NOAA Technical Memorandum NMFS-AFSC-41

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

August 1994

by

M. Zimmermann, P. Goddard, and T. M. Sample

Results of the 1991 U.S.-U.S.S.R.

Cooperative Bottom Trawl Survey of

the Eastern and Western Bering Sea

Continental Shelf
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:

Zimmermann, M., P. Goddard, and T.M. Sample. 1994. Results of the

1991 U.S.-U.S.S.R. cooperative bottom trawl survey of the eastern and

western Bering Sea continental shelf. U.S. Dep. Commer., NOAA

Tech. Memo. NMFS-AFSC-41, 178 p. 

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

National Marine Fisheries Service, NOAA.
August 1994

NOAA Technical Memorandum NMFS-AFSC-41

by

Results of the 1991 U.S.-U.S.S.R.

Cooperative Bottom Trawl Survey of

the Eastern and Western Bering Sea

Continental Shelf

Alaska Fisheries Science Center

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

Seattle, WA 98115-0070

U.S. DEPARTMENT OF COMMERCE

Ronald H. Brown, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Under Secretary and Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Administrator for Fisheries

M. Zimmermann, P. Goddard, and T. M. Sample
This document is available to the public through:

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, VA 22161
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This document is being made available in .PDF format for the convenience of users; however, the 

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iii

ABSTRACT

A cooperative bottom trawl survey of the Bering Sea was

conducted by the Alaska Fisheries Science Center (AFSC) of the

United States and the Pacific Research Institute of Fisheries and

Oceanography of the U.S.S.R. aboard the Soviet research vessel

Novodrutsk during May-June 1991. The primary purpose of this

survey was to assess the distribution, abundance, and biological

condition of groundfish resources over the continental shelf in

both the eastern and western Bering Sea. An independent bottom

trawl survey of the central and southeastern Bering Sea

continental shelf was also conducted by the AFSC during JuneSeptember 1991 aboard U.S. research vessels.

Results summarizing geographic distribution, abundance

estimates, and size composition are presented for the principal

species of fish encountered. The distributions of commercially

important crab species are also shown. Comparisons are made

among results of this cooperative survey, the 1991 U.S. survey,

and earlier surveys from the areas commonly fished in the eastern

Bering Sea. The appendices include station and catch

information, abundance, size, and age data.
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V

CONTENTS

Page

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

Survey Methods ......... Survey Area and Sampling Design.............. ..................

Vessel and Fishing Gear

Collection and Processing of Samples...... Data Analysis ................

Results of the Survey ............... Hauls and Data Collected ...........

Environmental Conditions ........... Relative Importance of Major Taxonomic Groups

Abundance of Major Fish Groups . ....

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. . Abundance, Distribution, and Size Composition of

Principal Fish Species .............. Walleye pollock ............ Pacific cod .............. Yellowfin sole ............. Rock sole ............... Hippoglossoides spp. .......... Alaska plaice ............. Atheresthes spp. ............ Pacific halibut ............ Greenland turbot ............ Distribution of Major Crab Species ........ Snow crab (C. opilio) ......... Snow crab (C. bairdi) ......... Red king crab ............. Blue king crab .............

Discussion ......................

Acknowledgments ....................

Citations 

Appendix A.

Appendix B.

Appendix C.

Appendix D.

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Station, Haul, and Catch Data ......

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Abundance Estimates for Principal Fish Species 

Population Estimates by Sex and Size Groups

for Principal Fish Species . . . . . . . . . . .

Age-Length Keys for Walleye Pollock

1

 3

3 . 9 . 9

12

16

16

17

17

26

36

36

45

51

61

66

69

74

79

84

89

89

89

89

89

9 4

100

101

103

125

143

and Pacific Cod . . . . . . . . . . . . . . . . 165
INTRODUCTION

The Resource Assessment and Conservation Engineering (RACE)

Division of the Alaska Fisheries Science Center (AFSC) and the

Pacific Research Institute of Fisheries and Oceanography (TINRO)

of the U.S.S.R. (now known as the Russian Federation) conducted a

cooperative bottom trawl survey of the eastern and western Bering

Sea shelf from 11 May through 25 June 1991. This survey was

conducted aboard the Soviet research vessel Novodrutsk, in

complement to the annual independent U.S. bottom trawl survey of

the eastern Bering Sea shelf. While the U.S. survey sampled east

of the U.S.-U.S.S.R. Convention Line, the cooperative U.S.-

U.S.S.R. survey sampled both U.S. waters and areas west of the

Convention Line in the Soviet Exclusive Economic Zone (EEZ).

Five U.S. scientists participated in survey operations conducted

aboard the Soviet vessel.

Systematic bottom trawl surveys, designed to assess the

biological condition of crab and groundfish species in the

eastern Bering Sea, have been conducted by the U.S. annually

since the early 1970s. Initial surveys were limited to Bristol

Bay and the central waters of the eastern Bering Sea shelf. The

first large-scale survey, conducted in 1975, sampled continental

shelf and slope waters from Unimak Pass north to approximately

62°N lat. and east of the Alaska mainland. Expansive surveys

have been conducted annually by the United States since 1979,

covering a large portion of the eastern Bering Sea shelf.

However, information on the abundance, distribution, and
2

biological characteristics of crab and groundfish assemblages

occurring in the western portion of the Bering Sea has been

limited.

The Soviet scientists have conducted fisheries research in

the eastern and western Bering Sea since 1958 under a program

entitled the "Bering Sea Comprehensive Scientific-Commercial

Expedition" (Moiseev 1963). Information collected during many of

these surveys has not been available to U.S. scientists or has

been of limited value since U.S. and Soviet methods of collecting

station and catch data have differed significantly (Sample and

Nichol 1994). In 1990, an attempt was made to standardize data

collections by utilizing U.S. sampling methodology aboard a

Soviet research vessel conducting the cooperative U.S.-U.S.S.R.

bottom trawl survey (Sample and Nichol 1994). The 1990 survey

provided the first complete set of standardized data from both

the western and eastern Bering Sea.

This report describes the survey methodology

the results of the 1991 cooperative U.S.-U.S.S.R.

survey of the Bering Sea shelf. Complete results

and summarizes

bottom trawl

of the 1991

U.S. survey are presented in Goddard and Zimmermann (1993).

The specific objectives of this report are to

1.

2.

3.

Describe the geographical distribution of important

demersal resources in the eastern and western Bering

Sea during the survey period;

Describe biological characteristics and relative

abundance of ecologically important species, and;

Compare the results of this cooperative survey with

the results of the 1991 U.S. survey and earlier

U.S.-U.S.S.R. cooperative bottom trawl surveys.
3

SURVEY METHODS

Survey Area and Sampling Design

The area surveyed by the research vessel Novodrutsk covered

the Bering Sea continental shelf from the Alaska coast west to

the 200 m isobath and north from the Alaska Peninsula to

approximately St. Matthew Island (Fig. 1). The survey also

extended into Russian shelf waters in the Gulf of Anadyr and west

along the Siberian coast. Most of these areas were also sampled

during the 1990 U.S. -U.S.S.R. cooperative survey. The 1991

survey, however, extended farther west and included the shelf

waters in the Olyutorski Gulf.

For sampling and analytical purposes, the survey area was

divided into 11 subareas (Fig. 2). The eastern portion of the

Bering Sea shelf was further divided into three depth zones

delineated by the 50 m (Subareas 1 and 2), 100 m (Subareas 3 and

4) I and 200 m (Subareas 5, 6, and 9) isobaths. Because separate

oceanic domains influence fish distributions (Kinder and

Schumacher 1981), stratifying data among these subareas may

reduce the variance of population estimates. Detailed

bathymetric data were not available for the western portion of

the survey area; therefore, the data recorded on the Soviet side

of the U.S.-U.S.S.R. Convention Line were grouped into lessspecific depth zones. Subarea 14 includes all depths less than

100 m, Subarea 15 includes depths between 100 m and 200 m, and

Subareas 16 and 17 include depths less than 200 m. These
Figure l.--Survey area and station locations sampled by the RV Novodrutsk during the

1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelf.

6

subareas were grouped into three main regions for reporting and

comparative purposes as follows:

1) the standard U.S. shelf area (Subareas l-6) which

consisted of the combined region of the central and

southeastern Bering Sea;

2) the north shelf area which extends from 61° N lat. to

St. Lawrence Island and east to the U.S.-U.S.S.R.

