OCS Study 

•

MMS 2006-048 

Relative Contribution of POCS Oil 

Platforms to Regional Population 

Dynamics of a Model Reef Fish, The 

Blackeye Goby Rhinogobiops 

nicholsii, in the Eastern Santa 

Barbara Channel 

Final Technical Summary 

Final Study Report 

U.S. Department of the Interior 

Minerals Management Service

Pacific OCS Region 

OCS Study 

MMS 2006-048 

Relative Contribution of POCS Oil 

Platforms to Regional Population 

Dynamics of a Model Reef Fish, The 

Blackeye Goby Rhinogobiops 

nicholsii, in the Eastern Santa 

Barbara Channel 

Final Technical Summary 

Final Study Report 

Authors 

Hunter S. Lenihan 

Andrew J. Brooks 

Principal Investigators 

Prepared under MMS Cooperative 

Agreement No. 14-35-0001-31063 

by 

Coastal Marine Institute 

Marine Science Institute 

University of California 

Santa Barbara, CA 93106 

U.S. Department of the Interior 

Minerals Management Service Camarillo

Pacific OCS Region November 2006
Disclaimer 

This report has been reviewed by the Pacific Outer Continental Shelf Region, Minerals Management 

Service, U.S. Department of the Interior and approved for publication. The opinions, findings, 

conclusions, or recommendations in this report are those of the authors, and do not necessarily reflect 

the views and policies of the Minerals Management Service. Mention of trade names or commercial 

products does not constitute an endorsement or recommendation for use. This report has not been 

edited for conformity with Minerals Management Service editorial standards. 

Availability of Report

Extra copies of the report may be obtained from: 

U.S. Dept. of the Interior 

Minerals Management Service 

Pacific OCS Region 

770 Paseo Camarillo 

Camarillo, CA 93010 

Phone: 805-389-7621 

A PDF file of this report is available at: 

http://www.coastalresearchcenter.ucsb.edu/CMI/ 

Suggested Citation 

The suggested citation for this report is: 

Lenihan, H.S., and A.J. Brooks. Relative contribution of POCS oil platforms to regional population 

dynamics of a model reef fish, the blackeye goby Rhinogobiops nicholsii, in the Eastern Santa 

Barbara Channel. MMS OCS Study 2006-048. Coastal Research Center, Marine Science Institute, 

University of California, Santa Barbara, California. MMS Cooperative Agreement Number 14-35-

0001-31063. 47 pages. 
Table of Contents 

FINAL TECHNICAL SUMMARY........................................................................ 1 

FINAL STUDY REPORT....................................................................................... 7 

 Introduction.................................................................................................... 8 

 Methods and Materials................................................................................... 10 

 Site Descriptions ...................................................................................... 10 

 POCS Oil Platform Gina.......................................................................... 11 

 Control Sites- Natural Rocky Reefs at Santa Cruz Island ....................... 11 

 Abundance and Recruitment.................................................................... 12 

 Population Structure, Immigration, and Emigration................................ 13 

 Fecundity.................................................................................................. 14 

 Predation Mortality of Blackeye Goby.................................................... 14 

 Age and Growth Estimates ...................................................................... 15 

 Results............................................................................................................ 15 

 Population Abundance............................................................................. 15 

 Recruitment.............................................................................................. 21 

 Population Structure, Immigration, and Emigration................................ 22 

 Fecundity.................................................................................................. 31 

 Predation Mortality of Blackeye Goby.................................................... 33 

 Age and Growth Estimates ...................................................................... 36 

 Discussion...................................................................................................... 36 

 Acknowledgements........................................................................................ 39 

 Literature Cited .............................................................................................. 40 

 
List of Tables 

Table 1. Site characteristics ................................................................................... 12 

Table 2: Tagged blackeye gobies in December 2003 ............................................ 23 

Table 3: Tagged blackeye gobies in January 2004 ................................................ 23 

Table 4: Tagged blackeye gobies in June 2004 ..................................................... 24 

Table 5. Tagged blackeye gobies in July 2004 ...................................................... 24 

Table 6: Tethering control for treatments with empty hooks................................. 34 

Table 7: Tethering control for treatments with empty hooks................................. 34 

 

 

List of Figures 

Figure 1. Site map of study locations...................................................................... 9 

Figure 2. Abundance of fishes as POCS oil platform Gina in June ........................ 16 

Figure 3. Total number and vertical distribution of fishes on 14 June 2003........... 17 

Figure 4. Abundance of fishes as POCS oil platform Gina in July......................... 18 

Figure 5. Total number and vertical distribution of fishes on 17 July 2003 ........... 19 

Figure 6. Abundance of fishes as POCS oil platform Gina in August.................... 20 

Figure 7. Total number and vertical distribution of fishes on 30 August 2003 ....... 21 

Figure 8. Recruitment per unit area of habitat......................................................... 22 

Figure 9. Total number of blackeye goby tagged from Sept to Jan ........................ 25 

Figure 10. The size-frequency distribution of blackeye goby at OP Gina............... 26 

Figure 11. The size-frequency distribution of blackeye goby at Chief Reef ........... 27 

Figure 12. The size-frequency distribution of blackeye goby at Potato Reef.......... 28 

Figure 13. The size-frequency distribution of blackeye goby at Orizaba Reef ....... 29 

Figure 14. Weight-length relationship from wet weights ........................................ 30 

Figure 15. Weight-length relationship from 70% ETOH ........................................ 31 

Figure 16. Mean number of eggs per clutch ............................................................ 32 

Figure 17. Mean area and density of egg masses..................................................... 32 

Figure 18. Relationship between egg density and surface area ............................... 33 

Figure 19. Fate of tethered gobies............................................................................ 35 

Figure 20. Length frequency of gobies tethered ..................................................... 36 

 
Relative Importance of POCS Oil Platforms 

1

FINAL TECHNICAL SUMMARY 

STUDY TITLE: Relative importance of POCS oil platforms on the regional population 

dynamics of reef fishes in the Eastern Santa Barbara Channel 

REPORT TITLE: Relative contribution of POCS oil platforms to regional population 

dynamics of a model reef fish, the blackeye goby Rhinogobiops nicholsii, in the Eastern Santa 

Barbara Channel 

CONTRACT NUMBER: 14-35-0001-31063 

SPONSORING OCS REGION: Pacific 

APPLICABLE PLANNING AREA(S): Southern California 

FISCAL YEAR(S) OF PROJECT FUNDING: FY 02, FY 03 

COMPLETION DATE OF REPORT: November 2006 

COST(S): FY 02-03: $112,348 

CUMULATIVE PROJECT COST: $112,348 

PROJECT MANAGER: Russell J. Schmitt 

ADDRESS: Coastal Research Center, Marine Science Institute, University of California, Santa 

Barbara, CA 93106-6150 

PRINCIPAL INVESTIGATORS: Hunter S. Lenihan and Andrew J. Brooks 

ADDRESSES: Bren School of Environmental Science and Management, University of 

California, Santa Barbara, CA 93106-5131; Marine Science Institute, University of California, 

Santa Barbara, CA 93106 

BACKGROUND: 

Determining the effect of each decommissioning alternative on the regional production of reefassociated fish species is the primary ecological question concerning the decommissioning of the 

POCS offshore oil platforms (Holbrook et al. 2000). Surveys of the 27 platforms in California 

waters reveal that they harbor rich but highly variable assemblages of reef-associated fishes and 

invertebrates (Love et al. 1999; Page et al. 1999). However, the total habitat area provided by 

platforms is relatively small in relation to the regional availability of natural reef habitat thus 

suggesting that platforms may have little influence on population dynamics at regional scales. 

Nevertheless, platforms may negatively influence the regional population dynamics if they 

attract individuals from more suitable habitat, or they may enhance populations in areas that have 

relatively little natural habitat and where the structures have positive influences on demographic 
Final Technical Summary – Lenihan and Brooks 

2

processes, including individual growth, reproduction, and survival. Regional stocks of most 

reef-associated species are composed of local populations that are linked together through the 

dispersal of larvae and/or the migration of adults or juveniles (Lipcius et al. 1997; Lenihan et al. 

2001). Oil platforms most likely enhance regional population abundance by acting as (1) selfmaintained local populations, or (2) source populations that continually supply individuals to 

less-productive sink populations. 

OBJECTIVES: 

Our objectives were to test whether POCS oil platforms in the Eastern Santa Barbara Channel 

influence the regional population abundance of a model reef fish, the blackeye goby 

Rhinogobiops nicholsii, through examination of the relative contribution of one POCS oil 

platform, OP Gina, and natural rocky reefs. We examined the population demographics of the 

blackeye goby because this species is the most common demersal fish found on oil platforms 

(Carr et al. 1999), provides the best model species to examine population dynamics, and as a 

very common, small benthic species plays an important role in reef food webs as both a predator 

on zooplankton and benthic invertebrates (e.g., amphipods, isopods, and polychaete worms) and 

prey to rockfish, kelp bass, and other groundfish species. Blackeye goby utilize a limited amount 

of benthic habitat, have limited migratory behavior as adults, closely guard non-cryptic nests, 

and produce eggs that can be used to quantify fecundity. Therefore, it was possible to quantify 

key demographic features (reproductive output, recruitment, deaths, immigration, and 

emigration) necessary to relative contributions to regional population dynamics as they may vary 

on POCS oil platforms and natural rocky reef habitat. 

 

If oil platforms influence the population dynamics of a fish species on a regional scale, this effect 

can be accurately estimated for blackeye goby in the Eastern Santa Barbara Channel (ESBC). 

