 km before they even begin their search for suitable patches of food 

along the Kenai Peninsula whereas kittiwakes at Gull Island can often find prey within 1 

km of the colony. The effort expended by Barrens' kittiwakes is rewarded, however, 

because they generally locate high density patches of prey and deliver large (multiplefish) meals back to their chicks. Chisik Island kittiwakes spend as much time foraging as 

Barrens' birds, but have difficulty finding any prey patches. Consequently they deliver 

smaller meals to chicks less frequently, and usually fail to rear chicks to fledging. 

In contrast, murres can deliver only one fish at a time to chicks and foraging range 

imposes an even greater constraint on chick-rearing murres than it does on kittiwakes. 

Murres from the Barrens may fly only 10-20 km to locate pollock or capelin schools 

(although they may have to dive >40 m to obtain food), whereas murres from Chisik 

must fly 30-60 km to exploit sand lance concentrations in northern Kachemak Bay. 

Thus, even before the effects of annual variability in prey abundance are felt (see below), 

these species- and location-specific foraging constraints must affect parental foraging 

effort and total parental investment in reproduction differently at each colony. These 

relationships will be examined in detail in Wre analyses and publications. Preliminary 

analyses suggest that variation in food abundance is still the overwhelming factor 

influencing seabird behavior and biology, and we will now consider some gross patterns- 

- acknowledging that some of the "noise" in these patterns can, in fact, be explained by 

local constraints on biology. 
Response of Seabirds to Variation in Food SuppIv 

The numerical and functional responses of animals to changes in prey density are almost 

always non-linear and co-existing species that feed on shared prey resources usually 

respond differently to fluctuations in prey density (Holling 1959; Murdoch and Oaten 

1975; Piatt 1990; Piatt and Methven 1992). In this study, we set out to measure and 

contrast the form of murre and kittiwake responses to variation in forage fish density in 

lower Cook Inlet. We measured a variety of functional and numerical response 

parameters of seabirds at three different colonies, while simultaneously measuring the 

abundance of prey around those colonies. 

For convenience, we can expand on the term "functional responsew-- which Holling used 

specifically to describe the relationship between a predator's rate of prey consumption 

and prey density-- to include all parameters related to foraging and capture of prey, 

delivery of prey to offspring, aggregation at sea, foraging time budgets, or even 

maintenance of body condition. For seabirds, functional response parameters are 

typically measured over time-scales of minutes to days, and spatial scales of meters to 

10's of kilometers. In theory, we could have measured functional response parameters on 

an hourly or daily basis and constructed response curves with measures of prey density 

collected over the same time periods. Similarly, predator-prey aggregation response 

curves can be constructed from line transect data collected over hours (e.g., Piatt 1990), 

and we are analyzing our own survey data for that purpose (Speckrnan, in prep.). In 

practice, however, it generally required 3 weeks to measure prey density within seabird 

foraging range of our three study colonies, and logistic constraints and funding limited 

this effort to once per breeding season. Therefore, our analyses of functional response 

parameters use data that were collected periodically during the breeding season and then 

averaged to obtain one mean value to regress against one mean value of prey abundance 

obtained in each colony area per year. 

Similarly, Holling used the term "numerical response" to specifically describe the 

relationship between a predator's rate of population change and prey density. Again, we 

can expand this definition in our study of seabirds to include components of population 

change such as hatching, fledging or breeding success, recruitment, and survival. These 

parameters arc+- in the absence of stochastic mortality events (e.g., from severe weather, 

oil pollution, etc.)- mostly a function of food availability over longer time scales 

(months and years) and larger spatial scales (100's to 1000's of kilometers). Thus, 

population change in seabirds reflects day-to-day foraging success integrated over 

reproductive time-periods and the area over which populations are distributed (Cairns 

1987, 1992a,b; Piatt 1987). In practice, we obtained one measure of each numerical 

response parameter per colony per year, and regressed that against the mean density of 

forage fish observed around each colony during the early chick-rearing period in each 

summer. 

The Parameters 

We measured forage fish abundance within a 45 km range of each colony by conducting 

systematic hydroacoustic surveys supplemented with mid-water trawls to classify targets 
(Chapter 7). These data were reduced to a single estimate of mean biomass per colony per 

year (Figure 14.1). Trawl and seine data are not used for examining response curves 

because they are point measures of abundance, and biased (e.g., trawls were conducted 

only where significant acoustic sign was observed). 

We measured a variety of parameters (Figs. 14.2 and 14.3) at colonies for Common 

Murres (COMU) and Black-legged Kittiwakes (BLKI). Details of methods for data 

collection are found in Chapters 9 and 10, although additional details are provided here 

for some parameters. 

Functional response parameters that involved behavior included: aggregation of birds at 

sea (foraging bird density), attendance of adults at nest-sites, chick-feeding rate, and 

foraging trip duration. Foraging density at sea was calculated by dividing the total 

number of birds observed on the water on strip transects in each area by the total number 

of square kilometers surveyed in that area (i.e., we have not binned the data into smaller 

transect units and calculated mean + s.d. densities. The question of appropriate scale for 

grouping data will be addressed in future analyses, Speckman in prep.). There were 

methodological problems with the bird census data collected in 1995 and these results are 

not included in the present analysis. Attendance data can be expressed two ways. First, 

we can express attendance data in mean bird-minutes of attendance per nest per hour. For 

example, if only one member of a nesting pair attends the nest in every hour of the day, 

then mean attendance is 60 bird-min/hr. If at least one member is present all day, and 

both members of a pair are present for 15 minutes of every hour all day, then mean 

attendance would be 75 bird-min/hr. In the latter case, birds would have an extra 4 hours 

(16*15/60) of discretionary time in a 16 hour day that could be used for other activities. 

Discretionary time is calculated as the percentage of each hour that both members of a 

breeding pair are present. Thus, 75 bird-min/hr of attendance equals 25% of each hour 

with discretionary time (100*(75-60)/60). Foraging trip durations were determined from 

observations of birds with known departure times that returned with food for chicks, and 

therefore represent that amount of time taken by the adult to feed itself and gather food 

for its young. 

Functional response parameters that involved physiology included: chick growth rate 

(BLKI only), fledgling body condition (COMU), age at fledging (COMU), and adult 

body mass (COMU) or condition (BLKI). For kittiwakes, we could measure growth rates 

of alpha and beta chicks by taking repeated measures of mass over time at selected nestsites. We could not measure fledgling body condition in kittiwakes because large chicks 

come and go from nests and it was never clear when "fledging" had actually occurred. In 

any case, growth rates are a good proxy for fledgling body condition. For murres, we 

could not measure growth rates of chicks because it caused too much disturbance at the 

colony. However, we could capture fledglings (jumplings) on evenings when they 

jumped to sea from their nest sites, and therefore could obtain a good measure of 

fledgling body condition. Age at fledging for murres was calculated from plots where we 

studied breeding phenology. Two data sources were used to assess body condition of 

adults: adults captured at colonies for stress studies or birds collected at sea for diet 

studies. In either case, we used only data collected during late July-early August to 
compare with fish abundance data collected on cruises at that time. For murres, we 

examined absolute body mass because birds from all three colonies were identical in size 

and there is no need to calculate a "condition index" of mass/wing-length which corrects 

for size differences among colonies. For kittiwakes, size did differ slightly among 

colonies, probably because of differing ratios in collections of males and females (which 

are dimorphic). Therefore we examined body condition indices (mass/wing-length) in 

kittiwakes. Finally, we examined physiological levels of stress by measuring blood 

plasma concentrations of corticosterone (Kitaysky et al. 1999). These data will be 

analyzed and interpreted in detail under a different EVOSTC funded project (00479). 

Numerical response parameters included clutch size (BLKI), laying success (BLKI), 

hatching success, brood size at fledging (BLKI), fledging success, and overall breeding 

success. These parameters have self-explanatory names, and details of how they were 

measured are given in Chapters 9 and 10. Since murres lay only one egg and they do not 

build nests, clutch size, brood size and laying success were not measured. 

Our original ambition was to obtain data on each parameter from each colony in every 

year (i.e., 15 colony-years of data per parameter) in order to have a robust data set with 

which to construct response curves (Chapter 1). We generally succeeded in obtaining 12- 

15 colony-years of data for most parameters (Figs. 14.2, 14.3) , but in some cases we 

could not do so well because of logistic constraints (e.g., measuring COMU chick age at 

fledging not feasible at Barrens), because of biological constraints (e.g., kittiwakes rarely 

produced enough chicks at Chisik to allow measures of adult attendance, chick-feeding 

rate, foraging trip duration, or chick growth rates), or because it took years to refine our 

methods (e.g., capture of COMU jumplings at night). 

With only one exception, all data collected on all murre and kittiwake parameters are 

included in the following analyses of response curves and inter-annual variability. In 

other words, no data have been culled, and if a particular colony-year of data is missing 

(Figs. 14.2, 14.3) it is because it was not collected for reasons given above. Out of 266 

colony-year-species parameter values considered here, only 3 were excluded from 

analyses. These were behavior data on kittiwake attendance, chick-feeding rate, and 

foraging trip duration collected at the Barrens in 1997 (open circles in Fig. 14.5). These 

data were all calculated from the same observational data set, and for some reason all 

have improbable values; suggesting some systematic bias. We will re-examine these data 

at a later time, but for now I have simply excluded them in statistical analyses. 

Functional and Numerical Responses to Fluctuations in Prey Density 

We predicted (Chapter 1) that both murres and kittiwakes would exhibit non-linear 

functional responses to prey density. Responses can be positive or negative. We did not 

measure all the parameters initially proposed for study (Table 1. l), and we added a few 

along the way. In all cases, we tested the strength of relationships using a variety of linear 

and non-linear models, and selected models that best fit the data (Table 14.1). More than 

half of all relationships were, in fact, non-linear and prey density explained a significant 

amount of variation in parameter values. In the following, we will consider predicted and 
observed relationships on a case by case basis, and discuss some of the implications of 

observed relationships (or lack thereof). 

We are not just interested in the form of relationships between parameters and prey 

abundance. By contrasting results obtained under a variety of conditions, we also gain 

insight into the range of parameter values likely to be encountered under 'natural' 

conditions. This offers insight into the biology of murres and kittiwakes-- especially 

when we also consider species-specific adaptations and constraints for dealing with 

changes in food abundance. 

Behavioral Parameters 

First, we consider parameters that require a behavioral response to changes in prey 

density. These parameters relate to the acquisition of food energy from the local 

environment, i.e., tracking food at sea (flock dispersion), foraging success away from the 

colony (as indicated by foraging trip duration), success in feeding chicks (measured as 

daily rate of meal delivery) and foraging effort (indirectly indicated by the re-allocation 

of discretionary time to foraging). In general, very little is known about how these 

parameters vary with food supply for any seabird species, and I will explore our findings 

for murres and kittiwakes in some detail. 

Dispersion at sea 

The distribution of murre and kittiwake flocks at sea reflected the distribution of prey: 

70-80% of the variance in bird density in the 3 study areas was explained by forage fish 

density using a sigmoidal (logistic) regression model (Figs. 14.4, 14.5; Table 14.1). This 

form of aggregative behavior was predictable. Most higher vertebrate predators studied to 

date exhibit thresholds in their choice of foraging patches (Murdoch and Oaten 1975, 

Piatt and Methven 1992) and seabirds are no exception (Piatt 1990, Mehlum et al. 1999). 

The simplest explanation for this behavior is that predators seek to maximize their rate of 

energy intake, and therefore spend little time in areas where prey densities limit capture 

rate (Hassell and May 1974). More detailed analyses of aggregation behavior as a 

knction of spatial scale are being conducted (Speckman, in prep). 

Inflection at the threshold was sharp for murres, resulting in more of a step-hnction than 

a sigmoidal curve. The steepness of the response around the threshold explains why we 

observed a dramatic decline in bird densities in Kachemak Bay when forage fish densities 

dropped to around threshold values in 1999 (Fig. 14.1). Both murres and kittiwakes were 

conspicuously scarce in traditional feeding areas in 1999 (Figs. 8.1 and 8 .2). 

The sigmoidal nature of the aggregation response reveals that murres and kittiwakes do 

have definable limits in their ability to locate and capture prey in local waters. This 

foraging constraint has an impact on all other parameters of seabird ecology. If prey 

densities within the 45 km area we surveyed around each colony fall below threshold 

levels, then birds must range fkther from colonies- if possible- to find food. 

Otherwise, they fail to adequately provision chicks or themselves, with predictable 

consequences for reproduction. 
Foraging trip duration 

As predicted, foraging trip duration (FTD) for both murres and kittiwakes was a nonlinear, negative hnction of forage fish density (Fig. 14.4, 14.5). As discussed above 

(Seabird Foraging Ecology), the functional relationship is confounded by the fact that 

good foraging grounds are found at different distances away from each colony, and so 

foraging tip durations (FTD's) are not just a function of food abundance-- particularly for 

kittiwakes. Nonetheless, variation in food density accounted for about 50-60% of 

variation in FTD's using a negative exponential model (Table 14.1). 

Under a range of moderate to high food densities, murres were absent for about 2 hr per 

foraging tip whereas kittiwakes were absent about 3 - 3.5 hr per trip. As prey density 

fell, FTD's increased exponentially with murres foraging 3-4 hrs and kittiwakes foraging 

5-6 hrs [note these are averages, some individuals foraged much longer]. Regression of 

data measured at Gull and Chisik, which are less confounded by travel to distant foraging 

grounds, suggests that-- all else being equal-- kittiwakes spend about 1.4 hr more than 

murres on foraging trips (r2=0.65, p=0.05, FTDBLKl = O.~~*FTDCOMU + 82). Similar 

values and inter-specific differences in FTD's were observed during years of 'good' and 

'poor' food supply at Sumburgh Head, Shetland, where murre foraging trips averaged 1.3 

and 3 hours, respectively (Monaghan et al. 1994), while kittiwake foraging trips averaged 

2.3 and 6.2 hr, respectively (Hamer et al. 1993). Average murre (3.6 hr) and kittiwake 

(5.0 hr) foraging times at Bluff, Alaska, also differed by 1.4 hr (Watanuki et al. 1992). 

Average Common Murre foraging trips at the Gannet Islands, Labrador were 1.3 and 1.6 

hr in 1982 and 1983, respectively (Birkhead and Nettleship 1987). 

These results suggest that kittiwakes are less efficient than murres in acquiring food. 

Murres must acquire more food than kittiwakes to sustain themselves each day because 

of their differences in body size (average in Cook Inlet ca. 1040 g vs. 405 g, 

respectively), costs of flight (wing loading: 1.86 glcm2 vs. 0.39 glcm2; Gabrielsen 1994) 

and foraging method (diving vs. surface-feeding). From measures of field metabolic rates 

(FMR) during chick-rearing of Common Murres and Black-legged Kittiwakes 

(Gabrielsen 1994), and assuming an 87% assimilation efficiency (Romano 2000), we can 

calculate that murres (2.14 Wd/g FMR) and kittwakes (2.03 kJ/d/g FMR) feeding on 

sand lance (<I00 mm, ca. 5.0 kJ/g wet; van Pelt et al. 1997, Anthony et al. 2000) would 

need to eat 5 12 g and 189 g, respectively, of fish per day (or 49% and 47% or their body 

masses, respectively). [Note that respective values for juvenile pollock (3.5 W/g, 74% 

assimilation) would be 859 and 3 17 glday, or 83% and 78% of body mass]. 

In addition to food for self-maintenance, and on average for the chick-rearing period, 

murres need to acquire about 200 kJ/d of extra food to feed chicks (Gabrielsen 1994) 

whereas kittiwakes need to collect about 420 kJ/d extra (Gabrielsen 1994). This 

represents an increase above self-maintenance of 8% and 44%, respectively. Thus, in 

order to rear one chick to fledging, including self-maintenance costs, murres and 

kittiwakes would have to gather 552 and 273 g of sand lance daily, or 53% and 67% of 

adult body mass, respectively. [Respective values for juvenile pollock would be 789 and 

390 gld, or 76% and 96% body mass]. For kittiwakes rearing two chicks, the cost of self 

maintenance goes up (2.29 kJ/d/g; Gabrielsen 1994) and chick demands double (840 
kJ/d) so that adults would need to acquire 38 1 g of sand lance per day, or 94% of body 

mass daily. [Respective values for pollock: 544 g/d, 134% body mass]. 

Thus, parent murres need to acquire about twice as much food each day as parent 

kittiwakes and they typically acquire what they need in about half the time. This 

difference in efficiency probably arises mostly from the fact that kittiwakes are restricted 

to feeding only on schools of fish found within ca. 0.5m of the sea surface (Baird 1994), 

whereas murres can dive to depths of ca. 200m (Piatt and Nettleship 1985) and can 

therefore exploit virtually the entire water column of lower Cook Inlet. Even if most of 

the exploitable fish biomass is above 50 m (Chapters 4,7), murres still have access to 100 

times more foraging habitat than kittiwakes at any distance from a colony. Furthermore, 

we observed that surface-shoaling behavior of fish occurred mostly in coastal waters, and 

so kittiwake foraging habitat was more restricted than murre habitat in the horizontal 

dimension as well. Finally, murres (ca. 80 kmhr) can fly faster than kittiwakes (ca. 60 

kmhr) and can therefore range further in a given time period. This may be particularly 

valuable when daylight is limiting (below). Because potential foraging area increases as a 

function of the distance from colony squared, murres can access nearly twice (1.8~) the 

area kittiwakes can in the same amount of flight time. 

Chick-feeding rate 

Because FTD's increase exponentially as prey densities fall, the ability of murres and 

kittiwakes to feed their chicks diminishes rapidly at low prey densities owing to rapidly 

increasing energy costs and time constraints. As one would expect, the cost of foraging 

goes up with increased time spent foraging (Gabrielsen 1994). A Common Murre 

increases food demand about 8.5% more above resting needs for every hour it spends at 

sea (Gabrielsen 1994). Perhaps more importantly, the amount of time available for 

foraging is limited-- and this appears to be the critical factor limiting chick provisioning 

at low prey densities. For example, peak food demands for adult kittiwakes in Cook Inlet 

extend from about 10 July to 15 August (Chapter 10). In mid-July, there are little more 

than 18 hours of daylight and by mid-August there are less than 16 hours from sunrise to 

sunset. Since kittiwakes feed diurnally, they are constrained by these time windows in 

how often they can feed chicks. 

While chick feeding rates (CFR's) are ultimately limited by daylight, kittiwakes can 

adjust the quality and quantity of food delivered in each meal to chicks. In general, the 

quality (energy density) of meals fed to chicks varied little (mean= 4.7 Wg; C.V.=8.5%) 

because adults apparently went out of their way to feed oily forage fish to chicks at all 

colonies (Chapter 10; Roby et al., unpubl. data). A more important source of variability 

was in the mass of meals delivered (C.V. 3 1.6%). Because they can capture, carry and 

then regurgitate multiple prey to chicks, kittiwakes can vary the size of meal loads 

delivered. It is difficult, however, to assess the true mass of chick meals delivered by 

adults because of uncertainties in the collection of regurgitated samples (e.g., was it full 

or partial meal because regurgitation was incomplete, or because adult partially fed chick 

before capture?). These data need further detailed analysis. What we can say for now is 

that the largest meal delivered by an individual was 62 g, and that average meals in years 
with good food supplies were about 30 g (Chapter lo), which if comprised all of sand 

lance (400 mm), would be about 150 Wlmeal. 

As predicted (Chapter I), kittiwakes exhibited a sigrnoidal response in chick feeding rate 

(CFR) to prey density (Fig. 14.5), and the asymptotic rate of chick meal delivery 

estimated by logistic regression was 0.21 mealslnesthr (k0.02, p<0.001). This means that 

over a range of moderate to high prey densities, and with foraging trips of about 3.3 hr 

(200 min, Fig. 14.5), average adults delivered 3.8 meals per 18-hr day. Baird (1994) 

reported the same feeding rate for kittiwakes in the Gulf of Alaska (mean 3.8; range 2.4- 

6.5 mealsld). If 'good' meals containing 150 Wlmeal were delivered, then nests received 

570 kJ/d, i.e., enough to sustain growth of about 1.35 chicks (which was, in fact, the 

asymptotic brood size at fledging, Fig. 14.5). 

Below threshold levels of prey abundance (estimated by regression at 0.0135 g/m3, 

p<0.001), CFR's declined rapidly to as little as 2.0 mealsld (0.11 meals/nest/hr/l8h). Note 

that we have relatively few measures of CFR below threshold prey density because 

kittiwake chicks failed to survive and we could not measure behavioral parameters in 

those cases. CFR was correlated (r2=0.40, p=0.037) with foraging trip duration and we 

can calculate from regression (CFR= -0.0076"FTD + 5.34) that in order to deliver 3.0 

mealsld, FTD's must not exceed 308 midtrip in an 18 hr day; or 257 midtrip during late 

chick-rearing (16 hr day). Even then, those 3 meals would need to weigh about 30 g (150 

k.) each to achieve maximal growth rates of one chick. 

Thus, 5 hr (300 min) is the approximate critical FTD above which kittiwakes begin to 

have problems maintaining one chick in lower Cook Inlet, and it corresponds to a 

maximum CFR of about 3 mealsfd (0.17 meals/nesthrll8h, Fig. 14.5). Adults would be 

hard-pressed to deliver enough food for chicks in 2 mealdd, and so it is not surprising 

that 3 mealdd is a critical level of effort required. Suryan et al. (2000a) reached the same 

conclusion for kittiwakes in Prince William Sound: "it appears that an average distance 

over 45 km and duration > 5 hrs is approaching the limit that adults can maintain while 

successfully provisioning young". Similarly, Hamer et al. (1993) concluded that foraging 

trips of 2-3 hrs recorded at various colonies in northeast England and at Sumburgh Head 

in 1991 represented "the norm for kittiwakes rearing chicks in conditions of good food 

supply" whereas an FTD of 6.2 h observed at Sumburgh Head (about same latitude as 

Cook Inlet) in 1990 led to complete breeding failure in kittiwakes. The critical FTD (5 

hr) and CFR (3 mealsld) values observed in our study would, of course, be different at 

higher latitudes where kittiwakes have much longer day-lengths in which to forage (e.g., 

Svalbard, Gabrielson 1994). 

In contrast to kittiwakes and against predictions (Chapter I), murre CFR's were not a 

sigmoidal function of prey density- possibly because foraging effort at low prey 

density was buffered by re-allocation of discretionary time (see below). For murres, CFR 

declined slightly and linearly with decreasing prey density (Fig. 14.4). Because the peak 

of murre chick-rearing in Cook Inlet occurs between about 10-30 August, daylight hours 

available for foraging ranged from 14- 16 hr during chick-rearing. Thus, the average CFR 
of 0.26 mealslnestlhr translates into an average daily delivery rate of about 4.1 mealsld 

(range 3.0-5.3) in a 16-hr day. 

Since murres deliver only one fish at a time to chicks, the issue of meal size is less 

complicated than for kittiwakes. However, murres did select energy-rich fish (mostly 

osmerids, sand lance, herring; Chapter 9) and delivered larger fish (often >I00 mm) than 

they ate themselves (generally 400 mm). It was very difficult (and disturbing to birds) to 

collect fish delivered by adults, so we have very limited data on fish size other than visual 

estimates of size compared to bill length (e.g., Uttley et al. 1994). For now, we estimate 

that the mean size of fish delivered was about 6.4 g, and therefore murres were fed an 

average of about 26 g/d (range 19-34). Even if we assume that chicks were fed fish with 

higher energy content (e.g., 5.7 kJ1g for sand lance >I00 mm; Anthony et al. 2000), we 

can calculate that chicks received only 148 kJId, which is less than the average required 

intake estimated from metabolic study (200 kJ/d, Gabrielsen 1994) and much less than 

estimated from other field studies (Barrett et al. 1997). However, higher estimates of 

energy delivery rates are often the result of higher-- and perhaps faulty (van Pelt et al. 

1997)-- estimates of fish energy density rather than higher rates of meal delivery. In any 

case, our data and these issues need fbrther consideration before reaching any final 

conclusions. 

One certainty, however, is that our observed rates of meal delivery and resulting mass of 

fledgling chicks are within normal ranges observed in other studies. For example, in a 10- 

yr study of food consumption by Common Murre chicks at the Isle of May, Scotland 

(56.2' N), the average daily feeding frequency was 4.1 (f 0.2 s.e.) mealsld (Harris and 

Wanless 1995). As in Cook Inlet, meals were comprised mostly of energy-rich species 

(sand lance Ammodytes marinus, herring Clupea harengus, sprat Sprattus sprattus). The 

10-yr average daily food delivery during chick-rearing was estimated at 30 (k2 s.e.) g/d. 

The difference in daily food delivery between this study and ours (30 vs 26 g/d, 

respectively) is entirely due to the difference in estimate of average fish mass delivered 

(7.7g vs. 6.4 g, respectively). The difference may be real, however, since the mass of 

chicks at fledging age was also higher at the Isle of May (263 f 3.8g) than in Cook Inlet 

(227 f 6.5 g). 

Similar murre CFR's have been observed elsewhere. Burger and Piatt (1990) reported an 

average CFR of 4.3 rnealsld (range 3.7-4.9) during 4 years of study at Witless Bay, 

Newfoundland. In that study, total food intake averaged 57 gld (range 45-66) owing to 

the much larger size of fish delivered (mean=13.3 g). Uttley et al. (1994) reported CFR's 

of 3.0 rnealsld in a 'bad' food year at Sumburgh Head and 6.2 mealsld in a 'good' food 

year. Watanuki et al. (1992) estimated a CFR of 3.7 mealsld (19.5 hr day) for murres at 

Bluff. At the Gannett Islands, murre CFR's were 4.9 and 3.7 rnealsld in 1982 and 1983, 

with corresponding chick departure weights of 23 1 and 246 g, respectively. 

Adult attendance and discretionary time 

Differences in size and quality of meals notwithstanding, self-respecting murre and 

kittiwake parents everywhere try to deliver about 4 rnealsld to chicks. Murres forage only 

during the day and one adult of the pair almost always attends the nest-site to incubate the 
egg or guard the chick against predators (Cairns et al. 1987, Burger and Piatt 1990). 

Therefore a total of 14- 16 h are available each day for off-duty murres to forage or 

engage in other activities. For murres under moderate to good food conditions, where 

foraging trips usually require a minimum of 2 h (above), this means that at least 8 hld is 

invested in foraging; leaving 6-8 h for other activities. About 2-4 h of each day, adults are 

absent from nest sites, but not foraging for chicks (FTD's and CFR's calculated only from 

absences resulting in a meal delivery). We assume that during these absences, adults 

engage in self-maintenance activities, socialize or obtain meals for themselves (Cairns et 

al. 1987, Uttley et al. 1994). For the remaining hours of each day (ca. 4 h during 

incubation, 2.5 h during chick-rearing) off-duty murres can be found "loafing" at the nest 

site, using this "discretionary" time to attend the site with its mate (Fig. 14.4). 

This overlap in time among mates attending the nest-site offers a time buffer that can be 

re-directed towards foraging when food supplies are scarce (Burger and Piatt 1990, 

Monaghan et al. 1994, Uttley et al. 1994, Zador and Piatt 1999). Discretionary coattendance time has varied from about 2.4% to 40% of daylight hours among studies to 

date (Zador and Piatt 1999). Our study indicates that the relationship between 

discretionary time and food density is sigmoidal (Fig. 14.4, Table 14.1). During moderate 

to good food conditions in Cook Inlet, regression analysis suggested (p<0.001) 

asymptotic attendance at 76 bird-minh during incubation and 71 bird-mink during 

chick-rearing (Fig. 14.4). This corresponds to co-attendance of adults during 27% of 

daylight hours during incubation, and 18% of daylight hours during chick-rearing. Below 

threshold food densities (0.013 g/m3, p<0.001), murres rapidly used up all their 

discretionary time on foraging trips of exponentially increasing duration (Fig. 14.4). It 

appears that discretionary time buffers were depleted during chick-rearing when foraging 

trips exceeded about 170 min. 

