NOAA Technical Memorandum NMFS-AFSC-164
 

Food Habits of Groundfishes 

in the Gulf of Alaska in 1999 and 2001 

by 

M-S. Yang, K. Dodd, R. Hibpshman, and A. Whitehouse 

U.S. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration
 

National Marine Fisheries Service
 

Alaska Fisheries Science Center
 

May 2006 
NOAA Technical Memorandum NMFS 

The National Marine Fisheries Service's Alaska Fisheries Science Center 

uses the NOAA Technical Memorandum series to issue informal scientific and 

technical publications when complete formal review and editorial processing 

are not appropriate or feasible. Documents within this series reflect sound 

professional work and may be referenced in the formal scientific and technical 

literature. 

The NMFS-AFSC Technical Memorandum series of the Alaska Fisheries 

Science Center continues the NMFS-F/NWC series established in 1970 by the 

Northwest Fisheries Center. The NMFS-NWFSC series is currently used by 

the Northwest Fisheries Science Center. 

This document should be cited as follows: 

M-S. Yang, K. Dodd, R. Hibpshman, and A. Whitehouse. 2006. Food 

habits of groundfishes in the Gulf of Alaska in 1999 and 2001. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-164, 199 p. 

Reference in this document to trade names does not imply endorsement by 

the National Marine Fisheries Service, NOAA. 
NOAA Technical Memorandum NMFS-AFSC-164
 

Food Habits of Groundfishes
 

in the Gulf of Alaska in 1999 and 2001
 

by
 

M-S. Yang, K. Dodd, R. Hibpshman, and A. Whitehouse
 

Alaska Fisheries Science Center
 

7600 Sand Point Way N.E.
 

Seattle, WA 98115
 

www.afsc.noaa.gov 

U.S. DEPARTMENT OF COMMERCE 

Carlos M. Gutierrez, Secretary 

National Oceanic and Atmospheric Administration 

Vice Admiral Conrad C. Lautenbacher, Jr., U.S. Navy (ret.), Under Secretary and Administrator 

National Marine Fisheries Service 

William T. Hogarth, Assistant Administrator for Fisheries 

May 2006 
This document is available to the public through: 

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

www.ntis.gov 
Notice to Users of this Document 

This document is being made available in .PDF format for the convenience of users; however, the 

accuracy and correctness of the document can only be certified as was presented in the original hard 

copy format. 

 iii 

ABSTRACT


 A total of 7,899 stomachs from 40 species, walleye 


pollock (Theragra chalcogramma), Pacific cod (Gadus 


macrocephalus), arrowtooth flounder (Atheresthes stomias), 


Pacific halibut (Hippoglossus stenolepis), sablefish 


(Anoplopoma fimbria), spiny dogfish (Squalus acanthias), big 


skate (Raja binoculata), Bering skate (Bathyraja interrupta), 


Alaska skate (Bathyraja parmifera), longnose skate (Raja 


rhina), eulachon (Thaleichthys pacificus), shortfin eelpout 


(Lycodes brevipes), black eelpout (Lycodes diapterus), wattled 


eelpout (Lycodes palearis), giant grenadier (Coryphaenoides 


pectoralis), rougheye rockfish (Sebastes aleutianus), Pacific 


ocean perch (Sebastes alutus), redbanded rockfish (Sebastes 


babcocki), shortraker rockfish (Sebastes borealis), dusky 


rockfish (Sebastes variabilis), sharpchin rockfish (Sebastes 


zacentrus), shortspine thornyhead (Sebastolobus alascanus), 


Atka mackerel (Pleurogrammus monopterygius), spinyhead sculpin 


(Dasycottus setiger), yellow Irish lord (Hemilepidotus 


jordani), bigmouth sculpin (Hemitripterus bolini), darkfin 


sculpin (Malacocottus zonurus), great sculpin (Myoxocephalus 


polyacanthocephalus), dusky snailfish (Liparis gibbus), 


Pacific sandfish (Trichodon trichodon), searcher (Bathymaster 


signatus), northern ronquil (Ronquilis jordani), deepsea sole 


(Embassichthys bathybius), rex sole (Errex zachirus), flathead 


sole (Hippoglossoides elassodon), butter sole (Isopsetta 


isolepis), southern rock sole (Lepidopsetta bilineata), 


northern rock sole (Lepidopsetta polyxystra), yellowfin sole 


(Pleuronectes asper), and Dover sole (Microstomus pacificus) 


were analyzed to describe the food habits of the major 


groundfish species in the Gulf of Alaska in 1999 and 2001. 


Arrowtooth flounder, Pacific halibut, sablefish, Pacific 


cod, bigmouth sculpin, big skate, and Bering skate were the 


main piscivores. Walleye pollock were the dominant prey fish. 


The main predators that fed on Tanner crabs were Pacific 


halibut, Pacific cod, big skate, longnose skate, and great 


sculpin. Flathead sole, sharpchin rockfish, rougheye rockfish,


longnose skate, and walleye pollock were the main consumers of 


pandalid shrimp. Sharpchin rockfish, Pacific ocean perch, 


redbanded rockfish, Atka mackerel, and pollock fed mainly on 


zooplankton (mainly euphausiids and calanoid copepods). 


Southern rock sole, northern rock sole, rex sole, Dover sole, 


deepsea sole, and darkfin sculpin were benthic feeders; they 


fed mainly on polychaetes, marine worms, and brittle stars.


v


CONTENTS 


ABSTRACT .............................................. iii 


INTRODUCTION .......................................... 1 


METHODS .............................................. 3 


RESULTS and DISCUSSION ............................... 10 


Walleye pollock .................................... 10 


Pacific cod ........................................ 19 


Arrowtooth flounder ................................ 31 


Pacific halibut .................................... 39 


Sablefish ......................................... 50 


Spiny dogfish ..................................... 60 


Big skate ......................................... 62 


Bering skate ...................................... 64 


Longnose skate .................................... 67 


Alaska skate ...................................... 69 


Eulachon .......................................... 71 


Shortfin eelpout .................................. 74 


Black eelpout ..................................... 77 


Wattled eelpout ................................... 79 


Giant grenadier ................................... 82 


Rougheye rockfish ................................. 85 


Pacific ocean perch ............................... 88 


Redbanded rockfish ................................ 91 


Shortraker rockfish ............................... 94 


Dusky rockfish .................................... 98 


Sharpchin rockfish ................................ 101 


Shortspine thornyhead ............................ 106 


Atka mackerel ..................................... 111 


Spinyhead sculpin ................................. 116 


Yellow Irish lord ................................. 119 


Bigmouth sculpin .................................. 122 


Darkfin sculpin ................................... 126 


Great sculpin ..................................... 130 


Dusky snailfish ................................... 133 


Pacific sandfish .................................. 136 


Searcher .......................................... 139 


Northern ronquil .................................. 142 


Deepsea sole ...................................... 144 


Rex sole .......................................... 147 


Flathead sole ..................................... 152 


Butter sole ....................................... 157 

vi


 Southern rock sole ................................ 159 


Northern rock sole ................................ 165 


Yellowfin sole .................................... 170 


Dover sole ........................................ 175 


SUMMARY .............................................. 179 


ACKNOWLEDGMENTS ...................................... 187 


CITATIONS ............................................ 189 

INTRODUCTION 


The estimated biomass of the groundfish resource in 


the Gulf of Alaska is about 5.6 million metric tons (t) 


(NPFMC 2004). Therefore, understanding the food habits of 


these fish and the interrelationships between them, their 


predators and their prey, becomes important when we try to 


understand the Gulf of Alaska ecosystem. In order to 


understand the multispecies implications of harvesting 


strategies, it is also important to understand the 


groundfish food web. These topics were the objective of 


this study. 


In 1990, the Resource Ecology and Ecosystem Modeling 


(REEM) program of the Resource Ecology and Fisheries 


Management (REFM) Division at the Alaska Fisheries Science 


Center (AFSC) began systematic collections of fish stomach 


samples in the Gulf of Alaska. The collections have 


continued on a triennial (biennial since 1999) basis 


through REFM’s participation in the bottom trawl survey 


performed by the Center’s Resource Assessment and 


Conservation Engineering (RACE) Division in the Gulf of 


Alaska. This report includes information on the stomach 


collection procedures, data analysis, and comparisons of 


the diet of 40 groundfish species in the Gulf of Alaska 


(GOA) for 1999 (Table 1) and 2001 (Table 2). 

 2

 The western and central GOA regulatory areas of the 


North Pacific Fishery Management Council (NPFMC) were 


sampled. Some species which are encountered less often, 


their sample sizes were small and it is difficult to make 


inferences regarding their diets. 

 3 

METHODS 


Stomach Collection and Stomach Contents Analysis 


The study area (Fig. 1) covered the area from the Islands 


of Four Mountains (170o W long.) to Cape St. Elias (144o30’W 


long.), which encompasses the NPFMC’s western and central 


Gulf of Alaska regulatory areas. 


Scientists on board chartered bottom trawl vessels 


collected stomachs from fish captured in AFSC survey trawls.


Before excising a stomach, fish were examined for evidence 


of regurgitation or net feeding. If a fish had food in its 


mouth or around the gills, or if its stomach was inverted 


or flaccid, the fish was categorized as having regurgitated 


food and the specimen was discarded. If a predator had 


fresh food (usually fish) sticking out of the mouth or the 


throat, it was categorized as a net-feeding fish and was 


also discarded. When a sampled stomach was retained, it 


was put in a cloth stomach bag. A field tag with the 


species name, fork length (FL) of the fish, and haul data 


(including vessel, cruise, haul number, specimen number) 


was also put in the bag. All of the samples collected were 


then preserved in buckets containing a buffered 10% 


formalin solution. When the samples arrived at the 


laboratory, they were transferred into 70% ethanol before 


the stomach contents were analyzed. In the laboratory, the 

 4 

Table 1.-- Number of stomachs and fish size analyzed in the Gulf of Alaska in 1999. 

 F=stomachs with food, E=empty stomachs, T=total, SD=standard deviation. 

Species No. of stomachs Fork length (cm)* 

F E T Range Mean + SD 

Walleye pollock 497 43 540 10-69 38.33 + 5.79 

Pacific cod 453 1 454 14-104 54.96 + 5.73 

Pacific halibut 134 35 169 17-114 57.05 + 7.16 

Arrowtooth flounder 499 536 1035 9-80 41.30 + 5.05 

Sablefish 59 80 139 29-67 55.19 + 3.17 

Shortraker rockfish 1 40 41 42-42 42.00 + 0.00 

Sharpchin rockfish 6 0 6 19-27 23.67 + 3.08 

Atka mackerel 13 18 31 37-51 46.76 + 0.83 

Bigmouth sculpin 1 0 1 64-64 64.00 + 0.00 

Flathead sole 9 6 15 17-36 26.90 + 6.19 

Southern rock sole 63 43 106 15-50 34.18 + 2.85 

Northern rock sole 36 21 57 17-41 29.66 + 2.05 

Yellowfin sole 44 17 61 15-42 28.15 + 2.07 

Total 1,815 840 2,655 

* data from stomachs with food only 
 5 

Table 2.-- Number of stomachs and fish size analyzed in the Gulf of Alaska in 2001. 

 F=stomachs with food, E=empty stomachs, T=total, SD=standard deviation. 

Species No. Stomachs Fork length (cm)* 

F E T Range Mean + SD 

Walleye pollock 766 50 816 7-75 37.28 + 5.17 

Pacific cod 803 35 838 9-92 48.92 + 4.60 

Pacific halibut 808 81 889 13-126 61.63 + 7.44 

Arrowtooth flounder 1359 424 1783 13-81 37.66 + 4.93 

Sablefish 284 64 348 23-90 59.08 + 2.62 

Spiny dogfish 1 0 1 72-72 72.00 + 0.00 

Big skate 2 0 2 81-87 89.00 +11.31 

Bering skate 3 0 3 42-70 51.67 +15.89 

Alaska skate 1 1 2 59-59 59.00 + 0.00 

Longnose skate 3 0 3 112-133 121.60+10.6 

Eulachon 19 20 39 16-21 19.05 + 1.35 

Shortfin eelpout 17 1 18 19-29 22.30 + 1.19 

Black eelpout 1 0 1 24-24 24.00 + 0.00 

Wattled eelpout 2 1 3 37-40 38.50 + 2.12 

Giant grenadier 17 8 25 27-35 31.15 + 0.70 

Rougheye rockfish 25 11 36 16-78 34.10 + 2.88 

Pacific ocean perch 39 11 50 10-40 29.70 + 1.73 

Redbanded rockfish 3 1 4 20-22 21.00 + 1.00 

Shortraker rockfish 22 24 46 43-61 54.50 + 1.61 

Dusky rockfish 1 0 1 39-39 39.00 + 0.00 

Sharpchin rockfish 7 11 18 25-32 29.00 + 2.16 

Shortspine rockfish 27 14 41 15-39 25.67 + 0.35 

Atka mackerel 28 2 30 28-51 37.33 + 1.61 

Spinyhead sculpin 13 1 14 12-25 17.23 + 5.26 

Yellow Irish lord 2 0 2 30-38 34.00 + 5.66 

Bigmouth sculpin 2 1 3 20-75 47.50+38.89 

Darkfin sculpin 16 1 17 7-12 8.56 + 1.46 

Great sculpin 6 0 6 38-58 48.10 + 6.62 

Dusky snailfish 1 0 1 53-53 53.00 + 0.00 

Pacific sandfish 2 0 2 15-16 15.50 + 0.71 

Searcher 11 0 11 23-29 26.00 + 2.17 

Northern ronquil 1 0 1 16-16 16.00 + 0.00 

Deepsea sole 3 0 3 40-43 41.30 + 1.53 

Rex sole 41 1 42 24-50 37.40 + 2.21 

Flathead sole 16 15 31 30-51 36.73 + 2.85 

Butter sole 2 8 10 46-51 48.50 + 3.54 

Southern rock sole 29 4 33 19-43 32.23 + 1.58 

Northern rock sole 29 2 31 17-40 29.20 + 0.75 

Yellowfin sole 2 0 2 38-42 40.00 + 2.83 

Dover sole 35 3 38 34-60 44.38 + 1.66 

Total 4449 795 5244 

* data from stomachs with food only 
 6


170°E 180° 170°W 160°W 150°W 140°W 130°W 

50°N 

50°N 

60°N 

60°N 

Western GOA 

Central GOA 

Eastern GOA 

Bering Sea 

Alaska CANADA 

RUSSIA 

170°W 160°W 150°W 140°W 

Figure 1. --Study area in the Gulf of Alaska (GOA) in 1990 and 2001. 
 7 

stomach was cut open, the contents were removed, and then 


blotted with a paper towel. The wet weight was then 


recorded to the nearest 0.1 g. After obtaining the total 


weight for a stomach's contents, the contents were placed 


in a Petri dish and examined under a microscope. Each prey 


item was classified to the lowest practical taxonomic level. 


The prey items of all rockfishes, Pacific halibut, and 


sablefish were weighed and enumerated. The numbers of non-


commercially important prey were not counted for Pacific 


cod, walleye pollock, and arrowtooth flounder; instead the 


percent volume of these prey items were visually estimated. 


Prey weights and numbers of commercially important crabs 


and fish were recorded. If pollock otoliths were found, 


otolith lengths were measured and the pollock's standard 


length (SL) was derived through an otolith length-fish 


length regression table. Standard lengths of prey fish and 


carapace widths (CW) of Tanner crab (C. bairdi) were also 


recorded. During this study, discarded fish parts from 


commercial fish processing operations were also found quite 


frequently in the stomachs of some marine fishes (e.g., 


sablefish). Fish were identified as fishery offal if the 


parts (usually heads or tails) had an evident cut. 

 8 

Data Analysis 


The general diet of each species in each year was 


summarized to show the mean percent frequency of occurrence, 


and the mean percent of the total weight of each prey item 


found in the stomach (these values were calculated as the 


average of the values calculated from each haul). 


Change in diet by predator size in terms of percent by 


weight of main prey items was shown for each 10 cm FL group 


(when data are available). The prey size frequency data of 


the commercially important fish and crabs, and some forage 


fish, were also summarized by predator size groups. 


The commercially important prey found in this study 


include walleye pollock, Pacific cod, Pacific halibut, 


yellowfin sole (Pleuronectes asper), rock sole 


(Pleuronectes bilineatus), flathead sole (Hippoglossoides 


elassodon), rex sole (Errex zachirus), Dover sole 


(Microstomus pacificus), arrowtooth flounder, Greenland 


turbot (Reinhardtius hippoglossoides), Pacific herring 


(Clupea pallasi), coho salmon (Oncorhynchus kisutch), all 


rockfish species, Tanner crabs, and pandalid shrimp. 


Although capelin (Mallotus villosus), Pacific sand lance 


(Ammodytes hexapterus), and eulachon (Thaleichthys 


pacificus) are not commercially important fish in the Gulf 


of Alaska area, they are food of many commercially 

 9 

important fish that are economically important in other 


countries (e.g., Japan); therefore, data on these prey fish 


were also analyzed in this report. 

 10 

RESULTS AND DISCUSSION 


Overview 


The following species chapters summarize the 


consumption of commercially important and also non-


commercially important prey by each predator. Each species 


chapter is subdivided into subsections that provide 


information on general diet and effect of predator size. 


Walleye Pollock


 Walleye pollock (Theragra chalcogramma) ranked second 


(next to arrowtooth flounder) in biomass in the groundfish 


complex in the Gulf of Alaska in 2004. The exploitable 


biomass (age 3+) in 2004 was estimated at 765,180 t (NPFMC 


2004). Walleye pollock feed mainly on euphausiids, 


calanoid copepods, and other crustaceans. As pollock 


increase in size, they also eat juvenile pollock and other 


teleosts. Therefore, it is important to understand the 


food habits of pollock and their possible impact on pollock 


and other commercially important fishes. 


General Diet 


Walleye pollock fed mainly on zooplankton. 


Euphausiids, shrimp, and calanoid copepods were their most 


important prey. In addition, amphipods and planktonic 


tunicates (larvaceans) were also frequently found in 


pollock stomachs. Tables 3 - 4 (for 1999 and 2001, 

 11 

respectively) list the food items found in pollock stomachs,


mean percentage of the prey weight to the total food weight, 


and the mean percentage of the frequency of occurrence of 


the prey. Total number of stomachs with food, the total 


number of empty stomachs, and the number of the hauls were 


also listed in Tables 3 – 4. The percent by weight of the 


fish consumed was no more than 18% of the total stomach 


contents in each of the 2 years sampled (Tables 3 - 4). 


Capelin and juvenile walleye pollock were the most 


important prey fish consumed by pollock in this study. 


Other commercially important prey fish included Pacific 


herring, arrowtooth flounder, and flathead sole. Pacific 


sand lance and eelpout were also consumed by pollock. 


Comparing the diets from the 2 years indicates that 


the diet of walleye pollock in 1999 and 2001 was similar. 


In both years, the diets included about 11-22% (by weight) 


calanoid, 41-48% euphausiids, 13% shrimp, and 14-17% fish. 


However, fewer pollock were consumed (0.33% by weight) in 


1999 than in 2001 (5%)(Fig. 2 and Tables 3 and 4). During 


the same time period, the consumption of capelin declined 


from 5% (by weight) in 1999 to 0.13% in 2001; and the 


consumption of pandalid shrimp was about the same, 8.73% 


(by weight) in 1999 and 9.06% in 2001. 

 12 

Variation of Diet Based on Predator Size 


Figure 2 illustrates the main prey items of walleye 


pollock by predator fork length. In 1999 and 2001, 


calanoid copepods and amphipods were mainly consumed by 


smaller (< 40 cm FL) pollock. Euphausiids comprised the 


largest portion of pollock food through all size groups. 


Shrimp comprised the second largest portion of pollock food 


in fish larger than 30 cm FL. Cannibalism occurred mainly 


in the 30-39 cm FL size group and fish larger than 50 cm FL 


in 2001 (Fig. 2). Pollock comprised less than 10% (by 


weight) of the total stomach contents weight in each size 


group, respectively. 

 13 

Table 3.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Theragra chalcogramma (walleye pollock) collected in the Gulf of

 Alaska in 1999. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 3.83 0.58 

Gastropoda (snail) 0.37 0.02 

Pteropoda 0.54 0.24 

Thecosomata (pteropod) 1.87 0.15 

Gymnosomata (pteropod) 0.17 0.08 

Bivalvia (clam) 0.16 0.17 

Nuculana sp. (clam) 0.19 0.00 

Pectinidae (scallops) 0.16 0.00 

Teuthoidea (squid) 0.19 0.00 

Berryteuthis magister (squid) 0.19 0.42 

Crustacea 3.61 0.68 

Calanoida (copepod) 37.34 11.35 

Malacostraca 0.61 0.19 

Mysida (mysid) 1.54 0.03 

Mysidae (mysid) 3.35 0.29 

Cumacea (cumacean) 1.29 0.01 

Isopoda (isopod) 0.52 0.00 

Amphipoda (amphipod) 3.41 0.52 

Gammaridea (amphipod) 6.02 0.17 

Hyperiidea (amphipod) 4.02 0.03 

Hyperiidae (amphipod) 0.19 0.00 

Euphausiacea (euphausiid) 1.63 0.17 

Euphausiidae (euphausiid) 61.21 48.28 

Decapoda (shrimp and crab) 0.44 0.00 

Sergestes similis (Pacific sergestid) 0.16 0.27 

Caridea (shrimp) 6.24 2.46 

Pasiphaeidae (shrimp) 0.37 0.03 

Hippolytidae (shrimp) 0.20 0.08 

Eualus spp. (shrimp) 0.20 0.02 

Pandalidae (shrimp) 4.34 2.76 

Pandalus spp. (shrimp) 3.44 1.86 

Pandalus borealis (shrimp) 3.50 3.90 

Pandalus jordani (shrimp) 0.31 0.12 

Pandalopsis spp. (shrimp) 0.56 0.09 

Crangonidae (shrimp) 1.66 0.75 
 14

 Table 3.--Continued. 

Prey items Percent frequency Percent weight 

Crangon spp. (shrimp) 0.51 0.31 

Reptantia (crab) 1.28 0.05 

Paguridae (hermit crab) 0.17 0.00 

Decapoda brachyura (crab) 0.17 0.00 

Echiura (marine worm) 0.15 0.11 

Chaetognatha (arrow worm) 1.75 0.60 

Copelata (larvacea) 10.62 5.77 

Teleostei (fish) 6.74 3.02 

Non-gadoid fish remains 1.66 2.92 

Osmeridae (smelts) 1.96 3.55 

Mallotus villosus (capelin) 1.78 5.20 

Thaleichthys pacificus (eulachon) 0.82 1.84 

Gadidae (gadid fish) 0.20 0.05 

Theragra chalcogramma (walleye pollock) 0.19 0.33 

Zoarcidae (eelpout) 0.17 0.13 

Scorpaeniformes (rockfish and cottid) 0.19 0.01 

Ammodytes sp. (sand lance) 0.44 0.22 

Pleuronectidae (flatfish) 0.93 0.13 

Unidentified organic material 0.89 0.02 

Rocks 0.15 0.01 

Total non-empty stomachs = 497 

Total prey number = 575 

Total prey weight = 1460.091 g 

Total empty stomachs = 43 

Number of hauls = 45 

Full stomach summary statistics 

Average fork length = 38.33 cm 

Standard deviation of fork length = 5.79 cm 

Minimum fork length = 10 cm 

Maximum fork length = 69 cm 

Average fullness = 3.53 

Standard deviation of fullness = .36 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 33.37 cm 

Standard deviation of fork length = 15.65 cm 

Minimum fork length = 10 cm 

Maximum fork length = 60 cm 
 15 

Table 4.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Theragra chalcogramma (walleye pollock) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 1.57 0.09 

Phyllodocidae (polychaete) 0.18 0.02 

Gastropoda (snail) 0.40 0.02 

Pteropoda 0.83 0.12 

Thecosomata (pteropod) 2.08 0.03 

Bivalvia (clam) 0.62 0.01 

Cephalopoda (squid and octopus) 0.35 0.05 

Teuthoidea (squid) 0.48 0.05 

Crustacea 3.95 1.63 

Calanoida (copepod) 37.18 21.80 

Large calanoid (copepod) > 5mm 1.17 0.02 

Medium calanoid (copepod) 2-5mm 0.64 0.00 

Small calanoid (copepod) 2mm 0.20 0.00 

Harpacticoida (copepod) 0.10 0.00 

Mysida (mysid) 1.58 0.04 

Mysidae (mysid) 3.60 0.43 

Cumacea (cumacean) 1.83 0.79 

Amphipoda (amphipod) 1.24 0.14 

Gammaridea (amphipod) 5.73 2.18 

Hyperiidea (amphipod) 10.06 0.60 

Euphausiacea (euphausiid) 12.90 6.76 

Euphausiidae (euphausiid) 47.79 32.78 

Euphausia sp. (euphausiid) 0.31 0.01 

Euphausia pacifica (euphausiid) 1.43 0.30 

Thysanoessa sp. (euphausiid) 0.84 0.17 

Thysanoessa inermis (euphausiid) 1.60 1.31 

Decapoda (shrimp and crab) 0.29 0.01 

Caridea (shrimp) 6.98 1.70 

Pasiphaeidae (shrimp) 1.23 0.46 

Hippolytidae (shrimp) 1.21 0.40 

Eualus sp. (shrimp) 0.10 0.01 

Pandalidae (shrimp) 5.30 2.68 

Pandalus sp. (shrimp) 4.49 3.38 

Pandalus borealis (shrimp) 2.20 2.50 

Pandalus goniurus (shrimp) 0.45 0.32 
 16

 Table 4.--Continued. 

 Prey items Percent frequency Percent weight 

Pandalus montagui tridens (shrimp) 0.10 0.01 

Pandalopsis sp. (shrimp) 0.20 0.13 

Pandalopsis dispar (sidestripe shrimp) 0.10 0.04 

Crangonidae (shrimp) 2.21 0.54 

Crangon sp. (shrimp) 0.81 0.22 

Crangon dalli (shrimp) 0.10 0.11 

Crangon communis (shrimp) 0.19 0.01 

Argis sp. (shrimp) 0.09 0.01 

Argis dentata (shrimp) 0.28 0.05 

Reptantia (crab) 6.77 1.40 

Paguridae (hermit crab) 1.68 0.19 

Munida quadrispina (pinch bug) 0.10 0.07 

Majidae (spider crab) 0.10 0.05 

Chionoecetes spp. (snow and Tanner crab) 0.09 0.02 

Chionoecetes bairdi (Tanner crab) 0.27 0.21 

Echiura (marine worm) 0.10 0.44 

Ectoprocta (bryozoan) 0.10 0.00 

Chaetognatha (arrow worm) 0.40 0.04 

Copelata (larvacea) 7.17 1.75 

Teleostei (fish) 6.41 1.89 

Non-gadoid fish remains 1.58 1.58 

Clupea pallasi (Pacific herring) 0.10 0.72 

Osmeridae (smelts) 0.73 0.72 

Mallotus villosus (capelin) 0.33 0.13 

Gadidae (gadid fish) 0.40 0.40 

Theragra chalcogramma (walleye pollock) 1.81 4.93 

Zoarcidae (eelpout) 0.27 0.08 

Lycodes brevipes (shortfin eelpout) 0.09 0.04 

Cottidae (sculpin) 0.10 0.18 

Ammodytes sp. (sand lance) 0.80 1.76 

Ammodytes hexapterus (Pacific sand lance) 0.19 0.38 

Pleuronectidae (flatfish) 0.10 0.01 

Atheresthes stomias (arrowtooth flounder) 0.18 0.69 

Hippoglossoides elassodon (flathead sole) 0.14 0.35 

Unidentified organic material 0.30 0.01 

Unidentified eggs 0.10 0.00 

Unidentified worm-like organism 0.10 0.01 

Unidentified tube 0.10 0.00 
 17 

Table 4.--Continued. 