This species inhabit most of the 13 oil platforms in the area (Carr et al. 1999). There are also 

relatively few local natural reefs in the ESBC within the normal range of movement of adult 

blackeye goby, or that are hydrographically connected with local oil platforms (Harms and 

Winant 1998). Consequently, populations of goby inhabiting ESBC platforms are either selfmaintained on individual or proximal platforms, or are subsidized by, or subsidize natural reefs 

through limited immigration/emigration. They can also be connected through larval transport as 

blackeye goby has pelagic larvae that spend a relatively short time in the water column during 

dispersal. Therefore, identifying connectivity between local populations of blackeye goby will 

entail understanding hydrographic connectivity between habitats, larval transport processes, and 

adult/juvenile migration (Hench et al. 2001). 

Understanding the population dynamics of blackeye goby on ESBC POCS oil platforms and 

natural reefs, and estimating whether platforms influence regional population dynamics through 

supply of "excess production", are a means of estimating the relative contribution of oil 

platforms and natural rocky reefs. It also provides the means of executing the three major 

research objectives proposed by Holbrook et al (2000): (1) assessing the quality of platforms as 

reef habitat, (2) estimating connectivity between local populations, and (3) modeling effects on 

the regional population of maintaining, moving, removing, or topping the oil rigs. Our specific 

objectives were to (1) quantify population demographic processes (abundance, growth rates, 

births, mortality, immigration, and emigration) of blackeye goby through sampling using scuba; 
Relative Importance of POCS Oil Platforms 

3

and (2) assess the relative contribution of an oil platform and natural reefs as a means of 

estimating the influence of platforms on the regional population dynamics of a reef fish.

DESCRIPTION: 

Overview: Between May 2003 and November 2004, we made 90 total trips to oil platform Gina 

in the eastern Santa Barabara Channel and three natural rocky reef control sites at Santa Cruz 

Island, Orizaba Reef, Chief Reef, and Potato Reef. At each site we measured the following life 

history parameters of the blackeye goby (Rhinogobiops nicholsii), egg production, recruitment, 

abundance of adults, and population size structure. Additionally, we conducted tethering 

experiments to estimate mortality from predation, and a tag-recapture study to track mortality 

and immigration and emigration of individuals from the study areas. Finally, we collected 

individuals from all sites and removed otoliths (sagittae and lapillae) for size-at-age and 

microchemical analyses. The methods employed for each of these procedures is described in 

detail below. 

We examined the population dynamics of blackeye gobies at four locations, POCS oil platform 

Gina (OP Gina) and three natural, subtidal rocky reefs located on Santa Cruz Island (SCI). We 

selected OP Gina as our oil platform treatment because it is the only platform located at a water 

depth (31 m) at which scuba divers can dive to the seafloor and work for acceptable lengths of 

time (>10 min) safely. The seafloor around all other platforms in the SB Channel is too deep for 

diving, even with Nitrox gas. Natural reefs were selected on SCI because they were the reefs that 

were nearest to OP Gina, were located at similar water depths (20-30 m), and were inhabited by 

blackeye goby. 

Demographic study: Our first objective in the field was to identify the most abundant benthic 

fish species at OP Gina. We counted the total numbers of individuals of all species encountered 

on four transects (30 m long x 2 m wide) placed around OP Gina in June, July, and August 2003. 

We also counted on the same dates all fishes located in the water column (from the seafloor to 

the surface) within the footprint of the platform from the bottom to the surface of the water on 

the same dates. We found the blackeye goby was by far the most abundant species at OP Gina. 

Survey dives made during the same period at SCI confirmed that this species was also one of the 

most abundant species at our control sites. Therefore, we concentrated our effort throughout the 

project on this species. We had initially planned to study a surf perch species and the painted 

greenling but saw only a few individuals at all sites, and had substantial difficulty in capturing 

them in preliminary fish tagging trials. 

To test whether the abundance of gobies varied between OP Gina and natural reef control sites, 

divers counted the abundance of adults, juveniles, and young-of-the-year (YOY) along four 

replicate transects (30 m x 2 m) placed along the reef/sand interface at each site. Our counts of 

YOY provided an estimate of goby recruitment. Transect counts were made in September, 

October, and November 2003, and January and June 2004. 

Population structure, immigration, and emigration: We conducted monthly tagging of 

blackeye goby at each site during September, October, and November 2003, and January 2004 to 

test whether rates of population size structure, mortality, survival, immigration, and emigration 
Final Technical Summary – Lenihan and Brooks 

4

varied among natural reefs and OP Gina. Gobies were captured by divers, brought to the surface, 

measured, and tagged with a small subcutaneous injection of latex paint placed near the dorsal 

fin. Gobies were then released in the general area (within 2-5 meters) from which they were 

caught. Divers remained with the gobies upon release and chased away potential predators until 

the gobies regained awareness of their surroundings and exhibited what appeared to be normal 

behavior, mainly using the shelly bottom as refuge. A different color tag was applied each 

month, and colors were easily visible and distinguishable underwater at all our sites. 

Surveys for tagged fish were conducted September, October, November, and December 2003, 

and January, June, and July 2004. Length-frequency data recorded during tagging were used to 

construct adult population structure histograms for each site. Estimates of mortality, growth, 

immigration, and emigration are generated from the number of individuals tagged and recovered 

at each site during each sampling period. 

Fecundity: To test whether fecundity of blackeye gobies varied among natural reefs and OP 

Gina, we estimated the total number of eggs produced by individual fishes from each site. In 

April 2004, we collected egg masses of our target species from platform Gina (n=15), Chief Reef 

(n=11), Orizaba Reef (n=11), and from two depths at Potato Reef (n=11 from 20 m, and n=11 

from 30 m). This species deposit egg masses on the undersides of small boulders and/or shell 

fragments, which allowed for collection of entire egg clutches from an individual female. Eggs 

were collected by divers who non-destructively flipped loose pieces of material on the seafloor 

that appeared to be guarded by an adult goby. Samples were then placed in a cooler filled with 

seawater and returned immediately to flow-through seawater aquaria at the UC Santa Barbara’s 

Marine Science Institute. Estimates of egg mass area, egg density, and total number of eggs per 

clutch (fecundity) were then determined for each location. We examined each egg mass for data 

yielding a mean density of eggs (eggs/cm2

) and total number of eggs, which was calculated by 

multiplying the area of an egg mass by the mean density. 

Predation mortality of blackeye goby: To test whether rates of predation on gobies varied 

among natural reefs and OP Gina, we conducted a tethering experiment in which live, adult 

blackeye gobies were attached to lines and their fate was followed by divers. We deployed three 

replicate lines (33 m long) to which we tethered 10 gobies (10 gobies x 3 replicate lines = 30 

total gobies per site). The long-lines were placed along our “permanent” survey transects. We 

conducted this experiment at the conclusion of our study from 10-17 July 2004 to avoid impacts 

to our study area). After long-lines were deployed and inspected, gobies were captured and 

brought to the surface as described above (Tagging). Gobies were measured and hooked through 

the base of the dorsal fin with a small, barbed live-bait type fish hook connected to 1 m of 4lb 

monofilament with a size 7 (15 lb) snap swivel attached to the other end. The diver then released 

the goby from the plastic bottle and noted the loop location and bottle number of each fish. 

Gobies were tethered to the long-lines and sampled by divers after 1 hour. Tethered individuals 

were scored as “goby present”, “hook only present”, or “snapped”. Predators hooked on the goby 

lines were recorded and released. To address the possibility that “hook only present” individuals 

may have shaken off the hook without being preyed upon, we ran a control study at in which 

divers monitored the longlines continually. The depths at our study sites were prohibitive to 

prolonged bottom times, and so this study was conducted at Naples reef off of Santa Barbara, 

CA, at a depth of 12 meters. 
Relative Importance of POCS Oil Platforms 

5

Age and Growth estimates: To test whether growth rates of blackeye goby varied among 

natural reefs and OP Gina, we collected 60 individuals from each site and dissected the saggitae 

and lappillae (otoliths) for age-at-size and microchemical analyses. The collection process was as 

described above (Tagging) with the exception that fish were measured and then placed in ethanol 

immediately upon capture. Weight-length measurements were made from the 60 fish sacrificed 

for otiliths. Weights were taken prior to the removal of otoliths but after they were stored in 70% 

ETOH for 1-2 weeks. 

Mircochemistry of otoliths: We have yet to conduct this additional aspect of our study because 

we seek additional funding for the relatively expensive and time consuming analysis. 

Population modeling: We are in the process of modeling the population dynamics of blackeye 

goby and providing predictions for the regional-scale impacts of the five proposed 

decommissioning methods. We will undertake and complete our modeling component when we 

complete preparation of our population demographics paper. 

Summary: We expect that we will generate a total of four publications from our study: (1) a 

population demographics paper comparing a POCS oil platform and natural reef populations of 

blackeye goby, (2) a regional population dynamics modeling paper, (3) and age-growth analysis, 

and (4) potentially a paper that reports use of otolith microchemistry to analyze temporal patterns 

of habitat utilization by populations of gobies inhabiting POCS Gina and natural rocky reef 

control sites. 

 

SIGNIFICANT CONCLUSIONS: 

We assembled a thorough and spatially and temporally comprehensive field-based demographic 

data set of blackeye goby populations OP Gina and three natural rocky reefs located on the north 

shore Santa Cruz Island in the ESBC. The natural reefs we used were those located closest in 

space to OP Gina that also were inhabited by the blackeye goby. Our results provide information 

that can be used to estimate the relative contribution of goby populations from OP Gina and the 

natural reefs to the regional population pool of this species. 

We found that abundance did not differ among the oil platform and natural reefs; that 

recruitment was slightly lower at OP Gina than at natural reefs, that the size structure of the 

population was greater at Op Gina than natural reefs; that the differences in size structure may be 

explained by reduced predation mortality; that fecundity may be relatively low OP Gina OP, but 

that fish may live longer and therefore produce more population output over the long-term. 