Convention Line, only part of which (Subarea 9) was

covered in this survey;

3) the western shelf area (Subareas 14-17) including shelf

waters from the Gulf of Anadyr west into Olyutorski

Gulf. The northern portion of Subarea 14 was not

sampled due to sea ice conditions (Fig. 3) and time

constraints prevented the complete sampling of

Subarea 16.

Sampling site locations in most subareas were based on a

schematic 20 x 20 nautical mile grid system that was established

by AFSC scientists during previous U.S. surveys. Due to time

constraints, only alternate north-south columns spaced 40 miles

apart were sampled. All stations sampled in the standard U.S.

shelf were later sampled by the independent U.S. bottom trawl

survey. The grid sampling scheme was not applied to Subareas 16

and 17 due to the narrowness of the shelf.

The total survey area encompassed approximately 587,878 km2

(Table 1). The standard U.S. area accounted for approximately

79% of the total area, the west shelf 19%, and the north shelf

2%. An average of one station for every 2,259 km2

 was sampled

over the entire survey area. Sampling intensity was lowest in

Subarea 16 (1 sta./5,136 km2) and highest in Subarea 17

(1 sta./907 km2).
7

Table 1 .--Size of subareas and sampling effort during the 1991

cooperative U.S. -U.S.S.R. bottom trawl survey of the

Bering Sea shelf.

The survey began in Bristol Bay on 11 May 1991 and continued

west and north to the U.S.-U.S.S.R. Convention Line. Fishing in

U.S. waters (Subareas l-6 and 9) was completed on 8 June. Due to

extensive ice coverage in late May and early June, the vessel was

unable to proceed north to Subareas 14 and 15 as planned

(Fig. 3). All fishing operations ceased while the vessel

travelled to the Olyutorski Gulf, where sampling operations

resumed in the ice-free waters on 14 June, and proceeded east
Figure 3.--Southern extension of sea-ice at the end of March, April, May, and June 1991

(adapted from Oceanographic Monthly Summary).
9

following the receding ice edge. The survey was completed off

Cape Navarin on 25 June.

Vessel and Fishing Gear

Survey operations were conducted aboard the Soviet research

vessel Novodrutsk, a 101.6 m stern-trawling factory processor. A

pelagic commercial Soviet net was used as a bottom trawl on all

stations (Table 2). A SCANMAR1

 net mensuration system was used

to record net height and width during the survey. Although the

SCANMAR system malfunctioned early in the survey, some

information was recorded on the trawl's configuration which

indicated that the net had an average wing spread of 27 m and

height of 8 m while fishing.

Table 2. --Attributes of the net used during

U.S.S.R. cooperative bottom trawl

Sea shelf.

the 1991 U.S.-

survey of the Bering

Collection and Processing of Samples

Station positions and distances fished were determined by a

Global Positioning System (GPS) provided by the AFSC.

1

Reference to trade names does not imply endorsement by the

National Marine Fisheries Service, NOAA.
10

Information collected for each haul included time of day, date,

start and end positions, depth, distance fished, surface and

bottom temperatures, and scope (trawl cable length out).

Trawling operations were limited to daylight hours to avoid

potential sampling bias due to diel movement patterns of some

fish. In U.S. waters, the survey was conducted from east to west

to avoid the possibility of sampling migrating fish populations

more than once.

The bottom trawl was towed for approximately 30 minutes at

each of the sampling sites, covering a linear distance averaging

4.2 km and an area of 0.1 km2. Catches weighing less than the

holding capacity of the sampling table (approximately 1,000 kg)

were processed in their entirety. If the catch exceeded the

capacity of the sampling table, the entire catch was weighed

using an electronic scale and then a random subsample of 1,000 kg

was transferred to the sorting table. Subsample weights and

numbers were later expanded by applying the ratio of the weight

of the processed portion of the catch to the total catch weight.

The catch was sorted into plastic baskets by species or

species groups and each tared basket was weighed to the nearest

tenth of a pound. If numerous baskets were filled with the same

species, then counts were made of a few baskets to provide

estimates of total numbers caught and the average animal weight.

The following target fish species were further processed for size

composition data:
11

1. Walleye pollock (Theragra chalcogramma).

2. Yellowfin sole (Pleuronectes asper).

3. Rock sole (Pleuronectes bilineatus).

4. Pacific cod (Gadus macrocephalus).

5. Flathead sole (Hippoglossoides elassodon).

6. Bering flounder (Hippoglossoides robustus).

7. Arrowtooth flounder (Atheresthes stomias).

8. Kamchatka flounder (Atheresthes evermanni).

9. Alaska plaice (Pleuronectes guadrituberculatus).

10. Pacific halibut (Hippoglossus stenolepis).

Other less frequently encountered species including Arctic cod

(Boreogadus saida), Pacific herring (Clupea pallasi), Sakhalin

sole (Pleuronectes sakhalinensis), and starry flounder

(Platichthys stellatus) were also measured as time permitted.

Lengths of commercially important fish species were measured

from a random subsample consisting of 150-200 specimens. The sex

of each specimen was determined, if possible, and the total

length (tip of snout to end of middle ray of caudal fin) was

recorded.

The AFSC and TINRO methods for collecting fish lengths are

different. For analytical purposes, fish lengths, which were

measured to the nearest higher centimeter (i.e., fish between

10 cm and 11 cm were recorded as 11 cm) on board the vessel, were

adjusted by an average of -0.5 cm. Lengths were randomly

assigned either the originally recorded length or were assigned

the original length subtracted by 1 cm. This adjustment was

performed so that measurements conformed to methods traditionally

used during AFSC surveys, where lengths are measured and rounded

off to the nearest whole centimeter (i.e., fish between 9.5 and

10.5 cm are recorded as 10 cm).
12

Age structures were collected from Pacific cod (otoliths and

scales) and walleye pollock (otoliths). Pacific cod collections

included the recording of individual fish weights. An attempt

was made to collect three otolith pairs (and scales) per

sex/centimeter length category for Pacific cod and five otolith

pairs per sex/centimeter for pollock.

A special collection of Pacific cod stomachs was made from

stations in Bristol Bay for food habits studies. Stomachs were

preserved in a 10% formalin solution and later transported to the

AFSC’s Trophic Interactions Unit for analysis.

Pacific halibut were removed from the catch as early as

possible, measured alive, and returned to the sea. No sex

determination was performed. Weights of halibut were calculated

from a length-weight relationship provided by the International

Pacific Halibut Commission (IPHC) as follows:

Weight(lbs) = (9.204 * 106

) * L3.24

(cm).

Data Analysis

A summary of the methods and procedures used in the data

analysis is provided here. A more complete description of the

analytical methods is provided in Wakabayashi et al. (1985).
13

Analysis of catch and distribution data was completed for

the major fish species encountered. Other less abundant or noncommercial species were grouped into broader taxonomic categories

for analysis.

Some species were grouped with a morphologically similar

congener for the analysis, even though an attempt was made to

separate them while at sea. Arrowtooth flounder and the closely

related Kamchatka flounder were grouped together and referred to

as Atheresthes spp. Flathead sole and Bering flounder are also

similar in appearance and they were grouped together as

Hippoglossoides spp. The groupings not only eliminated the

problems associated with misidentification of these similar

species, but it also facilitated comparison with past AFSC bottom

trawl surveys, which used the same groupings.

The area swept at each station was estimated as the product

distance fished, calculated from GPS start and end positions and

an assumed constant net width of 27 m. Catch weights in

kilograms were divided by hectares (1 ha equals 10,000 m2) of

area covered by the trawl to produce a standardized value of

catch per unit of effort (CPUE).

The mean CPUE value of a subarea was calculated by averaging

all CPUE values of the individual hauls in that subarea. The

mean CPUE value of each subarea was then weighted by its own area

for calculating the mean CPUE for combined subareas. Biomass and

population numbers were calculated for each subarea as the

product of the mean subarea CPUE and the area contained in that
14

subarea. Total biomass and population numbers were calculated by

summing the component subarea values.

The number of individuals by size and sex category was

estimated by expanding the length-frequency subsample to the

total number of fish at each sampling site. These expanded

numbers were consequently combined to represent the size

composition in each subarea and then applied to the population

number to produce a population at-size estimate.