As for murres, kittiwakes forage during the day and one adult of the pair usually attends 

the nest-site to incubate the egg or guard the chick against predators (Baird 1994). In 

contrast to murres, adult kittiwakes appear to have little or no discretionary time at high 

food densities that can be re-allocated to foraging when food is scarce (Fig. 14.5). During 

chick-rearing, some 16-18 h are available each day for activities of the off-duty adult. 

Under good food conditions, chick foraging trips usually required 3.3 h (above), meaning 

that at least 13 hld were devoted to foraging trips that resulted in a chick meal; leaving at 

most 3-6 h for other activities. As in murres (above), adult kittiwakes may spend 2-4 h 

absent from nest sites for self-feeding or maintenance-- leaving just a little time for 

"loafing" at the nest-site. When foraging trips were more than 4 or 5 h-- often the case in 

Cook Inlet (Fig. 14.3)-- kittiwakes had no discretionary time at all. Indeed, adults were 

forced to abandon the chick altogether, leaving it vulnerable to predation (Fig. 14.5). 

Roberts and Hatch (1993) noted similar behavior of kittiwakes at a food-deprived colony 

on Middleton Island. Adults co-attended nests less than 1% of the time, and rarely left 

nests unattended altogether during incubation and early chick-rearing; less than 10% of 

the time overall. The duration of foraging trips initiated when one adult remained on the 

nest (mean 3.8 h) versus when no adult remained on the nest (mean 1.7 h) strongly 

suggests that adult kittiwakes "strive to maintain continuous attendance with their chicks" 
even in the face of serious food shortages (Roberts and Hatch 1993). Similarly, at 

Sumburgh Head (Hamer et al. 1993), nests were almost never left unattended in 199 1 

(good food year, productivity 0.98 chickslnest) whereas they were left unattended on 

17% of observations during chick-rearing in 1990 (bad food year, productivity 0.0 

chickslnest). 

Biological Parameters 

In contrast to behavioral parameters (above)-- which all relate to the acquisition of 

energy-- the biological parameters that we studied all relate to the disposition of food 

energy obtained from foraging. In other words, physiological condition (chick growth, 

adult body condition) and reproductive output (laying, hatching and fledging success; 

clutch and brood size) exhibit a range of values that, for the most part, simply reflect how 

much food has been acquired. For this reason, relationships between biological 

parameters and food supply are straightforward: As long as some adequate (threshold) 

amount of food/energy is obtained, then metabolic demands for maintenance and growth 

are met, and reproduction is not limited by food. This has recently been demonstrated in a 

variety of experimental situations in the laboratory (Kitaysky et al. 1999,2001; Romano 

2000) and field (Jacobsen et al. 1995, Erikstad et al. 1997, Golet et al. 1998, Golet and 

Irons 1999, Gill 1999, Kitaysky et al. 1998, Kitaysky 1999, Harding et al. 2001). 

However, the exact form of relationships between biological parameters and food supply 

in the wild has never been demonstrated. Further, we want to know how, or if, murres 

and kittiwakes can adjust their physiology or biology to compensate for low rates of food 

acquisition. 

Chick growth rates 

We observed few extreme low growth rates for kittiwake chicks in this study (Fig. 14.5). 

As food became scarce, adults abandoned nest-sites for extended periods (Fig. 14.5) and 

chicks were eaten by predators or fell out of their nests (as observed elsewhere; Hamer 

1993, Roberts and Hatch 1993). Thus, starving or emaciated chicks quickly disappeared 

fkom samples, leaving us with no chicks to measure or only chicks with successful 

parents-- a bias also encountered in penguin studies (Williams and Croxall 1990). This 

was particularly true for beta chicks, which are often expelled by alpha chicks during 

early chick-rearing if food is scarce (Roberts and Hatch 1993). Consequently, we found 

no relationship between beta chick growth and food supply (Table 14.1). 

With special efforts, we obtained repeated measures of some poorly-fed alpha/singleton 

chicks on Chisik Island in 1996 (1 1.1 g/d) and 1997 (14.4 g/d), allowing us to 

demonstrate a sigrnoidal relationship between alpha/singleton chick growth rate and food 

supply (Fig. 14.5). Outside the extreme low values from Chisik Island, however, average 

aZpha/singleton growth rates in all colony-years ranged between 14.5 and 19.8 g/d. Even 

when we include the extreme data, growth rates were not too variable (CV only 12.6%). 

The asymptotic rate of growth was 16.8 4~0.04 (s.e.) g/d (p< 0.001). Rates of kittiwake 

chick growth below the inflection point observed in this study (ca. 14g/d, Fig. 14.5) are 

unusual in Alaska (Murphy et al. 1991, Baird 1994, Suryan et al. 2000b) and at colonies 

in the Atlantic (Barrett and Runde 1980, Galbraith 1983, Barrett 1996)- suggesting that 
bias in sampling kittiwake chicks for growth measurements is a problem everywhere. 

Growth rates of less than 14 g/d were recorded for both alpha and beta chicks at the 

Middleton Tower colony, but only because predation was eliminated by the experimental 

set-up there (Gill 1999). 

After initial attempts, we abandoned efforts to measure absolute murre chick growth rates 

because of the disturbance caused by us when capturing chicks in murre nesting areas. In 

many years we were able to capture murre chicks after they had fledged from nest-sites 

(either by capturing them on beaches as they made their way to the water, or on the water 

using small boats and dip-nets). However, murre chicks may fledge at a younger age in 

years of good food supply (Table 14.1; Uttley et al. 1994). By dividing chick body mass 

by wing length, it is possible to obtain an index of growth (i.e., body condition at 

fledging, Fig. 14.4) that is independent of age in larger chicks. 

As for kittiwake chicks, the relationship between murre chick growth and food supply 

was sigmoidal, with an asymptotic (p<0.001) body condition index at 3.18 50.029 s.e. 

g/mm. Asymptotic indices were associated with absolute masses >209 g. The overall 

average chick body mass at fledging was 229 g (range of annual means 199-253 g). 

Chick body condition indices less than 3.0 were observed at Chisik only in 1998 (mass 

199 g) and 1999 (mass 206 g); the colony-years of lowest food supply observed in this 

study. Over all colony-years (n=10) for which we have data, murre fledgling body 

condition was remarkably consistent (CV only 4.2%). 

Based on fledgling masses and chick fledging age from study plots (average 20.2 d), we 

can estimate growth rates of about 9.7 to 13.2 g/d for murre chicks. Because growth 

continues throughout the 19-21 days in the nest (Gaston 1985), these rates are not much 

different than "maximum growth rates" of 8.6 to 15.7 g/d reported historically (Gaston 

1985) for common murres. At the Isle of May, where murres appeared to be unlimited by 

food supply, Harris and Wanless (1995) reported a mean weight of chicks at day 21 

(modal fledging age) of 263 k3.8 g, and annual mean mass of 'large' chicks (immediately 

pre-fledging) ranged from 245 to 265 g (Harris and Wanless 1988). Mass of 'large' 

chicks (wing lengths > 60mm) at the Gannett Islands, Labrador, ranged from 23 1-246 g 

in the 1980's (Birkhead and Nettleship 1987) and from 223-233 g in the 1990's (Bryant et 

al. 1 999). Lower growth rates (7-8 g/d) and similar final fledging masses (230-270 g) 

were observed for common and thick-billed murre chicks on Hornerya, Norway (Barrett 

et al. 1997). At Sumburgh Head, the mass of 'large' (wing length = 60 mm) chicks 

estimated from regression would be 256 g in the 'good' food year, and 212 g in the 'bad' 

food year (Uttley et al. 1994). 

As for kittiwakes, there are few examples of extreme low growth rates in common 

murres. In contrast to the situation with kittiwakes, however, predation of unattended 

chicks is not a source of bias in assessing murre chick growth. Apparently, murres in 

Cook Inlet (and at Sumburgh Head, Uttley et al. 1994) maintained high chick growth 

rates in the face of declining food supplies by re-allocating discretionary time to foraging 

for chick meals. Only in the most extreme conditions (1998199 at Chisik) did murre 

chicks appear to suffer from food deprivation. Similarly, common murre chick fledglings 
weighed only 204 g at Middleton Island (Hatch 1983), a site of persistent kittiwake 

breeding failure and presumably very poor food supplies (Gill 1999). The only other 

location where fledgling body masses of less than 210 g have been reported is at Vednry, 

Norway (165 g, Rarv et al. 1984; as reported in Harris and Wanless 1988). This was 

associated with an extreme case of long-term breeding failure of murre and puffin 

populations owing to a collapse of local herring stocks during the late 1970's (AnkerNilssen 1997). Thus, it appears that extreme low growth rates in common murres are 

rarely observed in the wild because murres can buffer against declining food supplies 

over a wide range of conditions. 

In summary, growth in both murre and kittiwake chicks is related to food density in a 

positive, sigmoidal fashion. This was predictable (Table 1.1). As long as chicks acquire 

adequate rations of food, they can grow at asymptotic rates. Excess rations are not 

assimilated by chicks (Romano 2000), and so growth rates are independent of food 

supply above the threshold (Fig. 14.5). Chick growth rates below threshold values 

indicate difficulty in acquiring food. However, low chick growth rate data are rarely 

recorded at kittiwake colonies where predation is common, nor at common murre 

colonies because adults can buffer chick feeding rates against moderate declines in food 

supply. 

These results for kittiwakes and common murres stand in contrast to other seabird species 

for which reduced chick growth rates are commonly observed. For example, thick-billed 

murres-- which live mostly in Arctic habitats and face more extreme feeding conditions 

than common murres-- exhibit at least 2-fold geographic and temporal variability in 

fledgling mass (range 121-250 g; mean 181 k39.4 g; CV=22%; Gaston 1985). Similarly, 

tufted puffins-- whose young are protected in burrows from predators-- exhibit 3-fold 

variability in chick growth rates (range 6.8-21.4 gld; mean 15.2 *4.5 gld; CV=21%; Piatt 

et al. 1997). 

Adult body condition 

We found no relationship between adult body condition and food density for either 

murres or kittiwakes. This was true whether we used body condition data from stress 

studies (circles, Figs. 14.4, 14.5) or from collections for diet studies (squares, Figs. 14.4, 

14.5) or combined data (Table 14.1, Figs. 14.4 and 14.5). Furthermore, variability in 

adult body condition was extremely low for both kittiwakes (CV = 7.5%) and murres 

(CV = 3.8%). 

These results were not expected. We predicted a positive, non-linear relationship between 

adult body condition and food supply (Table 1.1) and it was reasonable to assume that 

body condition would be sensitive to variations in food supply (Monaghan et al. 1989, 

Hamer et al. 1991). Indeed, a variety of experimental studies-- where adult foraging effort 

is manipulated by increasing or decreasing clutch size of nesting seabirds-- have shown 

that adult body condition can be affected negatively by increasing workload (Johnsen et 

al. 1994, Jacobsen et al. 1995, Golet and Irons 1999). 
Field studies of seabirds subjected to natural variation in food supply, however, rarely 

reveal any large effects on adult body condition. Indeed, for those single-colony studies 

where seasonal variability has been accounted for in sampling, variability in adult body 

condition among years was exceedingly low for great skuas Catharacta skua (CV = 

0.9%, n=4 yr, Hamer et al. 1991), Arctic terns Sternaparadisaea (CV = 6.6%, n=4 yr, 

Suddaby and Ratcliffe 1997), yellow-nosed albatross Diomedea chlororhynchos (CV = 

4.0%, n=4 yr, Weimerskirch et al. 2001), thick-billed murres (CV = 1.1%, n=5 yr, Bryant 

et al. 1999), common murres (CV = 0.6%, n=5 yr, Harris and Wanless 1988) and blacklegged kittiwakes (CV = 4.8%, n=8 yr, Williams et al. 1998). In the case of the skuas, 

thick-billed murres and common murres, variability in body condition was so low as to 

baffle investigators, given that other measures indicated some marked changes in food 

supply had occurred. In the case of the terns, albatross and in a two year study of 

kittwakes (Hamer et al. 1993), annual variation in adult body condition was often driven 

by one exceptional year, and otherwise body condition was not well correlated with food 

supply or indirect measures of food availability. 

Taken together with our results, this suggests that body condition is strongly buffered 

against fluctuations in prey abundance. The reason for this seems clear: Survival of adults 

during the subsequent winter is correlated with adult body condition at the end of the 

breeding season (Jacobsen et al. 1995, Hamer et al. 1991, Golet et al. 1998) and adults 

should therefore be conservative in maintaining their own body condition. This behavior 

is to be expected in long-lived species which have the opportunity to breed over multiple 

years, and supports the basic prediction of life-history theory that parents should balance 

investment in their offspring against their own chance to reproduce in the future (Steams 

1992). Most breeding seabirds appear to maintain a safety margin above some threshold 

body mass at which they abandon breeding attempts altogether (Weimerskirch et al. 

2001). We observed murres and kittiwakes near their limits in foraging ability, and near 

(murre) to total (kittiwake) failures in their ability to fledge chicks, but we never 

observed total abandonment of breeding effort. Collecting data on body condition of 

birds at or below thresholds of body condition may be difficult or impossible since these 

individuals would probably not remain at a colony to be captured. 

Clutch size and laying success 

Black-legged kittiwakes can lay up to three eggs whereas murres can lay only one egg. 

Kittiwakes build well-developed nests and it is relatively easy to assess what proportion 

of the population actually lay eggs after building nests (= laying success). In contrast, 

murres build no nest, and it is difficult to assess which birds attending crowded nesting 

areas are potential breeders. Thus, we have good data on variation in clutch size and 

laying success in kittiwakes, but none for murres. 

Clutch size and laying success in kittiwakes were independent of food supply (Fig. 14.5, 

Table 14.1). On average, 69% of pairs that attempted to breed eventually laid eggs. For 

those that laid, the average clutch size was 1.49 40.18 s.d. eggslnest. Laying success (CV 

= 28.7%) was more variable than clutch size (CV = 12.3%). There are at least two 

explanations for the lack of correspondence between these biological parameters and 

food supply. First, there was a gap in time between measurements: clutch size and laying 
success were measured in June while food supply was measured in late July - early 

August. We have no a priori reason to expect food supply (and secondarily kittiwake 

egg-production) in June to correlate with food supply in August, although we have weak 

evidence that this may be true. For example, the seine catch per effort of adult sand lance 

in Kachemak Bay tended (8=0.5 1, ns) to be high in August if it was high in June. 

Alternatively, kittiwakes may have a programmed approach to egg-laying that is largely 

independent of food supply except under extreme conditions, i.e., when food supplies and 

nutrient reserves are so low as to preclude egg formation. Indeed, evidence from a variety 

of seabirds suggests that clutch size is maximized and that regulation of breeding effort 

occurs later by brood reduction or nest desertion (Sydeman et al. 1991, Monaghan et al. 

1992, Hamer et al. 1993, Philips et al. 1996, Suddaby and Ratcliffe 1997). This may 

explain why, despite high variability in overall productivity among areas, kittiwake 

clutch size and laying success in Cook Inlet were similar to those observed during the 

same years (1995-1999) at several colonies in Prince William Sound (Suryan et al. 

2000b; n= 15 colony-years, laying success = 78% [CV = 24.3%], mean clutch size = 1.66 

*0.19 s.d. eggslnest [CV = 1 1.7%]); and throughout the Gulf of Alaska (Hatch 1990; n= 

77 colony-years, laying success = 65% [CV = 33.7%]; for n = 91 colony-years, clutch 

size = 1.49 * 0.23 s.d. [CV = 17.4%]). 

Hatching, fledging and breeding success 

Once the egg(s) have been laid, murres and kittiwakes are committed to a breeding effort. 

Incubation and guarding of the egg or chick is essential for survival of the offspring, and 

requires the presence of at least one adult. Not surprisingly, nest-attendance by at least 

one adult is among the least variable parameters for both murres (CV=O%) and kittiwakes 

(CV=7%) (Table 14.1). As predicted, hatching success and then fledging success in 

kittwakes were correlated with food supply (?=0.53 and 0.89, respectively) in a 

sigrnoidal fashion (Fig. 14.5). Fledging success had the strongest relationship, 

presumably because is it was measured closer to the time period in which prey were 

sampled. 

Despite the weak correlation between food supply and earlier events (laying, hatching), 

overall breeding success in kittiwakes was-- as predicted-- strongly correlated with food 

supply in sigmoidal fashion (Fig. 14.5, Table 14.1). Above the threshold prey density of 

0.015 g/m3, the upper asymptotic chick production was 0.46 chickslpair. Below the 

threshold, the lower asymptotic chick production was 0.0 15 chickslpair. Similarly, the 

best model to explain brood size at fledging was sigmoidal (Fig. 14.5), and suggests that 

as long as food supplies remained above threshold, kittiwakes could fledge 1.3 

chickslpair on average. 

Contrary to predictions (Table 1. I), neither hatching, fledging nor breeding success in 

common murres was correlated with food supply (Fig. 14.4). Murres appeared to have 

trouble in only 2 years. In 1998 at Chisik Island and in 1999 at Gull Island, murres 

arrived at colonies with relatively high levels of corticosteroid stress hormones in their 

blood plasma (Kitaysky et al., in prep.) which suggests that they were stressed by lack of 

food even before they began to breed (Piatt et al. 1999, Kitaysky et al. 1999,2000). On 
these two occasions, murres exhibited (Fig. 14.4) much lower than usual hatching success 

(52% vs. 70-go%), fledging success (<45% vs 64-92%), and consequently low overall 

breeding success (<30% vs. 53-8 1 %). 

In other years, murres were apparently not limited by food during laying or hatching. 

Murres were able to compensate for extremely low food abundance during both 

incubation and chick-rearing by increasing the amount of discretionary time devoted to 

foraging (Fig. 14.4, see above "Behavioral Parameters"). In effect, murres were able to 

buffer their breeding success against a wide range of variation in prey abundance by 

foraging longer and farther from colonies during lean food years (Burger and Piatt 1990, 

Zador and Piatt 1999). In fact, it appears (Chapter 8) that some murres foraged beyond 

the 45 km zone around each colony that we surveyed to assess prey abundance, and this 

may have confounded our attempt to correlate breeding success with "local" food supply. 

In any case (Table 14. I), murre fledging success (CV = 28%) and breeding success (CV 

= 29%) were about 3 times less variable than kittiwake fledging success (CV = 8 1%) and 

breeding success (CV = 87%) because murres were able to behaviorally compensate for 

low food densities. 

Obviously, murre breeding success cannot be completely independent of food supply. We 

may have failed to demonstrate a functional breeding response to variable food supply 

because the spatial scale of our sampling was too small, and because within the spatial 

range that murres operate, food supplies were simply never so low as to cause complete 

breeding failure. Functional response curves (above) for aggregation, foraging trip 

duration, and discretionary attendance all clearly indicate that murres-- like kittiwakes-- 

have a foraging threshold at about 0.01 3 g/m3 of fish biomass. The difference between 

murres and kittiwakes is that under the same environmental circumstances, murres can 

exploit nearly 100 times more habitat than kittiwakes at the same distance from colonies, 

they can search nearly twice as much surface area than kittiwakes in the same time, and 

they have more time to forage (see "Foraging trip duration", above). 

Consequently, while we frequently observed kittiwake breeding failures in Cook Inlet, 

we never observed total breeding failure in murres. Presumably, prey abundance was 

never so low throughout the entire study area that murres could not compensate to some 

degree. Perhaps if we could collect more data on murres during extremely poor food 

years (in the lower 10% of what we observed in our study), and at larger spatial scales, 

we could better resolve breeding response curves. With the data we have, however, we 

can assume that the breeding response of murres is sigmoidal (or a step-function) with a 

very low threshold for breeding failure. At the least, we can say that in the absence of 

disturbance (by humans, predation), breeding success of less than 0.4 chickslpair in 

murres indicates limitation by food supply. 

Our results are consistent with other studies. At Sumburgh Head, both murres (Uttley et 

al. 1994) and kittiwakes (Hamer et al. 1993) were examined simultaneously during a 

'good' food year (1 99 1) and a 'poor' food year (1 990) that, by many measures, were 

similar to our best years at Gull Island and our worst years at Chisik Island, respectively. 

Murres exhibited high hatching success (76%, 72%) and fledging success (78%, 98%) in 
1990 and 1991, respectively, and there was no significant difference in overall breeding 

success among years (59%, 70%; respectively). While kittiwakes showed little difference 

in hatching success (81 %, 80%) between years, fledging success (0%, 85%) and overall 

breeding success (0%, 68%) were extremely different in 1990 and 199 1, respectively. 

No other simultaneous studies of murres, kittiwakes and food supply have been 

conducted. However, we can examine variability in breeding success of murres and 

kittiwakes from long-term (1 975- 1999) data collected throughout Alaska (Gulf of Alaska, 

Aleutians, Bering and Chukchi Seas) in a variety of monitoring and research programs 

(Hatch 1993, Dragoo et al. 2000). From these data (Fig. 14.6, Table 14.2), which include 

an extreme-- but natural-- range of environmental conditions for breeding (see Hatch 

1993), we find that common murres (n=14 colonies, n=99 colony-years) have rarely had 

complete breeding failure (0 chickslpair on only 4% of occasions), and on only 26% of 

occasions was breeding success indicative of limiting food supply (i.e., below 0.40 

chickslpair; see above). Remarkably, common murres were successful (>0.40 chickslpair) 

about three-quarters of the time (Fig. 14.6) and variability in breeding success was quite 

low (CV = 40%) and similar to that observed in Cook Inlet (CV = 28%). In contrast, 

kittiwakes (n=17 colonies, n=235 colony-years) had complete failures (0 chickslpair) 

18% percent of the time, and showed signs of food limitation (breeding success < 0.46 

chickslpair; above) 77% of the time. On only 23% of occasions did kittiwakes appear to 

be un-restricted by food supply. Kittiwakes showed high levels of variability in breeding 

success in Cook Inlet (CV = 87%) and Alaska (CV = 1 10%). 

A similar contrast in murre and kittiwake breeding success has been noted elsewhere 

(Table 14.2). Common murres observed during 54 colony-years at a variety of colonies in 

the North Atlantic (Birkhead 1976, Hedgren 1980, Birkhead and Nettleship 1987, Harris 

and Wanless 1988, unpubl. data; Burger and Piatt 1990, Bryant et al. 1999; J. Piatt, 

unpubl. data) averaged 0.75 * 0.09 s.d. chickslpair. Despite the span of years (1963- 

2001) and colonies (n=l I), variability in breeding success was low (CV = 12%), with 

only one occasion where breeding success was less than 0.4 chickslpair (0.26 chickslpair, 

remaining values ranged from 0.52-0.88 chickslpair). At the Isle of May, murres have 

never failed in 21 years of study (range 0.63 to 0.81 chickslpair; Harris and Wanless, 

unpubl. data). Likewise, in 29 years of study at the Farallon Islands, California, common 

murres failed (<0.4 chickslpair) only 3 times, all in association with strong ENS0 events 

(Sydeman 200 1, PRBO unpubl. data). Otherwise, breeding success ranged between 0.6 1 

and 0.9 1 chickslpair. 

Kittiwake breeding success measured in the Atlantic during 143 colony-years (42 

colonies, 1973-200 1 ; Birkhead and Nettleship 1988, Harris and Wanless 1990, and 

unpubl. data; Hamer et al. 1993, Erikstad et al. 1995, Barrett 1996, and unpubl. data; 

Anker-Nilssen et al. 1997) averaged 0.77 *0.39 chickslpair and variability (CV = 53%) 

was more than 4 times greater than that observed in Atlantic murres (12%, Table 14.2). 

Indeed, it appears that under a wide range of conditions, kittiwake productivity is always 

more variable than murre productivity (Fig. 14.7). Furthermore, for both species, 

variability is high when productivity (and presumably food density) is low. This suggests 

that in "good times", high density prey aggregations are accessible by most colonies but 
in "bad times", prey aggregations are not just less abundant everywhere, they are patchy 

and accessible to only a few colonies. 

Variability of seabird parameters in relation to food 

Another informative way to look at the data collected over 15 colony-years in lower 

Cook Inlet is to examine variability in the different seabird parameters that we measured. 

For this purpose I calculated the ratio of maximum to minimum parameter values ("dm 

Ratio") and coefficients of variation (CV's) for each parameter. In general, both measures 

of variability yielded similar results (Table 14.1) and parameters fell into categories of 

"low" (CV<20%), "medium" (20<CV<40%), and "high" (CV>40%) variability. It was 

not always possible to measure every parameter in all years, and so sample sizes are less 

than 15 in many cases, but usually more than 10 (Table 14.1). We always had some data 

from the "best" colony (Gull Island) and "worst" colony (Chisik Island), and so the 

calculated CV's should capture the range of natural variability in most cases. 

The CV in forage fish biomass (as measured hydroacoustically) among all years and 

colonies was 80%. This corresponded to about a 20-fold difference in mean forage fish 

abundance between low and high extremes. If fluctuations in prey abundance have a 

strong influence on any foraging or breeding parameters, then variability in those 

parameters should be similar to variability in prey abundance. On the other hand, if 

seabirds are able to buffer against fluctuations in prey abundance, then we expect 

variability in some seabird parameters to be less than the variability observed in food 

supply. Finally, by ranking the seabird parameters from most variable to least variable 

for murres and kittiwakes we can highlight (Fig. 14.8) some similarities and differences 

in the way each species responds to variability in prey abundance: 

Similarities among species: 

1) Variability in density of adults at sea was of similar magnitude (>70%) to variability in 

forage fish biomass (80%). 

2) Adults minimized variability in time spent guarding the egg or chick at the nest site. 

3) Adult birds minimized variability in their own body condition. 

4) Variability in parameters relating to chick development (condition index, growth rate, 

age of fledging) was low to moderate. 

5) Variability in food acquisition parameters (trip duration, chick feeding rate) was 

moderate. 

6) Variability in early breeding parameters was lower than later breeding parameters 

(clutch size < laying success < hatching success < fledging success). 

Differences among species: 

1) Fledging and overall breeding success in kittiwakes was of similar magnitude to 

variability in forage fish biomass, whereas these parameters were only moderately 

variable in murres. 

2) Discretionary time (available for re-direction to foraging effort) during incubation and 

chick-rearing was highly variable in murres. Kittiwakes had no discretionary time 

in most years. 
Response of seabirds to prey: Summary and conclusions 

We had two main objectives in this study. First, we wanted to establish the form and 

strength of seabird responses to changes in prey abundance. Second, we wanted to assess 

the range of variability in those responses. 

Form of response 

We predicted that-- as in other vertebrates (Holling 1965, Murdoch and Oaten 1975, 

Piatt 1990)-- murres and kittiwakes would likely exhibit non-linear foraging relationships 

with food supply. The aggregative response of murres and kittiwakes was, in fact, 

sigrnoidal and bird density at sea was strongly correlated with prey density around each 

colony (Table 14.1). In recent years, breeding success in several seabird species has been 

shown to be a curvilinear hnction of food density (Arctic skua, Philips et al. 1996; 

Atlantic puffin, Anker-Nilssen et al. 1997; Arctic tern, Suddaby and Ratcliffe 1997), and 

we demonstrated a similar relationship for black-legged kittiwakes. Common murres did 

not exhibit such a relationship because breeding success was buffered by increased 

foraging effort in the face of declining food supply. In accord with Cairns' (1987) 

predictions, however, we demonstrated for the first time that other parameters such as 

discretionary ("loafing") time, foraging trip duration and chick growth rate in common 

murres also varied in curvilinear fashion with prey density. We also found curvilinear 

relationships between food density and hatching success, fledging success, chick feeding 

rate and brood size in black-legged kittiwakes. 

