NOAA Technical Memorandum NMFS-AFSC-60

Diets of the Important Groundfishes

in the Aleutian islands in Summer 1991

by

M-S, Yang

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

February 1996
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 new NMFS-NWFSC series will be used by

the Northwest Fisheries Science Center.

This document should be cited as follows:

Yang, M-S. 1996. Diets of the important groundfishes in the Aleutian

Islands in summer 1991. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-AFSC-60, 105 p.

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

the National Marine Fisheries Service, NOAA.
NOAA Technical Memorandum NMFS-AFSC-60

Diets of the Important Groundfishes

in the Aleutian Islands in Summer 1991

by

Mei-Sun Yang

Alaska Fisheries Science Center

7600 Sand Point Way N.E., BIN C-15700

Seattle, WA 981150070

U.S. DEPARTMENT OF COMMERCE

Ronald H. Brown, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Under Secretary and Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Administrator for Fisheries

February 1996
This document is available to the public through:

National Technical Information Set-vice

U.S. Department of Commerce

5265 Port Royal Road

Springfield, VA 22161
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

The diets of commercially important groundfish species in

the waters surrounding the Aleutian Islands during the summer of

1991 were studied. Important prey types, predator-prey size

relationships, and prey distribution are discussed in detail.
V

CONTENTS

Page

ABSTRACT ..................................................

INTRODUCTION......... .....................................

METHODS ...................................................

RESULTS

Walleye pollock....... ...................................

Pacific cod .............................................

Arrowtooth flounder .....................................

 Pacific halibut .........................................

Atka mackerel ...........................................

Greenland turbot ........................................

Shortspine thornyhead ...................................

Northern rockfish .......................................

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

Rougheye rockfish .......................................

Shortraker rockfish .....................................

SUMMARY ...................................................

ACKNOWLEDGMENTS ...........................................

iii

1

1

5

14

31

40

57

63

67

72

77

82

86

90

100

CITATIONS................................................. 101
INTRODUCTION

The estimated biomass of groundfish resources in the

Aleutian Islands region from long. 170° 30' E to 170° W, and the

southern Bering Sea from long. 170° W to 165° W is about 2.0

million metric tons (t) (Harrison 1993). The objective of this

study was to describe the food habits of key predators in the 

waters surrounding the Aleutian Islands and in the southern

Bering Sea. Eleven commercially important groundfish species

were studied: Pacific cod, Gadus macroceohu; walleye pollock,

Theragra chalcogramma; Pacific halibut, Higooalossus stenolepis;

arrowtooth flounder, Atheresthes stomias; Greenland turbot,

Reinhardtius hippoglossoides; Atka mackerel, Pleurogrammus

monopterygius Pacific ocean perch,

rockfish, Sebastes polyspinis;

Sebastes alutua; northern

rockfish, Sebastes

aleutianus; shortraker rockfish,

rougheye

Sebastes borealis; and

shortspine thornyhead, sebastolobus alascanus.

METHODS

Study Area

From July to September 1991, the Resource Assessment and

Conservation Engineering (RACE) Division at the Alaska Fisheries

Science Center, Seattle, Washington, conducted a groundfish

resources survey in' the Aleutian Islands region. This survey

area (Fig. 1) covered the southern Bering Sea from long 165°W to

170° W and the Aleutian Islands waters from long. 170° W to 170°

30' E. The Resource Ecology and Fishery Management (REFM)

Division's Trophic Interactions Program collected fish stomach

samples during this survey.

Sample Collection

Fish stomach samples were collected by scientists aboard the

charter vessel Green Hope from July to September in 1991. 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 (vessel, cruise, haul number, specimen number) was also put

in the bag. All of the samples collected were then preserved in

buckets containing a 10% buffered formalin solution. When the

samples arrived at the laboratory, they were transferred into a

70% ethanol solution before the stomach contents were analyzed.

Stomach Contents Analysis

In the laboratory, the stomach contents were first blotted

with a paper towel and the wet weight was then recorded to the

nearest one-tenth of a gram. After obtaining the total weight

 for a stomach's contents, the contents were placed in a petri

dish and examined under the microscope. Each prey item was

classified to the lowest practical taxonomic level. The numbers

of non-commercially important prey were not counted; instead the

percent volume of these prey items was 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 (from REFM

Aging Task). Standard lengths of prey fish, carapace widths (CW)

of Tanner crabs, (Chionoecetes spp.), and Korean horse-hair

crabs (Eriamacru isenbeckii) were also recorded.

Data Analysis

The general diet of each species was summarized by showing

the overall percent frequency of occurrence, and the percent of

the total weight of each prey item found-in the stomach. Change

in diet by predator size in terms of percent by weight of main

prey items was identified by dividing predator size into 10 cm FL

groups. The prey size frequency data of the commercially

important fish and crabs were also summarized by different

predator size groups.

The geographic distribution of the important prey consumed

(expressed as percent by weight of the total stomach contents

weight in each haul) by the predators were also shown. The
3

important prey found in this study include walleye pollock, Atka

mackerel, capelin (Mallotus villosus), myctophid, Tanner crabs,

and Korean horse-hair crabs.

5

WALLEYE POLLOCK

The projected 1995 exploitable biomass of walleye pollock

(Theragra chalcogramma for the Aleutian Islands region was

189,000 t (NPFMC 1994). Along with Atka mackerel, Pacific ocean

perch, northern rockfish, and Pacific cod, walleye pollock was

one of the five most abundant species in the Aleutian Islands

region in 1991 (Harrison 1993). An earlier study suggested that

euphausiids were the most frequently occurring prey of pollock in

the Aleutian Islands area (Simenstad et al. 1977). Other prey

items included shrimp, amphipods, cephalopods, myctophids,

bathylagids, and Sebastes spp.

RESULTS

General Diet

A total of 546 walleye pollock stomachs were analyzed, of

which 540 (99%) contained food. Pollock size ranged from 16 to

68 cm FL with a mean and standard deviation (SD) of 45.1 ± 10.1

cm. The average depth of the 44 haul locations where pollock

stomachs were collected was 198 ± 78 m with a range from 81 to

397 m. Table l-l lists the main prey found in the pollock

stomachs, the frequency of occurrence of prey (%), and the

percentage of prey weight to the total food weight. The data

presented in Table l-l suggests that pollock feed mainly on

euphausiids (43% by weight). Though calanoid copepods, mysids,

amphipods, and shrimp were frequently found in stomachs, they

were relatively less important as pollock as food. Zoea and

megalops of Chionoecetes spp. were found in pollock stomachs, but

they comprised less than 1% by weight of the total stomach

contents. Table l-l lists the diversity of prey fish found in

pollock stomachs. Myctophids (37% by weight of the total stomach

contents) were the most important prey fish of walleye pollock in

the Aleutian Islands region. Some commercially important fish,

such as Pacific cod, arrowtooth flounder, and Kamchatka flounder

(Atheresthes evermanni) were found. Capelin, eulachon

(T_haleichthys pacificus), deepsea smelts (Bathylagidae), and

Pacific sand lance (Ammodytes hexapterus) were also considered to

be important prey.
6

Variation of Diet Based on Predator Size

Figure l-i illustrates the main prey items of walleye

pollock by predator length. Calanoid copepods were mainly

consumed by pollock less than 20 cm FL. Euphausiids comprised the

largest portion of food of pollock between 20 and 49 cm FL. 

Myctophids were the most important food for pollock larger than

50 cm FL -- making up about 50% of the diet for this group.

Cannibalism of pollock was not observed in this study.

Size of Prey Fish

The number, mean, and SD of standard length of the prey fish

for pollock are listed in Table l-2. Since a large number of,

myctophids were consumed, the myctophid length data were further

divided into two predator size groups (< 40 cm and < 40 cm FL)

for analysis. Figure l-2 shows that walleye pollock less than

40 cm FL consumed mainly smaller sized (< 70 mm SL) myctophids

whereas larger pollock <40 cm FL) consumed many larger

70 mm SL) myctophids.

Geographic Distributions of Prey

Figure l-3 shows the percentage by weight of myctophids

consumed by walleye pollock in different locations. The figure

illustrates that myctophids were consumed on both sides of the

Aleutian Islands chain primarily in waters of bottom depths

greater than 150 m. Myctophids made up more than 50% of the

stomach contents weight for walleye pollock collected in these

areas.

DISCUSSION

The diet of walleye pollock from this study was compared to

data on pollock diet from the Gulf of Alaska (Yang 1993) and the

eastern Bering Sea (Livingston 1991). The weight (%) of the

major prey categories for pollock from three study areas are

compared in Table l-3. These data show that the diet similarity

(49%) between Aleutian Islands region and the Gulf of Alaska was

higher than the other areas. This was primarily caused by the

high consumption <39% of the total) of euphausiids in these two
7

areas. In the Bering Sea, pollock (41% by weight) was the main

food of pollock, whereas pollock comprised only 2% of the diet

the Gulf of Alaska, and no pollock cannibalism was observed in

the Aleutian Islands area. In the Gulf of Alaska, capelin

comprised the highest percentage (13%) by weight of prey fish

in

consumed by pollock, whereas myctophids (comprised 37% by weight)

were the main prey fish found in pollock stomachs in the Aleutian

Islands area. Another difference was that pollock consumed more

pandalid shrimp in the Gulf of Alaska (19%) than in the eastern

Bering Sea (4%) and Aleutian Islands area (2%).

Simenstad et al. (1977) found that euphausiids were the most

important prey (87% by weight) of walleye pollock in the Amchitka

Island area. They also found myctophids, Sebastes spp., shrimp,

squid, and octopus in the pollock stomachs.
8

Table l-l. --Main prey items (expressed in frequency of

occurrence (%) and percentage of total weight

consumed) of Theragra chalcogramma (walleye pollock)

collected in the Aleutian Islands area in 1991.

Prey Name % Freq. occur. % Total weight
9

Table 1-2.--Mean, standard deviation (SD), and range of

standard length of the miscellaneous, prey fish

consumed by walleye pollock in the Aleutian

Islands area in 1991.