Age composition in terms of biomass was estimated by first

calculating biomass at length using the equation:

where BL = biomass at length L in grams,

PL = population number at length L,

L = fork length in millimeters, and

A and B = constants based on regressions of previous

species-specific, length-weight data obtained

from the PACE eastern Bering Sea database.
15

Values used for the constants A and B are as follows:

A

1) Walleye pollock

Male 0.000011688

Female 0.000019090

All sexes 0.000012847

B

2.915008

2.833516

2.898081

A

2) Pacific cod

B

Male 0.0000044268 3.162674

Female 0.0000043510 3.165096

All sexes 0.0000043973 3.163560

After converting weight in grams to metric tons (t), BL was then

apportioned to biomass at age using the age-length keys for each

area. Growth characteristics of walleye pollock and Pacific cod

were described with von Bertalanffy (1938) growth curves fitted

to age-length data.
16

RESULTS OF THE SURVEY

Hauls and Data Collected

The research vessel Novodrutsk attempted 218 bottom trawls,

of which 213 were successfully completed (Fig. 1). A total of

83,662 length measurements were taken from 14 fish species

(Table 3). A total of 764 otolith pairs were collected from

walleye pollock and 509 otolith pairs and scale samples were

taken from Pacific cod. In Bristol Bay, 265 stomachs were

removed from Pacific cod and preserved for later analysis.

Table 3.--Collections of data from individual fish during the

1991 cooperative U.S.

the Bering Sea shelf.

-U.S.S.R. bottom trawl survey of
17

Environmental Conditions

Seawater surface temperatures ranged from -0.6°C to 9.2°C

(Fig. 4). The average surface water temperature in the standard

U.S. shelf was 2.3°C. Surface waters were coldest over Subareas

1, 2, and 4 and warmest near the Alaska Peninsula and shelf edge.

Surface temperatures were also warm along the Siberian coastline,

although this may be an artifact of the later sampling dates.

Bottom water temperatures ranged from -1.7°C to 3.7°C in the

overall survey area (Fig. 5). The average bottom temperature for

the standard U.S. shelf area was 1.3°C. A cold "tongue" of

bottom water extended far into the standard U.S. shelf area from

the north. Water below 0°C surrounded St. Matthew Island and

extended south, encompassing most of Subarea 4. Water less than

l°C surrounded this cold mass and extended eastward, following

the 50 m isobath into Bristol Bay. The warmest bottom water

temperatures were near the Alaska coast along the Alaska

Peninsula and also in the deep water along the western edge of

Subareas 5 and 6.

Relative Importance of Major Taxonomic Groups

A total of 80 fish species (Table 4), 13 shrimp species, 13

crab species, and 63 other invertebrate species or species groups

were identified during the survey. The total estimated biomass

of fish and invertebrates combined in the survey area was

8.5 million t. Approximately 82% of the total biomass was in the

standard U.S. area, 17% over the western shelf, and 1% over the

north shelf.

Figure 5. --Distribution of bottom water temperatures (°C) observed during the 1991

cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelf.
20

Table 4 .--Mean CPUE (kg/ha) of fish species encountered during the 1991 U.S.-

U.S.S.R. cooperative Bering Sea groundfish trawl survey.
21

Table 4 .--Continued.
22

Fish--The total biomass of all fish species combined was

8.0 million t which accounted for 93% of the total biomass of

fish and invertebrates (Table 5). Approximately 6.6 million t of

the fish biomass was in the standard U.S. shelf area,

1.3 million t in the western shelf area, and 0.06 million t in

the north shelf area. The combined families of Gadidae and

Pleuronectidae accounted for the majority of the total fish

biomass. The families of Rajidae, Cottidae, Clupeidae, and

Zoarcidae contributed most of the remaining fish biomass. Figure

6 illustrates the distribution and relative abundance of total

fish.

Invertebrates--The total invertebrate biomass accounted for

less than 7% (0.6 million t) of the total biomass estimate for

the survey (Table 6). Approximately 0.44 million t of the

combined invertebrate biomass was located in the standard U.S.

shelf area, while 0.12 million t was on the western shelf area,

and 0.01 million t was over the north shelf area. The phylum

Echinodermata (206,272 t) had the greatest biomass of all

invertebrate groups, followed by the phylums Coelenterata

(188,731 t) and Arthropoda (106,910 t).
Table 5.--Biomass estimates in metric tons (t) for major fish species and fish groups taken during the 1991 cooperative U.S.-U.S.S.R. bottom trawl

survey of the Bering Sea shelf.

aRounding accounts for minor discrepancies between sums of subareas and total survey area, and between sums of taxonomic subgroups and major groups.

bProportion of total estimated biomass, fish and Invertebrates combined, for the total survey area. Total estimated biomass = 8.549.418 t.
Figure 6. --Distribution and relative abundance in kg/ha of total fish sampled during the

1991 cooperative U.S. -U.S.S.R bottom trawl survey of the Bering Sea shelf.
Table 6.--Biomass estimates in metric tons (t) for major invertebrate groups taken during the 1991 cooperative U.S.-U.S.S.R bottom trawl survey of

the Bering Sea shelf.
26

Abundance of Major Fish Groups

Gadidae (codfishes)

Gadids were represented by four species with a combined

biomass of 4.9 million t, or 61% of the overall fish biomass,

making them the most abundant species group in the survey region

(Table 5). Walleye pollock (3.8 million t or 79%) accounted for

the majority of the gadid biomass, followed by Pacific cod

(0.9 million t or 20%). Saffron and Arctic cod accounted for

only 1% of the gadid biomass.

Pleuronectidae (flatfishes)

Fourteen species of pleuronectids were identified during the

survey (Table 4). They accounted for 2.5 million t or 31% of the

total fish biomass (Table 5). Yellowfin sole (33%) and rock sole

(32%) were the most abundant flatfish species. Most of the

remainder of the flatfish biomass consisted of Hippoglossoides

spp. (12%), Alaska plaice (l0%), Atheresthes spp. (6%), and

Pacific halibut (5%).

Rajidae (skates)

Skates were the third most abundant fish group with an

estimated biomass of 227,828 t (2.9% of total fish biomass,

Table 5). Skates were most abundant at depths greater than 100 m

(Fig. 7). Approximately 89% of the total skate biomass was in

the standard U.S. area, with highest concentrations in Subareas 5

and 6. Four skate species were identified in the survey
Figure 7. --Distribution and relative abundance in kg/ha of total skates sampled during the

1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelf.
2 8

(Table 4). The Alaska skate (Bathyaja parmifera) was the most

frequently encountered member of this group with an overall CPUE

of 3.7 kg/ha. The Aleutian skate (B. aleutica) and big skate

(Raja binoculata) were only found in the standard U.S. area,

while the Bering skate (B. interrupta) was caught in both the

standard U.S. area and the western area.

Cottidae (sculpins)

Sculpins were broadly distributed throughout the survey area

(Fig. 8). This was the most diverse group with 20 species of

sculpins identified (Table 4), but it accounted for only 2.4% of

the total fish biomass (Table 5). Although catch rates of

sculpins were highest in Subarea 15, 71% of the biomass occurred

in the standard U.S. shelf area. Members of the genus

Myoxocephalus were the major component of this group, accounting

for 49% of the overall sculpin biomass.

Other Species

Thirty-seven other species from 12 additional families were

also identified during the survey (Table 4). The combined

biomass of these species was approximately 200,000 t or 2.7% of

the total fish biomass (Table 5). The dominant families were

Clupeidae (Pacific herring was the only species identified;

189,000 t or 2.2%), Zoarcidae (total eelpouts; 17,550 t or 0.2%),

Cyclopteridae (total snailfishes; 6,600 t or 0.08%), Osmeridae

(total smelts; 5,900 t or 0.07%); and Agonidae (total poachers;
Figure 8.--Distribution and relative abundance in kg/ha of total sculpins sampled during

the 1991 cooperative U.S.-U.S.S.R. bottom trawl survey of the Bering Sea shelf.
3 0

5,500 t or 0.07%). The distribution and relative abundance of

Pacific herring, total eelpouts, total snailfishes, total smelts,

and total poachers are presented in Figures 9-13.
Figure 9.--Distribution and relative abundance in kg/ha of Pacific herring sampled during

the 1991 cooperative U.S.-U.S.S.R. bottom trawl survey of the Bering Sea shelf.
Figure 10. --Distribution and relative abundance in kg/ha of total eelpouts sampled during

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea

shelf.

Figure 12. --Distribution and relative abundance in kg/ha of total smelts sampled during

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea

shelf.
Figure 13. --Distribution and relative abundance in kg/ha of total poachers sampled during

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea

shelf.
36

Abundance, Distribution, and Size Composition

of Principal Fish Species

Walleye pollock

Distribution and abundance--Walleye pollock was the most

frequently encountered fish species in the survey and it occurred

in nearly all of the hauls (Fig. 14). Pollock also had the

highest overall mean catch rate of any fish species at 65.7 kg/ha

(Table 7). The mean catch rate was slightly higher in the

western shelf area (69.4 kg/ha) than in the standard U.S. shelf

area (66.3 kg/ha). Pollock were found at low levels of abundance

in the north shelf area, averaging 9.0 kg/ha. Catch rates were

highest in Subarea 6 (173.0 kg/ha), followed by Subarea 16

(129.8 kg/ha), Subarea 3 (67.4 kg/ha), and Subarea 17

(62.1 kg/ha). Catch rates were lowest in Subarea 14 (0.9 kg/ha)

and Subarea 2 (6.3 kg/ha).