Total non-empty stomachs = 766 

Total prey number = 37157 

Total prey weight = 3215.506 g 

Total empty stomachs = 50 

Number of hauls = 70 

Full stomach summary statistics 

Average fork length = 37.28 cm 

Standard deviation of fork length = 5.17 cm 

Minimum fork length = 7 cm 

Maximum fork length = 75 cm 

Average fullness = 3.77 

Standard deviation of fullness = .37 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 31.30 cm 

Standard deviation of fork length = 18.01 cm 

Minimum fork length = 11 cm 

Maximum fork length = 68 cm 
 18 

1999


n = 115 34 37 175 113 23


100


Misc. prey 80
 Calanoid 

Amphipod


60
 Euphausiid 

Shrimp 

Misc. fish 40


Osmeridae 

Walleye pollock 

20


0 

15 25 35 45 55 65 

Predator fork length (cm) 

Precent by weight (%wt) 

2001


n = 147 176 57 135 202 49


100


80


60


40


20


0


15 25 35 45 55 65 

Predator fork length (cm) 

Percent by weight (%wt) 

Misc. prey 

Calanoid 

Amphipod


Euphausiid


Shrimp 

Misc. fish 

Osmeridae 

Walleye pollock 

Figure 2.--Variations in the main food items of walleye pollock, by predator 

size, in the Gulf of Alaska in 1999, and 2001. 

n = stomachs with food. 
 19 

Pacific Cod 


Pacific cod (Gadus macrocephalus), with an exploitable 


biomass (age 3+) of 472,000 t (NPFMC 2004), ranks third in 


abundance in the Gulf of Alaska groundfish community. The 


landings of Pacific cod totaled 54,591 t in 2004. Pacific 


cod feed both in the water column and in benthic areas; 


hence, they have a high variety of prey in their diets, 


including several commercially important fish and crab. 


General Diet 


The long list of prey items presented in Tables 5-6 


suggests that Pacific cod is an opportunistic feeder. 


These tables present the total number of stomachs with food, 


total empty stomachs, the mean percent frequency of 


occurrence, and the mean percent by weight of the prey 


items found in the stomachs in 1999 and 2001. Polychaetes 


were the most frequently found invertebrates in Pacific cod 


stomachs. However, shrimp (mainly pandalids) were 


relatively more important in terms of the percentage of the 


total stomach content weight. Pacific cod also consumed 


large amounts of Tanner crab (C. bairdi) (9%, and 10% of 


the total stomach content weight in 1999 and 2001, 


respectively). Decorator crabs (Oregonia spp.), lyre crabs 


(Hyas spp.), hermit crabs, euphausiids, amphipods, and 


marine worms were the other invertebrates consumed by 

 20 

Pacific cod. Of the fish consumed by Pacific cod, walleye 


pollock made up the highest proportion of the total stomach 


contents weight in 1999 (11%), and Pacific sand lance 


comprised the highest percentage (17% by weight) of Pacific 


cod diet in 2001. Other commercially important prey fish 


include arrowtooth flounder, flathead sole, and Pacific 


herring. Pacific cod also consumed many non-commercially 


important fish, such as capelin, eulachon, zoarcids, 


cottids, agonids, bathymasterids, and stichaeids. Fish 


processing offal (processed fish waste) was also consumed 


by Pacific cod in the Gulf of Alaska. 


Based on the data from 1999, we found pollock made up 


11% (by weight) of the Pacific cod diet; however, the 


percentage of pollock in the Pacific cod diet decreased to 


4% in 2001. The percentages of capelin consumed by Pacific 


cod were low: 0 and 2% in 1999 and 2001, respectively. 


Like pollock, pandalid shrimp were also important food of 


Pacific cod. However, the amounts of pandalid shrimp 


consumed by Pacific cod in those 2 years were relatively 

 21 

Table 5.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

total weight) of Gadus macrocephalus (Pacific cod) collected in the Gulf of Alaska in 

1999. 

Prey items Percent frequency Percent weight 

Porifera (sponge) 0.82 0.07 

Anthozoa (anemome) 0.40 0.29 

Polychaeta (worm) 42.37 9.41 

Nephtyidae (polychaete) 0.22 0.06 

Mollusca 0.53 0.03 

Gastropoda (snail) 3.05 0.09 

Bivalvia (clam) 2.94 0.10 

Nuculana sp. (clam) 0.14 0.00 

Nuculana fossa (clam) 0.43 0.00 

Yoldia sp. (clam) 2.27 0.10 

Mytilidae (mussel) 0.50 0.07 

Pectinidae (scallops) 0.27 0.00 

Teuthoidea (squid) 0.62 0.01 

Octopoda (octopus) 10.00 0.84 

Crustacea 2.84 0.38 

Calanoida (copepod) 0.57 0.00 

Mysidae (mysid) 1.37 0.02 

Cumacea (cumacean) 0.63 0.00 

Isopoda (isopod) 3.83 0.36 

Amphipoda (amphipod) 0.13 0.00 

Gammaridea (amphipod) 20.66 0.65 

Hyperiidea (amphipod) 0.30 0.00 

Caprellidea (amphipod) 0.30 0.00 

Euphausiacea (euphausiid) 1.78 0.79 

Euphausiidae (euphausiid) 23.03 5.66 

Decapoda (shrimp and crab) 0.50 0.15 

Natantia (shrimp) 2.90 0.23 

Caridea (shrimp) 8.50 0.43 

Hippolytidae (shrimp) 4.38 0.23 

Spirontocaris sp. (shrimp) 0.13 0.00 

Pandalidae (shrimp) 25.13 7.41 

Pandalus sp. (shrimp) 5.07 2.40 

Pandalus borealis (shrimp) 2.12 0.91 

Pandalus goniurus (shrimp) 1.57 0.39 

Pandalus jordani (shrimp) 2.36 2.15 
 22

 Table 5.--Continued. 

Prey items Percent frequency Percent weight 

Pandalus montagui tridens (shrimp) 2.24 0.65 

Crangonidae (shrimp) 17.96 1.90 

Crangon sp. (shrimp) 0.72 0.12 

Crangon alaskensis (shrimp) 0.13 0.02 

Crangon dalli (shrimp) 2.54 0.39 

Crangon communis (shrimp) 0.96 0.21 

Argis sp. (shrimp) 1.02 0.27 

Argis crassa 0.27 0.24 

Reptantia (crab) 14.55 1.16 

Decapoda Reptantia legs (for unident. crabs) 0.22 0.01 

Anomura (crab) 0.41 0.08 

Paguridae (hermit crab) 16.00 5.27 

Paguridae legs (hermit crabs) 0.93 0.10 

Pagurus sp. (hermit crab) 0.13 0.30 

Elassochirus cavimanus (purple hermit crab) 2.17 0.44 

Acantholithodes hispidus (fussy crab) 0.13 0.05 

Rhinolithodes wosnessenskii (rhinoceros crab) 0.33 0.29 

Munida quadrispina (pinch bug) 10.61 8.16 

Decapoda brachyura (crab) 1.02 0.12 

Oxyrhyncha 0.63 0.56 

Decapoda Reptantia legs (for unident. crabs) 0.13 0.01 

Oregonia sp. (decorator crab) 0.40 0.01 

Oregonia gracilis (decorator crab) 0.27 0.10 

Hyas sp. (lyre crab) 3.10 1.30 

Hyas lyratus (lyre crab) 0.50 0.45 

Hyas coarctatus (lyre crab) 0.30 0.19 

Chionoecetes sp. (snow and Tanner crab) 2.93 0.20 

Chionoecetes bairdi (Tanner crab) 16.96 9.22 

Telmessus cheiragonus (hair crab) 0.13 0.03 

Cancer oregonensis (pygmy Cancer crab) 4.58 2.37 

Pinnotheridae (pea crab) 2.43 0.27 

Pinnixa sp. (pea crab) 2.89 0.47 

Sipuncula (marine worm) 3.57 1.02 

Echiura (marine worm) 7.62 2.14 

Priapulida (worm) 0.15 0.03 

Ectoprocta (bryozoan) 0.36 0.01 

Ctenodiscus crispatus (mud sea star) 0.40 0.01 

Ophiurida (brittle star) 0.30 0.00 

Echinoidea (sea urchin and sand dollar) 0.29 0.01 

Echinacea sp. (sea urchin) 0.13 0.02 

Clypeasteroida (sand dollar) 0.13 0.00 
 23

 Table 5.--Continued. 

Prey items Percent frequency Percent weight 

Holothuroidea (sea cucumber) 0.50 0.11 

Teleostei (fish) 8.89 0.48 

Non-gadoid fish remains 17.89 1.08 

Clupea pallasi (Pacific herring) 0.13 0.01 

Osmeridae (smelts) 0.40 0.04 

Thaleichthys pacificus (eulachon) 0.50 0.98 

Gadidae (gadid fish) 1.07 0.53 

Theragra chalcogramma (walleye pollock) 5.57 11.34 

Zoarcidae (eelpout) 3.00 1.18 

Lycodes sp. (eelpout unidentified) 0.14 0.01 

Scorpaenidae 0.60 0.21 

Cottoidei (sculpin) 7.34 1.34 

Icelinus sp. 0.57 0.05 

Icelinus borealis (northern sculpin) 1.17 0.24 

Agonidae (poacher) 0.92 0.14 

Podothecus acipenserinus (sturgeon poacher) 0.50 0.48 

Bathymasteridae (ronquils) 4.09 1.53 

Bathymaster signatus (searcher) 1.36 2.14 

Anarhichas orientalis (Bering wolffish) 0.14 0.03 

Stichaeidae (prickleback) 3.85 0.34 

Pholidae (gunnel family) 0.50 0.13 

Ammodytes sp. (sand lance) 4.72 1.57 

Ammodytes hexapterus (Pacific sand lance) 2.67 1.43 

Pleuronectoidei (flatfish) 2.41 0.15 

Pleuronectidae (flatfish) 2.20 0.40 

Atheresthes evermanni (Kamchatka flounder) 0.50 0.28 

Atheresthes stomias (arrowtooth flounder) 1.29 0.72 

Hippoglossoides elassodon (flathead sole) 0.27 0.20 

Isopsetta isolepis (butter sole) 0.13 0.63 

Unidentified organic material 1.67 0.05 

Unidentified worm-like organism 2.33 0.45 

Fishery offal 0.22 0.18 

Unidentified tube 0.28 0.02 

Wood 0.62 0.03 

Unidentified algae 0.78 0.02 

Rocks 1.11 0.08 
 24 

Table 5.--Continued. 

Total non-empty stomachs = 453 

Total prey number = 1886 

Total prey weight = 16196.383 g 

Total empty stomachs = 1 

Number of hauls = 50 

Full stomach summary statistics 

Average fork length = 54.96 cm 

Standard deviation of fork length = 5.73 cm 

Minimum fork length = 14 cm 

Maximum fork length = 104 cm 

Average fullness = 4.34 

Standard deviation of fullness = .41 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 38.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 38 cm 

Maximum fork length = 38 cm 
 25 

Table 6.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Gadus macrocephalus (Pacific cod) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Phaeophycophyta (brown algae) 0.09 0.00 

Porifera (sponge) 0.32 0.07 

Cnidaria 0.16 0.01 

Polychaeta (worm) 25.58 7.14 

Polynoidae (polychaete) 0.09 0.00 

Phyllodocidae (polychaete) 0.32 0.00 

Alciopidae (polychaete) 0.09 0.03 

Arabellidae (polychaete) 0.08 0.07 

Opheliidae (polychaete) 0.10 0.01 

Mollusca 0.29 0.02 

Gastropoda (snail) 4.95 2.14 

Bivalvia (clam) 3.94 0.29 

Nuculana sp. (clam) 0.09 0.00 

Veneroida (clam) 0.09 0.00 

Cephalopoda (squid and octopus) 2.75 0.38 

Teuthoidea (squid) 3.48 1.55 

Octopoda (octopus) 3.12 1.43 

Crustacea 2.54 0.15 

Copepoda 0.35 0.03 

Cirripedia (barnacle) 0.09 0.00 

Mysida (mysid) 0.09 0.00 

Mysidae (mysid) 1.80 0.05 

Cumacea (cumacean) 3.50 1.14 

Isopoda (isopod) 3.37 0.77 

Gammaridea (amphipod) 18.32 3.54 

Ampeliscidae (amphipod) 0.36 0.01 

Hyperiidea (amphipod) 0.81 0.06 

Caprellidea (amphipod) 0.14 0.00 

Caprellidae (amphipod) 0.09 0.00 

Euphausiidae (euphausiid) 18.23 5.20 

Euphausia sp. (euphausiid) 0.32 0.00 

Euphausia pacifica (euphausiid) 0.32 0.01 

Thysanoessa sp. (euphausiid) 0.41 0.10 

Natantia (shrimp) 11.02 2.40 

Caridea (shrimp) 9.28 1.10 
 26 

Table 6.--Continued. 

Prey items Percent frequency Percent weight 

Hippolytidae (shrimp) 4.72 0.32 

Lebbeus sp. (shrimp) 0.19 0.05 

Lebbeus groenlandicus (shrimp) 0.19 0.03 

Eualus sp. (shrimp) 0.09 0.00 

Heptacarpus sp. (shrimp) 0.09 0.00 

Pandalidae (shrimp) 12.01 3.62 

Pandalus sp. (shrimp) 6.39 1.46 

Pandalus borealis (shrimp) 5.43 1.61 

Pandalus goniurus (shrimp) 0.35 0.02 

Pandalus jordani (shrimp) 0.17 0.16 

Pandalus montagui tridens (shrimp) 0.17 0.03 

Pandalus platyceros (shrimp) 0.91 0.65 

Pandalus stenolepis (shrimp) 0.09 0.00 

Crangonidae (shrimp) 11.89 1.70 

Crangon sp. (shrimp) 1.64 0.31 

Crangon alaskensis (shrimp) 0.43 0.07 

Crangon dalli (shrimp) 0.93 0.11 

Crangon communis (shrimp) 3.79 0.57 

Sclerocrangon 0.08 0.02 

Argis sp. (shrimp) 3.10 1.33 

Argis lar (shrimp) 0.25 0.09 

Argis dentata (shrimp) 0.26 0.01 

Argis ovifer (shrimp) 0.09 0.02 

Argis alaskensis (shrimp) 0.08 0.07 

Reptantia (crab) 12.25 3.67 

Paguridae (hermit crab) 8.65 3.71 

Paguridae legs (hermit crabs) 0.87 0.54 

Pagurus ochotensis (hermit crab) 0.09 0.12 

Elassochirus sp. 0.09 0.00 

Elassochirus cavimanus (purple hermit crab) 0.09 0.03 

Acantholithodes hispidus (fussy crab) 0.14 0.35 

Lithodes aequispina (golden king crab) 0.17 0.04 

Munida quadrispina (pinch bug) 2.11 1.07 

Decapoda brachyura (crab) 0.43 0.55 

Oxyrhyncha 0.09 0.00 

Majidae (spider crab) 0.27 0.13 

Oregonia sp. (decorator crab) 0.27 0.03 

Oregonia gracilis (decorator crab) 0.09 0.02 

Hyas sp. (lyre crab) 1.77 0.96 

Hyas lyratus (lyre crab) 0.81 0.79 

Chionoecetes spp. (snow and Tanner crab) 0.70 0.36 
 27

 Table 6.--Continued. 

 Prey items Percent frequency Percent weight 

Chionoecetes bairdi (Tanner crab) 15.10 9.94 

Chorilia longipes (decorator crab) 0.41 0.26 

Telmessus cheiragonus (hair crab) 0.16 0.01 

Cancer oregonensis (pygmy Cancer crab) 2.23 0.87 

Pinnotheridae (pea crab) 0.35 0.06 

Pinnixa sp. (pea crab) 3.09 0.38 

Echiura (marine worm) 4.83 1.36 

Ectoprocta (bryozoan) 0.35 0.04 

Asteroidea (starfish) 0.11 0.00 

Ophiurida (brittle star) 0.68 0.26 

Clypeasterina (sand dollar) 0.09 0.02 

Holothuroidea (sea cucumber) 0.20 0.12 

Urochordata (tunicate) 0.09 0.00 

Teleostei (fish) 1.99 0.09 

Non-gadoid fish remains 3.39 0.43 

Clupea pallasi (Pacific herring) 0.11 0.49 

Osmeridae (smelts) 1.60 1.24 

Mallotus villosus (capelin) 2.11 1.94 

Thaleichthys pacificus (eulachon) 0.09 0.20 

Gadidae (gadid fish) 2.15 1.66 

Theragra chalcogramma (walleye pollock) 2.90 4.16 

Zoarcidae (eelpout) 1.62 0.36 

Lycodes sp. (eelpout) 0.12 0.00 

Lycodes brevipes (shortfin eelpout) 0.17 0.05 

Macrouridae (rattail) 0.09 0.01 

Cottoidei (sculpin) 3.07 1.84 

Cottidae (sculpin) 2.03 0.46 

Artediellus sp. (sculpin) 0.09 0.08 

Dasycottus setiger (spinyhead sculpin) 0.12 0.17 

Gymnocanthus sp.(sculpin) 0.12 0.05 

Icelinus sp. (sculpin) 0.19 0.01 

Malacocottus zonurus (darkfin sculpin) 0.35 0.23 

Agonidae (poacher) 0.63 0.11 

Podothecus acipenserinus (sturgeon poacher) 0.12 0.02 

Bathymasteridae (ronquils) 0.09 0.07 

Stichaeidae (prickleback) 2.10 0.74 

Lumpenus maculatus (daubed shanny) 0.12 0.01 

Ammodytes sp. (sand lance) 1.51 1.10 

Ammodytes hexapterus (Pacific sand lance) 18.67 15.77 

Pleuronectoidei (flatfish) 0.78 0.42 

Pleuronectidae (flatfish) 2.77 2.29 
 28 

Table 6.—Continued. 

 Prey items Percent frequency Percent weight 

Unidentified organic material 

Unidentified worm-like organism 

Unidentified algae 

0.58 

0.32 

0.44 

0.29 

0.02 

0.02 

Total non-empty stomachs = 803 

Total prey number = 14483 

Total prey weight = 16083.818 g 

Total empty stomachs = 35 

Number of hauls = 77 

Full stomach summary statistics 

Average fork length = 48.92 cm 

Standard deviation of fork length = 4.60 cm 

Minimum fork length = 9 cm 

Maximum fork length = 92 cm 

Average fullness = 4.14 

Standard deviation of fullness = .41 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 54.71 cm 

Standard deviation of fork length = 18.71 cm 

Minimum fork length = 22 cm 

Maximum fork length = 87 cm 
 29 

similar (14% in 1999 and 8% in 2001). The percentages of 


Tanner crab consumed were also similar (9% (by weight) in 


1999 and 10% in 2001). 


Variation of Diet Based on Predator Size 


Figure 3 shows that Pacific cod ate more fish with 


increasing cod size, especially for larger cod (>70 cm FL). 


The fish consumed comprised more than 45% of the total 


stomach contents in this larger size group of Pacific cod 


the 2 years that were sampled. Only this group of larger 


Pacific cod (>70 cm FL) consumed a significant amount of 


walleye pollock (35% (by weight) in 1999 and 11% in 2001). 


Smaller size groups (<60 cm FL) consumed very small amounts 


of pollock (<4%). All but the largest size group in 1999 


and 2001 consumed a fair amount of shrimp (>10%). Tanner 


crabs were mainly consumed by Pacific cod larger than 30 cm 


FL. The smallest size group (<20 cm FL) of cod ate a large 


amount (>24%) of miscellaneous prey (mainly amphipods and 


mysids). 

 30 

1999


n = 9 28 19 78 161 111 47 

15 25 35 45 55 65 75 

Predator fork length (cm) 

2001 

n = 24 121 86 138 150 213 71 

15 25 35 45 55 65 75 

Predator fork length (cm) 

0 

20 

40 

60 

80 

100 

Percent by weight (%wt) 

Misc. prey 

Polychaete 

Euphausiid 

Shrimp 

Tanner crab 

Other crab 

Misc. fish 

Flatfish 

Walleye pollock 

0 

20 

40 

60 

80 

100 

Percent by weight (%wt) 

Misc. prey 

Polychaete 

Euphausiid 

Shrimp 

Tanner crab 

Other crab 

Misc. fish 

Flatfish 

Walleye pollock 

Figure 3.--Variations in the main food items of Pacific cod, by predator 

size, in the Gulf of Alaska in 1999, and 2001. 

n = stomachs with food. 
 31 

Arrowtooth Flounder 


Arrowtooth flounder (Atheresthes stomias), with an 


exploitable biomass of 2,453,390 t in 2004, ranked first in 


the total groundfish biomass in the Gulf of Alaska(NPFMC 


2004). Arrowtooth flounder is a large flatfish with a 


symmetrical mouth and sharp teeth that feeds on 


commercially important fish such as walleye pollock and 


capelin as well as shrimp and other crustaceans. Therefore,


based on its feeding behavior and its high abundance in the 


Gulf of Alaska area, arrowtooth flounder is important to 


study because of its potential impact on commercially 


important species. 


General Diet 


Tables 7 and 8 list the total number of stomachs with 


food, total number of empty stomachs, the mean percent 


frequency of occurrence and the mean percent by weight of 


the prey items found in arrowtooth flounder stomachs in 


1999, and 2001. Euphausiids and pandalid shrimp were the 


most important invertebrate food of arrowtooth flounder. 


However, fish comprised the largest amounts of the total 


stomach contents of arrowtooth flounder (57% and 73% by 


weight in 1999 and 2001, respectively). Walleye pollock 


was the most important prey fish of arrowtooth flounder; 


followed by Pacific sand lance and capelin. Arrowtooth 

 32 

flounder also consumed some eulachon, Pacific herring, 


arrowtooth flounder, flathead sole, Lepidopsetta spp., and 


some non-commercially important species (e.g., zoarcids, 


cottids, searcher, ronquils, stichaeids, bathylagids, and 


myctophids).


The percentage of pollock in the diet of arrowtooth 


flounder was 14% and 31% (by weight) in 1999 and 2001, 


respectively. Smelts (mainly capelin) made up 8% and 13% 


of the diet (by weight) of arrowtooth flounder in 1999 and 


2001, respectively. The percentages of pandalid shrimp in 


the diet of arrowtooth flounder was 12% in 1999 and 7% in 


2001.


Variations of Diet Based on Predator Size 


Figure 4 illustrates the percentage by weight of the 


main prey items for different arrowtooth flounder size 


groups in 1999 and 2001. In general, larger arrowtooth 


flounder (> 40 cm FL) fed mainly on fish. Walleye pollock 


were the predominant prey fish for this size group of 


arrowtooth flounder. In 2001, pollock made up 31% of the 


total stomach contents. Smaller arrowtooth flounder (<40 


cm FL) fed mainly on euphausiids and pandalid shrimp (Fig. 


4). 

 33 

Table 7.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

of total weight) of Atheresthes stomias (arrowtooth flounder) collected in the Gulf of 

Alaska in 1999. 

 Prey items Percent frequency Percent weight 

Porifera (sponge) 0.38 0.03 

Polychaeta (worm) 2.11 0.42 

Hirudinea (leech) 0.32 0.52 

Pteropoda (Mollusca) 0.22 0.00 

Bivalvia (clam) 0.12 0.00 

Teuthoidea (squid) 1.62 0.13 

Octopoda (octopus) 0.13 0.01 

Crustacea 3.19 1.34 

Calanoida (copepod) 3.72 2.20 

Mysidae (mysid) 1.43 0.02 

Cumacea (cumacean) 0.16 0.00 

Gammaridea (amphipod) 2.21 0.04 

Euphausiacea (euphausiid) 7.54 4.49 

Euphausiidae (euphausiid) 30.00 17.82 

Thysanoessa spinifera (euphausiid) 0.26 0.78 

Caridea (shrimp) 3.25 0.92 

Pandalidae (shrimp) 6.99 3.47 

Pandalus sp. (shrimp) 1.23 2.08 

Pandalus borealis (shrimp) 3.62 3.49 

Pandalus goniurus (shrimp) 1.19 2.44 

Pandalus jordani (shrimp) 0.22 0.15 

Crangonidae (shrimp) 2.78 0.99 

Crangon sp. (shrimp) 0.77 0.11 

Crangon alaskensis (shrimp) 0.09 0.02 

Crangon dalli (shrimp) 0.21 0.06 

Argis sp. (shrimp) 0.27 0.34 

Reptantia (crab) 2.77 0.41 

Chionoecetes bairdi (Tanner crab) 0.22 0.09 

Ectoprocta (bryozoan) 0.16 0.02 

Chaetognatha (arrow worm) 0.16 0.00 

Copelata (larvacea) 0.16 0.01 

Teleostei (fish) 7.36 3.67 

Non-gadoid fish remains 8.17 6.97 

Clupeidae 0.24 0.38 

Osmeridae (smelts) 3.74 4.06 

Mallotus villosus (capelin) 1.37 3.75 

Gadidae (gadid fish) 3.12 5.03 

Theragra chalcogramma (walleye pollock) 6.07 13.81 

Zoarcidae (eelpout) 1.42 1.41 

Lycodes brevipes (shortfin eelpout) 0.12 0.15 

Cottoidei (sculpin) 0.08 0.01 

Bathymasteridae (ronquils) 0.13 0.02 

Bathymaster signatus (searcher) 0.09 0.99 

Stichaeidae (prickleback) 0.86 1.45 

Lumpenus maculatus (daubed shanny) 0.58 0.84 

Ammodytes sp. (sand lance) 1.48 2.16 

Ammodytes hexapterus (Pacific sand lance) 5.71 6.83 

Pleuronectoidei (flatfish) 0.83 1.06 
 34

 Table 7.--Continued. 

Prey items Percent frequency Percent weight 

Pleuronectidae (flatfish) 0.21 0.23 

Atheresthes stomias (arrowtooth flounder) 0.42 1.74 

Hippoglossoides elassodon (flathead sole) 0.38 2.38 

Unidentified organic material 0.80 0.55 

Fishery offal 0.91 0.09 

Unidentified algae 0.12 0.01 

Total non-empty stomachs = 499 

Total prey number = 955 

Total prey weight = 4896.509 g 

Total empty stomachs = 536 

Number of hauls = 77 

Full stomach summary statistics 

Average fork length = 41.30 cm 

Standard deviation of fork length = 5.05 cm 

Minimum fork length = 9 cm 

Maximum fork length = 80 cm 

Average fullness = 3.90 

Standard deviation of fullness = .48 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 41.29 cm 

Standard deviation of fork length = 12.55 cm 

Minimum fork length = 15 cm 

Maximum fork length = 78 cm 
 35 

Table 8.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Atheresthes stomias (arrowtooth flounder) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 0.84 0.05 

Nephtyidae (polychaete) 0.25 0.58 

Gastropoda (snail) 0.06 0.00 

Nuculana sp. (clam) 0.06 0.00 

Cephalopoda (squid and octopus) 0.24 0.18 

Teuthoidea (squid) 2.18 2.16 

Berryteuthis magister (squid) 0.05 0.21 

Crustacea 0.30 0.03 

Calanoida (copepod) 0.51 0.00 

Mysida (mysid) 1.14 0.15 

Mysidae (mysid) 0.05 0.00 

Cumacea (cumacean) 0.13 0.10 

Gammaridea (amphipod) 0.90 0.12 

Hyperiidea (amphipod) 0.45 0.00 

Euphausiacea (euphausiid) 4.62 1.86 

Euphausiidae (euphausiid) 23.90 9.63 

Euphausia sp. (euphausiid) 0.06 0.11 

Euphausia pacifica (euphausiid) 0.19 0.01 

Thysanoessa sp. (euphausiid) 0.39 0.39 

Thysanoessa inermis (euphausiid) 1.56 1.55 

Thysanoessa longipes (euphausiid) 0.08 0.02 

Thysanoessa raschi (euphausiid) 0.14 0.07 

Thysanoessa spinifera (euphausiid) 0.24 0.08 

Natantia (shrimp) 3.78 0.69 

Caridea (shrimp) 2.77 1.03 

Pasiphaea pacifica (shrimp) 0.08 0.05 

Hippolytidae (shrimp) 0.81 0.06 

Pandalidae (shrimp) 6.23 3.31 

Pandalus sp. (shrimp) 2.72 1.88 

Pandalus borealis (shrimp) 2.25 1.32 

Pandalus goniurus (shrimp) 0.14 0.02 

Pandalus jordani (shrimp) 0.30 0.38 

Pandalus montagui tridens (shrimp) 0.84 0.26 

Pandalus hypsinotus (humpback shrimp) 0.08 0.16 

Pandalopsis sp. (shrimp) 0.17 0.03 

Pandalopsis dispar (sidestripe shrimp) 0.05 0.05 

Crangonidae (shrimp) 1.45 0.26 

Crangon sp. (shrimp) 0.50 0.04 

Crangon dalli (shrimp) 0.65 0.28 

Crangon communis (shrimp) 0.14 0.03 

Argis dentata (shrimp) 0.06 0.05 

Reptantia (crab) 0.18 0.02 

Munida quadrispina (pinch bug) 0.20 0.02 

Ectoprocta (bryozoan) 0.06 0.00 

Chaetognatha (arrow worm) 0.12 0.00 

Teleostei (fish) 4.15 0.87 

Non-gadoid fish remains 5.52 2.29 

Clupeidae 0.08 0.06 
 36 

Table 8.--Continued. 