Prey name No. Mean (mm) SD (mm) Range (mm)

Arrowtooth flounder 4 34.7

Bathylagid 4 88.7

Capelin 2 95.0

Cattid 7 30.1

Kamchatka flounder 1 25.0

Myctophid 165 71.9

Pacific cod 1 58.0

Pacific sand lance 5 53.0

Searcher 1 30.0

Snailfish 6 18.0

Stichaeid 2 33.5

Viperfish 2 107.5

5.2 30-42

49.2 45-145

7.0 90-100

6.8 23-41

22.1 22-110

4.5 50-60

6.0 12-27

10.6 26-41

10.6 100-115
10

Table l-3. --Percent by weight of the major prey categories of

walleye pollock in the Aleutian Islands area (AI)

compared to the eastern Bering Sea (EBS) (from

Livingston 1991), and Gulf of Alaska (GOA)

(from Yang 1993). "-" indicates < 1.

Prey name AI GOA EBS

% similarity between AI and EBS: 38

% similarity between AI and GOA: 49

% similarity between EBS and GOA: 40
11

Figure l-l.-- Main food items of walleye pollock,

by predator size, in the Aleutian

Islands area in 1991. N = sample size.
1 2

Figure 1-2.-Size frequency distributions of myctophid

consumed by two size groups (< 40 cm FL

and ? ?40 cm FL) of walleye pollock in the

Aleutian Islands area in 1991.
Figure 1-3.-- Geographic distribution of myctophids consumed by walleye pollock in the Aleutian Islands area in 1991.
Pacific cod (Gaus marocenhalus) is one of the five most

abundant species (in biomass) in the Aleutian Islands area

(Harrison 1993). The projected exploitable biomass of Pacific

cod in 1995 was 220,000 t (Thompson 1994). Pacific cod have a

high variety of prey in their diets (including many commercially

important fish and crabs) since they feed both on the bottom and

in the water column.

RESULTS

General Diets

A total of 659 Pacific cod stomachs were analyzed, of which

651 contained food. Pacific cod lengths ranged from 15 to

109 cm FL with a mean and SD of 56.0 cm and; 17.0 cm,

respectively. The average depth of the 69 haul locations was 142

± 55 m with a range from 58 to 348 m. Pacific cod, an

opportunistic feeder,, ate many different invertebrates and

various fish (33% and 67% of the total stomach content weight,

respectively). Squid comprised the highest proportion (9% of the

total stomach content weight) of the invertebrates consumed.

Shrimp (hippolytid, pandalid, and crangonid) also comprised about

9% of the total stomach content weight. Pacific cod also

consumed Korean horse-hair crab (Erimacrus isenbeckii), Tanner

crabs (Chionoecetes bairdi), and other crabs (Table 2-l). The

crabs consumed by Pacific cod also made up about 9% of the total

stomach content weight. Polychaetes, mysids, gammarid amphipods,

and euphausiids were also found frequently in the stomachs but

they were not very important food of Pacific cod in terms of the 

percentage of the total stomach content weight. Atka mackerel

and walleye pollock were the two main fish species consumed by

Pacific cod. The two species comprised 27% and 17% of the total

stomach content weight, respectively. Other commercially

important prey fish include juvenile Pacific cod, greenlings

(hexagrammid), Sebastes spp., sablefish (Anoplopoma fimbria), rex

sole (Errex zachirus), flathead sole (Hippoglossus elassodon),

rock sole, (Pleuronectes bilineatus, and Pacific halibut.

Pacific cod also consumed many non-commercially important prey
15

fish, such as zoarcids, macrourids, cottids, agonids,

cyclopterids, bathymasterids, Pacific sand lance, and stichaeids.

Variation of Diet Based on Predator Size

Figure 2-l shows that Pacific cod consumption of fish

increased with increasing body size, especially for cod greater

than or equal to 70 cm FL. Fish comprised about 75% of the total

stomach contents in this larger size group. This group of

Pacific cod ?? ?70 cm FL) consumed large amounts of Atka mackerel

and walleye pollock (31% and 23% by weight, respectively). No

walleye pollock were found in the stomachs of Pacific cod smaller

than 60 cm FL. Other fish species made up between 10% and 30% of

the diet by weight throughout all the different size groups of

cod. Cod between 20 and 70 cm FL consumed some shrimp (between

17% and 39% of the diet). Tanner crabs ?? ?14%) were consumed

mainly by Pacific cod between 20 and 70 cm FL, The smallest size

group (< 20 cm FL) of cod ate primarily large amounts (70%) of

amphipods. 

Size of Important Prey

The commercially important prey consumed by Pacific cod were

analyzed by two predator size groups (< 60 cm, and ? ?60 cm FL).

No walleye pollock were found in the stomachs of Pacific cod less

than 60 cm FL. Pacific cod longer or equal to 60 cm FL consumed

many age 3+ pollock (approximately >300 mm SL) and some age 0 to

age 2 pollock (Fig. 2-2). The mean SL of pollock consumed by

Pacific cod was 334.4 ± 131.3 mm with a range from 65 to 518 mm

SL. Figure 2-3 (right) illustrates that Atka mackerel were

primarily consumed by larger Pacific cod( ? ?60 cm FL). The mean

standard length of all Atka mackerel consumed by Pacific cod was

226.2 ± 57.2 mm with a range from 107 to 330 mm SL. The mean SL

of the myctophids consumed was 71.8 ± 21.8 mm with a range from

28 to 105 mm SL. Figure 2-3 (left) also shows that myctophids

were mainly consumed by larger Pacific cod (3-60 cm FL). Larger

cod fed on larger prey. In general, larger Pacific cod ?? ?60 cm

FL) fed on larger Tanner crabs than smaller cod (< 60 cm FL)

(Fig. 2-4, left). The average carapace width (CW) of the Tanner

crabs consumed was 19.3 ? ?9.9 mm with a range of 5 to 53 mm.

Most of the Tanner crabs measured from Pacific cod stomach

contents were age-l crab (9-34 mm CW). Pacific cod also consumed

a fair number of Korean horse-hair crab (Fig. 2-4, right). The
16

average carapace width of the Korean horse-hair crab was 27.6 ±

10.8 mm with a range of 14 to 57 mm. Only one Pacific halibut

(27 mm SL) was observed in our Pacific cod samples. One flathead

sole (195 mm SL), one rex sole (260 mm SL), two juvenile cod (123

and 146 mm SL), six Sebastes spp. (125-260 mm SL), and two rock

sole (62 and 260 mm SL) were also observed in the samples.

Miscellaneous prey fish data are listed in Table 2-2.

Geographic Distributions of Prey

Figures 2-5 to 2-9 'illustrate the geographic distributions

of the important prey (percent by weight) for Pacific cod in each

haul where stomach samples were collected. The high percentage of

Atka mackerel in the diet of Pacific cod was observed mainly in

the western part of the Aleutian Islands area (Fig. 2-5).

Walleye pollock were consumed by Pacific cod at many locations in

the Aleutian Islands area (Fig. 2-6), the percent (> 75%)

consumption peaked in the Agattu Island area. Figure 2-7 shows

the geographic distribution of the Tanner crabs consumed by

Pacific cod. The figure illustrates that Tanner crab consumption

was low ?? ?25%), except in the Unalaska Island area (66%).

Consumption of Korean horse-hair crab by Pacific cod was mainly

located in the western part (west of Atka Island) of the Aleutian

Islands chain, and the highest percent (> 75%) consumption was

found in the Atka Island area. Myctophids were consumed by

Pacific cod mainly in the Yunaska Island area, and the percent by

weight was low (about 30% at two haul locations) (Fig. 2-9).

DISCUSSION

Simenstad et al. (1977) found that Pacific cod in the

Amchitka Island area fed mainly on fish (including cottids and

Pacific sand lance). Shrimp, Korean horse-hair crab, squid, and

octopus also occurred in their samples frequently. In our study,

cottids were also found frequently (27% frequency of occurrence)

in the stomachs of Pacific cod.

Table 2-3 lists the percentage by weight of the major prey

categories of Pacific cod from the Aleutian Islands area (this

study), Gulf of Alaska (Yang 1993), and the eastern Bering Sea

(Livingston 1991). Based on the data in Table 2-3, the percent

similarity of the diets between the three areas was about 30%.
17

Two major differences were observed. First, Atka mackerel was

the most important prey (27% by weight) of Pacific cod in the

Aleutian Islands area, whereas no Atka mackerel were found in

samples from the Gulf of Alaska or eastern Bering Sea. Second,

walleye pollock were prey of Pacific cod in all three areas,

however, the amounts differed. In the eastern Bering Sea,

pollock were the most important prey of Pacific cod, making up

40% of the total stomach contents weight. On the other hand,

pollock comprised only 17% and 8% of the total stomach content

weight of Pacific cod in the Aleutian Islands area and Gulf of

Alaska, respectively. The high percentage (27%) of Atka mackerel

and relatively low percentage (17%) of pollock consumed by

Pacific cod in the Aleutian Islands area can be attributed to the

higher biomass of Atka mackerel (about 700,000 t) compared to

that of pollock (about 200,000 t) in the Aleutian Islands area

(Harrison 1993).
18

Table 2-1.- -Prey items (expressed in frequency of

occurrence (%), and percentage of total weight)

of Gadus macrocephalus (Pacific cod) collected

in the Aleutian Islands area in 1991.

Prey Name

% Freq. % Total

occur. weight

Polychaeta (unidentified)

Gastropoda (unidentified)

Bivalvia (clam)

Cephalopoda (unidentified).,

Teuthoidea (squid unidentified)

Octopoda (unidentified)

Calanoida (copepod unidentified)

Mysidacea (mysid unidentified)

Isopoda (isopod)

Gammaridea (amphipod)

Hyperiid (amphipod)

Euphausiacea (unidentified)

Reptantia (crab)

Caridea (unidentified)

Hippolytidae (unidentified)

Pandalidae (unidentified)

Crangonidae (unidentified)

Paguridae (hermit crab)

Lithodidae (king crab)

lithodes hispidus (fuzzy crab)

Lopholithodes foraminatus (box crab)

Placetron wosnessenski (scale crab)

Lithodes couesi (couesi king crab)

Munida quadrispina (pinch bug)

Majidae (unidentified)

Chionoecetes sp. (unidentified)

ecetes bairdi (Tanner crab)

Frimacrus isenbeckii (crab)

Pinnotheridae (pea crab)

Sipuncula (peanut worm)

Raja spp.

