NOAA Technical Memorandum NMFS-AFSC-11

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

February 1993

by

Patricia A. Livingston, Alison Ward,

Geoffrey M. Lang, and Mei-Sun Yang

Groundfish Food Habits and Predation on

Commercially Important Prey Species in

the Eastern Bering Sea from 1987 to 1989
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:

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.

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

National Marine Fisheries Service, NOAA.
NOAA Technical Memorandum NMFS-AFSC-11

Groundfish Food Habits and Predation on

Commercially Important Prey Species in

the Eastern Bering Sea from 1987 to 1989

Patricia A. Livingston, Alison Ward,

Geoffrey M. Lang, and Mei-Sun Yang

Alaska Fisheries Science Center

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

Seattle, WA. 98115-0070

U.S. DEPARTMENT OF COMMERCE

Barbara Hackman Franklin, Secretary

National Oceanic and Atmospheric Administration

John A. Knauss, Administrator

National Marine Fisheries Service

William W. Fox, Jr., Assistant Administrator for Fisheries

February 1993
This document is available to the public through:

National Technical Information Service

U.S. Department of Commerce

5285 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

This document describes the feeding habits of major.

groundfish species in the eastern Bering Sea based on stomach

content information collected during 1987, 1988, and 1989. The

total consumption of commercially important prey species by

groundfish populations is calculated for the main feeding period

of May through September during 1987, 1988, and 1989. Walleye

pollock (Theragra chalcogramma) cannibalism is also calculated

for the period of May through December. Estimated predation

mortality in terms of numbers and biomass during this period is

presented. These estimates are compared with existing knowledge

of prey species abundance. Possible impact of predation on prey

species abundance patterns is discussed.
THIS PAGE INTENTIONALLY LEFT BLANK
V

CONTENTS

Abstract.. ......................

Executive Summary ....................

Predator and Prey species .............

Total Groundfish Consumption Estimates. ......

Introduction. ......................

Methods .........................

Sample Collection and Laboratory Analysis .....

Data Analysis ...................

Results and Discussion. .................

Groundfish Predation on Commercially Important Prey

King crabs. .................

Snow and Tanner crabs ............

Roundfish ..................

Flatfish. ..................

Conclusions .... ....................

Citations ........................

Appendices: Food habits and population level consumption

of each groundfish species. ..............

Appendix A. Walleye pollock ..............

Appendix B. Pacific cod . . ..............

Appendix C. Yellowfin sole, flathead sole, rock sole,

and Alaska plaice. .............

Appendix D. Greenland turbot .......... . . ..

Appendix E. Arrowtooth flounder ............

Appendix F. Pacific halibut. ..............

Page

iii

1

1

1

9

11

11

12

17

17

17

20

21

29

51

53

55

55

77

113

153

165

179
EXECUTIVE SUMMARY

This document summarizes groundfish predation on

commercially important stocks of fish and crabs on the eastern

Bering Sea shelf from 1987 to 1989. The amount of predation is

calculated using estimates of predator biomass, daily ration, and

the proportion of various prey categories in the stomach

contents. Estimates are presented in terms of number and biomass

of prey consumed during the main sampling period of May through

September of each year.

Predator and Prey Species

The following groundfish predators are included in this

report because they are dominant members of the eastern Bering

Sea shelf fish fauna that consume commercially important fish or

crab. The commercially important prey eaten by some of these

predators are also listed below:

Groundfish

Walleye pollock

Pacific cod

Yellowfin sole

Greenland turbot

Arrowtooth flounder

Flathead sole

Pacific halibut

Alaska plaice

Rock sole

Commercially important prey

Walleye pollock

Pacific cod

Yellowfin sole

Greenland turbot

Arrowtooth flounder

Flathead sole

Rock sole

Pacific halibut

Pacific herring

King crabs

Snow crab

Tanner crab

Total Groundfish Consumption Estimates

The total amount of each prey consumed from May to September

of 1984 to 1989 is presented in Tables 1 and 2. These estimates

are the sum of the consumption by each predator species.

Consumption of walleye pollock also includes cannibalism

estimates during the period October to December of 1985 and 1989.

Biomass consumed is converted to number consumed using available

prey size information. If prey size information was lacking for

a predator, number consumed could not be estimated. Total number

consumed is an underestimate in these cases and is shown in

parentheses.

Estimated number at-age of snow crab (Chionoecetes opilio),

Tanner crab (C. bairdi), and walleye pollock (Theragra

chalcogramma) consumed by groundfish predators are presented
2

along with the estimated natural mortality coefficients at-age in

Tables 3-8 and Figure 1. Fluctuations in the number consumed atage can occur through several processes: changes in predator or

prey abundance, changes in prey availability, or changes in

predation rate due to predators switching to an abundant prey

source. If predators respond to increases in prey species

abundance by switching preferentially to feeding on the more

 abundant prey, they can cause density-dependent mortality on that

prey species. This means that predators can alter the relative

size of the prey population. Changes across years in annual

natural mortality coefficients at-age of juvenile prey

populations provide a signal that this process may be occurring.

Fluctuations in estimates of the annual natural mortality

coefficient at-age for snow crab, Tanner crab, and walleye

pollock were present (Tables 4,6, and 8). Large fluctuations in

coefficients for snow crab ages 1 and 2 were estimated,

particularly for age-l crab from 1984 to 1985 and age-2 crab from

1985 to 1986. There was a large recruitment of snow crab

possibly in 1983 or 1984, and the large natural mortality

coefficients estimated from groundfish predation data show larger

than average natural mortality at-age for the 1983 year class.

Larger mortality at-age for Tanner crab was noted at-age 0 for

the 1984 year class, which was also suspected to be above

average. Finally, natural mortality coefficients for the 1985

year class of walleye pollock are larger at-age than for adjacent

year classes. The 1985 year class was more abundant than the

1986 to 1989 year classes at age 1 but later proved to be about

the same size as the 1986 and 1987 year classes at age 3. It

appears that differential predation by groundfish on the 1985

year class from ages 0-2 may have reduced the relative abundance

of this year class upon recruitment to the fishery.
Table 1 .--Estimated total biomass (metric tons) by year of commercially important prey

consumed by groundfish from May through September in the eastern Bering

Sea. (Consumption of walleye pollock also includes cannibalism estimates from May

through December.)

*Walleye pollock cannibalism estimate was not available for 1984.
Table 2.--Estimated number (millions) by year of commercially important prey consumed

by groundfish from May through September in the eastern Bering Sea. (Consumption

of walleye pollock also includes cannibalism estimates from May through December.)

Values in parentheses indicate cells with some missing prey size information and

therefore are underestimates of the total number consumed.

'Most king crab consumed in 1984 were blue king crab megalops larvae.

"Walleye pollock cannibalism estimate was not available for 1984.
5

Table 3 .--Estimated number (millions) of snow crab, Chionoecetes

opolio, consumed by age by groundfish from May through

September in the eastern Bering Sea.

Table 4 .--Estimates of the instantaneous annual natural mortality

coefficient by age for snow crab, obtained from

reconstructing population sizes at-ages 0-2 using survey

estimates of population size at age 3 and assuming the

only mortality is mortality from predation by groundfish

(Table 3).
6

Table 5 .--Estimated number (millions) of Tanner crab, Chionoecetes

bairdi, consumed by age by groundfish from May through

September in the eastern Bering Sea.

Table 6. --Estimates of the instantaneous annual natural mortality

coefficient by age for Tanner crab, obtained from

reconstructing population sizes at ages 0-2 using survey

estimates of population size at age 3 and assuming the

only mortality is mortality from predation by groundfish

(Table 5).
7

Table 7 .--Estimated number (billions) of walleye pollock consumed by

age by groundfish from May through September and

by cannibalism from May through December in the eastern

Bering Sea.

Year

Age 1984* 1985 1986 1987 1988 1989

0 43.82 1,033.12 191.27 248.54 215.48 851.68

1 4.04 28.64 37.43 9.59 11.83 11.31

2 0.19 0.55 1.09 1.80 0.67 0.49

3 0.15 0.21 0.35 0.23 0.19 0.16

4 0.08 0.10 0.06 0.06 0.23 0.16

5 0.05 0.05 0.07 0.01 0.13 0.15

6+ 0.04 0.03 0.09 0.01 0.13 0.22

* Walleye pollock cannibalism estimate was not available for 1984.

Table 8. --Estimates of the instantaneous annual natural mortality

coefficient by age for walleye pollock, obtained from

reconstructing population sizes at ages 0-2 using cohort

analysis estimates of population size at age 3 and

assuming the only mortality is mortality from predation by

groundfish (Table 7).

Year

Age 1984* 1985 1986 1987 1988 1989

0 3.19 2.67 2.75

1 1.25 1.88 1.13 1.18

2 0.17 0.10 0.31 0.16 0.10

*Mortality coefficients were not estimated for 1984 because walleye

pollock cannibalism estimate was not available for that year.
Figure 1. --Estimated number at-age of walleye pollock, snow

crabs (Chionoecetes opilio), and Tanner crabs (c.

bairdi) consumed by groundfish during months 5 to 9

from 1984 to 1989 in the eastern Bering Sea.
INTRODUCTION

Many large marine fish are predators of either juvenile or

small adult fish and crab. Because predation forms the largest

part of natural mortality of young fish and crab, it is important

to estimate the magnitude of predation loss on commercially

important populations. Population models that assume constant

natural mortality rates due to a lack of information on actual

rates can be improved by providing more accurate estimates of

predation losses. The move toward multispecies management of

stocks can be helped through studying the food web connections

between components of marine ecosystems, which include fish,

crabs, marine mammals, and birds.

The primary purpose of the Trophic Interactions Program of

the Resource Ecology and Fishery Management Division (REFM) at

the Alaska Fisheries Science Center (AFSC) is to study the

 consumption of commercially important fish or crab by key fish

predators in the eastern Bering Sea. These fish and the fish

they consume are commercially important species and form a major

part of the groundfish biomass in the eastern Bering Sea.

Program objectives include providing impact assessments relating

to fish predation effects on prey species populations, improving

population model estimates of predation mortality by marine fish,

and detecting possible changes in abundance and distribution of

juvenile fish and crab populations.

This paper reports the progress of the Trophic Interactions

Program of the REFM Division of the AFSC in analyzing available

data from 1987 to 1989 on the predation of commercially important

fish and crab species. The first section details the methods

used to estimate the total biomass and numbers of prey consumed

by the major groundfish species in the area. The second section

summarizes the consumption of commercially important prey by all

the major predators. Appendices summarize the diet and total

prey consumption by the following predators: walleye pollock,

Pacific cod (Gadus macrocephalus), yellowfin sole (Pleuronectes

asper) , flathead sole (Hippoglossoides elassodon), rock sole

(Pleuronectes bilineata), Alaska plaice (Pleuronectes

quadrituberculatus), Greenland turbot (Reinhardtius

hippoglossoides), arrowtooth flounder (Atheresthes stomias), and

Pacific halibut (Hippoglossus stenolepis).
THIS PAGE INTENTIONALLY LEFT BLANK
11

METHODS

Sample Collection and Laboratory Analysis

Stomachs were collected from major groundfish species during

1987, 1988, and 1989 in the eastern Bering Sea. Samples were

taken year-round, but primarily during May through September

using bottom and pelagic trawl gear on research and commercial

fishing vessels. Sampling occurred throughout the 24-hour day,

although most sampling occurred between 0600 and 2000 Alaska

daylight time. For all species except walleye pollock, stomachs

were removed at sea and placed in cloth bags labelled with

information regarding the location of capture, fork length, sex,

and sexual maturity of the fish. Fish showing evidence of

regurgitation (i.e., food in the mouth or throat or a flaccid

stomach) were not included in the sample. Stomachs were

preserved in 10% formalin and later transferred to 70% ethyl

alcohol. Contents were identified to the lowest taxonomic level

possible and enumerated. Wet weights were recorded after the

contents were blotted with paper towels. Standard length (SL)

measurements of prey fish and carapace width (CW) or lengths (CL)

of crab prey were taken when whole prey were available.

For walleye pollock, a combination of collection and

analysis methods was used. Information collected during the main

sampling period of May through September (months 5 to 9) includes

stomachs collected and analyzed using the methodology described

above. Most of the information collected outside the main

sampling period was from fishery observers aboard commercial

fishing vessels who performed quantitative shipboard scans of

walleye pollock stomach contents. Only fish with no visible

evidence of regurgitation were selected for scans. Once a fish

was selected for scanning, the stomach was excised and the volume

of the stomach contents was determined by a water displacement

method by emptying the stomach contents into a graduated cylinder

or beaker containing a known amount of water. The difference

between the initial water level and the water level after the

stomach contents were added was the stomach volume. Volume was

later converted to weight by assuming 1 ml of volume displaced

was equal to 1 g. The contents were then emptied onto a petri

dish or tray, prey were separated into the lowest taxonomic

categories possible, and the volume (expressed as a percentage of

the total) was visually estimated and recorded for each prey

category. Numbers of individuals in a prey category were

counted, if practical. Measurements of fish and crab prey were

taken if an item was whole.