The total biomass of pollock was estimated at approximately

3.9 million t and accounted for nearly 49% of the estimated

biomass of all fish combined. Approximately 3.0 million t or 79%

of the pollock biomass was in the standard U.S. shelf area. The

western shelf accounted for 780,000 t (20%) while the north shelf

contributed 0.3% of the total biomass. Nearly 42% of the total

biomass was in Subarea 6.

The total number of pollock was estimated at over

9.1 billion fish, with 84% in the standard U.S. shelf area.

Approximately 50% of the entire population was in Subarea 6.
Figure 14.--Distribution and relative abundance in kg/ha of walleye pollock sampled during

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea

shelf.
Table 7. --Abundance estimates and mean size of walleye pollock by subarea from

the 1991 cooperative U.S.

Sea shelf.

-U.S.S.R. bottom trawl survey of the Bering

a

Differences in totals and sums of biomass and population numbers by subarea are due to rounding.

b

- indicates no sample or insufficient data.
3 9

Size composition--Pollock measured during the survey ranged

in size from 8 to 87 cm in fork length (Fig. 15). The length

frequency distribution of nearly all subareas clearly showed two

or more modes (Fig. 16). All subareas of the standard U.S. shelf

showed distinct modes for large and small pollock. The smallest

pollock (<18 cm) were abundant on the standard U.S. shelf area,

especially in Subareas 2, 3, and 4. Mid-sized pollock (18 cm30 cm) were abundant at depths greater than 100 m, less abundant

at 50-100 m, and were virtually nonexistent in waters less than

50 m. Large pollock (mostly 45 cm-75 cm) were present in all

subareas of the standard U.S. shelf area. The length frequency

distributions of Subareas 9, 14, and 15 showed similar patterns;

they all included a wide mode of small fish and a mode of large

fish. The population of Subarea 16 was composed almost entirely

of large fish, with a single mode of lengths centered around

45 cm. Subarea 17 had a large mode of small fish and a wide

distribution of large fish.

Age composition--Fish 4 and 5 years old comprised

approximately 37% of the fish population, with age-5 fish

accounting for 20% of the total population (Fig. 17). All the

other age groups each accounted for less than 12% of the total

population. The majority of the biomass was distributed over

several age groups (Fig. 18). Fish aged at 4 to 6 years old

comprised approximately 43% of the biomass.
4 0

Figure 15. --Estimated size composition of walleye pollock by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 16. --Estimated relative size composition of walleye pollock (sexes combined) by

subarea during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the

Bering Sea shelf.
4 2

Figure 17. --Relative age composition of walleye pollock as shown

by age data collected aboard the RV Novodrutsk.
4 3

Figure 18. --Biomass estimated in metric tons (t) by age for

walleye pollock as shown by age data collected aboard

the RV Novodrutsk.
44

Growth--Von Bertalanffy growth curves fitted to age data for

walleye pollock showed similar growth patterns between the sexes

until age 11, where females were generally larger at age than

males (Fig. 19). The asymptotic length was nearly 10 cm higher

for females than males and the growth completion rates (K) were

also different (Table 8).

Figure 19. --Von Bertalanffy growth curves and mean lengths at age

for male and female walleye pollock as shown by age

data collected aboard the RV Novodrutsk during the

1991 cooperative U.S. -U.S.S.R. bottom trawl survey of

the Bering Sea shelf.
45

Table 8 .--Parameters of the von Bertalanffy growth curves for

walleye pollock by sex based on age readings from

otoliths and length data from the 1991 U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.

Sex

Male

Number Length

of age

readings*

Age range Parameters

range (cm) Linf K t0

341 1-19 13-74 58.289 0.2792 0.3573

Female 427 1-26 13-81 67.527 0.1859 -0.3771

a

Number for males and females includes 10 unsexed fish below 20 cm.

Pacific Cod

Distribution and abundance--Pacific cod were broadly

distributed throughout the survey area (Fig. 20). They were

identified in 92% of the hauls and were the second most

frequently encountered fish species (Table 9). The overall mean

catch rate was 16.7 kg/ha. Catch rates were highest in the north

shelf area with a mean of 23.1 kg/ha and lowest in the standard

U.S. shelf area at 15.5 kg/ha. The highest catch rates were in

Subarea 15 (45.4 kg/ha), Subarea 6 (35.1 kg/ha), Subarea 9

(23.1 kg/ha), and Subarea 17 (21.9 kg/ha). Pacific cod were

least abundant at depths less than 50 m in Subareas 1 and 2 with

catch rates of 3.8 kg/ha and 2.1 kg/ha, respectively.

The total Pacific cod biomass was estimated at 980,681 t, of

which 73% was in the standard U.S. shelf area. Subarea 6

accounted for 34% of the total Pacific cod biomass. The total

estimated population of Pacific cod was 616 million fish, with

61% located in the standard U.S. shelf area.
Figure 20. --Distribution and relative abundance in kg/ha of Pacific cod sampled during

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea

shelf.
Table 9 .--Abundance estimates and mean size of Pacific cod by subarea from the 1991

cooperative U.S.-U.S.S.R. bottom trawl survey of the Bering Sea shelf.ab

a

Differences in totals and sums of biomass and population numbers by subarea are due to rounding.

b

- indicates no sample or insufficient data.
48

Only 2% of the population was located in the north shelf area.

Subarea 15 contained the highest portion of the population with

an estimated 153 million individuals, approximately 25% of the

Pacific cod population, but only 12% of the biomass. This was

due to the high concentration of juveniles encountered in that

subarea.

Size composition--Pacific cod lengths ranged from 11 to

110 cm (Fig. 21). A prominent mode around 30 cm was evident in

the size composition of most subareas except 5, 6, 16, and 17

(Fig. 22). Size composition varied greatly between the subareas

and mean length generally increased with depth (Fig. 22). In the

standard U.S. shelf area, the modes of small fish were more

abundant in the shallower subareas while larger fish were

predominate in deeper waters. In Subarea 1 (<50 m in depth),

modes centered around 14 cm and 29 cm comprised 89% of the

population. The size compositions of Subareas 3 and 4 were

similar to the size composition of Subarea 1, although there were

fewer fish in the smallest size mode. Small fish in Subareas 3

and 4 represented 55% and 64% of the population, respectively.

In Subareas 5 and 6 (100-200 m in depth), only 4% and 23% of the

Pacific cod population, respectively, was composed of small fish.

Small Pacific cod accounted for a high percentage of the

total populations in Subareas 9, 14, and 15. Eighty percent of

the population in Subarea 15 was in the mode of smallest fish,

while 48% of the population in Subarea 9 and 32% of the

population in Subarea 14 were in the mode of smallest fish.
49

Figure 21. --Estimated size composition of Pacific cod by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 22. --Estimated relative size composition of Pacific cod (sexes combined) by

subarea during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the

Bering Sea shelf.
5 1

Small fish accounted for 13% of the population in Subarea 16 and

40% in Subarea 17.

Age composition--Although fish as small as 11 cm were

encountered in the survey, no Pacific cod smaller than 22 cm were

included in the age structure collections and they were all aged

as being age 2 or older. Therefore, fish smaller than 22 cm were

grouped together as ≤1 year old. Approximately one-half of the

Pacific cod population was comprised of age-2 and age-3 fish

(Fig. 23). All age groups over age 7 each comprised less than 5%

of the population. Age groups of cod 5-9 years old comprised 60%

of the total biomass, with the mode at age groups 6 and 7

(Fig. 24).

Growth--Von Bertalanffy growth curves fitted to age data for

Pacific cod indicated similar growth between the sexes (Fig. 25).

Growth completion rates (K) were nearly equal, although the

asymptotic length was higher for females than males (Table 10).

Yellowfin sole

Distribution and abundance--Yellowfin sole were identified

in 60% of the hauls and were the seventh most frequently

encountered species of commercial importance. They were

primarily distributed on the standard U.S. shelf at depths less

than 100 m (Fig. 26). Yellowfin sole were also observed in the

far western region of the survey in the Olyutorski Gulf. The

overall mean CPUE for yellowfin sole was 13.7 kg/ha (Table 11).