The non-linearity of hnctional relationships is wide-spread in predator-prey systems 

(Holling 1965, Hassell et al. 1977) and it contributes to the stability of predator and prey 

populations (Steele 1974, Murdoch and Oaten 1975). A more readily apparent 

consequence of the sigrnoidal response is that it introduces "on-off' dynamics into many 

of the seabird parameters we choose to measure. If prey density is above threshold, the 

parameter of study (e.g., fledging success) is high ("on"). Below threshold, it is low 

("off'). Prey densities can vary over quite a wide range, but if they always remain above 

(or below) threshold, then there will be no apparent relationship between predators and 

their food supply (e.g., at a colony of murres that appeared to be unlimited by food 

supply in the 19801s, Harris and Wanless 1988, 1995). In contrast, marked differences in 

predator biology can be observed in only 2 years of study if one happens to observe 

conditions on both sides of a prey threshold (e.g., murres at Sumburgh Head, Monaghan 

et al. 1994, Uttley et al. 1994). Whatever the circumstances, it is imprudent to interpret 

the effects of food supply on seabird biology without knowledge of basic hnctional 

relationships (Furness and Camphuysen 1997). In particular, we must be cautious in 

using seabirds as "monitors of the marine environment" if we do not know the form of 

response for parameters we use to infer change (Cairns 1987). Finally, the effects of nonlinear predator-prey dynamics are likely to "trickle up" through food webs. As a changing 

environment affects prey populations, we ought to expect dramatic non-linear (Steele 

1974) changes in predator populations (e.g., Anderson and Piatt 1999) rather than smooth 

linear transitions in community composition. 

Although multi-species, ecosystem management is a stated goal of fisheries organizations 

(Botsford et al. 1997), management of predatory and forage fish populations in order to 
sustain marine mammals or birds is still largely a conceptual exercise. Estimates of total 

food requirements of colonial seabirds and marine mammals have been available for 

decades (Furness and Tasker 1997), but only recently have there been attempts to include 

forage considerations in fish population assessment models (Stephenson 1997). 

Management of forage fish populations will ultimately require knowledge of the form of 

predator responses to prey density (Steele 1974) and the thresholds of prey density 

needed to support different predator populations (Piatt and Methven 1992, Byrd et al. 

1997, Furness and Tasker 1997). We can now propose, for example, that forage fish 

densities of about 0.015 g/m3 or higher are needed to support healthy murre and kittiwake 

populations in Alaska (and probably elsewhere). In lieu of acoustic survey data, we can 

also suggest approximate minimum CPUE values for beach seine (100 forage fiswset) 

and mid-water trawl (300 forage fishkm trawled) sampling, below which seabirds would 

have trouble breeding. At present, there are no other comparable data published on the 

minimum prey density requirements of marine birds or mammals. 

In addition to hypothesizing curvilinear relationships, Cairns (1987) further suggested 

that different seabird parameters would have differing thresholds to prey density. For 

example, Cairns proposed that as prey density declined, chick growth rate would 

diminish somewhat before any effect on breeding success would be observed. As prey 

densities fell further, breeding success would diminish before effects on adult survival 

were observed. The basic supposition was that birds would sequentially adjust activity 

budgets, loafing time, chick growth, and then breeding success, before prey density fell 

enough to affect their own survival. The main point of Cairn's hypothesis was that 

because different parameters should be sensitive to different thresholds of prey density, 

we can use different seabird parameters as graduated indicators of food abundance over a 

wide range of food supplies. 

Our results do not support this hypothesis. Statistical estimation of thresholds (inflection 

points) in all our sigmoidal response curves (Table 14.1) suggest that thresholds were 

very similar in all but one response(see below), occupying a very narrow (112000) range 

of prey densities (0.008 to 0.01 5 g/m3) within the spectrum observed during 15 colonyyears of acoustic surveys (0.003 to 0.07 g/m3). Why should prey density thresholds for 

aggregation (COMU, BLKI), chick feeding (BLKI), chick growth (COMU, BLKI), 

hatching success (BLKI), fledging success (BLKI), brood size (BLKI), overall breeding 

success (BLKI) and discretionary time (COMU) all be the same? Probably because there 

is only one physical threshold, and that is the fish school density above which seabirds 

can successfblly acquire food energy at a rate that is sufficient to support daily metabolic 

demands (Piatt 1990). As noted earlier, it is the acquisition of energy that sets the pace 

for all subsequent activities that involve the disposition of energy. 

The behavior that results in threshold patch foraging is well described. First, the rate at 

which predators capture prey is a non-linear function of prey density within the patch 

(Holling 1965, Murdoch and Oaten 1975). In low density patches, the physical dispersal 

of prey limits the rate at which predators can capture and consume them. As prey density 

increases, so does the rate of capture. At moderate to high prey patch densities, however, 

capture rate levels off because of a saturation effect: there is a physical limit to how 
quickly predators can capture, handle, consume and digest prey. In seeking to maximize 

daily food intake, most predators and all higher vertebrates will avoid patches with low 

capture rates and actively seek out patches with a higher probability of asymptotic 

capture rates (Goss-Custard 1970, Green 1980, Lima 1983, Piatt 1990). Thus, thresholds 

are set behaviorally by a predator during its' search for food, and it follows that 

subsequent behavior and biology will be calibrated to the same threshold. We might also 

have predicted that murres and kittiwakes would have different foraging thresholds 

owing to differences in body size and total metabolic demand (Piatt 1990, Furness and 

Camphuysen 1997)-- but they did not. It may be that thresholds are determined by massspecific metabolic demands, which are remarkably similar for murres and kittiwakes (see 

above, "Foraging trip duration"). 

With respect to aggregation, discretionary time, chick growth and foraging trip duration, 

murres responded fbnctionally over the same range of prey densities as kittiwakes. It 

appears, however, that murres did buffer fledging and breeding success against low prey 

densities by increasing foraging time budgets. In this one instance, a time-budget buffer 

effectively lowered the threshold for breeding success in murres. We were unable to 

statistically resolve this threshold, however, because we lacked suficient data at extreme 

low densities, and probably also because our study areas were not large enough to include 

all the potential foraging area for murres (see above, "Hatching, fledging and breeding 

success"). In any case, this "time-buffered threshold" is different than the more 

commonly described "patch density threshold" above. In this one case, then, Cairn's 

hypothesis is correct. A failure in murre breeding success would indicate much lower 

food supplies than a failure or decline in any other parameter we measured. 

Variability 

One of the main reasons for initiating this study was to examine natural variability in 

seabird biology within the geographic area affected by the Exxon Valdez oil spill. We are 

interested in two aspects of variability. First, is food supply a major source of variability 

in seabird parameters we measured? Second, which parameters are most sensitive to 

changes in food supply? 

Variability in bird density at sea (CV>70%) reflected variability in prey density 

(CV=80%), and murre and kittiwake dispersion was well-explained by food dispersion (8 

> 0.70, Table 14.1). This suggests that adult murres and kittiwakes track the abundance 

and distribution of prey schools at the spatial scale of measurement (1000's krn2). In turn, 

this tracking sets the baseline variability for all other parameters (Table 14.1) because 

variability in prey acquisition (including foraging trip duration, chick-feeding rate) 

depends on success in tracking the prey, and, in turn, all other parameters (body 

condition, reproductive success) vary with the rate of prey acquisition. 

Murres and kittiwakes had to cope with a 20-fold variation in food density between 

colony-years of study. Both species were able to buffer against fluctuations in food 

supply to different degrees and in different ways. Both species appeared to minimize 

effects of variability on their own body condition first, and then on the condition (growth) 

of chicks. Foraging behaviors (trip duration, frequency) were moderately variable, 
indicating some ability to buffer foraging effort against extreme changes in food supply. 

Some parameters (clutch size, guarding of chick) appeared relatively insensitive to food 

supply, suggesting that if conditions are good enough to initiate breeding that these 

parameters will be maintained at relatively fixed levels. 

Kittiwakes and murres differed most with respect to breeding success. Kittiwake fledging 

and breeding success were strongly correlated with food supply, and slightly more 

variable (CV=81-87%). Murre breeding success was poorly correlated with food, and less 

than half as variable (CV = 29%). However, the background variability in food supply is 

largely captured in murre discretionary time (CV =66%), used by murres to buffer 

breeding success. 

These results are entirely consistent with life-history theory (Steams 1992) which 

predicts that in long-lived animals that reproduce over many years, there is a trade-off 

between investment in the current year's reproductive effort and subsequent adult 

survival. When food is limiting during a breeding season, adults should always take care 

of themselves first-- and if necessary, even abandon their chicks-- because adults can 

always attempt to reproduce again in subsequent years. The importance of maintaining 

adult body condition is very clear, given the strong linkage between body condition and 

survival in seabirds (Erikstad et al. 1998, Golet et al. 1998, Weimerskirch et al. 2001). 

After taking care of themselves, it follows that adults would minimize variation in chick 

growth and condition, which is linked with survival to breeding age (Sagar and Homing 

1998, Weimerskirch et al. 2000). 

It is not clear whether murres and kittiwakes can actively buffer variability in foraging 

trip duration or chick feeding rate. There parameters are moderately variable in both 

murres and kittiwakes, but it may simply be that there is a limited range of possible 

values that these parameters can take. Below a certain level of effort (ca. 2-3 chick 

mealslday), chicks would fail and the reproductive effort would end. Delivery rates above 

4 mealslday are probably unnecessary. Similarly, there is an upper limit to the number of 

hours available for foraging in each day, and this sets a limit on the number of possible 

trips (see above, "Foraging trip duration"). It may be that in other taxa such as the 

procellifonnes-- which forage over many days-- foraging trips can be much more variable 

(e.g., Weimerskirch et al. 2001). 

Finally, variability in kittiwake breeding success is only slightly higher than the 

background variability in food supply. The difference may simply be due to 

measurement error, or it may reflect that fact that other factors such as weather and 

predation can also influence kittiwake breeding success (Barrett and Runde 1980, Hamer 

et al. 1993, Hatch et al. 1994). In any case, kittiwake breeding success appears to be very 

sensitive to fluctuations in food supply. This parameter should therefore prove to be a 

reliable indicator of variability in the marine environment (e.g., Aebischer et al. 1990). 

In contrast, murre breeding success tells us little about food supplies (except under 

extreme circumstances), whereas murre time-budgets are almost as sensitive as kittiwake 

breeding success to prey fluctuations. Given that murres (spp.) are probably the most 

widely monitored seabirds in the Northern Hemisphere (Gaston and Jones 1998), it is 
time to re-evaluate the utility of measuring breeding success in this species. At the very 

least, it is time to add time-budgets to the repertoire of parameters we routinely measure 

at murre colonies (Cairns 1987). 

Can Seabirds Recover from Effects of the EVOS? 

The immediate impact of the Exxon Valdez oil spill included a substantial loss of adult 

common murres (Piatt et al. 1990). Other species to experience population declines or 

reduced productivity following the spill included Black-legged Kittiwakes, Marbled 

Murrelets and Pigeon Guillemots (Spies et al. 1996). Populations of most seabirds had 

still not recovered five years after the spill (Spies et al. 1996). Models suggested that it 

could take decades for murre populations to fully recover to stable age distributions if 

environmental conditions were favorable (Ford et al. 1982, Piatt et al. 1990). However, 

evidence accumulated during the 1990's that environmental conditions were not 

favorable to seabirds in years following the oil spill. A "regime shift" had occurred in the 

Gulf of Alaska (GOA) during the late 19701s, apparently resulting in marked changes in 

seabird diets, and a lowering of reproductive success and population size in some marine 

bird and mammal populations (Piatt and Anderson 1996, Francis et al. 1998). 

This new information raised several questions: To what degree were seabirds affected by 

natural changes in the GOA environment before the spill? Could effects of the spill be 

separated from natural variability? In light of the regime shift, what was the current status 

of seabird populations in the GOA, and, could current conditions limit recovery of 

seabirds from effects of the spill? This study was initiated to answer some of these 

questions for seabirds in lower Cook Inlet, and particularly the Barren Islands, where bird 

populations were hit hardest by the spill (Piatt and Ford 1996). 

Population status of seabirds in Cook Inlet 

Our study was designed to provide contrasting data from a "food-pooryy colony (Chisik), 

where murre and kittiwake populations were known to have been declining at rates of 4- 

9% per annum for the past 30 years (Fig. 14.9), and a "food-rich" colony (Gull) where 

murre and kittiwake populations grew at rates of 9% per annum at some point during the 

past 25 years. Kittiwakes increased rapidly on Gull Island during the 19801s, but 

populations leveled off in the1990's and remained at the same level throughout the course 

of our study. Evidence suggests that this was due entirely to saturation of nesting habitat 

on the island. In the absence of nest-site limitation, we believe that kittiwakes would still 

be increasing at the rate observed prior to the plateau, and at a rate similar to that 

observed for murres (which are not yet limited by nesting habitat). Trends at the Barren 

Islands were unknown prior to the EVOS oil spill, but both murres and kittiwakes 

exhibited modest increasing trends during the past decade (Fig. 14.9). 

Productivity in kittiwakes (Fig. 14.10) parallels population trends. Kittiwakes have failed 

chronically at Chisik for more than 30 years, averaging 0.05 chickslpair during that time, 

and only 0.02 chickslpair during this study (1995-1999). Kittiwakes averaged 0.44 

chickslpair at Gull Island since 1984, and 0.48 chickslpair during this study. This is 

higher average productivity than has been observed at any other colony in Alaska except 
Cape Lisburne, where populations have been increasing for the past 20 years (Dragoo et 

al. 2000). Productivity is more variable at the Barrens, averaging 0.29 chickslpair during 

the past decade, and 0.43 chickslpair during this study (Fig. 14.10). 

In contrast, murre productivity does not correlate with population trends. Despite having 

markedly different population trends at the 3 colonies (Fig. 14.9), breeding success was 

high on Chisik (0.56 chickslpair), Gull (0.54 chickslpair) and the Barren islands (0.72 

chickslpair) during this study (Fig. 14.2). There are no prior historical data for murres 

except from the Barrens in 1989- 1993 (Nysewander et al. 1993, Roseneau et al. 1994, 

Boersma et al. 1995). When included, these data suggest an average productivity of 0.54 

chickslpair at the Barrens during the past 12 years. 

Results from Chisik beg the question: How can murres reproduce successfblly and yet 

experience population declines of 9% per annum? A similar question has been asked 

about murres in the Shetlands, which continued to have high breeding success even as 

numbers at colonies declined in apparent response to a crash in food stocks (Furness and 

Camphuysen 1997). These questions may be addressed by a study on adult seabird 

survival, also funded by the EVOS Trustee Council (Restoration Project 01338). Analysis 

of data collected in 2001 is still under way. Adding results from this study, we can now 

assess population trends, adult survival and productivity for murres and kittiwakes on 

Gull and Chisik islands. From these we can estimate recruitment and immigration if we 

assume that about 40% of juveniles survive to breed (a high-end estimate, Hudson 1985). 

Preliminary results (Piatt 2001) suggest that there are marked differences in population 

parameters of murres on Gull and Chisik islands (Table 14.3). On Chisik, annual adult 

mortality (8.0% pa) may largely account for the population decline (-8.9% pa), leaving a 

0.9% pa decline to be explained by emigration. If 40% of juveniles actually survived to 

breed, then recruitment (1 1% pa) would have to balanced by a much larger rate of 

emigration (12% pa). However, survival of chicks is likely to be much lower if chicks are 

underweight (Hatch 1983, Sagar and Homing 1998)-- as they frequently are at Chisik 

(Fig. 14.2). Furthermore, recruitment at a declining murre colony is likely to be less than 

20% (Hudson 1985) and possibly less than 5% (Hatchwell and Birkhead 199 1). Thus, 

recruitment at Chisik may, in fact, be neglible. With modest emigration, and a fairly high 

adult mortality rate, this would explain how murres can maintain such high breeding 

success and yet experience serious population declines. In contrast, the high rate (9.1% 

pa) of murre population increase at Gull Island can be explained by a low rate (4% pa) of 

adult mortality that is more than offset by high rates of recruitment and immigration 

(Table 14.3). 

Kittiwake population parameters appear more straightforward (Table 14.3). At Chisik, 

recruitment has to be virtually zero because productivity is negligible. Thus, the 

population decline (-4.3% pa) is explained entirely by adult mortality (7% pa), offset 

slightly by immigration. At Gull Island, a much higher adult mortality rate (18% pa) is 

balanced by much higher levels of productivity, recruitment and immigration. The 

differences in survival and productivity between Gull and Chisik seem to support the 
hypothesis that long-lived seabirds trade off the costs of reproduction with adult survival 

(Erikstad et al. 1998, Golet et al. 1998). 

Population parameter indices 

How do we compare the health of seabird populations among the islands in Cook Inlet, or 

among regions in Alaska? We have already seen that for each species, any one parameter 

we choose to examine can provide biased inferences about population status depending 

on whether it is correlated with fluctuations in food supply, linear or non-linear in 

response to changes in prey density, and highly variable or relatively constant in the face 

of environmental change. 

One way to assess and compare the performance of seabirds at colonies in Cook Inlet is 

to examine the deviation of parameter values from average at all three colonies (Fig. 

14.11). For example, the average breeding success of kittiwakes in 15 colony-years (3 

colonies in 1995-1999) of study was 0.3 12 chickdpair. Success of kittiwakes at the 

Barrens was lower than this in 2 years of study, and higher in 3 years. Success was higher 

than average in all 5 years at Gull Island, and much lower than average in all 5 years at 

Chisik. Similarly, we calculated deviations from average in other parameters (e.g., 

attendance, feeding rate, growth rate, fledging success, etc.), standardized the deviations, 

and arbitrarily ranked them from largest to smallest at each colony so that we could 

compare them all together (Fig. 14.1 1). In total, we can compare 266 parameter 

deviations (20 species-parameters by year, colony). 

This provides a holistic assessment of how well seabirds were doing at each colony 

during the years of our study. Analysis reveals (Fig. 14.1 1) that, in respect to all the 

parameters measured, birds at Gull Island do better than average most of the time (mean 

deviation = +0.24), while those at Chisik do poorly most of the time (mean deviation = - 

0.37). At the Barrens, measured parameters were above average slightly more often than 

they were below average (mean deviation = +0.09). 

Judging from the range of parameter values we observed at Chisik and Gull islands, and 

in comparing these with values obtained in studies conducted elsewhere under a wide 

range of conditions (e.g., Hamer et al. 1993, Uttley et al. 1993, Monaghan et al. 1994, 

Dragoo et al. 2000, Gill 1999, Suryan et al. 2000b, etc.), it is clear that Chisik and Gull 

exemplify the extremes of failing and thriving colonies, respectively, in Alaska. 

Consequently, this analysis provides a calibration for seabird performance at the Barren 

Islands and suggests that murres and kittiwakes there are doing modestly well. This 

conclusion is corroborated by data on population trends (Fig. 14.9). 

Indeed, there is a strong correlation between our parameter indices of population health 

and population trends (Fig. 14.12). This relationship seems intuitively reasonable. Our 

parameter indices integrate a suite of values that include behavioral, physiological and 

biological measurements. The combination of these parameters-- and many more 

unmeasured parameters-- is ultimately what determines whether a population will 

increase or decrease. Similarly, population trend represents an integration of all factors 

influencing population biology. 
So why measure dozens of species-parameters throughout summer when simply counting 

birds on plots for 4-6 weeks will provide an indication of population health? One major 

reason is that because, in the future at least, measuring both parameter indices and 

population trend would allow us to distinguish between anthropogenic and natural 

impacts on seabird populations-- something we could not do following the Exxon Valdez 

oil spill (Piatt and Anderson 1996). For example, if studies of murres at a colony yielded 

a parameter index of +0.25 but population trends were stable or decreasing, this would 

indicate that populations were not being limited by food supply, but rather by something 

that was removing large numbers of breeding birds from the population, such as gill-net 

mortality, oil pollution, or hunting. 

The parameter index also offers an instantaneous measure of health of seabird 

populations, whereas population trend data, by definition, needs to be collected over 

many years to establish a trend. One year's sampling may be all that is needed to assess 

the status of populations (e.g., parameter indices for 1995-1999 at Chisik were always 

negative, ranging from -0.24 to -0.62; whereas at Gull they were always positive, ranging 

from +0.19 to +0.29). In contrast, census data can be highly variable among consecutive 

years, and may need to be collected for a decade or longer to establish trends (e.g, 

Dragoo et al. 2000). Finally, census information will be misleading if study plots used for 

census purposes become saturated with breeding birds, or breeding habitat on a colony is 

saturated (as we found on Gull Island). 

Data provided in this study can now be used as a baseline to assess the status of other 

seabird colonies in Alaska. We know that data collected at Chisik, Gull and the Barren 

islands feature an extreme range of parameter values that reflect prey densities below and 

above threshold values. One could visit any murre or kittiwake colony once, collect data 

on a variety of parameter values (not necessarily all of the parameters we measured), and 

calculate standardized deviations From averages using data collected at that colony and 

data provided here in Chapters 8 and 9. From this exercise it should be possible to 

determine whether the health of the colony in question is above or below average. 

Conclusion 

Gull and Chisik islands support relatively small seabird colonies (1000's of birds) that 

apparently were little affected by the Exxon Valdez oil spill. Their population dynamics 

reflect meso-scale habitat characteristics that differ somewhat from the Barren islands, 

which contain orders-of-magnitude more breeding birds (10,000's of birds). Evidence 

suggests that ecological conditions and food supplies for seabirds in the eastern half of 

lower Cook Inlet will support modest population growth and allow recovery from losses 

incurred from the oil spill. Indeed, given the rates of increase observed at Gull and the 

Barren islands in the years since the spill, populations should have already recovered to 

numbers observed prior to the spill (assuming a ca. 35% decline in Cook Inlet 

populations pre- and post-spill; Piatt and Anderson 1996). However, declines at Cook 

Inlet colonies may have accounted for only about 10% of the total mortality in the Gulf of 

Alaska (Piatt and Anderson 1996), and it is not clear whether conditions in lower Cook 

Inlet are typical of elsewhere in the Gulf of Alaska. 
In the absence of quantitative data on food supplies, one way to answer that question is to 

compare seabird parameter indices from Cook Inlet to those gathered in other areas of 

Alaska. Unfortunately, the full suite of parameters measured in our studies has rarely 

been surveyed at other colonies. However, one parameter that has been widely reported is 

breeding success of Black-legged Kittiwakes (Table 14.2). We have established that 

kittiwake breeding swccess exhibits a strong, sigmoidal response to prey density (see 

above, "Hatching, fledging, and breeding success"). We can conclude from that analysis 

that kittiwake breeding success above 0.46 chickslpair represents asymptotic 

reproduction unlimited by food supply, while breeding swccess below 0.0 15 chickslpair 

represents asymptotic reproduction under conditions of severe food deprivation. Breeding 

success that ranges between 0.015 and 0.46 chickslpair represents reproduction that is 

limited to some degree by food supplies that hover around the threshold. 

Using these criteria, we can indirectly assess the status of food supplies for seabirds in 

Alaska by examining the historical breeding success of kittiwakes over time and space 

(Fig. 14.13; data from Hatch 1993, Dragoo et al. 2000). Prior to the regime shift that 

occurred in the late 1970's (Francis et al. 1998), kittiwake productivity in both the Gulf of 

Alaska and Bering Sea was very similar: only a small proportion (5-6%) of colony-years 

of production were food deprived, a large proportion (38-40%) were unlimited by food, 

and slightly more than half (55-56%) were limited to some degree by food supply. After 

the regime shift, but mostly prior to the Exxon Valdez oil spill in 1989, there was a 

marked change in kittiwake productivity (Fig. 14.13). The frequency of food-deprived 

production in the 1980's increased 6-fold (to 37%) in the Gulf of Alaska, while the 

frequency of unlimited production declined by half (to 17%). A similar, but less 

pronounced, shift occurred in the Bering Sea. In the 1990ts, there was a significant 

improvement in feeding conditions in the Gulf of Alaska: Whereas the frequency of 

unlimited production remained the same (at 17%), food-deprived production decreased 

(to 30%) while food-limited production increased (to 54%). By comparison, however, 

conditions in Cook Inlet had improved substantially more than the Gulf as a whole (in 

which Cook Inlet data are included). Of 24 colony-years of production in the 19903, 29% 

were unlimited by food, 50% were limited to some degree, and 29% were unlimited. 

Conditions in the Bering Sea improved even more than in the GOA. 

In summary, this analysis supports the hypothesis that a regime shift in the late 1970's 

reduced food availability to seabirds in the 1980's and 1990's, resulting in widespread 

population declines, lower breeding success, and mass mortality events (Piatt and 

Anderson 1996, Francis et al. 1998). The evidence Wher suggests that there was a slight 

improvement in feeding conditions in the 1990's and that conditions in Cook Inlet are 

better than those in the Gulf as a whole. In general, however, current (to 1999) conditions 

continue to be depressed compared to the 1970's. While seabirds in Cook Inlet colonies 

may have already recovered numerically to pre-spill levels, it is still not clear whether 

conditions elsewhere in the Gulf of Alaska would have supported similar rates of 

recovery during the 1990's. 
Future Prospects 

We can shed some light on the potential for hture seabird recovery by examining 

historical data on small-mesh trawl catches in the Gulf of Alaska (Anderson and Piatt 

1999). A shift in ocean climate during the late 1970's triggered a reorganization of 

community structure in the Gulf of Alaska ecosystem, as evidenced in changing catch 

composition on long-term (1953- 1997) small-mesh trawl surveys. Forage species such as 

pandalid shrimp and capelin declined and never recovered because of recruitment failure 

and predation. Total trawl catch biomass declined by more than 50% and remained low 

through the 1980s. In contrast, recruitment of high trophic-level groundfish improved 

during the 1980s, yielding a > 250% increase in catch biomass during the 1990s. This 

trophic reorganization apparently occurred at the expense of piscivorous sea birds and 

marine mammals. 

Analyses of long-term climate data reveal significant cycles in North Pacific climate, 

including those due to El Nino events (5-7 year cycle) and those to decadal-scale shifts in 

the position and intensity of the Aleutian Low pressure cell in winter. The recent 'warm 

regime', which has not favored forage fish and seabirds, has now exceeded in duration 

any previous decadal-scale warm cycle event on record. It is predicted that we should 

return to a 'cold regime' again in the very near future (Ware 1995, Francis et al. 1998). If 

so, then one can reasonably predict that ecological conditions will return to those that 

favor seabirds in the Gulf of Alaska. In turn, this would undoubtedly hasten the recovery 

of seabirds from damages incurred from the Exxon Valdez oil spill. 

Literature Cited: 

Aebischer, N.J., J.C. Coulson and J.M. Colebrook. 1990. Parallel long-term trends 

across four marine trophic levels and weather. Nature 347:753-755. 

Anderson, P.J., and J.F. Piatt. 1999. Community reorganization in the Gulf of Alaska 

following ocean climate regime shift. Marine Ecology Progress Series 189: 1 17- 

123. 

Anthony, J.A., D.D. Roby , and K.R. Turco. 2000. Lipid content and energy density of 

forage fishesfiom the northern Gulf of Alaska. J. Exper. Mar. Biol. Ecol. 248: 

53-78 

Anker-Nilssen, T., R.T. Barrett, and J.V. Krasnov. 1997. Long- and short-term responses 

of seabirds in the Norwegian and Barents Seas to changes in stocks of prey fish. 

Pp. 683-698 in Proceedings of the International Symposium on the role of Forage 

Fishes in Marine Ecosystems, Univ. of Alaska Sea Grant Rep. 97-01. University 

of Alaska, Fairbanks. 

Baird, P.H. 1994. Black-legged Kittiwake (Rissa tridactyla). In The Birds of North 

America, No. 92 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of 

Natural Sciences; Washington D.C.: The American Ornithologists' Union. 

Barrett, R.T. 1996. Egg laying, chick growth, and food of kittiwakes Rissa tridactyla 

at Hopen, Svalbard. Polar Res. 1 5: 107- 1 13. 

Barrett, R.T., and O.J. Runde. 1980. Growth and survival of nestling Kittiwakes Rissa 

tridactyla in Norway. Ornis. Scand. 11: 228-235. 
Barrett, R.T., M. Asheim, and V. Bakken. 1997. Ecological relationships between two 

syrnpatric congeneric species, Common Murres and Thick-billed Murres, Uria 

aalge and U lomvia, breeding in the Barents Sea. Can. J. Zool. 75: 618-63 1. 

Birkhead, T.R. 1976. Breeding biology and survival of Guillemots Uria aalge. 

Unpubl. Ph.D. thesis, Univ. of Oxford, England. 