For both quantitative shipboard scans and detailed

laboratory analysis, the prey category "fishery discards" was

used if the ingested item had obviously been discarded from a

processor (i.e., a consumed fish that had its head sliced off
12

with a clean diagonal cut). Due to the difficulties involved in

shipboard identification of taxonomic categories, particularly by

inexperienced biologists, some prey taxa may have been

misidentified in shipboard stomach scans.

Data Analysis

Prey Consumption by Predator Populations

Estimates of the total biomass of each prey species consumed

by the continental shelf portion of each groundfish population

were calculated according to

where Ci is the consumption (by weight) of a prey species by size

group i of a predator species, DRi is the daily ration (as a

proportion of body weight daily, BWD) of predator size group i, D

is the number of days in the sampling period when the prey

species was vulnerable to predation, Bi is the biomass of the

predator size group i, and Pi is the proportion by weight of the

prey species in the diet of predator size group i.

Total consumption estimates using Equation (1) were computed

within each major stratum of the eastern Bering Sea (Fig. 1).

These strata were devised by the Resource Assessment and

Conservation Engineering (RACE) Division of the AFSC to reflect,

in general, natural boundaries based on bottom depth. Strata 1

and 2 are considered inner continental shelf areas, strata 3 and

4 comprise the middle shelf, and strata 5 and 6 are the outer

shelf zones.

Predator size groupings used for total consumption estimates

were based on size groupings used previously (Livingston et al.

1986, Livingston 1991) and on knowledge of each predator's diet.

If consumption of commercially important prey groups differed

among predator sizes, then predator size groups were chosen to

minimize such consumption differences within a size group.

Daily ration (DR) estimates (Table 1) were derived using

some basic bioenergetic considerations as an alternative to using

rations estimated from gastric evacuation rate models and fieldestimated stomach content weights. As Livingston et al. (1986)

found, estimates derived from gastric evacuation rate models tend

to be lower than expected based on known annual growth patterns

of eastern Bering Sea species. Part of the problem with rations

estimated in this fashion may be due to undetected regurgitation

of stomach contents from field collections. It is believed that

more realistic rations can be derived using bioenergetic

variables such as annual growth increments and food conversion

efficiency estimates; thus, that is the approach used here.

Daily growth in weight of each species size group was estimated
13

Figure 1. --Map of the eastern Bering Sea shelf showing bottom

depth zones and strata used in this report.
14

Table 1. --Estimated daily ration of groundfish species

in the eastern Bering Sea, expressed as a fraction

of body weight daily.
15

from annual growth increments by length and length-weight

relationships for each species. A gross conversion efficiency

rate of food to somatic tissue for juvenile fish was assumed to

be 25% and for adult fish was assumed to be 10% based on

estimates presented by Brett and Groves (1979). Daily growth

increments could thus be converted to the amount of food required

to produce that growth. When the daily food requirements are

divided by mean fish weight, then the result is daily ration

expressed as a fraction of body weight.

The time period of analysis (D) for total consumption

estimates by all predator species was months 5 to 9, or 153 days.

The analysis was restricted to this time period because most

stomach samples were collected during this period and survey

estimates of groundfish biomass were obtained at this time.

Unquantified migrations of fish into different strata occur and

insufficient numbers of stomach samples were taken in each

stratum outside of this time period. Thus, total consumption

estimates made outside of this time period would not be very

reliable. Since months 5 to 9 are probably the main feeding and

growth period for groundfish in the eastern Bering Sea, these

total consumption estimates can be considered conservative

estimates of total annual predation removals by these groundfish

populations.

Total consumption estimates of king crabs by Pacific cod

were restricted to a 31-day period during months 5 to 9 when it

is most likely that soft-shell (newly molted) king crabs were

available. Total consumption estimates for walleye pollock

cannibalism were also made for months 10 to 12 since there were

more walleye pollock stomach content data available during this

time period when compared to the other groundfish species.

However, walleye pollock biomass estimates for each stratum were

assumed to be the same as during the months 5 to 9 period.

Unknown changes in walleye pollock biomass within each stratum in

winter cause greater uncertainty in these estimates than those

derived during the main feeding period.

Predator biomass estimates (B) (listed in the respective

appendix for each species) for all species except walleye pollock

and yellowfin sole were obtained from RACE Division bottom trawl

survey data. These trawl surveys are conducted in the eastern

Bering Sea during June to August of each year. Biomass estimates

of. arrowtooth flounder and Greenland turbot include only the

shelf portion of the populations. Thus, total predation estimates

for these populations refer only to predation occurring on the

shelf. Biomass estimates of walleye pollock, a semipelagic fish,

were probably underestimated by the trawl survey, so the cohort

analysis estimates of Wespestad, Bakkala, and Dawson (1990) were

used and biomass was apportioned into each stratum by using the

proportion of the trawl survey biomass found in each stratum.

Biomass estimates of yellowfin sole from trawl surveys has

fluctuated unreasonably in recent years, so cohort analysis

estimates of biomass for age-7+ fish from Bakkala and Wilderbuer
16

(1990) were used along with trawl survey estimates of fish less

than age 7. Cohort analysis estimates of yellowfin sole biomass

were apportioned into each stratum using the proportion of the

trawl survey biomass found in each stratum.

The proportion by weight of each prey item in the diet of

each predator size group was calculated for each stratum in the

following fashion. First, all stomach content data for a

particular fish species size group that was collected in a

stratum during months 5 to 9 in a given year were used.

Estimates of the percentage by weight of a given prey item in the

stomach contents were then calculated for each 20 nautical mile

square in the stratum where stomachs were collected. The

estimated percent by weight of the prey item in the whole stratum

was then calculated as the average of the percentages from each

20 nautical mile square. Standard errors of the stratum

percentages were derived from the variance between squares.

For strata where prey size information was available, total,

consumption estimates in terms of biomass were converted to

number of prey. The size frequency of a particular prey in the

stomach contents of a given predator size group from a stratum in.

a particular year during months 5 to 9 was used along with the

length-weight relationship for the prey to convert biomass

consumed within a particular prey size interval to number

consumed. If prey size information for a given predator size

group was not available for a given stratum, then the size

frequency of that prey in all strata combined for the predator

size group was used. Finally, when no prey size information was

available, the number consumed could not be estimated.

Snow (Chionoecetes opilio) and Tanner (c. bairdi) crabs and

walleye pollock were assigned to approximate age groups based on

the following age-length conversions:
17

RESULTS AND DISCUSSION

Groundfish Predation on Commercially Important Prey

The total impact of groundfish predation on a particular

prey species was estimated by summing the individual predator

 species removals described in the appendices. Comparison of

total fish predation with each predator species' removals

provides an indication of which predator population tends to be

the most important source of mortality for a prey population.

Also, comparison of total predation removals with prey population

size demonstrates the relative importance of predation as a

source of mortality. Finally, interannual fluctuations in

predation on a particular age group of prey may give early

indications of changes in abundance of prey age groups before

they are vulnerable to assessment by trawl survey. The total

consumption of each important prey group is summarized in terms

of estimated biomass and numbers removed by groundfish predation

in the eastern Bering Sea for segments of the years 1987 to 1989.

King Crabs

Tables 2-3 present the estimated total biomass and number of

king crabs consumed by all groundfish predators for 31 days

during months 5 to 9 in 1987 through 1989.

Red king crab--Pacific cod was the main predator of red king

crabs (Paralithodes camtschatica) and king crabs that could not

be identified to the species level. Most of the unidentified

king crabs consumed by Pacific cod were assumed to be red king

crabs based on the locations where unidentified king crabs were

consumed. These crabs were assumed to be soft-shell females

based on the timing and location of consumption by Pacific cod.

Walleye pollock and yellowfin sole were minor predators on king

crabs and consumed mostly small larval or newly settled

juveniles. Pacific cod consumption of red king crab and

unidentified king crab was 836, 554, and 1,928.2 metric tons (t)

in 1987, 1988, and 1989, respectively. Groundfish predation on

king crab in terms of biomass during these three years was lower

than the estimated predation for the 1984-1986 period, which

ranged from 1,136 t to 2,867 t (Livingston 1991).

Abundance of female red king crab (Stevens and MacIntosh

1990) during the 1987 to 1989 time period declined from

35.1 million crab to 21.2 million crab. Pacific cod consumption

of unidentified and red king crab (which were assumed to be

females) was 3.8%, 4.8% and 14.3% of the estimated population

numbers of female red king crab for 1987, 1988, and 1989,

respectively.

Blue king crab--Blue king crab megalops larvae (Paralithodes

platypus) were consumed by walleye pollock in 1987. The blue
18

Table 2 .--Estimated total biomass (metric tons) of king crabs

consumed by groundfish by year for 31 days

during months 5 to 9 in the eastern Bering Sea.
19

Table 3. --Estimated total number (millions) of king crabs

consumed by groundfish by year for 31 days

during months 5 to 9 in the eastern Bering Sea. Values

in parentheses indicate cells with some missing prey

size information. Prey size was assumed to be 97.5 mm

carapace length for Pacific cod predator cells without

prey size information.
20

king crab consumed by Pacific cod in 1989 were soft-shell crabs

(presumably females). Pacific cod predation on blue king crab in

1989 was less than 1% of the number of blue king crab females in

the Pribilof District. Consumption of blue king crab by

groundfish predators appears to be a sporadic occurrence and was

found at only one or two stations sampled during the May through

September period. In the previous 3-year period (1984-86),

yellowfin sole was the only predator on blue king crab

(Livingston 1991). Predation occurred only in 1984 and was on

megalops larvae.

Snow and Tanner Crabs

Total biomass of snow and Tanner crabs consumed by

groundfish predators is presented in Table 4. Table 5 presents

data on the estimated number of snow crabs consumed in areas

where prey size information was available, so they should be __

considered the minimum number consumed by groundfish predators.

Figures 2-5 show the biomass and numbers removed by prey size

including results from the 1984-86 period for comparison.

Snow crabs--The main predator of snow crabs, in terms of

estimated biomass removed, was Pacific cod. Pacific cod consumed

at least 90% of the total biomass removals of snow crabs in all

three years.- The remaining predators were flathead sole, walleye

pollock, Pacific halibut, rock sole, and yellowfin sole. Biomass

of snow crabs consumed by Pacific cod decreased from 1987

(151,226.5 t) to 1989 (116,609 t), while numbers consumed by

Pacific cod were relatively constant over the time period.

Consumption of snow crab by the other groundfish predators did

not occur every year; 1989 was the only year out of the three

where more than two groundfish species were consuming snow crab.

Total number of snow crab consumed by all groundfish predators

doubled from 1987 to 1989, primarily due to the large numbers of

small crab consumed by flathead sole in 1989.

Most of the sampled snow crab consumed in 1988 and 1989 were

between 5 and 15 mm CW or approximately age 1. Stevens et al.

(1991) note strong recruitment of postlarval crab in the last few

years. The large numbers of age-l crab consumed in 1988 and 1989

may be a reflection of above-average numbers of small crab

recruiting into the southeastern Bering Sea shelf population.

Monitoring the amount of predation on small crabs by these

predators may provide early indications of the presence of

abundant year classes of crabs.

Reconstructing age-l snow crab population size (which was

the age most preyed upon) according to the methods of Forney

(1977) could be done for 1986-88 by using trawl estimates of

numbers at age 3 and backcalculating age-l population size

assuming predation removals were the main source of mortality

between age 1 and age 3. Consumption of age-l snow crabs by all

predators, expressed as a proportion of reconstructed age-l

population size from 1986 to 1988, was 44%, 43%, and 60%,
21

respectively. The large change in percent predation removals

from 1987 to 1988 is an indication that predators may be exerting

density-dependent influences on snow crab populations at age 1.

This means that the number of crabs recruiting into the fishable

stock may be dampened depending on groundfish predation amounts.

Tanner crabs--Estimated total biomass of Tanner crabs consumed by

all predators decreased from 1987 (107,134 t) to 1988 (55,825 t)

with a subsequent increase in 1989 (88,520 t). Like snow crabs,

most of the biomass removed was due to Pacific cod predation.

However, most of the numbers consumed were due to predation on

small (1-10 mm CW) crab by flatfish such as flathead sole, rock

sole, and yellowfin sole. Total number consumed was highest in

1987 (42,632 million) but was still much lower than the estimate

of total number consumed in 1984, which was 152,850 million

(Livingston 1991). This may be an indication that there has not

been any increased recruitment of Tanner crab since 1984.