Our general finding is that populations of blackeye goby at OP Gina do not make a substantial 

contribution to the regional stock of blackeye goby, indicating that OP Gina’s removal, or 

modification based on other decommissioning strategies, would have little effect on the regional 

abundance and population dynamics of this species. Because this species is found on many other 

POCS oil platforms in the ESBC, our findings are relevant to decommissioning strategies in 

general. We predict that removal or in-situ modification of a platform will not have an important 

influence on regional populations of this model benthic species. OP Gina is not an important 

population source or sink. Therefore we also predict that (1) if the platforms were to remain in 
Final Technical Summary – Lenihan and Brooks 

6

place it would not have a negative impact on the regional populations of blackeye goby, and (2) 

that OP Gina should be not considered a potential marine reserve based on this ecologically 

relevant species. 

STUDY PRODUCTS: 

Published work 

Lenihan, H.S., A.J. Brooks, and M.C. Kay. In preparation. Relative contribution of POCS oil 

platforms to regional population dynamics of a model reef fish, the blackeye goby 

Rhinogobiops nicholsii, in the Eastern Santa Barbara Channel. Target: Ecological 

Applications. 

A.J. Brooks, H.S. Lenihan, and M.C. Kay. In preparation. Age and growth of the blackeye goby 

Rhinogobiops nicholsii, in the Eastern Santa Barbara Channel. Target: Environmental 

Biology of Fishes. 

Presentations 

H.S. Lenihan, A. Brooks, and M.C. Kay. 2005. Relative Importance of POCS Oil Platforms on 

the Population Dynamics of Reef Fishes in the Eastern Santa Barbara Channel. Bren 

School, UCSB. October, 2005. 

H.S. Lenihan. 2005. Population ecology and problem solving in the marine environment. Bren 

School, UCSB. December 2005. 

H.S. Lenihan. 2006. Population source-sink dynamics and POCS oil platform decommissioning. 

March, 2006. 
Relative Importance of POCS Oil Platforms

7

FINAL STUDY REPORT 

Relative contribution of POCS oil platforms to regional population dynamics of a model 

reef fish, the blackeye goby Rhinogobiops nicholsii, in the Eastern Santa Barbara Channel

Hunter S. Lenihan and Matthew C. Kay 

Bren School of Environmental Science and Management, University of California, Santa 

Barbara, CA 93106-5131 

Andrew J. Brooks 

Marine Science Institute, University of California, Santa Barbara, CA 93106 

9 July 2006 
Final Study Report – Lenihan and Brooks 

8

INTRODUCTION 

Ecological impact assessment has advanced in recent years due the integration of powerful 

ecological tools, including BACIPS impact analyses, oceanographic modeling to track 

population connectivity and manipulative experiments borrowed from marine field and 

population ecologists (Connell 1960; Schmitt and Holbrook 1996). Population ecology has 

made an especially important contribution because the models and analytical methods used to 

explore dynamical and often complex process regulating populations are also well suited to 

assessing impacts of human activities (Schmitt and Osenberg 1996). Here we address a pressing 

applied question concerning temperate latitude reef fishes and the management of Pacific 

Offshore-Continental Shelf (POCS) oil platforms in southern California. The effective 

management of oil platforms is critical to the ecosystems in which they operate because they are 

artificial reefs that are both a source of marine pollution and physical disturbance, and habitat for 

many marine species. By employing a quantitatively rich population biological approach, we not 

only generate ideas relevant for oil platform management, but also provide a general model for 

conducting field-based ecological assessments at a regional spatial scale. 

Substantial debate surrounds the future of POCS oil platforms, especially concerning how they 

should be decommissioned once they have reached the end of their productive lifetimes. Five 

potential methods are under consideration, leaving as they are, removing them completely, 

leaving them in place but cutting off top 30 m so that they are not a navigational hazard, toppling 

them in place, and disposing of them elsewhere, including into deep water. Determining the 

effects of decommissioning alternatives on the regional production of reef-associated fish species 

is a primary ecological question concerning future management of the POCS offshore oil 

platforms (Holbrook et al. 2000). Evidence has amassed indicating platforms are inhabited by 

many marine organisms including economically valuable rockfishes and other groundfishes. 

These data have ignited debate concerning the most environmentally and economically 

appropriate options for decommissioning. Many consider high biological production of 

platforms as justification for avoiding the expenditure of large sums of industry resources 

necessary for decommissioning. Others argue that the industry is responsible for removing the 

structures no matter the cost because that was a condition of the original lease policy. Holbrook 

et al. (2000) suggest that decisions on decommission should be made based at least in part on the 

best information concerning the ecological impacts of various decommissioning strategies. 

Little question remains as to whether POCS platforms are productive. Surveys of the 27 

platforms in California waters reveal that they harbor rich but highly variable assemblages of 

reef-associated fishes and invertebrates (Love et al. 1999; Page et al. 1999). However, Holbrook 

et al. (200)) suggest that high productivity on individual platforms does not necessary translate 

into high productivity and ecological enhancement at the regional or ecosystem level. They 

point out that the total habitat area provided by platforms is relatively small in relation to the 

regional availability of natural reef habitat thus suggesting that platforms may contributed very 

little to the regional abundance and distribution of marine organisms. Platforms also may 

negatively influence the regional population dynamics of a species if they attract individuals 

from more suitable habitat and, as a result, lead to significant reductions in demographic 

processes such as recruitment, growth, survival, or reproductive output. As platforms provide 

little reef habitat relative to natural reefs, significant negative impacts at a regional scale are 
Relative Importance of POCS Oil Platforms

9

unlikely, unless the platforms act as major population sinks. In contrast, platforms may enhance 

populations in areas that have relatively little natural habitat and where the structures have 

positive influences on demographic processes. Regional stocks of most reef-associated species 

are composed of local populations that are linked together through the dispersal of larvae and/or 

the migration of adults or juveniles (e.g., Lipcius et al. 1997; Lenihan et al. 2001). Oil platforms 

most likely enhance regional population abundances to some degree by acting as (1) selfmaintained local populations, and/or (2) source populations that supply individuals to other 

populations within the region. Thus, the ecologically relevant question is not whether platforms 

act as sources or sinks, but rather what is the relative contribution to regional populations in 

terms of numbers or biomass of individuals produced by populations associated with oil 

platforms when compared with the contribution made by populations associated with areas of 

natural habitat. 

We examined the population dynamics of a model reef fish, the blackeye goby (Rhinogobiops 

nicholsii), that commonly is found on both natural reefs and platforms. By estimating the 

demographic rates of populations on natural reef and an oil platform, we generate the 

information necessary to estimate the relative contribution of POCS oil platforms and natural 

rocky reefs at a regional scale. We also lay the grounds for quantitatively assessing the potential 

effects of the various decommissioning strategies and provide the data necessary for a 

meaningful ecological risk assessment model of future POCS platform management options. 

Here we provide the first step in that process, a rigorous examination of the population 

demographics of a model reef fish on one POCS oil platforms, Gina (OP Gina), located in the 

eastern Santa Barbara Channel (ESBC) and a nearby set of natural rocky reefs located on Santa 

Cruz Island (Figure 1). 

Figure 1. Site map of study locations, POCS Oil Platform Gina (OP Gina), and three natural subtidal rocky reefs on 

Santa Cruz Island. 
Final Study Report – Lenihan and Brooks 

10

We selected the blackeye goby as our model reef fish because it is one of the most common 

species on platforms (Carr et al. 1999), is a good species with which to examine population 

dynamics, and as a very common benthic species plays an important role in reef food webs as 

both a predator on zooplankton and benthic invertebrates (e.g., amphipods, isopods, and 

polychaete worms) and prey for larger rockfish and other groundfish species. Blackeye gobies 

are a territorial benthic species, have limited migratory behavior as adults, closely guard noncryptic nests, and produce benthic egg masses that can be used to quantify fecundity. Therefore, 

it is possible to quantify some of the key demographic features (reproductive output, recruitment, 

deaths, immigration, and emigration) necessary to identify population dynamics as they may 

vary on POCS oil platforms and natural rocky reef habitat (Steel 2001). Blackeye gobies are 

found in water depths to 150 m in the Santa Barbara Channel, including the base of POCS oil 

platform (OP Gina); the only platforms that is located in a water depth (30 m) that is accessible 

to scuba divers for long enough periods of time to conduct meaningful population ecological 

research. 

The study reported here is the first step in exploring source-sink population dynamics among 

platforms and natural reefs (Holt 1985; Pulliam 1988; Crowder et al. 2000). Understanding the 

population dynamics of the blackeye goby on ESBC POCS oil platforms and local reefs, and 

estimating whether platforms influence regional population dynamics through supply of "excess 

production", are also means of executing the three major research objectives proposed by 

Holbrook et al (2000): (1) assessing the quality of platforms as reef habitat, (2) estimating 

connectivity between local populations, and (3) modeling effects on the regional population of 

maintaining, moving, removing, or topping the oil rigs. 

Our specific objectives were to quantify the demographic contributions (abundance, growth 

rates, births, mortality, immigration, and emigration) of the blackeye goby on POCS oil platform 

Gina and three natural rocky reefs in the ESBC through sampling using scuba. We will use the 

models to estimate the influence of platforms on regional population dynamics, and estimate the 

effects of maintaining, moving, removing or topping the platforms using sensitivity analyses. 