Teleostei (unidentified fish)

Non-gadoid fish remains

Clupea pallasi (Pacific herring)

Chauliodus macouni, (Pacific viperfish)

Myctophid (lantern fish)

Gadidae (unidentified gadid)

Gadus macrocephalus (Pacific cod)

Theragra chalcosramma (walleye pollock)

Zoarcidae (unidentified eelpout)
Table 2-l.--Continued.

19
20

Table 2-2.--Mean, standard deviation (SD), and range of the

standard length of the miscellaneous prey

fish consumed by Pacific cod in the Aleutian

Islands area in 1991.
21

Table 2-3. --Percent by weight of the major prey categories of

Pacific cod in the Aleutian Islands area (AI)

compared to the eastern Bering Sea, (EBS) (from

Livingston 1991), and Gulf of Alaska (GOA)

(from Yang 1993). "-I" indicates <l.
22

Figure 2-1.-Variation in the main food items of Pacific cod,

by predator size, in the Aleutian Islands area

in 1991. N = sample size.
23

Walleye pollock

Figure 2-2.-Size frequency distributions of walleye pollock consumed

by Pacific cod ??? ?cm in the Aleutian Islands area in 1991.
24

Figure 2-3.--Size frequency distributions of Atka mackerel and

myctophid consumed by two size groups (< 60 cm FL

and ? ?60 cm FL) of Pacific cod in the Aleutian Islands

area in 1991.
25

Figure 2-4 Size frequency distributions of Tanner crab and Korean

horse-hair crab consumed by two size groups (< 60 cm FL

and ? ?60 cm FL) of Pacific cod in the Aleutian Islands area

in 1991.



Figure 2-8-- Geographic distribution of Korean horse-hair crabs consumed by Pacific cod in the Aleutian Islands area in 1991
a
31

ARROWTOOTH FLOUNDER

The projected 1995 exploitable biomass of arrowtooth

flounder (Atheresthes stomias) in the Aleutian Islands area was

43,500 t (Wilderbuer and Sample 1994). This resource has been

in good condition because of minimal exploitation and steady

increases in biomass throughout the 1980s and into the 1990s.

Arrowtooth flounder is a large flatfish with a symmetrical

mouth and sharp teeth that feeds on fish like walleye pollock

and capelin, as well as shrimp and other crustaceans (Yang

1993). Therefore, it is important to study its food habits and

its impact on the important prey. Kamchatka flounder, a very

similar congeneric species to the arrowtooth flounder in

morphology and biology, is also distributed in the Aleutian

Islands area. Because of the high similarity of the diets of

arrowtooth flounder and Kamchatka flounder (Yang and Livingston

1986), data of these two species from the Aleutian Islands area

were pooled together for analysis,

RESULTS

General Diets

A total of 339 arrowtooth flounder stomachs were analyzed.

Of this total, 194 (57%) contained food. Arrowtooth flounder

sizes ranged from 17 to 73 cm FL with a mean and SD of 38.3 and

± 9.9 cm, respectively. The average depth of the 47 haul

locations where samples were collected was 149 ± 60 m with a

range from 59 to 331 m.

Table 3-l lists the food items found in arrowtooth

flounder stomachs. Even though many invertebrate species like

euphausiids (34.8% by frequency of occurrence), pandalid

shrimp, squid, mysids, and amphipods were found in the diet, of

arrowtooth flounder, they comprised only 10% of the total

stomach contents weight. The remaining 90% of stomach content

weight was made up of fish. Atka mackerel comprised 44% by

weight of the total stomach contents. Walleye pollock occurred

more frequently in the diet, but comprised only 11% by weight.

Myctophids, the third most important prey of arrowtooth

flounder, comprised about 7% of the total stomach contents
32

weight. Other fish consumed by arrowtooth flounder included

Pacific herring (Clupea pallasi), Pacific cod, sablefish,

Pacific halibut, Pacific sand lance, snailfish (Cyclopteridae),

searcher (Bathymaster spp.), prickleback (Stichaeidae),

rockfish (Scorpaenidae), greenling (Hexagrammidae), and some

cottids.

Variation of Diet Based on Predator Size

Figure 3-l illustrates the percentage by weight of the

main prey items for different arrowtooth flounder size groups.

Atka mackerel were the predominant prey fish (>50%) for

arrowtooth flounder greater than or equal to 50 cm whereas

walleye pollock were the predominate prey in the diets of the

arrowtooth flounder between 40 and 49 cm long. Figure 3-l also

shows that fish from the miscellaneous category were important

to the diet of arrowtooth flounder less than 40 cm long.

These miscellaneous fish included stichaeid, cottid, Pacific

sand lance, searcher, rockfish, and some flatfish. Amphipods,

euphausiids, and shrimp were important food for smaller sized

(< 40 cm) arrowtooth flounder.

Sizes of the Prey Fish

Table 3-2 illustrates the standard length, standard

deviation, and size range of the miscellaneous prey fish

consumed by arrowtooth flounder. The four Atka mackerel

observed in my samples for arrowtooth flounder were between 210

and 330 mm SL. Walleye pollock consumed were between 60 and 190

mm SL. Because of the small numbers of prey fish consumed by

arrowtooth flounder, prey fish data were not analyzed by size

groups.

Geographic Distributions of the Prey

Figure 3-2 shows the geographic distribution of the

walleye pollock consumed by arrowtooth flounder. My sampling

shows that walleye pollock were consumed by arrowtooth flounder

at a limited number of locations in the Aleutian Islands area.

Only around Adak Island did pollock comprise more than 25% of

the stomach content weight of arrowtooth flounder. Figure 3-3

shows that high percentages (>75%) of Atka mackerel consumed by

arrowtooth flounder were mainly distributed in the western
33

Aleutian Islands between Attu Island, Agattu Island, and Kiska

Island. There was also a high percentage of Atka mackerel

consumed by arrowtooth flounder on the west side of Unalaska

Island.

DISCUSSION

Simenstad et al. (1977) found that shrimp and cottids were

the main diet of arrowtooth flounder in the Amchitka Island

area. However, their results were derived from a small sample.

In this study, I compared the diets of arrowtooth flounder from

the Aleutian Islands area to those from the Gulf of Alaska

(Yang 1993) and the eastern Bering Sea (Yang 1991). Table 3-3

lists the percentage by weight of the major prey categories of

arrowtooth flounder from these three study areas. It

illustrates that pollock were the main food of arrowtooth

flounder in the eastern Bering Sea (56%) and in the Gulf of

Alaska (66%), but not in the Aleutian Islands area (11%). On

the other hand, Atka mackerel were the-main food of arrowtooth

flounder in the Aleutian Islands area but were not found in the

diet of fish collected in the eastern Bering Sea and the Gulf

of Alaska areas. Data in Table 3-3 also indicates that fish in

the miscellaneous category comprised a higher percentage (15%),

in the stomach contents of arrowtooth flounder in the Aleutian

Islands area than in the other two areas. Another difference

is that myctophids were only found in the arrowtooth flounder

stomachs in the Aleutian Islands area (6.5%). Though the

composition of prey fish and their percentages were different

in the arrowtooth flounder stomachs, the overall degree of

piscivory (about 90%) was relatively constant across the three

areas .
34

Table 3-1 .--Prey items (expressed frequency of occurrence (%),

and percentage of total weight consumed) of

Atheresthes stomias (arrowtooth flounder) collected

in the Aleutian Islands area in 1991.
35

Table 3-2.--Mean, standard deviation (SD), and range of the

standard length of the miscellaneous prey fish

consumed by arrowtooth flounder in the Aleutian

Islands area in 1991.
36

Table 3-3. --Percentage by weight of the major prey categories

of arrowtooth flounder in the Aleutian Islands

area (AI) compared to the eastern Bering Sea (EBS)

(from Yang 1991), and Gulf of Alaska (GOA)

(from Yang 1993). "-" indicates cl.

Prey name AI GOA EBS

Cephalopod

Euphausiid

Pandalid

Pacific herring

Zoarcid

Capelin

Atka mackerel

Pollock

Myctophid

Miscellaneous fish

Unidentified fish

2

3

4

9

1

8

1

66

0

5

0

56

0

8

11
37


40

PACIFIC HALIBUT

The exploitable biomass of Pacific halibut (Hippoglossus

stenolenis) was estimated at 17,400 t round weight for the

eastern Bering Sea and Aleutian Islands areas (IPHC 1994). The

commercial catches in these areas totaled 3,800 t round weight

(head off weight). Since Pacific halibut feed on fish, crab,

and squid, it is important to study their food habits and their

impact on other commercially important species in the Aleutian

Islands area.

RESULTS

General Diets

A total of 202 Pacific halibut stomachs were analyzed, of

which 180 (89%) contained food. The size range of Pacific

halibut was between 28 and 116 cm FL with a mean and SD of 61.8

± 17.7 cm. The average depth of the 39 haul locations was 114

± 46 m with a range from 37 to 229 m. Table 4-l lists the

frequency of occurrence (%), and the percent by weight of the

prey found in Pacific halibut stomachs. By-weight, 55% of the

total stomach contents were fish, with the remainder made up by

invertebrates. Walleye pollock (19% by weight) was the most

important prey item. Atka mackerel was another important prey

of Pacific halibut; comprising 12% of the total stomach content

weight. Other commercially important fish consumed by Pacific

halibut include Pacific herring, Pacific cod, flathead sole,

sablefish, and rockfish Sebastes spp.). Pacific halibut also

consumed fishery discards (processed fish carcasses), but they

comprised less than 1% by weight of the total stomach content.

Many non-commercially important fish (capelin, cottids,

agonids, cyclopterids, and bathymasterids) were also consumed

by Pacific halibut; however, they comprised only a small

percent of the total stomach contents weight.

Squid and octopus were the most important invertebrate

prey of Pacific halibut; comprising 17% and 10% of the total

stomach contents weight, respectively. Chionoecetes bairdi was

the most frequently occurring prey (24%) of Pacific halibut and

comprised 7% of the total stomach contents weight. Less

important invertebrate' prey included lyre crab (Hyas spp.)
41

(2.4%), hermit crab (1.3%), and decorator crab (Oregonia spp.)

(0.6%). The other invertebrates consumed (polychaetes,

gastropods, clams, euphausiids, shrimp, and other crustaceans)

were considered to be less important as food for Pacific

halibut.