Birkhead, T.R., and D.N. Nettleship. 1987. Ecological relationships between 

Common Murres, Uria aalge, and Thick-billed Murres, Uria lomvia, at the 

Gannet Islands, Labrador. 111. Feeding ecology of the young. Can. J. Zool. 

65: 1638-1649. 

Birkhead, T.R., and D.N. Nettleship. 1987. Ecological relationships between 

Common Murres, Uria aalge, and Thick-billed Murres, Uria lomvia, at the 

Gannet Islands, Labrador. 11. Breeding success and site characteristics. Can. J. 

 ZOO^. 65: 1630-1637. 

Birkhead, T.R., and D.N. Nettleship. 1988. Breeding performance of Black-legged 

Kittiwakes, Rissa tridactyla, at a small, expanding colony in Labrador. Can. 

Field Naturalist 102: 20-24. 

Boersma, P.D., J.K. Parrish, and A.B. Kettle. 1995. Common Murre abundance, 

phenology and productivity on the Barren Islands, Alaska: The Exxon Valdez 

oil spill and long-term environmental change. Pp. 820-853 in Exxon Valdez 

Oil Spill: Fate and effects in Alaskan waters (P.G. Wells, J.N. Butler, and J.S. 

Hughes, eds.) American Society for Testing and Materials, Philadelphia, PA. 

ASTM STP 12 19 

Botsford, L. W., J. C. Castilla and C. H. Peterson. 1997. The management of fisheries 

and marine ecosystems. Science 277: 509-5 15. 

Bryant, R., I.L. Jones, and J. M. Hipfner. 1999. Responses to changes in prey availability 

by Common Murres and Thick-billed Murres at the Gannet Islands, Labrador. 

Can. J. Zool. 77: 1278-1287. 

Burger, A.E. and J.F. Piatt. 1990. Flexible time budgets in breeding Common Murres: 

Buffers against variable prey availability. Studies in Avian Biology 14:7 1-83. 

Byrd, G.V., R.L. Merrick, J.F. Piatt, and B.L. Norcross. 1997. Seabird, marine 

mammal and oceanography coordinated investigations (SMMOCI) near 

Unimak Pass, Alaska. Pp. 35 1-364 in: Forage Fishes in Marine Ecosystems. 

Proceedings of the International Symposium on the Role of Forage Fishes in 

Marine Ecosystems. Alaska Sea Grant College Program Report No. 97-01. 

University of Alaska Fairbanks. 

Cairns, D.K. 1987. Seabirds as indicators of marine food supplies. Biol. Oceanogr. 

5:261-271. 

Cairns, D.K. 1992a. Bridging the gap between ornithology and fisheries science: use 

of seabird data in stock assessment models. Condor 94:811-824. 

Cairns, D.K. 1992b. Population regulation of seabird colonies. Current Ornithol. 

9137-61. 

Dragoo, D.E., G.V. Byrd, and D.B. Irons. 2000. Breeding status and population 

trends of seabirds in Alaska in 1999. U.S. Fish and Wildl. Sew. Report 

AMNWR 2000102. Homer, AK. 

Erikstad, K.E., T. Tveraa, and R.T. Barrett. 1995. Adult survival and chick production in 

long-lived seabirds: a 5-year study of the kittiwake Rissa tridactyla. Pp. 47 1-477 
in: Ecology of Fjords and Coastal Waters (Skjoldal, H.R., C. Hopkins, K.E. 

Erikstad, and H.P. Leinaas, eds.). Elsevier Science, London. 

Erikstad, K.E., Asheim, M., Fauchald, P., Dahlhaug, L. and Tveraa, T. 1997. Adjustment 

of parental effort in the puffin; the roles of adult body condition and chick size. 

Behavioural Ecology and Sociobiology 40: 95-1 00. 

Erikstad, K.E., Fauchald, P., Tveraa, T, and Steen. H. 1998. On the cost of reproduction 

in long-lived birds; the influence of environmental variability. Ecology 79: 178 1 - 

1788. 

Ford, R.G., J.A. Wiens, D. Heinemann, and G.L. Hunt. 1982. Modelling the sensitivity of 

colonially breeding marine birds to oil spills: Guillemot and kittiwake populations 

on the Pribilof Islands, Bering Sea. Journal of Applied Ecology 19: 1-3 1. 

Francis, R.C., S.R. Hare, A.B. Hollowed, and W.S. Wooster. 1998. Effects of 

interdecadal climate variability on the oceanic ecosystems of the NE Pacific. 

Fisheries Oceanography 7: 1-2 1. 

Furness R.W., and C.J. Camphuysen. 1997. Seabirds as monitors of the marine 

environment. ICES J. Mar. Sci. 54:726-737. 

Furness, R.W. and M.L. Tasker. 1997. Seabird consumption in sand lance MSVPA 

models for the North Sea, and the impact of industrial fishing on seabird 

population dynamics. Pp. 147- 169 in Proceedings of the International Symposium 

on the role of Forage Fishes in Marine Ecosystems, Univ. of Alaska Sea Grant 

Rep. 97-01, Univ. of Alaska, Fairbanks, AK. 

Gabrielsen, G.W. 1994. Energy expenditure in Arctic seabirds. Ph.D. Thesis, Univ. 

Tromso, Norway. 

Galbraith, H. 1983. The diet and feeding ecology of breeding Kittiwakes Rissa tridactyla. 

Bird Study 30: 109-120. 

Gaston, A.J. 1985. Development of the young in the Atlantic Alcidae. Pp. 319-354 in The 

Atlantic Alcidae (D.N. Nettleship and T.R. Birkhead, eds). Academic Press, 

London. 

Gaston, A.J. and Jones, I.L. 1998. The Auks. Oxford University Press, Oxford. 

Gill, V. A. 1999. Breeding performance of Black-legged Kittiwakes (Rissa tridactyla) in 

relation to food availability: a controlled feeding experiment. M.S. Thesis, 

University of Alaska, Anchorage. 

Golet, G.H., D.B. Irons, and J.A. Estes. 1998. Survival costs of chick rearing in 

black-legged kittiwakes. Journal of Animal Ecology 672327-841. 

Golet, G.H., and D.B. Irons. 1999. Raising young reduces body condition and fat 

stores in black-legged kittiwakes. Oecologia 120: 530-538. 

Goss-Custard, J.D. 1970. The responses of redshank (Tringa totanus (L.)) to spatial 

variations in the density of their prey. J. Anim. Ecol. 39:9 1 - 1 13. 

Green, R.F. 1980. Bayesian birds: a simple test of Oaten's stochastic model of optimal 

foraging. Theor. Pop. Biol. 18: 244-256. 

Hamer, K.C., R.W. Furness, and R.W.G. Caldow. 1991. The effects of changes in food 

availability on the breeding ecology of great skuas Catharacta skua in Shetland. J. 

Zool. Lond. 223:175-188. 

Hamer, K.C., P. Monaghan, J.D. Uttley, P. Walton and M.D. Burns. 1993. The 

influence of food supply on the breeding ecology of Kittiwakes Rissa 

tridactyla in Shetland. Ibis 135: 
Harding, A.A., T. van Pelt, J.F. Piatt, and A.S. Kitaysky. 2001. Parental flexibility: 

An experimental reduction of provisioning effort in response to chick 

nutritional status in the horned puffin Fratercula corniculata. Mss. submitted 

to Animal Behavior. 

Harris, M.P., and S. Wanless. 1988. The breeding biology of guillemots Uria aalge 

on the Isle of May over a six year period. Ibis 130: 172- 192. 

Harris, M.P., and S. Wanless. 1985. The food consumption of young Common 

Murres (Uria aalge) in the wild. Colonial Waterbirds 18: 209-21 3. 

Harris, M.P., and S. Wanless. 1990. Breeding success of British kittiwakes Rissa 

tridactyla in 1986-1988: Evidence for changing conditions in the northern 

North Sea. J. Appl. Ecol. 27: 172-187. 

Hassell, M.P. and R.M. May. 1974. Aggregation of predators and insect parasites and 

its effect on stability. J. Anim. Ecol. 43567-594. 

Hassell, M.P., J.H. Lawton, and J.R. Beddington. 1977. Sigrnoid functional responses 

by invertebrate predators and parasitoids. J. Anim. Ecol. 46: 249-262. 

Hatch, S.A. 1983. The fledging of common and thick-billed murres on Middleton 

Island, Alaska. J. Field Ornith. 54: 266-274. 

Hatch, S.A., G.V. Byrd, D.B. Irons, and G.L. Hunt. 1993. Status and ecology of 

kittiwakes (Rissa tridactyla and R. brevirostris) in the North Pacific. Pages 

140-153 in K. Vermeer, K.T. Briggs, K.H. Morgan, and D. Siegel-Causey, 

editors, The Status, Ecology, and Conservation of Marine Birds of the North 

Pacific. Special Publication, Canadian Wildlife Service, Ottawa. 

Hatchwell, B. J. and T.R. Birkhead. 1 99 1. Population dynamics of common 

guillemots Uria aalge on Skomer Island, Wales. Ornis Scandinavica 22: 55- 

59. 

Hedgren, S. 1980. Reproductive success of guillemots Uria aalge on the island of 

Stora Karlso. Ornis Fennica 57: 49-57. 

Holling, C.S. 1959. The components of predation as revealed by a study of small 

mammal predation of the European pine sawfly. Can. Entomol. 91:293-320. 

Hudson, P.J. 1985. Population parameters for the Atlantic Alcidae. Pp. 233-261 in: The 

Atlantic Alcidae (D.N. Nettleship and T.R. Birkhead, eds.). Academic Press. New 

York. 

Jacobsen, K.O., K.E. Erikstad, and B.E. Saether. 1995. An experimental study of the 

costs of reproduction in the kittiwakes Rissa tridactyla. Ecology 76: 1636-1642. 

Johnsen, I., Erikstad, K.E. and Sather, B.E. 1994. Regulation of parental investment in a 

long-lived seabird, the puffin Fratercula arctica; an experiment. Oikos, 7 1 ; 273- 

278. 

Kitaysky, A.S. 1999. Metabolic and developmental responses of alcid chicks to 

experimental variation in food intake. Physiological and Biochemical Zoology 72: 

462-473. 

Kitaysky, A.S., J.C. Wingfield, and J.F. Piatt. 1998. Dynamics of food availability, body 

condition and physiological stress response in breeding Black-legged kittiwakes. 

Functional Ecology 13:577-584. 

Kitaysky, A.S., J.F. Piatt, J.C. Wingfield, and M. Romano. 1999. The adrenocortical 

stress-response of Black-legged Kittiwake chicks in relation to dietary 

restrictions. Journal of Comparative Physiology (B):303-3 10. 
Kitaysky A.S., Piatt J.F., Wingfield J.C. 2000. Seasonal dynamics of corticosterone 

and LH in breeding Common Murres in relation to fluctuations in food 

supply. In preparation, Physiological and Biochemical Zoology 

Kitaysky, A., J. Wingfield, and J. Piatt. 2001.Corticosterone facilitates begging and 

affects resource allocation in the Black-legged Kittiwake. In Press. Behavioral 

Ecology. 

Lima, S.L. 1983. Downy woodpecker foraging behavior: foraging by expectation and 

energy intake rate. Oecologia 58: 232-237. 

Nysewander, D., C.H. Dipple, G.V. Byrd, and E.P. Knudtson. 1993. Effects of the 

T/V Exxon Valdez oil spill on murres: A perspective from observations at 

colonies. NRDA Bird Study No. 3 Final Rep., U.S. Fish and Wildl. Sew., 

Homer AK. 40 pp. 

Mehlum, F., G.L. Hunt, Jr., Z. Klusek, and M.B. Decker. 1999. Scale-dependent 

correlations between the abundance of Briinnich's guillemots and their prey. 

Journal of Animal Ecology 68:60-72. 

Monaghan, P., J.D. Uttley, M. Burns, C. Thane, and J. Blackwood. 1989. The - 

relationship between food supply, reproductive effort, and breeding success in 

Arctic Terns Sterna paradisea. Journal of Animal Ecology 58:261-274. 

Monaghan, P., J.D. Uttley, and M. Burns. 1992. Effects of changes in food 

availability on reproductive effort in Arctic Terns Sterna paradisea. Ardea 80: 

71-81. 

Monaghan, P. P. Walton, S. Wanless, J.D. Uttley, and M.D. Burns. 1994. Effects of 

- prey abundance on the foraging behaviour, diving efficiency and time 

allocation of breeding Guillemots Uria aalge. Ibis 136:2 14-222. 

Murdoch, W.W. and A. Oaten. 1975. Predation and population stability. Adv. Ecol. Res. 

9:l-125. 

Murphy, E.C, A.M. Springer, and DG. Roseneau. 1991. High annual variability in 

reproductive success of kittiwakes (Rissa tridactyla L.) at a colony in western 

Alaska. Journal of Animal Ecology 605 15-534. 

Phillips, R.A., R.W.G. Caldow, and R.W. Furness. 1996. The influence of food 

availability on the breeding effort and reproductive success of Arctic Skuas 

Stercorarius parasiticus. Ibis 13 8: 4 10-4 19. 

Piatt, J.F. and D.N. Nettleship. 1985. Diving depths of four alcids. Auk 102: 293-297. 

Piatt, J.F. 1987. Behavioural Ecology of Common Murre and Atlantic Puffin 

Predation on Capelin: Implications for Population Biology. Ph.D. Thesis, 

Department of Biology, Memorial University of Newfoundland, St. John's, 

Nfld. 3 1 1 pp. 

Piatt, J.F. 1990. Aggregative response of Common Murres and Atlantic Puffins to 

their prey. Studies in Avian Biology 14:36-5 1. 

Piatt, J.F. 2001. Survival of Adult Murres and Kittiwakes in Relation to Forage Fish 

Abundance. Exxon Valdez Oil Spill Restoration Project Annual Report 

(Restoration Project 00338), U.S. Geological Survey, Anchorage, Alaska. 

Piatt, J.F., and D.A. Methven. 1992. Threshold foraging behavior of baleen whales. 

Marine Ecology Progress Series 84:205-2 10. 

Piatt, J.F. and R.G. Ford. 1996. How many seabirds were killed by the Exxon Valdez oil 

spill? American Fisheries Society Symposium 18:7 12-7 19. 
Piatt, J.F., C.J. Lensink, W. Butler, M. Kendziorek, and D. Nysewander. 1990. 

Immediate impact of the Enon Valdez oil spill on marine birds. Auk 107:387- 

397. 

Piatt, J.F., and P. J. Anderson. 1996. Response of Common Murres to the Exxon Valdez 

oil spill and long-term changes in the Gulf of Alaska marine ecosystem. Pp. 720- 

737 in: Enon Valdez Oil Spill Symposium Proceedings. Rice, S. D., R. B. Spies, 

D. A. Wolfe and B. A. Wright (Eds). American Fisheries Society Symposium 18, 

Bethesda, Maryland. 

Piatt, J.F., G. Drew, T.Van Pelt, A. Abookire, A. Nielsen, M. Shultz, and A. Kitaysky. 

1999. Biological effects of the 199711998 ENS0 event in lower Cook Inlet, 

Alaska. PICES Scientific Report No. 10:93- 100. 

Robards, M.D., J.F. Piatt, A.B. Kettle, and A.A. Abookire. 1999. Temporal and 

geographic variation in fish communities of lower Cook Inlet, Alaska. Fishery 

Bulletin 97:962-977. 

Robards, M.D. 2000. Ecology and demographics of Pacific sand lance, Ammodytes 

hexapterus Pallas, in lower Cook Inlet, Alaska. M.Sc. Thesis, Memorial 

University of Newfoundland, St. John's, Canada. 105 pp. 

Roberts, B.D., & Hatch, S.A. 1993. Behavioral ecology of Black-legged Kittiwakes 

during chick-rearing in a failing colony. Condor 95, 330-342. 

Romano, M.D. 2000. Effects of diet on growth and development of nestling seabirds. 

M.Sc. Thesis, Oregon State University, Corvallis OR. 59 pp. 

Roseneau, D.G., A.B. Kettle, and G.V. Byrd. 1997. Common Murre population 

monitoring at the Barren Islands, Alaska, 1996. Exxon Valdez Oil Spill 

Restoration Ann. Rep. (Restoration Project 96144), U.S. Fish and Wildlife Serv., 

Alaska Maritime NWR, Homer, Alaska. 

Roseneau, D.G., A.B. Kettle, G.V. Byrd. 1998. Common murre population monitoring at 

the Barren Islands, Alaska, 1997. Exxon Valdez Oil Spill Trustee Council 

Restoration Project 97144 Annual Report, U.S. Fish and Wildlife Service, Alaska 

Maritime National Wildlife Refuge, Homer, Alaska. 

Roseneau, D.G., A.B. Kettle, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration Project 

001639, U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 

Safina, C. and J. Burger. 1985. Common tern foraging: seasonal trends in prey fish 

densities and competition with bluefish. Ecology 66: 1457- 1463. 

Safina, C. and J. Burger. 1988. Prey dynamics and the breeding phenology of 

common terns (Sterna hirundo). Auk 105 :720-726. 

Sagar, P. and D.S. Homing. 1998. Mass related survival of fledging sooty shearwaters 

PufJinus griseus at the Snares, New Zealand. Ibis 140: 329-339. 

Sowls, A.L., S.A. Hatch, and C.J. Lensink. 1978. Catalog of Alaskan seabird colonies 

U.S. Fish and Wildlife Service FWSIOBI - 78/78. Washington, D.C. 

Spies, R.B., S.D. Rice, D.A. Wolfe, and B.A. Wright. 1996. The effects of the Exxon 

Valdez oil spill on the Alaskan coastal environment. Pp. 1- 16 in: Exxon Valdez 

Oil Spill Symposium Proceedings. Rice, S. D., R. B. Spies, D. A. Wolfe and B. A. 

Wright (Eds). American Fisheries Society Symposium 18, Bethesda, Maryland. 
Steele, J.H. 1974. The structure of marine ecosystems. Harvard Univ. Press, Cambridge, 

MA. 

Stephenson, R.L. 1997. The other F: Forage considerations in fisheries management. Pp. 

645-654 in Proceedings of the International Symposium on the role of Forage 

Fishes in Marine Ecosystems, Univ. of Alaska Sea Grant Rep. 97-01, Univ. of 

Alaska, Fairbanks, AK. 

Suddaby, D and N. Ratcliffe. 1997. The effects of fluctuating food availability on 

breeding Arctic Terns (Sternaparadisaea). Auk 1 14: 524-530. 

Suryan, R.M., D.B. Irons, and J. Benson. 2000a. Prey switching and variable foraging 

strategies of black-legged kittiwakes and the effect on reproductive success. 

Condor 102: 374-384 

Suryan, R. M., D. B. Irons, J. Benson, and M. Kaufman. 2000b. Foraging Ecology, 

Reproductive Biology, and Population Dynamics of Black-legged Kittiwakes 

(Rissa tridactyla) in Prince William Sound, Alaska. Appendix E in D. C. Duffy, 

compiler, APEX project: Alaska Predator Ecosystem Experiment in Prince 

William Sound and the Gulf of Alaska. Exxon Valdez Oil Spill Restoration 

Project Final Report, (Restoration Project 00 163), U.S. Fish and Wildlife Service, 

Anchorage, Alaska. 

Sydeman, W.J., Hester M.M., Gress, F., Martin P., and J. Buffa. 2001. Climate 

change, reproductive sucess, and diet composition of marine birds in the 

southern California Current system, 1969- 1997. Progress in Oceanography. In 

press. 

Steams, S.S. 1992. The Evolution of Life Histories. Oxford University Press, New 

York. 

Uttley, J.D., P. Walton, P. Monaghan, and G. Austin. 1994. The effects of food 

abundance on breeding performance and adult time budgets of Guillemots 

Uria aalge. Ibis 136:205-2 13. 

Van Pelt, T., J.F. Piatt, B.K. Lance, and D.D. Roby. 1997. Proximate composition and 

energy density of some North Pacific forage fishes. Comparative Biochemistry 

and Physiology 118(A): 1393-1398. 

Ware, D.M. 1995. A century and a half of change in the climate of the NE Pacific. 

Fisheries Oceanography 4:267-277. 

Watanuki, Y., Y. Naito, and J. Schauer. 1992. Chick diet and daily activity pattern of 

Common Murres and Black-legged Kittiwakes at Bluff seabird colony, Norton 

Sound, Alaska. Proc. NIPR Symp. Polar Biol. 5: 98-104. 

Weimerskirch, H., P.A. Prince, and L. Zimmermann. 2000. Chick provisioning by the 

yellow-nosed albatross: response of foraging effort to experimentally increased 

costs and demands. Ibis 142: 103-1 10. 

Weimerskirch, H., L. Zimmermann, and P.A. Prince. 2001. Influence of environmental 

variability on breeding effort in a long-lived seabird, the yellow-nosed albatross. 

Beh. Ecol. 12: 22-30. 

Williams, T.D. and J.P. Croxall. 1990. Is chick fledging weight a good index of food 

availability in seabird populations? Oikos 59: 4 14-4 16. 

Williams, J.C., M. Ortwerth, N. Rojek, and L. Scharf. 1998. Biological monitoring at 

Buldir Island, Alaska in 1997: Summary appendices. U.S. Fish and Wildl. Serv. 

Rep. AMNWR 98/05. Adak. Alaska. 184 pp. 
Zador, S., and J.F. Piatt. 1998. Time-budgets of Common Murres at a declining and 

increasing colony in Alaska. Condor 10 1 : 149- 152. 

Zador, S., A. Harding, J. Piatt, L. Ochikubo and A. Nielsen. 1997. Monitoring Seabird 

Populations in Areas of Oil and Gas Development on the Alaskan Continental 

Shelf Monitoring Populations And Productivity Of Seabirds At Colonies In 

Lower Cook Inlet, Alaska, 1995. OCS Study, MMS 95-01 3. 
Table 1.1. Characteristics and measurement of seabird numerical and functional response parameters. 

Measurable Parameters 

Numerical Response 

Adult survivorship 

Juvenile survivorship 

Clutch size 

Brood size 

Hatching success 

Fledging success 

Breeding success 

Chick growth rate 

Chick fledging weight 

Hypothesized Relationship to Prey Density 

Direction Form Threshold Buffer 

Measurement Time 

Parameter Response 

Methods 

Functional Response 

Adult foraging time activity 

Adult free time activity 

Adult meal size 

Adult body mass 

Dive time, frequency, depth 

Prey capture rate 

Aggregative response (tracking) 

surveys 

Aggregation index (group size) 

Foraging range 

Adult diet diversity 

Chick diet diversity 

Chick feeding rate 

Chick meal size 

positive 

positive 

positive 

positive 

positive 

positive 

positive 

positive 

positive 

negative 

positive 

positive 

positive 

negative 

positive 

positive 

positive 

negative 

negative 

negative 

positive 

positive 

-exponential 

-exponential 

-exponential 

-exponential 

sigmoidal 

sigmoidal 

sigmoidal 

sigmoidal 

sigmoidal 

logarithmic 

-exponential 

sigmoidal 

-exponential 

logarithmic 

-exponential 

sigmoidal 

-exponential 

logarithmic 

logarithmic 

logarithmic 

sigmoidal 

-exponential 

low 

moderate 

moderate 

moderate 

moderate 

moderate 

moderate 

moderate 

moderate 

low 

moderate 

moderate 

low 

moderate 

moderate 

moderate 

low 

moderate 

low 

low 

moderate 

low 

no 

no 

maybe 

maybe 

yes 

Yes 

yes 

yes 

yes 

2 year 

2-5 year 

1 year 

1 year 

1 year 

1 year 

1 year 

1 year 

1 year 

days 

days 

days 

days 

days 

hours 

hours 

hours 

days 

days 

days 

days 

days 

15-20 years 

15-20 years 

15-20 years 

15-20 years 

15-20 years 

15-20 years 

15-20 years 

15-20 years 

15-20 years 

3-5 years 

3-5 years 

3-5 years 

3-5 years 

1-2 years 

1-2 years 

1-2 years 

1-2 years 

3-5 years 

3-5 years 

3-5 years 

3-5 years 

3-5 years 

Banding/re-sighting 

Banding/re-sighting 

Visual observations (VO) 

VO, Remote camera observation 

Visual observation 

VO, Remote camera observation 

VO, Remote camera observation 

Direct measurement 

Direct measurement 

VO, Radio telemetry, TDR's 

VO, Radio telemetry 

Adult collections 

Adult collection/capture 

TDR's, Radio telemetry 

Aquarium observations 

At-sea bird/hydroacoustic 

At-sea bird surveys 

At sea surveys, Radio telemetry 

Collections, Stable isotopes 

Collections, Stable isotopes 

VO, Remote camera observations 

Chick meal collections 
Table 4.1. Mean catch-per-unit-effort (CPUE and standard error) of all fishes, and major fish species, captured per mid-water 

trawl (n=159) near the Barren Islands, Kachemak Bay and Chisik Island in 1996-1999. 

Area Year No. All fish species P. sand lance Herring Walleye pollock Capelin 

trawls mean stderr mean stderr mean stderr mean stderr mean stderr 

Barrens 1996 19 481.5 228.1 5.3 3.3 0.0 0.0 458.1 227.3 17.7 16.6 

Barrens 

Barrens 

Barrens 

Kachemak 

Kachemak 

Kachemak 

Kachemak 

Chisik 

Chisik 

Chisik 

Chisik 
Table 4.2. Species composition of mid-water trawl catches at the Barren Islands, Kachemak Bay, and near Chisik Island, 1996-1999. Species that comprised 

at least 1% of the catch are listed. For a complete list of species see appendices 4.2-4.4. Species richness and species diversity (Shannon-Wiener Diversity 

Index) are listed for each area and year. See methods for details. 

Common name Scientific name Barrens Kachemak Chisik 

1996 1997 1998 1999 96-99 1996 1997 1998 1999 96-99 1996 1997 1998 1999 96-99 

Pacific sandlance Ammodytes hexapterus 1 86 56 94 67 74 32 77 96 83 24 75 98 31 60 

Pacific herring 

Walleye pollock 

Capelin 

Pink salmon 

Pacific sandfish 

Longfin smelt 

Pacific Cod 

King (chinook) salmon 

Lumpenus spp. 

Eulachon 

Lingcod 

Lumpsuckers and snailfishes 

Snake prickleback 

Arrowtooth flounder 

Red (sockeye) salmon 

Armorhead sculpin 

Species richness 

Species diversity 

Clupea pallasi 

Theragra chalcogramma 

Mallotus villosus 

Oncorhynchus gorbuscha 

Trichodon trichodon 

Spirinchus thaleichthys 

Gadus macrocephalus 

Oncorhynchus tshawytscha 

Lumpenus spp. 

Thaleichthys pacificus 

Ophiodon elongatus 

Cyclopteridae 

Lumpenus sagitta 

Atherestes stomias 

Oncorhynchus nerka 

Gymnocanthus galeatus 
Table 5.1. Sampling time periods and number of beach seine sets conducted at the Barren Islands, Chisik Island and Kachemak Bay 

during 1995-1 999. In parentheses are the number of sets conducted during the June-August window that we used for comparison of 

results among years and areas. Specifications of seine nets "P, "A", "K and "C" are provided in Methods. 

Year Barren Islands Chisik Island Kachemak Bay 

Sampling period Net used No. Sets Sampling period Net used No. Sets Sampling period Net used No. Sets 

1995 No Samples "P" 0 (0) 15 June "K" 1 (1) 16 Jun - 26 Jul "K 60 (60) 

1996 2 Jul- 8 sep "A 36 (32j 3Jul-17Aug "A 30 (3oj 8Feb-11Dec "K" 283 (202j 

1997 19 Jun - 2 Sep "A" 28 (24) 4Jul-16Aug "A 18 (18) 6Feb-16Oct "K 228 (161) 

1998 16 Jun - 8 Sep "A" 30 (26) 23 Jun - 9 Aug "C" 21 (21) 29 May - 7 Sep "K 1 90 i149j 

1999 21~ur-1-8~ep "A" 26 (24j 21 May - 26 AU~ "c" 29 (24j 15 May - 26 AU~ "K" I 17 (99j 

TOTAL 120 (1 06) 99 (94) 878 (671) 
Table 5.2. Numbers of fish collected for morphometric measurements. Length data were collected on all these 

specimens; a subset (particularly sand lance) were also weighed and assessed for sex, fecundity and age. 