METHODS AND MATERIALS 

Between May 2003 and November 2004, we made a total of 90 trips to oil platform Gina in the 

eastern Santa Barbara Channel and three natural, rocky reef control sites at Santa Cruz Island; 

Orizaba Reef, Chief Reef, and Potato Reef. At each site, we measured the following life history 

parameters of the blackeye goby, egg production, recruitment, abundance of adults, and 

population size structure. Additionally, we conducted tethering experiments to estimate 

mortality from predation, and a tag-recapture study to track mortality and immigration and 

emigration of individuals from the study areas. Finally, we collected individuals from all sites 

and removed otoliths (sagittae and lapillae) for size-at-age and micro-chemical analyses. The 

methods employed for each of these procedures is described in detail below. 

Site Descriptions 

We examined the population dynamics of blackeye gobies at four locations, POCS oil platform 

Gina and three natural, subtidal rocky reefs located on Santa Cruz Island. We selected OP Gina 
Relative Importance of POCS Oil Platforms

11

as our oil platform treatment because it is the only platform located at a water depth (31 m) at 

which scuba divers can safely dive to the seafloor and work for acceptable lengths of time (>10 

min). Natural reefs were selected on SCI based on their proximity to OP Gina, similar water 

depths (20-30 m), and the occurrence of populations of the blackeye goby. 

POCS Oil Platform Gina 

OP Gina (34O 07’ N; 119O 16’ W) is located approximately 6.5 km offshore from the entrance to 

Channel Islands Harbor in Oxnard, California. Compared with other oil platforms in the Santa 

Barbara Channel, the seafloor footprint of OP Gina is relatively small (~30 m x 40 m) and 

located in shallow water (~31 m deep). Primary space on the support pilings is dominated by the 

mussel Mytilus californianus, and the scallop Crassoderma giganteum, barnacle Balanus 

nubilus, and anenome Corynactis californica are also common. Fish species that we commonly 

observed associated with the platform’s structural members include (in decreasing order of 

abundance): kelp bass (Paralabrax clathratus), cabezon (Scorpaenichthys marmatus), painted 

greenling (Oxylebius pictus), pile surfperch (Damalichthys vacca), rubberlip surfperch 

(Damalichthys toxotes) and ocean whitefish (Caulolatilus princeps). 

The seafloor directly beneath OP Gina is covered by a large shell mound composed of live and 

dead mussels (M. californianus) that have accumulated since the platform’s installation in 1980. 

The “shell mound” reaches a high point ~ 2 m tall (i.e., ~29 m beneath the sea surface) near the 

center of the OP Gina footprint, and gradually tapers into the surrounding sandy seafloor in ~31 

m water depth. The mound is generally circular in shape, 50-60 m in diameter, and there is 

100% cover of mussel shells directly below OP Gina. The percent cover of shells decreases 

rapidly so that there are only a few scattered shells on the sandy substrate only 6-8 m away 

beyond the platforms foot print. The shell reef supports large populations of the sea stars 

(Pisaster spp. and Asterina miniata), octopus (Octopus bimaculatus), crabs, and small infuanal 

organisms including polycheate worms and amphipods. We observed several fish species 

associated with this unique reef habitat, including (in decreasing order of abundance) blackeye 

goby (R. nicholsii), cabezon (S. marmatus), painted greenling (O. pictus), C-O turbot 

(Plueronichthys coenosus), fingeheads (Neoclinus spp.), and recruits and young-of-the-year 

(YOY) of numberous species of rockfish (Sebastes spp.). We conducted our work with R. 

nicholsii at the shell mound/sand interface along the eastern side of OP Gina. 

Control Sites- Natural Rocky Reefs at Santa Cruz Island 

Control sites were selected to mimic the physical and biological characteristics of OP Gina, 

especially in terms of water depth, total area and quality of blackeye goby habitat, physical 

structure, the relative isolation in space from other reefs, and proximity to platform Gina, as well 

as the composition and structure of fish and invertebrate assemblages. We intensively surveyed 

the coastlines of the mainland, Anacapa Island, and Santa Cruz Island before selecting our 

control sites. The three sites at Santa Cruz Island exhibited the highest level of biological and 

physical similarity to OP Gina. 

The three sites we selected, Chief, Potato and Orizaba reefs, were submerged rocky reefs 

associated with submerged pinnacles (Chief and Potato) and an islet (Orizaba) located north 

shore of Santa Cruz Island (Figure 1). Each reef was surrounded by sandy seafloor such that 

there was no corridor of rocky habitat linking the reefs to other reefs onshore on Santa Cruz 
Final Study Report – Lenihan and Brooks 

12

Island. We conducted all surveys and experiments at the interface of the seaward edge of each 

reef and the sandy seafloor at water depths from 20-30 m. All locations were at least 40 m away 

from other goby or rocky reef habitat (Table 1). 

Table 1. Site characteristics for Gina and three control sites at Santa Cruz Island.

Site Name GPS Position Water 

depth 

Highest 

vertical 

point 

Distance 

to shore 

Conspicuous / unique 

benthic features 

OP Gina 34O 07’ N 

119O 16’ W 

30.5 m 

(100’) 

Above 

surface 

6.5 km 

(3.6 nm) 

Shell mound 

Chief Reef 34O 02.555’ N 

119O 31.855’ W 

19.8 m 

(65’) 

8.5 m 

(28’) 

100 m Uneven rocky bottom, 

little mussel shell 

present, abundant 

Ophiothrix spiculata, 

Muricea spp.

Potato 34O 02.945’ N 

119O 35.880’ W 

27.7 m 

(91’) 

4.3 m 

(14’) 

170 m Steep vertical walls, 

mussel shell present 

Orizaba 34O 02.880’ N 

119O 43.353’ W 

19.8 m 

(65’) 

Above 

surface 

40 m Steep vertical walls, 

mussel shell present 

Invertebrate assemblages at each control site were similar to each other and typical of the Santa 

Barbara Channel. Fish that we commonly observed at sampling locations at each site included 

(in order of decreasing abundance), Blackeye goby (R. nicholsii), California sheephead 

(Semicossyphus pulcher), kelp bass (P. clathratus), pile surfperch (D. vacca), black surfperch 

(Embiotica jacksoni) rockfish (Sebastes spp.), cabezon (S. marmatus) and ocean whitefish (C. 

princeps). Other species common to the region were present but occurred higher in the water 

column or were seen much less regularly. 

Despite their similarities, the control sites were unique in several important ways. The reef/sand 

interface at Chief Reef contained isolated, small (~0.1-1.0 m3) boulders on the sandy seafloor, 

and this area supported extremely high densities of the brittle stars Ophiothrix spiculata. Neither 

feature was present at Potato or Orizaba Reefs. Potato Reef was physically the most similar to 

Platform Gina due to its depth, steep walls, and the high density of mussel distributed on the 

seafloor (see below). 

We accessed all sites using a 22’ UCSB research vessel that was launched from Santa Barbara 

(SCI sites) or Channel Islands Harbor (OP Gina). At SCI sites, we anchored at prerecorded GPS 

locations (Table 1). At OP Gina divers were deployed from an unanchored (“live”) boat. Divers 

descended the anchor line/platform pilings and located permanent buoys that marked sampling 

locations at each site. 

Abundance and recruitment 

Our first objective in the field was to identify the most abundant benthic fish species at OP Gina. 

We estimated the total numbers of individuals of all species encountered on four transects (30 m 

long x 2 m wide) placed haphazardly around OP Gina in June, July, and August 2003. We also 

counted on the same dates all fishes located in the water column (from the seafloor to the 

surface) within the foot print of the platform from the bottom to the surface of the water. We 
Relative Importance of POCS Oil Platforms

13

found the blackeye goby was by far the most abundant species at OP Gina. Survey dives made 

during the same period at SCI confirmed that blackeye gobies were also one of the most 

abundant species at our control sites. Therefore, we concentrated our effort throughout the 

project on this species. We had initially planned to study a surf perch species and the painted 

greenling but saw only a few individuals at all sites, and had substantial difficulty in capturing 

them in preliminary fish tagging trials. 

To test whether the abundance of gobies varied between OP Gina and natural reef control sites, 

divers estimated the abundance of adults, juveniles, and young-of-the-year (YOY) along four 

replicate transects (30 m x 2 m) placed along the reef/sand interface at each site. Our counts of 

YOY provided an estimate of goby recruitment. Transect counts were made in September, 

October, and November 2003, and January and June 2004. On each transect, two divers attached 

a transect line to a fixed marker and spooled the tape out as they swam along the interface. Each 

diver recorded all R. nicholsii encountered in a 30 m x 1 m swath. Data from both divers on a 

single transect were later pooled to form 1 replicate. This procedure was repeated at each site 

along fixed markers deployed to ensure that the same areas were sampled through time 

(“permanent” transects). Gobies smaller than 1.5 cm were recorded as YOY, and thus 

considered recruits. 

Population structure, immigration, and emigration 

We conducted monthly tagging of blackeye goby at each site during September, October, and 

November 2003, and January 2004 to test whether rates of mortality, survival, immigration, and 

emigration varied among natural reefs and OP Gina. At each site, divers used aquarium dip nets 

to capture individual gobies that were then transferred to larger holding pens on the seafloor. 

Holding pens were constructed of 1/16” nylon mesh (Memphis Net & Twine) fitted with internal 

wire frames (1 per pen) that were circular and measured 28 cm diameter x 15 cm tall. These 

frames protected captured gobies from abrasion and impacts associated with transport. 

When ascending, divers attached the holding pens to the bottom of a weighted line that hung 

from the boat at a depth of 8 m. This allowed the swim bladders of the captured gobies to 

equilibrate as divers surfaced and entered the boat. After 10-20 minutes at 8 m, the gobies were 

retrieved, removed from the pens, and placed in a 48 L cooler filled with fresh seawater. The 

cooler was partially drained and refilled with fresh seawater every 10-15 minutes throughout the 

tagging process. 