Variation of Diet Based on Predator Size

The diet of Pacific halibut varied greatly by predator

size (Fig. 4-l). Walleye pollock and Atka mackerel were

primarily consumed by Pacific halibut greater than or equal to

70 cm FL. Capehin were important food for halibut 40 to 60 cm

FL, whereas miscellaneous prey fish (e.g., rockfish, flatfish,

Pacific herring, and sablefish) were consumed by all size

groups. Tanner crabs were the primary food of Pacific halibut

between 50 and 70 cm FL. Hermit crabs, Korean horse-hair

crabs, lyre crabs, and decorator crabs were important food

items for Pacific halibut less than 60 cm FL. Hermit crabs.

were especially important (55% by weight) for fish less than

40 cm FL. Cephalopods were important to the diet of halibut

greater than 60 cm FL.

Sizes of the Commercially Important Prey

For analysis, prey length data of Pacific halibut were

divided into two predator size groups (c 80 cm and ? ?80 cm FL)

(Figs. 4-2 to 4-4). Figure 4-2 (left) shows that small Pacific

halibut (< 80 cm FL) consumed more walleye pollock than large

halibut ?? ?80 cm FL). The sizes of the walleye pollock

consumed by these two size groups were similar (between 200 and

450 mm SL) except that the smaller Pacific halibut also

consumed age-0 (< 140 mm SL) pollock. The mean standard

length and standard deviation of pollock consumed by Pacific

halibut was 211.8 ± 134.9 mm with a range from 41 to 453 mm SL.

Figure 4-2 (right) shows that large Pacific halibut

consumed larger Atka mackerel. The mean SL of the Atka

mackerel consumed by Pacific halibut was 260.1 ± 56.3 mm with a

range from 171 to 360 mm.

The sizes of capelin consumed by the two size groups of

Pacific halibut were similar (Fig. 4-3, right). The mean SL of

capelin consumed was 100.3 ± 11.5 mm with a range from 79 to

121 mm. Figure 4-3 (left) also shows that sizes of the

myctophids consumed by the two size groups of Pacific halibut
42

were similar. The mean SL of the myctophid consumed was

47.9 ± 11.3 mm with a range from 34 to 68 mm.

Figure 4-4 shows that large numbers of Tanner crabs were

consumed by the small Pacific halibut (< 80 cm FL); whereas

only a few Tanner crabs were consumed by large Pacific halibut

?? ?80 cm FL). The Tanner crabs consumed were mainly age-l

(9-34 mm CW) crabs and a few age-2 and older crabs. The mean

CW of the Tanner crabs consumed was 19.1 ± 4.9 mm with a range

from 5 to 51 mm.

In one sample, a Pacific halibut had consumed a 280 mm SL

Pacific herring. Other prey fish were also reported for

halibut in the Aleutian Islands area. The length data of these

prey fish are listed in Table 4-2.

Geographic Distributions of the Prey

The geographic distributions of important prey consumed by

Pacific halibut are shown in Figures 4-5 to 4-10. Figure 4-5

illustrates that walleye pollock were consumed by Pacific

halibut at many of the survey stations, and the high

percentages (> 75%) of walleye pollock consumed were observed

in the Unalaska and Akutan Islands areas. High percentages of

Atka mackerel by weight were also found in the Agattu and

Tanaga Islands area. The highest percentage of capelin

consumption was primarily in the Unalaska area (Fig. 4-7).

Based on my sample, Tanner crabs were- consumed mainly in Umnak

Island and Atka Island areas (Fig. 4-8). Figure 4-9

illustrates that while the Korean horse-hair crabs were

consumed by Pacific halibut at many stations, the amounts

(percent by weight) were not high. High percentages by weight

of myctophids were found in the Yunaska Island area though

myctophids were not found in Pacific halibut stomachs at many

stations (Fig. 4-10).

DISCUSSION

Simenstad et al. (1977) found that,

area, Pacific halibut fed principally on

sculpins, rock sole, Pacific sand lance,

in the Amchitka Island

walleye pollock,

sturgeon poacher

(Podothecus acipenserinus.) and secondarily on squid, octopus,

and crabs. The diet composition of Pacific halibut from this
43

study was similar to that found by Simenstad et al. (1977)

except that Atka mackerel were not observed in their samples.

Many earlier studies (Novikov 1968; Simenstad et al. 1977;

Best and Pierre 1986; Livingston et al. 1993; Yang 1993) show a

trend of changing diet composition of Pacific halibut by size.

This trend of predator size to diet preference was also

indicated in this study. When Pacific halibut are young, they

feed mainly on crustaceans. As they grow and increase in size,

they feed primarily on fish, squid, and octopus.

In this study, I compared the major prey categories of the

Pacific halibut in the Aleutian Islands area to those from the

Gulf of Alaska (Yang 1993). Table 4-3 indicates that walleye

pollock was the dominant prey (57% by weight) of Pacific

halibut in the Gulf of Alaska area; however, walleye pollock

comprised only 19% of the total stomach contents weight in the

Aleutian Islands area. Atka mackerel and cephalopods were also

important food (12% and 27%, respectively) of Pacific halibut

in the Aleutian Islands area, whereas none of these were

important food in the Gulf of Alaska area. Most of diet

differences can be attributed to increased cephalopod and Atka

mackerel consumption and lower pollock consumption in the

Aleutian Islands area compared with the Gulf of Alaska. Less

than one-half of the diet in Aleutian Islands was fish, whereas

about 64% of Gulf of Alaska diet was fish.
44

Table 4-1 .--Prey items (expressed in frequency of occurrence (%),

and percentage of total weight) of Pacific halibut

(Hippoglossus stenolepis) collected in the Aleutian

Islands area in 1991.
45

Table 4-2.- -Mean standard length, standard deviation (SD),

and size range of the miscellaneous prey fish

consumed by Pacific halibut in the Aleutian

Islands area in 1991.
Table 4-3. --Percentage by weight of the major prey categories of

Pacific halibut in the Aleutian Islands area (AI)

compared to the Gulf of Alaska (GOA)

(from Yang 1993).

48

Figure 4-2.--Size frequency distributions of walleye pollock and Atka

mackerel consumed by two size groups (< 80 cm FL and

? ?80 cm FL) of Pacific halibut in the Aleutian Islands area

in 1991.
49

Figure 4-3.--Size frequency distributions of capelin and myctophid

consumed by two size groups (< 80 cm FL and ? ?80 cm FL)

of Pacific halibut in the Aleutian Islands area in 1991.
50

Figure 4-4.--Size frequency distributions of Tanner crab consumed by

two size groups (< 80 cm FL and ? ?80 cm FL) of Pacific

halibut in the Aleutian Islands area in 1991.
Figure 4-5.-- Geographic distribution of walleye pollock consumed by Pacific halibut in the Aleutian Islands area in 1991.
Figure 4-6.-- Geographic distribution of Atka mackerel consumed by Pacific halibut in the Aleutian Islands area in 1991.
Figure 4-7.-- Geographic distribution of capelin consumed by Pacific halibut in the Aleutian Islands area in 1991.
Figure 4-8-- Geographic distribution of Tanner crabs consumed by Pacific halibut in the Aleutian Islands area in 1991.

Figure 4-10.-- Geographic distribution of myctophids consumed by Pacific halibut in the Aleutian Islands area in 1991.
57

ATKA MACKEREL

Atka mackerel (Pleurogrammus monopterygius) ranked first

in terms of biomass for the groundfish complex in the Aleutian

Islands area in 1991 (Harrison 1993). Based on the stock

synthesis (SS) model, the estimated exploitable biomass for

1995 estimated from the stock synthesis (SS) model was

832,000 t (Lowe 1994). The catch of Atka mackerel has been

increasing from 24,000 t in 1991 to 68,000 t in 1994 (Lowe

1994). Because of the abundance and the commercial value of

Atka mackerel, it is important to study its food habits and the

possible impact to the ecosystem in the Aleutian Islands area.

RESULTS

General Diet

A total of 238 Atka mackerel stomachs were analyzed, of

which 231 (97%) contained food. Atka mackerel ranged in size

from 22 to 44 cm FL with a mean and SD of 33.5 cm and ± 4.5 cm,

respectively. The average depth of the 21 haul locations

(Fig. 5-l) was 127.4 ± 37.9 m with a range from 66 to 181 m.

Table 5-l lists the frequency of occurrence (%) and the

percentage by weight of the prey found in Atka mackerel

stomachs. More than 90% of the total stomach contents weight

was made up of invertebrates and less than 10% was fish.

Euphausiids (mainly Thysanoessa inermis and Thysanoessa rachii)

were the most important prey item. The two species comprised

55% of the total stomach contents. Calanoid copepods were

another important prey of Atka mackerel, comprising 17% of the

total stomach content weight. Larvaceans and hyperiid

amphipods occurred frequently (81% and 68%, respectively), but

the two categories comprised less than 6% of the total stomach

contents weight, respectively. Squid was another invertebrate

prey of Atka mackerel; they comprised 8% of the total stomach

contents weight.

Atka mackerel eggs comprised 3% of the total stomach

contents weight and occurred in 9% of the Atka mackerel

stomachs analyzed. Walleye pollock were the second most

important prey fish of Atka mackerel; they comprised about 2%
58

of the total stomach contents weight. Myctophids, bathylagids,

zoarcids, cottids, stichaeids, and pleuronectids were also

found in the Atka mackerel stomachs. However, each of the

categories comprised less than 1% of the total stomach contents

weight.

Variations of Diet Based on Predator Size

Figure 5-2 illustrates the percentage by weight of the

main prey items for different Atka mackerel size groups.

Calanoid copepods (42% by weight) and larvaceans (22% by

weight) were the most important food of the smallest (< 25 cm

FL ) size groups of Atka mackerel. Euphausiids (69% by weight)

were the most important prey of Atka mackerel between 26 and 35

cm FL. The largest (> 35 cm FL) Atka mackerel also consumed a

fair amount of euphausiids (21% by weight) in addition to

cephalopods (29%). Cannibalism (preying on their own eggs).

occurred mainly in this size group (> 35 cm FL) of Atka

mackerel. Eggs comprised 13% of the total stomach contents

weight of this size group.

The size of walleye pollock consumed by Atka mackerel

ranged from 49 to 63 mm SL with a mean and SD of 56.2 ± 4.8 mm.

The cottids consumed by Atka mackerel ranged from 12 to 21 mm 

SL with mean and SD of 15.9 ± 3.1 mm. Other fish consumed by

Atka mackerel included one bathylagid (11 mm SL), one zoarcid

(61.4 mm SL), one myctophid (59 mm SL), and one stichaeid (29

mm SL).