Reconstruction of age-0 population size for 1985-87 and age1 population size for 1986 to 1988, using trawl estimates of

year-class abundance at age 3 and backcalculating abundance

assuming predation removals were the main source of mortality,

was done to determine whether predation was a variable proportion

of year-class abundance. Changing proportions of predation

removals would be an indication that predators were exerting

density-dependent control of prey population size. Predation on

Tanner crabs as a percent of the reconstructed age-0 population

size from 1985 to 1987 was 42%, 23%, and 67%, respectively.

Percent predation removals of age-l crabs from 1986 to 1988 was

90%, 95%, and 95%, respectively. Removals at age 0 are variable,

while those at age 1 appear to be high but stable rates of

removal across years. This may indicate predators are exerting a

density-dependent influence on the Tanner crab population size at

age 0 but not at age 1.

Roundfish

Roundfish, for the purposes of this report, is defined as

any groundfish species that is not a flatfish. Total estimated

biomass and minimum numbers of Pacific cod, walleye pollock,

-Pacific herring (Clupea pallasi), and Atka mackerel

(Pleurogrammus monopterygius) consumed by all groundfish

predators are summarized in Tables 6-7 and Figures 6-11.

Pacific cod--Total estimated biomass of Pacific cod consumed by

groundfish predators (Table 6) decreased from 1987 (8,880 t) to

1988 (1,330 t) and increased in 1989 back to a level similar to

1987 (7,762 t). Predators on- Pacific cod include Pacific cod,

walleye pollock, arrowtooth flounder, and Pacific halibut. There

was no dominant groundfish predator on Pacific cod across years.

Although Pacific cod cannibalism did occur each year, it was not

always the major source o-f predation mortality. The number

consumed was highest in 1987 (7.7 billion) and was primarily due

to Pacific cod cannibalism on age-0 fish. Most Pacific cod
22

Table 4. --Estimated total biomass (metric tons) of Tanner crabs

(Chionoecetes bairdi) and snow crabs (c. opilio) consumed

by groundfish by year during months 5 to 9 in

the eastern Bering Sea. (- = no samples taken.)
23

Table 5. --Estimated total number (millions) of Tanner crabs

(Chionoecetes bairdi) and snow crabs (c. opilio) consumed

by groundfish by year during months 5 to 9 in

the eastern Bering Sea. Values in parentheses indicate

cells where some prey size information was not available.

(- = no samples taken.)
24

Figure 2 .--Estimated biomass of snow crabs (Chionoecetes opilio)

consumed by groundfish during months 5 to 9

from 1984 to 1989 in the eastern Bering Sea by prey

size.
25

Figure 3. --Estimated number of snow crabs (Chionoecetes opilio)

consumed by groundfish during months 5 to 9

from 1984 to 1989 in the eastern Bering Sea by prey

size.
26

Figure 4. --Estimated biomass of Tanner crabs (Chionoecetes

bairdi) consumed by groundfish during months 5 to 9

from 1984 to 1989 in the eastern Bering Sea by prey

size.
27

Figure 5. --Estimated number of Tanner crabs (Chionoecetes bairdi)

consumed by groundfish during months 5 to 9

from 1984 to 1989 in the eastern Bering Sea by prey

size. (Note different y-axis scale for 1984.)
28

consumed by groundfish from 1984 through 1989 were age-0 fish.

There does not seem to be any relationship between the number of

age-0 Pacific cod consumed in a year and the strength of that

Pacific cod year class. For example, Thompson (1991) found the

1987 year class to be one of the smallest on record while our

data show that 1987 was the year with the largest number of age-0

Pacific cod consumed. It appears that Pacific cod is not a major

dietary component of any groundfish species. Therefore,

consumption of Pacific cod tends to be a sporadic occurrence that

may not necessarily be related to its abundance.

Walleye pollock--Walleye pollock was consumed by most-of the

major groundfish predators considered here. Walleye pollock

cannibalism dominated walleye pollock removals in terms of

biomass and numbers in all years. Pacific cod was the next most

important predator in terms of biomass removals, while yellowfin

sole and flathead sole were the next most important predators in

terms of numbers removed.

Sizes of walleye pollock consumed by predators indicate most

were age-0 walleye pollock (less than 14 cm SL) in all years

(Figs. 8-9). Pacific cod tended to consume a wide range of

walleye pollock sizes, mainly from 5 to 45 cm SL. Most age-l

pollock (approximately 14-22 cm SL) were consumed by Pacific cod,

walleye pollock, and arrowtooth flounder. More age-0 pollock

were consumed in 1989 than in 1987 and 1988. Wespestad et al.

(1990) show that the 1989 pollock year class at age 1 was larger

than the 1987 year class by about 40% and larger than the 1988

year class at age 1 by about 50%. However, the consumption of

age-0 pollock in numbers in 1989 is about three times more than

the consumption of age-0 walleye pollock in 1988. This might be

an indication that the 1989 year class was preyed on more heavily

at age 0 in relation to its abundance than the two previous year

classes. Age-O walleye pollock consumed in 1989 were smaller

than those consumed from 1985 to 1988. There may have been some

factor making smaller walleye pollock more available to predators

in 1989 that caused the increased predation.

Livingston (1992) found for the period from 1985 to 1988

that predation on age-0 walleye pollock was about proportional to

the amount remaining at age 1, indicating no density-dependent

predation pressure on age-0 walleye pollock in those years.

However, there was evidence of density-dependent predation on the

1985 walleye pollock year class beyond age 0. The apparent

effect of the density-dependent predation on the 1985 year class

was to decrease its relative abundance upon recruitment to the

fishery at age 3. Although the 1985 year class was more abundant

at age 1 than the subsequent three year classes following it, its

abundance at age 3 was similar to the year classes following it.

There are many factors that could influence predation on a

particular year class including the relative availability of

other prey to a predator and the availability and overlap of a

particular prey (and prey size) with the predator. Prediction of

density-dependent predation effects will be difficult until we
29

can understand more about each predator's prey size preferences

and about the abundance of important prey such as juvenile

walleye pollock.

Pacific herring--Pacific cod was the main predator on Pacific

herring, consuming the species in all three years. Walleye

pollock, arrow-tooth flounder, and Pacific halibut consumed

Pacific herring only during 1989. Biomass of Pacific herring

consumed by predators decreased from 1987 to 1989 and numbers

consumed were low for all three years. The level of Pacific

herring consumption by groundfish predators was much lower than

in 1985 and 1986.

Pacific herring consumed in 1988 and 1989 were immature

(< 20 cm) while those consumed in 1987 were larger than 25 cm.

Groundfish predation in 1987 and 1988, expressed as a percentage

of the available Pacific herring biomass, was 5% in 1987 and 3%

in 1988. (There was no cohort analysis estimate of biomass for

1989.) Pacific herring consumption by groundfish predators

tended to be sporadic in time and space and may depend on

encounter rates of Pacific herring schools rather than overall

biomass. Furthermore, most of the Pacific herring available

during the summer feeding period on the shelf are immature

Pacific herring because adults have moved inshore to spawn.

Pacific herring may constitute a larger fraction of the diet of

groundfish predators in other time periods when adult Pacific

herring have migrated to outer shelf waters for the winter

feeding period. However, we have insufficient samples during

autumn and winter to quantify Pacific herring consumption during

those periods.

Atka mackerel--Our samples indicated that Atka mackerel was

consumed only by Pacific cod and only in 1987. The last AFSC

groundfish predation report (Livingston 1991) noted no

consumption of Atka mackerel from 1984 to 1986. The current

center of distribution of Atka mackerel is in the Aleutian

Islands. Although their distribution in the past has extended

north to the Pribilof Islands, catches of Atka mackerel in the

Bering Sea are low. Atka mackerel were consumed at only one

station in the southwestern portion of the shelf, close to the

Aleutian Islands. The estimated consumption by Pacific cod in

1987 was less than 1% of the standing stock estimated in the 1991

Aleutian Islands survey (Lowe 1991). The sizes of Atka mackerel

consumed by Pacific cod ranged from 26 to 27 cm SL.

Flatfish

Arrowtooth flounder--Consumption of arrowtooth flounder by all

predators was variable across years (Tables 8-9). Estimated

total biomass consumed in 1987 (13,761 t) was about thirty times

greater than consumption in 1989 (464 t). No arrowtooth flounder

consumption was observed in 1988. In both years where arrowtooth

flounder were consumed, Pacific cod was the main predator in

terms of biomass removed. Arrowtooth flounder cannibalism and
30

Table 6. --Estimated total biomass (metric tons) of roundfish

consumed by groundfish by year during months 5

to 9, including walleye pollock cannibalism during months

10 to 12, in the eastern Bering Sea. ( - = no samples

taken.)
31

Table 7 .--Estimated total number (millions) of roundfish

consumed by groundfish by year during months 5

to 9, including walleye pollock cannibalism during months

10 to 12, in the eastern Bering Sea. Values in

parentheses indicate cells where some prey size

information was not available. ( - = no samples

taken.)
32

Figure 6.--Estimated biomass of Pacific cod consumed by

groundfish during months 5 to 9 from 1984 to 1989 in

the eastern Bering Sea by prey size. (Note different

y-axis scale for 1987.)
33

Figure 7. --Estimated number of Pacific cod consumed by groundfish

during months 5 to 9 from 1984 to 1989 in the

eastern Bering Sea by prey size. (Note different yaxis scales throughout.)
34

Figure 8. --Estimated biomass of walleye pollock consumed by

groundfish other than walleye pollock during

months 5 to 9 in 1984 and by groundfish including

walleye pollock during months 5 to 9 plus

cannibalism by walleye pollock during months 10 to 12

from 1985 to 1989 in the eastern Bering Sea by prey

size. (Note different y-axis scales for 1984 and

1985.)
35

Figure 9. --Estimated number of walleye pollock consumed by

groundfish other than walleye pollock during

months 5 to 9 in 1984 and by groundfish including

walleye pollock during months 5 to 9 plus

cannibalism by walleye pollock during months 10 to 12

from 1985 to 1989 in the eastern Bering Sea by prey

size.
36

Figure 10. --Estimated biomass of Pacific herring consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by

prey size.
37

Figure 11. --Estimated number of Pacific herring consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by

prey size.
38

predation by walleye pollock also occurred in both years.

Walleye pollock consumed the largest number of arrow-tooth

flounder. Most of the arrowtooth flounder consumed by walleye

pollock were 2 to 5 cm SL.

Total biomass consumed in each year can be compared with the

estimated standing stock of arrowtooth flounder to determine the

relative importance of predation on the arrow-tooth flounder

population (Table 10). Total consumption in each year, expressed

as a percentage of trawl-estimated biomass of arrowtooth

flounder, is less than 5%. This is a small percentage of the

arrowtooth flounder population, indicating predation is probably

not a major source of mortality. Examination of possible

predation impact on arrowtooth flounder too small to be assessed

by the trawl survey is not possible given the current state of

knowledge about juvenile arrowtooth flounder abundance. However,

most of the numbers of arrowtooth flounder consumed in 1987 were

age-0 fish, and Sample and Wilderbuer (1991) note that 1987 was a

year of strong recruitment. The increased consumption of

arrowtooth flounder in that year may have been the result of

increased availability of small fish.

Flathead sole--Estimated total biomass of flathead sole consumed

by groundfish predators was relatively low in 1987 (1,965 t) and

1988 (1,453 t) but was much higher in 1989 (25,718 t). Numbers

consumed followed a similar trend. Most of the biomass consumed

in 1989 was by Pacific cod, but walleye pollock consumed the most

in terms of numbers in that year (Table 9). This difference

between biomass and number was due to the large number of small

(5-7 cm SL or possibly age 0) flathead sole consumed by walleye

pollock in that year (Figs. 12-13). Pacific cod was the most

important predator of flathead sole in all years if biomass

consumed is considered. Other predators on flathead sole

included arrowtooth flounder, flathead sole, and Pacific halibut.

Most of the flathead sole consumed were less than 20 cm SL or

less than age 3. Walters and Wilderbuer (1990) report that

flathead sole do-not recruit to trawl fisheries until age 3, and

although some age-2 fish are caught in research trawls, they are

probably not fully recruited. This precludes a relevant

comparison of predator removals of juveniles with the juvenile

flathead sole population size. However, total biomass removals

by predators expressed as a percentage of trawl survey estimates

of biomass for 1987-89 (Table 10) are less than 5% for each year.

This is a small proportion, at least of the adult portion of the

population, indicating predation may not be a significant source

of mortality for flathead sole.

In all three years, predators consumed some flathead sole

that were possibly age 0, but total numbers of age-0 flathead

sole consumed in 1989 were much higher than the other two years

(Fig. 13). This might be an indication of an abundant year class

produced in 1989.
Rock sole--Total estimated biomass of rock sole consumed by

groundfish

1987.

predators ranged from 5,155 t in 1988 to 18,552 t in

The number of rock sole consumed followed an opposite

trend. Pacific cod was the most important predator in terms of

biomass removals. Other predators included walleye pollock,

arrowtooth flounder, flathead sole, and yellowfin sole. Size

composition of rock sole consumed in all three years tended to

consist of fish mainly between 5 and 15 cm SL (Figs. 14-15),

sizes that are probably not fully vulnerable to trawl surveys.