All gobies brought to the surface were measured and tagged with a small subcutaneous injection 

of latex paint placed near the dorsal fin. We used Liquitex® brand acrylic paint injected through 

a 1 ml tuberculin slip-tip syringe fitted with a 30G1/2 Precisionglide® needle (Becton, 

Dickinson, and Company). Individuals were handled in aquarium dip nets during tagging and 

returned immediately to the cooler. When all fish in the cooler were tagged, they were placed in 

the holding pens and returned to the seafloor by divers. Gobies were released in the general area 

(within 2-5 meters) from which they were caught. Divers remained with the gobies upon release 

and chased away potential predators until the gobies regained awareness of their surroundings 

and exhibited what appeared to be normal behavior, mainly using the shelly bottom as refuge. A 

different color tag was applied each month, and colors were easily visible and distinguishable 

underwater at all our sites. 
Final Study Report – Lenihan and Brooks 

14

Surveys for tagged fish were conducted September, October, November, and December 2003, 

and January, June, and July 2004. Surveys were conducted within 3-7 days after tagging at a 

given site, and methods used were the same as those used to estimate abundance. Additionally, 

we searched areas immediately adjacent and further outside of our permanent transects to sample 

for movement/emigration of individuals from our study transects. Length-frequency data 

recorded during tagging were used to construct adult population structure histograms for each 

site. Estimates of mortality, growth, immigration, and emigration are generated from the number 

of individuals tagged and recovered at each site during each sampling period. 

Fecundity 

To test whether fecundity of blackeye gobies varied among natural reefs and OP Gina, we 

estimated the total number of eggs produced by individual fishes from each site. In April 2004, 

we collected egg masses of blackeye gobies from platform Gina (n=15), Chief Reef (n=11), 

Orizaba Reef (n=11), and from two depths at Potato Reef (n=11 from 20 m, and n=11 from 30 

m). This species deposits egg masses on the undersides of small boulders and/or shell fragments 

that allowed for collection of entire egg clutches from an individual female. Males guard the egg 

masses. Eggs were collected at OP Gina from mussel shells, but egg masses from the Santa Cruz 

Island sites were found on shells of mussel shells, scallop (Crassoderma giganteu) shells, and 

small boulders. 

Eggs were collected by divers who non-destructively flipped loose pieces of material on the 

seafloor that appeared to be guarded by an adult goby. Egg masses deposited entirely on 

collectable substrata were placed in individually labeled Ziploc® bags and brought to the surface. 

Once on the boat, samples were placed in a cooler filled with seawater and returned immediately 

to flow-through seawater aquaria at the UC Santa Barbara’s Marine Science Institute. 

Estimates of egg mass area, egg density, and total number of eggs per clutch (fecundity) were 

determined as follows. Each egg mass (attached to substratum) was placed in a 1L finger bowl 

with the egg mass facing upwards. An acetate paper tracing of the egg mass was cut to fit the 

shape of the mass. This tracing was then weighed against an acetate standard of known weight 

and area to calculate egg mass area. Next, an acetate paper square of known area (1cm2

) was 

placed haphazardly within the egg mass and all eggs within the square were counted through a 

dissecting microscope. Four such replicate counts were made for each egg mass, thus yielding a 

mean density of eggs (eggs/cm2

). Total number of eggs was calculated by multiplying the area 

of an egg mass by the mean density. 

Predation mortality of blackeye goby 

To test whether rates of predation on gobies varied among natural reefs and OP Gina, we 

conducted a tethering experiment in which live, adult blackeye gobies were attached to lines and 

their fates followed by divers. We deployed three replicate lines (33 m long) to which we 

tethered 10 gobies (10 gobies x 3 replicate lines = 30 total gobies per site). Long-lines were 

constructed of 100 lb monofilament line with small loops spaced every 3 m. The long-lines were 

placed along our “permanent” survey transects. We conducted this experiment at the conclusion 

of our study from 10-17 July 2004 to avoid impacts to our study area). Long-lines were 

deployed along sets of 0.5 m tall risers that lifted the lines off the seafloor in an effort to limit 

goby entanglement. 
Relative Importance of POCS Oil Platforms

15

After long-lines were deployed and inspected, gobies were captured and brought to the surface as 

described above (Tagging). Gobies were measured and hooked through the base of the dorsal fin 

with a small, barbed live-bait type fish hook connected to 1 m of 4lb monofilament with a size 7 

(15 lb) snap swivel attached to the other end. Each hooked goby was then placed into an 

individually labeled 1⁄2 liter plastic wide-mouth bottle such that the 4 lb monofilament trailed 

through a slit in the top of the bottle. The remaining <1 meter of 4lb monofilament and snap 

swivel were wrapped around a rubber stopper and attached to the outside of the bottle with a 

rubber band, and the bottle was returned to the cooler. 

When all gobies were hooked and ready for deployment, divers descended to the long-lines with 

the plastic bottle/goby assemblies. At each loop in the long-line, a diver first unspooled the 4lb 

monofilament and attached the snap swivel to the loop. The diver then released the goby from 

the plastic bottle and noted the loop location and bottle number of each fish. Gobies were 

tethered to the long-lines and sampled by divers after 1 hour. Tethered individuals were scored 

as “goby present”, “hook only present”, or “snapped”. Predators hooked on the goby lines were 

recorded and released. 

To address the possibility that “hook only present” individuals may have shaken off the hook 

without being preyed upon, we conducted a control study in which divers monitored the 

longlines continually. The depths at our study sites prohibited prolonged bottom times, and so 

this study was conducted at Naples reef off of Santa Barbara, CA, in a depth of 12 meters. 

Age and Growth estimates 

To test whether growth rates of blackeye gobies varied among natural reefs and OP Gina, we 

collected 60 individuals from each site and dissected the saggitae and lappillae (otoliths) for ageat-size and microchemical analyses. The collection process was as described above (Tagging) 

with the exception that fish were measured and then placed in ethanol immediately upon capture. 

At one site, fish were weighed prior to being placed in ethanol, and were re-weighed after 1 

week exposure to ethanol. The difference in weights was used to correct for wet weights. Fish 

which were placed in ethanol prior to being weighed. Ageing of the otoliths has proven 

problematic to date and we developing an avenue for microchemical analyses. Weight-length 

measurements were made from the 60 fish sacrificed for otoliths. Weights were taken prior to the 

removal of otoliths but after they were stored in 70% ETOH for 1-2 weeks. 

RESULTS 

Population abundance on OP Gina and natural reefs at Santa Cruz Island 

Adult blackeye goby, Rhinogobiops nicholsii, were the most abundant fishes observed on benthic 

transects at OP Gina and all natural rocky reef sites located at Anacapa and Santa Cruz Islands 

(Figure 1) in June, July, August 2003 (Figures 2, 4, and 6). At OP Gina, blackeye gobies were 

located on the seafloor only, usually associated with mussel shell habitat, and were not found in 

the water column or on the platform structure (Figures 3, 5, and 7). Blackeye gobies were seen 

on the rocky faces of vertical reefs above the soft-sediment seafloor at the three natural control 

sites, Chief Reef, Potato Reef, and Orizaba Reefs, but only occasionally and in very low 

numbers. At Chief reef, gobies were observed in the water displaying mating behavior and 
Final Study Report – Lenihan and Brooks 

16

occasionally feeding on zooplankton. Other fishes that were regularly observed at all sites, pile 

surfperch (Damalichthys vacca), rubberlip surfperch (Damalichthys toxotes), and cabezon 

(Scorpaenichthys marmatus), were found on both benthic habitat and in the water column. The 

painted greenling Oxylebius pictus was the second most commonly found fish after blackeye 

gobies (Figures 2-7), and like the balckeye goby, was found only on the bottom habitat. 

Cabezon was observed in relatively high numbers on the support structures of OP Gina, often 

males guarding egg masses. 

Transect surveys of June 18-19, 2003, for all 5 species censused 

Site

G in a - b o tto m F ish cam p R alp h 's R id g e E M K R eef C h ief R eef P o tato R o ck O rizab a

Mean number of individuals

 per 60m2 transect

0

2 0

4 0

6 0

8 0

100

120

140

160 C . nicholsii 

O . pictus 

R . vacca 

R . toxotes 

S . m arm aratus

P latform Anacapa Santa C ruz

T ran se c t s u rv e ys o f Ju n e 1 8-1 9, 20 03 , fo r all

 s p ec ie s o th e r th a n R . n ic h o lsii

S ite

G in a - b o tto m F is h c a m p R a lp h 's R id g e E M K R e e f C h ie f R e e f P o ta to R o c k O riz a b a

Mean number of individuals

 per 60m2 transect.