Prey items Percent frequency Percent weight 

Clupea pallasi (Pacific herring) 0.19 0.38 

Osmeridae (smelts) 8.99 6.77 

Mallotus villosus (capelin) 6.44 5.97 

Thaleichthys pacificus (eulachon) 0.13 0.13 

Bathylagidae (deepsea smelts) 0.11 0.05 

Myctophidae (lanternfish) 0.05 0.00 

Stenobrachius leucopsarus (northern lampfish) 0.08 0.28 

Gadidae (gadid fish) 6.88 5.87 

Gadus macrocephalus (Pacific cod) 0.06 0.09 

Theragra chalcogramma (walleye pollock) 18.13 31.42 

Zoarcidae (eelpout) 1.39 1.15 

Lycodes sp. (eelpout unid) 0.09 0.29 

Sebastes sp. (rockfish) 0.09 0.66 

Sebastolobus alascanus (shortspine thornyhead) 0.36 1.02 

Cottoidei (sculpin) 0.38 0.75 

Cottidae (sculpin) 0.11 0.29 

Agonidae (poacher) 0.15 0.06 

Bathymasteridae (ronquils) 0.08 0.12 

Bathymaster sp. (searcher) 0.15 0.13 

Bathymaster signatus (searcher) 0.06 0.06 

Stichaeidae (prickleback) 0.83 0.64 

Ammodytes sp. (sand lance) 2.70 4.11 

Ammodytes hexapterus (Pacific sand lance) 5.83 5.78 

Pleuronectoidei (flatfish) 0.26 0.62 

Pleuronectidae (flatfish) 1.01 1.33 

Atheresthes sp. 0.15 0.48 

Atheresthes stomias (arrowtooth flounder) 0.18 0.90 

Lepidopsetta sp. (rock sole type) 0.08 0.11 

Lepidopsetta bilineatus (southern rock sole) 0.06 0.00 

Unidentified organic material 0.11 0.02 

Fishery offal 0.07 0.02 

Unidentified tube 0.25 0.01 

Unidentified algae 0.05 0.00 
 37 

Table 8.--Continued. 

Total non-empty stomachs = 1359 

Total prey number = 2346 

Total prey weight = 26954.353 g 

Total empty stomachs = 424 

Number of hauls = 133 

Full stomach summary statistics 

Average fork length = 37.66 cm 

Standard deviation of fork length = 4.93 cm 

Minimum fork length = 13 cm 

Maximum fork length = 81 cm 

Average fullness = 4.50 

Standard deviation of fullness = .36 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 42.54 cm 

Standard deviation of fork length = 16.71 cm 

Minimum fork length = 16 cm 

Maximum fork length = 163 cm 
 38 

1999


Percent by weight (%wt) Percent by weight (%wt)

n = 29 109 111 116 104 30


100


80


Misc. prey 

Euphausiid 

60
 Shrimp 

Misc. fish 

Ammodytidae 40


Osmeridae 

Walleye pollock 

20


0 

15 25 35 45 55 65 

Predator fork length (cm) 

2001


n = 157 390 264 258 197 93


100


80


15 25 35 45 55 65 

Predator fork length (cm) 

Misc. prey 

Euphausiid 

60
 Shrimp 

Misc. fish


40
 Osmeridae 

Walleye pollock 

20


0 

Figure 4.--Variations in the main food items of arrowtooth flounder, 

by predator size, in the Gulf of Alaska in 1999 and 2001. 

n = stomachs with food 
 39 

Pacific Halibut 


Pacific halibut (Hippoglossus stenolepis) had an 


exploitable biomass of about 91,818 t in the Gulf of Alaska 


(NPFMC Regulatory areas 3A and 3B) in 2004. In that same 


year the commercial catch in the Gulf of Alaska (areas 3A 


and 3B) was 18,481 t (IPHC 2004). Pacific halibut are 


important predators feeding on fish, crab, and squid. 


Knowledge of their food habits is needed to describe their 


potential impact on other commercially important species in 


the Gulf of Alaska area. 


General Diets 


Tables 9 and 10 list the total number of Pacific 


halibut stomachs containing food, the empty stomachs, the 


mean percent frequency of occurrence of the prey, and the 


mean percent by weight of the prey found in Pacific halibut 


stomachs collected in 1999 and 2001. Walleye pollock was 


the most important prey. In terms of weight, pollock 


comprised 10 and 22% of the total stomach contents in 1999 


and 2001, respectively. Pacific sand lance made up 17% and 


10% of the total stomach contents weight in the 2 years. 


Capelin comprised 6% and 4% of the total stomach contents 


weight in 1999 and 2001, respectively. Arrowtooth 


flounder comprised 4% and 2.5% of the total stomach 

 40 

contents weight for 1999 and 2001, respectively. Other 


commercially important fish consumed by Pacific halibut 


included Pacific cod, eulachon, Pacific ocean perch, 


flathead sole, southern rock sole, yellowfin sole, and 


young Pacific halibut. Pacific halibut also consumed some 


fishery offal. Many non-commercially important fish (e.g., 


cottids, agonids, cyclopterids, bathymasterids, and 


stichaeids) were also consumed by Pacific halibut; however, 


they played a minor role in the diet of the Pacific halibut.


Hermit crabs were the most important invertebrate prey 


of Pacific halibut; they comprised 17% and 10% of the total 


stomach contents weight in 1999 and 2001, respectively. 


Less important invertebrate prey included Tanner crabs (< 1 


to 6%), lyre crab (Hyas spp.) (3-7%), cancer crab (Cancer 


oregonensis) (6-10%), and decorator crab (Oregonia spp.) 


(1-3%). All of the other invertebrates consumed 


(polychaetes, gastropods, clams, cephalopods, shrimp, and 


other crustaceans) were found less frequently and were 


considered to be relatively less important as food of 


Pacific halibut. 

 41 

Table 9.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

total weight) of Hippoglossus stenolepis (Pacific halibut) collected in the Gulf of Alaska 

in 1999. 

Prey items Percent frequency Percent weight 

Porifera (sponge) 1.26 0.40 

Anthozoa (anemome) 1.30 0.56 

Polychaeta (worm) 3.08 0.23 

Mollusca 0.83 1.33 

Gastropoda (snail) 0.61 0.03 

Bivalvia (clam) 6.03 0.23 

Cephalopoda (squid and octopus) 2.16 0.30 

Octopoda (octopus) 1.52 0.00 

Isopoda (isopod) 1.14 0.02 

Natantia (shrimp) 5.13 1.48 

Caridea (shrimp) 0.61 0.02 

Hippolytidae (shrimp) 3.04 0.16 

Eualus sp. (shrimp) 1.79 0.05 

Pandalidae (shrimp) 2.44 0.43 

Crangonidae (shrimp) 4.63 0.95 

Crangon sp. (shrimp) 4.35 1.25 

Crangon alaskensis (shrimp) 0.65 0.03 

Crangon dalli (shrimp) 2.67 0.62 

Argis lar (shrimp) 0.70 0.08 

Reptantia (crab) 3.63 0.57 

Paguridae (hermit crab) 39.24 16.21 

Paguridae legs (hermit crabs) 2.60 0.01 

Pagurus brandti (sponge hermit crab) 0.65 0.60 

Decapoda brachyura (crab) 11.69 0.68 

Oxyrhyncha 1.14 0.02 

Oregonia sp. (decorator crab) 13.79 11.01 

Hyas sp. (lyre crab) 3.50 1.38 

Hyas lyratus (lyre crab) 13.42 1.98 

Chionoecetes sp. (snow and Tanner crab) 2.27 0.08 

Chionoecetes bairdi (Tanner crab) 0.35 0.05 

Cancer oregonensis (pygmy Cancer crab) 25.83 10.15 

Pinnixa sp. (pea crab) 0.35 0.01 

Sipuncula (marine worm) 0.83 0.07 

Ophiurida (brittle star) 1.30 0.00 

Clypeasteroida (sand dollar) 0.65 0.06 
 42

 Table 9.--Continued. 

Prey items Percent frequency Percent weight 

Teleostei (fish) 1.65 0.00 

Non-gadoid fish remains 12.60 0.20 

Clupeidae 1.60 1.24 

Mallotus villosus (capelin) 6.21 5.92 

Gadidae (gadid fish) 11.32 1.35 

Theragra chalcogramma (walleye pollock) 5.55 10.03 

Zoarcidae (eelpout) 0.61 0.57 

Cottoidei (sculpin) 2.00 0.03 

Triglops scepticus (spectacled sculpin) 0.61 0.08 

Podothecus acipenserinus (sturgeon poacher) 1.14 5.70 

Stichaeidae (prickleback) 1.58 0.44 

Pholidae (gunnel family) 0.61 0.10 

Pholis clemensi (longfin gunnel) 0.83 0.32 

Ammodytes sp. (sand lance) 6.36 3.82 

Ammodytes hexapterus (Pacific sand lance) 19.91 13.30 

Pleuronectidae (flatfish) 1.30 0.03 

Atheresthes stomias (arrowtooth flounder) 1.52 4.17 

Hippoglossus stenolepis (Pacific halibut) 1.14 0.12 

Unidentified organic material 0.61 0.40 

Unidentified worm-like organism 2.34 0.12 

Unidentified algae 1.26 1.01 

Total non-empty stomachs = 134 

Total prey number = 471 

Total prey weight = 3690.757 g 

Total empty stomachs = 35 

Number of hauls = 11 

Full stomach summary statistics 

Average fork length = 57.05 cm 

Standard deviation of fork length = 7.16 cm 

Minimum fork length = 17 cm 

Maximum fork length = 114 cm 

Average fullness = 4.64 

Standard deviation of fullness = .43 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 62.94 cm 

Standard deviation of fork length = 20.79 cm 

Minimum fork length = 37 cm 

Maximum fork length = 107 cm 
 43 

Table 10.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Hippoglossus stenolepis (Pacific halibut) collected in the Gulf of 

Alaska in 2001.

 Prey items Percent frequency Percent weight 

Porifera (sponge) 0.22 0.02 

Cnidaria 0.19 0.00 

Anthozoa (anemome) 0.42 0.22 

Polychaeta (worm) 2.61 0.13 

Aphroditidae (sea mouse) 0.20 0.06 

Nephtyidae (polychaete) 0.13 0.25 

Hirudinea (leech) 0.14 0.09 

Mollusca 0.68 0.02 

Gastropoda (snail) 0.79 0.01 

Bivalvia (clam) 3.56 0.37 

Pectinidae (scallops) 0.17 0.00 

Cephalopoda (squid and octopus) 0.80 0.23 

Teuthida (squid) 1.29 1.01 

Octopoda (octopus) 4.91 2.63 

Octopodidae (octopus) 0.10 0.20 

Cirripedia (barnacle) 0.07 0.00 

Mysida (mysid) 0.51 0.00 

Isopoda (isopod) 1.40 0.52 

Gammaridea (amphipod) 1.31 0.01 

Hyperiidea (amphipod) 0.13 0.00 

Caprellidea (amphipod) 0.15 0.00 

Euphausiacea (euphausiid) 0.76 0.10 

Euphausiidae (euphausiid) 1.59 0.39 

Thysanoessa sp. (euphausiid) 0.07 0.00 

Thysanoessa inermis (euphausiid) 0.06 0.02 

Natantia (shrimp) 0.51 0.03 

Caridea (shrimp) 0.55 0.01 

Hippolytidae (shrimp) 0.97 0.11 

Lebbeus sp. (shrimp) 0.42 0.09 

Lebbeus groenlandicus (shrimp) 0.78 0.21 

Pandalidae (shrimp) 0.97 0.07 

Pandalus sp. (shrimp) 1.21 0.20 

Pandalus jordani (shrimp) 0.11 0.00 

Pandalus montagui tridens (shrimp) 0.38 0.21 
 44

 Table 10.--Continued. 

 Prey items Percent frequency Percent weight 

Crangonidae (shrimp) 2.03 0.09 

Crangon sp. (shrimp) 0.41 0.02 

Crangon alaskensis (shrimp) 0.07 0.02 

Crangon stylirostris (shrimp) 0.07 0.02 

Crangon dalli (shrimp) 0.11 0.00 

Crangon communis (shrimp) 0.09 0.00 

Sclerocrangon sp. (shrimp) 0.08 0.01 

Sclerocrangon boreas (shrimp) 0.07 0.00 

Rhynocrangon alata (saddle-back shrimp) 1.04 0.37 

Argis sp. (shrimp) 0.35 0.01 

Argis crassa (shrimp) 0.07 0.01 

Argis levior (shrimp) 0.14 0.01 

Reptantia (crab) 4.08 0.44 

Paguridae (hermit crab) 25.23 6.84 

Paguridae legs (hermit crabs) 2.11 0.42 

Pagurus sp. (hermit crab) 2.09 0.51 

Pagurus ochotensis (hermit crab) 0.07 0.00 

Pagurus brandti (sponge hermit crab) 0.08 0.00 

Elassochirus sp. 3.67 1.87 

Elassochirus tenuimanus 0.36 0.02 

Elassochirus cavimanus (purple hermit crab) 0.67 0.04 

Placetron wosnessenskii (scale crab) 0.14 0.00 

Rhinolithodes wosnessenskii (rhinoceros crab) 0.31 0.52 

Munida quadrispina (pinch bug) 1.74 1.20 

Decapoda brachyura (crab) 0.28 0.01 

Majidae (spider crab) 2.12 0.13 

Oregonia sp. (decorator crab) 3.07 1.38 

Oregonia gracilis (decorator crab) 2.63 1.08 

Oregonia bifurca (decorator crab) 1.31 0.56 

Hyas sp. (lyre crab) 10.20 3.79 

Hyas lyratus (lyre crab) 7.37 2.79 

Hyas coarctatus (lyre crab) 0.35 0.35 

Chionoecetes spp. (snow and Tanner crab) 1.85 0.77 

Chionoecetes opilio (snow crab) 1.26 1.02 

Chionoecetes bairdi (Tanner crab) 10.25 4.37 

Pugettia gracilis (kelp crab) 0.22 0.00 

Chorilia longipes (decorator crab) 1.06 0.13 

Atelecyclidae (crab) 0.07 0.05 

Cancridae (crab) 0.30 0.00 

Cancer sp. (crab) 0.32 0.00 
 45 

Table 10.--Continued. 

 Prey items Percent frequency Percent weight 

Cancer oregonensis (pygmy Cancer crab) 15.58 5.80 

Pinnotheridae (pea crab) 0.10 0.02 

Pinnixa sp. (pea crab) 1.01 0.04 

Sipuncula (marine worm) 0.40 0.16 

Echiura (marine worm) 0.71 0.19 

Ectoprocta (bryozoan) 0.22 0.06 

Ophiurida (brittle star) 1.45 0.07 

Echinoidea (sea urchin and sand dollar) 0.08 0.00 

Ascidia sp. (tunicate) 0.08 0.01 

Thaliacea (pelagic salp) 0.15 0.00 

Teleostei (fish) 2.02 0.41 

Non-gadoid fish remains 7.23 0.54 

Clupeidae 0.30 0.17 

Clupea pallasi (Pacific herring) 0.66 1.41 

Salmonidae (salmon, whitefish) 1.01 1.00 

Oncorhynchus keta (chum salmon) 0.17 0.81 

Osmeridae (smelts) 2.08 0.40 

Mallotus villosus (capelin) 4.91 3.78 

Thaleichthys pacificus (eulachon) 0.34 0.09 

Gadidae (gadid fish) 2.99 2.98 

Gadus macrocephalus (Pacific cod) 0.19 0.85 

Theragra chalcogramma (walleye pollock) 17.76 22.19 

Zoarcidae (eelpout) 0.20 0.13 

Scorpaenidae (rockfish) 0.11 0.02 

Sebastes sp. (rockfish) 0.45 0.04 

Sebastes alutus (Pacific ocean perch) 0.34 0.48 

Cottoidei (sculpin) 4.00 0.81 

Cottidae (sculpin) 0.83 0.54 

Rhamphocottus richardsoni (grunt sculpin) 0.44 0.20 

Agonidae (poacher) 0.59 0.10 

Podothecus acipenserinus (sturgeon poacher) 0.08 0.02 

Cyclopteridae (snailfish) 0.15 0.01 

Aptocyclus ventricosus (smooth lumpsucker) 0.17 0.11 

Eumicrotremus orbis (Pacific spiny lumpsucker) 0.16 0.07 

Bathymasteridae (ronquils) 0.78 0.39 

Bathymaster sp. (searcher) 0.51 0.05 

Stichaeidae (prickleback) 1.10 0.16 

Lumpenus sagitta (snake prickleback) 0.20 0.04 

Pholidae (gunnel family) 0.44 0.07 

Pholis sp. (gunnel) 0.16 0.03 

Ammodytes sp. (sand lance) 8.09 4.64 
 46

 Table 10.--Continued. 

 Prey items Percent frequency Percent weight 

Ammodytes hexapterus (Pacific sand lance) 7.04 5.38 

Pleuronectoidei (flatfish) 1.61 0.12 

Pleuronectidae (flatfish) 4.17 2.56 

Atheresthes sp. 0.98 1.43 

Atheresthes evermanni (Kamchatka flounder) 0.10 0.31 

Atheresthes stomias (arrowtooth flounder) 1.32 0.76 

Hippoglossoides elassodon (flathead sole) 0.67 0.53 

Lepidopsetta bilineatus (southern rock sole) 0.15 0.88 

Limanda sp. 0.20 0.30 

Limanda aspera (yellowfin sole) 0.45 0.67 

Unidentified organic material 0.50 0.02 

Unidentified worm-like organism 0.68 0.03 

Fishery offal 1.10 1.90 

Unidentified tube 0.20 0.00 

Overboard material (non-fishery) 0.08 0.00 

Unidentified algae 0.34 0.00 

Rocks 0.07 0.01 

Total non-empty stomachs = 808 

Total prey number = 5401 

Total prey weight = 62323.362 g 

Total empty stomachs = 81 

Number of hauls = 99 

Full stomach summary statistics 

Average fork length = 61.63 cm 

Standard deviation of fork length = 7.44 cm 

Minimum fork length = 13 cm 

Maximum fork length = 126 cm 

Average fullness = 4.67 

Standard deviation of fullness = .44 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 64.75 cm 

Standard deviation of fork length = 21.77 cm 

Minimum fork length = 19 cm 

Maximum fork length = 128 cm 
 47

 Comparing the diet differences between 1999 and 2001, 


we noticed that miscellaneous fish (including all fishes 


other than walleye pollock), hermit crab, and other crabs 


(including lyre, cancer, and decorator crabs) were the 


three main prey groups of Pacific halibut. The percentages 


of these three main prey groups in the diet of Pacific 


halibut in 1999 and 2001 were similar. Miscellaneous fish 


comprised 37% and 33% of the stomach contents in 1999 and 


2001, respectively, and the other crabs category comprised 


26% and 18% of the stomach contents of Pacific halibut in 


those 2 years. 


Variation of Diet Based on Predator Size 


The diet of Pacific halibut varied greatly by predator 


size (Fig. 5). Miscellaneous prey fish (mainly capelin, 


Pacific sand lance, cottids, zoarcids, stichaeids, and 


flatfish) were important food for all sizes of Pacific 


halibut, whereas walleye pollock were mainly consumed by 


larger Pacific halibut (> 80 cm FL). Crabs (Tanner crabs, 


decorator crabs, lyre crabs, and cancer crabs) were the 


main food of Pacific halibut between 50 and 80 cm FL. 


Hermit crabs (pagurids) were important food (> 23% by 


weight) for Pacific halibut less than 60 cm FL, especially 


for fish less than 40 cm long (they comprised 47% and 40% 

 48 

of the total stomach contents weight in 1999 and 2001, 


respectively). Shrimp were also important food of Pacific 


halibut less than 30 cm FL. 

 49 

1999


n = 17 24 17 25 22 18 11


100


Misc. prey


80
 Other crab 

Shrimp 60


Hermit crab


40


Tanner crab


20
 Misc. fish


Walleye pollock 

0 

2001


n = 91 109 139 132 107 103 130


Percent by weight (%

wt) 

25 35 45 55 65 75 85 

Predator fork length (cm) 

Percent by weight (%

wt) 100


80


60


40


20


0 

25 35 45 55 65 75 85 

Predator fork length (cm) 

Misc. prey 

Other crab 

Shrimp 

Hermit crab 

Tanner crab 

Misc. fish 

Walleye pollock 

Figure 5.--Variations in the main food items of Pacific halibut, by predator 

size, in the Gulf of Alaska in 1999 and 2001. 

n = stomachs with food. 
 50 

Sablefish 


Sablefish, Anoplopoma fimbria, ranked sixth in total 


groundfish biomass in the Gulf of Alaska in 2004 with an 


exploitable biomass of 185,000 t (NPFMC 2004). The 


commercial catch of sablefish in 2004 was 14,847 t. 


Sablefish have been found to feed opportunistically on fish, 


crustaceans, and worms (Grinols and Gill 1968). Because 


sablefish is an important commercial species and it 


probably feeds on other commercially important fish, it is 


included in this study on food habits and potential impacts 


on the other marine fishes in the Gulf of Alaska. 


General Diet 


Tables 11 and 12 list the total number of stomachs 


with food, the total empty stomachs, the mean percent 


frequency of occurrence, and the mean percent by weight of 


the prey found in sablefish stomachs collected in 1999, and 


2001. Walleye pollock was the predominate fish prey 


consumed by sablefish. Pollock comprised 16% and 17% by 


weight of the total sablefish stomach contents in 1999 and 


2001, respectively. Most of the unidentified gadid fish 


(about 8% by weight of the total stomach contents, Table 12) 


were probably walleye pollock. Pacific herring, capelin, 


eulachon, Pacific cod, Pacific ocean perch, shortspine 

 51 

thornyhead, Pacific sand lance, and some flatfish (Family 


Pleuronectidae) were also important commercial species 


consumed by sablefish. Sablefish also consumed fish such 


as lanternfish (Family Myctophidae), eelpout (Family 


Zoarcidae), sculpin (Family Cottidae), and poacher (Family 


Agonidae). It is worth noting that fishery offal (fish 


carcasses) made up to 27% and 9% by weight of the sablefish 


diet in 1999 and 2001, respectively. 


Cephalopods were the most important invertebrate prey 


of sablefish. They comprised 12% and 9% of the total 


stomach contents weight in 1999 and 2001, respectively. 


Euphausiids were found frequently in stomachs. They 


comprised about 15% by weight of the stomach contents in 


2001. Pandalid shrimps comprised 6% and 3% of the total 


stomach contents weight in 1999 and 2001, respectively. 


Tanner crabs were found in sablefish stomachs in 1999 when 


they comprised 4% of the total stomach contents weight. 


Sablefish also consumed small amounts of jellyfish, 


polychaetes, snails, mysids, amphipods, crangonids, 


pagurids, and some marine worms. 

 52 

Table 11.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Anoplopoma fimbria (sablefish) collected in the Gulf of Alaska in 1999.

 Prey items Percent frequency Percent weight

 Scyphozoa (jellyfish) 1.05 0.01 

Polychaeta (worm) 3.29 1.13 

Gymnosomata (pteropod) 1.75 0.25 

Cephalopoda (squid and octopus) 13.95 3.59 

Teuthida (squid) 2.63 3.69 

Octopoda (octopus) 2.11 4.87 

Calanoida (copepod) 3.95 0.71 

Mysidae (mysid) 3.51 0.45 

Isopoda (isopod) 2.63 1.13 

Gammaridea (amphipod) 15.13 3.87 

Hyperiidea (amphipod) 3.07 0.53 

Themisto sp. (amphipod) 1.75 0.00 

Thysanoessa sp. (euphausiid) 1.75 1.03 

Thysanoessa inspinata (euphausiid) 0.66 0.04 

Hippolytidae (shrimp) 2.63 0.07 

Pandalidae (shrimp) 0.88 0.31 

Pandalus borealis (shrimp) 5.26 5.26 

Pandalus jordani (shrimp) 0.44 0.15 

Crangonidae (shrimp) 7.02 5.73 

Paguridae (hermit crab) 2.63 2.96 

Majidae legs (for C. opilio, C. bairdi, etc) 6.14 2.63 

Chionoecetes bairdi (Tanner crab) 0.88 1.30 

Sipuncula (marine worm) 3.95 5.46 

Echiura (marine worm) 2.63 0.09 

Thaliacea (pelagic salp) 1.32 0.29 

Teleostei (fish) 17.54 7.07 

Non-gadoid fish remains 10.53 1.68 

Mallotus villosus (capelin) 0.44 0.83 

Myctophidae (lanternfish) 0.66 1.75 

Theragra chalcogramma (walleye pollock) 11.40 16.07 

Fishery offal 20.39 27.04 
 53 

Table 11.--Continued. 

Total non-empty stomachs = 59 

Total prey number = 387 

Total prey weight = 1381.582 g 

Total empty stomachs = 80 

Number of hauls = 19 

Full stomach summary statistics 

Average fork length = 55.19 cm 

Standard deviation of fork length = 3.17 cm 

Minimum fork length = 29 cm 

Maximum fork length = 67 cm 

Average fullness = 3.84 

Standard deviation of fullness = .92 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 58.54 cm 

Standard deviation of fork length = 11.74 cm 

Minimum fork length = 28 cm 

Maximum fork length = 83 cm 
 54 

Table 12.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Anoplopoma fimbria (sablefish) collected in the Gulf of Alaska in 2001. 

 Prey items Percent frequency Percent weight 

Phaeophycophyta (brown algae) 0.68 0.07 

Porifera (sponge) 0.20 0.02 

Cnidaria 2.14 0.58 

Scyphozoa (jellyfish) 2.18 1.95 

Anthozoa (anemome) 0.51 0.09 

Pennatulacea (sea pen) 0.17 0.00 

Polychaeta (worm) 4.30 1.70 

Aphroditidae (sea mouse) 0.51 0.59 

Mollusca 1.45 1.29 

Gastropoda (snail) 0.69 0.14 

Bivalvia (clam) 1.48 1.21 

Cephalopoda (squid and octopus) 2.48 1.88 

Teuthida (squid) 6.92 1.01 

Octopoda (octopus) 1.87 5.61 

Calanoida (copepod) 0.96 0.00 

Large calanoid (copepod) > 5mm 1.20 0.00 

Medium calanoid (copepod) 2-5mm 0.34 0.00 

Mysida (mysid) 2.41 0.04 

Mysidae (mysid) 1.42 0.01 

Cumacea (cumacean) 0.32 0.01 

Isopoda (isopod) 1.00 0.15 

Amphipoda (amphipod) 0.51 0.01 

Gammaridea (amphipod) 22.85 2.95 

Hyperiidea (amphipod) 3.42 0.02 

Euphausiacea (euphausiid) 1.03 0.02 

Euphausiidae (euphausiid) 36.25 13.46 

Thysanoessa sp. (euphausiid) 2.42 0.96 

Thysanoessa inermis (euphausiid) 1.55 0.30 

Thysanoessa spinifera (euphausiid) 0.82 0.34 

Natantia (shrimp) 4.55 0.43 

Caridea (shrimp) 9.97 0.61 

Pasiphaea pacifica (shrimp) 0.77 0.03 

Pandalidae (shrimp) 4.82 0.68 

Pandalus sp. (shrimp) 0.17 0.00 

Pandalus borealis (shrimp) 0.28 0.04 
 55

 Table 12.--Continued. 