DISCUSSION

Simenstad et al. (1977) found that planktonic crustaceans,

hyperiid amphipods, calanoid copepods, and oikopleura

(larvaceans) occurred frequently in the Atka mackerel stomachs

collected from the Amchitka Island area. In the current study,

euphausiids were the most important food (55% by weight). This

is contrary to Simenstad et al. (1977) findings that

euphausiids occurred in only 1% of Atka mackerel stomachs.

The guarding of eggs by males is a characteristic of the

reproductive behavior of Atka mackerel (Zolotov and Tokranov

1991). Many studies (Zolotov and Tokranov 1991, Zolotov and

Medveditsyna 1978, Takemura and Yamane 1953) have shown that
59

Atka mackerel eat their own eggs. We compared the diets of

males and females to see if there was any diet differences that

could be linked to the egg-guarding behavior of males. Table

5-l indicates that the diet of male Atka mackerel was comprised

of 62% euphausiids, 18% calanoid copepods, 6% larvaceans, 4%

Atka mackerel eggs, and 2% walleye pollock. Similarly, the

diet of female Atka mackerel was comprised of 48% euphausiids,

16% calanoid copepods, 6% larvaceans, 3% Atka mackerel eggs

and 2% walleye pollock. The main differences were that male

Atka mackerel consumed more euphausiids than the females

(62% vs. 48%) and female Atka mackerel consumed more squid than

the males (15% vs. 1%). Based on this study, it appears that

male and female Atka mackerel do not feed differently despite

the egg-guarding behavior of the males.
60

Table 5-1 .--Main prey items (expressed in frequency of occurrence (%FO),

and percent total weight (%WT)) of Atka mackerel

(Pleurogrammus monopterygius) collected in the Aleutian

Islands area in 1991.

62

Figure 5-2.-Variation in the main food items of Atka mackerel,

by predator size, in the Aleutian Islands area in 1991.

N = sample size.
63

GREENLAND TURBOT

The total estimated biomass of Greenland turbot

alossoldes) in the Aleutian Islands area was

12,072 t in 1991 (Harrison 1993). The catch of the Greenland

turbot in the Aleutian Islands in 1994 was 2,933 t (Ianelli

et al. 1994). Earlier studies on the diet of Greenland turbot

(Mito 1974, Smith et al. 197-8, Yang and Livingston 1988) have

shown that Greenland turbot are primarily piscivorous, and

walleye pollock is the most important prey of Greenland turbot

in the eastern Bering Sea. Therefore, it is important to study

the diet of the Greenland turbot in the Aleutian Islands area.

To avoid confusion with the Pacific halibut (Hippoglossus

stenoleois), we use the "official" market name (Greenland

turbot) instead of Greenland halibut which is the common name

used by the American Fisheries Society (AFS 1991). 

RESULTS

A total of 44 Greenland turbot stomachs were analyzed, of

which 25 (57%) contained food. Greenland turbot sizes ranged

 from 58 to 100 cm FL with a mean and standard deviation of

67.6 ± 7.7 cm. Figure 6-l illustrates the haul locations for

the collected stomach samples of the Greenland turbot in the

Aleutian Islands area in 1991. The average depth of the 5

haul locations was 332.7 ± 87.5 m with a range from 181 to

390 m.

Table 6-l lists the frequency of occurrence (%) and the

percentage by total weight of Greenland turbot prey. Fish

comprised about 50% by weight of the diet of Greenland turbot.

Myctophids were the most important prey fish of Greenland

turbot. This group comprised 36% of the frequency of

occurrence and 29% of the total stomach contents weight.

Bathylagids were the second most important prey fish. This

latter category comprised 13% of the total stomach contents

weight. Although walleye pollock were found in the stomachs of

Greenland turbot, they comprised only 1.4% of the total stomach

contents weight. Squid were the most important invertebrate

prey. They comprised 46% of the total stomach contents weight.

Polychaetes and octopus were also consumed by Greenland turbot;
however, they

total diet.

Diet was

64

comprised very low percentages by weight of the

not analyzed by different predator size groups

 because all turbot collected were larger than 55 cm and the

total sample size was small. However, some prey fish length

data were collected during the analysis. The length of

measurable myctophids consumed by Greenland turbot had a mean

and SD of 101.2 ± 5.8 mm SL with a range between 92 and 108 mm.

The average SL of the four bathylagids collected from stomach

contents was 124.7 ± 17.1 mm with a range of 102 to 143 mm.

One measurable Pacific viperfish (Chauliodus macouni) (140 mm

SL) was also identified during the analysis.

DISCUSSION

Yang and Livingston (1988) found that walleye pollock was

the most important prey of Greenland turbot in the eastern

Bering Sea. However, in this study, walleye pollock was not an

important prey. Instead, myctophids and squid were the most

important prey for Greenland turbot in the Aleutian Islands

area. This difference in diet composition can be related to

the fact thatwalleye pollock abundance is so much higher in

the Bering Sea than in the Aleutian Islands area. Though the

compositions of the prey fish in the diet of Greenland turbot

were different in these two areas, the total percentages of the

fish and cephalopods consumed were similar in this study (50%

fish and 50% cepahlopods) and for the same depth area (200-399

m) in the Bering Sea (49% fish and 50% cephalopods) (Yang and

Livingston 1988).

Because of the small sample size (n = 25) in this study,

diet variation between different size groups of Greenland

turbot were not analyzed.
65

Table 6-1.- -Prey items (expressed in frequency of occurrence (%),

and percentage of total weight) of Greenland turbot

(Reinhardtius hippoglossoides) collected in the

Aleutian Islands area in 1991.

67

SHORTSPINE THORNYHEAD

Shortspine thornyheads (Sebastolobus alascanus) account for

the bulk of the "other rockfish" catch in the Aleutian Islands

area (Ito 1994). The "other rockfish" category includes all

species of Sebastes and Sebastolobus other than the Pacific ocean

perch (Sebastes alutus) complex. The estimate of the exploitable

biomass for "other rockfish" for 1995 was 15,450 t in the

Aleutian Islands area (Ito 1994). In the past, thornyheads were

not the primary target of the rockfish fleet. Today, thornyheads

are one of the most commercially valuable rockfish species

(Dawson 1991).

RESULTS

A total of 67 shortspine thornyhead stomachs were analyzed,

of which 44 (66%) contained food. Shortspine thornyhead sizes

ranged from 17 to 52 cm FL with a mean and SD of 33.4 ± 7.8 cm.

Figure 7-l shows the haul locations for the collected stomach

samples of the shortspine thornyhead in the Aleutian Islands in

1991. The average depth of the 8 haul locations was 350.4 ± 43.3

m with a range from 271 to 410 m.

Table 7-l lists the frequency of occurrence (%) and the

percentage by total weight of the prey items of shortspine

thornyhead. Fish made up about 65% by weight of the diet of

shortspine thornyhead. Cottids were the most important prey fish

of shortspine thornyhead, Comprising 51% of the total stomach

contents weight. Other prey fish included unidentified rockfish,

cyclopterids, and other unidentified fish remains. Pandalid

shrimp, at 18% of the total stomach contents weight, were the

most important invertebrate prey. Shortspine thornyhead also

consumed Korean horse-hair crab (8% by weight), deep sea king

crab (Lithodes couesi) (< 1%) and other crustaceans (< 5%).

Figure 7-2 illustrates the variation of the main food items

of different size groups of shortspine thornyhead. The smallest

size group ( 25 cm FL) consumed high percentages (66% of the

total stomach contents weight) of shrimp and euphausiids (13%)

but no fish. Medium-sized (26-35 cm FL) shortspine thornyhead

consumed a high percentage (88% by weight) of cottids. The

largest size group of shortspine thornyhead also consumed a high
68

percentage (47% by weight) of cottids plus some miscellaneous

fish, shrimp, and Korean horse-hair crab (35 mm CW). The average

standard length of the cottids consumed in this study was

71 ± 23.8 mm with a range from 27 to 92 mm SL.

DISCUSSION

Yang (1993) found that shortspine thornyhead consumed large

amounts (67% of the total stomach contents weight) of shrimp

(mainly pandalids) in the Gulf of Alaska area. In this study,

cottids were the most important prey of the shortspine thornyhead

in the Aleutian Islands area; they comprised 51% of the total

stomach contents weight. Shrimp (mainly pandalids) were also

important; however, they comprised only 23% of the total stomach

contents weight of the shortspine thornyhead. Differences in

abundance of the main prey between the two areas might be the

main reason for the observed diet differences. Predator size

might be another reason for the difference since the average

shortspine thornyhead in the Aleutian Islands area was larger

than that in the Gulf of Alaska (33.4 cm vs 29.7 cm FL).

Yang (1993) has already described that shortspine thornyhead

mainly feeds on epibenthic shrimp and fish. Yang (1993)

suggested that this species' elongated body, relatively large

terminal mouth, and gill raker structure all contribute to the

diet differences between shortspine thornyhead and other rockfish

species. The present study supports Yang's (1993) observations

except that the analysis found more fish than shrimp in the

stomachs of shortspine thornyhead in the Aleutian Islands area.
69

Table 7-1 .--Prey items (expressed in frequency of occurrence (%),

and percentage of total weight) of shortspine thornyhead

(Sebastolobus alascanus collected in the Aleutian Islands

area in 1991.

71
72

NORTHERN ROCKFISH

Northern rockfish (Sebastes polyspinis) were distributed

mainly in the western Aleutian Islands area and on the Petrel

Bank (Harrison 1993). It was the fourth most abundant groundfish

encountered during the 1991 Aleutian Islands groundfish survey

(Harrison 1993). Because of its abundance, it is considered

important to study the food habits of the northern rockfish in

the Aleutian Islands area.

RESULTS

A total of 153 northern rockfish stomachs were analyzed, of

which 115 (75%) contained food. Northern rockfish lengths ranged

from 14 to 45 cm FL with a mean and standard deviation of

28.6 ± 5.5 cm. Figure 8-l shows the haul locations where stomach

samples of northern rockfish were collected in the Aleutian

Islands area in 1991. The average depth of the 18 haul locations

was 152 ± 43.5 m with a range from 77 to 236 m.