0

2

4

6

8

1 0 O . p ictu s 

R . vacca

R . toxotes 

S . m arm aratus

P la tfo rm A na ca p a S a n ta C ruz

Figure 2. Abundance of fishes at POCS oil platform Gina (OP Gina) and natural rocky reefs at Anacapa and Santa 

Cruz Islands in June 2003. Data are means and 95% CI from four replicate 30 m x 2 m transect counts collected by 

divers from each site. C. nicholsii is the former name for R. nicholsii, the blackeye goby.
Relative Importance of POCS Oil Platforms

17

Species

C. nicholsii O. pictus R. vacca R. toxotes S. marmaratus

Depth (ft)

0

20

40

60

80

100 232 41 

1 

3 

6 

7 

6 

1 

8 

10 

4 

1 

3 

Surface

Bottom

Figure 3. Total number and vertical distribution of fishes observed beneath OP Gina on 14 June 2003. Data from 

bottom transect (31m depth) are included. Each number represents the total number of individuals of all species 

recorded at that depth. C. nicholsii is the former name of R. nicholsii, the blackeye goby.
Final Study Report – Lenihan and Brooks 

18

T ra n s e c t s u rv e y s o f J u ly 1 4 -1 8 , 2 0 0 3 , fo r a ll 5 s p e c ie s c e n s u s e d 

S ite

G in a F is h c a m p R . R id g e E M K C h ie f P o ta to O riz a b a

Number of individuals per

 60m2 transect

0

5 0

100

150

200

250

300

C . n ic h o ls ii 

O . p ic tu s 

R . va c c a

R . to xo te s

S . m a rm a ra tu s

P la tfo rm A n a c a p a S a n ta C ru z

T ra n s e c t s u rv e y s o f J u ly 1 4 -1 8 , 2 0 0 3 , fo r a ll

 s p e c ie s o th e r th a n R . n ic h o ls ii

S ite

G in a F is h c a m p R . R id g e E M K C h ie f P o ta to O riz a b a

Mean number of individuals per 

60m2 transect

0

2

4

6

8

1 0

O . p ic tu s 

R . v a c c a

R . to x o te s

S . m a rm a ra tu s

P la tfo rm A n a c a p a S a n ta C ru z

Figure 4. Abundance of fishes at POCS oil platform Gina (OP Gina) and natural rocky reefs at Anacapa and Santa 

Cruz Islands in July 2003. Data are means and 95% CI from four replicate 30 m x 2 m transect counts collected by 

divers from each site. C. nicholsii is the former name of R. nicholsii.
Relative Importance of POCS Oil Platforms

19

Species

C. nicholsii O. pictus R. vacca R. toxotes S. marmaratus

Depth

0

20

40

60

80

100

302 25 

5 

2 

2 

1 

15,8 1 

1 

1 

9,4

2 

1 

1 

1 

1 

1 

1 

1 

1 

Bottom

Surface

Figure 5. Total number and vertical distribution of fishes observed beneath OP Gina on 17 July 2003. Data from 

bottom transect (31m depth) are included. Each number represents the total number of individuals of all species 

recorded at that depth. Number after commas are counts made at the same depths but counted by divers when 

conducting bottom transects (i.e. looking upwards). R. nicholsii was initially C. nicholsii. 
Final Study Report – Lenihan and Brooks 

20

Site

Gina Fishcamp Ralph's Ridge EMK Chief Reef Potato Orizaba

Mean number of individuals

 per transect (40m

2)

0

50

100

150

200 C. nicholsii 

O. pictus 

R. vacca 

R. toxotes 

S. Marmaratus 

Transect surveys of August 20-21, 2003, for all 5 species censused 

Platform Anacapa Santa Cruz

Site

Gina Fishcamp Ralph's Ridge EMK Chief Reef Potato Orizaba

Mean number of individuals 

per transect (40m

2)

0

2

4

6

8

O. pictus 

R. vacca 

R. toxotes 

S. marmaratus 

Transect surveys of August 20-21, 2003, for all 5 species 

censused except R. nicholsii

Platform Anacapa Santa Cruz

Figure 6. Abundance of fishes at POCS oil platform Gina (OP Gina) and natural rocky reefs at Anacapa and Santa 

Cruz Islands in August 2003. Data are means and 95% CI from four replicate 30m x 2m transect counts collected 

by divers from each site. C. nicholsii was the former name of R. nicholsii, the blackeye goby.
Relative Importance of POCS Oil Platforms

21

Species

C. Nicholsii O. Pictus R. vacca R. toxotes S. marmaratus

Depth (feet)

0

20

40

60

80

100

305 1, 17

3 

1 

3, 15 2, 20

1 

3 

1 

1 

7 

1 

Bottom

Surface

Figure 7. Total number and vertical distribution of fishes observed beneath OP Gina on 30 August 2003. Data 

from bottom transect (31m depth) are included. Each number represents the total number of individuals of all 

species recorded at that depth. Number after commas are counts made at the same depths but counted by divers 

when conducting bottom transects (i.e. looking upwards).

In June 2003, there were significantly higher densities of blackeye gobies at Chief Reef than at 

Potato Reef-90’ and OP Gina, and greater numbers at Orizaba Reef than at Potato Reef-90’ 

(Figure 2). There were no significant differences among other locations during June 2003. In 

July 2003, there were greater numbers of blackeye gobies at Chief Reef than at other locations, 

and no difference in goby density among any other stations (Figure 4). In August 2004, there 

were generally higher densities of blackeye gobies at all stations than during June and July, but 

there were no significant differences among locations (Figure 6). 

Recruitment 

In 2004, we examined recruitment during March-September, months in which blackeye gobies 

have been reported to recruit (e.g., Love 1999). Recruitment did not occur or was at very low 

levels March through June, when steadily increasing recruitment began. Recruitment reached 

maximum levels in late July-early August (Figure 8). There was no significant difference among 

locations for any time period, due mainly to high variation within sites and thus low power to 

detect differences. However, there was a trend towards lower recruitment at OP Gina than at 

natural reefs, across all sampling dates. 
Final Study Report – Lenihan and Brooks 

22

Recruitment at all sites: March - September 2004

Date

March

18

April

10

May

27

June

11

June

23

July

16

July

31

August

11

August 23

September

17

Mean number of recruits per m

2

0

2

4

6

8

Gina 

Chief 

Potato 

Orizaba 

Figure 8. Recruitment per unit area of habitat of R. nicholsii measured March-September 2004 at OP Gina and the 

three natural rocky reefs at Santa Cruz Island. Data are means and 95% CI from four replicate 30 m x 2 m transects. 

Visual counts were made by divers.

Population structure, immigration, and emigration 

We were able to tag a relatively high number of blackeye goby at all sites in September, October, 

and November 2003, and January 2004 (Tables 2-5). The number of gobies tagged at OP Gina 

was less than at other sites in 2003 (Figure 9) because goby density was lower than reef sites and 

there was often more shell material in which fish were able to escape and hide, thereby making 

them more difficult for divers to catch. By December 2004, we were highly efficient at tagging 

gobies at all stations. We sampled transects for tagged gobies in December 2003, and January, 

June, and July 2004 and found relatively high rates of tag returns at all sites, except for OP Gina 

in December 2003, when we found very low numbers of fishes tagged in September. Low 

numbers of returns of blue (i.e., September) tagged fish during this period may have resulted 

from very low light levels and the resulting difficulty in identifying the blue tags. 
Relative Importan

23

Table 2. Total number of blackeye gobies tagged in the study, and the number of tags and proportion of individuals tagged recovered in 

Site Total # tags applied # of tags recovered December 2003 

Blue Yellow Orange Total Blue Yellow Orange Total Blue 

Chief Reef 80 120 100 300 5 19 18 42 0.06 Potato Reef 81 120 85 286 19 29 30 78 0.23 Orizaba Reef 125 130 161 416 5 36 41 82 0.04 OP Gina 43 47 63 153 1 11 15 26 0.02  Blue = September 2003 Yellow = October 2003 Orange = November 2003 

Table 3. Total number of blackeye gobies tagged in the study, and the number of tags and proportion of individuals tagged recovered in 

Site Total # tags applied # of tags recovered Janaury 2004 

Blue Yellow Orange Green Total Blue Yellow Orange Green Total Blue 

Chief Reef 80 120 100 147 447 2 4 22 20 48 0.03 Potato Reef 81 120 85 109 395 10 27 26 33 96 0.12 Orizaba Reef 125 130 161 154 570 3 18 33 44 98 0.02 OP Gina 43 47 63 91 244 2 17 24 35 78 0.05  Blue = September 2003 Yellow = October 2003 Orange = November 2003 Green = January 2004 
Final Study Report – Lenihan and Brooks 

24

Table 4. Total number of blackeye gobies tagged in the study, and the number of tags and proportion of individuals tagged recovered i

Site Total # tags applied # of tags recovered June 2004 

Blue Yellow Orange Green Total Blue Yellow Orange Green Total Blue 

Chief Reef 80 120 100 147 447 0 7 6 14 27 0 Potato Reef 81 120 85 109 395 3 10 1 10 24 0.04 Orizaba Reef 125 130 161 154 570 1 11 7 22 41 0.01 OP Gina 43 47 63 91 244 1 7 10 10 28 0.02  Blue = September 2003 Yellow = October 2003 Orange = November 2003 Green = January 2004 

Table 5. Total number of blackeye gobies tagged in the study, and the number of tags and proportion of individuals tagged recovered i

Site Total # tags applied # of tags recovered July 2004 

Blue Yellow Orange Green Total Blue Yellow Orange Green Total Blue 

Chief Reef 80 120 100 147 447 0 2 2 13 17 0 Potato Reef 81 120 85 109 395 5 15 8 14 42 0.06 Orizaba Reef 125 130 161 154 570 2 10 4 19 35 0.02 OP Gina 43 47 63 91 244 0 7 9 13 29 0  Blue = September 2003 Yellow = October 2003 Orange = November 2003 Green = January 2004 
Relative Importance of POCS Oil Platforms

25

Site

Gina Chief Potato Orizaba

Number of fish tagged

0

25

50

75

100

125

150

175 September 

October 

November 

January 

Gina Chief Potato Orizaba

Cumulative % of tags recovered

0

20

40

60

80

100 September

October

November

January

A B

Figure 9. Total number of blackeye goby, R. nicholsii, tagged from September 2003 to January 2004, the 

cumulative numbers of tags recovered during censuses conducted from December 2003 to July 2004 at OP Gina and 

three natural rocky reefs sites at Santa Cruz Island.