39

Flathead sole consumed large numbers of age-0 rock sole -in

1988, which might indicate an abundant 1988 year class of rock

sole. However, relative numbers at age 2 in the 1990 survey

(Walters and Wilderbuer 1991a) suggest this year class was not

necessarily a strong one. Total biomass consumed, expressed as a

percentage of survey estimates of biomass in the three years

(Table 10) was less than 2% in each year.

yellowfin sole--Pacific cod, walleye pollock and Pacific halibut

were predators of yellowfin sole during the 1987 to 1989 period.

Pacific cod predation in terms of biomass dominated all three

years. Consumption by all groundfish in terms of biomass

decreased from 17,394 t in 1987 to 7,190 t in 1989. Consumption

was much lower in this period than in the 1984 to 1986 period

where values ranged from 28,359 t to 56,291 t (Livingston 1991).

These changes in consumption do not seem to be related to changes

in biomass of yellowfin sole on the shelf because total biomass

of yellowfin sole has been relatively stable from 1984 to 1989

according to stock synthesis model results (Bakkala and

Wilderbuer 1991).

Unlike the other years in the time series, consumption in

1987 was dominated by age-0 yellowfin sole in terms of numbers

eaten by walleye pollock (Figs. 16-17). Pacific cod also

consumed mainly small yellowfin sole in 1989. In other years,

most predation was on yellowfin sole ranging in size from 10 to

25 cm SL (ages 3-10). There is no information yet available to

support the conclusion that 1987 or 1989 produced a large year

class of yellowfin sole. When estimates of total yellowfin sole

consumption in terms of biomass are compared to the biomass

estimated from trawl surveys (Table 10), it seems that groundfish

predation constitutes only a small proportion (< 1%) of the

standing stock biomass.

Greenland turbot--Pacific cod and walleye pollock were the only

groundfish that consumed Greenland turbot (Tables 8-9). Amounts

consumed were negligible in 1987 and 1988. Walleye pollock was

the main predator on Greenland turbot in 1989, consuming

17,628 t. Sizes consumed by walleye pollock ranged from 2 to 4

cm SL (probably age 0). There is currently no evidence to

support an above-average Greenland turbot year class in 1989. It

seems likely that consumption of Greenland turbot by groundfish

predators is sporadic and limited to small areas of the shelf.
40

Pacific halibut--Pacific halibut was consumed by walleye pollock

during 1988 (Tables 8-9). Sizes consumed ranged from 2 to 4 cm

SL (probably age 0). The size of Pacific halibut consumed

suggests they were post-larvae that had not yet settled to the

bottom. Deriso (1987) suggests that Pacific halibut may be

transported into the Bering Sea from the Gulf of Alaska. It is

possible that groundfish consumption of Pacific halibut is a

transitory phenomenon, occurring during restricted time periods

when postlarvae are swept into shallow waters and start settling

to the bottom. The total consumption estimates assume that

predation is occurring throughout the month 5 to 9 period,

whereas the vulnerability of young Pacific halibut to walleye

pollock feeding in the water column may be of shorter duration,

implying that consumption estimates are probably high.

Alaska plaice--Alaska plaice was consumed by walleye pollock

during 1989. The size of Alaska plaice consumed was 4 cm SL

(probably age 0). The amount consumed (13 t) was small relative

to the standing stock of Alaska‘ plaice (599,400 t) (Walters and

Wilderbuer 1991b), suggesting groundfish predation on Alaska

plaice may not be a significant source of mortality.
41

Table 8 .--Estimated total biomass (metric tons) of flatfish

consumed by groundfish by year during months 5

to 9 in the eastern Bering Sea. (- = no samples taken.)
42

Table 9 .--Estimated total number (millions) of flatfish

consumed by groundfish by year during months 5

to 9 in the eastern Bering Sea. Values in parentheses

indicate cells where some prey size information was

not available. ( - = no samples taken.)
43

Table 10. --Total biomass of flatfish consumed by

groundfish, trawl survey estimates of

biomass, and percent consumed by year in

the eastern Bering Sea. (Biomass in metric

tons.)

*Sources: Low and Narita(1990) and Wilson and Armistead(l991).
44

Figure 12.--Estimated biomass of flathead sole consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by

prey size.
45

Figure 13.--Estimated number of flathead sole consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by

prey size.
46

Figure 14. --Estimated biomass of rock sole consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by prey

size.
47

Figure 15.--Estimated number of rock sole consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by prey

size. (Note different y-axis scale for 1984.)
48

Figure 16. --Estimated biomass of yellowfin sole consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by

prey size.
49

Figure 17. --Estimated number of yellowfin sole consumed by

groundfish during months 5 to 9 from

1984 to 1989 in the eastern Bering Sea by

prey size. (Note different y-axis scales for 1987

and 1989.)
THIS PAGE INTENTIONALLY LEFT BLANK
51

CONCLUSIONS

Predation by Pacific cod on Tanner and snow crabs in the

eastern Bering Sea may constitute a large portion of the juvenile

populations of these two species and may be a density-dependent

factor that regulates the number of crabs that recruit to the

fishery. Walleye pollock cannibalism was the most important

source of groundfish predation on age-0 walleye pollock and may

also prove to be a density-dependent factor. A longer time

series of predation data is needed to determine whether these

data can be used as early indicators of year-class abundance. A

better understanding of Tanner and snow crab size at-age and of

the juvenile abundances of both these crabs as well as walleye

pollock are needed to determine whether predation is a densitydependent factor controlling population size.

In many cases, groundfish appeared to be an early sampler of

Tanner and snow crabs, blue king crabs, and several flatfish

species. Again, more information on juvenile abundance of these

prey species may determine whether this predation is an early

indicator of the presence of abundant year classes.

Consumption estimates for all prey should be viewed at the

present time more as indices of consumption rather than actual

consumption for several reasons. First, most of the calculations

(except for walleye pollock cannibalism) consider only the time

period from May through September in each year. Although this is

the main feeding period for most fishes in the Bering Sea,

consumption of prey certainly occurs during other parts of the

year. Inadequate numbers and spatial distribution of stomach

samples during other parts of the year combined with gaps in

knowledge about the seasonal migrations of groundfish predators

make calculation of predation in other parts of the year

difficult without seasonal resource assessment surveys in the

area.

Predation estimates during the time period considered here

may be underestimates for prey that are consumed year-round, such

as Tanner and snow crabs that are consumed by Pacific cod.

Predation estimates for groundfish predation on newly settling

stages of crabs and flatfishes may be overestimates if the prey

species are not available to the predator during the whole time

period. Also, for prey that have a very limited spatial

distribution within a stratum, such as red and blue king crabs,

inadequate stomach sampling throughout the whole stratum can

provide biased estimates of consumption. For these prey,

consumption estimates would be biased upwards if sampling was

concentrated more in areas where king crabs occur and estimates

would be biased downwards if stomach sampling was not performed
52

in king crab areas. Sampling density was doubled beginning in

1989 so that problems such as this will be minimized in 1989 and

future years.

Estimates of total numbers consumed are underestimates for

some prey since prey size data were not available for all

predators consuming a particular prey due to advanced digestion

of prey.

Total consumption estimates in terms of biomass are

underestimates of total groundfish predation if important

groundfish predators of a particular prey have not been sampled.

Skates are growing parts of the groundfish biomass in the eastern

Bering Sea and consideration of their predation is becoming

important. Stomach sampling of skates was initiated in 1992 and

will be a regular part of the food habits sampling if it proves

to be an important consumer of commercially important prey.
Bakkala, R. G., and T. K. Wilderbuer. 1990. Yellowfin sole. In

Stock assessment-and fishery evaluation document for

groundfish resources in the Bering Sea/Aleutian Islands

region as projected for 1991. North Pacific Fishery

Management Council, P.O. Box 103136, Anchorage, AK 99510.

Bakkala, R. G., and T. K. Wilderbuer. 1991. Yellowfin sole. In

Stock assessment and fishery evaluation document for

groundfish resources in the Bering Sea/Aleutian Islands

region as projected for 1992. North Pacific Fishery

Management Council, P.O. Box 103136, Anchorage, AK 99510.

Brett, J. R., and T. D. D. Groves. 1979. Physiological

energetics. In W. S. Hoar, D. J. Randall, and J. R. Brett

(editors), Fish physiology, Vol. VIII: Bioenergetics and

growth, p. 279-352. Academic Press, New York.

Deriso, R. B. 1987. Pacific halibut: Biology, fishery, and

management. Northwest Environ. J. 3:129-144.

Forney, J. L. 1977. Reconstruction of yellow perch (Perca

flavescens) cohorts from examination of walleye

(Stizostedion vitreum vitreum) stomachs. J. Fish. Res.

Board Can. 34:925-932.

Livingston, P.A. 1991. 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. 1992. The importance of walleye pollock,

Theragra chalcogramma, and Pacific herring, Clupea pallasi,

to groundfish, marine mammals, birds, and fisheries in the

eastern Bering Sea. Unpubl. manuscr. Alaska Fisheries

Science Center, 7600 Sand Point Way NE, Seattle, WA 98115.

Livingston, P. A., D. A. Dwyer, D. L. Wencker, M. S. Yang, and

G. M. Lang. 1986. Trophic interactions of key fish species

in the eastern Bering Sea. Int. N. Pac. Fish. Comm. Bull.

47:49-65.

Low, L-L., and R. E. Narita (editors). 1990. Condition of

groundfish resources in the Bering Sea-Aleutian Islands

regions as assessed in 1988. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS F/NWC-178.

Lowe, S. A. 1991. Atka mackerel. In Stock assessment and

fishery evaluation report of the Bering Sea/Aleutian

Islands region as projected for 1992. North Pacific
54

Fishery Management Council, P.O. Box 103136, Anchorage,

AK 99510.

Sample, T. M., and T. K. Wilderbuer. 1991. Arrowtooth flounder.

In Stock assessment and fishery evaluation report of

the Bering Sea/Aleutian Islands region as projected for

1992. North Pacific Fishery Management Council, P.O. Box

103136, Anchorage, AK 99510.

Stevens, B. G., and R. A. MacIntosh. 1990. Report to industry

on the 1990 eastern Bering Sea crab survey. NWAFC Processed

Rep. 90-09, 50 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish.

Serv., NOAA, 7600 Sand Point Way NE., Seattle, WA 98115.

Stevens, B. G., R. A. MacIntosh, and J. A. Haaga. 1991. Report

to industry on the 1991 eastern Bering Sea crab survey.

AFSC Processed Rep. 91-17, 53 p. Alaska Fish. Sci. Cent.,

Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE,

Seattle, WA 98115.

Thompson, G. G. 1991. Pacific cod. In Stock assessment and

fishery evaluation report of the Bering Sea/Aleutian Islands

region as projected for 1992. North Pacific Fishery

Management Council, P.O. Box 103136, Anchorage, AK 99510.

Walters, G. E., and T. K. Wilderbuer. 1990. Other flatfish.

In L-L. Low and R. E. Narita (editors), Condition of

groundfish resources in the Bering Sea-Aleutian Islands

region as assessed in 1988, p. 123-141. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS F/NWC-178.

Walters, G. E., and T. K. Wilderbuer. 1991a. Rock sole. In

Stock assessment and fishery evaluation report of the

Bering Sea/Aleutian Islands region as projected for 1992.

North Pacific Fishery Management Council, P.O. Box 103136,

Anchorage, AK 99510.

Walters, G. E., and T. K. Wilderbuer. 1991b. Other flatfish.

In Stock assessment and fishery evaluation report of the

Bering Sea/Aleutian Islands region as projected for 1992.

North Pacific Fishery Management Council, P.O. Box 103136,

Anchorage, AK 99510.

Wespestad, V. G., R. G. Bakkala, and P. Dawson. 1990. Walleye

pollock. In Stock assessment and fishery evaluation

document for-groundfish resources in the Bering Sea/Aleutian

Islands region as projected for 1991. North Pacific Fishery

Management Council, P.O. Box 103136, Anchorage, AK 99510.

Wilson, M. T., and C. E. Armistead. 1991. 1989 Bottom trawl

survey of the eastern Bering Sea continental shelf. U.S.

Dep. Commer . , NOAA Tech. Memo. NMFS F/NWC-212.
55

APPENDIX A

Walleye Pollock

Appendix A presents biomass, food habits, prey composition,

prey size, and prey consumption estimates for walleye pollock

during months 5 to 9 and months 10 to 12 from 1987, 1988, and 1989

Table Page

in the eastern Bering Sea.

List of Tables

A-l. --Cohort analysis estimates of walleye pollock

biomass (metric tons) in the eastern Bering

Sea from Wespestad, Bakkala and Dawson (1990)

by pollock size, year, and stratum. . . . . . . . .