Highest catch rates were encountered in the standard U.S. shelf
5 2

Figure 23. --Relative age composition of Pacific cod as shown

by age data collected aboard the RV Novodrutsk.
53

Figure 24. --Biomass in metric tons (t) estimated by age for

Pacific cod as shown by age data collected aboard the

RV Novodrutsk.
54

Figure 25. --Von Bertalanffy growth curves and mean lengths at age

for male and female Pacific cod as shown by age data

collected aboard the RV Novodrutsk during the 1991

cooperative U.S. -U.S.S.R. bottom trawl survey of the

Bering Sea shelf.
55

Table 10. --Parameters of the von Bertalanffy growth curves for

Pacific cod by sex based on age readings from otoliths

and length data from the 1991 U.S.-U.S.S.R. bottom

trawl survey of the Bering Sea shelf.

Table ll.--Abundance estimates and mean size of yellowfin sole by subarea from the 1991

cooperative U.S.-U.S.S.R. bottom trawl survey of the Bering Sea shelf.ab
5 8

area with a mean CPUE of 17.4 kg/ha. Only trace catches were

made in the north shelf and western shelf areas with mean CPUE

values of 0.03 kg/ha and 0.1 kg/ha, respectively. The highest

concentrations of yellowfin sole were in Subarea 2 with an

average catch rate of 42.1 kg/ha. Yellowfin sole were also

abundant in Subarea 1 (27.6 kg/ha), Subarea 4 (22.6 kg/ha), and

Subarea 3 (16.9 kg/ha). Catch rates in all other subareas were

less than 1 kg/ha.

The total biomass of yellowfin sole was estimated at 807,162

t, of which 99.8% was in subareas 1 through 4. The total

population of yellowfin sole was estimated at 2.9 billion fish.

Size composition--Yellowfin sole were only measured in the

U.S. standard shelf area. No length data were recorded in the

north shelf or western shelf areas where they occurred in trace

amounts. Yellowfin sole ranged in length from 10 to 45 cm, but

94% of the population was between 20 and 40 cm in length

(Figs. 27 and 28).

Ninety-nine percent of the small yellowfin sole (119 cm)

were in waters of less than 50 m in Subareas 1 and 2. Mid-sized

yellowfin sole, ranging from 20 to 29 cm, were the most abundant

size group in each subarea and accounted for 54% of the total

population. They were most abundant in Subarea 2, where they

comprised 69% of the population. Fish longer than 29 cm

represented significant portions of the populations in Subarea 3

(48%) t Subarea 4 (45%), Subarea 1 (43%), and a smaller portion of

the population in Subarea 2 (26%).
5 9

Figure 27. --Estimated size composition of yellowfin sole by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 28. --Estimated relative size composition of yellowfin sole (sexes combined) by

subarea during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the

Bering Sea shelf.
61

Rock sole

Distribution and abundance--Although rock sole were found in

all subareas, the highest concentrations were observed in Bristol

Bay and throughout the central portion of the eastern Bering Sea

(Fig. 29). Rock sole were identified in 79% of the hauls. The

overall mean CPUE value was 13.6 kg/ha (Table 12). Catch rates

were highest in the standard U.S. shelf area with a mean CPUE of

17.1 kg/ha. They were encountered in trace amounts in the north

shelf (0.12 kg/ha) and western shelf (0.67 kg/ha) areas. Rock

sole were most abundant at depths less than 100 m, with highest

concentrations occurring in subarea 1 with a mean CPUE of

34.5 kg/ha.

The total estimated biomass of rock sole was 799,855 t.

Ninety-nine percent of the overall biomass occurred in the

standard U.S. shelf area, 89% of which occurred in the combined

Subareas of 1, 3, and 4. The total population was estimated at

3.7 billion fish, with 51% or 1.9 billion fish located in Subarea

1.

Size composition--Rock sole ranged in length from 8 to 50 cm

(Fig. 30). Length measurements were collected from the standard

U.S. shelf area but were not recorded from the north shelf or

western shelf areas where less than 1% of the population

occurred. Smaller rock sole (119 cm) were most abundant in the

shallowest subareas, especially in Subarea 1, where they

comprised 46% of the population (Fig. 31). Seventy-seven percent

of all fish less than 20 cm were in Subarea 1. Their portion of
Figure 29. --Distribution and relative abundance in kg/ha of rock sole sampled during

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea

shelf.
Table 12.--Abundance estimates and mean size of rock sole by subarea from the 1991

cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelf.ab

a

Differences in totals and sums of biomass and population numbers by subarea are due to rounding.

b

- indicates no sample or insufficient data.
6 4

Figure 30. --Estimated size composition of rock sole by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 31.--Estimated relative size composition of rock sole (sexes combined) by

subarea during the 1991 cooperative U.S.

Bering Sea shelf.

-U.S.S.R. bottom trawl survey of the
66

the population decreased with increasing depth, and it was

especially low in Subarea 6, where they accounted for only 1% of

the population. Mid-sized (20-29 cm) rock sole were abundant in

shallow and medium depth subareas, and they were the dominant

size group in Subarea 3, where they comprised 57% of the

population. Large rock sole ( ≤ 30 cm) were the most abundant size

group in Subareas 2 (42%) and 4 (55%), and they were the

predominate size group in Subarea 6 (82%).

Hippoglossoides spp.

Distribution and abundance--Hippoglossoides spp. were found

in all subareas with largest catches occurring at depths greater

than 50 m (Fig. 32). This genus occurred in 79% of the hauls and

had an overall mean CPUE of 5.1 kg/ha (Table 13). Catch rates

were similar in the U.S. standard shelf (5.9 kg/ha) and the north

shelf (5.8 kg/ha) areas. Hippoglossoides spp. were found in low

abundance in the western shelf area (1.8 kg/ha). Mean catch

rates were highest in Subarea 3 (12.9 kg/ha) and Subarea 6

(10.1 kg/ha).

The total estimated biomass of Hippoglossoides spp. was

299,816 t. Approximately 91% of the total biomass was in the

standard U.S. shelf area, 7% in the western shelf area, and 2% in

the north shelf area. Subarea 3 accounted for 44% of the total

biomass. The total estimated population of Hippoglossoides spp.

was 996 million fish.
Figure 32. --Distribution and relative abundance in kg/ha of Hippoglossoides spp. sampled

during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering

Sea shelf.
Table 13. --Abundance estimates and mean size of Hippoglossoides spp. by subarea from the

1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelfab.
69

Size composition--Hippoglossoides spp. ranged in size from

9 to 51 cm (Fig. 33). Mean fish size was larger in the

standard U.S. shelf area (31.4 cm) than the north shelf

(25.5 cm) and western shelf (24.2 cm) areas. Seven percent of

the total population was ≤ 19 cm, while 78% of the fish ranged

in length from 20 to 40 cm. Within the standard U.S. shelf

area, fish were largest at depths between 50 and 100 m,

averaging 34.1 cm and 33.7 cm in Subareas 3 and 4, respectively

(Fig. 34). Fish in the deeper Subareas of 5 and 6 (100 m200 m) averaged 28.0 cm and 29.2 cm, respectively.

Approximately 80% and 76% of the fish in Subareas 3 and 4,

respectively, were ≤ 30 cm. In Subareas 5 and 6, 41% and 45% of

the fish, respectively, were ≤ 30 cm, while most of the

remaining fish were in the middle size range of 20 cm-29 cm.

Alaska plaice

Distribution and abundance--Alaska plaice were encountered

at 67% of the sampling sites with highest catch rates occurring

in the northeast portion of the standard U.S. shelf area

(Fig. 35). This was the sixth most frequently encountered fish

species during the survey. The overall mean catch rate was

4.4 kg/ha (Table 14). Mean catch rates were highest at depths

less than 50 m in Subarea 2 (12.2 kg/ha) and Subarea 1

(9.4 kg/ha).

The total estimated biomass of Alaska plaice was

255,750 t. Ninety-three percent of the biomass was in the

standard U.S. shelf area, with 6% in the western shelf area.
70

Figure 33. --Estimated size composition of Hippoglossoides spp. by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 34. --Estimated relative size composition of Hippoglossoides spp. (sexes combined)

by subarea during the 1991 cooperative U.S.-U.S.S.R.

the Bering Sea shelf.

bottom trawl survey of

Table 14.--Abundance estimates and mean size of Alaska plaice by subarea from the 1991

cooperative U.S.-U.S.S.R. bottom trawl survey of the Bering Sea shelf.ab

a

Differences in totals and sums of biomass and population numbers by subarea are due to rounding.

b

- indicates no sample or insufficient data.
74

Approximately 92% of the total biomass was in the combined

Subareas of 1 through 4. The total estimated population was

352 million fish.