Prey items Percent frequency Percent weight 

Pandalus jordani (shrimp) 0.51 2.50 

Pandalus platyceros (shrimp) 0.43 0.07 

Pandalopsis sp. (shrimp) 0.85 0.03 

Crangonidae (shrimp) 2.73 0.20 

Reptantia (crab) 1.16 0.06 

Paguridae (hermit crab) 3.40 0.54 

Decapoda brachyura (crab) 0.94 0.03 

Chionoecetes sp. (snow and Tanner crab) 0.37 0.10 

Echiura (marine worm) 0.83 0.15 

Priapulida (worm) 0.43 0.06 

Ophiurida (brittle star) 0.43 0.20 

Holothuroidea (sea cucumber) 0.38 0.21 

Chaetognatha (arrow worm) 1.03 0.00 

Urochordata (tunicate) 0.32 0.02 

Thaliacea (pelagic salp) 0.85 0.13 

Copelata (larvacea) 0.28 0.07 

Teleostei (fish) 15.16 4.79 

Non-gadoid fish remains 6.14 2.21 

Clupea pallasi (Pacific herring) 0.17 0.54 

Osmeridae (smelts) 2.85 1.33 

Mallotus villosus (capelin) 1.37 1.86 

Thaleichthys pacificus (eulachon) 2.01 2.46 

Gadidae (gadid fish) 12.33 8.17 

Gadus macrocephalus (Pacific cod) 1.92 1.60 

Theragra chalcogramma (walleye pollock) 12.93 16.96 

Zoarcidae (eelpout) 1.20 0.36 

Scorpaeniformes (rockfish and cottid) 0.20 0.06 

Scorpaenidae 0.17 0.02 

Sebastes alutus (Pacific ocean perch) 0.17 0.19 

Sebastolobus alascanus (shortspine thornyhead) 1.31 4.01 

Dasycottus setiger (spinyhead sculpin) 0.21 0.04 

Agonidae (poacher) 2.99 0.23 

Aspidophoroides bartoni (Aleutian alligatorfish) 0.18 0.27 

Asterotheca alascana (gray starsnout) 1.28 0.15 

Ammodytes hexapterus (Pacific sand lance) 7.13 4.85 

Pleuronectoidei (flatfish) 0.61 0.38 

Unidentified organic material 1.03 0.03 

Unidentified worm-like organism 0.85 0.05 

Fishery offal 6.81 8.86 

Unidentified tube 0.17 0.00 
 56 

Table 12.--Continued. 

Total non-empty stomachs = 284 

Total prey number = 3868 

Total prey weight = 14407.363 g 

Total empty stomachs = 64 

Number of hauls = 39 

Full stomach summary statistics 

Average fork length = 59.08 cm 

Standard deviation of fork length = 2.62 cm 

Minimum fork length = 23 cm 

Maximum fork length = 90 cm 

Average fullness = 3.74 

Standard deviation of fullness = .58 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 56.66 cm 

Standard deviation of fork length = 11.34 cm 

Minimum fork length = 26 cm 

Maximum fork length = 75 cm 
 57

 Comparing the 2 years of data, we noticed that the 


percentages of the main food items in sablefish stomachs 


were similar for 1999 and 2001. For example, pollock 


comprised 16% and 17% (by weight) of the diet in 1999 and 


2001, respectively. Pandalid shrimp comprised 6% and 3% in 


those 2 years. Cephalopods ranged from 12% to 9% of the 


stomach contents for sablefish in 1999 and 2001, 


respectively. However, sablefish consumed a larger variety 


of fish (e.g. eelpouts, cottids, poachers.) in 2001. 


These species made up 50% of the total stomach contents 


weight in 2001. Sablefish consumed a much higher 


percentage of fish offal in 1999 than in 2001 (27% vs. 9%). 


Comparing their diets to the diets of other groundfish 


species, we noticed that sablefish appeared to feed more 


frequently on fish offal than walleye pollock, Pacific cod, 


arrowtooth flounder, or Pacific halibut. This may indicate 


that sablefish are highly opportunistic feeders. 


Variation of Diet Based on Predator Size 


Figure 6 illustrates that larger (> 60 cm FL) 


sablefish consumed more fish (walleye pollock, 


miscellaneous fish, and fishery offal) than the smaller 


fish (< 60 cm FL). The smaller sablefish (< 60 cm FL) 


consumed more euphausiids, shrimp, and cephalopods. 


Sablefish larger than 70 cm FL consumed a high percentage 

 58 

(31%) of fishery offal in 2001. The miscellaneous prey 


consumed by the smallest size group (< 50 cm FL) of 


sablefish in 1999 was made up of mainly gammarid amphipods 


and sipuncula marine worms (46% by weight). 

 59 

 1999


Percent by weight (%

wt) Percent by weight (%

wt) 

n = 18 24


100


80


60


40


20


0


45 55 65 

Predator fork length (cm) 

17


Misc. prey 

Jellyfish 

Cephalopod 

Shrimp 

Crab 

Misc. fish 

Walleye pollock 

Fishery offal 

2001


n = 23 133 92


100


80


60


40


20


0


45 55 65 75 

Predator fork length (cm) 

36


Misc. prey 

Jellyfish 

Cephalopod 

Shrimp 

Crab 

Misc. fish 

Walleye pollock 

Fishery offal 

Figure 6.--Variations in the main food items of sablefish, by predator size, 

in the Gulf of Alaska in 1999 and 2001. 

n = stomachs with food.
 60 

Spiny Dogfish


 In the Gulf of Alaska, sharks (including spiny dogfish 


(Squalus acanthias), Pacific sleeper shark (Sominosus


pacificus), and salmon shark (Lamna ditropis)) have been 


managed as part of the “other species” category under the 


GOA FMP (Fishery Management Plan), along with other 


potentially economically important species such as, 


sculpins, squids, and octopi. The estimated biomass of all 


sharks was 34,214 t (Gaichas et al. 1999). 


Spiny dogfish is a demersal species. In the eastern 


North Pacific, they occur from Baja California to the 


Bering Sea (Hart 1973). Their diet varies greatly from 


euphausiids to many different kinds of fish such as Pacific 


herring, capelin, and sand lance. Because of this 


diversity in their diet, it is important to study the role 


of spiny dogfish in the Gulf of Alaska ecosystem. 


General Diet 


Euphausiids (7% by weight) and fishery offal (93%) 


were the only food items found in the spiny dogfish 


stomachs collected in 2001 in the Gulf of Alaska (Table 13). 


More stomach samples are needed in the future to provide an 


accurate description of the diet of spiny dogfish in the 


GOA. 

 61 

Table 13.--Prey items (expressed in mean percent frequency of occurrence, and percent total 

weight) of Squalus acanthias (spiny dogfish) collected in the Gulf of Alaska in 2001.

 Prey items Percent frequency Percent weight 

Euphausiacea (euphausiid) 100.00 6.68 

Fishery offal 100.00 93.32 

Total non-empty stomachs = 1 

Total prey number = 15 

Total prey weight = 35.73 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 72.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 72 cm 

Maximum fork length = 72 cm 

Average fullness = 6.00 

Standard deviation of fullness = 0 

Minimum fullness = 6 

Maximum fullness = 6 
 62 

Big Skate


 Big skate (Raja binoculata) are distributed in the 


Bering Sea, Aleutian Islands region, and as far south as 


Baja California (Mecklenburg et al. 2002). It is the most 


abundant skate species in the Gulf of Alaska with an 


estimated biomass of 53,324 t (NPFMC 2004). In 2003, a 


directed fishery for certain skate species developed in the 


Gulf of Alaska. Along with longnose skate (Raja rhina), 


they have been one of the two target species of the skate 


fishery since 2004. Therefore, it is important to study 


the trophic role of the big skate in the Gulf of Alaska 


ecosystem. 


General Diet 


Table 14 lists the total number of stomachs containing 


food, the empty stomachs, the mean percent frequency of 


occurrence of the prey, and the mean percent by weight of 


the prey found in big skate stomachs collected in 2001. 


Pacific sand lance was the most important prey. In terms of 


weight, Pacific sand lance comprised 49% of the total 


stomach contents in 2001. Tanner crabs were the most 


important invertebrate prey of big skate; they comprised 


46% of the total stomach contents weight in 2001. Big 


skate also consumed some shrimp (2%) and three spine 


stickleback (1%). 

 63 

Table 14.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Bathyraja binoculata (big skate) collected in the Gulf of Alaska in 2001. 

Prey items Percent frequency Percent weight 

Hippolytidae (shrimp) 

Argis lar (shrimp) 

Chionoecetes bairdi (Tanner crab) 

Gasterosteus aculeatus (threespine stickleback) 

Ammodytes sp. (sand lance) 

50.00 

50.00 

50.00 

50.00 

50.00 

2.29 

1.80 

45.92 

1.04 

48.96 

Total non-empty stomachs = 2 

Total prey number = 44 

Total prey weight = 324.32 g 

Total empty stomachs = 0 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 89.00 cm 

Standard deviation of fork length = 11.31 cm 

Minimum fork length = 81 cm 

Maximum fork length = 97 cm 

Average fullness = 4.50 

Standard deviation of fullness = 0.71 

Minimum fullness = 4 

Maximum fullness = 5 
 64 

Bering Skate (Sandpaper Skate) 


Bering skate (Bathyraja interrupta) are distributed 


from the Bering Sea, Aleutian Islands, to the waters off 


Southern California (Mecklenburg et al. 2002). This 


species along with Aleutian skate (B. aleutica), Alaska 


skate (B. parmifera), and other Bathyraja spp. are managed 


as “other skates” under the GOA FMP (Gulf of Alaska, 


Fishery Management Plan). The total biomass of these “other 


skates” was estimated 17,689 t in 2004 (NPFMC 2004). 


As the role of the skates has received more attention, 


it is important to study the diet of the skates to be able 


to understand the whole trophic relationships in the Gulf 


of Alaska ecosystem. 


Table 15 lists the total number of stomachs with food, 


the total empty stomachs, the mean percent frequency of 


occurrence, and the mean percent by weight of the prey 


found in Bering skate stomachs collected in 2001. Gadids 


(probably walleye pollock) were the primary fish prey 


consumed by Bering skate; they comprised 31% (by weight) of 


the total stomach contents in 2001. 


Lyre crab (Hyas lyratus) and hippolytid shrimp were 


the most important invertebrate prey of Bering skate; they 


each comprised 33% of the total stomach content weights in 

 65 

2001. Bering skate also consumed a low amount (2%) of 


isopods. 

 66 

Table 15.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Bathyraja interrupta (Bering skate) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Isopoda (isopod) 

Hippolytidae (shrimp) 

Hyas lyratus (lyre crab) 

Gadidae (gadid fish) 

33.33 

33.33 

33.33 

33.33 

2.10 

33.33 

33.33 

31.23 

Total non-empty stomachs = 3 

Total prey number = 14 

Total prey weight = 36.342 g 

Total empty stomachs = 0 

Number of hauls = 3 

Full stomach summary statistics 

Average fork length = 51.67 cm 

Standard deviation of fork length = 15.89 cm 

Minimum fork length = 42 cm 

Maximum fork length = 70 cm 

Average fullness = 4.33 

Standard deviation of fullness = 1.53 

Minimum fullness = 3 

Maximum fullness = 6 
 67 

Longnose Skate 


Longnose skate (Raja rhina) are distributed from the 


southeastern Bering Sea to Baja California (Mecklenburg 


et al. 2002). It ranked second in the total skate biomass 


in the Gulf of Alaska in 2004 with an estimated biomass of 


37,575 t (NPFMC 2004). The allowable biological catch (ABC)


was 2,818 t. It was one of the target species (along with 


big skate) of the skate fishery in the Gulf of Alaska. Due 


to concerns over increased fishing rates, it is important 


to understand the trophic role of longnose skate in the 


whole Gulf of Alaska ecosystem. 


Table 16 lists the total number of stomachs with food, 


the total number of empty stomachs, the mean percent 


frequency of occurrence, and the mean percent by weight of 


the prey found in longnose skate stomachs collected in 2001. 


Tanner crab was the most important prey consumed by 


longnose skate; they comprised 45% (by weight) of the total 


stomach contents in 2001. Pandalid shrimp were the other 


important prey of longnose skate; they also comprised 45% 


of the total stomach content weights in 2001. Longnose 


skate also consumed some dwarf wrymouth (9% by weight). 

 68 

Table 16.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Raja rhina (longnose skate) collected in the Gulf of Alaska in 2001. 

Prey items Percent frequency Percent weight 

Pandalus borealis (shrimp) 

Pandalus goniurus (shrimp) 

Argis lar (shrimp) 

Chionoecetes bairdi (Tanner crab) 

Cryptacanthodes aleutensis (dwarf wrymouth) 

33.33 

33.33 

33.33 

66.67 

33.33 

24.68 

20.03 

1.55 

44.53 

9.21 

Total non-empty stomachs = 3 

Total prey number = 35 

Total prey weight = 185.955 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 121.60 cm 

Standard deviation of fork length = 10.60 cm 

Minimum fork length = 112 cm 

Maximum fork length = 133 cm 

Average fullness = 4.00 

Standard deviation of fullness = 1.00 

Minimum fullness = 3 

Maximum fullness = 5 
 69 

Alaska Skate 


Alaska skate (Bathyraja parmifera) are distributed in 


the Gulf of Alaska, Bering Sea, Aleutian Islands, and 


northern Sea of Japan (Mecklenburg et al. 2002). This 


species along with Aleutian skate (B. aleutica), Bering 


skate (B. interrupta), and other Bathyraja spp. are managed 


as “other skates” under the GOA FMP (Gulf of Alaska, 


Fishery Management Plan). The total biomass of these 


“other skates” was estimated at 17,689 t in 2004 (NPFMC 


2004). It is important to study the diet of this species 


to better understand the predator-prey relationships in the 


Gulf of Alaska. 


Polychaetes were the only prey found in the single 


Alaska skate stomach collected in 2001 in the Gulf of 


Alaska (Table 17). More stomach samples are needed to 


describe the diet of this species in the GOA. 

 70 

Table 17.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Bathyraja parmifera (Alaska skate) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 100.00 100.00 

Total non-empty stomachs = 1 

Total prey number = 1 

Total prey weight = 1.274 g 

Total empty stomachs = 1 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 59.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 59 cm 

Maximum fork length = 59 cm 

Average fullness = 2.00 

Standard deviation of fullness = 0 

Minimum fullness = 2 

Maximum fullness = 2 

Empty stomach summary statistics 

Average fork length = 91.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 91 cm 

Maximum fork length = 91 cm 
 71 

Eulachon 


 Eulachon (Thaleichthys pacificus) are a small silvery 


fish commonly encountered in groundfish fisheries in Alaska.


Eulachon had an exploitable biomass of 49,061 t in the Gulf 


of Alaska in 2001. The reported catch of eulachon in the 


Gulf of Alaska in 2001 was 512 t (Nelson 2003). Although 


eulachon are not commercially important fish in the Gulf of 


Alaska area, they are common prey of some commercially 


important fish (Yang and Nelson 2000) and marine mammals 


(Womble 2003). Therefore, it is important to study the 


diet of eulachon in the Gulf of Alaska area. 


General Diet 


Table 18 lists the total number of stomachs containing 


food, the total number of empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of eulachon collected in the Gulf of Alaska in 


2001. Euphausiids and fish were the main food of eulachon 


(66% and 14% of the total stomach contents weight, 


respectively). Other food items included small 


invertebrates such as mysids, cumaceans, and hyperiid 


amphipods. 


Barraclough (1964) also found that, in British 


Columbia, euphausiids were the most important food of 

 72 

eulachon. Further studies should increase the sample size 


and the sampling locations in the Gulf of Alaska. 

 73 

Table 18.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Thaleichthys pacificus (eulachon) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight

 Mysida (mysid) 5.26 2.72 

Cumacea (cumacean) 5.26 2.10 

Hyperiidea (amphipod) 5.26 5.93 

Euphausiacea (euphausiid) 52.63 40.85 

Thysanoessa inermis (euphausiid) 5.26 25.77 

Copelata (larvacea) 5.26 1.67 

Teleostei (fish) 21.05 13.78 

Non-gadoid fish remains 5.26 2.60 

Unidentified organic material 5.26 4.57 

Total non-empty stomachs = 19 

Total prey number = 33 

Total prey weight = 1.618 g 

Total empty stomachs = 20 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 19.05 cm 

Standard deviation of fork length = 1.35 cm 

Minimum fork length = 16 cm 

Maximum fork length = 21 cm 

Average fullness = 3.42 

Standard deviation of fullness = 1.17 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 14.55 cm 

Standard deviation of fork length = 4.14 cm 

Minimum fork length = 7 cm 

Maximum fork length = 21 cm 
 74 

Shortfin Eelpout


Shortfin eelpout (Lycodes brevipes) are found 


throughout the Gulf of Alaska at depths ranging from 27 to 


973 m (Mecklenburg et al. 2002). Eelpouts are rarely 


encountered in observed fisheries, with the exception of a 


small amount of bycatch in flatfish and rockfish trawl 


fisheries. Estimated bycatch of eelpouts (not identified 


to species) from the fisheries in the Gulf of Alaska in 


1998 was 4.6 t (Gaichas et al. 1999). 


General Diet 


Table 19 lists the total number of stomachs containing 


food, the total number of empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of shortfin eelpout collected in the Gulf of 


Alaska in 2001. Clams and cumaceans were the most common 


prey items of shortfin eelpout (comprising 51% and 30% of 


mean percent total weight, respectively). Other prey items 


included shrimp, mysids, and euphausiids. 


Brodeur and Livingston (1988) found that brittle stars 


represented the vast majority (nearly 90%) of the prey 


biomass of shortfin eelpout in the Bering Sea. A previous 


study by Smith et al. (1978) found that polychaetes, 


euphausiids, and decapod crustaceans were the most common 


prey items in shortfin eelpout stomachs. Lang et al. (2003) 

 75 

also found that shortfin eelpout in the eastern Bering Sea 


consumed primarily benthic prey (polychaetes, amphipods, 


and brittle stars. They comprised 28%, 24%, and 23% of the 


total stomach contents weight, respectively). 

 76 

Table 19.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lycodes brevipes (shortfin eelpout) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Bivalvia (clam) 

Mysida (mysid) 

Cumacea (cumacean) 

Euphausiacea (euphausiid) 

Caridea (shrimp) 

36.90 

10.71 

35.71 

3.57 

16.67 

50.56 

7.20 

30.24 

1.44 

10.56 

Total non-empty stomachs = 17 

Total prey number = 38 

Total prey weight = 1.108 g 

Total empty stomachs = 1 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 22.30 cm 

Standard deviation of fork length = 1.19 cm 

Minimum fork length = 19 cm 

Maximum fork length = 29 cm 

Average fullness = 2.50 

Standard deviation of fullness = .07 

Minimum fullness = 2 

Maximum fullness = 4 

Empty stomach summary statistics 

Average fork length = 27.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 27 cm 

Maximum fork length = 27 cm 
 77 

Black Eelpout 


Black eelpout (Lycodes diapterus) are widespread in 


the Gulf of Alaska, usually occurring at depths from 100 to 


850 m (Mecklenburg et al. 2002). Estimated bycatch of 


eelpouts (not identified by species) from the fisheries in 


the Gulf of Alaska in 1998 was 4.6 t (Gaichas et al. 1999). 


General Diet 


Table 20 lists the total number of stomachs containing 


food, the total number of empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of black eelpout collected in the Gulf of Alaska 


in 2001. Euphausiids were the most common prey items of 


black eelpout. They comprised 90% of the total stomach 


contents weight. Black eelpout also consumed crangonid 


shrimp; they comprised 9% of the total stomach contents 


weight. 


It is difficult to draw any conclusions about the diet 


of this species since there was only one black eelpout 


stomach analyzed. Larger sample size is needed for future 


study of the diet of black eelpout. 

 78 

Table 20.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lycodes diapterus (black eelpout) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Thysanoessa sp. (euphausiid) 

Thysanoessa inermis (euphausiid) 

Crangon dalli (shrimp) 

100.00 

100.00 

100.00 

77.07 

13.53 

9.40 

Total non-empty stomachs = 1 

Total prey number = 32 

Total prey weight = 2.66 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 24.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 24 cm 

Maximum fork length = 24 cm 

Average fullness = 6.00 

Standard deviation of fullness = 0 

Minimum fullness = 6 

Maximum fullness = 6 
 79 

Wattled Eelpout 


Wattled eelpout (Lycodes palearis) are found 


throughout the Gulf of Alaska and are typically encountered 


at depths of less than 150 m. They reach a maximum size of 


approximately 50 cm (Mecklenburg et al. 2002). Eelpouts 


are not targeted as commercial species; however, there has 


been a small amount of bycatch in flatfish and rockfish 


trawl fisheries. Estimated catch of eelpouts (not 


identified to species) from the fisheries in the Gulf of 


Alaska in 1998 was 4.6 t (Gaichas et al. 1999). 


General Diet 


Table 21 lists the total number of stomachs containing 


food, the total empty stomachs, the mean percent frequency 


of occurrence and mean percent by weight of the prey items 


of wattled eelpout collected in the Gulf of Alaska in 2001. 


Shortfin eelpout (Lycodes brevipes) was the most important 


prey of wattled eelpout, in terms of the percentage of the 


total stomach contents weight. It comprised 92% of the 


total prey weight. Crangonid shrimp (Argis spp.) was the 


other prey of wattled eelpout. It comprised 8% of the 


total stomach contents weight. 


Slipp and DeLacy (1952) found that clams and shrimp 


were important prey items of wattled eelpout in Puget Sound. 


Crustaceans and polychaetes comprised the majority of the 

 80 

diet of wattled eelpout in the Bering Sea (Brodeur and 


Livingston 1988). Tanner crabs (Chionoecetes bairdi) and 


snow crabs (C. opilio) were also important in the diet of 


wattled eelpouts in the Bering Sea, but this was not seen 


in the current study. Lang et al. (2003) found similar 


results to Brodeur and Livingston (1988). The differences 


between this study and earlier studies may be attributed to 


the small sample size (n = 2) of this study. Larger sample 


sizes with a wider geographic area would be necessary for 


future diet studies of the wattled eelpout in the Gulf of 


Alaska. 

 81 

Table 21.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lycodes palearis (wattled eelpout) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Argis sp. (shrimp) 50.00 7.94 

Lycodes brevipes (shortfin eelpout) 50.00 92.06 

Total non-empty stomachs = 2 

Total prey number = 2 

Total prey weight = 4.661 g 

Total empty stomachs = 1 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 38.50 cm 

Standard deviation of fork length = 2.12 cm 

Minimum fork length = 37 cm 

Maximum fork length = 40 cm 

Average fullness = 4.00 

Standard deviation of fullness = 0 

Minimum fullness = 4 

Maximum fullness = 4 

Empty stomach summary statistics 

Average fork length = 42.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 42 cm 

Maximum fork length = 42 cm 
 82 

Giant Grenadier 


Giant grenadiers (Coryphaenoides pectoralis) are the 


largest of all grenadier species and their length reach 


150 cm total length (Mecklenburg et al. 2002). They are 


most often encountered at depths greater than 200 m 


(Iwamoto and Stein 1974) and are commonly observed as 


bycatch in various fisheries (including sablefish, flatfish, 


and rockfish) in the Gulf of Alaska. Giant grenadier had a 


biomass of 386,312 t in the Gulf of Alaska in 1999. 


Estimated bycatch of grenadiers in the Gulf of Alaska in 


1998 was 14.5 t (Gaichas et al. 1999). 


General Diet 


Table 22 lists the total number of stomachs containing 


food, the total empty stomachs, the mean percent frequency 


of occurrence and mean percent by weight of the prey items 


of giant grenadier collected in the Gulf of Alaska in 2001. 


Squid and pasiphaeid shrimp were the most common prey items; 


they comprised 32% and 22% of mean percent total weight, 


respectively). Other invertebrate prey items included 


octopi, other shrimp, mysids, and euphausiids. Prey fish 


consumed included walleye pollock, deepsea smelts, and 


scorpaenid. 

 83 

In this study, squid and shrimp were the most 


important food of giant grenadier. Earlier studies of 


grenadier in different areas showed some similarities. 


Brodeur and Livingston (1988) examined grenadier stomachs 


from the eastern Bering Sea and found that eelpouts and 


unidentified teleosts were the main food of giant grenadier.


Drazen et al. (2001) reported that giant grenadier on the 


West Coast of the United States ate squid, myctophids, 


bathylagids, and Pacific viperfish. Yang (2003) found that 


myctophids and squid were the most important prey items for 


giant grenadier in the Aleutian Islands region; they 


comprised 47% and 45% of the total prey weight, 


respectively. 

 84 

Table 22.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Coryphaenoides pectoralis (giant grenadier) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight

 Cephalopoda (squid and octopus) 4.55 0.16 

Teuthida (squid) 42.42 32.09 

Octopoda (octopus) 18.18 6.04 

Mysida (mysid) 16.67 4.13 

Euphausia pacifica (euphausiid) 8.33 1.90 

Pasiphaea pacifica (shrimp) 9.09 22.13 

Hippolytidae (shrimp) 4.55 2.41 

Pandalidae (shrimp) 4.55 4.21 

Argis dentata (shrimp) 16.67 8.97 

Teleostei (fish) 4.55 0.80 

Bathylagidae (deepsea smelts) 4.55 0.86 

Theragra chalcogramma (walleye pollock) 8.33 4.03 

Scorpaenidae 4.55 12.29 

Total non-empty stomachs = 17 

Total prey number = 42 

Total prey weight = 18.305 g 

Total empty stomachs = 8 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 31.15 cm 

Standard deviation of fork length = .70 cm 

Minimum fork length = 27 cm 

Maximum fork length = 35 cm 

Average fullness = 2.50 

Standard deviation of fullness = .06 

Minimum fullness = 2 

Maximum fullness = 4 

Empty stomach summary statistics 

Average fork length = 30.88 cm 

Standard deviation of fork length = 3.36 cm 

Minimum fork length = 26 cm 

Maximum fork length = 35 cm 
 85 

Rougheye Rockfish 


Rougheye rockfish (Sebastes aleutianus) is an 


important commercial species in the Gulf of Alaska. It had 


an exploitable biomass of 40,281 t in the Gulf of Alaska in 


2004 (Clausen et al. 2004). The reported catch of rougheye 


rockfish has been combined with shortraker rockfish 


(Sebastes borealis) since 1994. Total catch of these two 


species in the Gulf of Alaska in 2004 was 973 t (Clausen 


et al. 2004). 


General Diet 


Table 23 lists the total number of stomachs containing 


food, the total number of empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of rougheye rockfish collected in the Gulf of 


Alaska in 2001. Pandalid shrimp and euphausiids were the 


most common prey items; they comprised 26% and 22% of mean 


percent total weight, respectively. Tanner crab 


(Chionoecetes bairdi), comprising 13% of mean percent total 


prey weight, was also a significant portion of the diet. 


Other prey items included octopi, calanoid copepods, and 


other shrimp species. 


In an earlier study Yang and Nelson (2000) found that 


shrimp was the main food of rougheye rockfish in the Gulf 


of Alaska. The most noticeable difference is that 

 86 

consumption of fish prey was much lower in 2001 (1%) by 


percent weight than in 1990 (18%) and 1993 (13%). 


Additionally, rougheye rockfish consumed a greater amount 


(by weight) of Tanner crab in 2001 (13%) than those in 1990 


(5%) and 1993 (1%). 

 87 

Table 23.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes aleutianus (rougheye rockfish) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Octopoda (octopus) 3.33 7.66 

Crustacea 5.56 0.05 

Large calanoid (copepod) > 5mm 16.67 6.23 

Medium calanoid (copepod) 2-5mm 5.56 0.18 

Mysida (mysid) 5.56 0.09 

Cumacea (cumacean) 7.41 0.12 

Gammaridea (amphipod) 12.22 2.85 

Hyperiidea (amphipod) 5.56 0.18 

Euphausiacea (euphausiid) 3.33 0.27 

Euphausiidae (euphausiid) 11.11 4.03 

Thysanoessa inermis (euphausiid) 11.11 17.95 

Caridea (shrimp) 8.89 0.80 

Hippolytidae (shrimp) 3.70 0.96 

Pandalidae (shrimp) 19.63 19.32 

Pandalus borealis (shrimp) 3.70 1.91 

Pandalus goniurus (shrimp) 3.70 4.67 

Crangonidae (shrimp) 5.56 0.18 

Crangon sp. (shrimp) 3.70 0.83 

Argis sp. (shrimp) 3.70 2.94 

Paguridae (hermit crab) 3.70 0.93 

Chionoecetes sp. (snow and Tanner crab) 3.70 4.35 

Chionoecetes bairdi (Tanner crab) 3.70 8.54 

Chaetognatha (arrow worm) 16.67 3.24 

Teleostei (fish) 10.37 0.81 

Unidentified organic material 10.37 10.88 

Total non-empty stomachs = 25 

Total prey number = 97 

Total prey weight = 45.015 g 

Total empty stomachs = 11 

Number of hauls = 3 

Full stomach summary statistics 

Average fork length = 34.10 cm 

Standard deviation of fork length = 2.88 cm 

Minimum fork length = 16 cm 

Maximum fork length = 78 cm 

Average fullness = 2.67 

Standard deviation of fullness = .54 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 39.91 cm 

Standard deviation of fork length = 9.33 cm 

Minimum fork length = 18 cm 

Maximum fork length = 47 cm 
 88 

Pacific Ocean Perch 


Pacific ocean perch (Sebastes alutus) is an important 


commercial species in the Gulf of Alaska. It had an 


exploitable biomass of 286,367 t in the Gulf of Alaska in 


2004 (Hanselman et al. 2004). The reported catch of 


Pacific ocean perch in the Gulf of Alaska in 2004 was 


11,518 t. Earlier study shows that Pacific ocean perch is 


mainly a zooplankton feeder. Their food includes calanoid 


copepod, euphausiids, and miscellaneous prey (Yang 2003). 