A-2. --Mean percent by weight (%W) and standard error (SE)

of prey walleye pollock in the stomach contents of

walleye pollock by year, stratum, predator size group,

and time of year in the eastern Bering Sea.

(* - no standard error estimate since only one

station was sampled, - = no samples taken.). . . . .

A-3. --Mean percent by weight (%W) and standard error

(SE) of miscellaneous commercial crab species

in the stomach contents of walleye pollock by

prey species, pollock size group, year,

strata, and time of year. (- = no samples

taken.)......................

A-4. --Mean percent by weight (%W) and standard

error (SE) of miscellaneous commercial fish

species in the stomach contents of walleye

pollock by prey species, pollock size group,

year, strata, and time of year. (- = no

samples taken.). . . . . . . . . . . . . . . . . .

A-5. --Estimated total biomass (thousand metric tons) of

prey walleye pollock consumed by walleye pollock

by year, stratum, predator size group, and

time of year in the eastern Bering Sea. Numbers in

parentheses indicate cells where no prey size

information was available. (- = no samples taken.).

58

59

60

61

62
56

A-6. --Estimated number (billions) of prey walleye pollock

consumed by walleye pollock by year, stratum,

predator size group, and time of year in the eastern

Bering Sea. Numbers in parentheses indicate cells

where no prey size information was available. (= - no

samples taken.) . . . . . . . . . . . . . . . . . . . 63

A-7. --Total biomass (metric tons) of miscellaneous commercial

crab species consumed by walleye pollock by prey species,

pollock size group, year, strata, and time of year.

Values in parentheses indicate cells where no prey size

information was available. ( - = no samples taken.). . 64

A-8 .--Total biomass (metric tons) of miscellaneous commercial

fish species consumed by walleye pollock by prey

species, pollock size group, year, strata, and time

of year. Values in parentheses indicate cells where 

no prey size information was available. (- = no

samples taken.). . . . . . . . . . . . . . . . . . 65

A-9. --Total number (millions) of miscellaneous commercial

crab species consumed by walleye pollock by prey

species, pollock size group, year, strata, and time

of year. Values in parentheses indicate cells

where no prey size information was available. ( - = no

-samples taken.). . . . . . . . . . . . . . . . . . 66

A-10. --Total number (millions) of miscellaneous commercial

fish species consumed by walleye pollock by prey

species, pollock size group, year, strata, and time

of year. Values in parentheses indicate cells where

no prey size information was available. ( - = no

samples taken.). . . . . . . . . . . . . . . . . .

A-11. --Size ranges of some commercially important prey

consumed by walleye pollock during months 5 to 9

in the eastern Bering Sea during 1987 to 1989. . . .

List of Figures

Figure

 A-l. --Diet composition of walleye pollock, in terms of

percent by weight, during months 5 to 9 and months

10 to 12 by predator size for 1987 to 1989 in the

eastern Bering Sea. . . . . . . . . . . . . . . . .

A-2. --Size frequency of prey walleye pollock found in

two size groups of walleye pollock during months

5 to 9 in 1987, 1988, and 1989 in the eastern Bering

Sea........................

67

68

Page

69

70
57

A-3 .--Size frequency of prey walleye pollock found in

two size groups of walleye pollock during months

10 to 12 in 1987, 1988, and 1989 in the eastern Bering

Sea........................ 71

A-4. --Percent by weight of prey walleye pollock in the diet

of walleye pollock by sampling station during months

5 to 9 in 1987, 1988, and 1989 in the eastern Bering

Sea........................ 72

A-5 .--Percent by weight of prey walleye pollock in the diet

of walleye pollock by sampling station during months

10 to 12 in 1987, 1988, and 1989 in the eastern Bering

Sea........................ 73

A-6 .--Percent by weight of Pacific herring, Greenland

turbot, flathead sole, and rock sole in the diet of

walleye pollock by sampling station during months

5 to 9 in various years in the eastern Bering Sea. . 74

A-7. --Biomass and number of prey walleye pollock consumed by four

size groups of walleye pollock during months 5 to 9 of

1987, 1988, and 1989 by prey size. . . . . . . . . . 75

A-8. --Biomass and number of prey walleye pollock consumed by four

size groups of walleye pollock during months 10 to 12 of

1987, 1988, and 1989 by prey size. . . . . . . . . . 76
58

Table A-l. --Cohort analysis estimates of walleye pollock

biomass (metric tons) in the eastern Bering

Sea from Wespestad, Bakkala and Dawson (1990)

by pollock size, year, and stratum.
Table A-2. --Mean percent by weight (%W) and standard error (SE) of prey walleye

pollock in the stomach contents of walleye pollock by year, stratum,

predator size group, and time of year in the eastern Bering Sea. (* -

no standard error estimate since only one station was sampled, - = no

samples taken.)
60

Table A-3. --Mean percent by weight (%W) and standard error

(SE) of miscellaneous commercial crab species

in the stomach contents of walleye pollock by

prey species, pollock size group, year,

strata, and time of year. (- = no samples

taken.)
61

Table A-4 .--Mean percent by weight (%W) and standard

error (SE) of miscellaneous commercial fish

species in the stomach contents of walleye

pollock by prey species, pollock size group,

year, strata, and time of year. (- = no

samples taken.)
Table A-5. --Estimated total biomass (thousand metric tons) of prey walleye

pollock consumed by walleye pollock by year, stratum,

predator size group, and time of year in the eastern

Bering Sea. Numbers in parentheses indicate cells where

no prey size information was available. (- = no samples taken.)
Table A-6. --Estimated number (billions) of, prey walleye pollock consumed by

walleye pollock by year, stratum, predator size group, and

time of year in the eastern Bering Sea. Numbers in parentheses

indicate cells where no prey size information was available. (= - no

samples taken.)
64

Table A-7 .--Total biomass (metric tons) of miscellaneous

commercial crab species consumed by walleye

pollock by prey species, pollock size group,

year, strata, and time of year. Values in

parentheses indicate cells where no prey size

information was available. ( - = no samples

taken.)
65

Table A-8 .--Total biomass (metric tons) of miscellaneous

commercial fish species consumed by walleye

pollock by prey species, pollock size group,

year, strata, and time of year. Values in

parentheses indicate cells where no prey size

information was available. ( - = no samples

taken.)
66

Table A-9. --Total number (millions) of miscellaneous

commercial crab species consumed by walleye

pollock by prey species, pollock size group,

year, strata, and time of year. Values in

parentheses indicate cells where no prey size

information was available. ( - = no samples

taken.)
67

Table A-10. --Total number (millions) of miscellaneous

commercial fish species consumed by walleye

pollock by prey species, pollock size group,

 year, strata, and time of year. Values in

parentheses indicate cells where no prey size

information was available. ( - = no samples

taken.)
68

Table A-ll.--Size ranges of some commercially important prey

consumed by walleye pollock during months 5 to 9

in the eastern Bering Sea during 1987 to 1989.
69

Figure A-l. --Diet composition of walleye pollock, in terms of

percent by weight, during months 5 to 9 and months

10 to 12 by predator size for 1987 to 1989 in the

eastern Bering Sea.
70

Figure A-2. --Size frequency of prey walleye pollock found in

two size groups of walleye pollock during months

5 to 9 in 1987, 1988, and 1989 in the eastern Bering

Sea.
71

Figure A-3. --Size frequency of prey walleye pollock found in

two size groups of walleye pollock during months

10 to 12 in 1987, 1988, and 1989 in the eastern Bering

Sea.
Figure A-4.--Percent by weight of prey walleye pollock in the diet

of walleye pollock by sampling station during months

5 to 9 in 1987, 1988, and 1989 in the eastern Bering

Sea.
Figure A-5. --Percent by weight of prey walleye pollock in the diet

of walleye pollock by sampling station during months

10 to 12 in 1987, 1988, and 1989 in the eastern Bering

Sea.
Figure A-6. --Percent by weight of Pacific herring, Greenland

turbot, flathead sole, and rock sole in the diet of

walleye pollock by sampling station during months

5 to 9 in various years in the eastern Bering Sea.
75

Figure A-7. --Biomass and number of prey walleye pollock consumed by

four size groups of walleye pollock during months 5 to

9 of 1987, 1988, and 1989 by prey size.
76

Figure A-8. --Biomass and number of prey walleye pollock consumed by

four size groups of walleye pollock during months 10

to 12 of 1987, 1988, and 1989 by prey size.
77

APPENDIX B

Pacific Cod

Appendix B presents biomass, food habits, prey composition,

prey size, and prey consumption estimates for Pacific cod during

months 5 to 9, from 1987, 1988, and 1989 in the eastern Bering Sea.

List of Tables

Table

B-l. --Estimated biomass in metric tons of Pacific

cod in the eastern Bering Sea by cod size,

year, and stratum. . . . . . . . . . . . . . . . .

B-2. --Mean percent by weight (%W) and standard error

(SE) of roundfish in the stomach contents of

Pacific cod by prey species, cod size group,

year, and strata during months 5 to 9 in the

eastern Bering Sea. ( * = no standard error

estimate since only one station was sampled.). . . .

B-3 .--Mean percent by weight (%W) and standard error

(SE) of flatfish in the stomach contents of

Pacific cod by prey species, cod size group,

year, and strata during months 5 to 9 in the

eastern Bering Sea. . . . . . . . . . . . . . . . .

B-4. --Mean percent by weight (%W) and standard error

(SE) of king crabs in the stomach contents of

Pacific cod by prey species, cod size group,

year , and strata during months 5 to 9 in the

eastern Bering Sea. . . . . . . . . . . . . . . . .

B-5 .--Mean percent by weight (%W) and standard error

(SE) of snow (Chionoecetes opilio) and Tanner

(C. bairdi) crabs in the stomach contents of

Pacific cod by prey species, cod size group,

year, and strata during months 5 to 9 in

the eastern Bering Sea. (* = no standard

error since only one station was sampled,

- = no samples taken.). . . . . . . . . . . . . . .

Page

81

82

83

84

85
B-6 .--Estimated total weight (metric tons) of roundfish

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. . . . . . . . . . . . . . . . . 86

78

B-7. --Estimated total number (millions) of roundfish

consumed by Pacific cod by prey species, cod size

group, year-, and strata during months 5 to 9 in the

eastern Bering Sea. Parentheses indicate cells where

no prey size information was available. . . . . . . 87

B-8 .--Estimated total biomass (metric tons) of flatfish

consumed by Pacific cod by prey species, cod size

group , year , and strata during months 5 to 9 in the

eastern Bering Sea. . . . . . . . . . . . . . . . . 88

B-9. --Estimated total number (millions) of flatfish

consumed by Pacific cod by-prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Numbers in parentheses indicate

cells where no prey size information was available. . 89

B-10. --Estimated total biomass (metric tons) of king crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata for 31 days during months 5 to

6 in the eastern Bering Sea. . . . . . . . . . . . 90

B-11. --Estimated total number (millions) of king crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata for 31 days during months 5 to

6 in the eastern Bering Sea. Values in parentheses

estimated from an average king crab size of 97.5 mm

carapace length. . . . . . . . . . . . . . . . . . .

B-12. --Estimated total biomass (metric tons) of snow

(Chionoecetes by opilio) and Tanner (c. bairdi) crabs 

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Values in parentheses indicate

cells where no prey size information was available.

(- = no samples taken.). . . . . . . . . . . . . .

B-13 .--Estimated total number (millions) of snow

(Chionoecetes opilio) and Tanner (C. bairdi) crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Values in parentheses indicate

cells where no prey size information was available.

(- = no samples taken.). . . . . . . . . . . . . .

B-14. --Size ranges of some commercially important prey

consumed by Pacific cod during months 5 to 9

in the eastern Bering Sea during 1987 to 1989. . .

91

92

93

94
Figure Page

B-l. --Diet composition of Pacific cod, in terms of

percent by weight, during months 5 to 9 by year and

predator size in the eastern Bering Sea.