Analysis of the size structure of populations at our sampling sites collected from tagged fishes 

indicated that a higher proportion of the population at OP Gina contained relatively large fishes 

compared with all natural reef sites (Figure 10-13; G-test, P<0.05). There was no significant 

difference in size structure among reef sites (G-test, P>0.056). Larger fish at OP Gina may 

result from a number of factors, including higher survivorship and faster growth rates, which we 

plan to explore via population modeling. One potential factor, reduced predation mortality at OP 

Gina, was explored with a manipulative experiment described below. 
Final Study Report – Lenihan and Brooks 

26

Platform Gina

0

1

2

3

4

5 September N=43

0

2

4

6

8 November

N=63

NSR=0

NOR=2

Number of Individuals

0

2

4

6

8

10

Size (mm)

N=47

NSR=0

October

40 60 80 100

0

2

4

6

8

10 N=91

NSR=0

NOR=1

NNR=7

January

Figure 10. The size-frequency distribution of blackeye goby at OP Gina collected from fish tagged September 2003 

to January 2004. SR= September tag returns; OR= October tag returns; and NR= November tag returns.
Relative Importance of POCS Oil Platforms

27

Chief Reef

0

2

4

6

8

10

Number of Individuals

0

2

4

6

8

10

12

14

Size (mm)

0

2

4

6

8

September

October

November

N=80

N=120

N=100

NSR=2

NSR=0

NOR=0

40 60 80 100

0

2

4

6

8

10

12 N=147

NSR=0

NOR=1

NNR=5

January

Figure 11. The size-frequency distribution of blackeye goby at Chief Reef (SCI) collected from fish tagged 

September 2003 to January 2004. SR= September tag returns; OR= October tag returns; and NR= November tag 

returns.
Final Study Report – Lenihan and Brooks 

28

Potato Reef

0

2

4

6

8

10

Number of Individuals

0

2

4

6

8

10

September

October

N=81

N=120

NSR=4

Size (mm)

0

2

4

6

8

10 November N=85

NSR=2

NOR=7

40 60 80 100

0

2

4

6

8

10

N=109

NSR=4

NOR=8

NNR=6

January

Figure 12. The size-frequency distribution of blackeye goby at Potato Reef (SCI) collected from fish tagged 

September 2003 to January 2004. SR= September tag returns; OR= October tag returns; and NR= November tag 

returns.
Relative Importance of POCS Oil Platforms

29

Orizaba Reef

0

2

4

6

8

10

12

14

Number of Individuals

0

2

4

6

8

10

12

Size (mm)

0

2

4

6

8

10

12

14

September

October

November

N=125

N=130

N=161

NSR=7

NSR=3

NOR=2

40 60 80 100

0

2

4

6

8

10

12

14 N=154

NSR=0

NOR=9

NNR=7

January

Figure 13. The size-frequency distribution of blackeye goby at Orizaba Reef (SCI) collected from fish tagged 

September 2003 to January 2004. SR= September tag returns; OR= October tag returns; and NR= November tag 

returns.
Final Study Report – Lenihan and Brooks 

30

Results of the tag-and-recovery experiment indicate that rates of survival at both OP Gina and all 

rocky reefs sites were relatively high (Tables 2-5), or alternatively that rates of emigration at all 

sites was relatively low. Because each site was located substantial distances away from even the 

closest ref sites inhabited by gobies (see Methods), and during frequent surveys at the those sites 

we never saw tagged individuals, we think that immigration and emigration rates were generally 

very low and, that variation through time in the numbers of tagged fishes from each tagging is a 

good means of estimating mortality rates. However, the tagging method prevented us from 

definitively assessing whether immigration and emigration of adults and juveniles occurred 

among sites. The tagging data thus indicate that mortality rates of blackeye goby were lower at 

OP Gina than at natural rocky reefs, and that there was relatively little difference in mortality 

rates among the natural reef sites. The rate of tag returns declined substantially between January 

and June-July 2004, a pattern probably caused by a series of intense storms that occurred during 

winter February-March 2004. In a subsequent paper, we will use tagging data in a population 

dynamic model to more thoroughly estimate rates of mortality, survival, and movement among 

reefs and OP Gina. 

Our tagging effort also provided the first comprehensive information concerning length-biomass 

relationships. Data from fish collected across all tagging periods indicate a tight relationship 

between the two variables for all sites in our study (Figures 14-15). These data will provide 

others working with this species with the means to estimate biomass through length 

measurements. We found no apparent difference in length-biomass relationships between 

populations at OP Gina and natural reefs. 

All Sites - wet weights & lengths

Length (mm)

30 40 50 60 70 80 90 100

Weight (g)

0

2

4

6

8

10 Chief Reef (n=65)

Orizaba Reef (n=48)

Potato Reef (n=61)

OP Gina (n=62)

Figure 14. Weight-length relationships for blackeye goby at all locations. Data are from wet weights of gobies (see 

Methods section for details). 
Relative Importance of POCS Oil Platforms

31

All Sites - ETOH weights & lengths

Length (mm)

30 40 50 60 70 80 90 100

Weight (g)

0

2

4

6

8 Chief Reef (n=65)

Orizaba Reef (n=48)

Potato Reef (n=51)

OP Gina (n=52)

Figure 15. Weight-length relationships for blackeye goby at all locations. Data are from gobies from 70% ETOH 

(see Methods section for details). 

Fecundity 

We estimated variation in fecundity among goby populations located at OP Gina and natural 

rocky reefs at Santa Cruz Island by quantifying and comparing various metrics associated with 

egg masses collected at each site in April 2004, which is when we observed the highest 

abundance of male gobies displaying nest guarding behavior. Potato Reef (both at 60’ and 90’ 

water depths) had a significantly higher number of eggs per clutch than the other sites (Figure 

16). There were no significant differences in total egg counts at the other sites. Relatively high 

egg counts at Potato Reef were caused by both larger mean areas of egg masses and higher egg 

densities per clutch than at other sites (Figure 17). Although there were no significant 

differences among sites in the latter two parameters, there were trends for higher values at Potato 

Reef versus all other sites. The relationship between egg density and clutch size in area are 

illustrated in Figure 18. 
Final Study Report – Lenihan and Brooks 

32

Total number of eggs per clutch at all sites

Site

Gina Chief Potato 90' Potato 60' Orizaba

Mean number of eggs per clutch

0

5000

10000

15000

20000

Figure 16. Mean (+ 95% CI) number of eggs per clutch at all sites. The number of clutches at each site varied: OP 

Gina, N= 15 clutches; all other sites, N= 11. Data were collected April 2004. 

Mean egg mass area and density for all sites

Site

Gina Chief Potato 90' Potato 60' Orizaba

Mean density (eggs per cm2

) 100

150

200

250

300

Mean area of egg masses (cm2)

20

40

60

80

Mean density 100

 Mean area

Figure 17. Mean (+ 95% CI) area and density of egg masses at OP Gina and natural rocky reef sites on Santa Cruz 

Island. Data were collected in April 2004. 
Relative Importance of POCS Oil Platforms

33

Surface area of egg mass (cm2)

0 20 40 60 80 100

Density of eggs (# per cm

2)

50

100

150

200

250

300

350

Gina

Chief

Potato 90'

Potato 60'

Orizaba

P 90

P 60

Orizaba

Gina

Chief

Figure 18. Relationship between egg density and surface area of eggs in egg masses from all sites examined. Eggs 

were collected in April 2004.

Predation mortality of blackeye goby 

The tethering of blackeye gobies to longlines and monitoring of their fate was used to test 

whether predation on gobies differed among OP Gina and natural rocky reefs. This experiment 

was conducted because we found populations of gobies at OP Gina contained a higher proportion 

of larger fishes than other stations, thereby indicating survivorship was highest at OP Gina. In 

contrast, of course, growth rates might have been higher at OP Gina than other stations. 

The tethering method we used had four possible outcomes, three with missing fish, snapped 

lines, empty hooks, or snapped lines in which we also found empty hooks nearby on the seafloor, 

and, the fourth outcome, gobies still hooked (see Methods for details). To test which of these 

outcomes represented a predation event, we conducted an experiment on Naples Reef on the 

mainland coast (see Methods for details). Results from this experiment indicate with a 

moderate-high level of certainty (~50-77%) that snapped lines, empty hooks, and snapped lines 

with empty hooks were caused by predation and not escapement (Tables 6-7). These results 

provide us with guarded confidence that results from our actual tethering experiment are valid 

(see below). 
Final Study Report – Lenihan and Brooks 

34

Table 6: Tethering control for treatments with empty hooks (“predation” vs “escape”). 

Fates of hooks/gobies T = 40 minutes T = 60 minutes 

Mean 95% Mean 95% 

Snapped 0.66 1.43 1.33 1.43 

Live 3.00 2.48 0.66 1.43 

Empty 1.33 1.43 3.00 2.48 

Empty due to: 

 predation (confirmed) 0.66 1.43 1.33 1.43 

 escape (confirmed) 0.00 0.00 0.00 0.00 

 unknown 0.66 1.43 1.66 1.43 

% of all hooks empty due to 

possible escape 

13.3% - 33.3% - 

% of empty hooks due to 

possible escape 

50.0% - 55.3% - 

Table 7: Tethering control for treatments with empty hooks (“predation” vs “escape”). 