General Diet 


Table 24 lists the total number of stomachs containing 


food, the total number of empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of Pacific ocean perch collected in the Gulf of 


Alaska in 2001. Euphausiids, larvaceans, and copepods were 


the most common prey items; they comprised 41%, 24%, and 


21% of the total stomach contents weight, respectively. 


Other prey items included octopi, hyperiid amphipods, and 


shrimp. 


Yang (2003) found that calanoid copepods and 


euphausiids were the most important prey of Pacific ocean 


perch in the Aleutian Islands region in 1994 and 1997. He 


also noticed that a large amount of myctophids were 


consumed by Pacific ocean perch in those 2 years (11% and 

 89 

12% by weight, respectively). The current study also shows 


the importance of zooplankton in the diet of Pacific ocean 


perch. However, fish were not a common prey item in this 


study. 

 90 

Table 24.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes alutus (Pacific ocean perch) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Thecosomata (pteropod) 3.03 0.45 

Teuthida (squid) 2.22 0.15 

Octopoda (octopus) 3.03 2.62 

Copepoda 5.13 2.76 

Calanoida (copepod) 11.19 3.24 

Large calanoid (copepod) > 5mm 35.56 10.12 

Medium calanoid (copepod) 2-5mm 11.45 0.07 

Small calanoid (copepod) < 2mm 23.08 4.39 

Mysida (mysid) 4.44 0.01 

Gammaridea (amphipod) 2.22 0.01 

Hyperiidea (amphipod) 24.65 5.08 

Euphausiacea (euphausiid) 6.06 18.79 

Euphausiidae (euphausiid) 13.33 11.81 

Thysanoessa sp. (euphausiid) 17.78 3.95 

Thysanoessa inermis (euphausiid) 24.44 6.23 

Thysanoessa longipes (euphausiid) 2.22 0.01 

Natantia (shrimp) 4.44 0.00 

Caridea (shrimp) 14.95 2.72 

Hippolytidae (shrimp) 2.22 0.01 

Pandalidae (shrimp) 6.06 2.66 

Chaetognatha (arrow worm) 17.78 0.84 

Copelata (larvacea) 20.17 23.69 

Teleostei (fish) 3.03 0.32 

Protomyctophum thompsoni (bigeye lanternfish) 2.22 0.07 

Total non-empty stomachs = 39 

Total prey number = 5353 

Total prey weight = 139.182 g 

Total empty stomachs = 11 

Number of hauls = 3 

Full stomach summary statistics 

Average fork length = 29.70 cm 

Standard deviation of fork length = 1.73 cm 

Minimum fork length = 10 cm 

Maximum fork length = 40 cm 

Average fullness = 3.33 

Standard deviation of fullness = .24 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 25.55 cm 

Standard deviation of fork length = 10.74 cm 

Minimum fork length = 9 cm 

Maximum fork length = 39 cm 
 91 

Redbanded Rockfish 


Redbanded rockfish (Sebastes babcocki) are distributed 


from the Bering Sea, Aleutian Islands, south to Southern 


California (Mecklenburg et al. 2002). It had an 


exploitable biomass of 6,897 t in the Gulf of Alaska in 


2004 (Clausen et al. 2004). The catch of redbanded 


rockfish in the Gulf of Alaska in 2002 was 35 t (Heifetz 


et al. 2002). 


General Diet 


Table 25 shows the total number of stomachs containing 


food, the total empty stomachs, the mean percent frequency 


of occurrence and mean percent by weight of the prey items 


of redbanded rockfish collected in the Gulf of Alaska in 


2001. Copepods (mainly Calanus spp.) and isopods were the 


most common prey items of redbanded rockfish. They 


comprised 50% and 49% of the total stomach contents weight, 


respectively. Euphausiids were also food of redbanded 


rockfish; however, they comprised only 1% of the total 


stomach contents weight. 


The current study suggests that redbanded rockfish eat 


both benthic (e.g., isopods) and pelagic (e.g., copepods 


and euphausiids) prey. It should be noted, however, that 


these results are from a sample of only three stomachs. 

 92 

Larger sample size is needed for future study of the diet 


of redbanded rockfish in the Gulf of Alaska. 

 93 

Table 25.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes babcocki ( redbanded rockfish) collected in the Gulf of 

Alaska in 2001. 

Prey items Percent frequency Percent weight 

Calanus spp. 

Isopoda (isopod) 

Thysanoessa spp. (euphausiid) 

50.00 

100.00 

50.00 

50.00 

49.35 

0.65 

Total non-empty stomachs = 3 

Total prey number = 105 

Total prey weight = 4.434 g 

Total empty stomachs = 1 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 21.00 cm 

Standard deviation of fork length = 1.00 cm 

Minimum fork length = 20 cm 

Maximum fork length = 22 cm 

Average fullness = 3.67 

Standard deviation of fullness = 1.15 

Minimum fullness = 3 

Maximum fullness = 5 

Empty stomach summary statistics 

Average fork length = 23.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 23 cm 

Maximum fork length = 23 cm 
 94 

Shortraker Rockfish 


Shortraker rockfish (Sebastes borealis) are 


distributed from the Bering Sea, Aleutian Islands region, 


to Southern California (Mecklenburg et al. 2002). It had an 


exploitable biomass of 32,723 t in the Gulf of Alaska in 


2004. The reported catch of shortraker rockfish has been 


combined with rougheye rockfish (Sebastes aleutianus) since 


1994 (Clausen et al. 2004). Total catch of these two 


species in the Gulf of Alaska in 2004 was 973 t. An 


earlier study showed that shortraker rockfish fed on squid, 


shrimp, mysids, bathylagids, and myctophids (Yang and 


Nelson 2000). 


General Diet 


Tables 26 and 27 show the total number of stomachs 


containing food, the total empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of shortraker rockfish collected in the Gulf of 


Alaska in 1999 and 2001, respectively. In 1999, only one 


shortraker rockfish was examined; the prey consumed by the 


fish was made up non-gadoid fish remains. However, in 2001 


a wide variety of prey was eaten. Shrimp was the most 


important food of shortraker rockfish. It accounted for 


44% of the total stomach contents weight. Myctophids were 


the most common fish prey item. They comprised 30% of the 

 95 

total prey weight. Squid (comprising 16% by weight) were 


also important food of shortraker rockfish. 


Yang and Nelson (2000) found varying results between 


years in their examination of shortraker rockfish diet in 


the Gulf of Alaska. In 1990, only squid and myctophids 


were found in the stomachs. In 1993, more prey items were 


found in the stomachs of shortraker rockfish. They 


included cephalopod, mysids, pandalid shrimp, and 


bathylagids. In contrast, the diet of shortraker rockfish 


in 2001 was much more diversified. It included 18 


different prey items with shrimp and myctophids as the most 


important prey. 

 96 

Table 26.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes borealis (shortraker rockfish) collected in the Gulf of Alaska

 in 1999. 

Prey items Percent frequency Percent weight 

Non-gadoid fish remains 100.00 100.00 

Total non-empty stomachs = 1 

Total prey number = 1 

Total prey weight = 3.46 g 

Total empty stomachs = 40 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 42.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 42 cm 

Maximum fork length = 42 cm 

Average fullness = 4.00 

Standard deviation of fullness = 0 

Minimum fullness = 4 

Maximum fullness = 4 

Empty stomach summary statistics 

Average fork length = 50.25 cm 

Standard deviation of fork length = 8.91 cm 

Minimum fork length = 37 cm 

Maximum fork length = 85 cm 
 97 

Table 27.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes borealis (shortraker rockfish) collected in the Gulf of Alaska

 in 2001. 

 Prey items Percent frequency Percent weight 

Cephalopoda (squid and octopus) 8.33 0.84 

Teuthida (squid) 19.70 15.76 

Gnathophausia gigas (mysid) 3.33 0.23 

Mysida (mysid) 29.39 1.41 

Gammaridea (amphipod) 4.85 0.09 

Hyperiidea (amphipod) 3.03 0.03 

Euphausiidae (euphausiid) 1.52 0.02 

Natantia (shrimp) 1.52 0.03 

Caridea (shrimp) 25.00 17.50 

Oplophoridae (shrimp) 1.52 1.96 

Pasiphaea sp. (glass shrimp) 28.48 23.75 

Hippolytidae (shrimp) 3.03 0.37 

Pandalidae (shrimp) 8.33 0.80 

Bathylagidae (deepsea smelts) 1.52 0.08 

Myctophidae (lanternfish) 19.70 13.93 

Stenobranchius nannochir (garnet myctophid) 16.67 16.27 

Agonidae (poacher) 1.52 0.07 

Unidentified organic material 8.33 6.86 

Total non-empty stomachs = 22 

Total prey number = 44 

Total prey weight = 108.486 g 

Total empty stomachs = 24 

Number of hauls = 6 

Full stomach summary statistics 

Average fork length = 54.50 cm 

Standard deviation of fork length = 1.61 cm 

Minimum fork length = 43 cm 

Maximum fork length = 61 cm 

Average fullness = 2.83 

Standard deviation of fullness = .40 

Minimum fullness = 2 

Maximum fullness = 5 

Empty stomach summary statistics 

Average fork length = 51.75 cm 

Standard deviation of fork length = 7.70 cm 

Minimum fork length = 39 cm 

Maximum fork length = 72 cm 
 98 

Dusky Rockfish


The dusky rockfish (Sebastes ciliatus) has been 


considered a single variable species with light and dark 


forms. Orr and Blackburn (2004) resurrected Sebastes 


variabilis (Pallas) and used dusky rockfish as its common 


name. They redescribed Sebastes ciliatus (Tilesius) and 


called it dark rockfish. In this study, dusky rockfish 


(Sebastes variabilis) were collected and studied. It had 


an exploitable biomass of 70,862 t in the Gulf of Alaska in 


2003 (Lunsford et al. 2004). The reported catch of dusky 


rockfish in the Gulf of Alaska in 2004 was 2,651 t. 


General Diet 


Table 28 lists the total number of stomachs containing 


food, the total number of empty stomachs, the mean percent 


frequency of occurrence and mean percent by weight of the 


prey items of dusky rockfish collected in the Gulf of 


Alaska in 2001. Pacific sand lance and euphausiids were 


the most common prey items of dusky rockfish. They 


comprised 82% and 17% of the total stomach contents weight, 


respectively. A small amount of copepods were also food of 


dusky rockfish. 


Yang’s (1993) earlier diet study of Sebastes ciliatus


found that euphausiids were the most important food (69% by 


weight) of S. ciliatus. Other food items included: 

 99 

larvaceans, cephalopods, calanoid copepods, arrow worms, 


gammarid amphipods, and shrimp. 

 100 

Table 28.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 Total weight) of Sebastes variabilis (dusky rockfish) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight

 Large calanoid (copepod) > 5mm 

 Euphausiidae (euphausiid) 

Thysanoessa inermis (euphausiid) 

Ammodytes hexapterus (Pacific sand lance) 

100.00 

100.00 

100.00 

100.00 

1.15

3.45 

13.79 

81.61 

Total non-empty stomachs = 1 

Total prey number = 4 

Total prey weight = 0.87 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 39.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 39 cm 

Maximum fork length = 39 cm 

Average fullness = 3.00 

Standard deviation of fullness = 0 

Minimum fullness = 3 

Maximum fullness = 3 
 101 

Sharpchin Rockfish 


Sharpchin rockfish (Sebastes zacentrus) had an 


exploitable biomass of 20,698 t in the Gulf of Alaska in 


2004 (Clausen et al. 2004). Sharpchin rockfish is one of 


the species classified in the “shortraker/rougheye rockfish 


and other slope rockfish” management group in the Gulf of 


Alaska. Since 1992, this species has ranked second in 


abundance among “other slope rockfish” species found in 


commercial catches in the Gulf of Alaska, behind only 


harlequin rockfish (Sebastes variegatus) (Clausen et al. 


2003). Sharpchin rockfish and other species comprising the 


“other slope rockfish” group are caught predominately in 


the trawl fishery and not the longline fishery. The 


avoidance of the longline bait suggests that this species 


has a diet consisting primarily of plankton. It is 


important to study the food habits of sharpchin rockfish 


because it is a commercially valuable species in the Gulf 


of Alaska. 


General Diet 


Tables 29 and 30 show the total number of full 


stomachs, the total number of empty stomachs, the minimum 


and maximum fork length, average fork length, the minimum 


and maximum stomach fullness, the average fullness, the 


mean percent frequency of occurrence, and the mean percent 

 102 

total weight of the prey items of sharpchin rockfish in the 


Gulf of Alaska in 1999 and 2001, respectively. In 1999, 


calanoid copepods were the most abundant prey item for 


sharpchin rockfish, comprising 76% (by weight) of the 


stomach contents. Euphausiids were the second most 


abundant prey item in 1999, comprising 18% (by weight) of 


the total stomach contents. In 2001, the shrimp Pandalus 


borealis was the most abundant prey item, comprising 50% 


(by weight) of the stomach contents. Euphausiids were also 


a major component of the sharpchin rockfish’s diet in 2001, 


accounting for 45% by weight of the stomach contents. 


Pteropods, amphipods, ostracods, and hermit crabs were also 


consumed by sharpchin rockfish. 


The percent frequency of occurrence and percent by 


weight of prey items of the sharpchin rockfish varied from 


1999 to 2001. The shrimp Pandalus borealis was the most 


abundant prey item by percent weight found in stomachs in 


2001, but it was not found in any sharpchin rockfish 


stomach samples in 1999. Calanoid copepods were found in 


every sharpchin rockfish stomach analyzed in 1999 and were 


also found in the highest percent by weight, but made up 


less than 1% by weight of the prey items found in sharpchin 


rockfish in 2001. The variation between the food habits of 

 103 

sharpchin rockfish between 1999 and 2001 could be 


attributed to the small sample sizes of stomachs analyzed. 

 104 

Table 29.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes zacentrus (sharpchin rockfish) collected in the Gulf of

 Alaska in 1999. 

Prey items Percent frequency Percent weight 

Pteropoda 

Ostracoda 

50.00 

16.67 

2.52 

0.38 

Calanoida (copepod) 

Themisto sp. (amphipod) 

Euphausiacea (euphausiid) 

Paguridae (hermit crab) 

100.00 

66.67 

33.33 

16.67 

76.40 

2.35 

17.87 

.47 

Total non-empty stomachs = 6 

Total prey number = 26 

Total prey weight = 2.339 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 23.67 cm 

Standard deviation of fork length = 3.08 cm 

Minimum fork length = 19 cm 

Maximum fork length = 27 cm 

Average fullness = 4.33 

Standard deviation of fullness = 1.21 

Minimum fullness = 3 

Maximum fullness = 6 
 105 

Table 30.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastes zacentrus (sharpchin rockfish) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Pteropoda 

Calanoida (copepod) 

Euphausiidae (euphausiid) 

Caridea (shrimp) 

Pandalus borealis (shrimp) 

25.00 

16.67 

50.00 

8.33 

50.00 

0.34 

0.20 

45.41 

4.05 

50.00 

Total non-empty stomachs = 7 

Total prey number = 18 

Total prey weight = 8.53 g 

Total empty stomachs = 11 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 29.00 cm 

Standard deviation of fork length = 2.16 cm 

Minimum fork length = 25 cm 

Maximum fork length = 32 cm 

Average fullness = 4.43 

Standard deviation of fullness = 1.27 

Minimum fullness = 3 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 25.27 cm 

Standard deviation of fork length = 3.74 cm 

Minimum fork length = 19 cm 

Maximum fork length = 33 cm 
 106 

Shortspine Thornyhead 


Shortspine thornyhead (Sebastolobus alascanus) had an 


estimated exploitable biomass of 86,200 t in the Gulf of 


Alaska in 2004 (Gaichas and Ianelli 2004). Shortspine 


thornyheads are a commercially important rockfish in both 


the trawl and longline fisheries in the Gulf of Alaska, 


with most of the domestic catch exported to Japan (Gaichas 


and Ianelli 2002). The total catch for shortspine 


thornyhead in 2004 was 805 t. Previous stomach analyses 


show that shortspine thornyhead diet consists of a variety 


of crustaceans, mollusks, and fish (Yang and Nelson 2000). 


The commercial value of shortspine thornyhead, and its role 


as a potential predator on commercially valuable crab and 


fish, makes it important to understand its food habits in 


the Gulf of Alaska. 


General Diet 


Table 31 shows the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of shortspine thornyhead in 2001 in the 


Gulf of Alaska. Fish (shortspine thornyhead, zoarcids, 


gadids, and myctophids), comprising 35% by weight, were the 

 107 

most abundant prey found in the stomachs of shortspine 


thornyhead. The decorator crab Chorilia longipes


represented 30% by weight of the diet. Euphausiids (16% by 


weight) and shrimp (9% by weight) were also integral 


components of the shortspine thornyhead stomach contents. 


Polychaetes, larvaceans, octopus, amphipods, mysids, 


chaetognaths, isopods, and copepods, were also consumed by 


shortspine thornyheads. 


Shrimp (mostly pandalids) were the most abundant prey 


by percent weight found in shortspine thornyhead stomachs 


in 1990 and 1993 (Yang and Nelson 2000). However, in 2001, 


fish and decorator crabs were the most abundant prey, while 


shrimp comprised less than 10% of their diet by percent 


weight. In the Aleutian Islands, Yang (2003) found that 


fish was the shortspine thornyhead’s most important prey 


(44% by weight). Of the fish species consumed by 


shortspine thornyhead in 2001, shortspine thornyhead was 


most abundant by percent weight. However, this does not 


suggest that cannibalism is common among shortspine 


thornyhead since no instances of cannibalism were recorded 


in 1990 or 1993 in the Gulf of Alaska, and no cannibalism 


was observed in the 1994 Aleutian Islands survey. 


Euphausiids were an important prey for shortspine 


thornyheads in 2001, but were only a small part of the diet 

 108 

(3% by weight) in 1993, and were not found at all in 


stomachs in 1990. The variations in the diets between the 


different years discussed can be attributed to the smaller 


sample size in the 2001 survey. A total of 81 and 147 full 


stomachs were analyzed in 1990 and 1993, respectively, 


compared to only 27 full stomachs analyzed in 2001. Also, 


stomachs were only analyzed from three hauls in 2001, 


compared to 11 and 24 hauls in 1990 and 1993, respectively. 

 109 

Table 31.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Sebastolobus alascanus (shortspine thornyhead) collected in the Gulf

 of Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 7.14 0.60 

Aphroditidae (sea mouse) 2.38 0.71 

Onuphidae (polychaete) 2.38 0.88 

Octopoda (octopus) 2.38 1.07 

Large calanoid (copepod) > 5mm 4.76 0.02 

Medium calanoid (copepod) 2-5mm 2.38 0.00 

Mysida (mysid) 26.35 0.51 

Pseudomma sp. (mysid) 4.76 0.06 

Isopoda (isopod) 4.76 0.19 

Gammaridea (amphipod) 25.40 0.66 

Caprellidae (amphipod) 2.38 0.02 

Euphausiacea (euphausiid) 3.33 0.11 

Euphausiidae (euphausiid) 11.90 0.25 

Thysanoessa sp. (euphausiid) 30.95 12.58 

Thysanoessa inermis (euphausiid) 4.76 0.88 

Natantia (shrimp) 2.38 0.01 

Caridea (shrimp) 7.14 3.92 

Eualus sp. (shrimp) 2.38 0.30 

Pandalidae (shrimp) 11.43 0.55 

Pandalus spp. (shrimp) 2.38 2.12 

Crangonidae (shrimp) 4.76 0.56 

Crangon sp. (shrimp) 7.14 1.50 

Argis ovifer (shrimp) 2.38 0.47 

Paguridae (hermit crab) 3.33 2.01 

Majidae (spider crab) 3.33 0.30 

Chorilia longipes (decorator crab) 13.49 30.41 

Chaetognatha (arrow worm) 4.76 0.52 

Copelata (larvacea) 3.33 1.20 

Teleostei (fish) 3.33 0.02 

Non-gadoid fish remains 6.67 0.93 

Myctophidae (lanternfish) 3.33 0.79 

Gadidae (gadid fish) 11.11 0.37 

Zoarcidae (eelpout) 3.33 8.49 

Sebastolobus alascanus (shortspine thornyhead) 3.33 15.73 

Unidentified organic material 3.33 0.25 

Unidentified tube 2.38 0.02 
 110 

Table 31.--Continued. 

Total non-empty stomachs = 27 

Total prey number = 198 

Total prey weight = 40.267 g 

Total empty stomachs = 14 

Number of hauls = 3 

Full stomach summary statistics 

Average fork length = 25.67 cm 

Standard deviation of fork length = 1.69 cm 

Minimum fork length = 15 cm 

Maximum fork length = 39 cm 

Average fullness = 3.33 

Standard deviation of fullness = .35 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 24.93 cm 

Standard deviation of fork length = 7.38 cm 

Minimum fork length = 16 cm 

Maximum fork length = 39 cm 
 111 

Atka Mackerel 


Atka mackerel (Pleurogrammus monopterygius) is an 


important food source for marine birds, predatory fish, and 


marine mammals, including the endangered Steller sea lion 


(Yang 1999). There are no reliable estimates of the 


current biomass of Atka mackerel due to high variability in 


survey estimates. In 1996 the estimated biomass of Atka 


mackerel in the Gulf of Alaska was 345,990 t (Martin 1997). 


However, over 98% of the catch came from one haul within a 


large stratum (Lowe and Lauth 2003). This led to a large 


stratum biomass with a large confidence interval. Several 


factors make it difficult to determine biomass of Atka 


mackerel. First, they lack a swim bladder, making it 


difficult to conduct hydroacoustic surveys for them. 


Second, the preferred habitat of Atka mackerel is hard, 


rough, rocky substrates that are not ideal for bottom trawl 


surveys. Finally, the schooling behavior and patchy 


distribution of Atka mackerel lead to large variances in 


catch data (Lowe and Lauth 2003). 


It is important to understand the food habits of Atka 


mackerel in the Gulf of Alaska because it is a commercially 


valuable species. The total catch of Atka mackerel in the 


Gulf of Alaska in 2004 was 817 t, exceeding the total 


allowable catch for the first time since the quotas were 

 112 

implemented in 1998 (Lowe and Lauth 2004). Also, Atka 


mackerel were found as prey in the stomachs of Pacific cod 


and arrowtooth flounder, both commercially important fish 


species (Yang and Nelson 2000). 


General Diet 


Tables 32 and 33 show the total number of full 


stomachs, the total number of empty stomachs, the minimum 


and maximum fork length, average fork length, the minimum 


and maximum stomach fullness, the average fullness, the 


mean percent frequency of occurrence, and the mean percent 


total weight of the prey items of Atka mackerel in the Gulf 


of Alaska in 1999 and 2001, respectively. Euphausiids were 


the dominant food item found in the stomachs of Atka 


mackerel in 1999 and 2001, comprising 66% and 67% by weight, 


respectively. Larvaceans (15% by weight in 1999 and 2001) 


were the second most abundant prey item. In 1999, fish 


(sculpin and Pacific halibut) made up less than 1% of the 


diet by weight; however, in 2001, fish (Pacific sand lance) 


made up over 14% of the diet by weight. Atka mackerel 


consumed less than 1% by weight of crab (hermit and 


atelecyclid) in 2001, but no crab were found in the samples 


from 1999. Other prey items consumed by Atka mackerel were 


gastropods, jellyfish, pteropods, copepods, amphipods, 


isopods, and shrimp. 

 113 

In the 1996 study of Atka mackerel food habits in the 


Gulf of Alaska, the major prey was copepods (64% by 


weight)(Yang and Nelson 2000). However, in the current 


studies, euphausiids were the most abundant prey item, 


while copepods comprised less than 1% by weight. In the 


Aleutian Islands region, Yang (2003) found copepods and 


euphausiids to be the most important prey for Atka mackerel. 


Fish (primarily Pacific sand lance) was a more important 


part of the diet of Atka mackerel in 2001 (14% by weight) 


compared with 1996 and 1999 when, in both years, it made up 


less than 1% by weight of the prey. Similarly, in the 


eastern Bering Sea, fish (primarily walleye pollock) was 


the most important food of Atka mackerel representing 53% 


by weight of the diet (Brodeur and Livingston 1988). In 


1996 and 1999, gastropods were the most frequently 


encountered prey item in the stomachs of Atka mackerel, 71% 


frequency of occurrence and 43% frequency of occurrence, 


respectively; however, in 2001, gastropods were found less 


frequently (11% frequency of occurrence). The variations 


in the diets from the different years could be attributed 


to the patchy distribution of Atka mackerel, and the 


different areas that the samples were collected from. 

 114 

Table 32.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Pleurogrammus monopterygius (Atka mackerel) collected in the Gulf

 of Alaska in 1999. 

Prey items Percent frequency Percent weight 

Cnidaria 4.76 0.18 

Gastropoda (snail) 42.86 5.96 

Gymnosomata (pteropod) 23.81 8.48 

Clione limacina (pteropod) 4.76 0.44 

Calanoida (copepod) 9.52 0.19 

Isopoda (isopod) 4.76 3.43 

Euphausiacea (euphausiid) 38.10 20.24 

Thysanoessa sp. (euphausiid) 4.76 7.14 

Thysanoessa inermis (euphausiid) 26.19 38.60 

Caridea (shrimp) 7.14 0.01 

Copelata (larvacea) 19.05 14.50 

Teleostei (fish) 7.14 0.24 

Cottoidei (sculpin) 4.76 0.01 

Hippoglossus stenolepis (Pacific halibut) 4.76 0.58 

Total non-empty stomachs = 13 

Total prey number = 49 

Total prey weight = 61.291 g 

Total empty stomachs = 18 

Number of hauls = 7 

Full stomach summary statistics 

Average fork length = 46.76 cm 

Standard deviation of fork length = .83 cm 

Minimum fork length = 37 cm 

Maximum fork length = 51 cm 

Average fullness = 4.00 

Standard deviation of fullness = .71 

Minimum fullness = 2 

Maximum fullness = 7 

Empty stomach summary statistics 

Average fork length = 47.67 cm 

Standard deviation of fork length = 3.58 cm 

Minimum fork length = 40 cm 

Maximum fork length = 52 cm 
 115 

Table 33.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Pleurogrammus monopterygius (Atka mackerel) collected in the Gulf

 of Alaska in 2001. 

Prey items Percent frequency Percent weight 

Gastropoda (snail) 10.63 0.05 

Bivalvia (clam) 1.04 0.01 

Cephalopoda (squid and octopus) 16.67 1.72 

Calanoida (copepod) 28.54 0.73 

Hyperiidea (amphipod) 3.33 0.00 

Euphausiacea (euphausiid) 16.67 2.65 

Euphausiidae (euphausiid) 96.74 56.05 

Euphausia pacifica (euphausiid) 5.56 0.22 

Thysanoessa sp. (euphausiid) 5.56 0.69 

Thysanoessa inermis (euphausiid) 16.67 8.10 

Reptantia (crab) 16.67 0.05 

Paguridae (hermit crab) 8.33 0.04 

Atelecyclidae (crab) 8.33 0.11 

Copelata (larvacea) 38.96 15.08 

Teleostei (fish) 8.33 0.03 

Ammodytes hexapterus (Pacific sand lance) 16.67 14.46 

Total non-empty stomachs = 28 

Total prey number = 161 

Total prey weight = 231.458 g 

Total empty stomachs = 2 

Number of hauls = 6 

Full stomach summary statistics 

Average fork length = 37.33 cm 

Standard deviation of fork length = 1.61 cm 

Minimum fork length = 28 cm 

Maximum fork length = 51 cm 

Average fullness = 3.83 

Standard deviation of fullness = .30 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 42.00 cm 

Standard deviation of fork length = 1.41 cm 

Minimum fork length = 41 cm 

Maximum fork length = 43 cm 
 116 

Spinyhead Sculpin 


The estimated biomass for all sculpin species in the 


Gulf of Alaska in 1999 was 30,827 t (Gaichas et al. 1999). 