N = number of stomachs. . . . . . . . . . . . . . . 95

B-2. --Size frequency of walleye pollock as prey in two

size groups of Pacific cod from 1987 to 1989 in the

eastern Bering Sea. . . . . . . . . . . . . . . . . 96

B-3 .--Size frequency of Chionoecetes bairdi as prey in

two size groups of Pacific cod from 1987 to 1989

in the eastern Bering Sea. . . . . . . . . . . . . . 97

B-4. --Size frequency of Chionoecetes opilio as prey in

two size groups of Pacific cod from 1987 to 1989

in the eastern Bering Sea. . . . . . . . . . . . . . 98

B-5. --Percent by weight of walleye pollock in the diet

of Pacific cod by sampling station during months 5 to

9 from 1987 to 1989. . . . . . . . . . . . . . . . . 99

B-6. --Percent by weight of Pacific herring in the diet

of Pacific cod by sampling station during months 5 to

9 from 1987 to 1989. . . . . . . . . . . . . . . . . 100

B-7. --Percent by weight of yellowfin sole, rock sole,

and flathead sole in the diet of Pacific cod by

sampling station during months 5 to 9 in 1989. . . . 101

B-8. --Percent by weight of king crab (Paralithodes

sp.) in the diet of Pacific cod by sampling station

during months 5 to 9 from 1987 to 1989. . . . . . . 102

B-9. --Percent by weight of red king crab and blue king

crab in the diet of Pacific cod by sampling station

during months 5 to 9 by year. . . . . . . . . . . . 103

B-10. --Percent by weight of Tanner crab, Chionoecetes

bairdi, in the diet of Pacific cod by sampling

station during months 5 to 9 from 1987 to 1989. . . 104

B-11. --Percent by weight of snow crab, Chionoecetes

opilio, in the diet of Pacific cod by sampling

station during months 5 to 9 from 1987 to 1989. . . 105
80

B-12. --Biomass and number of walleye pollock consumed

by three size groups of Pacific cod during months

5 to 9 from 1987 to 1989 in the eastern Bering Sea

by prey size. . . . . . . . . . . . . . . . . . . . 106

B-13 .--Biomass and number of yellowfin sole consumed

by three size groups of Pacific cod during months 5

to 9 from 1987 to 1989 in the eastern Bering Sea by

preysize..................... 107

B-14 .--Biomass and number of flathead sole consumed by

three size groups of Pacific cod during months 5 to

9 from 1987 to 1989 in the eastern Bering Sea by

preysize...............................................108

B-15 .--Biomass and number of rock sole consumed

by three size groups of Pacific cod during months 5

to 9 from 1987 to 1989 in the eastern Bering Sea by

preysize........................................... 109

B-16. --Biomass and number of Tanner crab, Chionoecetes

bairdi, consumed by three size groups of Pacific cod

during months 5 to 9 from 1987 to 1989 in the eastern

Bering Sea by prey size. . . . . . . . . . . . . . 110

B-17. --Biomass and number of snow crab, Chionoecetes

opilio, consumed by three size groups of Pacific cod

during months 5 to 9 from 1987 to 1989 in the eastern

Bering Sea by prey size. . . . . . . . . . . . . . 111
81

Table B-l. --Estimated biomass in metric tons of Pacific

cod in the eastern Bering Sea by cod size,

year, and stratum.
82

Table B-2 .--Mean percent by weight (%W) and standard error

(SE) of roundfish in the stomach contents of

Pacific cod by prey species, cod size group,

year, and strata during months 5 to 9 in the

eastern Bering Sea. ( * = no standard error

estimate since only one station was sampled.)
83

Table B-3 .--Mean percent by weight (%W) and standard error

(SE) of flatfish in the stomach contents of

Pacific cod by prey species, cod size group,

year, and strata during-months 5 to 9 in the

eastern Bering Sea.
84

Table B-4. --Mean percent by weight (%W) and standard error

(SE) of king crabs in the stomach contents of

Pacific cod by prey species, cod size group,

year, and strata during months 5 to 9 in the

eastern Bering Sea.
85

Table B-5. --Mean percent by weight (%W) and standard error

(SE) of snow (Chionoecetes opilio) and Tanner

(c. bairdi) crabs in the stomach contents of

Pacific cod by prey species, cod size group,

year.; and strata during months 5 to 9 in

the eastern Bering Sea. (* = no standard

error since only one station was sampled,

- = no samples taken.)
86

Table B-6. --Estimated total weight (metric tons) of roundfish

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea.
87

Table B-7. --Estimated total number (millions) of roundfish

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Parentheses indicate cells where

no prey size information was available.
88

Table B-8 .--Estimated total biomass

consumed by Pacific cod

group, year, and strata

eastern Bering Sea.

(metric tons) of flatfish

by prey species, cod size

during months 5 to 9 in the
89

Table B-9. --Estimated total number (millions) of flatfish

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Numbers in parentheses indicate

cells where no prey size information was available.
90

Table B-10.--Estimated total biomass (metric tons) of king crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata for 31 days during months 5 to

6 in the eastern Bering Sea.
91

Table B-11. --Estimated total number (millions) of king crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata for 31 days during months 5 to

6 in the eastern Bering Sea. Values in parentheses

estimated from an average king crab size of 97.5 mm

carapace length.
92

Table B-12. --Estimated total biomass (metric tons) of snow

(Chionoecetes opilio) and Tanner (C. bairdi) crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Values in parentheses indicate

cells where no prey size information was available.

(- = no samples taken.)
93

Table B-13. --Estimated total number (millions) of snow

(Chionoecetes opilio) and Tanner (c. bairdi) crabs

consumed by Pacific cod by prey species, cod size

group, year, and strata during months 5 to 9 in the

eastern Bering Sea. Values in parentheses indicate

cells where no prey size information was available.

(- = no samples taken.)
94

Table B-14. --Size ranges of some commercially important prey

consumed by Pacific cod during months 5 to 9

in the eastern Bering Sea during 1987 to 1989.
Figure B-l. --Diet composition of Pacific cod, in terms of

percent by weight, during months 5 to 9 by year and

predator size in the eastern Bering Sea.

N = number of stomachs.
96

Figure B-2. --Size frequency of walleye pollock as prey in two

size groups of Pacific cod from 1987 to 1989 in the

eastern Bering Sea.
97

Figure B-3. --Size frequency of Chionoecetes bairdi as prey in

two size groups of Pacific cod from 1987 to 1989

in the eastern Bering Sea.
98

 Figure B-4. --Size frequency of Chionoecetes opilio as prey in

two size groups of Pacific cod from 1987 to 1989

in the eastern Bering Sea.
Figure B-5. --Percent by weight of walleye pollock in the diet

of Pacific cod by sampling station during months 5

9 from 1987 to 1989.

to
Figure B-6.--Percent by weight of Pacific herring in the diet

of Pacific cod by sampling station during months 5 to

9 from 1987 to 1989.
Figure B-7. --Percent by weight of yellowfin sole, rock sole,

and flathead sole in the diet of Pacific cod by

sampling station during months 5 to 9 in 1989.
Figure B-8. --Percent by weight of king crab (Paralithodes

sp.) in the diet of Pacific cod by sampling station

during months 5 to 9 from 1987 to 1989.
Figure B-9. --Percent by weight of red king crab and blue king

crab in the diet of Pacific cod by sampling station

during months 5 to 9 by year.
104

Figure B-10. --Percent by weight of Tanner crab, Chionoecetes

bairdi, in the diet of Pacific cod by sampling

station during months 5 to 9 from 1987 to 1989.
Figure B-11. --Percent by weight of snow crab, Chionoecetes

opilio, in the diet of Pacific cod by sampling

station during months 5 to 9 from 1987 to 1989 .
106

Figure B-12. --Biomass and number of walleye pollock consumed

by three size groups of Pacific cod during months

5 to 9 from 1987 to 1989 in the eastern Bering Sea

by prey size.
107

Figure B-13. --Biomass and number of yellowfin sole consumed

by three size groups of Pacific cod during months 5

to 9 from 1987 to 1989 in the eastern Bering Sea by

prey size.
108

Figure-B-14. --Biomass and number of flathead sole consumed by

three size groups of Pacific cod during months 5 to

9 from 1987 to 1989 in the eastern Bering Sea by

prey size.
109

Predator size group (cm)

Figure B-15. --Biomass and number of rock sole consumed

by three size groups of Pacific cod during months 5

to 9 from 1987 to 1989 in the eastern Bering Sea by

prey size.
110

Figure B-16.--Biomass and number of Tanner crab, Chionoecetes

bairdi, consumed by three size groups of Pacific cod

during months 5 to 9 from 1987 to 1989 in the eastern

Bering Sea by prey size.
111

Figure B-17. --Biomass and number of snow crab, Chionoecetes

opilio, consumed by three size groups of Pacific cod

during months 5 to 9 from 1987 to 1989 in the eastern

Bering Sea by prey size.
THIS PAGE INTENTIONALLY LEFT BLANK
113

APPENDIX C

Yellowfin Sole, Alaska Plaice, Rock Sole, and Flathead Sole

Appendix C presents biomass, food habits, prey composition,

prey size, and prey consumption estimates for yellowfin sole,

Alaska plaice, rock sole, and flathead sole during months 5 through

9 from 1987, 1988, and 1989 in the eastern Bering Sea.

List of Tables

Table Page

C-l. --Yellowfin sole, flathead sole, and rock sole biomass

estimates, in metric tons, by year and stratum. . . . .

C-2 .--Mean percent-by weight (%W) and standard error (SE)

of snow crab in the diet of yellowfin sole, flathead

sole, and rock sole by year and stratum, months 5

through 9. Dash (-) indicates stratum where predator

was not sampled. . . . . . . . . . . . . . . . . . . .

118

119

C-3 .--Mean percent by weight (%W) and standard error (SE)

of Tanner crab in the diet of yellowfin sole, flathead

sole, and rock sole by year and stratum, months 5

through 9. Dash (-) indicates stratum where predator

was not sampled. . . . . . . . . . . . . . . . . . . . 120

C-4. --Mean percent by weight (%W) and standard error (SE)

of walleye pollock in the diet of yellowfin sole,

 flathead sole, and rock sole by year and stratum,

months 5 through 9. Dash (-) indicates stratum where

predator was not sampled. . . . . . . . . . . . . . . . 121

C-5. --Estimated snow crab biomass (metric tons) consumed by

yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled. . . . 122
114

C-6. --Estimated number of snow crab (millions) consumed by

yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled. . . . 123

C-7.--Estimated Tanner crab biomass (metric tons) consumed

by yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled. . . . 124

C-8. --Estimated number of Tanner crab (millions) consumed

by yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled. . . . 125

C-9. --Estimated walleye pollock biomass (metric tons)

consumed by yellowfin sole, flathead sole, and rock

sole by year and stratum, months 5 through 9. Numbers

in parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled. . . . 126

C-10. --Estimated number of walleye pollock (millions)

consumed by yellowfin sole, flathead sole, and rock

sole by year and stratum, months 5 through 9. Numbers

in parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash

(-) indicates stratum where predator was not sampled. . 127

C-11. --Estimated biomass (metric tons) of miscellaneous

species consumed by yellowfin sole and flathead sole

by year and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated using

conventional methods. . . . . . . . . . . . . . . . . 128

C-12. --Estimated number (millions) of miscellaneous

species consumed by yellowfin sole and flathead sole

by year and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated using

conventional methods . . . . . . . . . . . . . . . . . 129
115

List of Figures

Figure Page

C-1. --Annual diet composition of yellowfin sole in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples. . . . . . . . . . . . . . . . . . . . 130

C-2. --Annual diet composition of flathead sole in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples. . . . . . . . . . . . . . . . . . . 131

C-3. --Annual diet composition of rock sole in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples. . . . . . . . . . . . . . . . . . . . . 132

C-4. --Annual diet composition of Alaska plaice in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples. . . . . . . . . . . . . . . . . . . . 133

C-5. --Size frequency of snow crab prey found in yellowfin sole

during 1988 and 1989, flathead sole in 1989, and rock

sole in 1989 in the eastern Bering Sea, months 5

through........................................ 134

C-6. --Size frequency of Tanner crab prey found in yellowfin

sole in 1988 and 1989, and flathead sole in 1989 in

the eastern Bering Sea, months 5 through 9. . . . . . . 135

C-7. --Size frequency of walleye pollock prey found in

yellowfin sole and flathead sole in 1987-1989,

months 5 through 9. . . . . . . . . . . . . . . . . . . 136

C-8. --Percent by weight of snow crab in the diet of

yellowfin sole in 1988, and flathead sole and rock

sole in 1989, by sampling station in the eastern

Bering Sea, months 5 through 9. . . . . . . . . . . . . 137

C-9. --Percent by weight of Tanner crab in the diet of

yellowfin sole in 1987 and 1989 by sampling station in

the eastern Bering Sea, months 5 through 9. . . . . . . 138

C-10. --Percent by weight of Tanner crab in the diet of

flathead sole, 1987-1989, by sampling station in the

eastern Bering Sea, months 5 through 9. . . . . . . . 139

C-11. --Percent by weight of walleye pollock in the diet of

yellowfin sole, 1987-1989, by sampling station in the

eastern Bering Sea, months 5 through 9. . . . . . . . 140
116

C-12. --Percent by weight of walleye pollock in the diet of

flathead sole, 1987-1989, by sampling station in the

eastern Bering Sea, months 5 through 9. . . . . . . .

C-13.--Percent by weight of rock sole in the diet of

yellowfin sole in 1989, and Paralithodes sp. in the

diet of yellowfin sole in 1988 by sampling station in

the eastern Bering Sea, months 5 through 9. . . . . .