Fates of hooks/gobies T = 40 

minutes 

T = 60 

minutes 

Snapped 2 4 

Live 9 2 

Empty 4 9 

Empty due to: 

 predation (confirmed) 2 4 

 escape (confirmed) 0 0 

 unknown 2 5 

% of all hooks empty due to 

possible escape 

13.3% 33.3% 

% of empty hooks due to 

possible escape 

50.0% 55.5% 

 

Results from the tethering experiment conducted at OP Gina and natural reef sites indicated that 

rates of predation on gobies, by the fishes that we observed attacking goby or found hooked to 

our lines with gobies in their stomachs (e.g., gopher and olive rockfishes), did not differ between 

OP Gina and all the natural reef sites (Figure 19). However, there was a statistically nonsignificant trend (based on the overlap of 95% confidence level error bars in Figure 19) towards 

higher survivorship at OP Gina relative to natural reefs. Those fish that we estimate were 

probably preyed upon (i.e., those on lines “snapped” and “snapped and empty hooks”) were 

mostly of medium length (Figure 20). In contrast, empty hooks were those that tethered 

relatively large gobies. 
Relative Importance of POCS Oil Platforms

35

Fates of tethered gobies (tethered for 1 hr) at all four sites

Site

Gina Chief Potato Orizaba

Mean Number of Gobies

0

2

4

6

8

10

12

14

Snapped lines 

Empty hooks 

Live goby on hook 

Snapped + Empty 

Figure 19. Fates of gobies tethered to lines at all sites. Data are means + 95% Confidence Intervals (CI). The 

tethering experiment was conducted 10-17 July 2004. 
Final Study Report – Lenihan and Brooks 

36

Fates of tethered gobies after 1 hour, results 

pooled from all 4 sites.

Size (mm)

60 70 80 90 100

Number of Gobies

0

1

2

3

4

5

6

7

Snapped lines 

Empty hooks 

Gobies live 

Figure 20. The length frequency of gobies tethered on lines to test predation risk. Data are from three treatments, 

lines which were found snapped, and therefore likely a sign of gobies being eaten by rockfish or other groundfish 

(e.g., cabezon and lingcod); lines with empty hooks, from which gobies could have escaped or were eaten; and live 

gobies that remained tethered after 1 hr. Data are pooled from all four sites, OP Gina, Chief Reef, Orizaba Reef, and 

two locations (water depths) at Potato Reef (60 and 90 feet). 

Age and Growth estimates 

We are in the process of analyzing age and growth data. We found that patterns of growth via 

rings or demarcations in blackeye goby otoliths are very difficult to identify. However, we are 

developing a statistical model based on sampling populations of visual microscope counts of 

potential growth rings taken by different observers as a means of estimating age classes. If 

successful we will be able to age and therefore estimate growth rates in goby populations and OP 

Gina and our natural reef sites. We think the method we are developing will also generate a 

publication that can be used by others to estimate growth patterns in otoliths that are difficult to 

read.

DISCUSSION 

We assembled a thorough spatially and temporally comprehensive field-based demographic data 

set of blackeye goby populations inhabiting OP Gina and three natural rocky reefs located on the 

north shore Santa Cruz Island in the ESBC. The natural reefs we used were those located closest 

in space to OP Gina that were inhabited by the blackeye goby. Our results provide information 
Relative Importance of POCS Oil Platforms

37

that can be used to estimate the relative contribution of goby populations from OP Gina and the 

natural reefs to the regional population pool of this species. In general, we found that OP Gina 

does not represent a critical population source of blackeye gobies to the region. We also found 

that OP Gina does not represent a population sink. These findings have a major implication; that 

during consideration of decommissioning alternatives, the level of potential localized population 

loss at OP Gina should not be a major factor influencing management decisions. Removal of OP 

Gina should not have an important influence on regional blackeye goby populations, and were it 

to be left in place, it should not cause a decrease in population abundances at a regional scale. 

Although there were no statistically significant differences in blackeye goby abundance between 

OP Gina and natural reefs, nor among reef sites, there was a trend towards lower abundance at 

OP Gina versus natural reefs sites. This was somewhat surprising because we found a relatively 

large of amount of favored goby habitat, mainly mussel shells, at OP Gina. In addition, results 

form other demographic measurements, especially trends toward lower mortality via predation, 

and potentially higher growth rates at OP Gina versus natural reefs are mechanisms that should 

contribute to higher abundance at Op Gina. These results may be explained by several factors, 

including higher mortality rates caused by some other factor than predation, including 

intraspecific density dependent interactions within a potentially habitat limited environment. We 

found little evidence for relatively high emigration based on our tagging data. 

Another factor that may help to explain the trends toward relatively low abundance at OP Gina 

was that this site had a trend towards lower input rates via recruitment than the natural reef sites. 

Recruitment levels in March-September did not vary statistically but here was a trend towards 

relatively low levels at OP Gina. We measured recruitment as the relatively abundance of YOY 

blackeye gobies counted by divers along transects. There is the possibility that we 

underestimated recruitment at OP Gina relative to other sites because the study area was deep 

and dark, and the bottom was covered with excellent refuges gobies to hide within. However, 

we think it is more likely that recruitment rates are lower at Op Gina because the platform is 

relatively isolated from other populations that could supply larvae. 

The mean size of individual gobies was significantly higher at OP Gina than at natural reef sites. 

There were no significant differences among control reef sites. These data indicate that there is a 

larger proportion of large fish in the OP Gina population than at other sites. Large fish at OP 

Gina are probably due to faster growth rates, greater survivorship to older age classes, or a 

combination of both factors. We tested whether mortality caused by predation varied among 

sites as a way to determining whether survivorship was greater at OP Gina than natural reefs. 

Results from our experiment indicate a trend toward reduced predation mortality at Op Gina. 

This was likely caused by relatively low abundance at OP Gina of kelp bass that were by far the 

most voracious predators on blackeye gobies at control reef sites. The other important goby 

predator, cabezon, is found at relatively high levels at Op Gina, but mainly inhabited the 

supporting structure of the platform located above the bottom where no gobies were found. 

Therefore, reduced relatively low levels of predation at OP Gina may explain larger size 

structure of that population relative to natural reef sites. We are in the process of analyzing age 

and growth data from goby otoliths, the results of which should help us further explain the 

variation in size structure. 
Final Study Report – Lenihan and Brooks 

38

We fond that several proxies for fecundity of blackeye goby, based on various measurements of 

egg clutches laid and guarded by gobies, varied between OP Gina and reef control sites. Egg 

clutches were smaller and had lower egg densities at Op Gina than at natural reef sites, indicating 

that populations on OP Gina may generate less per capita output than populations on natural 

reefs. Based on differences in standardized abundances as each site, these data indicate OP Gina 

populations may have less total output. 

Our study provides an example of how population ecological tools and data can be used to 

address a complex applied problem, in this case the relative contribution of POCS oil platforms 

to regional population dynamics of a reef fish relative to the contribution made by natural reefs. 

This approach has been used often in terrestrial wildlife management and well as marine 

fisheries and mammal management and conservation. Our study provides one of the few 

examples where a thorough demographic survey has been subsidized by specific experimental 

evidence in a marine ecological field assessment (see Schmitt and Osenberg 1996 for other 

examples). This approach is valuable for the management of POCS oil platforms that are both 

extensive in their size and environmental impact but also situated in environmental conditions 

that make examination of the their ecological value and contributions difficult to quantify, 

especially at regional scales. We plan to use the data generated from this study to conduct 

generalized population dynamic models that can be used to explore the general effects of ESBC 

platforms on regional stocks of the blackeye goby, and to predict the impact of the five 

decommissioning alternatives. 
Relative Importance of POCS Oil Platforms

39

ACKNOWLEDGEMENTS 

We thank RJ Schmitt and SJ Holbrook for stoking our interest in this important study. We thank 

S. Herrar, S. Mutz, S. Levenbach, C. Culver, Matt Newnham, S. Anderson, Eric Hessell, Rick 

Wilder, C. Svedlund, Keith Seydel, Ashley Greenly and a suite of other UCSB scientists and 

students who provided valuable input including especially time on the seafloor as hard working 

research divers. 
40

LITERATURE CITED 

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reserves. Bulletin of Marine Science 66: 799-820. 

Harms, S. and C. D. Winant. 1998. Characteristic patterns of the circulation in the Santa 

Barbara Channel. Journal of Geophysical Research 103: 3041-3065. 

Hench, J. L., B. O. Blanton, and R. A. Luettich, Jr. 2001. Lateral dynamic analysis and 

classification of barotropic tidal inlets. Continental Shelf Research, in press. 

Holbrook, S. J., R. F. Ambrose, L. Botsford, M. H. Carr, P.T. Raimondi, and M. J. Tegner. 

2000. Ecological issues related to decommissioning of California's offshore production 

platforms. Report to the University of California Marine Council. The Select Committee 

on Decommissioning, University of California. 

Holt, R. D. 1985. Population dynamics in two-patch environments: some anomalous 

consequences of an optimal habitat distribution. Theoretical Population Biology 28: 181-

208. 

Lenihan, H.S., C.H. Peterson, J.E. Byers, J.H. Grabowski, G.W. Thayer, and D.R. Colby. 2001. 

Cascading of habitat degradation: oyster reefs invaded by refugee fishes escaping stress. 

Ecological Applications 11: 764-782. 

Lipcius, R. et al. 1997. Hydrodynamic decoupling of recruitment, habitat quality, and adult 

abundance in the Caribbean spiny-lobster: source-sink dynamics? Marine and 

Freshwater Research 48: 807-815. 

Love, M. S., J. Caselle, and L. Snook. 2000. Fish assemblages around seven oil platforms in the 

Santa Barbara Channel area. Fishery Bulletin 98: 96-117. 

Page, H. M., J. E. Dugan, D. S. Dugan, J. B. Richards, and D. B. Hubbard. 1999. Effects of an 

offshore oil platform on the distribution and abundance of commercially important crab 

species. Marine Ecology Progress Series 185: 47-57. 

Pulliam, H. R. 1988. Sources, sinks, and population regulation. American Naturalist 132: 652-

661. 

Schmitt, R.J. and C. W. Osenberg. 1996. Detecting Ecological Impacts: Concepts & 

Applications in Coastal Habitats. Academic Press. 
41

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