Spinyhead sculpin (Dasycottus setiger), along with other 


species of sculpin, are common bycatch in bottom trawls and 


pot fisheries (Gaichas et al. 1999). Spinyhead sculpin 


have been found to prey upon fish from food habits studies 


in the Aleutian Islands (Yang 2003) and near Kamchatka and 


the Kuril Islands (Tokranov and Orlov (2001). It is 


important to study the food habits of spinyhead sculpin in 


the Gulf of Alaska because it is a potential predator on 


commercially important species of fish, crab, and shrimp. 


General Diet 


Table 34 lists the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of spinyhead sculpin in 2001 in the Gulf 


of Alaska. Shrimp (mainly pandalids) comprised 93% by 


weight of the diet of spinyhead sculpin in the Gulf of 


Alaska in 2001. Fish (primarily zoarcids) made up 6% by 


weight of stomach contents. Mysids and hyperiid amphipods 


were also consumed by spinyhead sculpin. 

 117

 Tokranov and Orlov (2001) found that fish (48% by 


weight) was the most important food of spinyhead sculpin in 


the waters off southeastern Kamchatka and the northern 


Kuril Islands. In the Aleutian Islands region, fish (56% 


by weight) were also found to be the predominant prey for 


spinyhead sculpin (Yang 2003). In contrast, this study 


found that shrimp (mainly pandalid) was the most important 


food of spinyhead sculpin collected in the Gulf of Alaska. 


Shrimp comprised 93% of the total stomach contents weight; 


while fish was a much smaller portion of the diet, 


comprising less than 6% by weight. The small sample sizes, 


in both the current survey and the Aleutian Islands survey, 


could contribute to the variation in the food habits of 


spinyhead sculpin observed for the two regions. 

 118 

Table 34.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Dasycottus setiger ( spinyhead sculpin) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Pseudomma sp. (mysid) 53.85 1.74 

Hyperiidea (amphipod) 7.69 0.00 

Natantia (shrimp) 23.08 5.69 

Caridea (shrimp) 7.69 0.39 

Pandalidae (shrimp) 15.38 29.97 

Pandalus borealis (shrimp) 15.38 26.65 

Pandalus goniurus (shrimp) 7.69 10.22 

Crangonidae (shrimp) 30.77 3.75 

Crangon sp. (shrimp) 23.08 7.65 

Argis sp. (shrimp) 7.69 8.29 

Teleostei (fish) 15.38 0.05 

Non-gadoid fish remains 7.69 0.39 

Zoarcidae (eelpout) 7.69 5.20 

Total non-empty stomachs = 13 

Total prey number = 69 

Total prey weight = 25.361 g 

Total empty stomachs = 1 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 17.23 cm 

Standard deviation of fork length = 5.26 cm 

Minimum fork length = 12 cm 

Maximum fork length = 25 cm 

Average fullness = 3.85 

Standard deviation of fullness = 1.14 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 28.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 28 cm 

Maximum fork length = 28 cm 
 119 

Yellow Irish Lord 


The estimated biomass of yellow Irish lord 


(Hemilepidotus jordani) in the Gulf of Alaska was 20,220 t 


in 1999 (Gaichas et al. 1999). Of the individual sculpin 


species assessed in 1999, yellow Irish lord was the most 


abundant. Food habit studies from the eastern Bering Sea 


(Brodeur and Livingston 1988) and from coastal Kamchatka 


(Tokranov 1995) have found that crab is an important prey 


in the diet of yellow Irish lord. Because of the high 


abundance of yellow Irish lord, and its role as a predator 


of commercially important crabs, it is important to study 


the food habits of yellow Irish lord in the Gulf of Alaska. 


General Diet 


Table 35 lists the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of yellow Irish lord in 2001 in the Gulf 


of Alaska. Tanner crab (Chionoecetes bairdi), comprising 


85% by weight, was the most abundant prey of yellow Irish 


lord in the Gulf of Alaska in 2001. Lyre crab, Hyas 


lyratus, was also consumed, but only comprised 3% (by 


weight) of the total stomach content. Other prey items 

 120 

found in the stomachs of yellow Irish lord were copepods 


and hydrozoa. 


Brodeur and Livingston (1988) found fish (40% by 


weight), hermit crabs (27% by weight), and Chionoecetes 


crabs (11% by weight) were the most important prey for 


yellow Irish lord in the eastern Bering Sea. In contrast, 


the current study found yellow Irish lord fed mostly on 


Chionoecetes bairdi (85% by weight), while fish and hermit 


crabs were absent from the stomach contents from the Gulf 


of Alaska. Tokranov (1995) found similar results in the 


coastal waters off Kamchatka, where decapods (42% by weight)


were the most abundant food for yellow Irish lord. The 


small sample size of the current study and the different 


locations of collection could contribute to the variation 


between the studies discussed. 

 121 

Table 35.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Hemilepidotus jordani ( yellow Irish lord) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Hydrozoa 

Calanoida (copepod) 

Hyas lyratus (lyre crab) 

Chionoecetes bairdi (Tanner crab) 

50.00 

50.00 

50.00 

50.00 

2.32 

10.09 

2.85 

84.73 

Total non-empty stomachs = 2 

Total prey number = 785 

Total prey weight = 40.491 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 34.00 cm 

Standard deviation of fork length = 5.66 cm 

Minimum fork length = 30 cm 

Maximum fork length = 38 cm 

Average fullness = 5.50 

Standard deviation of fullness = 0.71 

Minimum fullness = 5 

Maximum fullness = 6 
 122 

Bigmouth Sculpin 


Bigmouth sculpin (Hemitripterus bolini) had an 


estimated biomass of 3,974 t in 1999 in the Gulf of Alaska 


(Gaichas et al. 1999). Bigmouth sculpin is a predatory 


sculpin with an extremely large mouth reaching a length of 


over 73 cm (Mecklenburg, et al. 2002). Previous studies 


have shown bigmouth sculpin preyed on commercially 


important fish in the eastern Bering Sea (Brodeur and 


Livingston 1988) and in the Aleutian Islands (Yang 2003). 


It is important to understand the food habits of bigmouth 


sculpin because it is a potential predator on commercially 


important fish species in the Gulf of Alaska. 


General Diet 


Tables 36 and 37 list the total number of full 


stomachs, the total number of empty stomachs, the minimum 


and maximum fork length, average fork length, the minimum 


and maximum stomach fullness, the average fullness, the 


mean percent frequency of occurrence, and the mean percent 


total weight of the prey items of bigmouth sculpin in the 


Gulf of Alaska in 1999 and 2001, respectively. Arrowtooth 


flounder (Atheresthes stomias) was the only prey item found 


in the single stomach of bigmouth sculpin analyzed in 1999 


from the Gulf of Alaska. In 2001, fish (zoarcids and 

 123 

sculpins) comprised 91% and hermit crab comprised 9% by 


weight of the total stomach contents, respectively. 


Bigmouth sculpin have preyed on commercially valuable 


fish in both the Aleutian Islands and the eastern Bering 


Sea. Yang (2003) found the main prey item for bigmouth 


sculpin in the Aleutian Islands was Atka mackerel (100% by 


weight), while in the eastern Bering Sea, walleye pollock 


(71% by weight) was the most abundant prey (Brodeur and 


Livingston 1988). Brodeur and Livingston (1988) also found 


Tanner crabs (less than 1%) in the diets of bigmouth 


sculpin in the eastern Bering Sea. The current study 


showed that fish (arrowtooth flounder, zoarcids, and 


cottids) were the most important prey for bigmouth sculpin 


in the Gulf of Alaska, but no Tanner crabs were found. The 


small sample size (one stomach in 1999 and two stomachs in 2001)


of the current study could contribute to the lack of more 


commercially important fish and crab found in the stomachs 


of bigmouth sculpin in the Gulf of Alaska. 

 124 

Table 36.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Hemitripterus bolini (bigmouth sculpin) collected in the Gulf of Alaska

 in 1999. 

Prey items Percent frequency Percent weight 

Atheresthes stomias (arrowtooth flounder) 100.00 100.00 

Total non-empty stomachs = 1 

Total prey number = 1 

Total prey weight = 191.58 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 64.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 64 cm 

Maximum fork length = 64 cm 

Average fullness = 6.00 

Standard deviation of fullness = 0 

Minimum fullness = 6 

 Maximum fullness = 6 
 125 

Table 37.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Hemitripterus bolini ( bigmouth sculpin) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Paguridae (hermit crab) 

Zoarcidae (eelpout) 

Cottoidei (sculpin) 

50.00 

50.00 

50.00 

8.59 

50.00 

41.41 

Total non-empty stomachs = 2 

Total prey number = 3 

Total prey weight = 20.468 g 

Total empty stomachs = 1 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 47.50 cm 

Standard deviation of fork length = 38.89 cm 

Minimum fork length = 20 cm 

Maximum fork length = 75 cm 

Average fullness = 4.00 

Standard deviation of fullness = 0 

Minimum fullness = 4 

Maximum fullness = 4 

Empty stomach summary statistics 

Average fork length = 51.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 51 cm

 Maximum fork length = 51 cm 
 126 

Darkfin Sculpin 


Darkfin sculpin (Malacocottus zonurus) had an 


estimated biomass of 312 t in 1999 in the Gulf of Alaska 


(Gaichas et al. 1999). In the Aleutian Islands area, 


shrimp and fish were preyed upon by darkfin sculpin (Yang 


2003). Darkfin sculpin was also found as prey in the 


stomachs of Pacific cod. In the Gulf of Alaska, it is 


important to understand the food habits of darkfin sculpin 


because of its role as both predator and prey in relation 


to commercially important species. 


General Diet 


Table 38 lists the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of darkfin sculpin in 2001 in the Gulf of 


Alaska. Polychaete worms (52% by weight) were the most 


common prey item found in the diet of darkfin sculpin in 


2001 in the Gulf of Alaska. Euphausiids ranked second at 


23% by weight. Other prey items found in stomachs of 


darkfin sculpin were shrimp (including pandalid and 


crangonid), amphipods (gammarid and caprellid), and mysids. 

 127 

Darkfin sculpin and blackfin sculpin (Malacocottus 


kincaidi) are believed by some researchers to be the same 


species and the two names are often used interchangeably 


(Mecklenburg et al. 2002). The diets of both species are 


compared for this report. In the Aleutian Islands, the 


most important prey items for darkfin sculpin were 


polychaetes (43% by weight), amphipods (20% by weight), and 


shrimp (16% by weight) (Yang 2003). Simenstad et al. (1977) 


found that blackfin sculpin in the Amchitka Island area fed 


primarily on polychaetes, isopods, shrimp, and amphipods. 


These two studies reported diets similar to the diet 


observed for darkfin sculpin in the current study. However, 


euphausiids (23% by weight) were a more important part of 


the diet in the current study compared to the Aleutian 


Islands study where euphausiids made up less than 1% (by 


weight) of the total stomach contents. The larger role of 


euphausiids in the current study may be because smaller 


darkfin sculpins (8.56 + 1.46 cm average fork length) were 


sampled compared to the larger darkfin sculpins (14.7 +


5.3 cm average fork length) sampled in the Aleutian Islands 


study, and the smaller sculpins may prey more on plankton 


than the larger sculpins. In contrast, darkfin sculpin, 


analyzed from southeastern Kamchatka and the northern Kuril 


Islands, preyed less on polychaetes and amphipods (less 

 128 

than 30% by weight) and more on gastropods and octopus 


(more than 50% by weight) (Tokranov and Orlov 2001). 

 129 

Table 38.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Malacocottus zonurus (darkfin sculpin) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 80.00 45.14 

Phyllodocidae (polychaete) 50.00 3.80 

Nephtyidae (polychaete) 3.33 3.55 

Pseudomma sp. (mysid) 50.00 0.54 

Gammaridea (amphipod) 63.33 6.14 

Caprellidea (amphipod) 10.00 4.27 

Euphausiacea (euphausiid) 3.33 1.48 

Euphausiidae (euphausiid) 50.00 21.74 

Natantia (shrimp) 50.00 3.26 

Caridea (shrimp) 10.00 6.58 

Pandalidae (shrimp) 3.33 2.95 

Crangonidae (shrimp) 50.00 0.54 

Total non-empty stomachs = 16 

Total prey number = 51 

Total prey weight = 4.85 g 

Total empty stomachs = 1 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 8.56 cm 

Standard deviation of fork length = 1.46 cm 

Minimum fork length = 7 cm 

Maximum fork length = 12 cm 

Average fullness = 5.19 

Standard deviation of fullness = 0.83 

Minimum fullness = 3 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 9.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 9 cm

 Maximum fork length = 9 cm 
 130 

Great Sculpin 


Great sculpins (Myoxocephalus polycanthocephalus) had 


an estimated biomass of 3,912 t in the Gulf of Alaska in 


1999 (Gaichas et al. 1999). The great sculpin is a large 


predatory sculpin that can grow to over 75 cm in length 


(Mecklenburg et al. 2002). Studies from the Aleutian 


Islands (Yang 2003) and eastern Bering Sea (Brodeur and 


Livingston 1988) found crab and fish to be the major prey 


items in the diet of great sculpin. The food habits of 


great sculpin in the Gulf of Alaska are important to study 


because this species is a potential predator of 


commercially important species of crab and fish. 


General Diet 


Table 39 lists the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of great sculpin in 2001 in the Gulf of 


Alaska. The only prey item found in the stomachs of great 


sculpin sampled in the Gulf of Alaska in 2001 was Tanner 


crab, Chionoecetes bairdi. 

 131 

Studies from different regions showed brachyuran crabs 


to be an important prey of the great sculpin. In the 


Amchitka Islands area, brachyuran and gammarid amphipods 


were also found in great sculpin stomachs (Simenstad et al. 


1977). In the eastern Bering Sea, Chionoecetes spp. (50% 


by weight) was its most important prey (Brodeur and 


Livingston 1988). In the Aleutian Islands, Yang (2003) 


found Tanner crab (31% by weight) and Korean horse-hair 


crab (Erimacrus isenbeckii) (21% by weight) to be the most 


important prey for great sculpins. These diets are similar 


to the diet of great sculpin in the current study, where 


Tanner crab was the only prey observed. Although fish 


(including the commercially important walleye pollock and 


Atka mackerel), were found in previous studies, no fish 


were observed in the current study. The lack of fish in 


the diet of great sculpin in the current study could be 


attributed to the small sample size. 

 132 

Table 39.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Myoxocephalus polyacanthocephalus ( great sculpin) collected in the 

 Gulf of Alaska in 2001. 

Prey items Percent frequency Percent weight

 Chionoecetes bairdi (Tanner crab) 100.00 100.00 

Total non-empty stomachs = 6 

Total prey number = 26 

Total prey weight = 498.282 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 46.10 cm 

Standard deviation of fork length = 6.62 cm 

Minimum fork length = 38 cm 

Maximum fork length = 58 cm 

Average fullness = 4.17 

Standard deviation of fullness = .75 

Minimum fullness = 3

 Maximum fullness = 5 
 133 

Dusky Snailfish 


Dusky snailfish (Liparis gibbus) is a widespread 


species of snailfish found in the Gulf of Alaska, Aleutian 


Islands, Bering Sea, and Arctic Alaska waters. Dusky 


snailfish can grow to a length of over 50 cm (Mecklenburg 


et al. 2002). Dusky snailfish is a potential predator on 


commercially valuable species of crab, fish, and shrimp in 


the Gulf of Alaska. 


General Diet 


Table 40 shows the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of dusky snailfish in 2001 in the Gulf of 


Alaska. Shrimp was the only prey found in the one dusky 


snailfish stomach that was sampled. Hippolytid shrimp 


accounted for 58% of the stomach contents by weight. Humpy 


shrimp (Pandalus goniurus) were also found in the stomach. 


They made up 42% by weight of the total stomach contents. 


In Canadian Arctic waters, amphipods, and polychaete 


worms were the most important prey in the diet of dusky 


snailfish (Atkinson and Percy 1992). In contrast, shrimp 


comprised 100% by weight of the diet of dusky snailfish in 

 134 

the current study from the Gulf of Alaska. However, only a 


single stomach was analyzed in the current study. The 


different locations of the two surveys discussed as well as 


the small sample size of the current study could be 


attributed to the differences in the prey observed. 

 135 

Table 40.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Liparis gibbus ( dusky snailfish) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Hippolytidae (shrimp) 100.00 58.15 

Pandalus goniurus (shrimp) 100.00 41.85 

Total non-empty stomachs = 1 

Total prey number = 13 

Total prey weight = 15.82 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 53.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 53 cm 

Maximum fork length = 53 cm 

Average fullness = 4.00 

Standard deviation of fullness = 0 

Minimum fullness = 4 

Maximum fullness = 4 
 136 

Pacific Sandfish 


In 2003 the estimated biomass of Pacific sandfish 


(Trichodon trichodon) was 3,894 t in the Gulf of Alaska 


(Nelson 2003). Pacific sandfish made up approximately 2% 


by weight of the diets of Pacific cod and Pacific halibut 


in the Gulf of Alaska in 1996 (Yang and Nelson 2000). Also, 


in the eastern Bering Sea, Pacific sandfish preyed upon 


commercially important fish such as walleye pollock 


(Brodeur and Livingston 1988). It is important to study 


the food habits of Pacific sandfish in the Gulf of Alaska 


because of its role as both predator and prey of 


commercially important fish. 


General Diet 


Table 41 shows the total number of full stomachs, the 


total number of empty stomachs, the minimum and maximum 


fork length, average fork length, the minimum and maximum 


stomach fullness, the average fullness, the mean percent 


frequency of occurrence, and the mean percent total weight 


of the prey items of Pacific sandfish in 2001 in the Gulf 


of Alaska. Mysids were the most important prey item for 


Pacific sandfish in the Gulf of Alaska in 2001, comprising 


85% by weight of the diet. Calanoid copepods made up 9% of 


the prey items. 

 137 

Brodeur and Livingston (1988) found that Pacific 


sandfish in the eastern Bering Sea consumed fish (97% by 


weight), including walleye pollock, as its major food. 


Crustaceans, including copepods, made up less than 2% (by 


weight) of the diet. In contrast, the current study found 


mysids and copepods to be the most abundant prey items, 


while fish were not consumed at all. The small sample size 


of the current study and the different locations of the two 


studies discussed could have contributed to the variations 


in the diets observed for Pacific sandfish. A more 


extensive analysis of the food habits of Pacific sandfish 


would need to be conducted to determine what role 


commercially valuable fish play in their diet in the Gulf 


of Alaska. 

 138 

Table 41.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Trichodon trichodon (Pacific sandfish) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Calanoida (copepod) 

Mysida (mysid) 

Unidentified organic material 

50.00 

50.00 

50.00 

8.61 

85.24 

6.15 

Total non-empty stomachs = 2 

Total prey number = 9 

Total prey weight = 0.569 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 15.50 cm 

Standard deviation of fork length = 0.71 cm 

Minimum fork length = 15 cm 

Maximum fork length = 16 cm 

Average fullness = 5.50 

Standard deviation of fullness = 0.71 

Minimum fullness = 5 

Maximum fullness = 6 
 139 

Searcher 


 Searchers (Bathymaster signatus) are bottom-dwelling 


members of the family Bathymasteridae. They are found from 


eastern Kamchatka, the Commander Islands, the Aleutian 


Islands and east to Washington State (Allen and Smith 1988). 


The diet of searchers has previously been studied by 


Tokranov (1998) from specimens collected near the northern 


Kurils and southeast Kamchatka. Tokranov found searchers 


to have a wide and diverse diet including many different 


types of invertebrates and fishes. Searchers have 


previously been found in the stomachs of commercially 


important predators such as Pacific cod, Pacific halibut, 


and arrowtooth flounder in the Gulf of Alaska (Yang and 


Nelson 2000). Because searchers are the prey of 


commercially important species, it is important to study 


the food habits to help understand the interrelationships 


of the groundfish community and the food web. 


General Diet 


Table 42 lists the total number of stomachs, total 


number of empty stomachs, mean percent frequency of 


occurrence of the prey, mean percent weight of prey, and 


full stomach summary statistics for stomachs collected in 


the Gulf of Alaska in 2001. Larvaceans were the most 


important prey in terms of both mean percent frequency of 

 140 

occurrence and mean percent weight at 91% and 81%, 


respectively. Searchers also consumed gammarid amphipod, 


jellyfish, polychaetes, and euphausiids (Table 42). 


The results of this study showed that searchers feed 


on many different kinds of invertebrates. Tokranov (1998) 


also found searchers of the northwestern Pacific to feed on 


many types of invertebrates, in particular, gammarids were 


the most abundant prey accounting for nearly 42% of the 


total stomach contents by weight. This study similarly 


found that gammarids were important invertebrate prey of 


searcher. Larvaceans were the most dominant prey in the 


current study but were not noted as prey in Tokranov’s 


study. Possible differences in the two studies may be 


accounted for by geographical separation, bathymetry and 


substrate differences, time of day and year, the small 


sample size at only one sampling location in this study, 


and localized abundance of prey. 

 141 

Table 42.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Bathymaster signatus (searcher) collected in the Gulf of Alaska in 

 2001. 

 Prey items Percent frequency Percent weight

 Scyphozoa (jellyfish) 9.09 2.52 

Phyllodocidae (polychaete) 18.18 1.02 

Nephtyidae (polychaete) 9.09 1.89 

Gammaridea (amphipod) 36.36 10.38 

Euphausiidae (euphausiid) 9.09 0.82 

Thysanoessa inermis (euphausiid) 18.18 2.51 

Copelata (larvacea) 90.91 80.85 

Total non-empty stomachs = 11 

Total prey number = 986 

Total prey weight = 13.408 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 26.00 cm 

Standard deviation of fork length = 2.17 cm 

Minimum fork length = 23 cm 

Maximum fork length = 29 cm 

Average fullness = 3.00 

Standard deviation of fullness = 1.04 

Minimum fullness = 2 

Maximum fullness = 5 
 142 

Northern Ronquil 


Northern ronquils (Ronquilis jordani) are bottom-


dwelling members of the family Bathymasteridae. They range 


from the Bering Sea and Amchitka Island in the Aleutians 


east through the Gulf of Mexico and south to the waters off 


Monterey, California; inhabiting depths less than 275 m 


(Mecklenburg et al. 2002). Northern ronquils have 


previously been found in the stomachs of arrowtooth 


flounder (Yang and Nelson 2000). To help further 


understanding of the interrelationships of the groundfish 


community, it is important to study the food habits of the 


Northern ronquils. 


General Diet 


Table 43 lists the total number of stomachs, total 


number of empty stomachs, mean percent frequency of 


occurrence of prey, mean percent weight of prey, and full 


stomach summary statistics for stomachs collected in the 


Gulf of Alaska. One northern ronquil stomach was collected 


in 2001 and contained food. The stomach contained five 


prey items from two taxonomic categories and weighed 


0.142 g. By percent weight, Phyllodocidae polychaetes were 


the most important prey accounting for 86% of the stomach 


contents weight. The remaining 14% of weight were gammarid 


amphipods. 

 143 

Table 43.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Ronquilis jordani (northern ronquil) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Phyllodocidae (polychaete) 100.00 85.92 

Gammaridea (amphipod) 100.00 14.08 

Total non-empty stomachs = 1 

Total prey number = 5 

Total prey weight = 0.142 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 16.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 16 cm 

Maximum fork length = 16 cm 

Average fullness = 2.00 

Standard deviation of fullness = 0 

Minimum fullness = 2

 Maximum fullness = 2 
 144 

Deepsea Sole 


Deepsea sole (Embassichthys bathybius) is a small-


mouthed flatfish that ranges from the Bering Sea and 


Aleutian Islands to Southern California at depths between 


320 to 1,433 m (Mecklenburg et al. 2002). In 2003, the 


estimated biomass of deepsea sole was 999 t in the Gulf of 


Alaska (Turnock et al. 2004). Deepsea sole is not managed 


as a single species in the Gulf of Alaska; however, because 


it is commonly caught with other flatfish, they are managed 


together as the larger complex “deep water flatfish” (NPFMC 


2004). In addition to deepsea sole, this complex includes 


Greenland turbot (Reinhardtius hippoglossoides) and Dover 


sole (Microstomus pacificus) and in 2004 the complex had an 


estimated biomass of 99,620 t (NPFMC 2004). Between 1978 


and 1995, deepsea sole had an average catch of 6 t in the 


Gulf of Alaska (Turnock et al. 2001). Deepsea sole is part 


of a commercially important complex of flatfish species and 


it is therefore important to study their food habits. 


General Diet 


Table 44 lists the total number of stomachs, total 


number of empty stomachs, mean percent frequency of 


occurrence of the prey, mean percent weight of prey, and 


full stomach summary statistics from deepsea sole stomachs 


collected in 2001 from the Gulf of Alaska. A total of 

 145 

three stomachs were collected from one haul, all of which 


contained food. Polychaetes were the most important prey 


item by weight; they accounted 72% of the total stomach 


contents weight. Octopus was the second most important 


prey by weight accounting for 18% of the stomach contents. 


Gammarid and caprellid amphipods accounted for the 


remaining stomach weight at 4.5% and 5.5%, respectively. 


All four prey categories were equally important in terms of 


mean percent frequency of occurrence at 33%. 

 146 

Table 44.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Embassichthys bathybius ( deepsea sole) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 

Octopoda (octopus) 

Gammaridea (amphipod) 

Caprellidea (amphipod) 

33.33 

33.33 

33.33 

33.33 

72.22 

17.92 

4.48 

5.38 

Total non-empty stomachs = 3 

Total prey number = 8 

Total prey weight = 0.558 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 41.30 cm 

Standard deviation of fork length = 1.53 cm 

Minimum fork length = 40 cm 

Maximum fork length = 43 cm 

Average fullness = 3.00 

Standard deviation of fullness = 0 

Minimum fullness = 3 

Maximum fullness = 3 
 147 

Rex Sole 


Rex sole (Errex zachirus) is a small-mouthed flatfish 


found in the Bering Sea and Aleutian Islands south to Baja 


California at depths less than 850 m (Mecklenburg et al. 


2002). Rex sole biomass estimates in the Gulf of Alaska 


decreased from 87,042 t in 1993 to 71,326 t in 2001 then 


increased to 99,950 t in 2003 (Turnock and A’mar 2004). 


Previous studies on the rex sole diet have been conducted 


off the coast of Oregon (Pearcy and Hancock 1978 and 


Kravitz et al. 1976) and found rex sole to feed primarily 


on polychaetes and crustaceans. As a species of commercial 


importance in the Gulf of Alaska, the food habits of rex 


sole is reviewed in this document. 


General Diet 


A total of 42 stomachs (41 with food) were analyzed 


from 7 hauls. Table 45 lists the total number of stomachs, 


total empty stomachs, mean percent frequency of occurrence, 


mean percent weight of prey, and full stomach summary 


statistics. Rex sole has a diverse diet eating many 


different types of invertebrates. Polychaetes and gammarid 


amphipods were the most frequently encountered prey with 


mean percent frequency of occurrences of 36% and 43%, 


respectively. At least 11 polychaete families were 


represented in the stomach contents and combined accounted 

 148 

for approximately 26% of the total prey weight. Despite 


the high frequency that gammarids were found to occur with, 


they accounted for only 4% of the total prey weight. 


Combined together, crustaceans accounted for 35% of the 


total prey weight. Echiuran worms were also frequently 


encountered (28% frequency of occurrence) and accounted for 


18% of the total prey weight. Vertebrates present in the 


diet of rex sole included gadid fish which had a frequency 


of occurrence of 14% and accounted for approximately 14% of 


the total prey weight and unidentified fish which accounted 


for another 5% of the total prey weight and were 


encountered in 4% of the stomachs. Other prey included 


pelagic snails, clams, copepods, mysids, cumaceans, isopods, 


amphipods, euphausiids, shrimp, hermit crabs, and 


sipunculans. 


In this study, we found the diet of rex sole to be 


primarily composed of crustaceans and polychaetes. 


Together, crustaceans and polychaetes accounted for 61% of 


the total prey weight. This is consistent with the 


findings of previous studies conducted on specimens from 


Oregon waters. Kravitz et al. (1976) found amphipods and 


polychaetes to be the first and second most frequently 


encountered prey, respectively. Pearcy and Hancock (1978) 

 149 

also found polychaetes followed by crustaceans to be the 


most important prey by weight. 