C-14 .--Biomass (metric tons) and number (billions) of snow

crab consumed by yellowfin sole in 1988, and flathead

sole and rock sole in 1989, by prey size, in the

eastern Bering Sea, months 5 through 9. . . . . . . .

C-15. --Biomass (metric tons) and number (billions) of

Tanner crab consumed by yellowfin sole in 1987 and

1989, months 5 through 9. . . . . . . . . ... . . . .

C-16. --Biomass (metric tons) and number (billions) of

Tanner crab consumed by flathead sole, 1987-1989,

by prey size in the eastern Bering Sea, months 5

through..............................................

C-17. --Biomass (metric tons) and number (billions) of

Tanner crab consumed by rock sole in 1987 and 1988,

by prey size in the eastern Bering Sea, months 5

through 9. Note: 1987 Numbers reported in millions. .

C-18. --Biomass (metric tons) and number (billions) of

walleye pollock consumed by yellowfin sole, 1987-

1989, by prey size in the eastern Bering Sea, months

5 through 9............. .............................

C-19. --Biomass (metric tons) and number (billions) of

walleye pollock consumed by flathead sole, 1987-

1989, by prey size in the eastern Bering Sea, months

5 through 9............. .............................

C-20. --Biomass (metric tons) and number (billions) of

walleye pollock consumed by rock sole in 1987 by

prey size in the eastern Bering Sea, months 5

through 9.....................................

C-21. --Biomass (metric tons) and number (billions) of rock

sole consumed by yellowfin sole in 1988 and 1989, by

prey size in the eastern Bering Sea, months 5

through 9.............. .......................

C-22. --Biomass (metric tons) and number (billions) of rock

sole consumed by flathead sole in 1987 and 1988, by

prey size in the eastern Bering Sea, months 5

through 9.............. .......................

141

142

143

144

145

146

147

148

149

150

151
117

C-23 .--Biomass (metric tons) and number (millions) of

Paralithodes sp. consumed by yellowfin sole in 1988,

and biomass and numbers (billions) of flathead sole

consumed by flathead sole in 1988 by prey size in the

eastern Bering Sea, months 5 through 9. . . . . . . . 152
118

Table C-l. --Yellowfin sole, flathead sole, and rock sole biomass

estimates, in metric tons, by year and stratum.
119

Table C-2 .--Mean percent by weight (%W) and standard error (SE)

of snow crab in the diet of yellowfin sole, flathead

sole, and rock sole by year and stratum, months 5

through 9. Dash (-) indicates stratum where predator

was not sampled.
120

Table C-3. --Mean percent by weight (%W) and standard error (SE)

of Tanner crab in the diet of yellowfin sole, flathead

sole, and rock sole by year and stratum, months 5

through 9. Dash (-) indicates stratum where predator

was not sampled.
121

Table C-4 .--Mean percent by weight (%W) and standard error (SE)

of walleye pollock in the diet of yellowfin sole,

flathead sole, and rock sole by year and stratum,

months 5 through 9. Dash (-) indicates stratum where

predator was not sampled.
122

Table C-5.--Estimated snow crab biomass (metric tons) consumed by

yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled.
123

Table C-6.--Estimated number of snow crab (millions) consumed by

yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled.
Table C-7.--Estimated Tanner crab biomass (metric tons) consumed

by yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled.
125

Table C-9. --Estimated number of Tanner crab (millions) consumed

by yellowfin sole, flathead sole, and rock sole by year

and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled.
126

Table C-9. --Estimated walleye pollock biomass (metric tons)

consumed by yellowfin sole, flathead sole, and rock

sole by year and stratum, months 5 through 9. Numbers

in parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash (-)

indicates stratum where predator was not sampled.
127

Table C-10. --Estimated number of walleye pollock (millions)

consumed by yellowfin sole, flathead sole, and rock

sole by year and stratum, months 5 through 9. Numbers

in parentheses correspond to year-stratum combinations

where number consumed could not be calculated. Dash

(-) indicates stratum where predator was not sampled.
128

Table C-11. --Estimated biomass (metric tons) of miscellaneous

species consumed by yellowfin sole and flathead sole

by year and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated using

conventional methods.
129

Table C-12. --Estimated number (millions) of miscellaneous

species consumed by yellowfin sole and flathead sole

by year and stratum, months 5 through 9. Numbers in

parentheses correspond to year-stratum combinations

where number consumed could not be calculated using

conventional methods.
130

Figure C-l.--Annual diet composition of yellowfin sole in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples.
131

Figure C-2. --Annual diet composition of flathead sole in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples.
132

Figure C-3. --Annual diet composition of rock sole in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N=number of

stomach samples.
Figure C-4. --Annual diet composition of Alaska plaice in terms of

percent by weight, months 5 through 9, by predator

size in the eastern Bering Sea, 1987-1989. N-number of

stomach samples.
134

Figure C-5. --Size frequency of snow crab prey found in yellowfin

sole during 1988 and 1989, flathead sole in 1989, and

rock sole in 1989 in the eastern Bering Sea, months 5

through 9.
135

Figure C-6. --Size frequency of Tanner crab prey found in yellowfin

sole in 1988 and 1989, and flathead sole in 1989 in

the eastern Bering Sea, months 5 through 9.
136

Figure C-7.--Size frequency of walleye pollock prey found in

yellowfin sole and flathead sole in 1987-1989,

months 5 through 9.
Figure C-8. --percent by weight of snow crab in the diet of

yellowfin sole in 1988, and flathead sole and rock

sole in 1989, by sampling station in the eastern

Bering Sea, months 5 through 9.
138

Figure C-9. --Percent by weight of Tanner crab in the diet of

yellowfin sole in 1987 and 1989 by sampling station in

the eastern Bering Sea, months 5 through 9.
Figure C-10. --percent by weight of Tanner crab in the diet of

flathead sole, 1987-1989, by sampling station in the

eastern Bering Sea, months 5 through 9.
Figure C-11 .--Percent by weight of walleye pollock in the diet of

yellowfin sole, 1987-1989, by sampling station in the

eastern Bering Sea, months 5 through 9.
Figure C-12. --Percent by weight of walleye pollock in the diet of

flathead sole, 1987-1989, by sampling station in the

eastern Bering Sea, months 5 through 9.
142

Figure C-13.--Percent by weight of rock sole in the diet of

yellowfin sole in 1989, and Paralithodes sp. in the

diet of yellowfin sole in 1988 by sampling station in

the eastern Bering Sea, months 5 through 9.
143

Figure C-14. --Biomass (metric tons) and number (billions) of snow

crab consumed by yellowfin sole in 1988, and flathead

sole and rock sole in 1989, by prey size, in the

eastern Bering Sea, months 5 through 9.
144

Figure C-15. --Biomass (metric tons) and number (billions) of

Tanner crab consumed by yellowfin sole in 1987 and

1989, months 5 through 9.
145

Figure C-16.--Biomass (metric tons) and number (billions) of

Tanner crab consumed by flathead sole, 1987-1989,

by prey size in the eastern Bering Sea, months 5

through 9.
146

Figure C-17. --Biomass (metric tons) and number (billions) of

Tanner crab consumed by rock sole in 1987 and 1988,

by prey size in the eastern Bering Sea, months 5

through 9. Note: 1987 Numbers reported in millions.
Figure C-18. --Biomass (metric tons) and number (billions) of

walleye pollock consumed by yellowfin sole, 1987-

1989, by prey size in the eastern Bering Sea, months

5 through 9.
148

Figure C-19.--Biomass (metric tons) and number (billions) of

walleye pollock consumed by flathead sole, 1987-

1989, by prey size in the eastern Bering Sea, months

5 through 9.
149

Figure C-20. --Biomass (metric tons) and number (billions) of

walleye pollock consumed by rock sole in 1987 by

prey size in the eastern Bering Sea, months 5

through 9.
150

Figure C-21. --Biomass (metric tons) and number (billions) 'of rock

sole consumed by yellowfin sole in 1988 and 1989, by

prey size in the eastern Bering Sea, months 5

through 9.
151

Figure C-22. --Biomass (metric tons) and number (billions) of rock

sole consumed by flathead sole in 1987 and 1988, by

prey size in the eastern Bering Sea, months 5

through 9.
152

Figure C-23. --Biomass (metric tons) and number (millions) of

Paralithodes sp. consumed by yellowfin sole in 1988,

and biomass and numbers (billions) of flathead sole

consumed by flathead sole in 1988 by prey size in the

eastern Bering Sea, months 5 through 9.
153

APPENDIX D

Greenland Turbot

Appendix D presents biomass, food habits, prey composition,

prey size, and prey consumption estimated for Greenland turbot

during months 5 to 9, from 1987, 1988, and 1989 in the eastern

Bering Sea.

List of Tables

Table Page

D-l. --Biomass (by predator size, stratum, and year) of

Greenland turbot in the eastern Bering Sea from

1987 through 1989 (data based on the bottom trawl

survey conducted by the PACE Division of the Alaska

Fisheries Science Center,NMFS)......................... 155

D-2. --Mean percent by weight and standard error

(%W + S.E.) of walleye pollock in the diet of

Greenland turbot by predator size, stratum,

and year in the eastern Bering Sea (sampled

in months 5 to 9). (- = no samples taken.)........... 156

D-3. --Estimated biomass of walleye pollock consumed

by Greenland turbot in the eastern Bering Sea

(by predator size, stratum, and year).

(- = no samples taken.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

D-4. --Estimated number (millions) of walleye pollock

consumed by Greenland turbot in the eastern

Bering Sea (by predator size, stratum, and year).

(- = no samples taken.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

D-5. --Estimated biomass and number of miscellaneous

commercial prey consumed by Greenland turbot

(sampled in months 5-9) by prey item, predator

size group, year, and stratum. Numbers in

parentheses indicate cells with no prey size

information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
154

List of Figures

Figures Page

D-l. --Diet composition of Greenland turbot, in terms

of percent by weight, during months 5 to 9 by

year and predator size in the eastern Bering

Sea, 1987-89. N = sample size........................ 160

D-2. --Percent by weight of walleye pollock in the

diet of Greenland turbot in the eastern Bering

Sea, 1987-89 (months 5 to 9) . . . . . . . . . . . . . . . . . . . . . . . . . . 161

D-3. --Size frequency distributions of walleye pollock

consumed by Greenland turbot in the eastern

Bering Sea by year, 1987-89 . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

D-4. --Estimated biomass and number of walleye pollock

consumed by Greenland turbot in the eastern

Bering Sea by year, 1987-89 (months 5 to 9)........... 163
155

Table D-l. --Biomass (by predator size, stratum, and year) of

Greenland turbot in the eastern Bering Sea from 1987

through 1989 (data based on the bottom trawl survey

conducted by the RACE Division of the Alaska

Fisheries Science Center, NMFS).
156

Table D-2. --Mean percent by weight and standard error (%W + S.E.)

of walleye pollock in the diet of Greenland turbot by

predator size, stratum, and year in the eastern

Bering Sea (sampled in months 5 to 9). (- = no

samples taken.)
157

Table D-3. --Estimated biomass of walleye pollock consumed by

Greenland turbot in the eastern Bering Sea (by

predator size, stratum, and year). (- = no samples

taken.)
158

Table D-4.--Estimated number (millions) of walleye pollock

consumed by Greenland turbot in the eastern Bering

Sea (by predator size, stratum, and year). (- = no

samples taken.)
159

Table D-5 .--Estimated biomass and number of miscellaneous

commercial prey consumed by Greenland turbot (sampled

in months 5-9) by prey item, predator size group,

year, and stratum. Numbers in parentheses indicate

cells with no prey size information.
160

Figure D-l. --Diet composition of Greenland turbot, in terms of

percent by weight, during months 5 to 9 by year and

predator size in the eastern Bering Sea, 1987-89.

N = sample size.
161

Figure D-2. --Percent by weight of walleye pollock in the diet of

Greenland turbot in the eastern Bering Sea, 1987-89

(months 5 to 9).

163

Figure D-4. --Estimated biomass and number of walleye pollock

consumed by Greenland turbot in the eastern Bering

Sea by year, 1987-89 (months 5 to 9).
THIS PAGE INTENTIONALLY LEFT BLANK
165

APPENDIX E

Arrowtooth flounder

Appendix E presents biomass, food habits, prey composition,

prey size, and prey consumption estimates for Pacific cod during

months 5 to 9, from 1987, 1988, and 1989 in the eastern Bering Sea.

List of Tables

Table

E-l. --Biomass (by predator size, stratum, and year) of

arrowtooth flounder in the eastern Bering Sea from

1987 through 1989 (data based on the bottom trawl

survey conducted by the RACE Division of the Alaska

Fisheries Science Center, NMFS........................