Table 8-l lists the frequency of occurrence (%), and the

percentage by total weight of the prey items of northern

rockfish. The analysis indicated that northern rockfish were

mainly planktivorous. Euphausiids were the most important prey of

the northern rockfish, comprising 50% of the total stomach

contents weight. Calanoid copepods occurred 'the most frequently

(71%) in northern rockfish stomachs, but they comprised only 17%

of the total stomach contents weight. Other food included

 polychaetes, pteropods, amphipods, shrimp, pagurid crabs, and

arrow worms. One myctophid (52 mm SL consumed by one 34 cm FL

fish) was the only prey fish found in northern rockfish stomachs;

they comprised only 1% of the total stomach contents weight.

Calanoid copepods (65% by weight) were the most important

food of the smaller-sized group ?? ?25 cm FL) of northern rockfish

whereas euphausiids (57%) were the main food of the larger-sized

fish (> 25 cm FL) (Fig. 8-2).
73

DISCUSSION

Earlier studies in the Gulf of Alaska (Yang 1993), and

Bering Sea (Skalkin 1964, Mito 1974) showed a similar diet for

northern rockfish: euphausiids, calanoid copepods, arrow worms,

and hermit crabs. All these studies indicate that northern

rockfish are planktivorous.
74

Table 8-1 .--Prey items (expressed in percent frequency of occurrence (%),

and percentage of total weight) of northern rockfish

(Sebastes polyspinsis) collected in the Aleutian Islands area

in 1991.

76
77

PACIFIC OCEAN PERCH

The estimated 1995 exploitable biomass of Pacific ocean

perch (Sebastes alutus) in the Aleutian Islands area was

252,000 t (NPFMC 1994). It ranked second in mean catch per unit

effort (CPUE) among the most abundant groundfish species in the

1991 Aleutian Islands groundfish survey (Harrison 1993). The

objective of this study was to understand the food habits of

Pacific ocean perch and their relation to other marine fishes in

the Aleutian Islands area.

RESULTS

A total of 266 Pacific ocean perch stomachs were analyzed,

of which 128 were empty and 138 (52%) contained food. Pacific

ocean perch length ranged from 10 to 45 cm FL with a mean and SD

of 30.4 ± 7.4 cm. The average depth of the 16 haul locations was

203.7 ± 54.4 m with a range from 77 to 331 m.

Table 9-l lists the frequency of occurrence (%), and the

percentage of total weight for the prey items of Pacific ocean

perch. Euphausiids were the most important prey of Pacific ocean

perch in terms of frequency of occurrence (75%) and percentage of

total weight (51%). Calanoid copepods, amphipods, and

polychaetes were also found frequently, however, they comprised

low percentages by weight of the total diet of Pacific ocean

perch. Myctophids were the most important prey fish consumed by

Pacific ocean perch; they comprised 34% of the total stomach

contents weight. The myctophids consumed by Pacific ocean perch

had a mean standard length and SD of 58.0 ± 28.2 mm with a range

from 24 to 97 mm SL. A high (>75%) percentage of myctophids were

found in the stomachs of Pacific ocean perch from the Seguam

Island area (Fig. 9-l).

Figure 9-2 illustrates the variation in diet between the

different size groups of Pacific ocean perch. The smaller

?? ?25 cm FL) Pacific ocean perch fed mainly on calanoid copepods

and euphausiids, whereas both the medium-sized (26-35 cm FL) and

largest (> 35 cm FL) fish consumed high percentages of

euphausiids (65% and 35%, respectively). This figure also shows

that large amounts (55% by weight) of myctophids were consumed by

fish from the largest size group.
78

DISCUSSION

Simenstad et al. (1977) found that, in the Amchitka Island

area, Pacific ocean perch fed mainly on euphausiids (86% by

weight) and hyperiid amphipods (6% by weight) with incidental

exploitation of mesopelagic fishes like myctophids. The present

study generally agrees with the earlier findings except that a

much higher percentage (34%) of myctophids were consumed by

Pacific ocean perch in the present study. Because of the wide

distributional range (from southern California to the Bering Sea)

of the Pacific ocean perch, the diets of this species have been

documented for many other areas (Yang [1993] in the Gulf of

Alaska; Skalkin [1964] and Mito [1974] in the Bering Sea; and

Brodeur and Pearcy [1984] along the West Coast). The results

from the previous studies were similar to the results of this

study. That is, Pacific ocean perch are mainly planktivorous;

the smaller fish eat a higher percentage of calanoid copepods and

the larger fish eat a higher percentage (usually more than 85%)

of euphausiids and some shrimp. The main difference between the

earlier studies and this study is that a high percentage of

myctophids (34% by weight) was found in the diet of Pacific ocean

perch collected for this study.
79

Table 9-l.--Prey items (expressed in frequency of occurrence (%),

and percentage of total weight) of Pacific ocean perch

(Sebastes aleutus) collected in the Aleutian Islands area

in 1991.

81
82

ROUGHEYE ROCKFISH

Rougheye rockfish (Sebastes aleutianus) has been managed

with the shortraker rockfish as a deep-water species in the

Pacific ocean perch complex in the Aleutian Islands area since

1991. The projected exploitable biomass of rougheye rockfish in

the Aleutian Islands area in 1995 was 25,278 t (Ito and Ianelli

1994).

RESULTS

A total of 58 rougheye rockfish stomachs were analyzed, of

which only 11 (19%) contained food. The average size of the

rougheye rockfish was 38.7 cm FL with a SD of 5.8 cm. Fish size

ranged from 24 to 48 cm FL. The average depth of the 11 haul

locations (Fig. 10-l) was 297 ± 102 m with a range from 152 to

410 m.

Table 10-l shows the frequency of occurrence (%) and

percentage by weight of the prey items of rougheye rockfish. It

illustrates that shrimp, including pandalids and hippolytids,

were the primary invertebrate prey of the rougheye rockfish.

Snailfish were the most important fish prey; they comprised 44%

of the stomach contents weight. Rougheye rockfish also consumed

some myctophids (4% by weight), and non-gadoid fish remains (3%

by weight). Other food items included polychaetes, amphipods,

mysids, euphausiids, and isopods.

Because of the small sample size of rougheye rockfish

stomachs, an analysis of diet variation between different size

groups was not available.

DISCUSSION

Some earlier studies on rougheye rockfish show similar

results to this study. Yang (1993) found that shrimp (pandalids,

hippolytids, crangonids) comprised more than 50% of the total

stomach contents weight for rougheye rockfish collected in Gulf

of Alaska. Feder (1980) found that shrimp occurred in 75% of the

rougheye rockfish stomachs collected in the southeastern Gulf of
83

Alaska. Both authors also reported that snailfish, squid, and

mysids were part of the rougheye rockfish diet.
Table 10-l .--Prey items (expressed in frequency of occurrence (%),

and percentage of total weight) of rougheye rockfish

(Sebastes aleutianus) collected in the Aleutian Islands

area in 1991.

86

SHORTRAKER ROCKFISH

Shortraker rockfish (Sebastes borealis) had an exploitable

biomass of 19,694 t in the Aleutian Islands area in 1991 (Ito and

Ianelli 1994). Because of their special morphological

characteristics (large mouth, short gill rakers, and low gill

raker number), they are considered to be a potential predator of

fish, cephalopods, and other commercially important species.

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

shortraker rockfish.

RESULTS

A total of 33 shortraker rockfish stomachs were analyzed, of

which 16 were empty and 17 (52%) contained food. The average

size of the shortraker rockfish was 43.2 cm FL with a SD of

7.6 cm. Fish length ranged between 33 and 67 cm FL. The average

depth of the 7 haul locations (Fig. 11-l) was 385 ± 39 m with-a

range from 331 to 456 m.

Table 11-l lists the frequency of occurrence (%), and the

percentage by weight of the prey items found in the stomachs of

shortraker rockfish. Shrimp (including hippolytids and pandalids)

were the most important food of shortraker rockfish in terms of

frequency of occurrence and percentage of the total stomach

contents weight. Fish prey comprised 37% of the total stomach

contents weight, of which myctophids and cottids comprised 15%

and 19%, respectively. The samples revealed one myctophid

(96 mm SL) that had been consumed by a 39 cm FL shortraker

rockfish. Two cottids (39 mm and 92 mm SL) were consumed by

shortraker 45 cm and 40 cm FL, respectively. One shortraker

rockfish also consumed a Korean horse-hair crab (44 mm CW).

Another important shortraker rockfish prey were isopods; they

comprised 16% of the total stomach contents weight although their

percent frequency of occurrence (6%) was low.
87

DISCUSSION

It is difficult to collect stomach samples of shortraker

rockfish since many fish brought up in bottom trawl samples had

already regurgitated. An earlier food habits study of shortraker

rockfish (Yang 1993) shows that this fish fed mainly on squid and

myctophids in the Gulf of Alaska. This study also indicates that

myctophids were important food of shortraker rockfish in the

Aleutian Islands area. However, the sample sizes for all of these

studies were small.
Table 11-1 .--Prey items (expressed in frequency of occurrence (%),

and percentage of total weight) of shortraker rockfish

(Sebastes borelais) collected in the Aleutian Islands

area in 1991.

SUMMAR Y

A total of 2,606 stomachs collected from 11 species were

analyzed to describe the food habits of the major groundfish

species in the Aleutian Islands area. The analysis emphasized

predation on commercially important fish, crab, and shrimp. The

predator sizes and the number of the stomachs collected for each

species are summarized in Table 1. Although juveniles of some

species (e.g., walleye pollock, Pacific cod, Pacific halibut, and

arrowtooth flounder) were sampled, the main focus was on the food

habits of the adult fish.

Table 2 lists the percent by weight of the important prey or

prey groups consumed by groundfish. The analysis revealed that

arrowtooth flounder, Pacific halibut, Pacific cod, Greenland

turbot, and pollock were primarily fish eaters. In the present

study, the main predators to feed on Tanner crabs were Pacific

halibut and Pacific cod. Shortspine thornyhead, rougheye

rockfish, and shortraker rockfish were the main consumers of

pandalid shrimp. Atka mackerel, Pacific ocean perch, northern,

rockfish, and walleye pollock were the main consumers of

euphausiids. Atka mackerel, Pacific ocean perch, northern perch

were also the main calanoid copepod eaters. The main cephalopod

eaters were the Greenland turbot and Pacific halibut.