Kachemak Bay Chisik Island Barren Islands 

Species No. Fish Species No. Fish Species No. Fish 

Alaska Plaice 1 Capelin 5 Capelin 13 

Arctic Shanny 

Armorhead Sculpin 

Brown lrish Lord 

Buffalo Sculpin 

Butter Sole 

Capelin 

Chinook Salmon 

Chum Salmon 

Coho Salmon 

Crescent Gunnel 

Cuttlefish 

Dolly Varden 

Dover Sole 

English Sole 

Eulachon 

Flathead Sole 

Gadidae 

Great Sculpin 

Hexagrammidae 

High Cockscomb 

Kelp Greenling 

Lemon Sole 

Lingcod 

Liparidae 

Lobefin Snailfish 

Longfin Smelt 

Masked Greenling 

Myoxocephalus Spp. 

Northern Ronquil 

Northern Sculpin 

Oncorhynchus Spp. 

Pacific Cod 

Pacific Halibut 

Pacific Herring 

Pacific Sand Lance 

Pacific Sandfish 

Pacific Staghorn Sculpin 

Pacific Tomcod 

Padded Sculpin 

Painted Greenling 

Petrale Sole 

Pholidae 

Pink Salmon 

Pleuronectidae 

Prowfish 

Red lrish Lord 

Rock Greenling 

Rock Sole 

Sablefish 

Saddleback Gunnel 

Saffron Cod 

Sand Shrimp 

Sand Sole 

Sawback Poacher 

Sebastes Spp. 

Silverspotted Sculpin 

Slender Eelblenny 

Snake Prickleback 

Sockeye Salmon 

Soft Sculpin 

Starry Flounder 

Sturgeon Poacher 

Surf Smelt 

Three-Spined Stickleback 

Tidepool Sculpin 

Tubenose Poacher 

Unidentiiied Larval Fish 

Walleye Pollock 

Whitespotted Greenling 

Yellowfin Sole 

Total 

Chinook Salmon 

Chum Salmon 

Cottidae Spp. 

Crescent Gunnel 

Dolly Varden 

Eulachon 

Flathead Sole 

Great Sculpin 

Humpy Shrimp 

Lingcod 

Longfin Smelt 

Lumpenus Spp. 

Myoxocephalus Spp. 

Onwrhynchus Spp. 

Osmeridae 

Osmeridae Larvae 

Pacific Cod 

Pacific Herring 

Pacific Sand Lance 

Pacific Sandfish 

Pacific Staghorn Sculpin 

Rock Greenling 

Rock Sole 

Sand Shrimp 

Silverspotted Sculpin 

Smooth Aligatorfish 

Snake Prickleback 

Sockeye Salmon 

Starry Flounder 

Sturgeon Poacher 

Surf Smelt 

Three-Spined Stickleback 

Unidentified Larval Fish 

Walleye Pollock 

Whitespotted Greenling 

Total 

1 Pacific Sand ~ance 3839 

5 Total 3852 

34 

1 

74 

10 

3 

4 

2 

3 

9 

7 

4 

154 

17 

1 

34 

62 

924 

2 

55 

1 

1 

3 

1 

3 

15 

2 

23 

1 

9 

10 

65 

2 

8 

1555 
Table 5.3. Total beach seine catches at the Barren Islands, Chisik Island and Kachemak Bay during June -August, 1995-1999. 

Fish species Barren Islands Chisik Island Kachemak Bay 

1995 1996 1997 1998 1999 1995 1996 1997 1998 1999 1995 1996 1997 1998 1999 

Totalfish No Data 129033 45821 19533 2580 31 1044 1153 473 1409 27944 110150 100055 279954 128272 

Pacific Herring 

Pink Salmon 

Chum Salmon 

Coho Salmon 

Sockeye Salmon 

Chinook Salmon 

Dolly Varden 

Unidentified Salmonid 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

Surf Smelt No Data 22 6 62 1 0 0 1 5 4 9 22 87 50 19 

Capelin NoData 12 0 1 0 4 13 0 1 0 1 0 5060 5 0 

~ulachon No Data 0 0 00 03200 0 0 0 1 0 

Longfin Smelt No Data 0 0 00 05090 0 0 0 52 0 

Unidentified Larval Smelt No Data 0 0 00 00010 0 0 0 0 2 

Unidentified Smelt No Data 0 0 10 00002 0 0 0 0 0 

Pacific Cod No Data 480 3317 28 0 21 74 0 5 0 2066 2334 1656 111 37 

Pacific Tomcod No Data 0 0 0 0 0 2 0 0 0 220 440 79 25 3 

Saffron Cod No Data 0 0 0 0 0 0 0 0 0 54 437 1450 2126 840 

Walleye Pollock No Data 05471 371 61 0 0 0 0 0 4 1406 0 19 14 

Unidentified Juvenile Gadid No Data 0498 26 2 0 0 0 0 0 0 98 18 1072 300 

Pacific Sandfish No Data 0265 10 00000 9 36 9 2 6 

Arctic Shanny No Data 0 0 00 00000 0 1 3 1 1 

Pacific Snake Prickleback No Data 0 0 0 0 1119 23 6 7 163 14 300 132 268 

Daubed Shanny No Data 0 0 00 00000 0 7 0 0 0 

Slender Eelblenny No Data 0 0 00 00000 0 268 8 1367 0 

Unidentified Lumpenus Spp. No Data 0 0 00 00020 0 0 0 1242 1403 

High Cockscomb No Data 0 0 00 00000 0 0 1 1 2 

Saddleback Gunnel No Data 0 0 00 00000 0 0 0 1 3 

Crescent Gunnel No Data 0 0 0 0 0 11 0 0 0 14 43 112 104 97 

Unidentified Gunnel No Data 0 0 20 00000 0 0 0 0 1 

Sand Lance No Data 127830 26516 15261 8 0 233 95 231 5 18612 78069 78847 205104 1 14587 

Prowfish No Data 0 0 01 00000 0 1 0 1 2 

Rock Greenling No Data 12 10 I1000 25 22 18 50 60 

Kelp Greenling No Data 4 0112 00000 0 44 130 0 0 

Masked Greenling No Data 0 0 00 00000 3 0 3 35 31 

Mitespotted Greenling No Data 0 0 0 0 0 22 0 0 2 51 118 335 102 236 

Painted Greenling No Data 0 0 00 00000 0 0 0 0 0 

Unidentified Greenling No Data 2768500000 0 0 0 43 55 

Linacod NoData 13 127 570 45 0 0 0 I 2 0 5 190 160 131 

sablefish No Data 0 0 00 00000 46 6 0 0 0 

Silverspotted Sculpin No Data 15 0 0 0 0 2 0 0 0 45 70 81 35 128 

Crested Sculpin No Data 0 0 00 00000 0 0 0 0 0 

Tidepool Sculpin No Data 0 0 00 00000 0 0 0 1 0 

Eyeshade Sculpin No Data 0 0 00 00000 0 0 0 0 1 

Warty Sculpin No Data 0 0 00 00000 0 13 0 0 0 

NorthernSwlpin NoData 227 13 0 0 0 0 0 0 0 0 0 2 23 4 

Buffalo Sculpin No Data 0 0 00 00000 21 4 2 3 53 
Table 5.3. Total beach seine catches at the Barren Islands, Chisik Island and Kachemak Bay during June -August, 1995-1999. 

Soft Sculpin No Data 0 0 00 00000 2 0 0 0 0 

Pacific Staghorn Sculpin No Data 0 0 00 0202233 7 4 8 0 5 

Great Sculpin No Data 0 0 10 3 2 32 9 2 83 194 240 280 583 263 

Padded Sculpin No Data 0 0 00 02000 0 1 1 0 24 

Sharpnose Sculpin No Data 0 0 00 0 0 0 0 0 0 0 0 0 3 

Red Irish Lord No Data 0 0 00 00000 0 0 0 1 4 

Yellow Irish Lord No Data 0 0 00 00000 0 1 1 1 1 

Brown Irish Lord No Data 0 0 00 00000 0 0 0 0 2 

Roughspine Sculpin No Data 0 0 00 00000 0 0 0 0 0 

Ribbed Sculpin No Data 0 0 00 00000 0 1 0 0 0 

Scalyhead Sculpin 

Unidentified Sculpin 

Unidentified Larval Swlpins 

Threespine Stickleback 

Sebastes spp. 

Northern Rockfish 

Pipefish 

Wolf-Eel 

Kelp Clingfish (Remicola) 

Unidentified Eelpout Spp. 

Smooth kigatorfish 

Tubenose Poacher 

Sawback Poacher 

Sturgeon Poacher 

Unidentified Poacher 

Smooth Lumpsucker 

Snailfish Spp 

Ribbon Snailfish 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

Petrale Sole No Data 0 0 00 00000 12 0 0 0 0 

Flathead Sole No Data 0 0 00 00000 4 2 0 4 0 

Pacific Halibut No Data 0 0 00 01000 1 3 20 15 24 

Butter Sole No Data 7 3 11 00000 2 2 0 50 0 

Dover Sole No Data 0 0 00 00000 0 0 0 2 2 

Sand Sole No Data 0 0 00 00000 0 0 0 6 13 

Alaska Plaice No Data 0 0 00 00000 0 0 0 0 1 

Hybrid Sole No Data 0 0 01 00000 0 0 0 0 0 

Rock Sole No Data 0 13 0 0 0 62 0 1 0 58 288 549 496 375 

Yellowtin Sole No Data 0 0 00 00000 0 0 1 43 51 

EnglishSole No Data 0 0 00 00000 2 0 0 14 14 

Starry Flounder No Data 0 0 0 1 0 51 10 14 5 13 31 29 9 10 

Unidentified Flaffish No Data 119 019 00000 0 0 0 17 66 

Unid JuvILawal Fish No Data 0 0 0 1 0 56 672 2 161 0 0 0 8 0 

Unidentified Fish No Data 21220 0 20 0 0 0 0 0 0 0 0 0 0 

Unidentified Larval Fish No Data 0 304 2873 1283 0 0 0 0 0 0 0 0 0 0 
Table 5.4. Beach seine catch composition by actual numbers (A) and by proportions (B) of major taxonomic 

groups at the Barren Islands, Chisik Island, and Kachemak Bay, during June-Aug, 1995-1999. 

A. Total Fish 

Island Year Herring Salmonids Osmerids Gadids Sand lance Sculpins Flatfish Other Total 

Barren Islands 1995 0 0 0 0 0 0 0 0 0 

Barren lslands 

Barren lslands 

Barren lslands 

Barren lslands 

Chisik lsland 

Chisik lsland 

Chisik lsland 

Chisik lsland 

Chisik lsland 

Kachemak Bay 

Kachemak Bay 

Kachemak Bay 

Kachemak Bay 

Kachemak Bay 1999 219 8338 21 1194 114587 752 556 2605 128272 

Total -Barren Islands 0 682 105 10254 169615 9378 66 6867 196967 

Total -Chisik Island 283 1641 50 102 564 211 144 1115 4110 

Total -Kachemak Bay 88978 27413 5308 14809 495219 4325 2229 8094 646375 

Total All Sites 89261 29736 5463 25165 665398 13914 2439 16076 847452 

B. Proportion (%) 

Island Year Herring Salmonids Osmerids Gadids Sand lance Sculpins Flatfish Other 

Barren Islands 1995 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

Barren Islands 1996 0.00 0.32 0.03 0.37 99.07 0.19 0.01 0.02 

Barren Islands 1997 0.00 0.00 0.01 20.27 57.87 17.42 0.08 4.35 

Barren Islands 1998 0.00 0.18 0.33 2.18 78.13 1.42 0.01 17.76 

Barren Islands 1999 0.00 8.88 0.04 2.44 0.31 33.95 0.85 53.53 

Chisik Island 1995 0.00 6.45 12.90 67.74 0.00 6.45 0.00 6.45 

Chisik Island 1996 1.72 30.65 2.01 7.28 22.32 3.64 10.92 21.46 

Chisik Island 1997 19.08 10.23 0.26 0.00 8.24 0.78 0.87 60.54 

Chisik Island 1998 8.25 22.83 3.38 1.06 48.84 9.73 3.17 2.75 

Chisik Island 1999 0.43 77.57 0.43 0.00 0.35 8.23 0.35 12.63 

Kachemak Bay 1995 16.12 6.13 0.04 8.39 66.60 0.96 0.33 1.43 

Kachemak Bay 1996 13.84 8.29 0.02 4.28 70.88 1.81 0.30 0.59 

Kachemak Bay 1997 7.15 3.48 5.14 3.20 78.80 0.48 0.60 1.14 

Kachemak Bay 1998 22.10 1.70 0.04 1.20 73.26 0.29 0.23 1.18 

Kachemak Bay 1999 0.17 6.50 0.02 0.93 89.33 0.59 0.43 2.03 

Total -Barren Islands 0.00 0.35 0.05 5.21 86.11 4.76 0.03 3.49 

Total -Chisik Island 6.89 39.93 1.22 2.48 13.72 5.13 3.50 27.13 

Total -Kachemak Bay 13.77 4.24 0.82 2.29 76.61 0.67 0.34 1.25 

Total -All Sites 10.53 3.51 0.64 2.97 78.52 1.64 0.29 1.90 
Table 5.5. Catch-per-unit-effort (CPUE), standard error, and median catches in 

beach seine sets during June-August, 1995-1999, at the Barren Islands, Chisik 

Island and Kachemak Bay. 

Island Year Total fish No. sets CPUE Std Err Median 

Barren Islands 1995 No Data 0 No Data No Data No Data 

1996 129033 32 4032 2588 467 

1997 45821 24 1909 712 433 

1998 19533 26 751 234 97 

1999 2580 24 108 32 55 

TOTAL 196967 106 1858 805 190 

Chisik Island 1995 31 1 31 --- --- 

1996 1044 30 35 6 22 

1997 1153 18 64 27 22 

1998 473 2 1 23 5 22 

1999 1409 24 59 23 20 

TOTAL 4110 94 44 8 23 

Kachemak Bay 1995 27944 60 466 146 104 

1996 110150 202 545 162 65 

1997 100055 161 62 1 173 116 

1998 279954 149 1879 555 122 

1999 128272 99 1258 643 131 

TOTAL 646375 671 963 170 103 
Table 5.6. Frequency of occurrence of different fish species in beach seines at the Barren Islands, Chisik Island, and Kachemak 

Bay, June-August, 1995-1999. N = number of seine sets conducted. 

Species 

Pacific Herring 

Pink Salmon 

Chum Salmon 

Coho Salmon 

Sockeye Salmon 

Chinook Salmon 

Dolly Varden 

Unidentified Salmonid 

Surf Smelt 

Capelin 

Eulachon 

Longfin Smelt 

Unidentified Larval Smelt 

Unidentified Smelt 

Pacific Cod 

Pacific Tomcod 

Saffmn Cod 

Walleye Pollock 

Unidentified Juvenile Gadid 

Pacific Sandfish 

Arctic Shanny 

Pacific Snake Prickleback 

Daubed Shanny 

Slender Eelblenny 

Unidentified Lumpenus Spp. 

High Cockscomb 

Saddleback Gunnel 

Crescent Gunnel 

Unidentified Gunnel 

Sand Lance 

Prowfish 

Rock Greenling 

Kelp Greenling 

Masked Greenling 

Whitespotted Greenling 

Painted Greenling 

Unidentified Greenling 

Lingcod 

Sablefish 

Silverspotted Sculpin 

Crested Sculpin 

Tidepool Sculpin 

Eyeshade Sculpin 

Warty Sculpin 

Northern Sculpin 

Buffalo Sculpin 

Armorhead Sculpin 

Soft Sculpin 

Pacific Staghorn Sculpin 

Great Sculpin 

Padded Sculpin 

Sharpnose Sculpin 

Red lrish Lord 

Yellow lrish Lord 

Brown lrish Lord 

Roughspine Sculpin 

kibbed sculpin 

Scalvhead Scul~in 

~nideitified ~culpin 

Unidentified Larval Sculpins 

Threespine Stickleback 

Sebastes spp. 

Northern Rockfish 

Barren Islands 

1995 1996 1997 1998 1999 

N= 0 32 24 26 24 

No Data 0.0 0.0 0.0 0.0 

No Data 34.4 0.0 3.8 8.3 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 3.1 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 6.3 4.2 11.5 4.2 

No Data 6.3 0.0 3.8 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 3.8 0.0 

No Data 56.3 33.3 19.2 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 29.2 26.9 50.0 

No Data 0.0 16.7 7.7 4.2 

No Data 0.0 16.7 3.8 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 3.8 0.0 

No Data 90.6 66.7 69.2 20.8 

No Data 0.0 0.0 0.0 4.2 

No Data 3.1 4.2 3.8 0.0 

No Data 6.3 0.0 11.5 8.3 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 6.3 25.0 15.4 8.3 

No Data 18.8 33.3 30.8 25.0 

No Data 0.0 0.0 0.0 0.0 

No Data 15.6 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 43.8 4.2 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 11.5 8.3 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 79.2 50.0 100.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

No Data 0.0 0.0 0.0 0.0 

Chisik Island 

1995 1996 1997 1998 1999 

Kachemak Bay 

1995 1996 1997 1998 1999 
Table 5.6. Frequency of occurrence of different fish species in beach seines at the Barren Islands, Chisik Island, and Kachemak 

Bay, June-August, 1995-1999. N = number of seine sets conducted. 

Species Barren Islands Chisik Island Kachemak Bay 

1995 1996 1997 1998 1999 1995 1996 1997 1998 1999 1995 1996 1997 1998 1999 

N= 0 32 24 26 24 1 30 18 21 24 60 202 161 149 99 

Pipefish NoData 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.0 

Glf- el 

Kelp Clingfish (Remiwla) 

Unidentified Eelpout Spp. 

Smooth Aligatortish 

Tubenose Poacher 

Sawback Poacher 

Sturgeon Poacher 

Unidentified Poacher 

Smooth Lumpsucker 

Snailfish Spp 

Ribbon Snailfish 

Petrale Sole 

Flathead Sole 

Pacific Halibut 

Butter Sole 

Dover Sole 

Sand Sole 

Alaska Plaice 

Hybrid Sole 

Rock Sole 

Yellowfin Sole 

EnglishSole 

Starry Flounder 

Unidentified Flattish 

Unid JuvILa~al Fish 

Unidentified Fish 

Unidentified Larval Fish 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 

No Data 
Table 6.1. Relative abundance of demersal fishes captured in 

bottom trawls in Outer and lnner Kachemak Bay, 1996-1 999. 

Average CPUE, standard deviation, and the number of trawls are 

listed for forage size (8-1 5 cm) and smaller than forage size (< 8 

cm) fish. 

Fish size Year Outer Bay Inner Bay 

mean stdev n mean stdev n 

Forage 1996 13.7 8.3 4 19.7 10.0 7 

Forage 1997 19.8 17.1 12 17.9 14.1 20 

Forage 1998 10.1 9.1 17 16.1 15.322 

Forage 1999 9.5 15.9 5 35.9 33.6 8 

Forage 1996-1999 13.5 13.3 38 20.0 18.7 57 

Small 1996 18.5 20.3 4 94.5 152.7 7 

Small 1997 26.2 31.5 12 65.7 114.4 20 

Small 1998 23.1 35.9 17 35.6 39.7 22 

Small 1999 46.4 47.7 5 59.9 42.4 8 

Small 1996-1999 26.7 34.6 38 56.8 90.2 57 
Table 6.2. Seasonal variation in relative abundance of demersal fishes 

captured in Kachemak Bay, 1996-1999. Data from all stations in Kachemak 

Bay are combined. Average CPUE, standard deviation, and the number of 

trawls are listed for forage size (8-1 5 cm) and smaller than forage size (< 8 

cm) fish. Early and Late July were not sampled (ns) in 1996 or 1999. 

Fish size Year Early July Late July August 

mean stdev n mean stdev n mean stdev n 

Forage 1996 ns ns ns ns ns ns 17.5 9.5 11 

Forage 1997 12.3 7.7 10 21.9 18.3 9 21.2 16.4 13 

Forage 1998 7.8 5.4 11 10.9 8.3 14 20.6 18.0 14 

Forage 1999 ns ns ns ns ns ns 25.8 30.4 13 

Small 1996 ns ns ns ns ns ns 66.9 124.8 11 

Small 1997 17.7 21.0 10 35.0 35.4 9 87.4 137.4 13 

Small 1998 12.4 10.1 11 24.0 30.2 14 50.4 50.1 14 

Small 1999 ns ns ns ns ns ns 54.7 43.1 13 
Table 6.3. Species composition (% total number) of demersal fishes in bottom trawls, 1996-1999, and 

SCUBA transects, 1997-1998, in Kachemak Bay. Data for small (< 8 cm) and forage (8 -1 5 cm) size 

fishes are combined. Data are presented for all of Kachemak Bay (bay wide), Outer Kachemak Bay, 

and lnner Kachemak Bay. For a complete species list, see Appendices 6.2 and 6.4. 

Fish group Trawls 1996-1 999 SCUBA 1997-1 998 

Bay wide Outer Bay Inner Bay Bay wide Outer Bay Inner Bay 

Flatfish (Pleuronectidae) 41 .O% 43.3% 40.2% 9.2% 3.9% 23.6% 

Cod (Gadidae) 21 .O% 12.8% 23.8% 10.4% 8.6% 15.4% 

Sculpins (Cottidae) 14.8% 19.8% 13.0% 39.0% 50.5% 7.7% 

Pricklebacks (Stichaeidae) 7.3% 4.2% 8.3% 23.2% 28.6% 8.5% 

Ronquils (Bathymasteridae) 5.4% 4.9% 5.6% 0.9% 0.0% 3.2% 

Greenlings (Hexagrammidae) 3.7% 3.1 % 3.9% 6.3% 3.2% 14.6% 

Rockfish (Sebastes spp.) 4.0% 9.2% 2.2% 0.3% 0.2% 0.5% 

Poachers (Agonidae) 1 .O% 0.9% 1 .O% 0.6% 0.8% 0.0% 

Snailfish (Liparis spp.) 0.9% 0.3% 1.1% 0.0% 0.0% 0.0% 

Gunnels (Pholidae) 0.9% 1.4% 0.7% 9.1% 3.7% 23.9% 

Other 0.1 % 0.0% 0.1% 1.1% 0.6% 2.7% 
Table 6.4. Demersal fish abundance on SCUBA 

transects in Outer and lnner Kachemak Bay, 1997- 

1998. Average CPUE, standard deviation, and the 

number of dives are listed for both forage (8-1 5 cm) 

and smaller than forage size ( < 8 cm) fish. 

Fish size Year Outer Bay Inner Bay - - - 

mean stdev. n mean stdev. n 

Forage 1997 6.5 13.7 10 5.4 7.9 10 

Forage 1998 6.2 15.1 27 1.5 4.1 25 

Small 1997 5.6 4.5 10 3.9 7.7 10 

Small 1998 7.7 15.9 27 1.9 4.7 25 
Table 6.5. All fishes and hermit crabs counted on good SCUBA transects in 1999. Size is 

either small (< 8 cm), forage (8-15 cm), or big (> 15 cm). 

Latin name Common name Size Cohen Seldovia 

Dive 1 Dive 2 Dive 3 Dive 3 Dive 4 

Sitchaeus punctatus Arctic shannv small 1 0 0 0 0 

Sitchaeus punctatus Arctic shann; forage 

Pleuronectidae Flatfish small 

Pleuronectidae Flatfish forage 

Pleuronectidae Flatfish big 

P holidae Gunnel small 

Pholidae Gunnel forage 

Lumpenus spp. Lumpenus spp. small 

Lumpenus spp. Lumpenus spp. forage 

Lumpenus spp. Lumpenus spp. big 

Sebastes spp. Rockfish forage 

Bathymasteridae RonquilISearcher forage 

Cottidae Sculpin small 

Cottidae Sculpin forage 

Cottidae Sculpin big 

Anarrhichthys ocellatus Wolf-eel big 

Unidentified fish Unidentified fish forage 

Unidentified fish Unidentified fish big 

Hermit Crab Hermit Crab small 

Hermit Crab Hermit Crab forage 

Grand total 
Table 7.1. Total number of linear kilometers surveyed in Lower Cook Inlet 

during hydroacoustic surveys, 1995-1 999. 

Survey Survey Dates Nearshore Offshore Total Surveyed 

Year 

km km km 
Table 7.2. Number of ten-minute transects used for analysis of 

hydroacoustic surveys in Cook Inlet. 

Year Chisik Kachemak Barrens 

Total lnsh Offsh Total lnsh Offsh Total lnsh Offsh 

1995 103 * 103 124 * 124 129 * 129 

* Inshore area surveyed was too small to use in this analysis 
Table 7.3. Hydroacoustic biomass (g/m3) of forage fish in waters near Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands 

n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle 

Table 7.4. Hydroacoustic biomass (g/m3) of forage fish in surface (c30m) waters near Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands 

n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle 
Table 7.5. Hydroacoustic biomass (g/m3) of forage fish in inshore transect waters near Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands 

n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle 

Table 7.6. Hydroacoustic biomass (g/m3) of forage fish in offshore transect waters near Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands 

n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle n mean stdev stderr 90th pctle 
Table 8.1. Total number of linear and square kilometers surveyed in Lower Cook Inlet during 5 years of surveys for marine birds 

and mammals, 1995-1999. Nearshore transects followed the contours of mainland or island shorelines, while offshore transects 

cut across open water from one shore to another. The transects immediately around the Barren Islands were considered offshore. 

Survey Survey Dates Transect Width Nearshore Offshore Total Surveyed 

Year 

m km km2 km km2 km km2 

1996 14-31 July 200 nearshore 561 126 1491 447 2052 574 

300 offshore 
Table 8.2. Species composition and numbers of seabirds and marine mammals observed during 5 years of surveys in Lower Cook Inlet during July and August, 1995-1999 

All Loons Gavia spp. total 

Common Loon Gavia immer 

Yellow-billed Loon Gavia adamsii 

Pacific Loon Gavia pacifica 

Red-throated Loon Gavia stellata 

Red-necked Grebe Podiceps grisegena 

Horned Grebe Podiceps auritus 

Laysan Albatross' Phoebastria immutabilis 1 cO.1 1 40.1 

Northern Fulmar Fulmarus glacialis 2151 13.2 429 0.6 157 0.9 72 0.5 261 1.4 3070 2.3 

All Shearwaters Puffinus spp. total 3155 19.4 45550 67.5 4823 27.3 3733 23.4 8015 44.4 65276 48.2 

Sooty Shearwater Pufrinus griseus 9 0.1 1 ~0.1 70 0.4 1377 8.6 209 1.2 1666 1.2 

Short-tailed Shearwater Puffinus tenuirostris 80 0.5 189 0.3 2 ~0.1 10 0.1 4 ~0.1 285 0.2 

Bullets Shearwater Puffinus bulleri 1 ~0.1 1 ~0.1 

Fork-tailed Storm-Petrel Oceanodroma furcata 748 4.6 2172 3.2 357 2.0 49 0.3 265 1.5 359 1 2.7 

Leach's Storm-Petrel Oceanodroma leucorhoa 2 ~0.1 2 co.1 

All Cormorants Phalacrocorax spp. total 34 0.2 72 0.1 112 0.6 56 0.4 41 0.2 315 0.2 

Pelagic Cormorant Phalacrocorax pelagicus 33 0.2 42 0.1 53 0.3 40 0.3 24 0.1 192 0.1 

Red-faced Cormorant Phalacrocorax urile 1 ~0.1 12 ~0.1 3 ~0.1 9 0.1 4 ~0.1 29 ~0.1 

Doublecrested Cormorant Phalacrocorax auritus 1 ~0.1 11 0.1 1 ~0.1 8 ~0.1 2 1 40.1 

Red-breasted Merganser Mergus serrator 6 ~0.1 6 ~0.1 

Unidentified Merganser Mergus spp. 1 ~0.1 1 ~0.1 

White-winged Swter Melanitta fusca 6 ~0.1 40 0.1 22 0.1 8 0.1 225 1.2 301 0.2 

Surf Swter Melanitta perspicillata 63 0.1 5 40.1 56 0.4 25 0.1 149 0.1 

Harlequin Duck Histrionicus histrionicus 3 ~0.1 5 ~0.1 7 ~0.1 13 0.1 28 ~0.1 
Table 8.2. (cont'd) Species composition and numbers of seabirds and marine mammals observed during 5 years of surveys in Lower Cook Inlet during July and August, 1995-1999. 