E-2 .--Mean percent by weight and standard error (%W + SE)

of walleye pollock in the diet of arrowtooth flounder

by predator size, stratum, and year in the eastern

Bering Sea (sampled in months 5 to 9). (- = no

samples taker.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

E-3 .--Mean percent by weight and standard error (%W + SE)

of miscellaneous commercial prey consumed by

arrowtooth flounder (sampled in months 5-9) by prey

item, predator size group, year, and stratum..........

E-4. --Estimated biomass (metric tons) of walleye pollock

consumed by arrowtooth flounder in the eastern

Bering Sea (by predator size, stratum, and year).

(- = no samples taken.) . . . . . . . . . . . . . . . . . . . . . . . . . . .

E-5. --Estimated number (millions) of walleye pollock

consumed by arrowtooth flounder in the eastern

Bering Sea (by predator size, stratum, and year)..

(- = no samples taken.) . . . . . . . . . . . . . . . . . . . . . . . . .

E-6. --Estimated biomass (metric tons) and number

(millions) of miscellaneous commercial prey

consumed by arrowtooth flounder (sampled in

months 5-9) by prey item, predator size group,

year, and stratum. Numbers in parentheses

indicate cells with no prey size information..........

Page

167

168

169

170

171

172
166

List of Figures

Figures Page

E-l. --Diet composition of arrowtooth flounder, in

terms of percent by weight, during months 5 to 9

by year and predator size in the eastern Bering

Sea, 1987-89. N = sample size........................ 173

E-2. --Percent by weight of walleye pollock in the diet

of arrowtooth flounder in the eastern Bering Sea

by year, 1987-89 (months 5 to 9)...................... 174

E-3. --Percent by weight of arrowtooth flounder, rock

sole, flathead sole in the diet of arrowtooth

flounder in the eastern Bering Sea in 1989 (months

5 to 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

E-4. --Percent by weight of Pacific herring in the diet

of arrowtooth flounder in the eastern Bering Sea

in 1987 (months 5 to 9) . . . . . . . . . . . . . . . . . . . . 176

E-5. --Size frequency distributions of walleye pollock

consumed by three size groups of arrowtooth

flounder in the eastern Bering Sea by year,

1987-89..................... . . . . . . . . . . . . . . . . 177

E-6. --Estimated biomass and number of walleye pollock

consumed by three size groups of arrowtooth

flounder in the eastern Bering Sea by year,

1987-89 (months 5 to 9) . . . . . . . . . . . . . . . . . . . . . . 178
167

Table E-l .--Biomass (by predator size, stratum, and year) of

arrowtooth flounder in the eastern Bering Sea from

1987 through 1989 (data based on the bottom trawl

survey conducted by the PACE Division of the Alaska

Fisheries Science Center, NMFS).
168

Table E-2 .--Mean percent by weight and standard error (%W + SE)

of walleye pollock in the diet of arrowtooth flounder

by predator size, stratum, and year in the eastern

Bering Sea (sampled in months 5 to 9). (- = no

samples taken.)

* Only one station was sampled.
169

Table E-3 .--Mean percent by weight and standard error (%W + SE)

of miscellaneous commercial prey consumed by

arrowtooth flounder (sampled in months 5-9) by prey

item, predator size group, year, and stratum.
170

Table E-4.--Estimated biomass (metric tons) of walleye pollock

consumed by arrowtooth flounder in the eastern

Bering Sea (by predator size, stratum, and year).

(- = no samples taken.)
171

Table E-5. --Estimated number (millions) of walleye pollock

consumed by arrowtooth flounder in the eastern Bering

Sea (by predator size, stratum, and year). (- = no

samples taken.)
172

Table E-6 .--Estimated biomass (metric tons) and number (millions)

of miscellaneous commercial-prey consumed by

arrowtooth flounder (sampled in months 5-9) by prey

item, predator size group, year, and stratum. Numbers

in parentheses indicate cells with no prey size

information.
173

Figure E-l. --Diet composition of arrowtooth flounder, in terms of

percent by weight, during months 5 to 9 by year and

predator size in the eastern Bering Sea, 1987-89.

N = sample size.
Figure E-2. --Percent by weight of walleye pollock in the diet of

arrowtooth flounder in the eastern Bering Sea by year,

1987-89 (months 5 to 9).
175

Figure E-3. --Percent by weight of arrowtooth flounder, rock sole

flathead sole in the diet of arrowtooth flounder in

the eastern Bering Sea in 1989 (months 5 to 9).
176

Figure E-4. --Percent by weight of Pacific herring in the diet of

arrowtooth flounder in the eastern Bering Sea in 1987

(months 5 to 9).
Figure E-5. --Size frequency distributions of walleye pollock

consumed by three size groups of arrowtooth flounder

in the eastern Bering Sea by year, 1987-89.
178

Figure E-6.--Estimated biomass and number of walleye pollock

consumed by three size groups of arrowtooth flounder

in the eastern Bering Sea by year, 1987-89 (months 5

to 9).
179

APPENDIX F

Pacific Halibut

Appendix F presents biomass, food habits, prey composition,

prey size, and prey comsumption estimates for Pacific halibut

during months 5 to 9 in 1989 in the eastern Bering Sea.

List of Tables

Table Page

F-l. --Estimated biomass in metric tons of Pacific

halibut for 1989 in the eastern Bering Sea by

halibut size group and stratum. . . . . . . . . . . . 181

F-2. --Mean percent by weight (%W) and standard error

(SE) of fish in the stomach contents of Pacific

halibut by prey species, halibut size group,

and stratum during months 5 to 9 in 1989 in

the eastern Bering Sea. . . . . . . . . . . . . . . . 182 

F-3. --Mean percent by weight (%W) and standard error

(SE) of Tanner (Chionoecetes bairdi) and snow

(C. opilio) crab in the stomach contents of

Pacific halibut by prey species, halibut size group,

and stratum during months 5 to 9 in 1989 in

the eastern Bering Sea. . . . . . . . . . . . . . . . 183

F-4 .--Estimated total biomass (metric tons) and number

(millions) of fish consumed by Pacific halibut by

prey species, halibut size group, and stratum during

months 5 to 9 in 1989 in the eastern Bering Sea . . . 184

F-5. --Estimated total biomass (metric tons) and number

(millions) of Tanner (Chionoecetes bairdi) and snow

(C. opilio) crab consumed by Pacific halibut by prey

species, halibut size group, and stratum during

months 5 to 9 in 1989 in the eastern Bering Sea . . . 185

F-6. --Size range of fish consumed by Pacific halibut by

prey species, and halibut size group during months

5 to 9 in 1989 in the eastern Bering Sea. . . . . . . 186
180

List of Figures

Figure Page

F-l. --Diet composition of Pacific halibut, in terms

of percent by weight and predator size during

months 5 to 9 in the eastern Bering Sea in

1989. N= number of stomachs. . . . . . . . . . . . . 187

F-2.--Size frequency of walleye pollock consumed

Pacific halibut during months 5 to 9 in the

by

eastern Bering Sea in 1989. . . . . . . . . . . . . . 188

F-3.--Size frequency of C. opilio and C. bairdi

consumed by Pacific halibut during months 5

to 9 in the eastern Bering Sea in 1989. . . . . . . . 189

F-4 .--Percent by weight of walleye pollock,

flathead sole and yellowfin sole in the diet

of Pacific halibut by sampling station

during months 5 to 9 in 1989. . . . . . . . . . . . . 190

F-5.-- Percent by weight of C. opilio and C. bairdi

in the diet of Pacific halibut by sampling

station during months 5 to 9 in 1989. . . . . . . . . 191

F-6.--Biomass and number of walleye pollock,

C. opilio and C. bairdi consumed by Pacific

halibut during months 5 to 9 in the eastern

Bering Sea by prey size in 1989. . . . . . . . . . . 192
181

Table F-l. --Estimated biomass in metric tons of Pacific halibut

for 1989 in the eastern Bering Sea by halibut size

group and stratum.
182

Table F-2 .--Mean percent by weight (%W) and standard error (SE) of

fish in the stomach contents of Pacific halibut by

prey species, halibut size group, and stratum during

months 5 to 9 in 1989 in the eastern Bering Sea.
183

Table F-3 .--Mean percent by weight (%W) and standard error (SE) of

Tanner(Chionoecetes bairdi) and snow (C. opilio) crab

in the stomach contents of Pacific halibut by

prey species, halibut size group, and stratum during

months 5 to 9 in 1989 in the eastern Bering Sea.
184

Table F-4 .--Estimated total biomass (metric tons) and number

(millions) of fish consumed by Pacific halibut by prey

species, halibut size group, and stratum during months

5 to 9 in 1989 in the eastern Bering Sea.
185

Table F-5. --Estimated total biomass (metric tons) and number

(millions) of Tanner (Chionoecetes bairdi) and snow

(C. opilio) crab consumed by Pacific halibut by prey

species, halibut size group, and stratum during months

5 to 9 in 1989 in the eastern Bering Sea.
186

Table F-6.--Size range of fish consumed by Pacific halibut by

prey species, and halibut size group during months 5 to

9 in 1989 in the eastern Bering Sea.
187

Figure F-l. --Diet composition of Pacific halibut, in terms of

percent by weight and predator size during months 5 to

9 in the eastern Bering Sea in 1989. N= number of

stomachs.
188

Figure F-2. --Size frequency of walleye pollock consumed by Pacific

halibut during months 5 to 9 in the eastern Bering Sea

in 1989.
189

Figure F-3. --Size frequency of C. opilio and C. bairdi consumed by

Pacific halibut during months 5 to 9 in the eastern

Bering Sea in 1989.
Figure F-4. --Percent by weight of walleye pollock, flathead sole

and yellowfin sole in the diet of Pacific halibut by

sampling station during months 5 to 9 in 1989.
191

Figure F-5. --Percent by weight of C. opilio and C. bairdi in the

diet of Pacific halibut by sampling station during

months 5 to 9 in 1989.

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. 

AFSC10 KINOSHITA, R. K., and J. M. TERRY. 1993. Oregon, Washington, and Alaska exports of edible fishery

products, 1991, 47 p. NTIS No. PB93-159101.

9 KARINEN, J. F., M. M. BABCOCK, D. W. BROWN, W. D. MACLEOD, JR., L. S. RAMOS, and J.W.

SHORT. 1993. Hydrocarbons in intertidal sediments and mussels from Prince William Sound, Alaska,

1977-1980: Characterization and probable sources, 69 p. NTIS No. PB93-159093.

 8 WING, B. L. 1993. Winter oceanographic conditions in the eastern Gulf of Alaska, January-February

1986, 53 p. NTIS No. PB93-158335.

7 ARMISTEAD, C. E., and D. G. NICHOL. 1993. 1990 bottom trawl survey of the eastern Bering

Sea and continental shelf, 190 p. NTIS No. PB93-156677.

6 WOLOTIRA, R. J., JR., T. M. SAMPLE, S. F. NOEL, and C. R. ITEN. 1993. Geographic and bathymetric

distributions for many commercially important fishes and shellfishes off the West Coast of North America,

based on research survey and commercial catch data, 1912-84, 184 p. NTIS No. PB93-167682. 

5 GUTTORMSEN, M., R. NARITA, J. GHARRETT, G. TROMBLE, and J. BERGER. 1992. Summary

of observer sampling of domestic groundfish fisheries in the northeast Pacific Ocean and Eastern Bering

Sea, 1990, 281 p. NTIS No. PB93-159085.

4 GUTTORMSEN, M., R. NARITA, and J. BERGER. 1992. Summary of U. S. observer sampling

of joint venture fisheries in the northeast Pacific Ocean and Eastern Bering Sea, 1990, 78 p. NTIS No.

PB93-127546.

3 JOHNSON, P. A., S. D. RICE, and M. M. BABCOCK (compilers). 1992. Impacts of oil pollution

and Prince William Sound studies: Bibliography of 1960-91 publications and reports, Auke Bay Laboratory,

98 p. NTIS No. PB93-114064.

2 KAJIMURA, H., and E. SINCLAIR. 1992. Fur seal investigations, 1990, 192 p. NTIS No. PB93-

109080.

1 MERRICK, R. L., D. G. CALKINS, and D. C. MCALLISTER. 1992. Aerial and ship-based surveys

of Steller sea lions (Eumetopias jubatus) in southeast Alaska, the Gulf of Alaska, and Aleutian Islands

during June and July 1991, 41 p. NTIS No. PB92-235928. 

F/NWC216 ZENGER, H. H., JR., and M. F. SIGLER. 1992. Relative abundance of Gulf of Alaska sablefish

and other groundfish based on National Marine Fisheries Service longline surveys, 1988-90, 

103 p. NTIS No. PB92-222843.

215 KINOSHITA, R. K., B. M. K. BROOKE, L. E. QUEIROLO, and J. M. TERRY. 1992. Economic status of

the groundfish fisheries off Alaska, 1990, 99 p. NTIS No. PB92-187699.

214 ANTONELIS, G. A. 1992. Northern fur seal research techniques manual, 47 p. NTIS No. PB92-191824.