The data in Table 2 indicates that Atka mackerel were the

dominant prey fish and were consumed mainly by arrowtooth

flounder (44%), Pacific halibut (12%), and Pacific cod (27%).

Pollock was another important prey and was consumed mainly by

Pacific halibut (19%), Pacific cod (17%), and arrowtooth flounder

(13%). In the Aleutian Islands area, myctophids were important

food for many fish. Even though they did not comprise a high

percentage of the total stomach contents weight of arrowtooth

flounder (7%), and Pacific cod (3%), myctophids were important

food of many other fish (Greenland turbot, 28%; walleye pollock,

37%; shortraker rockfish, 15%; and Pacific ocean perch, 34%).

Cottids were found in the diet of many species; however, the

dominant consumer appeared to be the shortspine thornyhead (51%)

and shortraker rockfish (19%). The flatfish consumed by the

groundfish include arrowtooth flounder, flathead sole, Kamchatka

flounder, rock sole, rex sole, and Pacific halibut. Each of

these species comprised less than 5% of the stomach contents

weight (Table 2). Pacific sand lance were consumed by the main

predator species (arrowtooth flounder, Pacific halibut, Pacific
91

cod, and pollock) but comprised less than 1% of the stomach

content weight of each species. Pacific cod (1% each) were

consumed by Pacific halibut and Pacific cod. The commercially

important Tanner crabs were mainly consumed by Pacific halibut

and Pacific cod (7% and 2% of the total stomach contents weight,

respectively), though they were also consumed by walleye pollock

(<l%) and Atka mackerel (<1%). Table 2 indicates that almost all

predator species consumed a certain amount of cephalopods (squid

and octopus), of which Greenland turbot (50%), Pacific halibut

(27%), and Pacific cod (12%) were the three main predators of the

cephalopods. Shrimp (mainly pandalids, hippolytids, and

crangonids) were mainly consumed by rougheye rockfish (45%),

shortraker rockfish (32%), shortspine thornyhead (23%), and

Pacific cod (10%). The main euphausiids feeders in the Aleutian

Islands were Atka mackerel (50%), Pacific ocean perch (51%),

northern rockfish (50%), and walleye pollock (43%). Calanoid

copepods were mainly consumed by Atka mackerel (17%), northern

rockfish (17%), and Pacific ocean perch (7%).

By using the proportions of the prey items in the stomachs

(values in Table 2), I calculated the Schoener's (1970) index to

show the dietoverlap between groundfish species in the Aleutian

Islands (Fig. 1). Schoener's index (C,) is calculated as

where Px,i and Py,i are the proportions by weight of prey i in the

diets of species x and y, respectively.

The upper diagonal section of Figure 1 shows the Schoener's

indices (percentage) between different species. For example, the

value 40 in column 3 and row 2 means the diet overlap between

arrowtooth flounder (ATF) and Pacific halibut (PH) was 40% in

term of Schoener's index. The lower diagonal section of

Figure 1 shows the diet overlap between species by categorizing

the Schoener's indices into low (<30%), medium (30-55%), and high

(>55%) values. These values are denoted as blank cells

(for <30% overlap), gray cells (for 30-55% overlap) and black

cells (for >55% overlap). For example, in column 2, it shows

that arrowtooth flounder has high diet overlap (black cell) with

Pacific cod, medium diet overlap (gray cell) with Pacific halibut

and low diet overlap (blank cells) -with all other species in this

study. Overall, Figure 1 shows that Pacific cod had high (>55%),
92

dietary overlap with Pacific halibut and arrowtooth flounder

since they fed mainly on Atka mackerel, pollock, and cephalopods.

High dietary overlap values (85%) also occurred between walleye

pollock and Pacific ocean perch because they all consumed large

amounts of myctophids and euphausiids. Another high dietary

overlap was found between Atka mackerel, northern rockfish, and

Pacific ocean perch since they were mainly zooplankton eaters;

they all consumed large amounts of eupahausiids and calanoid

copepods.

Table 3 lists the size of the commercially important prey

consumed by each predator species. The details of the prey size

of each of the predators were presented in the different sections

of this publication which give species descriptions. This

summary attempts to compare the prey size of the same prey

species consumed by different predators.

Table 3 indicates that the length of consumed pollock varies

from species to species. The average length

(334 ± 131 mm SL) of the prey pollock consumed by Pacific cod was

the highest, whereas arrowtooth flounder consumed smaller prey

pollock (107 ± 58 mm). The mean length of Atka mackerel consumed

by different predators ranged from 226 to 260 mm SL. The size of

the flat-head sole varied from 195 mm SL consumed by Pacific cod

to 205 ± 49 mm consumed by Pacific halibut. Larvae arrowtooth

flounder (35 ± 5 mm SL) were found in walleye pollock diet,

whereas larger-sized arrowtooth flounder

(200 ± 74 mm SL) were consumed by Pacific halibut. Prey Pacific

cod included one 58 mm juvenile consumed by pollock,, 135 ± 12 mm

consumed through cannibalism, and one 230 mm adult consumed by

the Pacific halibut. The mean size of Pacific sand lance

consumed varied from 53 ± 5 mm SL consumed by pollock, to

126 ± 14 mm SL consumed by Pacific halibut, to 160 ± 32 mm SL

consumed by Pacific cod. The mean length of myctophid ranged

from 48 ± 11 mm (consumed by Pacific halibut) to 101 ± 6 mm

(consumed by Greenland turbot). The mean carapace widths of the

Tanner crabs consumed by Pacific halibut was 19 ± 5 mm. Korean

horse-hair crabs consumed by Pacific halibut had a mean and SD of

28 ± 9 mm. One 35 mm Korean horse-hair crab was also found in

shortspine thornyhead stomach.
93

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

Aleutian Islands in 1991. F, stomachs with food;

E, empty stomachs; T, total; SD, standard deviation.
94
95

Table 3. --Standard length (mm) of the prey fish and the carapace

width (mm) of the prey crabs consumed by groundfish in

the Aleutian Islands in 1991. "*" indicates no data.

ATF, arrowtooth flounder; ATK, Atka mackerel; BAT,

bathylagid; CAP, capelin; COD, Pacificcod; COT,

cottid; FHS, flathead sole; GT, Greenland turbot; KAM,

Kamchatka flounder; KHC, Korean horse-hair crab; HER,

herring; MYC, myctophid; NOR, northern rockfish; PH,

Pacific halibut; PLK, walleye pollock; POA, poacher;

POP, Pacific ocean perch; RAT, rattail; REX, rex

sole; RF, rockfish; ROU, rougheye rockfish; RS, rock

sole; SAB, sablefish; SAN, Pacific sand lance; SEA,

searcher; SHR, shortraker rockfish; SNA, snailfish;

SST, shortspine thornyhead; STI, stichaeid; TAN,

Tanner crab; VIP, Pacific viperfish.
96

Table 3.- -Continued.
97

Table 3.- -Continued.
98

Table 3. --Continued.
9 9

Figure 1.- Schoener’s index (%) of dietary overlap of groundfish species in the Aleutian Islands area in 1991

ATF, arrowtooth flounder; PH, Pacific halibut; COD, Pacific cod; GT, Greenland turbot;

PLK, pollock; SST, shortspine thornyhead; ROU, rougheye rockfish; SHR, shortraker rockfish;

ATK, Atka mackerel; POP, Pacific ocean perch; NOR, northern rockfish.
100

ACKNOWLEDGMENTS

I would like to thank Patricia Livingston for reviewing an

earlier version of this manuscript and for giving many helpful

suggestions. Thanks also go to Tom Gerber, Richard Wiggins, and

Kirsten Rohrbach for analyzing the stomach contents used in this

study. Doug Smith's help with the computer programs was also

appreciated. I also thank Eric Brown and Robin Harrison for

reviewing this manuscript.
101

CITATIONS

American Fisheries Society. 1991. Common and scientific names of

fishes from the United States and Canada. American

Fisheries Society Special Publication 20, fifth edition.

183 p. American Fisheries Society, 5410 Grosvenor Lane,

Suite 110, Bethesda, MD 20814-2199.

Best, E. A., and G. St-Pierre. 1986. Pacific halibut as

predator and prey. Technical Report No. 21. International

Pacific Halibut Commission, P.O. Box 95009, Seattle,, WA

98145-2009.

Brodeur, R. D., and W. G. Pearcy. 1984. Food habits and dietary

overlap of some shelf rockfishes (Genus Sebastes) from the

northeastern Pacific Ocean. Fish. Bull., U.S. 82:269-293.

Dawson, P. 1991. Shortspine thornyhead. In Stock assessment and

fishery evaluation report for the 1992 Gulf of Alaska

groundfish fishery. North Pacific Fishery Management

Council, 605 W. 4th Ave., Suite 306 Anchorage, AK 99510.

Feder, H. M. 1980. Distribution, abundance, community structure,

and trophic relationships of the benthos of the northeastern

Gulf of Alaska from Yakutat Bay to Cross Sound. In

Environmental Assessment of the Alaskan Continental Shelf,

Annual Reports 1:597-648. U. S. Dep. Commer., Natl. Oceanic

Atmos. Admin., Off. Mar. Pollut. Assess., Juneau, Alaska.

Harrison, R. C. 1993. Data report: 1991 bottom trawl survey of

the Aleutian Islands area. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-AFSC-12, 144 p.

Ianelli, J. N., T. K. Wilderbuer, and T. M. Sample. 1994.

Greenland turbot. In Stock assessment and fishery evaluation

report for the groundfish resources of the Bering

Sea/Aleutian Islands regions as projected for 1995.

November 1994, compiled by the plan team for the groundfish

fisheries of the Bering Sea and Aleutian Islands. Nort h

Pacific Fishery Management Council, 605 W. 4th Ave., Suite

306, Anchorage, AK 99510.
102

International Pacific Halibut Commission. 1994. Appendix A:

Pacific halibut SAFE report. In Stock assessment and

fishery evaluation report for the groundfish resources of

the Bering Sea/Aleutian Islands regions as projected for

1995. November 1994, compiled by the plan team for the

groundfish fisheries of the Bering Sea and Aleutian

Islands, North Pacific Fishery Management Council, ,605 W.

4th Ave., Suite 306, Anchorage AK 99510.

Ito, D. 1994. Other rockfish. In Stock assessment and fishery

evaluation report for the groundfish resources of the Bering

Sea/Aleutian Islands regions as projected for 1995.