Species Scientific Name 1995 1996 1997 1998 1999 Total 

Number %Total Number %Total Number %Total Number %Total Number %Total Number %Total 

All Phalaropes Phalaropus spp. 409 2.5 2545 3.8 371 2.1 647 4.1 138 0.8 4110 3.0 

Red-necked Phalarope Phalaropus lobatus 278 1.7 2483 3.7 176 1.0 562 3.5 127 0.7 3626 2.7 

Red Phalarope Phalaropus fulicaria 34 0.2 1 ~0.1 1 ~0.1 36 ~0.1 

All Jaegars Stercorarius spp. 46 0.3 11 ~0.1 2 co.1 5 ~0.1 11 0.1 75 0.1 

Pomarine Jaeger Stercorarius pomarinus 31 0.2 5 ~0.1 1 ~0.1 2 ~0.1 7 ~0.1 46 ~0.1 

Parasitic Jaeger Stercorarius parasiticus 8 ~0.1 5 ~0.1 1 co.1 2 ~0.1 16 ~0.1 

Long-tailed Jaeger Stercorarius longicaudus 7 ~0.1 1 ~0.1 1 co.1 9 ~0.1 

All Gulls Laridae 

Mew Gull Lams canus 

Glaucous-winged Gull Larus glaucescens 

Herring Gull Larus argentatus 

Bonaparte's Gull Larus philadelphia 

Black-legged Kittiwake Rissa tridactyla 

Sabine's Gull Xema sabini 

All Terns Sterna spp. 188 1.2 169 0.3 484 2.7 133 0.8 393 2.2 1367 1 .O 

Arctic Tern Sterna paradisaea 63 0.4 135 0.2 468 2.6 108 0.7 276 1.5 1050 0.8 

Aleutian Tern Sterna aleutica 119 0.7 28 ~0.1 5 ~0.1 1 ~0.1 23 0.1 176 0.1 

All Alcids Alcidae 5815 35.8 12367 18.3 8864 50.1 7978 50.0 6995 38.8 42019 31 .O 

All Murres Uria spp. 1204 7.4 2955 4.4 2455 13.9 2207 13.8 2016 11.2 10837 8.0 

Common Murre Uria aalge 1201 7.4 2916 4.3 2455 13.9 2193 13.7 2012 11.2 10777 8.0 

Thick-billed Murre Uria lomvia 3 ~0.1 22 eO.1 1 ~0.1 2 ~0.1 28 ~0.1 

Pigeon Guillemot Cepphus columba 90 0.6 360 0.5 341 1.9 373 2.3 321 1.8 1485 1 .I 

All Brachyramphus Brachyramphus spp. 472 2.9 1571 2.3 2336 13.2 2380 14.9 1661 9.2 8420 6.2 

Marbled Murrelet Brachyramphus marmoratus 371 2.3 904 1.3 1585 9.0 1844 11.6 1357 7.5 6061 4.5 

Kiltlitz's Murrelet Brachyramphus brevirostris 6 cO.1 114 0.2 122 0.7 208 1.3 56 0.3 506 0.4 

Andent Mumlet Synthliboramphus antiquus 31 0.2 615 0.9 53 0.3 17 0.1 17 0.1 733 0.5 

Cassin's Auklet Piychoramphus aleuticus 1 ~0.1 4 ~0.1 1 ~0.1 6 ~0.1 

Parakeet Auklet Aethia psittacula 39 0.2 114 0.2 11 0.1 15 0.1 51 0.3 230 0.2 

Rhinoceros Auklet Cerorhinca monocerata 10 0.1 12 ~0.1 14 0.1 25 0.2 4 40.1 65 ~0.1 

Tufted Puffin Fratercula cirrhata 3489 21.5 6254 9.3 3349 18.9 2681 16.8 2675 14.8 18448 13.6 

Horned Puffin Fratercula comiculata 476 2.9 485 0.7 298 1.7 279 1.7 248 1.4 1786 1.3 

Least Au Wet Aethia pusilla 1 ~0.1 1 ~0.1 
Table 8.2. (cont'd) Species composition and numbers of seabirds and marine mammals observed during 5 years of surveys in Lower Cook Inlet during July and August, 1995-1999. 

Species Scientific Name 1995 1996 1997 1998 1999 Total 

Number %Total Number %Total Number %Total Number %Total Number %Total Number %Total 

All marine mammals total' 27 21 9 97 123 365 831 

Sea Otter 

Northern Fur Seal 

Steller's Sea Lion 

Harbor Seal 

Harbor Porpoise 

Dall's Porpoise 

Killer Whale 

Humpback Whale 

Fin Whale 

Minke Whale 

Unidentified baleen whale 

Enhydra lutris 

Callorhinus ursinus 

Eumetopias jubatus 

Phoca vitulina 

Phocoenaphocoena 

Phocoenoides dalli 

Orcinus orca 

Megaptera novaeangliae 

Balaenoptera physalus 

Balaenoptera acutorostrata 

Balaenoptera spp. 

*All birds were observed within transed boundaries (see Table 8.1 for transed widths) except for the Laysan Albatross, which was off-transed. Marine mammal observations 

include all sighted marine mammals, regardless of distance from the survey vessel. 
Table 8.3. Number observed (N) and density (D) per kilometer squared of predominant marine bird species and speaes groups by study area in Lower Cook 

Inlet, 1995-1999. In 1996-1999, Chisik, Kachemak, and the Barrens surveys covered comparable areas with similar (1996) or identical (1997-1999) transect layouts (Figures 

7.2-7.3). In 1995, transects covered a smaller portion of each study area and included minimal nearshore habitat (Table 8.1, Fig. 7.1). 

Species 1995 1996 1997 1998 1999 

Chisik Kach Barrens Chisik Kach Barrens Central Shuvak Chisik Kach Barrens Chisik Kach Barrens Chisik Kach Barrens 

All marine birds N 2661 3400 10180 2098 4892 18273 3746 38452 1131 7723 8829 1764 6952 7248 925 3804 13312 

D 34.36 53.03 116.47 20.42 39.16 165.94 31.92 324.77 11.37 58.92 86.17 16.63 53.12 70.94 8.65 28.76 130.76 

All Shearwaters N 518 1401 1236 565 496 10090 1897 32502 308 2341 2174 577 1533 1623 98 1090 6826 

D 6.69 21.85 14.14 5.50 3.97 91.63 16.17 274.51 3.10 17.86 21.22 5.44 11.71 15.89 0.92 8.24 67.05 

All Cormorants N 11 0 23 0 26 41 0 5 0 36 70 0 25 31 1 14 26 

D 0.14 0.00 0.26 0 0.21 0.37 0 0.04 0 0.27 0.68 0 0.19 0.30 0.01 0.11 0.26 

Black-legged N 805 807 1396 383 1393 1265 42 74 167 987 937 356 1476 1109 252 280 805 

Kittiwake D 10.39 12.59 15.97 3.73 11.15 11.49 0.36 0.63 1.68 7.53 9.14 3.36 11.28 10.85 2.36 2.12 7.91 

Glaucous-winged N 317 36 321 28 352 282 37 84 60 129 170 79 50 121 33 78 196 

Gull D 4.09 0.56 3.67 0.27 2.82 2.56 0.32 0.71 0.60 0.98 1.66 0.74 0.38 1.18 0.31 0.59 1.93 

All Murres N 409 280 515 190 860 813 272 819 154 972 1329 250 1001 956 157 400 1459 

D 5.28 4.37 5.89 1.85 6.88 7.38 2.32 6.92 1.55 7.42 12.97 2.36 7.65 9.36 1.47 3.02 14.33 

Pigeon Guillemot N 0 25 65 1 209 142 0 8 3 193 145 0 194 179 0 150 171 

D 0.00 0.39 0.74 0.01 1.67 1.29 0 0.07 0.03 1.47 1.42 0 1.48 1.75 0 1.13 1.68 

Marbled Murreletl N 67 285 114 198 428 361 266 204 262 1650 302 257 1443 472 157 986 462 

Brachyramphus D 0.87 4.45 1.30 1.93 3.43 3.28 2.27 1.72 2.63 12.59 2.95 2.42 11.03 4.62 1.47 7.46 4.54 

Kifflitz's Murrelet N 2 3 1 23 47 15 21 8 2 117 3 22 185 1 4 32 20 

D 0.03 0.05 0.01 0.22 0.38 0.14 0.18 0.07 0.02 0.89 0.03 0.21 1.41 0.01 0.04 0.24 0.20 

Tufted Puffin N 30 20 3439 124 212 4402 198 1318 7 444 2898 19 274 2388 15 122 2538 

D 0.39 0.31 39.35 1.21 1.70 39.98 1.69 11.13 0.07 3.39 28.28 0.18 2.09 23.37 0.14 0.92 24.93 

Horned Puffin N 386 38 53 241 125 90 12 17 98 99 101 165 23 91 153 17 78 

D 4.98 0.59 0.61 2.35 1.00 0.82 0.10 0.14 0.99 0.76 0.99 1.56 0.18 0.89 1.43 0.13 0.77 
Table 9.1. Numbers of Common Murres in population plots at Chisik Island (includes Duck Island), 1995 - 1999. Of the original 7 plots (1 - 7) 

historically monitored by AMNWR personnel, Common Murres were present in plots 4 & 7 only from 1995 - 1999, therefore totals from plots 4 & 7 are 

comparable to plots 1- 7 from the historical data. Additional population plots for Common Murres were established in 1997. Plot 9 is a Chisik Island 

plot that was created in 1997 and Duck Island plots are productivity plots that were counted starting in 1997. 

Year Plot 7 Plots 4 & 7 Plot 9 Duck Island plots 

n mean stdev n mean stdev n mean stdev n mean stdev 

1995 5 64 11.80 1 * 169 - 

1996 4 9 1 17.15 4 153 11.95 

1997 7 76 36.34 7 138 45.23 8 60 34.1 8 8 219 13.02 

1998 3 0 0.00 3 69 7.00 3 0 0 2 249 31.82 

1999 5 67 12.74 5 187 57.81 5 88 14.83 3 227 27.07 

* There was only 1 count for plot 4 in 1995 and it was added to the counts for plot 7 to generate a mean for plots 4 & 7, therefore there is not a 

standard deviation for this count. 
Table 9.2. Numbers of Common Murres in population plots at Gull Island, 1995-1999. 

Year - Plots 1-3 Plots 1-8 Plots 1-1 0 

n mean stdev n mean stdev n mean stdev 

Table 9.3. Numbers of Common Murres in population plots at the Barren Islands*, 1995-1999. 

Year Plots 1-8 

n mean stdev 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 9.4. Common Murre hatching success (chicks hatched per egg laid) at Chisik, Gull and Barren 

Islands, 1995-1 999. 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 4 0.39 0.43 10 0.84 0.08 

1996 8 0.81 0.13 12 0.84 0.21 10 0.84 0.09 

1997 11 0.77 0.14 12 0.81 0.13 10 0.90 0.09 

1998 11 0.52 0.32 5 0.84 0.11 10 0.72 0.24 

1999 8 0.83 0.15 5 0.52 0.17 10 0.86 0.09 

All 8 0.66 0.20 9 0.75 0.16 10 0.83 0.07 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 

Table 9.5. Common Murre fledging success (chicks fledged per chick hatched) at Chisik, Gull and 

Barren Islands, 1995-1 999. 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 10 0.88 0.06 

1996 8 0.92 0.08 12 0.69 0.34 10 0.88 0.08 

1997 11 0.87 0.10 12 0.64 0.34 10 0.92 0.07 

1998 11 0.21 0.32 5 0.78 0.05 10 0.71 0.35 

1999 8 0.70 0.34 5 0.45 0.35 10 0.84 0.09 

All 10 0.68 0.32 9 0.64 0.14 10 0.85 0.08 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 9.6. Common Murre breeding success (chicks fledged per egg laid) at Chisik, Gull and 

Barren Islands, 1995-1 999. 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 5 0.61 0.18 10 0.74 0.1 1 

1996 8 0.74 0.12 12 0.64 0.35 10 0.74 0.1 1 

1997 11 0.67 0.16 12 0.53 0.29 10 0.82 0.09 

1998 11 0.18 0.30 5 0.65 0.07 10 0.58 0.30 

1999 8 0.63 0.34 5 0.28 0.29 10 0.75 0.12 

All 10 0.56 0.25 8 0.54 0.15 10 0.73 0.09 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 

Table 9.7. Timing of Common Murre egg laying at Chisik, Gull and Barren Islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 4 20-JuI 11.52 10 7-JuI 2.81 

1996 8 10-Jul 2.66 11 12-Jul 5.55 10 3-Jul 4.65 

1997 11 6-Jul 3.62 12 10-Jul 4.92 10 I-Jul 1.17 

1998 11 26-JuI 6.81 5 9-JuI 2.80 10 8-JuI 2.37 

1999 8 16-JuI 6.34 5 13-JuI 7.03 10 3-JuI 4.98 

All 8 15-Jul 7.92 8 I I-Jul 1.83 10 4-Jul 2.97 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 

Table 9.8. Timing of Common Murre hatching at Chisik, Gull and Barren Islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 2 I I-Aug 1.77 10 7-Aug 2.04 

1996 8 9-Aug 2.29 10 13-Aug 5.22 10 4-Aug 4.57 

1997 11 7-Aug 5.09 12 9-Aug 4.63 10 2-Aug 1.42 

1998 10 25-Aug 6.44 5 10-Aug 3.15 6 6-Aug 2.64 

1999 8 16-Aug 6.17 5 12-Aug 11.63 10 3Aug 5.01 

All 8 13-Aug 7.20 8 11-Aug 1.83 9 4-Aug 2.07 

* Data from: Kettle, A,, D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 9.9. Summary of Common Murre chick diet composition (% number) at Chisik, Gull and Barren Island, 1995-1999. 

Prey Chisik Island Gull Island Barren Islands* 

1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 

No. meals n.d. 553 783 203 307 1846 35 132 326 552 130 1175 389 236 421 408 186 1640 

Osmerids 48.8 46.7 47.8 53.1 49.1 5.7 20.5 30.4 37.0 56.2 29.9 79.9 90.7 91.2 93.4 91.4 87.3 

Sand lance 21.2 11.9 27.6 35.5 24.0 60.0 12.9 29.1 20.1 23.8 29.2 0.8 2.1 4.3 2.0 2.2 2.4 

Gadids 5.2 0.9 0.0 0.0 1.5 5.7 22.7 13.8 4.2 0.0 9.3 6.9 2.5 1.2 1.7 1.1 3.6 

Other 17.4 13.8 23.2 10.7 16.3 22.9 11.4 13.8 32.1 17.7 19.6 6.4 0.4 0.2 2.0 2.2 2.4 

Unidentified 7.4 26.7 1.5 0.7 9.1 5.7 32.6 12.9 6.7 2.3 12.0 5.9 4.2 3.1 1.0 3.2 4.4 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon Valdez Oil Spill Restoration Project Final Report 

(Restoration Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 9.10. Summary of adult Common Murre diet composition (%mass) at Chisik, Gull and Barren Islands, 1995-1999. 

Prey Chisik Island Gull Island Barren Islands* 

1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 

No. stomachs 13 10 10 8 10 51 11 16 8 10 10 55 10 9 10 10 5 44 

Total biomass (g) 186 342 360 164 364 1416 965 1351 331 103 484 3234 52 231 73 263 295 913 

Mean glstomach 14 34 36 21 36 25 88 84 47 10 48 47 5 26 7 26 59 22 

Osmerids 0.3 35.5 0.5 0.0 55.8 18.4 0.0 0.3 0.6 62.1 7.3 14.1 34.6 26.0 35.7 92.0 13.4 40.3 

Sand lance 37.6 34.8 66.5 86.6 36.5 52.4 95.8 98.4 62.9 13.7 89.9 72.1 0.0 2.8 0.8 0.0 72.8 15.3 

Gadids 39.3 10.6 14.6 0.0 0.6 13.0 4.2 1.3 32.8 0.0 1.0 7.9 65.4 59.8 59.3 0.0 10.4 39.0 

Other 0.3 19.1 18.4 13.4 4.3 11.1 0.0 0.1 3.7 24.2 1.7 5.9 0.0 11.4 4.3 8.0 0.0 4.7 

Unidentified 22.5 0.1 0.0 0.1 2.7 5.1 0.0 0.0 0.0 0.1 0.2 0.1 0.0 0.0 0.0 0.0 3.4 0.7 

* Data from: Kettle, A,, D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon Valdez Oil Spill Restoration Project Final Report 

(Restoration Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 9.1 1. Common Murre attendance expressed as "bird-minutes" or the combined minutes both parents spent at the nest 

site per hour during incubation at Chisik, Gull, and Barren Islands, 1995-1999 (n = nest sites) . 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren lslands seabird studies, 2000, Exxon Valdez Oil Spill 

Restoration Project Final Report (Restoration Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 

Table 9.12. Common Murre attendance expressed as "bird-minutes" or the combined minutes both parents spent at the nest 

site per hour during chick-rearing at Chisik, Gull, and Barren Islands, 1995-1999 (n = nest sites) . 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 7 63.09 2.17 9 70.82 6.04 12 65.79 4.41 

1996 22 60.34 4.14 12 64.65 2.22 10 69.03 4.64 

1997 19 64.93 3.32 7 73.50 6.56 9 73.25 6.41 

1998 9 59.93 4.72 14 75.47 9.62 9 69.20 4.08 

1999 12 62.84 5.23 11 66.59 4.16 9 75.54 4.10 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon Valdez Oil Spill 

Restoration Project Final Report (Restoration Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 
Table 9.13. Common Murre chick-feeding rates (feeds per hour) at Chisik, Gull, and Barren Islands, 1995-1999 (n = nest 

sites) . 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

1995 7 0.28 0.07 9 0.32 0.12 12 0.29 0.1 1 

1996 22 0.19 0.06 12 0.36 0.1 1 10 0.26 0.04 

1997 19 0.25 0.09 7 0.30 0.13 9 0.25 0.07 

1998 9 0.16 0.05 14 0.24 0.09 9 0.25 0.05 

1999 12 0.26 0.06 11 0.27 0.12 9 0.23 0.03 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon Valdez Oil Spill 

Restoration Project Final Report (Restoration Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 

Table 9.14. Common Murre foraging trip durations (minutes) when chick provisioning (resulted in chick feeding) at Chisik, Gull, 

and Barren Islands, 1995-1 999 (n = nest sites). 

Year Chisik Island Gull Island Barren Islands* 

n mean stdev n mean stdev n mean stdev 

* Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon Valdez Oil Spill 

Restoration Project Final Report (Restoration Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 
Table 9.15. Pooled growth rate* (g Imm wing growth) of Common Murre 

chicks at Chisik and Gull Islands, 1995-1999. 

Year Chisik Island 

n slope stdev 

1995 3 1 5.68 4.42 

1996 45 7.83 3.76 

1997 32 8.26 5.00 

1998 n.d. n.d. n.d. 

1999 24 6.31 2.38 

Gull Island 

n slope stdev 

15 6.11 3.59 

24 9.30 2.70 

3 n.d. n.d. 

n.d. n.d. n.d. 

n.d. n.d. n.d. 

All 4 7.02 1.22 2 7.71 0.63 

*Slope of linear regression of mass on wing length for chicks with wings 

>= 25mm and <= 45 mm (linear growth phase). N represents number of 

chicks; each chick was measured once, thus growth rates shown here are 

composites per colony-year. 
Table 9.16. Size, condition, and estimated age of common murre fledglings at Chisik Island, 1997-1999, summarised by capture bout date. 

Year Headbill (mm) Tarsus (mm) Wing (mm) Mass (g) Winglmass Estimated age (d)* 

bout date n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

1997 Total 0 0 123 72.0 7.06 123 229.3 28.81 123 3.19 0.32 123 20.9 2.74 

1998 29-Au~ 0 0 2 77.5 4.95 2 205.0 28.28 2 2.64 0.20 2 23.1 1.92 

3-Sep 0 0 9 68.0 9.87 9 198.2 34.57 9 2.92 0.34 9 19.4 3.83 

4-Sep 0 0 9 69.4 9.08 9 198.7 35.01 9 2.86 0.29 9 19.9 3.52 

1998 Total 0 0 20 69.6 9.21 20 199.1 32.64 20 2.86 0.30 20 20.0 3.57 

1999 27-Au~ 2 66.5 0.49 2 35.3 0.42 2 77.5 0.71 2 237.5 24.75 2 3.07 0.35 2 23.1 0.27 

28-Aug 4 64.5 4.21 4 35.0 2.58 4 72.0 9.56 4 211.0 34.55 4 2.92 0.13 4 20.9 3.71 

30-Au~ 2 65.6 1.27 2 34.3 0.49 2 74.5 2.12 2 220.0 14.14 2 2.95 0.11 2 21.9 0.82 

31-Aug 6 66.2 3.09 6 34.6 0.97 6 73.0 7.10 6 224.8 19.15 6 3.10 0.34 6 21.3 2.75 

4-Sep 5 62.9 2.76 5 34.1 0.36 8 76.1 6.64 8 215.4 30.16 8 2.83 0.32 8 22.5 2.58 

6-Sep 4 62.6 3.80 4 32.2 1.62 21 70.4 8.11 21 203.0 32.93 21 2.88 0.29 21 20.3 3.15 

7-Sep 0 0 28 69.7 9.65 28 203.4 32.30 28 2.92 0.21 28 20.0 3.75 

8-Sep 0 0 17 65.7 7.74 17 198.5 30.55 17 3.03 0.31 17 18.5 3.00 

11-Sep 0 0 4 66.3 9.18 4 211.8 49.61 4 3.16 0.35 4 18.7 3.56 

1999Total 23 64.5 3.25 23 34.2 1.59 92 70.1 8.63 92 206.6 31.71 92 2.95 0.28 92 20.2 3.35 

GrandTotal 23 64.5 3.25 23 34.2 1.59 235 71.0 7.92 235 217.9 32.54 235 3.07 0.33 235 20.6 3.07 

* age is estimated by regression from wing length, using relationship [age(d) = -7.01 + 0.388*wing(mm)] from known-age chicks (see Methods). 
Table 9.17. Size, condition, and estimated age of common murre fledglings at Gull Island, 1997-1999, summarized by capture bout date. 

Year Headbill (mm) Tarsus (mm) Wing (mm) Mass (g) Winglmass Estimated age (d)* 

bout date n mean stdev n nean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

1997 28-Au~ 0 

29-Au~ 0 

1997 Total 0 

1998 10-Sep 0 

12-Sep 0 

13-Sep 0 

1998 Total 0 

1999 11-Sep 7 65.1 1.92 7 34.4 1.66 22 70.6 7.46 19 237.2 23.93 19 3.30 0.32 22 20.4 2.89 

13-Sep 3 63.9 3.21 3 34.0 1.90 41 66.3 8.23 40 214.3 21.61 40 3.25 0.29 41 18.7 3.19 

1999 Total 10 64.7 2.26 10 34.3 1.64 63 67.8 8.18 59 221.7 24.65 59 3.27 0.30 63 19.3 3.17 

Grand Total 10 64.7 2.26 10 34.3 1.64 163 70.0 9.14 157 222.9 30.54 157 3.18 0.29 163 20.1 3.55 

* age is estimated by regression from wing length, using relationship [age(d) = -7.01 + 0.388*wing(mm)] from known-age chicks 

(see Methods). 
Table 9.18. Size and condition of Common Murre fledglings at the Barren Islands* 

1996 - 1999, summarized by capture bout date. 

Year Wing (mm) Mass (g) Winglmass 

bout date n mean stdev n mean stdev n mean stdev 

1996 26-Aug 18 74.27 4.25 18 235.94 22.37 18 3.18 0.23 

27-Au~ 14 79.43 4.13 14 251.77 23.20 14 3.17 0.88 

31-Au~ 13 77.62 6.53 13 237.85 26.23 13 3.06 0.27 

3-Sep 2 68.00 2.83 2 216.00 19.80 2 3.18 0.16 

1996 Total 47 74.83 5.03 47 235.4 14.73 47 3.15 0.06 

1997 19-Au~ 13 72.23 13.89 13 246.92 30.87 13 3.42 1.52 

20-Au~ 7 74.57 4.50 7 238.57 13.59 7 3.20 0.10 

24-Au~ 43 79.05 5.86 43 254.53 20.64 43 3.22 0.30 

26-Aug 17 78.47 5.27 17 254.29 17.78 17 3.24 0.35 

28-Aug 16 77.69 3.20 16 256.13 20.03 16 3.30 0.22 

1997 Total 96 76.40 2.90 96 250.1 7.36 96 3.28 0.09 

1998 Total 3 85.33 - 3 269.00 - 3 3.15 - 

1999 ~otal 77 78.41 1.84 77 249.0 9.79 77 3.18 0.12 

Grand Total 223 77.56 3.99 223 247.1 12.93 223 3.17 0.10 

*Data from: Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon 

Valdez Oil Spill Restoration Project Final Report (Restoration Project 00163J), U.S. Fish and Wildlife 

Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 9.19. Common Murre fledging age (days) at Chisik and Gull Islands, 1995 

- 1999 (n = fledglings). 

Year Chisik Island Gull Island 

n mean stdev n mean stdev 

All 6 1 20.59 1.02 41 19.91 0.90 
Table 9.20. Common murre adult size and condition, Chisik Island 1997-1999, summarized by capture bout date. 

Year Culmen (mm) Headbill (mm) Tarsus (mm) Wing (mm) Mass (g) Masslwing 

bout date n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

1997 12-Jun 4 45.8 1.01 0 4 41.1 1.87 4 213.0 4.76 4 1048.8 67.00 4 4.92 0.25 

24-Jun 10 47.4 2.00 0 10 39.5 1.46 10 218.0 3.56 10 1064.5 76.72 10 4.88 0.35 

31-JuI 96 46.7 2.20 96 116.2 2.97 96 39.6 1.56 96 218.1 4.71 96 1081.3 67.07 96 4.96 0.29 

10-Aug 9 46.8 2.28 9 116.9 4.06 9 40.8 1.22 9 223.3 3.74 9 1043.6 31.69 9 4.67 0.11 

17-Aug 27 47.1 2.31 15 117.0 3.30 27 40.7 1.95 27 216.8 5.94 27 1017.1 81.23 27 4.69 0.36 

1997 Total 146 46.8 2.18 120 116.3 3.09 146 39.9 1.69 146 218.1 5.06 146 1065.1 72.69 146 4.88 0.32 

1998 28-Jun 4 49.5 1.42 4 118.3 2.10 4 40.6 0.61 4 223.3 3.30 4 1060.0 21.60 4 4.75 0.14 

12-JuI 5 47.0 3.04 5 116.4 2.43 5 40.9 1.12 5 223.0 4.64 5 998.0 43.24 5 4.48 0.19 

23-JuI 11 45.8 2.36 11 115.7 3.65 11 40.6 1.20 11 221.5 6.83 11 1044.5 64.82 11 4.72 0.28 

13-Aug 15 45.7 2.38 15 115.7 3.70 15 40.6 1.21 15 222.9 3.99 15 1055.7 56.50 15 4.74 0.25 

31-Au~ 21 46.9 2.41 21 115.0 3.29 21 39.5 1.76 21 219.0 5.32 21 959.0 46.17 21 4.38 0.21 

1998 Total 56 46.5 2.52 56 115.7 3.34 56 40.2 1.48 56 221.2 5.33 56 1012.4 67.09 56 4.58 0.28 

1999 29-Jun 10 46.8 2.19 10 116.0 2.59 10 40.3 1.16 10 224.6 3.66 10 1030.8 58.38 10 4.59 0.22 

6-JuI 24 46.9 2.22 24 116.1 3.32 24 40.8 1.19 24 220.5 3.87 24 1026.9 59.91 24 4.66 0.25 

13-JuI 10 46.7 2.90 10 115.9 3.26 10 41.3 1.00 10 224.7 5.27 10 1037.0 92.95 10 4.61 0.38 

19-JuI 12 46.5 1.91 12 117.2 3.31 12 39.8 1.18 12 216.4 5.53 12 1031.7 69.59 12 4.77 0.28 

26-JuI 5 46.8 1.85 5 116.6 1.07 5 38.1 1.48 5 219.6 5.86 5 1062.0 27.97 5 4.84 0.13 

12-Aug 7 47.4 0.81 7117.4 3.17 7 40.2 1.76 7222.9 3.80 7 1090.395.48 7 4.89 0.40 

28-Aug 6 47.7 2.88 6 116.8 3.12 6 41.4 1.01 6 222.5 4.28 6 1010.8 70.95 6 4.54 0.25 

1999 Total 74 46.9 2.15 74 116.5 3.01 74 40.4 1.44 74 221.3 5.14 74 1036.6 69.98 74 4.68 0.29 

GrandTotal 276 46.8 2.24 250 116.2 3.13 276 40.1 1.60 276 219.6 5.36 276 1046.8 73.70 276 4.77 0.33 
Table 9.21. Common murre adult size and condition, Gull Island 1997-1999, summarized by capture bout date. 