 150 

Table 45.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Errex zachirus (rex sole) collected in the Gulf of Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 36.19 5.94 

Aphroditidae (sea mouse) 1.90 0.14 

Phyllodocidae (polychaete) 24.29 4.02 

Nephtyidae (polychaete) 25.48 2.51 

Goniadidae (polychaete) 9.05 1.14 

Onuphidae (polychaete) 0.95 0.02 

Lumbrineridae 7.86 8.59 

Arabellidae (polychaete) 3.81 3.16 

Opheliidae (polychaete) 3.81 0.09 

Sternaspidae (polychaete) 2.86 0.08 

Maldanidae (polychaete) 1.90 0.04 

Pectinariidae (polychaete) 4.76 0.34 

Pteropoda 0.95 0.00 

Bivalvia (clam) 5.71 1.11 

Large calanoid (copepod) > 5mm 0.95 0.00 

Mysida (mysid) 12.38 6.29 

Cumacea (cumacean) 5.71 2.82 

Isopoda (isopod) 6.67 0.49 

Gammaridea (amphipod) 42.86 4.46 

Hyperiidea (amphipod) 22.86 5.29 

Caprellidae (amphipod) 2.86 0.06 

Euphausiacea (euphausiid) 4.05 3.79 

Euphausiidae (euphausiid) 9.52 5.15 

Thysanoessa sp. (euphausiid) 1.90 1.97 

Thysanoessa inermis (euphausiid) 8.57 3.02 

Natantia (shrimp) 0.95 0.00 

Caridea (shrimp) 4.05 0.40 

Hippolytidae (shrimp) 0.95 0.01 

Eualus sp. (shrimp) 0.95 0.04 

Pandalidae (shrimp) 3.10 0.85 

Pandalus sp. (shrimp) 0.95 0.01 

Crangonidae (shrimp) 0.95 0.00 

Crangon spp. (shrimp) 5.71 0.25 

Crangon dalli (shrimp) 0.95 0.06 

Paguridae (hermit crab) 0.95 0.00 

Sipuncula (marine worm) 9.52 0.66 

Echiura (marine worm) 28.10 17.95 

Teleostei (fish) 4.05 4.92 

Gadidae (gadid fish) 14.29 14.29 
 151 

Table 45.--Continued. 

Total non-empty stomachs = 41 

Total prey number = 1028 

Total prey weight = 74.05 g 

Total empty stomachs = 1 

Number of hauls = 7 

Full stomach summary statistics 

Average fork length = 37.40 cm 

Standard deviation of fork length = 2.21 cm 

Minimum fork length = 24 cm 

Maximum fork length = 50 cm 

Average fullness = 3.29 

Standard deviation of fullness = .15 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 35.00 cm 

Standard deviation of fork length = 0 cm 

Minimum fork length = 35 cm 

Maximum fork length = 35 cm 
 152 

Flathead Sole 


Flathead sole (Hippoglossoides elassodon) is a large-


mouthed flatfish ranging from the Bering Sea and Aleutian 


Islands to northern California at depths up to 1,000 m 


(Mecklenburg et al. 2002). In 2004, flathead sole had an 


estimated exploitable biomass in the Gulf of Alaska of 


292,670 t (NPFMC 2004). This is an increase from the 2001 


estimated exploitable biomass of 170, 915 t (Turnock et al. 


2003). Previous studies of flathead sole food habits in 


Alaska have shown that they consume commercially important 


prey including walleye pollock (Theragra chalcogramma) and 


snow and Tanner crabs (Chionoecetes spp.) (Yang and Nelson 


2000, Pacunski 1990). Because they are a commercially 


important species and they prey on other commercially 


important species, flathead sole are included in this study. 


General Diet 


Thirty-one flathead sole stomachs from three hauls 


were collected in the Gulf of Alaska in 2001, 16 of which 


contained food. In 1999, 15 flathead sole were collected 


in one haul and nine fish of them had stomachs containing 


prey. Tables 46 and 47 list the total number of stomachs, 


total empty stomachs, mean percent frequency of occurrence, 


mean percent weight of prey, and full stomach summary 


statistics for stomachs collected in the Gulf of Alaska in 

 153 

1999 and 2001. Shrimp were the most important prey by 


weight in the flathead sole diet in both 1999 (81%) and 


2001 (66%). Specifically, pandalid shrimp accounted for 


41% (1999) and 64% (2001) of the of the total prey weight 


and were also the most important prey in terms of frequency 


of occurrence in 2001 (Table 47). Other invertebrate prey 


included polychaetes, cumaceans, isopods, amphipods, 


euphausiids, brittle stars, and unidentified crab. Fishery 


offal was the second most important prey in terms of weight 


in 2001 at 17%. Fish were not present in flathead sole 


stomachs from 1999 but were represented in 2001 by 


stichaeids (6% of the total prey weight). 


The results from 1999 and 2001 both show shrimp, 


particularly pandalids, as the most important prey to 


flathead sole. Yang and Nelson (2000) conducted a similar 


study in the Gulf of Alaska in 1993 and also found pandalid 


shrimp to be the most important prey (39% by weight) in the 


flathead sole diet. In addition, Yang and Nelson (2000) 


found walleye pollock among the prey from 1993 Gulf of 


Alaska specimens, however they were of little importance 


accounting for less than 1% of the total prey weight. No 


walleye pollock were found in this study of 1999 and 2001 


flathead sole stomachs. Similarly, tanner crabs were found 


to account for 3% of the prey by weight in 1993 but were 

 154 

not present in 1999 or 2001 (Yang and Nelson 2000). Some 


of the differences between the previous study by Yang and 


Nelson (2000) and this current one may be due to the small 


sample size and limited number of sampling stations in 1999 


and 2001. 

 155 

Table 46.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight of Hippoglossoides elassodon (flathead sole) collected in the Gulf of

 Alaska in 1999. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 11.11 1.69 

Yoldia sp. (clam) 11.11 1.69 

Isopoda (isopod) 11.11 1.69 

Gammaridea (amphipod) 22.22 4.64 

Euphausiidae (euphausiid) 11.11 5.49 

Caridea (shrimp) 11.11 10.97 

Hippolytidae (shrimp) 22.22 29.96 

Pandalus jordani (shrimp) 11.11 40.51 

Reptantia (crab) 11.11 3.38 

Total non-empty stomachs = 9 

Total prey number = 10 

Total prey weight = 2.37 g 

Total empty stomachs = 6 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 26.90 cm 

Standard deviation of fork length = 6.19 cm 

Minimum fork length = 17 cm 

Maximum fork length = 36 cm 

Average fullness = 3.00 

Standard deviation of fullness = .82 

Minimum fullness = 2 

Maximum fullness = 4 

Empty stomach summary statistics 

Average fork length = 34.00 cm 

Standard deviation of fork length = 3.03 cm 

Minimum fork length = 29 cm 

Maximum fork length = 37 cm 
 156 

Table 47.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight of Hippoglossoides elassodon (flathead sole) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 4.76 0.17 

Pseudomma sp. (mysid) 14.29 0.22 

Cumacea (cumacean) 4.76 0.01 

Isopoda (isopod) 4.76 0.37 

Hippolytidae (shrimp) 4.76 0.10 

Eualus spp. (shrimp) 4.76 0.09 

Pandalidae (shrimp) 14.29 12.38 

Pandalus spp. (shrimp) 21.43 20.11 

Pandalus borealis (shrimp) 26.19 31.79 

Crangon spp. (shrimp) 9.52 1.15 

Argis sp. (shrimp) 4.76 0.05 

Reptantia (crab) 4.76 0.60 

Ophiurida (brittle star) 9.52 2.80 

Ophiura sarsi (brittle star) 14.29 7.42 

Teleostei (fish) 4.76 0.01 

Stichaeidae (prickleback) 4.76 5.68 

Fishery offal 4.76 17.05 

Total non-empty stomachs = 16 

Total prey number = 64 

Total prey weight = 46.041 g 

Total empty stomachs = 15 

Number of hauls = 3 

Full stomach summary statistics 

Average fork length = 37.75 cm 

Standard deviation of fork length = 6.03 cm 

Minimum fork length = 30 cm 

Maximum fork length = 51 cm 

Average fullness = 3.69 

Standard deviation of fullness = 1.35 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 34.80 cm 

Standard deviation of fork length = 10.77 cm 

Minimum fork length = 14 cm 

Maximum fork length = 47 cm 
 157 

Butter Sole 


Butter sole (Isopsetta isolepis) is a small-mouthed 


flatfish found throughout the Gulf of Alaska from Amchitka 


Island in the Aleutians to California, usually at depths 


less than 150 m (Allen and Smith 1988). From 1993 to 2001, 


butter sole biomass estimates in the Gulf of Alaska 


decreased from 29,809 to 9,812 t, and then increased to 


31,148 t in 2003 (Turnock et al. 2003). Butter sole is not 


managed as a single species but is part of a larger shallow 


water flatfish complex including seven other flatfish 


species (NPFMC 2004). As part of a larger management body 


of flatfish, it is important to study the food habits of 


butter sole. 


General Diet 


In 2001, 10 stomachs from butter sole collected from 


one haul in the Gulf of Alaska were analyzed. Only two of 


the stomachs contained prey (Table 48). Cumaceans 


accounted for 100% of the prey both by weight and frequency. 


Due to the small sample size and the high proportion (80%) 


of empty stomachs it is difficult to make any general 


conclusions about the diet of butter sole based on the 


stomach contents. 

 158 

Table 48.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight of Isopsetta isolepis (butter sole) collected in the Gulf of Alaska in 2001. 

Prey items Percent frequency Percent weight 

Cumacea (cumacean) 100.00 100.00 

Total non-empty stomachs = 2 

Total prey number = 45 

Total prey weight = 0.27 g 

Total empty stomachs = 8 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 48.50 cm 

Standard deviation of fork length = 3.54 cm 

Minimum fork length = 46 cm 

Maximum fork length = 51 cm 

Average fullness = 2.00 

Standard deviation of fullness = .00 

Minimum fullness = 2 

Maximum fullness = 2 

Empty stomach summary statistics 

Average fork length = 37.50 cm 

Standard deviation of fork length = 6.35 cm 

Minimum fork length = 25 cm

 Maximum fork length = 45 cm 
 159 

Southern Rock Sole 


Southern rock sole (Lepidopsetta bilineata) is a 


small-mouthed flatfish found in the southeast Bering Sea, 


in the Aleutian Islands around the Islands of Four 


Mountains, and as far south as Baja California at depths 


shallower than 340 m (Mecklenburg et al. 2002). Southern 


rock sole has been a separate species from northern rock 


sole (Lepidopsetta polyxystra) since the revision of the 


genus Lepidopsetta in 2000 (Orr and Matarese 2000). Both 


species are managed as part of the shallow water flatfish 


complex which includes six other species (NPFMC 2004). In 


2003, the exploitable biomass of GOA southern rock sole was 


the largest of all the species in the shallow water 


flatfish complex at 127,267 t (Turnock et al. 2003). From 


2001 to 2003, the catch of southern rock sole declined from 


2,462 to 2,103 t (Turnock et al. 2003). Because southern 


rock sole is both abundant and commercially important, its 


food habit is reviewed in this document. 


General Diet 


Tables 49 and 50 list the total number of stomachs, 


total empty stomachs, number of hauls, mean percent 


frequency of occurrence, mean percent weight of prey, and 


full stomach summary statistics for stomachs collected in 


1999 and 2001 in the Gulf of Alaska. Polychaetes were 

 160 

important food in the diet of southern rock sole in both 


1999 and 2001 (27% and 16% by weight, respectively). 


Crustaceans accounted for 5% of the prey weight in 1999 but 


had a much stronger presence in 2001 comprising 35% of the 


prey weight. In both years brittle stars were frequently 


encountered, ranking second in frequency of occurrence in 


1999 (30%) and first in 2001 (41%). Brittle stars 


represented 10% of the prey weight in 1999 and 35% in 2001. 


Fish prey had a much stronger presence in 1999 than in 2001 


(23% and 2% by weight, respectively). Sculpins were the 


most prominent fish prey in 1999, representing 13% of the 


mean total prey weight, followed by Pacific sand lance 


which accounted for 9% of the total prey weight. Walleye 


pollock were only found as prey in 1999 and were of little 


importance (<1% by weight). Stichaeids were the only fish 


prey found in 2001 and accounted for 2% of the total prey 


weight. 


Polychaetes and brittle stars were featured parts of 


the southern rock sole diet in both 1999 and 2001, in terms 


of mean percent frequency of occurrence and mean percent 


total weight. Other prey that had a notable presence in 


weight and frequency in 1999 and were not present in 2001 


or were present in a much more diminished capacity, 


included sipunculans, fish, and crustaceans. In 1999, 

 161 

sipunculans accounted for 15% of the mean total prey weight 


but were absent in 2001. Fish prey combined represented 


23% of the mean total prey weight in 1999. Sculpins had a 


mean percent frequency of occurrence of 14% in that year. 


In 2001, sculpins were not present in the stomach contents, 


and fish prey only comprised 2% of the total stomach 


contents weight. Crustaceans together accounted for 5% of 


the prey weight in 1999, but had a much more pronounced 


presence in 2001 constituting 35% of the prey weight. The 


differences between study years may be a reflection of 


flexibility in the southern rock sole diet, sample size, 


different sample locations, and prey availability. 

 162 

Table 49.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lepidopsetta bilineata (southern rock sole) collected in the Gulf of 

Alaska in 1999. 

Prey items Percent frequency Percent weight 

Anthozoa (anemome) 1.25 0.10 

Polychaeta (worm) 51.20 23.30 

Phyllodocidae (polychaete) 1.25 0.08 

Onuphidae (polychaete) 1.25 0.09 

Cirratulidae (polychaete) 1.25 0.90 

Opheliidae (polychaete) 3.75 2.90 

Serpulidae (polychaete) 0.96 0.19 

Mollusca 4.96 0.28 

Bivalvia (clam) 13.13 2.63 

Pectinidae (scallops) 5.58 1.25 

Cardiidae (cockles) 1.85 1.55 

Cephalopoda (squid and octopus) 1.85 0.31 

Cumacea (cumacean) 4.09 0.06 

Isopoda (isopod) 1.92 0.14 

Gammaridea (amphipod) 15.19 1.31 

Hyperiidea (amphipod) 1.56 0.01 

Euphausiidae (euphausiid) 1.92 0.01 

Natantia (shrimp) 5.70 0.49 

Crangonidae (shrimp) 0.89 0.09 

Argis sp. (shrimp) 0.96 1.48 

Paguridae (hermit crab) 3.49 0.55 

Paguridae legs (hermit crabs) 0.96 0.13 

Decapoda brachyura (crab) 0.96 0.13 

Hyas spp. (lyre crab) 1.56 0.35 

Cancer oregonensis (pygmy Cancer crab) 0.96 0.05 

Pinnixa sp. (pea crab) 2.81 0.10 

Sipuncula (marine worm) 7.52 15.47 

Echiura (marine worm) 1.25 0.14 

Priapulida (worm) 4.38 0.98 

Asteroidea (starfish) 2.50 0.43 

Ophiurida (brittle star) 30.07 10.30 

Echinoidea (sea urchin and sand dollar) 1.56 0.65 

Clypeasteroida (sand dollar) 4.24 0.29 

Holothuroidea (sea cucumber) 4.60 1.11 

Enteropneusta (acorn worm) 3.13 8.77 
 163

 Table 49.--Continued. 

Prey items Percent frequency Percent weight 

Non-gadoid fish remains 0.89 0.19 

Theragra chalcogramma (walleye pollock) 0.89 0.84 

Cottoidei (sculpin) 14.06 12.81 

Ammodytes hexapterus (Pacific sand lance) 7.50 8.79 

Pleuronectidae (flatfish) 1.79 0.35 

Unidentified worm-like organism 2.81 0.05 

Unidentified tube 2.81 0.33 

Total non-empty stomachs = 63 

Total prey number = 121 

Total prey weight = 173.655 g 

Total empty stomachs = 43 

Number of hauls = 8 

Full stomach summary statistics 

Average fork length = 34.18 cm 

Standard deviation of fork length = 2.85 cm 

Minimum fork length = 15 cm 

Maximum fork length = 50 cm 

Average fullness = 3.88 

Standard deviation of fullness = .27 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 36.86 cm 

Standard deviation of fork length = 7.01 cm 

Minimum fork length = 24 cm 

Maximum fork length = 49 cm 
 164 

Table 50.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lepidopsetta bilineata (southern rock sole) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 25.56 9.92 

Phyllodocidae (polychaete) 5.00 0.11 

Nereidae (polychaete) 5.56 0.08 

Nephtyidae (polychaete) 2.22 0.96 

Goniadidae (polychaete) 33.33 3.98 

Flabelligeridae (polychaete) 2.78 0.02 

Opheliidae (polychaete) 2.22 0.76 

Maldanidae (polychaete) 2.78 0.01 

Bivalvia (clam) 19.44 5.08 

Isopoda (isopod) 5.00 0.24 

Gammaridea (amphipod) 26.11 6.90 

Hyperiidea (amphipod) 2.78 0.07 

Decapoda Reptantia legs (crabs) 16.67 10.23 

Paguridae (hermit crab) 4.44 3.21 

Hyas lyratus (lyre crab) 16.67 13.89 

Echiura (marine worm) 8.33 0.10 

Ophiurida (brittle star) 41.11 23.83 

Ophiura sp. (brittle star) 2.22 3.84 

Ophiura sarsi (brittle star) 8.89 7.36 

Echinoidea (sea urchin and sand dollar) 5.56 0.21 

Clypeasteroida (sand dollar) 5.00 4.64 

Holothuroidea (sea cucumber) 5.56 2.42 

Stichaeidae (prickleback) 2.22 2.15 

Total non-empty stomachs = 29 

Total prey number = 257 

Total prey weight = 38.335 g 

Total empty stomachs = 4 

Number of hauls = 3 

Full stomach summary statistics 

Average fork length = 32.23 cm 

Standard deviation of fork length = 1.58 cm 

Minimum fork length = 19 cm 

Maximum fork length = 43 cm 

Average fullness = 3.67 

Standard deviation of fullness = .25 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 35.00 cm 

Standard deviation of fork length = 12.83 cm 

Minimum fork length = 22 cm

 Maximum fork length = 47 cm 
 165 

Northern Rock Sole 


Northern rock sole (Lepidopsetta polyxystra) is a 


small-mouthed flatfish found throughout the Bering Sea 


shelf and Aleutian Islands south to Washington at depths 


less than 250 m (Mecklenburg et al. 2002). Northern and 


southern rock sole have previously been considered a single 


species until the genus Lepidopsetta was revised in 2000 


and the new species L. polyxystra was described (Orr and 


Matarese 2000). The estimated exploitable biomass of 


northern rock sole increased from 64,240 t in 2001 to 


79,998 t in 2003. The catch increased as well from 2,711 t 


in 2001 to 3,031 t in 2002 but then decreased to 1,279 t in 


2003. Northern rock sole are managed as part of the 


shallow water flatfish complex in the Gulf of Alaska. 


Because of their commercial importance, their food habits 


are included in this study. 


General Diet 


Tables 51 and 52 list the total number of stomachs, 


total number of empty stomachs, number of hauls, mean 


percent frequency of occurrence, mean percent weight of 


prey, and full stomach summary statistics for stomachs 


collected in 1999 and 2001 in the Gulf of Alaska. In both 


years polychaetes were present in the diet of northern rock 


sole. They accounted for 39% of the prey by weight in 1999 

 166 

and 13% in 2001. Brittle stars also figured prominently in 


both years representing 20% of the prey by weight in 1999 


and 29% in 2001. In terms of fish prey, Pacific sand lance 


was consumed in both years and constituted 7% of the prey 


weight in 1999 and 19% in 2001. In 1999, unidentified 


algae comprised 20% of the mean percent total weight but 


were not present in 2001. Conversely, in 2001, sea 


cucumbers constituted 23% of the mean percent total weight 


but were absent from the prey in 1999. Other prey included 


mollusk, clams, cephalopods, cumaceans, isopods, amphipods, 


euphausiids, shrimp, crab, hermit crab, and echinoderms. 


Both 1999 and 2001 show polychaetes, brittle stars, 


and Pacific sand lance to be featured parts of the northern 


rock sole diet. A study of rock sole diet in the Bering 


Sea between 1984 and 1988 showed polychaetes to be of 


paramount importance in terms of frequency and weight (Lang 


1992). However, Lang’s study was prior to the revision of 


the genus Lepidopsetta and did not differentiate between 


northern and southern rock sole. Similar to the results of 


this study, Lang (1992) also showed that Pacific sand lance 


were the primary fish prey in 1988. In waters off the 


northern Kurils and southeastern Kamchatka, amphipods were 


found to be the most dominant prey for L. polyxystra in 

 167 

terms of frequency of occurrence at 71%, followed by 


polychaetes at 45% (Kuznetsova and Kunin 2002). 

 168 

Table 51.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lepidopsetta polyxystra (northern rock sole) collected in the Gulf of

 Alaska in 1999. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 47.71 38.51 

Maldanidae (polychaete) 5.00 0.52 

Mollusca 9.04 1.77 

Bivalvia (clam) 3.76 0.05 

Cephalopoda (squid and octopus) 2.50 0.15 

Cumacea (cumacean) 1.54 0.03 

Arcturidae (isopod) 1.54 0.19 

Gammaridea (amphipod) 14.91 2.60 

Natantia (shrimp) 2.50 0.77 

Reptantia (crab) 1.54 0.04 

Pinnixa sp. (pea crab) 5.00 3.00 

Ophiurida (brittle star) 28.65 20.40 

Clypeasteroida (sand dollar) 4.62 4.59 

Teleostei (fish) 3.08 0.01 

Ammodytes hexapterus (Pacific sand lance) 1.54 6.87 

Unidentified tube 3.08 0.47 

Unidentified algae 20.00 20.00 

Total non-empty stomachs = 36 

Total prey number = 46 

Total prey weight = 57.837 g 

Total empty stomachs = 21 

Number of hauls = 5 

Full stomach summary statistics 

Average fork length = 29.66 cm 

Standard deviation of fork length = 2.05 cm 

Minimum fork length = 17 cm 

Maximum fork length = 41 cm 

Average fullness = 3.80 

Standard deviation of fullness = .56 

Minimum fullness = 3 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 32.57 cm 

Standard deviation of fork length = 4.48 cm 

Minimum fork length = 23 cm 

Maximum fork length = 40 cm 
 169 

Table 52.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Lepidopsetta polyxystra (northern rock sole) collected in the Gulf of

 Alaska in 2001. 

Prey items Percent frequency Percent weight

 Polychaeta (worm) 24.76 8.66 

Phyllodocidae (polychaete) 10.24 0.69 

Nereidae (polychaete) 13.33 0.38 

Nephtyidae (polychaete) 10.71 1.05 

Glyceridae (polychaete) 7.14 0.44 

Arabellidae (polychaete) 6.67 0.50 

Cirratulidae (polychaete) 3.57 0.69 

Capitellidae (polychaete) 7.14 0.76 

Maldanidae (polychaete) 3.33 0.01 

Bivalvia (clam) 26.67 5.84 

Isopoda (isopod) 6.90 0.26 

Gammaridea (amphipod) 10.24 1.20 

Hyperiidea (amphipod) 10.00 0.14 

Caprellidea (amphipod) 6.67 0.01 

Euphausiacea (euphausiid) 3.57 0.07 

Hippolytidae (shrimp) 3.33 0.01 

Paguridae (hermit crab) 13.57 0.70 

Ophiurida (brittle star) 68.10 23.73 

Chilophiurina (brittle star) 3.57 0.42 

Ophiura sarsi (brittle star) 7.14 4.62 

Echinoidea (sea urchin and sand dollar) 6.67 1.47 

Clypeasteroida (sand dollar) 10.48 0.51 

Holothuroidea (sea cucumber) 30.00 23.05 

Ammodytes sp. (sand lance) 7.14 18.81 

Unidentified worm-like organism 14.29 5.99 

Total non-empty stomachs = 29 

Total prey number = 398 

Total prey weight = 55.844 g 

Total empty stomachs = 2 

Number of hauls = 2 

Full stomach summary statistics 

Average fork length = 29.20 cm 

Standard deviation of fork length = .75 cm 

Minimum fork length = 17 cm 

Maximum fork length = 40 cm 

Average fullness = 4.00 

Standard deviation of fullness = .05 

Minimum fullness = 3 

Maximum fullness = 5 

Empty stomach summary statistics 

Average fork length = 22.00 cm 

Standard deviation of fork length = 4.24 cm 

Minimum fork length = 19 cm

 Maximum fork length = 25 cm 
 170 

Yellowfin Sole 


Yellowfin sole (Limanda aspera) is a small-mouthed 


flatfish with an extensive range in the North Pacific that 


stretches from the Sea of Japan to the Bering and Beaufort 


Seas, the Aleutian Islands and through the Gulf of Alaska 


to British Columbia (Mecklenburg et al. 2002). The 


estimated exploitable biomass in 2003 for the Gulf of 


Alaska was 54,738 t and the catch was 58.8 t (Turnock et al. 


2003). A study in the southwestern Bering Sea from 1979 to 


1986 on the food habits of yellowfin sole found their diet 


to be chiefly composed of polychaetes and bivalves 


(Tokranov 1990). Similarly, a study in the eastern Bering 


Sea from 1984 to 1988 found polychaetes, gammarid amphipods,


marine worms, and bivalves to be the most important prey 


items in the yellowfin sole diet (Lang 1992). As an 


abundant and commercially important species, the food 


habits of yellowfin sole is examined in this document. 


General Diet 


Tables 53 and 54 list the total number of stomachs, 


total empty stomachs, number of hauls, mean percent 


frequency of occurrence, mean percent weight of prey, and 


full stomach summary statistics for stomachs collected in 


1999 and 2001 in the Gulf of Alaska. In terms of mean 


percent frequency of occurrence and mean percent total 

 171 

weight, polychaetes were the most important prey in 1999 


(48% and 35%, respectively). Bivalves were second in both 


categories in 1999 at 37% frequency of occurrence and 26% 


by weight. Other prey that figured prominently in mean 


percent frequency of occurrence in 1999 include gammarid 


amphipods (24%) and cumaceans (19%). By weight, crangonid 


shrimp (including Crangon dalli) constituted a notable 


portion of the mean percent total weight at 10%. The only 


commercial prey was Tanner crab (Chionoecetes bairdi), but 


was of little importance accounting for less than 1% mean 


percent total weight and having a 2% mean frequency of 


occurrence. 


In 2001 only two stomachs from yellowfin sole 


collected from one haul. These revealed a much smaller 


prey data set than 1999. All were examined. Three prey 


groups, polychaetes, copepods, and cumaceans were equal 


with respect to mean percent frequency of occurrence (50%). 


However, by weight, cumaceans were the dominant prey items; 


they comprised 91% of the prey weight. 


The 1999 results feature polychaetes and bivalves as 


the most prevalent prey groups by both frequency and weight. 


This is consistent with the findings of both Tokranov (1990) 


in the southwest Bering Sea and Lang (1992) in the eastern 


Bering Sea. Polychaetes and bivalves combined accounted 

 172 

for 61% of the mean percent total weight in 1999. Tokranov 


(1990) found these two taxonomic groups to account for 43­


81% (by weight) of the yellowfin sole prey. Lang (1992) 


had these two prey categories among the top three in both 


frequency of occurrence and by percent weight. The 2001 


results from this document show a departure from the 


previously observed pattern of results in 1999 and the 


other two studies from the Bering Sea. This may be 


explained in part by the small sample size (n=2) for 2001. 