Size composition--Alaska plaice ranged from 14 to 56 cm in

total length (Fig. 36). In general, mean size increased with

increasing depth, ranging from approximately 36 cm in Subareas 1

and 2 (<50 m) to 40 cm in Subareas 3 and 4 (50 m-100 m)

(Fig. 37). The length frequency distributions of the fish in

subareas 1 and 2 showed strong modes centered around 35 cm to

36 cm.

Atheresthes spp.

Distribution and abundance--Atheresthes spp. were primarily

restricted in distribution to depths greater than 100 m

(Fig. 38). This genus occurred in 31% of the hauls. The average

catch rate for the survey was 2.7 kg/ha (Table 15). CPUE was

greatest in the standard U.S. shelf area, averaging 3.4 kg/ha,

compared with the north shelf (0.05 kg/ha) and western shelf

(0.09 kg/ha) areas. Atheresthes spp. were most abundant in the

100 m-200 m depth zones of Subareas 5 and 6, with mean CPUE

values of 13.0 kg/ha and 7.9 kg/ha, respectively.

The estimated biomass for the survey area was 156,508 t.

Over 99% of the biomass was located in the standard U.S. shelf

area, primarily in Subareas 3, 5, and 6. No Atheresthes spp.

were encountered in Subareas 1, 2, and 14, and only trace amounts

were observed in western shelf Subareas 15, 16, and 17.
75

Figure 36. --Estimated size composition of Alaska plaice by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 37. --Estimated relative size composition of Alaska plaice (sexes combined)

by subarea during the 1991 cooperative U.S.-U.S.S.R.

the Bering Sea shelf.

bottom trawl survey of
Figure 38. --Distribution and relative abundance in kg/ha of Atheresthes spp. sampled

during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering

Sea shelf.
Table 15. --Abundance estimates and mean size of Atheresthes spp. by subarea from the

1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelf.ab

a

Differences in totals and sums of biomass and population numbers by subarea are due to rounding.

b

- indicates no sample or insufficient data.
79

Size composition--Atheresthes spp. were only measured from

catches in the standard U.S. shelf area. Lengths ranged from

13 to 68 cm (Fig. 39). Subareas 3 and 5 were dominated by fish

in the 30 cm-39 cm size range, comprising 66% and 62% of the

population, respectively (Fig. 40). The size distribution in

Subarea 6 was not dominated by any single size group of fish,

although two modes were apparent: one centered around 24 cm and

the other centered at approximately 40 cm. The size distribution

in Subarea 4 was also bimodal with one mode centered around 25

cm, and the other between 33 cm and 41 cm.

Pacific halibut

Distribution and abundance--The distribution of catch rates

for Pacific halibut is shown in Figure 41. They occurred in 75%

of the hauls with an overall catch rate of 2.0 kg/ha (Table

Catch rates for the western shelf area (2.0 kg/ha) averaged

nearly the same as catch rates from the standard U.S. shelf

16).

area

(2.1 kg/ha). Highest concentrations occurred in standard U.S.

shelf Subarea 5 (4.1 kg/ha) and in western shelf Subareas 16

(3.4 kg/ha) and 17 (3.4 kg/ha).

The total biomass of Pacific halibut in the survey area was

estimated at 119,413 t. The standard U.S. shelf area accounted

for about 81% of the total biomass, with the western shelf area

contributing 19%. The north shelf area contained less than 1.0%

of the overall biomass. The total estimated population was

68 million fish with 95% located in the standard U.S. shelf area.
8 0

Figure 39. --Estimated size composition of Atheresthes spp. by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 40. --Estimated relative size composition of Atheresthes spp. (sexes combined)

by subarea during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of

the Bering Sea shelf.

Table 16. --Abundance estimates and mean size of Pacific halibut by subarea from

the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering

Sea shelf.

aDifference in totals and sums of biomass and population numbers by subarea are due to rounding. b- indicates no sample or insufficient data.
Pacific halibut abundance varied widely with bottom temperature

and depth. Highest catch rates were observed at depths of 55 m145 m and in bottom temperatures ranging from 0°C to nearly 4°C.

84

Size composition--Pacific halibut had the greatest size

range of any species measured. They ranged from 14 to 215 cm in

total length (Fig. 42). Subareas l-4 all had a strong mode of

small fish ( ≤ 49 cm in length), which accounted for 75% to 93% of

the population of these Subareas (Fig. 43). Both mean size and

maximum length were greater in Subareas 5 and 6. Approximately

78% of the halibut in Subarea 5 and 49% of the halibut in Subarea

6 were 50 cm-100 cm in length, as opposed to Subareas l-4, where

at most only 25% were between 50 cm and 100 cm.

Greenland turbot

Distribution and abundance--Greenland turbot occurred in 27%

of the total hauls, primarily at depths greater than 100 m

(Fig. 44). The average catch rate for the overall survey was

0.2 kg/ha with the highest mean CPUE of nearly 1.0 kg/ha in

Subarea 6 (Table 17).

The total survey biomass of Greenland turbot was estimated

at 12,621 t. Approximately 74% of the biomass was located in

Subarea 6 with an additional 12% in Subarea 15. The estimated

population was 27 million fish. Nearly all Greenland turbot

catches occurred at bottom temperatures ranging between 0°C and

approximately 2°C, and between 90 and 180 m in depth.
85

Figure 42. --Estimated size composition of Pacific halibut by

region during the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf.
Figure 43. --Estimated relative size composition of Pacific halibut (sexes combined)

by subarea during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of

the Bering Sea shelf.
Figure 44. --Distribution and relative abundance in kg/ha of Greenland turbot sampled

during the 1991 cooperative U.S.-U.S.S.R.

Sea shelf.

bottom trawl survey of the Bering
Table 17. --Abundance estimates and mean size of Greenland turbot by subarea from the

1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering Sea shelf.ab

a

Differences in totals and sums of biomass and population numbers by subarea are due to rounding.

b

- indicates no sample or insufficient data.
89

Size composition--Greenland turbot were encountered in small

numbers and no length data were collected.

Distribution of Major Crab Species

The Soviet net was inefficient at sampling most benthic as

well as many epibenthic species. Catches of invertebrates, in

general, were approximately ten times lower in this cooperative

survey than during the 1991 U.S. bottom trawl survey. Catch data

collected during the 1991 U.S.-U.S.S.R. cooperative survey was

probably not indicative of the abundance of most invertebrates,

including commercially important crab species. However, these

data may provide some insight into the range and relative

distribution of the major species of crab. Maps showing relative

catch rates for snow crab ( ⊆. onilio and ⊆. bairdi), red king

crab, and blue king crab are presented in Figures 45 through 48.

They are intended to show only the general distribution patterns

of the commercially important crab species as encountered in the

survey.
Figure 45. --Distribution and relative abundance in kg/ha of snow crab (⊆. opilio) sampled

during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering

Sea shelf.
Figure 46. --Distribution and relative abundance in kg/ha of snow crab (⊆. bairdi) sampled

during the 1991 cooperative U.S. -U.S.S.R. bottom trawl survey of the Bering

Sea shelf.


94

DISCUSSION

Comparison of results among past independent U.S. and

cooperative U.S. -U.S.S.R. bottom trawl surveys in the Bering Sea

have shown major differences in abundance estimates in areas

commonly sampled. For the last 4 years of the time series (see

Sample and Nichol 1994), biomass estimates of individual species

from the U.S.-U.S.S.R. cooperative survey data were generally

lower than biomass estimates from the independent U.S. survey

data of the standard U.S. shelf area (Table 18). The cooperative

survey biomass estimates of walleye pollock, Hippoglossoides

Spp., and Atheresthes spp. are approximately 50% lower than from

the U.S. surveys for 1988-1991. Biomass estimates from the 1991

cooperative survey were at least 40% lower than U.S. biomass

estimates for all species except Greenland turbot, Pacific

halibut, and Pacific cod (Table 18). The 1991 U.S.-U.S.S.R.

survey biomass estimates of several invertebrate groups including

crustaceans, echinoderms, ascideans, and mollusks were 90% to 99%

lower than the biomass from the 1991 U.S. survey. These results

likely indicate a greater fishing efficiency by the U.S. standard

83-112 bottom trawl relative to the Soviet commercial pelagic net

used in the 1991 cooperative survey. The Soviet net may have had

poor bottom-tending characteristics. It is noteworthy that the

1991 Soviet net had a wing mesh size of 200 mm, which was double

the mesh size for the 1990 Soviet net (100 mm) and nearly double
Table 18.--Biomass estimates in metric tons for major fish species from the standard U.S.

shelf commonly fished during separate U.S. and cooperative U.S.-U.S.S.R. bottom

trawl surveys conducted during 1988-1991.'

a

Biomass estimates for invertebrates are not available for 1988 and 1989.
96

the wing mesh size of the U.S. net (102 mm). However, there is

little information to assess the 1991 Soviet net's fishing

characteristics and efficiencies.