Year Culmen length (mm) Headbill length (mm) Tarsus length (mm) Wing length (mm) Mass (g) Masshing 

bout date n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

1997 20-Jun 11 47.6 2.31 0 11 40.0 1.56 11 220.8 4.58 11 1018.2 126.00 11 4.61 0.59 

30-JuI 14 47.4 2.54 12 115.0 3.02 14 40.4 1.51 14 215.3 4.12 14 1008.6 51.19 14 4.68 0.22 

8-Aug 25 45.3 2.40 0 25 41.4 1.36 25 218.8 5.04 25 988.4 52.76 25 4.52 0.24 

26-Aug 28 47.2 2.72 19 116.9 4.07 28 40.3 1.78 28 215.5 6.26 281005.9 67.95 28 4.67 0.37 

1997 Total 78 46.7 2.67 31 116.1 3.76 78 40.6 1.63 78 217.3 5.62 78 1002.5 71.42 78 4.62 0.35 

1998 4-Jun 18 47.6 3.39 18 118.3 3.64 18 40.3 1.61 18 218.4 5.25 18 1032.8 45.40 18 4.73 0.19 

14-Jun 6 48.2 2.04 6 116.4 3.97 6 40.0 1.76 6 215.5 6.28 6 1046.3 116.81 6 4.85 0.46 

21-Jun 5 49.8 2.20 5 119.0 2.52 5 39.1 0.88 5 218.6 4.34 51041.2 55.68 5 4.77 0.29 

10-JuI 14 46.5 4.13 14 116.2 2.73 14 40.1 3.43 14 216.8 5.38 14 1057.1 74.89 14 4.88 0.33 

23-JuI 6 47.5 2.56 6 115.9 4.42 6 40.6 0.97 6 215.5 4.72 6 1100.5 58.90 6 5.11 0.28 

I-Au~ 23 47.0 2.1 1 23 116.4 3.28 23 39.7 1.84 23 214.7 4.1 1 23 1085.9 55.55 23 5.06 0.27 

12-Au~ 10 47.2 3.55 10117.6 4.57 10 41.1 1.77 10 213.9 3.45 101101.7 92.87 10 5.15 0.38 

19-Aug 10 46.2 2.52 10 115.0 3.57 10 39.4 1.54 10 212.8 3.88 10 1036.4 66.86 10 4.87 0.31 

27-Au~ 10 46.7 1.88 10 116.7 2.40 10 39.5 1.19 10 213.5 5.21 10 1009.8 51.71 10 4.73 0.26 

6-Sep 10 47.5 2.27 10 116.8 3.14 10 38.7 2.26 10 213.9 7.55 10 962.1 81.57 10 4.49 0.29 

1998 Total 112 47.2 2.85 112 116.8 3.45 112 39.9 2.00 112 215.4 5.20 112 1049.6 76.46 112 4.87 0.34 

1999 12-Jun 15 47.3 1.85 15 118.0 2.91 15 41.4 1.10 15 213.7 3.56 15 1062.5 67.46 15 4.97 0.27 

24-Jun 10 49.2 1.74 10 116.6 3.17 10 40.4 1.27 10 218.2 6.60 10 1011.4 74.79 10 4.63 0.28 

7-JuI 7 47.0 2.27 7 116.7 3.69 7 39.7 1.72 7 215.7 3.73 7 1085.7 84.75 7 5.03 0.35 

19-JuI 7 47.3 1.62 7 116.7 2.37 7 40.7 1.26 7 215.3 3.45 71088.1 140.25 7 5.05 0.63 

3-Au~ 10 47.1 2.03 10 115.4 3.83 10 40.1 1.24 10 217.7 7.02 10 1101.1 56.38 10 5.06 0.22 

16-Aug 9 46.6 2.48 9115.1 3.37 9 40.6 1.20 9213.0 5.17 9 963.8 70.81 9 4.53 0.33 

23-Aug 10 47.9 2.15 10 116.4 3.36 10 40.8 1.34 10 213.1 6.15 10 1004.5 45.09 10 4.72 0.25 

1999 Total 68 47.5 2.09 68 116.5 3.27 68 40.6 1.33 68 215.1 5.46 68 1044.1 87.24 68 4.85 0.38 

Grand Total 258 47.1 2.62 211 116.6 3.43 258 40.3 1.77 258 215.9 5.46 258 1033.9 80.44 258 4.79 0.37 
Table 9.22. Baseline concentrations of corticosterone (nglml) in Common 

Murres at Gull and Chisik Islands, 1997-1999. 

Year Breeding stage Gull Island Chisik lsland 

n mean stdev n mean stdev 

1997 Pre-egg-laying 11 7.55 4.72 14 6.20 2.87 

Incubation 12 6.20 3.16 12 7.71 2.76 

Early chick-rearing 8 10.20 2.49 11 11.69 5.36 

Late chick-rearing 12 34.77 19.89 6 25.78 3.29 

Total 43 15.26 16.28 43 10.76 7.40 

1998 Pre-egg-laying 28 6.56 5.30 5 19.45 9.77 

Incubation 47 6.80 8.34 31 19.41 9.66 

Early chick-rearing 15 4.22 1.81 11 19.69 9.68 

Late chick-rearing 20 9.59 8.98 15 19.56 6.69 

Total 110 6.90 7.29 62 19.50 8.82 

1999 Pre-egg-laying 21 9.61 9.33 21 7.31 7.44 

Incubation 29 9.47 9.14 30 13.65 10.45 

Early chick-rearing 11 3.96 2.45 23 9.86 10.81 

Late chick-rearing 10 7.99 15.79 8 3.72 1.36 

Total 71 8.45 9.76 82 10.00 9.77 
Table 10.1. Number of adult Black-legged Kittiwakes counted in plots from middle incubation to the start of fledging at 

Chisik (plots 1-7), Gull (plots 1-10) and Barren islands (plots 1-4), 1995-1999. 

Year Chisik Island Gull Island Barren Island* 

n mean stdev n mean stdev n mean stdev 

* Data from : Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, Exxon Valdez Oil 

Spill Restoration Project Final Report (Reostoration Project 00163J), U.S. Fish and Wildlife Service, Alaska 

Maritime National Wildlife Service, Homer, Alaska. 
Table 10.2. Black-legged Kittiwake productivity (chicks fledged per nest site) at Chisik, 

Gull and Barren island, 1995-1 999. - 

Year Chisik Island Gull Island *Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 12 0.02 0.06 6 0.34 0.35 11 0.62 0.25 

1996 7 0.04 0.06 10 0.50 0.31 11 0.72 0.20 

1997 10 0.02 0.04 11 0.60 0.36 11 0.31 0.13 

1998 9 0.00 0.00 10 0.32 0.22 11 0.04 0.06 

1999 9 0.00 0.00 10 0.65 0.11 11 0.45 0.14 

All 5 0.02 0.02 5 0.48 0.15 5 0.43 0.07 

Table 10.3. Black-legged Kittiwake laying success (number of nest structures with 

>=legg, per nest structure) at Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island *Barren Islands - - - -- -- 

n mean stdev n mean stdev n mean stdev 

1995 12 0.38 0.19 6 0.58 0.23 11 0.92 0.06 

1999 9 0.70 0.18 10 0.81 0.09 11 0.72 0.09 

All 5 0.67 0.19 5 0.74 0.12 5 0.69 0.28 

Table 10.4. Black-legged Kittwake clutch size (eggs laid per nest with eggs) at Chisik, 

Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island *Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 12 1.39 0.46 6 1.59 0.28 11 1.83 0.13 

1999 9 1.42 0.38 10 1.62 0.13 11 1.34 0.10 

All 5 1.45 0.11 5 1.64 0.06 5 1.49 0.32 

* Data from : Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren lslands seabird 

studies, 2000, Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration 

Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 
Table 10.5. Black-legged Kittiwake hatching success (chicks hatched per egg laid) at 

Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 12 0.29 0.37 6 0.50 0.31 11 0.91 0.16 

1996 7 0.80 0.12 10 0.75 0.10 n.d. n.d. n.d. 

1997 10 0.57 0.24 11 0.53 0.22 11 0.65 0.15 

1998 9 0.21 0.12 10 0.44 0.25 8 0.56 0.33 

1999 9 0.12 0.12 10 0.70 0.10 11 0.74 0.12 

All 5 0.40 0.28 5 0.58 0.13 5 0.72 0.15 

Table 10.6. Black-legged Kittwake brood size at hatching (chicks hatched per nest with 

chicks) at Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island *Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 12 1.39 0.46 6 1.30 0.15 11 1.71 0.23 

1999 9 1.42 0.38 10 1.45 0.10 11 1.23 0.13 

All 5 1.45 0.11 5 1.40 0.09 5 1.07 0.64 

Table 10.7. Black-legged Kittiwake fledging success (chicks fledged per chick hatched) at 

Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island *Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 12 0.06 0.17 n.d. 11 0.45 0.17 

1999 9 0.00 0.00 10 0.76 0.13 11 0.65 0.12 

All 5 0.03 0.03 5 0.66 0.10 5 0.51 0.1 1 

* Data from : Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren lslands seabird studies, 

2000, Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration Project 00163J), 

U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 10.8. Black-legged Kittiwake brood size at fledging (chicks fledged per nest with - -. - 

chicks) at Chisik, Gull and Barren islands, 1995-1999. 

Year Chisik Island Gull Island *Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 1 1 .OO 4 1.32 0.32 I1 1.37 0.15 

1996 3 1.00 0.00 10 1.24 0.14 0 no chicks no chicks 

1997 2 1.00 0.00 11 1.31 0.16 9 1.05 0.84 

1998 0 n.d. 10 1.37 0.28 1 0.00 0.00 

1999 0 n.d. 10 1.35 0.14 10 1.11 0.10 

All 3 1.00 0 5 1.32 0.05 4 1.18 0.17 

Table 10.9. Black-legged Kittiwake egg laying chronology at Chisik, Gull and Barren 

islands. 1995-1 999. 

Year Chisik Island Gull Island *Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 12 20-Jun 7.77 6 19-Jun 6.41 11 10-Jun 1.78 

1996 7 5-Jun 1.12 10 12-Jun 6.30 11 Il-Jun 7.22 

1997 10 13-Jun 2.37 11 8-Jun 1.58 11 20-Jun 2.88 

1998 9 9-Jun 4.19 10 16-Jun 1.84 10 29-Jun 5.34 

1999 9 15-Jun 2.67 10 13-Jun 1.90 11 22-Jun 0.90 

All 5 12-Jun 5.73 5 13-Jun 4.16 5 18-Jun 7.96 

Table 10.10. Black-legged Kittiwake chick hatching chronology at Chisik, Gull and 

Barren islands, 1995-1 999. 

Year Chisik Island Gull Island *Barren Islands - 

n mean stdev n mean stdev n mean stdev 

1995 12 8-JuI 3.89 6 14-JuI 5.66 12 7-JuI 1.83 

1999 9 10-Jul 3.58 10 10-Jul 2.07 11 19-Jul 1.27 

All 5 6-Jul 3.65 5 Il-Jul 3.39 5 15-Jul 8.88 

* Data from : Kettle, A,, D.G. Roseneau, G.V. Byrd. 2000. Barren lslands seabird 

studies, 2000, Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration 

Project 00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife 

Service, Homer, Alaska. 
Table 10.1 1. Black-legged Kittiwake productivity index at Gull and Chisik Islands, 1995-1999. This index is the 

proportion of large chicks counted late in the season to the number of nests counted during middle incubation, for the 

whole colony. 

Year Chisik Island Gull Island 

nests fledglings prod. lndex first count 2nd count nests fledglings prod. lndex first count 2nd count 

1995 n.d. 5719 2288 0.40 13-Jul 9-Aug 

1996 n.d. 5152 2885 0.56 29-Jun 4-Aug 

1997 13,341 67 0.01 19-Jun 7-Aug 4435 2040 0.46 26-27 Jun 3-4 Aug 

1998 n.d. 4800 1344 0.28 17-18 Jun 12-Aug 

1999 11,063 1041 0.09 21-Jun 22-Aug 5809 3427 0.59 23-24 Jun 10-Aug 
Table 10.12. Black-legged Kittiwake attendance expressed as "bird-minutes" or the 

combined minutes both parents spent at the nest site per hour during chick-rearing at 

Chisik, Gull and Barren islands, 1995-1999 (n = nest sites). 

Year Chisik Island Gull Island **Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 * * 11 57.72 4.30 

1996 14 57.69 5.05 18 58.26 8.10 8 56.42 6.34 

1997 5 57.61 4.05 31 60.66 2.55 19 48.32 17.58 

1998 * 31 60.63 3.93 23 58.93 5.50 

1999 * 24 59.54 6.69 29 50.20 15.19 

All 2 57.65 0.71 4 59.77 2.53 5 54.32 6.13 

Table 10.13. Black-legged Kittwake chick-feeding rates (feeds per hour) at Chisik, Gull and 

Barren islands, 1995-1 999 (n = nest site). 

Year Chisik Island Gull Island **Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 * * 11 0.19 0.08 

1999 * 24 0.23 0.12 29 0.15 0.08 

All 2 0.13 0.01 4 0.22 0.02 5 0.18 0.02 

Table 10.14. Black-legged Kittiwake foraging trip durations (minutes) when chick 

provisioning (resulted in chick feeding) at Chisik, Gull and Barren islands, 1995-1999 (n = 

nest sites). 

Year Chisik Island Gull Island **Barren Islands 

n mean stdev n mean stdev n mean stdev 

1995 * * 10 235.01 59.63 

1999 * 23 236.42 115.30 24 338.66 164.20 

All 2 308.30 30.43 4 196.38 33.95 5 314.86 56.40 

* Breeding failure limited observations to less than 2 nest sites. 

** Data from : Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren lslands seabird studies, 

2000, Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration Project 

00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, 

Alaska. 
Table 10.1 5. Growth rates (gld*) of Black-legged Kittiwake chicks by rank at Gull and the 

Barren islands, 1995-1 999. 

Rank Year Chisik Gull **Barrens 

n mean stdev n mean stdev n mean stdev 

Alpha 1 Singleton 1995 n.d. 16 15.5 8.9 8 19.1 3.4 

1996 10 11.0 6.2 2 17.2 4.3 32 17.5 6.1 

1997 8 14.5 4.4 36 15.4 3.7 35 16.2 4.8 

1998 n.d. 46 16.1 2.7 13 17.3 2.6 

1999 n.d. 30 16.2 2.2 36 17.8 3.4 

Beta 1995 n.d. 2 13.8 6.5 5 19.8 4.5 

1996 1 12.0 1 17.4 3 18.4 6.1 

1997 n.d. 9 12.6 3.1 6 6.9 5.0 

1998 n.d. 18 15.5 1.7 1 21.7 -- 

1999 n.d. 17 15.6 3.2 6 14.2 3.0 

*Slope of linear regression of mass on age for chicks age 6-22 d. 

**Data from : Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 2000, 

Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration Project 00163J), U.S. Fish 

and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, Alaska. 
Table 10.16. Baseline concentrations of corticosterone (nglml) in Blacklegged Kittwakes at Gull and Chisik islands, 1997-1999. 

Year Breeding stage Gull Island Chisik Island 

n mean stdev n mean stdev 

1997 Pre-egg-laying 

lncubation 

Early chick-rearing 

Late chick-rearing 

Total 

1998 Pre-egg-laying 

lncubation 

Early chick-rearing 

Late chick-rearing 

Total 

1999 Pre-egg-laying 

lncubation 

Early chick-rearing 

Late chick-rearing 

Total 

All Grand Total 3 7.97 2.63 3 8.24 0.71 
Table 10.17. Summary of Black-legged Kittiwake chick diet composition (% mass) at Chisik, and Gull islands, 1995-1999. 

Prey Chisik Island Gull Island Barren Islands 

1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 

No. regurgitations 0 19 27 17 3 66 40 74 100 101 68 383 40 74 100 101 68 383 

Total biomass (g) -- 266 520 241 24 1051 228 825 1727 1776 1406 5961 228 825 1727 1776 1406 5961 

Mean gtsample -- 14 19 14 8 16 6 11 17 18 21 16 6 11 17 18 21 16 

Osmerids -- 18.0 0.0 16.3 0.0 8.3 10.7 2.0 0.6 5.7 1.8 3.0 10.7 2.0 0.6 5.7 1.8 3.0 

Herring -- 0.0 11.7 0.0 0.0 5.8 0.0 7.5 20.1 22.3 11.5 16.2 0.0 7.5 20.1 22.3 11.5 16.2 

Sand lance -- 69.8 72.9 74.8100.0 73.2 86.0 80.0 73.5 70.5 85.5 76.8 86.0 80.0 73.5 70.5 85.5 76.8 

Gadids -- 0.0 3.7 0.0 0.0 1.8 1.4 0.0 3.2 1.3 0.5 1.5 1.4 0.0 3.2 1.3 0.5 1.5 

Other -- 9.4 6.2 8.7 0.0 7.5 0.0 0.0 0.4 0.3 0.7 0.4 0.0 0.0 0.4 0.3 0.7 0.4 

Unidentified fish -- 0.1 3.6 0.0 0.0 1.8 1.9 6.5 0.2 0.0 0.0 1.0 1.9 6.5 0.2 0.0 0.0 1.0 

Invertebrates -- 2.7 1.9 0.2 0.0 1.6 0.0 4.0 2.0 0.0 0.0 1.1 0.0 4.0 2.0 0.0 0.0 1.1 
Table 10.18. Average feeding frequency, meal size, energy density, and energy provisioning 

rates to Black-legged Kittiwake broods at Gull, Chisik, and Barren islands, Cook Inlet, Alaska 

1995 - 1999. Data from Dan Roby and Patrick Jodice of the Cooperative Fish and Wildlife 

Unit at Oregon State University, Corvalis, Oregon. 

Location 1 Year Feeding frequency Meal size (g) Energy density (kJ I Energy provisioning 

(rnealslnesVday)* g wet mass) rate (kj I nest day) 

Barren Islands 

1996 

1997 

1998 

1999 

Gull Island 

1996 

1997 

1998 

1999 

Chisik Island 

1996 

1997 

1998 

1999 

2 

2.5 

Failed 

Failed 

* Based on feeds I hour and an 18 hour day. 
Table 10.19. Summary of adult Black-legged Kittwake diet composition (% mass) at Chisik, Gull and Barren islands, 1995-1999. 

Prey Chisik Island Gull Island Barren Islands 

1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 1995 1996 1997 1998 1999 Total 

No. stomachs 

Total biomass (g) 

Mean glstomach 

Osmerids 

Sand lance 

Gadids 

Other 

Unidentified fish 

Invertebrates 
Table 10.20. Black-legged Kittiwake adult size and condition, Chisik Island 1997-1999, summarized by capture bout 

Year Culmen (mm) Headbill (mm) Tarsus (mm) Wing (mm) Mass (g) Masslwing 

bout date n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

1997 11-Jun 7 38.5 2.90 0 7 35.2 1.46 7 316.9 7.69 7 422.9 32.64 7 1.33 0.10 

23-Jun 61 37.7 1.61 61 93.0 2.86 61 35.0 1.29 61 319.4 7.37 61 394.9 42.28 61 1.24 0.13 

1-JuI 2 35.0 4.17 2 88.8 5.37 2 33.4 3.32 2 317.5 4.95 2 363.5 33.23 2 1.15 0.12 

31-JuI 6 37.6 1.16 4 93.6 3.92 6 35.0 1.40 6 307.5 12.44 6 354.2 32.47 6 1.15 0.10 

1997 Total 76 37.7 1.83 67 92.9 3.02 76 35.0 1.36 76 318.2 8.33 76 393.4 42.78 76 1.24 0.13 

1998 10-Jun 

19-Jun 

28-Jun 

5-JuI 

1998 Total 

1999 13-Jun 

24-Jun 

3-JuI 

1999 Total 

Grand Total 176 37.9 1.81 166 93.2 3.07 176 35.2 1.37 176 321.3 8.73 176 406.9 42.51 176 1.27 0.12 
Table 10.21. Black-legged Kittiwake adult size and condition, Gull Island 1997-1999, summarized by capture bout date. 

Year Culmen (mm) Headbill (mm) Tarsus (mm) Wing (mm) Mass (g) Masslwing 

bout date n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

27-Jun 15 39.3 2.51 15 94.6 4.61 15 35.5 1.23 15 325.3 9.25 15 409.2 44.17 15 1.26 0.11 

2-JuI 15 39.6 1.77 15 94.9 3.46 15 35.8 0.89 15 321.6 7.46 15 417.7 33.00 15 1.30 0.09 

11-JuI 7 37.5 1.44 7 90.8 2.77 7 34.6 1.08 7 316.9 5.84 7 397.1 33.52 7 1.25 0.09 

22-JuI 10 39.8 1.56 5 95.9 3.26 10 35.7 1.20 10 317.1 7.42 10 400.8 38.08 10 1.26 0.11 

4-Au~ 8 40.5 4.56 8 94.8 3.31 8 34.9 1.01 8 320.6 6.78 8 374.424.85 8 1.17 0.07 

1997 Total 69 39.2 2.39 50 94.3 3.88 68 35.5 1.10 69 320.7 7.72 69 400.3 37.96 69 1.25 0.10 

1998 13-Jun 21 38.8 1.62 21 94.2 2.77 21 35.8 1.14 21 324.7 9.94 21 438.6 44.51 21 1.35 0.13 

22-Jun 21 39.1 1.58 21 95.4 3.29 21 36.0 1.21 21 322.3 7.42 21 421.3 39.02 21 1.31 0.12 

30-Jun 7 37.6 3.12 7 94.6 3.49 7 35.5 1.53 7 324.6 6.02 7 404.324.57 7 1.25 0.06 

7-JuI 7 39.9 3.07 7 95.6 3.76 7 35.5 1.23 7 326.0 11.00 7 409.6 37.79 7 1.26 0.11 

15-JuI 15 38.7 1.93 15 94.3 3.71 15 35.4 1.50 15 323.8 8.45 15 426.2 38.28 15 1.32 0.11 

22-JuI 11 39.1 2.09 12 94.0 3.71 12 35.6 1.14 12 316.6 10.77 12 411.1 41.28 12 1.30 0.10 

1-Au~ 11 40.1 1.67 11 96.1 3.44 11 35.3 1.51 11 322.4 8.96 11 428.8 32.66 11 1.33 0.09 

12-Au~ 10 39.7 1.92 10 95.6 3.79 10 34.7 1.09 10 325.6 7.88 10 380.5 44.66 10 1.17 0.11 

1998 Total 103 39.1 2.01 104 94.9 3.38 104 35.5 1.29 104 323.1 9.02 104 419.3 41.55 104 1.30 0.12 

1999 13-Jun 10 38.5 1.57 10 94.0 3.30 10 35.6 1.59 10 322.1 10.27 10 422.9 36.54 10 1.31 0.09 

25-Jun 14 39.2 1.45 14 94.8 2.96 14 36.4 1.35 14 325.1 9.28 14 408.1 24.77 14 1.26 0.07 

6-JuI 8 39.4 1.23 8 95.3 2.22 8 36.3 0.85 8 326.310.35 8 423.934.01 8 1.30 0.09 

20-JuI 9 39.5 1.60 9 94.3 3.03 9 36.0 1.20 9 325.9 6.43 9 394.432.48 9 1.21 0.09 

3-Au~ 9 38.9 1.39 9 94.7 2.04 9 36.1 1.24 9 322.4 9.14 9 358.920.42 9 1.11 0.08 

15-Au~ 12 39.1 2.16 12 95.2 3.22 12 36.3 1.23 12 320.3 6.79 12 395.1 39.44 12 1.23 0.11 

1999 Total 62 39.1 1.59 62 94.7 2.80 62 36.1 1.25 62 323.6 8.71 62 400.9 36.99 62 1.24 0.10 

Grand Total 239 39.2 2.02 221 94.7 3.31 239 35.7 1.25 240 322.4 8.62 240 408.1 40.51 240 1.27 0.11 
Table 10.22. Black-legged Kittiwake adult mass, Barren Island* 1997-1 999, summarized 

by capture bout date. 

Year Wing (mm) Mass (g) Mass I wing 

bout date n mean stdev n mean stdev n mean stdev 

1997 24-Jun 1 320.00 - 1385.00 - 1 1.20 

28-Jun 

29-Jun 

30-Jun 

3-JuI 

14-Aug 

I -Au~ 

2-Au~ 

3-Au~ 

6-Au~ 

7-Au~ 

15-Aug 

1997 Total 

1998 26-Jun 

28-Jun 

29-Jun 

6-JuI 

1 0-JuI 

1 2-Jul 

1 4-Jul 

27-Jul 

2-Au~ 

1 0-Aug 

I I -Au~ 

12-Aug 

2 1 -Aug 

1999 Total 70 318.83 3.55 70 411.45 25.56 70 1.29 0.07 

Grand Total 195 317.74 1.04 195 401.37 24.98 195 1.26 0.05 

* Data from : Kettle, A., D.G. Roseneau, G.V. Byrd. 2000. Barren Islands seabird studies, 

2000, Exxon Valdez Oil Spill Restoration Project Final Report (Reostoration Project 

00163J), U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Service, Homer, 

Alaska. 
Table 1 1.1. Duration of counts made at Pigeon Guillemot colony sites in Kachemak 

Bay. 

Colony site Area* Count duration (min.) 

Guillemot Meadows moving count 

Naskowhak Pt. 5 

Lemon Cliffs 5 

Gray Cliffs Seldovia Bay 5 

Seldovia Bay Seldovia Bay moving count 

Sub-Seldovia Seldovia Bay 5 

Seldovia Pt. Seldovia Bay moving count 

Kasitsna Cliffs 5 

Hesketh I. Hesketh I. moving count 

S. W. Yukon 5 

Yukon I. Yukon I. 5 

Sub-Yukon Yukon I. 5 

S. Neptune Bay 5 

N. Neptune Bay Neptune Bay 10 

China Poot Bay 5 

Motherlode Moosehead Pt. moving count 

Moosehead N. Side Moosehead Pt. 5 

Moosehead Peterson Side Moosehead Pt. 10 

E. Peterson Bay 5 

The Nose 5 

Peterson Pt. 5 

lsmailof I. 5 

Sea Cliff Manor 5 

Triangle Rock 5 

Goshawk 5 

Mallard Bay moving count 

*Indicates the individual colony sites that make up larger census areas. 
Table 1 1.2. Age - wing length data 

used to age unknown-age Pigeon 

Guillemot chicks (from known-age 

chicks raised in captivity, G. Divoky, 

unpubl data.). 

Age Mean wing length 

(d) (mm) 
Table 11.3. Results of replicated counts at individual Pigeon Guillemot colony sites in Kachemak 

Bay, 1996-1999. 