 173 

Table 53.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight of Limanda aspera (yellowfin sole) collected in the Gulf of Alaska 

in 1999. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 48.26 34.67 

Mollusca 1.79 0.86 

Gastropoda (snail) 2.78 1.25 

Bivalvia (clam) 37.26 23.35 

Nuculana sp. (clam) 3.13 1.17 

Nuculana fossa (clam) 3.13 0.59 

Siliqua sp. (razor clam) 1.92 1.32 

Calanoida (copepod) 1.92 0.00 

Cumacea (cumacean) 18.75 1.00 

Gammaridea (amphipod) 24.03 2.16 

Euphausiidae (euphausiid) 1.92 0.03 

Decapoda (shrimp and crab) 1.79 0.23 

Crangonidae (shrimp) 5.49 2.56 

Crangon dalli (shrimp) 3.57 7.75 

Reptantia (crab) 1.79 0.39 

Paguridae (hermit crab) 5.63 5.87 

Chionoecetes bairdi (Tanner crab) 1.92 0.03 

Pinnotheridae (pea crab) 3.13 0.78 

Pinnixa sp. (pea crab) 3.13 2.20 

Echinodermata (sea star, cucumber, urchin) 1.92 0.08 

Ophiurida (brittle star) 6.97 2.35 

Brittle star legs (brittle star) 3.85 0.07 

Echinacea sp. (sea urchin) 1.92 0.09 

Clypeasteroida (sand dollar) 1.92 1.37 

Unidentified organic material 2.78 2.72 

Unidentified worm-like organism 5.05 7.12 

Total non-empty stomachs = 44 

Total prey number = 102 

Total prey weight = 48.98 g 

Total empty stomachs = 17 

Number of hauls = 4 

Full stomach summary statistics 

Average fork length = 28.15 cm 

Standard deviation of fork length = 2.07 cm 

Minimum fork length = 15 cm 

Maximum fork length = 42 cm 

Average fullness = 3.25 

Standard deviation of fullness = .31 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 28.94 cm 

Standard deviation of fork length = 4.93 cm 

Minimum fork length = 20 cm 

Maximum fork length = 36 cm 
 174 

Table 54.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight of Limanda aspera (yellowfin sole) collected in the Gulf of Alaska

 in 2001. 

Prey items Percent frequency Percent weight 

Polychaeta (worm) 

Calanus spp. (copepod) 

Cumacea (cumacean) 

50.00 

50.00 

50.00 

3.97 

5.44 

90.59 

Total non-empty stomachs = 2 

Total prey number = 71 

Total prey weight = 0.478 g 

Total empty stomachs = 0 

Number of hauls = 1 

Full stomach summary statistics 

Average fork length = 40.00 cm 

Standard deviation of fork length = 2.83 cm 

Minimum fork length = 38 cm 

Maximum fork length = 42 cm 

Average fullness = 3.00 

Standard deviation of fullness = 1.41 

Minimum fullness = 2 

Maximum fullness = 4 
 175 

Dover Sole 


The Dover sole (Microstomus pacificus) is a small-


mouthed flatfish found from the Bering Sea and Aleutian 


Islands south to Baja California at depths up to 1,200 m 


(Mecklenburg et al. 2002). In 2005, Dover sole had an 


estimated exploitable biomass of 102,395 t in the Gulf of 


Alaska (Turnock et al. 2004b). Dover sole is managed in 


the Gulf of Alaska as part of the deep-water flatfish 


complex which includes Greenland turbot (Reinhardtius 


hippoglossoides) and deepsea sole (Embassichthys bathybius) 


(NPFMC 2004). The catch of Dover sole increased from 23 t 


in 1986 to 9,741 t in 1991. It gradually decreased to 492 t 


in 2002. The catch was 682 t in 2004 (Turnock et al. 2004b). 


Because Dover sole is a commercially important species, its 


food habits are explored in this study. 


General Diet 


Table 55 lists the total number of stomachs, total 


empty stomachs, number of hauls, mean percent frequency of 


occurrence, mean percent weight of prey, and full stomach 


summary statistics for Dover sole collected in 2001 in the 


Gulf of Alaska. Polychaetes were the most dominant prey 


overall, accounting for 49% of the prey by mean percent 


total weight and having the highest mean percent frequency 


of occurrence (27%). Secondarily, brittle stars 

 176 

represented 24% of the prey by weight and had a 25% 


frequency of occurrence. Echiuran worms were also commonly 


encountered at 24% frequency of occurrence and comprised 5% 


of the prey by weight. Other prey with high frequencies of 


occurrence were gammarid amphipods (22%) and cumaceans 


(17%); however, each of these prey taxa modestly accounted 


for less than 1% of the total prey weight. Prey of 


diminishing importance included anemones, bivalves, isopods, 


euphausiids, shrimp, hermit crabs, and sipunculans. 


The chief prey items of Dover sole were polychaetes 


and brittle stars, ranking first and second, respectively 


(Table 55). Gabriel and Pearcy (1981) also found the diet 


of Dover sole off the Oregon coast was primarily composed 


of polychaetes and brittle stars. Similarly, Pearcy and 


Hancock (1978) found polychaetes were the most common prey 


of Dover sole off the Oregon coast. 

 177 

Table 55.--Prey items (expressed in mean percent frequency of occurrence, and mean percent 

 total weight) of Microstomus pacificus (Dover sole) collected in the Gulf of Alaska in 

 2001. 

Prey items Percent frequency Percent weight 

Anthozoa (anemome) 4.00 0.15 

Polychaeta (worm) 26.67 6.87 

Aphroditidae (sea mouse) 1.33 2.11 

Polynoidae (polychaete) 4.00 0.13 

Euphrosinidae 20.00 11.86 

Phyllodocidae (polychaete) 17.33 5.51 

Phyllodoce sp. (polychaete) 1.67 0.22 

Nephtyidae (polychaete) 1.33 0.30 

Arabellidae (polychaete) 1.67 0.56 

Maldanidae (polychaete) 4.00 1.16 

Terebellida (polychaete) 20.00 20.00 

Bivalvia (clam) 8.00 1.02 

Cumacea (cumacean) 17.00 0.62 

Isopoda (isopod) 8.00 0.23 

Gammaridea (amphipod) 21.67 0.74 

Hyperiidea (amphipod) 13.33 1.21 

Caprellidea (amphipod) 5.33 1.02 

Euphausiidae (euphausiid) 8.00 4.60 

Euphausia pacifica (euphausiid) 5.00 0.37 

Thysanoessa sp. (euphausiid) 8.00 2.59 

Thysanoessa inermis (euphausiid) 8.00 1.95 

Caridea (shrimp) 1.33 0.68 

Hippolytidae (shrimp) 2.67 2.31 

Paguridae (hermit crab) 10.00 3.01 

Sipuncula (marine worm) 4.00 1.16 

Echiura (marine worm) 24.00 5.33 

Ophiurida (brittle star) 25.33 17.10 

Ophiuridae (brittle star) 20.00 7.19 
 178 

Table 55.--Continued. 

Total non-empty stomachs = 35 

Total prey number = 334 

Total prey weight = 56.638 g 

Total empty stomachs = 3 

Number of hauls = 5 

Full stomach summary statistics 

Average fork length = 44.38 cm 

Standard deviation of fork length = 1.66 cm 

Minimum fork length = 34 cm 

Maximum fork length = 60 cm 

Average fullness = 3.60 

Standard deviation of fullness = .37 

Minimum fullness = 2 

Maximum fullness = 6 

Empty stomach summary statistics 

Average fork length = 48.67 cm 

Standard deviation of fork length = 10.02 cm 

Minimum fork length = 41 cm 

Maximum fork length = 60 cm 
 179 

SUMMARY 


Important Prey of Groundfish 


A total of 7,899 stomachs from 40 species were 


analyzed to describe the food habits of the major 


groundfish species in the Gulf of Alaska in 1999 and 2001. 


Our analysis emphasized groundfish predation on 


commercially important fish, crab, and shrimp. The 


predator sizes and the number of the stomachs collected for 


each species are summarized in Tables 1 and 2 for 1999 and 


2001, respectively. Although juveniles of some species 


(walleye pollock, Pacific cod, Pacific halibut, and 


arrowtooth flounder) were sampled, the main focus of our 


study was the food habits of adult fish. 


Tables 56 and 57 list the percent by weight of the 


commercially important fish, crab, shrimp, and other major 


prey or prey groups consumed by groundfish in 1999 and 2001, 


respectively. Arrowtooth flounder, Pacific halibut, 


sablefish, Pacific cod, bigmouth sculpin, big skate, and 


Bering skate were the main predators that consumed fish. 


The main predators that consumed Tanner crabs were Pacific 


halibut, Pacific cod, great sculpin, yellow Irish lord, big 


skate, and longnose skate. Flathead sole, Pacific cod, 


spinyhead sculpin, dusky snailfish, longnose skate, 


rougheye rockfish, and sharpchin rockfish, were the primary 

 180 

consumers of pandalid shrimp. Sharpchin rockfish, Atka 


mackerel, Pacific ocean perch, redbanded rockfish, and 


searchers are thought to not have substantial impact on the 


commercially important species in the Gulf of Alaska since 


they feed mainly on zooplankton (primarily euphausiids and 


calanoid copepods). The data in Tables 56 and 57 indicate 


that pollock were the dominant prey fish in both years and 


were consumed predominately by arrowtooth flounder, Pacific 


halibut, sablefish, Pacific cod, and Bering skate. Pollock 


cannibalism, which accounted for less than 1% in 1999 and 


5% in 2001 of the total stomach contents weight, were not 


an important phenomenon in the Gulf of Alaska compared with 


the Bering Sea (Livingston 1991). Other forage fish such 


as Pacific herring, capelin, eulachon, and Pacific sand 


lance can be categorized as the next most important prey 


fishes. Pacific halibut was the main predator of Pacific 


herring in 2001 (2% of the total stomach content weight), 


whereas arrowtooth flounder consumed a relatively large 


amount of capelin (13% by weight) in the same year. Other 


large amounts (9% by weight, respectively) of capelin were 


consumed in 1999 by arrowtooth flounder and pollock. 


Pacific sand lance was consumed by the main piscivorous 


species (arrowtooth flounder, Pacific halibut, sablefish, 


Pacific cod, and big skate). Flatfish consumed by 

 181 

groundfish include arrowtooth flounder, Kamchatka flounder, 


flathead sole, butter sole, rock sole, yellowfin sole, and 


Pacific halibut. Arrowtooth flounder was consumed mostly 


by Pacific halibut, Pacific cod, arrowtooth flounder, and 


bigmouth sculpin. Pacific cod (<2% each) were consumed by 


Pacific halibut and sablefish. Chum salmon (Oncorhynchus 


keta) (1% stomach content weight) were found in Pacific 


halibut stomachs. Sebastes spp. were found in arrowtooth 


flounder, Pacific halibut, and sablefish stomachs. Tanner 


crabs were mainly consumed by Pacific cod, sablefish, and 


Pacific halibut though they were also consumed by bigmouth 


sculpin, longnose sculpin, great sculpin, rougheye rockfish, 


yellowfin sole, and arrowtooth flounder. Tables 56 and 57 


show that many predator species consumed a certain amount 


of cephalopods (squid and octopus) but shortraker rockfish, 


giant grenadier, and sablefish were the main predators of 


the cephalopods. Many predators preyed on pandalid shrimp, 


which includes all the Pandalus and Pandalopsis species. 


The sharpchin rockfish, spinyhead sculpin, dusky snailfish, 


longnose skate, Pacific cod, and rougheye rockfish were the 


primary predators of the pandalids. 

 182 

Table 56.--Percent by weight of the important prey or prey group consumed 


 by the groundfish in the Gulf of Alaska in 1999. AMP, amphipod;


 ATK, Atka mackerel; ATF, arrowtooth flounder; BAS, bathymasterid;


 BMS, bigmouth sculpin; BRI, brittle star; CAL, calanoid; CAP, 


 capelin; CEP, cephalopod; CHA, chaetognath; COD, Pacific cod; COT,


 cottid; EUL, eulachon; EUP, euphausiid; FHS, flathead sole; FOF,


 fish offal; HER, herring; LAR, larvacean; MAW, marine worm; MOL, 


 molluska; MYC, myctophid; MYS, mysid; NRS, northern rock sole;


 OCR, other crabs; OSH, other shrimp; PAG, pagurid; PAH, Pacific 


 halibut; PAN, pandalid; PLK, pollock; POL, polychaete; ROS, rock 


 sole; SAB, sablefish; SAL, salmonid; SAN, Pacific sand lance; SHA, 


 sharpchin rockfish; SHR, shortraker rockfish; SRS, southern rock 


 sole; TAN, Tanner crab; UNF, unknown fish; YFS, yellowfin sole;


 ZOA, zoacid.


Predator


Prey FHS SRS NRS YFS SHR SHA ATK BMS PLK COD SAB PAH ATF 

POL 2 27 39 35 0 0 0 0 1 9 1 <1 <1 

MAW 0 17 0 7 0 0 0 0 0 0 0 0 0 

BRI 0 10 20 2 0 0 0 0 0 0 0 0 0 

MOL 2 8 2 29 0 3 15 0 1 <1 <1 2 <1 

CHA 0 0 0 0 0 0 0 0 1 0 0 0 <1 

LAR 0 0 0 0 0 0 15 0 6 0 0 0 <1 

CAL 0 0 0 0 0 76 <1 0 11 <1 1 0 2 

MYS 0 0 0 0 0 0 0 0 <1 <1 <1 0 <1 

AMP 5 1 3 2 0 2 0 0 1 1 4 0 <1 

EUP 6 <1 0 <1 0 18 66 0 48 6 1 0 23 

OSH 41 2 1 10 0 0 <1 0 4 4 6 5 2 

PAN 41 0 0 0 0 0 0 0 9 14 6 <1 12 

OCR 3 1 3 3 0 0 0 0 <1 16 0 26 <1 

PAG 0 1 0 6 0 1 0 0 <1 6 3 17 0 

TAN 0 0 0 <1 0 0 0 0 0 9 4 <1 <1 

CEP 0 <1 <1 0 0 0 0 0 <1 1 12 <1 <1 

ZOA 0 0 0 0 0 0 0 0 <1 1 0 1 2 

COT 0 13 0 0 0 0 0 0 <1 3 0 <1 <1 

STI 0 0 0 0 0 0 0 0 0 <1 0 1 2 

BAS 0 0 0 0 0 0 0 0 0 4 0 0 1 

EUL 0 0 0 0 0 0 0 0 2 1 0 0 0 

MYC 0 0 0 0 0 0 0 0 0 0 2 0 0 

SAN 0 9 7 0 0 0 0 0 <1 3 0 17 9 

ATF 0 0 0 0 0 0 0 100 0 1 0 4 2 

FHS 0 0 0 0 0 0 0 0 0 <1 0 0 2 

ROS 0 0 0 0 0 0 0 0 0 <1 0 0 0 

CAP 0 0 0 0 0 0 0 0 9 <1 1 6 9 

HER 0 0 0 0 0 0 0 0 0 <1 0 1 <1 

PLK 0 1 0 0 0 0 0 0 <1 11 16 10 19 

FOF 0 0 0 0 0 0 0 0 0 0 27 0 0 

UNF 0 <1 0 0 100 0 <1 0 6 2 9 <1 11 
 183 

Table 57.--Percent by weight of the important prey or prey group consumed 


 by the groundfish in the Gulf of Alaska in 2001. AKS, Alaska skate;


 AMP, amphipod;ATK, Atka mackerel; ATF, arrowtooth flounder; BAS,


 bathymasterid; BES, Bering skate; BGS, big skate; BKE, black eelpout;


 BMS, bigmouth sculpin ;BRI, brittle star; BUT, butter sole; CAL,


 calanoid; CAP, capelin; CEP, cephalopod; CHA, chaetognath; COD, 


 Pacific cod; COT, cottid; CUC, sea cucumber; CUM, cumacean; DES, 


 deepsea sole; DFS, darkfin sculpin; DOG, spiny dogfish; DOV, Dover 


 sole; DSS, dusky snailfish; DUR, dusky rockfish; EUL, eulachon; 


 EUP, euphausiid; FHS, flathead sole; FOF, fish offal; GRS, great 


 sculpin; GTG, giant grenadier; HER, herring; JFH, jellyfish; LAR, 


 larvacean; LNS, longnose skate; MAW, marine worm; MOL, molluska; MYC, 


 myctophid; MYS, mysid; NRQ, northern ronquil; NRS, northern rock sole; 


 OCR, other crabs; OSH, other shrimp; OTF, other fish; PAG, pagurid; 


 PAH, Pacific halibut; PAN, pandalid; PLK, pollock; POL, polychaete;


 POP, Pacific ocean perch; PSF, Pacific sandfish; RBR, redbanded


 rockfish; REX, rex sole; ROS, rock sole; ROU, rougheye rockfish; SAB,


 sablefish; SAL, salmonid; SAN,Pacific sand lance; SER, searcher; SFE,


 shortfin eelpout; SHA, sharpchin rockfish; SHR, shortraker rockfish;


 SHS, spinyhead sculpin; SRS, southern rock sole; SST, shortspine


 thornyhead; STI, stichaeid; TAN, Taner crab; UNF, unknown fish; WTE,


 Wattled eelpout; YFS, yellowfin sole; YIL, yellow Irish lord; ZOA, 


 zoarcid.


Predator


Prey SHA SHS DSS PSF SER POP RBR


JFH 0 0 0 0 3 0 0 

POL 0 0 0 0 3 0 0 

MAW 0 0 0 0 0 0 0 

MOL <1 0 0 0 0 <1 0 

CHA 0 0 0 0 0 1 0 

LAR 0 0 0 0 81 24 0 

CAL <1 0 0 9 0 21 50 

MYS 0 2 0 85 0 <1 0 

AMP 0 <1 0 0 10 5 0 

EUP 45 0 0 0 3 41 49 

OSH 4 26 58 0 0 3 0 

PAN 50 67 42 0 0 3 1 

OCR 0 0 0 0 0 0 0 

PAG 0 0 0 0 0 0 0 

TAN 0 0 0 0 0 0 0 

CEP 0 0 0 0 0 0 0 

ZOA 0 5 0 0 0 0 0 

COT 0 0 0 0 0 0 0 
 184 

Table 57.-- Continued. 

Predator 

Prey DOG BGS BES LNS ATK PLK COD SAB PAH ATF BMS GRS 

JFH 0 0 0 0 0 0 0 3 0 0 0 0 

POL 0 0 0 0 0 <1 7 2 1 1 0 0 

MAW 0 0 0 0 0 <1 <1 <1 <1 0 0 0 

MOL 0 0 0 0 <1 <1 2 3 <1 <1 0 0 

CHA 0 0 0 0 0 <1 0 <1 0 <1 0 0 

LAR 0 0 0 0 15 2 0 <1 0 0 0 0 

CAL 0 0 0 0 1 22 <1 <1 0 <1 0 0 

MYS 0 0 0 0 0 <1 <1 <1 <1 <1 0 0 

AMP 0 0 0 0 <1 3 4 3 <1 <1 0 0 

EUP 7 0 0 0 67 41 5 15 1 14 0 0 

OSH 0 4 33 2 0 4 8 1 1 3 0 0 

PAN 0 0 0 45 0 9 8 3 1 7 0 0 

OCR 0 0 33 0 <1 2 9 <1 17 <1 0 0 

PAG 0 0 0 0 <1 <1 4 1 10 0 9 0 

TAN 0 46 0 45 0 <1 10 <1 6 0 0 100 

CEP 0 0 0 0 0 <1 3 9 3 3 0 0 

BRI 0 0 0 0 0 0 <1 <1 <1 0 0 0 

ZOA 0 0 0 0 0 <1 <1 <1 <1 1 50 0 

COT 0 0 0 0 0 <1 3 <1 2 1 41 0 

STI 0 0 0 0 0 0 1 0 <1 1 0 0 

BAS 0 0 0 0 0 0 <1 0 <1 <1 0 0 

EUL 0 0 0 0 0 0 <1 2 <1 <1 0 0 

MYC 0 0 0 0 0 0 0 0 0 <1 0 0 

SAN 0 49 0 0 15 2 17 5 10 10 0 0 

ATF 0 0 0 0 0 1 0 0 3 1 0 0 

FHS 0 0 0 0 0 <1 0 0 1 0 0 0 

ROS 0 0 0 0 0 0 0 0 1 <1 0 0 

CAP 0 0 0 0 0 1 3 3 4 13 0 0 

HER 0 0 0 0 0 1 1 1 2 <1 0 0 

PLK 0 0 31 0 0 5 6 25 25 37 0 0 

COD 0 0 0 0 0 0 0 2 1 0 0 0 

FOF 93 0 0 0 0 0 0 9 2 <1 0 0 

UNF 0 0 0 0 0 3 1 7 1 3 0 0 

OTF 0 1 0 9 0 <1 2 5 6 4 0 0 
 185 

Table 57.-- Continued. 

Predator 

Prey SHR ROU SST DUR SFE BKE WTE EUL GTG 

JFH 0 0 0 0 0 0 0 0 0 

POL 0 0 2 0 0 0 0 0 0 

MAW 0 0 0 0 0 0 0 0 0 

MOL 0 0 0 0 51 0 0 0 0 

CHA 0 3 1 0 0 0 0 0 0 

LAR 0 0 1 0 0 0 0 2 0 

CAL 0 6 <1 1 0 0 0 0 0 

MYS 1 <1 1 0 7 0 0 3 4 

CUM 0 0 <1 0 30 0 0 2 0 

ISO 0 0 3 0 0 0 0 0 0 

AMP <1 3 1 0 0 0 0 6 0 

EUP <1 22 16 17 1 91 0 67 2 

OSH 44 6 7 0 11 9 8 0 34 

PAN 1 26 3 0 0 0 0 0 4 

OCR 0 0 31 0 0 0 0 0 0 

PAG 0 1 2 0 0 0 0 0 0 

TAN 0 13 0 0 0 0 0 0 0 

CEP 17 8 1 0 0 0 0 0 38 

BRI 0 0 0 0 0 0 0 0 0 

ZOA 0 0 8 0 0 0 92 0 0 

COT 0 0 0 0 0 0 0 0 0 

STI 0 0 0 0 0 0 0 0 0 

BAS 0 0 0 0 0 0 0 0 0 

EUL 0 0 0 0 0 0 0 0 0 

MYC 30 0 4 0 0 0 0 0 0 

SAN 0 0 0 82 0 0 0 0 0 

ATF 0 0 0 0 0 0 0 0 0 

FHS 0 0 0 0 0 0 0 0 0 

ROS 0 0 0 0 0 0 0 0 0 

CAP 0 0 0 0 0 0 0 0 0 

HER 0 0 0 0 0 0 0 0 0 

PLK 0 0 6 0 0 0 0 0 4 

COD 0 0 0 0 0 0 0 0 0 

FOF 0 0 0 0 0 0 0 0 0 

UNF 0 0 0 0 0 0 0 0 0 

OTF <1 1 1 0 0 0 0 16 14 
 186 

Table 57.-- Continued. 

Predator 

Prey FHS SRS NRS REX DOV NRQ DES DFS YFS BUT 

JFH 0 0 0 0 0 0 0 0 0 0 

POL <1 16 13 26 49 86 72 52 4 0 

MAW 0 <1 6 19 6 0 0 0 0 0 

MOL 0 5 6 1 1 0 0 0 0 0 

CHA 0 0 0 0 0 0 0 0 0 0 

LAR 0 0 0 0 0 0 0 0 0 0 

CAL 0 0 0 <1 0 0 0 0 5 0 

MYS <1 0 0 6 0 0 0 1 0 0 

CUM <1 0 0 3 1 14 0 10 91 100 

ISO <1 <1 <1 0 <1 0 0 23 0 0 

AMP 0 7 1 10 3 0 10 10 0 0 

EUP 0 0 <1 14 10 0 0 3 0 0 

OSH 1 0 <1 1 3 0 0 0 0 0 

PAN 64 0 0 1 0 0 0 0 0 0 

OCR 1 24 0 0 0 0 0 0 0 0 

PAG 0 3 1 <1 3 0 0 0 0 0 

TAN 0 0 0 0 0 0 0 0 0 0 

CEP 0 0 0 0 0 0 18 0 0 0 

BRI 10 35 29 0 24 0 0 0 0 0 

CUC 0 2 23 0 0 0 0 0 0 0 

ZOA 0 0 0 0 0 0 0 0 0 0 

COT 0 0 0 0 0 0 0 0 0 0 

STI 6 2 0 0 0 0 0 0 0 0 

BAS 0 0 0 0 0 0 0 0 0 0 

EUL 0 0 0 0 0 0 0 0 0 0 

MYC 0 0 0 0 0 0 0 0 0 0 

SAN 0 0 19 0 0 0 0 0 0 0 

ATF 0 0 0 0 0 0 0 0 0 0 

FHS 0 0 0 0 0 0 0 0 0 0 

ROS 0 0 0 0 0 0 0 0 0 0 

CAP 0 0 0 0 0 0 0 0 0 0 

HER 0 0 0 0 0 0 0 0 0 0 

PLK 0 0 0 14 0 0 0 0 0 0 

COD 0 0 0 0 0 0 0 0 0 0 

FOF 17 0 0 0 0 0 0 0 0 0 

UNF 0 0 0 5 0 0 0 0 0 0 
 187 

ACKNOWLEDGEMENTS 


We would like to thank Thomas Wilderbuer for reviewing 


the manuscript. Thanks also go to Morgan Busby, Debbie 


Blood, and Jay Orr for identification of juvenile fish and 


larvae. We also want to thank James Lee and Gary Duker for 


editing the manuscript. 


 189 

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RECENT TECHNICAL MEMORANDUMS
 

Copies of this and other NOAA Technical Memorandums are available from the 

National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22167 

(web site: www.ntis.gov). Paper and microfiche copies vary in price. 

AFSC163	 EILER, J. H., T. R. SPENCER, J. J. PELLA, and M. M. MASUDA. 2006. Stock composition, run timing, 

and movement patterns of chinook salmon returning to the Yukon River basin in 2003, 104 p. NTIS 

No. PB2006-108429. 

162	 IGNELL, S. E., B. L. WING, B. D. EBBERTS, and M. M. MASUDA. 2006. Abundance and spatial pattern 

of salps within the North Pacific Subarctic Frontal Zone, August 1991, 26 p. NTIS No. PB2006-108423. 

161	 ANGLISS, R. P., and R. OUTLAW. 2005. Alaska marine mammal stock assessments, 2005, 247 p. NTIS 

number pending. 

160	 SEPEZ, J. A., B. D. TILT, C. L. PACKAGE, H. M. LAZARUS, and I. VACCARO. 2005. Community 

profiles for North Pacific fisheries - Alaska, 552 p. NTIS No. PB2006-108282. 

159	 ETNIER, M. A., and C. W. FOWLER. 2005. Comparison of size selectivity between marine mammals 

and commercial fisheries with recommendations for restructuring management policies, 274 p. NTIS 

No. PB2006-102327. 

158 	 LANG, G. M., P. A. LIVINGSTON, and K. A. DODD, 2005. Groundfish food habits and predation on 

commercially important prey species in the eastern Bering Sea from 1997 through 2001, 222 p. NTIS 

number pending. 

157	 JOHNSON, S. W., A. DARCIE NEFF, and J. F. THEDINGA. 2005. An atlas on the distribution and 

habitat of common fishes in shallow nearshore waters of southeastern Alaska, 89 p. NTIS number 

pending. 

156	 HOFF, G. R., and L. L. BRITT. 2005. Results of the 2004 Eastern Bering Sea upper continental slope 

survey of groundfish and invertebrate resources, 276 p. NTIS No. PB2006-100504. 

155	 YANG, M-S., K. AYDIN, A. GRIEG, G. LANG, and P. LIVINGSTON. 2005. Historical review of capelin 

(Mallotus villosus) consumption in the Gulf of Alaska and Eastern Bering Sea, 89 p. NTIS No. 

PB2005-110464. 

154	 HOLLAND D. S. 2005. Economic analysis of protection of essential fish habitat in Alaskan fisheries: 

An analysis of research needs, 35 p. NTIS No. PB2005-110129. 

153	 FRITZ, L. W., and C. STINCHCOMB. 2005. Aerial, ship, and land-based surveys of Steller sea lions 

(Eumetopias jubatus) in the western stock in Alaska, June and July 2003 and 2004, 56 p. NTIS 

number PB2005-108287. 

152	 AMES, R. T., G. H. WILLIAMS, and S. M. FITZGERALD. 2005. Using digital video monitoring systems 

in fisheries: Application for monitoring compliance of seabird avoidance devices and seabird mortality 

in Pacific halibut longline fisheries, 93 p. NTIS No. PB2005-107312. 

151	 TESTA, J. W. (editor). 2005. Fur seal investigations, 2002-2003, 72 p. NTIS No. PB2005-104811. 

150 	 GULLAND, F. M. D., H. PÉREZ-CORTÉS M., J. URBÁN R., L. ROJAS-BRACHO, G. YLITALO, J. 

WEIR, S. A. NORMAN, M. M. MUTO, D. J. RUGH, C. KREUDER, and T. ROWLES. 2005. Eastern 

North Pacific gray whale (Eschrichtius robustus) unusual mortality event, 1999-2000: A compilation, 

33 p. NTIS No. PB2005-105795.