Mean size for yellowfin sole, rock sole, Alaska plaice, and

Pacific halibut measured from the standard U.S. shelf area were

about 2 cm to 4 cm longer during the U.S.-U.S.S.R. cooperative

survey compared with the U.S. survey (Fig. 49). However, the

magnitude of the population at-size was greatly reduced for all

the flatfish species with the exception of Pacific halibut from

the U.S.-U.S.S.R. cooperative data sets. The relative size

composition was similar for both yellowfin sole and Pacific

halibut. The mean length of walleye pollock was longer during

the U.S. survey (37.7 cm) rather than during the U.S.-U.S.S.R.

cooperative survey (31.3 cm) (Fig. 50). The Soviet commercial

pelagic net appeared to be more efficient at sampling juvenile

pollock while the U.S. 83-112 net was apparently more efficient

at sampling the adult portion of the population. Pacific cod

mean length was longer from the U.S. -U.S.S.R. cooperative survey

(45.6 cm) compared with the U.S. survey (37.0 cm) (Fig. 50).

Relating the results from the U.S.-U.S.S.R. cooperative

surveys to the results from the U.S. surveys can be ambiguous, as

described by Sample and Nichol (1994). Potential bias in the

cooperative survey data sets can not be fully evaluated.

Comparative trawling experiments were not conducted with the

research vessel Novodrutsk in 1991. Therefore the fishing

efficiency of the Soviet sampling net can not be assessed further
97

Figure 49. --Length composition of yellowfin sole, rock sole,

Alaska plaice, and Pacific halibut during the 1991

independent U.S. bottom trawl survey and the 1991

cooperative U.S. -U.S.S.R. bottom trawl survey. Data

is from the standard U.S. area commonly fished during

both surveys.
98

Figure 50. --Length compostion of walleye pollock and Pacific cod

during the 1991 independent U.S. bottom trawl survey

and the 1991 cooperative U.S.-U.S.S.R. bottom trawl

survey. Data is from the standard U.S. area commonly

fished during both surveys.
99

or related to other sampling trawls. Also, since the net

mensuration equipment malfunctioned after only a few readings

were recorded, the approximate mean net width used for the

biomass calculations may be inaccurate. While past U.S.-U.S.S.R.

cooperative surveys have begun about 2 weeks prior to the U.S.

survey, the 1991 cooperative survey started about 1 month before

the U.S. survey. This difference in sampling time may have

allowed for movement of some portion of the groundfish assemblage

into or out of the survey area. Such movement may have accounted

for at least some of the differences in biomass estimates and

population parameters between the two surveys.

The 1991 cooperative U.S. -U.S.S.R. survey region extended

farther west along the Bering Sea shelf than during earlier

cooperative surveys. The information gathered from sampling

sites in Cape Olyutorski has provided U.S. scientists with the

first direct data on the biological characteristics of that

region. However, potential biases in the 1991 data set may limit

its value.
100

ACKNOWLEDGMENTS

The authors wish to express their gratitude to Russian

scientist Dr. Mikhail Stepanenko and to the specialists and

vessel crew of the RV Novodrutsk who participated in this survey.

Our appreciation is also extended to AFSC personnel Dennis

Benjamin, Doyne Kessler, David Roetcisoender, Lynn Faughnan, and

Lee Anne Powell who assisted on board the RV Novodrutsk in the

collection of the data presented in the report.
101

CITATIONS

Goddard, P., and M. Zimmermann. 1993. Distribution, abundance

and biological characteristics of groundfish in the eastern

Bering Sea based on results of the U.S. bottom trawl survey

during June-September 1991. AFSC Processed Rep. 93-15,

324 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv.,

NOAA, 7600 Sand Point Way NE, BIN C15700, Seattle, WA

98115-0070.

Kinder, T. H., and J. D. Schumacher. 1981. Hydrographic

structure over the continental shelf of the southeastern

Bering Sea, p.31-52. In D. W. Hood and J. A. Calder (eds.)

The eastern Bering Sea shelf: Oceanography and resources,

Vol. 1, Office of Mar. Poll. Assess., Natl. Oceanic. Atmos.

Admin.

Moiseev, P. A. (editor) 1963-1965, 1970. Soviet fisheries

investigations in the northeastern Pacific. Tr. Vses.

Nauchnoissled. Inst. Morsk. Rybn. Khoz. Okeanogr. 48, 49,

53, 58, 70 (Izv. Tikhookean. Nauchno-issled. Morsk. Rybn.

Khoz. Okeanogr. 50-53, 72). (Transl. in Soviet Fisheries

Investigations in the northeast Pacific, Pt. I-V, by Israel

Program Sci. Transl.) Avail. Natl. Tech. Inf. Serv.,

Springfield, VA, as TT 67-51203, TT 67-51204, TT 67-51205,

TT 67-51206, and TT 71-50127.

Oceanographic Monthly Summary Vol. XI, No.4-7, 1991, Navy-NOAA

Joint Ice Center, National Meteorological Center, W/NMC2l.

Sample, T. M., and D. G. Nichol. 1994. Results of the 1990

U.S.- U.S.S.R. cooperative bottom trawl survey of the

eastern and northwestern Bering Sea continental shelf. U.S.

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-34, 183 p.

von Bertalannfy, L. 1938. A quantitative theory of organic

growth. Hum. Biol. 10:181-213.

Wakabayashi, K., R. G. Bakkala, and M. S. Alton. 1985. Methods

of the U.S.-Japan demersal trawl surveys. In R. G. Bakkala

and K. Wakabayashi (eds.), Results of U.S.-Japan groundfish

investigations in the Bering Sea during May-August 1979, p.

7-26. Int. North. Pac. Fish. Comm. Bull. 44.
THIS PAGE INTENTIONALLY LEFT BLANK
APPENDIX A

Station, Haul, and Catch Data

Appendix A contains computer listings of station and catch

data for all successfully completed standard stations used in the

analysis of the 1991 cooperative U.S.-U.S.S.R. bottom trawl

survey of the Bering Sea shelf. Station locations by haul number

are shown in Figure A-l.

Latitudes and longitudes are in degrees, minutes, and tenths

of minutes. Gear depths are in fathoms and catch weights are in

kilograms. Tow duration is in tenths of hours and distance

fished is in nautical miles.

Page

Figure A-l. Sampling sites by haul number from

the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering

Sea shelf . . . . . . . . . . . . . . . . . . 104

Table A-l. Haul and catch data for successfully

completed tows by the RV Novodrutsk . . . . . 105
Figure A-l. --Sampling sites by haul number from the 1991 cooperative U.S.-U.S.S.R. bottom

trawl survey of the Bering Sea shelf.


Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.
Table A-l .--Continued.




APPENDIX B

Abundance Estimates for Principal Fish Species

Appendix B presents estimates of population size in terms of

number of individuals and biomass estimates in metric tons with

confidence intervals for the principal species of fish sampled

during the 1991 U.S. -U.S.S.R. cooperative survey. Estimates are

given by subarea, standard U.S. area (SA), north shelf (NS),

western shelf (WS), and for all areas combined.

List of Tables

Table

B-l. CPUE, population,

B-2. CPUE, population,

B-3. CPUE, population,

B-4. CPUE, population,

B-5. CPUE, population,

B-6. CPUE, population,

B-7. CPUE, population,

B-8. CPUE, population,

Page

and biomass for walleye pollock . . . 127

and biomass for Pacific cod . . . . . 129

and biomass for yellowfin sole . . . . 131

and biomass for rock sole . . . . . . 133

and biomass for Hippoglossoides spp. . 135

and biomass for Alaska plaice. . . . . 137

and biomass for Atheresthes spp. . . . 139

and biomass for Pacific halibut . . . 141

THIS PAGE INTENTIONALLY LEFT BLANK
127

Table B-l .--CPUE, population, and biomass for walleye pollock.
128

Table B-l .--continued.
129

Table B-2.--CPUE, population, and biomass for Pacific cod.
130

Table B-2 .--Continued.
131

Table B-3.--CWE, population, and biomass for yellowfin sole.
132

Table B-3. --Continued.
133

Table B-4.-- CPUE, population, and biomass for rock sole.
134

Table B-4. --Continued.