Colony Site 1996 1997 1998 1999 

n mean stdev n mean stdev n mean stdev n mean stdev 

Guillemot Meadows 

Naskowhak Pt. 

Lemon Cliffs 

Gray Cliffs 

Seldovia Bay 

Sub-Seldovia 

Seldovia Point 

Kasitsna Cliffs 

Hesketh 

S.W. Yukon 

Yukon I. 

Sub-Yukon 

S. Neptune 

N. Neptune 

China Poot Bay 

Motherlode 

N. Moosehead Pt. 

E. Moosehead Pt. 

E. Peterson Bay 

The Nose 

Peterson Pt. 

lsmailof I. 

Sea Cliff 

Triangle Rock 

Goshawk 

Mallard Bay 
Table 11.4. Results of replicated counts of Pigeon Guillemots at different areas of Kachemak Bay, 1996- 

1999. 

Area 1996 1997 1998 1999 

n mean stdev n mean stdev n mean stdev n mean stdev 

Seldovia Bay 2 89.5 4.9 6 81.8 19.2 5 79.6 23.0 3 55.0 9.6 

Hesketh I. 3 39.7 1.5 6 29.8 4.6 8 43.0 6.8 4 25.0 7.6 

Yukon I. 3 20.0 5.6 5 14.6 8.4 7 23.6 9.3 3 7.3 2.1 

Neptune Bay 3 29.3 0.6 9 29.0 4.7 7 25.4 4.2 3 15.0 2.6 

Moosehead Pt. 3 100.0 10.0 8 110.3 9.1 6 119.0 11.0 3 78.7 6.7 
Table 1 1.5. Results of annual 

surveys of Pigeon Guillemots 

along the south shore of 

Kachemak Bay, 1995-1 999. 

Year Count 

1995 557 

1996 467 

1997 634 

1998 504 

1999 563 
Table 1 1.6. Median hatch date of Pigeon Guillemot 

eggs in Kachemak Bay, 1995-1999. 

Area Year n median 

(nests) hatch date* 

Inner Bay 1995 24 714 

1996 15 6/28 

1997 20 714 

1998 12 711 

1999 9 6/30 

Outer Bay 1995 25 712 

1996 15 6/29 

1997 23 71 1 

1998 17 712 

* Date that first egg in a given nest hatched 
Table 11.7. Percent composition (by number) of prey items in Pigeon Guillemot nestling diets at Kachemak Bay, Alaska, 1995-1999. 

Taxon Halibut Moosehead Point 1 Moosehead 2 MooseCove head 3 

1995ia 199!ia 1996 1997 1999 1998 1999 1998 

Total schooling fish 41.1 83.4 46.1 74.1 79.6 55.2 77.8 68.6 

Sand lanced 39.1 83.4 44.2 67.7 79.6 55.2 76.6 68.6 

~apelin~,~ 1.9 

salmonidsf 2.0 0.4 

Unidentified schooling fish 6.0 1.2 

Total demersal fish 

~adids~,~ 

sculpinsh 

Blennies' 

Gunnels' 

Pricklebacks, eelblenniesk 

Arctic shannyb" 

~onquils~~"' 

Unidentified blennies 

Total blennies 

Flatfishn 

Rockfish0 

~reenlings~~~ 

Unidentified demersal fish 

Total invertebrates 2.0 

Hermit Crabsq 

Shrimpr 2.0 

Unidentified invertebrates 

Unidentified 3.3 5.7 4.1 3.2 2.9 2.3 

n 151 175 412 249 103 58 171 86 

'Observations made from boats. b~hese identifications were not used in 1995, and these groups could not be reliably distinguished during 

boat observations. May have been present this year, but not identified. Ammodytes hexapterus Mallotus villosus ' Salmonidae 

Gadidae Cottidae ' Blenniodea j Pholidae Lumpenus spp. ' Stichaeus punctatus Bathymaster signatus, Ronquilus jordani " 

Pleuronectiformes O Sebastes spp. Hexagrammihe Anomura Decapoda 
Table 11.7 (continued). Percent composition (by number) of prey items in Pigeon Guillemot nestling diets at Kachemak Bay, Alaska, 

1995-1999. 

Taxon Neptune Yukon Island Outer Seldovia 1 Outer Inner Seldovia 1 Inner 

Bay Seld. 2 Seld. 2 

1995a 1996a 1997 1996a 1997 1998a 1997a 1998a 1998a 

Total schooling fish 20.0 2.9 1.9 21.1 14.8 11.1 0.8 9.6 

Sand lanced 19.3 1 .O 21.1 14.4 11.1 3.8 

capelinbze 0.4 0.8 

salmonidsf 0.7 2.9 1 .O 1 .O 

Unidentified schooling fish 4.8 

Total demersal fish 

~adids~,~ 

sculpinsh 

Blennies' 

Gunnels1 

Pricklebacks, eelblenniesk 

Arctic shannybh' 

~onquils~~~ 

Unidentified blennies 

Total blennies 

Flatfishn 

Rockfish0 

~reenlings~)~ 

Unidentified demersal fish 

Total invertebrates 

Hermit Crabsq 

Shrimpr 

Unidentified invertebrates 

Unidentified 26.7 2.9 10.5 15.5 9.6 15.2 6.3 3.1 2.9 

'Observations made from boats. b~hese identifications were not used in 1995, and these groups could not be reliably distinguished during 

boat observations. May have been present this year, but not identified. Ammodytes hexapterus Mallotus villosus * Salmonidae 

Gadidae Cottidae ' Blenniodea j Pholidae Lumpenus spp. ' Stichaeus punctatus Bathymaster signatus, Ronquilus jordani " 

Pleuronectiformes O Sebastes spp. Hexagrammidae Anomura * Decapoda 
Table 11.8. Growth parameters of alpha and singleton Pigeon Guillemot chicks in Kachemak Bay, 1995-1999. 

Area Year Age 8-1 8 rate (g 1 day)a Age 5-20 rate (g 1 day)a Mass at age 30 * 2 d Fledge massb 

n mean stdev n mean stdev n mean stdev n mean stdev 

Inner Bay 1995 16 20.4 4.5 15 19.8 2.6 13 467 44 

1996 7 17.5 4.9 8 17.2 3.6 9 423 85 

1997 9 18.1 5.9 14 17.1 5.8 7 434 77 6 447 32 

1998 7 19.4 5.9 9 16.9 4.8 4 411 49 2 448 39 

1999 5 19.8 2.2 7 20.6 2.2 1 500 

Outer Bay 1995 14 19.6 6.5 16 19.1 4.1 13 423 94 

1996 8 17.1 4.8 9 18.4 4.3 6 429 29 

1997 11 18.0 4.4 11 18.5 2.9 10 415 54 13 441 34 

1998 7 19.8 2.3 10 16.8 4.7 10 412 32 9 430 39 

a Slope of linear regression of mass on age 

Mass within 1 day of fledging 
Table 1 1.9. Growth parameters of beta Pigeon Guillemot chicks in Kachemak Bay, 1995-1 999. 

Area Year Age 8-1 8 rate (g 1 day)a Age 5-20 rate (g / day)a Mass at age 30 * 2 d Fledge massb 

n mean stdev n mean stdev n mean stdev n mean stdev 

Inner Bay 1995 

1996 

1997 

1998 

1999 

Outer Bay 1995 

1996 

1997 

1998 

a Slope of linear regression of mass on age 

b Mass within 1 day of fledging 
Table 1 1.10. Mayfield parameters and estimates of reproductive success for Pigeon Guillemots in 

Kachemak Bay, 1995-1 999. 

Area Year n mean Egg Proportion Age 1-1 5 Age 16-30 chicks fledged Brood at fledge 

(nests) clutch size DSR Hatching DSR DSR 1 nesting pair* n mean stdev 

Inner Bay 1995 45 1.78 0.984 0.63 0.973 0.997 0.44 

1996 33 1.81 0.987 0.71 1 .OOO 0.988 0.71 10 1.90 0.32 

1997 29 1.77 0.983 0.89 0.983 0.971 0.47 9 1.78 0.44 

1998 19 1.64 0.961 0.78 0.982 0.957 0.15 4 1.50 0.58 

1999 15 0.67 6 1.67 0.52 

1995-1 998 141 1.78 0.983 0.74 0.984 0.983 0.47 29 1.76 0.44 

Outer Bay 1995 39 1.80 0.981 0.79 0.962 0.991 0.38 

1996 30 1.83 0.988 0.63 0.969 0.974 0.34 4 1.75 0.50 

1997 36 1.72 0.979 0.74 0.964 0.992 0.34 18 1.56 0.51 

1998 34 1.70 0.976 0.63 0.928 0.967 0.10 12 1.33 0.49 

1999 14 0.29 3 1.33 0.58 

1995-1 998 153 1.76 0.982 0.70 0.959 0.983 0.29 37 1.49 0.51 

*Productivity estimates for 1999 are not directly comparable with estimates from other years - see 

Methods for details. 
Table 1 1.1 1. Fledging age of Pigeon Guillemot chicks 

in Kachemak Bay, 1996-1998. 

Fledging age (d) 

Area Year n mean stdev 

Inner Bay 1996 10 34.9 3.2 

1997 17 34.9 3.0 

1998 6 36.3 3.3 

Outer Bay 1996 6 36.7 2.6 

1997 14 37.9 3.2 

1998 13 37.8 3.5 
Table 11.12. Age-dependant observed mortality rate of 

Pigeon Guillemot chicks in Kachemak Bay, 1995-1999. 

Chick # of obs* # of Mortality rate 

age (d) deaths (deaths / obs) 

*number of chicks observed alive at given age 
Table 1 1.13. Measurements of adult Pigeon Guillemots in Kachemak Bay, 1995-1 999. 

Area Mass Wing* Culmen 

n mean stdev n mean stdev n mean stdev 

lnner Bay 

Outer Bay 

Both areas 

Area Headbill Tarsus 10th Primary 

n mean stdev n mean stdev n mean stdev 

lnner Bay 

Outer Bay 

Both areas 

* Flattened wing length 
Table 12.1. Horned Puffin breeding success on Duck (Chisik) Island. 

Year 1999 1998 1997 1996 1995 chi square df P 

Total no. egg-sites 47 6 1 48 5 1 2 1 

Total no. chicks 36 42 32 43 15 

Total no. fledglings 33 34 26 35 12 

Hatching Success 0.77 0.69 0.67 0.84 0.71 5.186 4 >0.5 

(Chickslegg-site) 

stdev 0.43 0.47 0.48 0.37 0.46 

Fledging Success 0.97 0.89 0.96 0.83 0.92 4.71 4 >0.5 

(Fledglingslchicks) 

stdev 0.17 0.31 0.19 0.38 0.28 

Breeding Success 0.70 0.62 0.64 0.70 0.66 5.186 4 >0.5 

(Fledglingslegg-sites) 

stdev 0.46 0.50 0.50 0.47 0.51 

Median chick hatch date 26-Jul 29-Jul 25-Jul 19-Jul 21-Jul 

no.chicks used for phenology 33 27 28 35 13 

stdev 5.58 5.49 5.43 5.96 4.48 

Notes: Nest-site is sample unit. Hatching, fledging and reproductive success are compared 

between years using a chi-square contigency table. All tests were non-significant, with four 

degrees of freedom. Median chick hatch dates are limited to chicks with precise hatch dates. 
Table 12.2. Diet composition (% number) of Horned Puffin chicks at Duck 

(Chisik) Island in 1995-1 999. 

Prev Items 1995 1996 1997 1998 1999 

. - .- . - . - .- .- . - . - . . . - 

Pacific sandlance 91 98 825 94 465 95 1174 95 103 99 

Ammodytes hexapterus 

Rockfish species 0 0 00 00 10.1 00 

Sabastes sp. 

Gadidae 0 0 0 0 20.4 0 0 0 0 

Capelin 22273 92131 00 

Mallotus villosus 

unidentified squid 0 0 00 00 20.2 00 

Salmon sp. 00162 71343 11 

Onchorhynchus sp. 

Euphasiid 0 0 00 61 10.1 0 0 

Sculpin sp. 

Cottidae sp. 

Pacific Lamprey 0 0 4 0.5 0 0 4 0.3 0 0 

Lampetra tridentatus 

Sandfish 0 0 10.1 00 00 0 0 

Trichodon trichodon 

unidentified Smelt 0 0 00 00 20.2 00 

Osmeridae 

Unidentified fish species 0 0 00 010.22 00 

Total prey items 93 875 491 1233 1 04 
Table 12.3. Mean size and energy value of sandlance in Horned Puffin chick diet. 

Year Length (mm) N SD Mass (g) N SD kJ N SD 

1995 92.7 93 24.7 2.9 93 2.6 16.1 93 15.2 

1996 85.2 542 31.5 2.1 560 1.8 13.8 293 10.1 

1997 86.0 143 19.1 2.5 142 2.3 13.1 142 13.7 

1998 95.4 1170 16.5 3.1 1011 2.0 16.6 1111 10.7 

1999 100.2 101 8.5 3.3 104 1.0 18.7 101 6.2 

F P d f F P d f F P d f 

year 26.51 <0.001 4 28.76 <0.001 4 7.86 <0.001 4 

error 2049 2022 1735 

Note: Length was measured fork length, mass is mean fresh mass and kJ is mean food 

energy in kJ. There was a significant difference in sandlance length, mass and energy 

value between years (one-way ANOVA results presented). 
Table 12.4. Characteristics of meal loads delivered by 

Horned Puffins to their chicks. 

YEAR Masslload (g) No. prey itemslload 

mean n SE mean n SE 

1995 15.2 3.0 2.4 7.7 3.0 2.2 
Table 12.5. Horned Puffin daily food delivery rates at Duck Island. 

Year Date Time Deliveries 

Start Finish Mean N* SD Phenology 

1996 23-Aug-96 630 2200 5.4 5 2.0 late chick-rearing 

1996 24-Aug-96 630 2200 6.8 5 2.2 late chick-rearing 

1997 26-Jul-97 500 2300 2.8 5 0.8 late incubationlearly chick-rearing 

1997 1-Aug-97 500 2300 3.4 5 1.1 early chick-rearing 

1997 13-Aug-97 600 2200 2.6 7 1.0 mid chick-rearing 

* N = number of nests observed 
Table 12.6. Linear growth rates of Homed Puffin chicks on Duck Island in different years 

Year Body Mass (g/day) Wing (dday) Culmen length (mmlday) Tarsus (dclay) 

Mean N SD Mean N SD Mean N SD Mean N SD 

treatment 1 1.7 4 <.oo~ 

error 86 

Means followed by different letters are significantly different as determined from Tukey multiple comparison tests. 
Table 12.7. Horned Puffin chick fledging 

age on Duck Island. Fledging age (+I- 3 

days) is calculated from productivity and 

growth data of known age chicks. 

Year Fledging age (days) 

Mean SD N 

1996 42.1 4.9 25 
Table 12.8. Measurements of Horned Puffin fledglings caught 

en route to the ocean. All measurements in mm except mass, 

which is in grams. 

Date Wing Tarsus Headbill Culmen Mass 

29-Aug-98 158 385 
Table 12.9. Census counts of Horned Puffins on Duck Island. 

1995 8-Aug-95 811 761 235 1807 midchick-rearing1996 12-Jul-96 335 198 236 769 late incubation 

1996 16-Jul-96 364 435 160 959 lateincubation 

1997 16-Jul-97 233 485 29 747 late incubation 

1997 17-Jul-97 197 780 10 987 late incubation 

1997 18-Jul-97 527 652 100 1293 late incubation 

1997 14-Aug-97 1323 757 255 2335 midllate chick-reaing 

1997 15-Aug-97 631 230 25 886 midllate chick-reaing 

1997 17-Aug-97 985 41 0 225 1620 midllate chick-reaing 

1998 25-Jun-98 290 1017 0 1307 late incubationlearly chick-reaing 

1998 26-Jun-98 551 1342 300 2193 late incubationlearly chick-reaing 

1998 27-Jun-98 261 91 7 22 1200 late incubationlearly chick-reaing 

1998 25-Aug-98 1580 470 750 2800 late chick-rearing 

1998 2-Sep-98 649 479 21 8 1346 late chick-rearing 

1999 9-Aug-99 1472 690 435 2597 mid chick-rearing 

1999 4-Sep-99 2380 1380 610 4370 late chick-rearing 

"Land" = no. birds counted on shore (all individuals visible on rocks, vegetation and cliff). 

"Water" = no. birds counted in rafts or as individuals on the water within about 200m from shore. 

"Flying" = no. birds counted flying around colony. "Total" = total no. birds counted on land, water 

and flying. 
Table 12.10. Whole island census counts of Tufted Puffin on Duck Island. 

Year Date Total no. Stage of breeding 

1995 24-Jul-95 26 early chick-rearing 

1995 8-Aug-95 54 mid chick-rearing 

1996 12-Jul-96 12 late incubation 

1996 16-Jul-96 6 late incubation 

1997 16-Jul-97 3 late incubation 

1997 17-Jul-97 9 late incubation 

1997 18-Jul-97 14 late incubation 

1997 14-Aug-97 20 midllate chick-reaing 

1997 15-Aug-97 5 midllate chick-reaing 

1997 17-Aug-97 11 midllate chick-reaing 

1998 25-Jun-98 28 late incubationlearly chick-reaing 

1998 26-Jun-98 29 late incubationlearly chick-reaing 

1998 27-Jun-98 63 late incubationlearly chick-reaing 

1999 10-Aug-99 20 mid chick-rearing 

1999 4-Sep-99 34 late chick-rearing 

"Total no." = sum of birds on land, water and in flight. 
Table 13.1. Glaucous-winged Gull productivity and hatching chronology at Chisik and Gull Islands, 1995-1999. 

Colony Year Clutch size *Productivity Hatching success **Brood size at hatch Hatch date 

n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

Gull 1995 2 2.07 0.10 2 1.31 0.23 2 0.64 0.14 2 2.00 0.00 2 2-JuI 1.41 

1996 5 2.39 0.15 5 1.25 0.26 5 0.53 0.14 5 1.93 0.16 5 4-JuI 5.41 

1997 5 2.47 0.35 5 1.30 0.33 5 0.52 0.07 5 2.03 0.25 5 30-Jun 2.17 

1998 5 2.40 0.22 5 1.55 0.43 5 0.65 0.19 5 2.20 0.40 5 30-Jun 2.90 

1999 5 2.23 0.32 5 1.43 0.30 5 0.64 0.08 5 2.16 0.41 5 8-JuI 5.66 

Chisik 1995 n.d. n.d. n.d. n.d. n.d. 

***I996 12 2.42 0.75 30 1.73 0.96 9 0.53 0.35 27 1.93 0.74 2 27-Jun --- 

1997 2 2.41 0.06 2 1.23 0.32 2 0.51 0.12 2 2.33 0.47 2 26-Jun 0.71 

1998 2 2.88 0.18 2 1.50 0.71 2 0.53 0.28 2 2.45 0.07 2 24-Jun 1.06 

1999 3 2.07 0.32 3 1.07 0.57 3 0.50 0.18 3 2.05 0.33 3 5-JuI 2.90 

*Productivity is defined as chicks hatched per nest with eggs. 

**Brood size at hatch is defined as the number of chicks hatched per nest with chicks. 

***Nest site used as sample unit. 
Table 13.2. Number of adult Glaucous-winged Gulls counted in plots from middle 

incubation to the start of fledging at Chisik (plots 1-7)* and Gull Islands (plots 1-10), 

1995-1 999. 

Chisik Island Gull Island 

Year plots 1-7 North & Snug Harbor plots plots 1-10 

n mean stdev n mean stdev n mean stdev 

*data reported for Chisik 1995-1999 are for only those plots where gulls were 

present. However, plots 1-7 were checked periodically for the presence of gulls. 
Table 13.3. Total numbers of individual Glaucous-winged Gulls seen at 

Chisik and Gull Islands 1995-1999. 

Chisik Island Gull Island 

Year 

individuals count date individuals count date 

*single count 

**Duck Island only 
Table 13.4. Pelagic Cormorant productivity and hatching chronology at Gull Island, 1995-1999. 

Year Clutch size Productivity Hatching success Brood size at hatch Brood size at fledge Hatch date 

n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n median stdev 

1995 31 2.17 1.17 31 0.29 0.46 31 0.78 0.39 31 1.80 0.77 31 0.42 0.51 31 28-JuI 6.33 

1996 25 3.00 1.15 25 0.58 0.50 25 0.69 0.36 25 2.72 0.67 25 0.82 0.39 25 9-JuI 10.96 

1997 19 2.69 1.27 19 0.63 1.07 19 0.47 0.38 19 2.40 0.70 19 1.09 1.22 19 22-JuI 13.59 

1998 6 3.83 1.17 6 0.83 0.41 6 0.41 0.30 6 2.00 1.00 6 1.00 0.00 6 10-JuI 5.59 

1999 9 3.00 0.50 9 0.78 0.44 9 0.57 0.40 9 2.29 1.11 9 1.00 0.00 9 17-JuI 3.06 
Table 13.5. Pelagic and Red-faced Cormorant productivity index on Gull Island 1995-1 999. 

Count #1 Count #2 Cormorant spp. Year productivity count date nest count adult count count date nest count adult count chick count 

Pelagic 1995 

1996 

1997 

1998 

1999 

Red-faced 1995 

1996 

1997 

1998 

1999 
Table 13.6. Numbers of Pelagic Cormorant individuals and nests in population plots on Gull Island 1995-1999. 

plots 1-3 plots 1-8 plots 1-10 

individuals nests individuals nests individuals nests 

Year n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev n mean stdev 

1995 2 1 0.00 4 1 0.00 2 43 0.71 4 29 1.41 2 44 0.00 4 30 2.12 

1996 5 1 1.95 4 0 0.00 5 31 3.91 4 20 0.50 5 31 3.91 4 20 0.50 

1997 7 1 0.69 7 1 0.00 7 21 3.09 7 12 0.79 7 23 2.97 7 12 0.38 

1998 8 1 0.35 8 1 0.00 8 18 3.07 8 10 2.56 8 20 3.38 8 10 2.64 

1999 11 4 0.89 11 3 0.00 11 18 5.09 11 11 0.30 11 21 5.28 11 12 0.30 

n = number of count days 
Table 13.7. Numbers of Tufted Puffins in population plots at 

Gull Island 1997-1 999 @=count day). 

Plots Year n mean stdev 
Table 13.8. Tufted Puffin chick growth rates at Gull Island 1997 for five 

individual chicks. Mass growth rate is expressed in terms of grams per day 

during the linear phase of growth. Wing, culmen and tarsus growth is 

millimeters of increase per day over the linear growth phase. 

Chick Mass Wing Culmen Tarsus 

A 20.81 4.29 0.40 0.12 

B 14.36 4.30 0.29 0.20 

C 13.21 3.37 0.50 0.30 

D 15.94 4.04 0.30 0.25 

E 14.44 3.67 0.26 0.14 

Mean 15.75 3.93 0.35 0.20 
Table 14.1. Ranked variability in seabird parameters among years (expressed as "mlm Ratio", the ratio of maximum to minimum values, and as 

C.V., the Coefficient of Variation) and functional relationship with prey density. BLKI= Black-legged Kittiwake; COMU= Common Murre; N= number 

of colony-years of data; Ranks are low (C.V.c20%), medium (20%<C.V.<40%) and high (C.V.>40%). 

Parameter n Variability Relationship with Fish Density 

mlm Ratio C.V. RANK linear r model r model p best-fit model Threshold 

BLKI % Time Adult Present with Chick 11 1.2 6.6 Low 0.08 0.08 NS none 

BLKl Adult Body Condition 15 1.3 7.5 Low 0.03 0.03 NS none 

BLKl Clutch Size 15 1.7 12.3 Low 0.01 0.01 NS none 

BLKl AlphaISingleton Chick Growth Rate 12 1.7 12.6 Low 0.00 0.73 0.012 sigmoidal 0.012 

BLKl Brood Size at Fledging 11 1.4 13.5 Low 0.30 0.59 0.084 sigmoidal 0.013 

BLKl Beta Chick Growth Rate 9 2.8 25.6 Medium 0.00 0.00 NS none 

BLKl Foraging Trip Duration 11 2.3 26.1 Medium 0.59 0.61 0.008 neg. exponential 

BLKl Chick Feeding Rate 11 2.3 26.1 Medium 0.21 0.71 0.045 sigmoidal 0.013 

BLKl Lay~ng Success 15 3.8 28.7 Medium 0.00 0.00 NS none 

BLKl Hatching Success 14 4.3 37.2 Medium 0.01 0.53 0.049 sigmoidal 0.008 

BLKl Density at Sea 12 20.1 72.3 High 0.41 0.80 <0.001 sigmoidal 0.01 3 

Forage Fish Biomass 15 20.3 79.8 High ----- ----- ----- ----- ---- BLKl Fledging Success 13 >27* 81.2 High 0.42 0.89 <0.001 sigmoidal 0.013 

BLKl Breeding Success 15 >36* 87.0 High 0.20 0.64 0.009 sigmoidal 0.015 

COMU % Time Adult Present with Chick 15 0 0.0 Low 0.00 0.00 NS none 

COMU Adult Body Condition 13 1.1 3.8 Low 0.04 0.04 NS none 

COMU Chick Body Condition 10 1.1 4.2 Low 0.05 0.71 0.044 sigmoidal 0.010 

COMU Chick Age at Fledging 8 1.2 4.8 Low 0.37 0.44 0.073 neg. hyperbolic 

COMU Chick Feeding Rate 15 1.7 15.5 Low 0.41 0.41 0.011 linear 

COMU Hatching Success 14 2.3 20.9 Medium 0.11 0.11 NS none 

COMU Foraging Trip Duration 15 2.1 21.1 Medium 0.45 0.49 0.005 neg. exponential 

COMU Fledging Success 13 4.4 28.3 Medium 0.00 0.00 NS none 

COMU Breeding Success 14 4.5 29.2 Medium 0.00 0.02 NS none 

COMU Discretionary Time at Incubation 14 6.7 44.3 High 0.06 0.54 0.040 sigmoidal 0.013 

COMU Discretionary Time at Chick-rearing 15 >27* 65.8 High 0.28 0.65 0.008 sigmoidal 0.012 

COMU Density at Sea 12 12.6 72.4 High 0.16 0.70 0.017 sigmoidal 0.015 

Forage Fish Biomass 15 20.3 79.8 High ----- ----- ----- ----- ----- * minimum rnlm Ratio values obtained by rounding min values upward from zero. 
Table 14.2. Variability in breeding success of Black-legged 

Kittiwakes and Common Murres in different geographic areas. 

See text for sources of data. 

Species Location Breeding success 

n mean CV(%) s.d. 

Kittiwakes Cook Inlet 15 0.31 87 0.27 

Gulf of Alaska 

Aleutians 

Bering Sea 

Chukchi Sea 

Alaska 

Newfoundland 

Vedoy I., Norway 

Hornoya I., Norway 

lsle of May, UK 

North Sea 1986 

North Sea 1987 

North Sea 1988 

West Coast UK 

Atlantic Ocean 

Murres Cook Inlet 

Gulf of Alaska 

Aleutians 

Bering Sea 

Alaska 

California 

Newfoundland 

lsle of May 

Europe 

Atlantic Ocean 
Table 14.3. Preliminary estimate of population parameters for seabirds at Chisik and Gull Islands. 

Type Parameter Black-legged Kittiwake Common Murre 

Chisik Gull Chisik Gull 

Measured Population change (prop. per annum) -0.043 0.088 -0.089 0.091 

Measured Annual adult survival (p.p.a.) 0.930 0.820 0.920 0.960 

Measured Mean productivity (chickslpair) 0.020 0.482 0.560 0.540 

Literature Juvenile survival to breeding 

Estimated Maximum recruitment (p.p.a.) 

Estimated Maximum (im1e)migration (p.p.a.) 0.023 0.171 -0.120 0.023 

Note: recruitment and immigration must balance. For example, if no murre chicks at Chisik survived to 

breed, then recruitment would be zero, and ernmigration would have to be -0.008 to account for 

population trends.