November 1994, compiled by the plan team for the groundfish

fisheries of the Bering Sea and Aleutian Islands. North

Pacific Fishery Management Council, 605 W. 4th Ave., Suite

306, Anchorage AK 99510.

Ito, D. H., and J. N. Ianelli. 1994. Pacific ocean perch. In

Stock assessment and fishery evaluation report for the

groundfish resources of the Bering Sea/Aleutian Islands

regions as projected for 1995. November 1994, compiled by

the plan team for the groundfish fisheries of the Bering Sea

and Aleutian Islands. North Pacific Fishery Management

Council, 605 W. 4th Ave., Suite 306, Anchorage, AK 99510.

Livingston, P. A. 1991. Pacific cod, p. 31-88. In P. A.

Livingston (ed.), Groundfish food habits and predation on

commercially important prey species in the eastern Bering

Sea from 1984 to 1986. U.S. Dep. Commer., NOAA Tech. -Memo.

NMFS F/NWC-207.

Livingston, P. A. 1991. Walleye pollock, p. 9-30. In P. A.

Livingston (ed.), Groundfish food habits and predation on

commercially important prey species in the eastern Bering

Sea from 1984 to 1986. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS F/NWC-207.

Livingston, P. A., A. Ward, G. M. Lang, and M-S. Yang. 1993.

Groundfish food habits and predation on commercially

important prey species in the eastern Bering Sea from 1987

to 1989. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-11,

192 p.
103

Lowe, S. A. 1994. Atka mackerel. In Stock assessment and

fishery evaluation report for the groundfish resources of

the Bering Sea/Aleutian Islands regions as projected for

1995. November 1994, compiled by the plan team for the

groundfish fisheries of the Bering Sea and Aleutian

Islands. North Pacific Fishery Management Council, 605 W.

4th Ave., Suite 306, Anchorage, AK 99510.

Mito, K. 1974. Food relationships among benthic fish

populations in the-Bering Sea. M.S. Thesis, Hokkaido

Univ., Hokkaido, Japan, 135 p.

North Pacific Fishery Management Council. 1994. Summary,

p. l-18. In Stock assessment and fishery evaluation report

for the groundfish resources of the Bering Sea/Aleutian

Islands regions as projected for 1995. Compiled by the

plan team for the groundfish fisheries of the Bering Sea

and Aleutian Islands. North Pacific Fishery Management

Council, 605 W. 4th Ave., Suite 306, Anchorage, AK 99510.

Novikov, N. P. 1968. Basic elements of the biology of the

Pacific halibut (Hippoalossus hippoglossus stenolepis

Schmidt) in the Bering Sea. In Sov. Fish. Inv. N. Pac. Pt.

II, 175-219. Isr. Prog. Sci. Transl. TT67-51204. Available

from the Department of Commerce, Clearinghouse for Federal

Scientific and Technical Information, Springfield, VA 22151.

Schoener, T. W. 1970. Non-synchronous spatial overlap of

lizards in patchy habitats. Ecology 51:408-418.

Simenstad, C. A., J. S. Isaksonk, and R. E. Nakatani. 1977.

Marine fish communities of Amchitka Island, Alaska. In

M.L. Merrit and R.G. Fuller (ed.), The Environment of

Amchitka Island, Alaska. U.S. Energy Research and

Development Administration. TID 267-12:451-492.

Skalkin, V. A. 1964. Pitanie morskikh okunei v Beringovum more

(Diet of rockfish in the Bering Sea). Tr. Vses. NauchnoIssled. Inst. Morsk. Rybn. Khoz. Okeanogr. 49 (Izv.

Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr.

51) : 151-166. In Russ. (Transl. by Isr. Program. Sci.

Transl., 1968, p. 159-174. In P. A. Moiseev (ed.), Soviet

fisheries investigations in the northeast Pacific, Part 2,
104

available U.S. Dep. Commer., Natl. Tech. Inf. Serv.,

Springfield, VA, as TT 67-51204).

Smith, R. L., A. C. Paulson, and J. R. Rose. 1978. Food and

feeding relationships in the benthic and demersal fishes of

the Gulf of Alaska and Bering Sea. In Environmental

assessment of the Alaskan continental shelf, Final Rep.,

Biol. Stud. Vol 1, p. 33-107. U.S. Dep. Commer., NOAA,

Environ. Res. Lab. Available Arctic Environ. Assess.

Cent., 222 W. 8th Ave., No. 56, Anchorage, AK 99513.

Takemura, Y., and T. Yamane. 1953. Notes on the food of

Pleurogrammus azonus taken from the western coast of

Hokkaido. Bull. JPN Soc. Sci. Fish. Vol. 19,

No. 2: 111-117.

Thompson, G. G. 1994. Pacific cod. In Stock assessment and

fishery evaluation report for the groundfish resources

of the Bering Sea/Aleutian Islands regions as projected

for 1995. Compiled by the Plan Team for the Groundfish

Fisheries of the Bering Sea and Aleutian Islands, North

Pacific Fishery Management Council, 605 W. 4th Ave., Suite

306, Anchorage, AK 99510.

Wilderbuer, T. K., and T. M. Sample. 1994. Arrowtooth flounder.

In Stock assessment and fishery evaluation report for the

groundfish resources of the Bering Sea/Aleutian Islands

regions as projected for 1995. North Pacific Fishery

Management Council, 605 W. 4th Ave., Suite 306, Anchorage,

AK 99510.

Yang, M-S. 1991. Arrowtooth flounder, p. 143-162. In P. A.

Livingston (ed.), Groundfish food habits and predation on

commercially important prey species in the eastern Bering

Sea from 1984 to 1986. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS F/NWC-207.

Yang, M-S. 1993. Food habits of the commercially important

groundfishes in the Gulf of Alaska in 1990. U.S. Dep.

Commer., NOAA Tech. Memo. NMFS-AFSC-22, 150 p.
105

Yang, M-S., and P. A. Livingston. 1986. Food habits and diet

overlap of two congeneric species, Atheresthes stomias

and Atheresthes evermanni, in the eastern Bering Sea.

Fish. Bull., U.S. 82:615-623.

Yang, M-S., and P. A. Livingston. 1988. Food habits and daily

ration of Greenland halibut, Reinhardtius hippoglossoides

in the eastern Bering Sea. U. S. Natl. Mar. Fish. Serv.,

Fish. Bull., U.S. 86:675-690.

Zolotov, O. G., and A. V. Medveditsyna. 1978. Feeding habits of

the one-finned greenling in coastal waters of the north

Kurile Islands. Sov. J. Mar. Biol. Vol. 4, No. 4: 790-792.

Zolotov, O. G., and A. M. Tokranov. 1991. Feeding

characteristics of greenlings and Irish lords during

spawning in the upper sublittoral of eastern Kamchatka. J.

Ichthyol. Vol. 31, No. 3:146-155.
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. 

AFSC59 MARTIN, M. H., and D. M. CLAUSEN. 1995. Data report: 1993 Gulf of Alaska bottom trawl survey,

 217 p. NTIS No. PB96-135561.

58 QUEIROLO, L. E., L. W. FRITZ, P. A. LIVINGSTON, M. R. LOEFFLAD, D. A. COLPO, and Y. L.

DEREYNIER. 1995. Bycatch, utilization, and discards in the commercial groundfish fisheries of the Gulf

of Alaska, eastern Bering Sea, and Aleutian Islands, 148 p. NTIS No. PB96-125547.

57 SMALL, R. J., and D. P. DEMASTER. 1995. Alaska marine mammal stock assessments 1995-57, 93p.

NTIS No. PB95-274734. 

56 DORN, M. W., S. M. FITZGERALD, M. A. GUTTORMSEN, and M. R. LOEFFLAD. 1995. An evaluation

of North Pacific groundfish observer program methods of haul weight estimation, 31 p. NTIS No. PB95-

271151.

55 PELLA, J., R. RUMBAUGH, and M. DAHLBERG. 1995. Incidental catches of salmonids in the 1991

North Pacific squid driftnet fisheries, 33 p. NTIS No. PB95-252722.

54 KINOSHITA, R. K., A. GRIEG, and J. M. TERRY. 1995. Economic status of the groundfish fisheries off

Alaska, 1993, 108 p. NTIS No. PB95-252714.

53 WING, B. L., and D. J. KAMIKAWA. 1995. Distribution of neustonic sablefish larvae and associated

ichthyoplankton in the eastern Gulf of Alaska, May 1990, 48 p. NTIS No. PB95-241519. 

52 HONKALEHTO, T., and N. WILLIAMSON. 1995. Echo integration-trawl survey of walleye pollock

(Theragra chalcogramma) in the southeast Aleutian Basin during February and March, 1994, 39 p. NTIS

No. PB95-219424.

51 CLARY, J. C. (editor). 1995. Poster abstracts and manuscripts from the Third International Conference

on Marine Debris, May 8-13, 1994, Miami, Florida, 108 p. NTIS No. PB95-210837.

50 MUNRO, P. T., and R. Z. HOFF. 1995. Two demersal trawl surveys in the Gulf of Alaska: Implications

of survey design and methods, 139 p. NTIS No. PB95-195061. 

49 STARK, J. W., and D. M. CLAUSEN. 1995. Data Report: 1990 Gulf of Alaska bottom trawl survey, 221

p. NTIS No. PB95-194825.

48 NARITA, R., M. GUTTORMSEN, J. GHARRETT, G. TROMBLE, and J. BERGER. 1994. Summary of

observer sampling of domestic groundfish fisheries in the northeast Pacific Ocean and eastern Bering Sea,

1991, 540 p. NTIS No. PB95-190963

47 DORN, M. W., E. P. NUNNALLEE, C. D. WILSON, and M. E. WILKINS. 1994. Status of the coastal

Pacific whiting resource in 1993, 101 p. NTIS No. PB95-176467.

46 SINCLAIR, E. H. (editor). 1994. Fur seal investigations, 1993, 93 p. NTIS No. PB95-178943.

45 SINCLAIR, E. H. (editor). 1994. Fur seal investigations, 1992, 190 p. NTIS No. PB95-173472.

44 KINOSHITA, R. K., and J. M. TERRY. 1994. Oregon, Washington, and Alaska exports of edible

fishery products, 1993, 52 p. NTIS No. PB95-165924.