BIOMASS
135

Table B-5.--CPUE, population, and biomass for Hippoglossoides spp.

CPUE
136

Table B-5 .--Continued.

BIOMASS
137

Table B-6.--CPUE, population, and biomass for Alaska plaice.

CPUE
138

Table B-6. --Continued.
139

Table B-7.--CPUE, population, and biomass for Atheresthes spp.
140

Table B-7. --Continued.
141

Table B-8. --CPUE, population, and biomass for Pacific halibut.
142

Table B-8. --Continued.
APPENDIX C

Population Estimates by Sex and Size Groups

for Principal Fish Species

Appendix C presents estimates of numbers of individuals by

centimeter interval, sex, and area for the principal species of

fish sampled during the 1991 U.S. -U.S.S.R. cooperative survey.

Estimates are given for the standard U.S. area, north shelf and

western shelf. Estimates of total abundance for yellowfin sole,

rock sole, Hippoglossoides spp., Alaska plaice, and Atheresthes

Spp. are less than those given earlier (Tables 11-15) because of

missing length data.

List of Tables

Table Page

C-l.

C-2.

C-3.

C-4.

C-5.

C-6.

C-7.

Population estimates by sex and size groups for

walleye pollock from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf. . . . . . . 145

Population estimates by sex and size groups for

Pacific cod from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf . . . . . . 149

Population estimates by sex and size groups for

yellowfin sole from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf . . . . . . 154

Population estimates by sex and size groups for

rock sole from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf . . . . . . 155

Population estimates by sex and size groups for

Hippoglossoides spp. from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf . . 156

Population estimates by sex and size groups for

Alaska plaice from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf . . . . . . 158

Population estimates by sex and size groups for

Atheresthes spp. from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf . . . . . . 160
144

List of Tables continued

C-8. Population estimates by sex and size groups for

Pacific halibut from the 1991 cooperative U.S.-U.S.S.R.

bottom trawl survey of the Bering Sea shelf . . . . . . 161
145

Table C-l .--Population estimates by sex and size groups for walleye pollock from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
Table C-l .--Continued.

146

Standard U.S. shelf area
147

Table C-l .--Continued.

North shelf area
148

Table C-l .--Continued.

Western shelf area
149

Table C-2.--Population estimates by sex and size groups for Pacific cod from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
Table C-2 .--Continued.

150

Standard U.S. shelf area
151

Table C-2 .--Continued.

North shelf area
Table C-2. --Continued.

152

Western shelf area
Table C-2. --Continued.

153

Western shelf area
154

Table C-3.--Population estimates by sex end size groups for yellowfin sole from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
155

Table C-4. --Population estimates by sex and size groups for rock sole from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
156

Table C-5 .--Population estimates by sex and size groups for Hippoglossoides spp. from the 1991 cooperative

U.S.-U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
157

Table C-5 .--Continued.

North shelf area
158

Table C-6. --Population estimates by sex and size groups for Alaska plaice from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
Table C-6.--Continued.

159

North shelf area
160

Table C-7.--Population estimates by sex and size groups for Atheresthes spp. from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
161

Table C-B.--Population estimates by sex and size groups for Pacific halibut from the 1991 cooperative U.S.-

U.S.S.R. bottom trawl survey of the Bering Sea shelf.

Standard U.S. shelf area
162

Table C-8. --Continued.

Standard U.S. shelf area
Table C-8. --Continued.

163

Western shelf area
THIS PAGE INTENTIONALLY LEFT BLANK
APPENDIX D

Age-Length Keys for Walleye Pollock

and Pacific cod

Appendix D presents age-length keys for walleye pollock and

Pacific cod by sex and sexes combined from the 1991 cooperative

U.S.-U.S.S.R. bottom trawl survey. Lengths are expressed in

millimeters. Asterisks indicate ages affected by linear

interpolation used to assign length distributions to age classes

that are not represented by collected age data.

List of Tables

Table

D-l. Age length keys for male walleye pollock sampled

during the 1991 U.S.-U.S.S.R. Bering Sea survey .

D-2. Age length keys for female walleye pollock sampled

during the 1991 U.S.-U.S.S.R. Bering Sea survey .

D-3. Age length keys for total walleye pollock sampled

during the 1991 U.S.-U.S.S.R. Bering Sea survey .

D-4. Age length keys for male Pacific cod sampled

during the 1991 U.S.-U.S.S.R. Bering Sea survey .

D-5. Age length keys for female Pacific cod sampled

during the 1991 U.S.-U.S.S.R. Bering Sea survey .

D-6. Age length keys for total Pacific cod sampled

during the 1991 U.S.-U.S.S.R. Bering Sea survey .

Page

. . . 167

. . . 169

. . . 171

. . . 173

. . . 175

. . . 177
THIS PAGE INTENTIONALLY LEFT BLANK


Table D-2.--Age length keys for female walleye pollock sampled during the 1991 U.S.-U.S.S.R. Bering Sea survey.






Table D-5 .--Continued.


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. 

AFSC40 SIGLER, M. F., and H. H. ZENGER, Jr. 1994. Relative abundance of Gulf of Alaska sablefish and

other groundfish based on the domestic longline survey, 1989, 79 p. NTIS No. PB94-204963.

39 ZENGER, H. H., Jr., M. F. SIGLER, and E. R. VAROSI. 1994. Assessment of Gulf of Alaska sablefish

and other groundfish species based on the 1988 National Marine Fisheries Service longline survey, 79

p. NTIS No. PB94-204872.

 

38 LOWRY, L. F., K. J. FROST, R. DAVIS, R. S. SUYDAM, and D. P. DEMASTER. Movements and

behavior of satellite-tagged spotted seals (Phoca largha) in the Bering and Chukchi Seas, 71 p. NTIS No.

PB94-180684.

37 BUCKLEY, T. W., and P. A. LIVINGSTON. 1994. A bioenergetics model of walleye pollock (Theragra

chalcogramma) in the eastern Bering Sea: Structure and documentation, 55 p. NTIS No. PB94-181831.

36 YANG, M-S., and P. A. LIVINGSTON. 1994. Variations in mean stomach content weights of walleye

pollock, Theragra chalcogramma, in the eastern Bering Sea, 32 p. NTIS No. PB94-178084.

35 PARKS, N. B., and F. R. SHAW. 1994. Relative abundance and size composition of sablefish

(Anoplopoma fimbria) in the coastal waters of California and Southern Oregon, 1984-1991. NTIS

number pending.

34 SAMPLE, T. M., and D. G. NICHOL. 1994. Results of the 1990 U.S.-U.S.S.R. cooperative bottom

trawl survey of the eastern and northwestern Bering Sea continental shelf, 183 p. NTIS No. PB94-

181849.

33 WEINBERG, K. L., M. E. WILKINS, R. R. LAUTH, and P. A. RAYMORE, JR. 1994. The 1989

Pacific west coast bottom trawl survey of groundfish resources: Estimates of distribution, abundance, and

length and age composition, 168 p. plus Appendices. NTIS No. PB94-173796.

32 PEREZ, M. A. 1994. Calorimetry measurements of energy value of some Alaskan fishes and

squids, 32 p. NTIS No. PB94-152907.

31 RONHOLT. L. L., K. TESHIMA, and W. D. KESSLER. 1994. The groundfish resources of the

Aleutian Islands region and southern Bering Sea 1980, 1983, and 1986, 351 p. NTIS No. PB94-

152915

30 LORENZ, J. M. 1994. Distribution and habitat of adult salmon in the Situk River, Alaska: Potential

impacts of flooding from Russell Fiord, 27 p. NTIS No. PB94-151859.

29 IGNELL, S. E., L. J. SIMON, and M. L. DAHLBERG. 1994. Estimation of salmonid bycatch in the

1989 Japanese squid driftnet fishery, 45 p. NTIS No. PB94-152105.

28 MORTENSEN, D. G., and H. SAVIKKO. 1993. Effects of water temperature on growth of juvenile

pink salmon (Oncorhynchus gorbuscha), 12 p. NTIS No. PB94-145349.

27 LOW, L-L. (coordinator). 1994. Status of living marine resources off Alaska, 1993, 110 p. NTIS No.

PB94-149846.

26 LOW, L-L. (coordinator). 1993. Status of living marine resources off the Pacific coast of the United

States for 1993, 90 p. NTIS No. PB94-133733.