NOAA Technical Memorandum NMFS-AFSC-89

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

March 1998

by

M. E. Wilkins, M. Zimmermann, and K. L. Weinberg

The 1995 Pacific West Coast

Bottom Trawl Survey of Groundfish

Resources: Estimates of Distribution,

Abundance, and Length and

Age Composition
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:

Wilkins, M. E., M. Zimmermann, and K. L. Weinberg. The 1995 Pacific

west coast bottom trawl survey of groundfish resources: Estimates of

distribution, abundance, and length and age composition. U.S. Dep.

Commer., NOAA Tech. Memo. NMFS-AFSC-89, 138 p. plus

Appendices.

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

the National Marine Fisheries Service, NOAA.
March 1998

NOAA Technical Memorandum NMFS-AFSC-89

by

M. E. Wilkins, M. Zimmermann, and K. L. Weinberg

The 1995 Pacific West Coast

Bottom Trawl Survey of Groundfish

Resources: Estimates of Distribution,

Abundance, and Length and

Age Composition

Resource Assessment and Conservation Engineering Division

Alaska Fisheries Science Center

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

Seattle, WA 98115-0070

U.S. DEPARTMENT OF COMMERCE

William M. Daley, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Under Secretary and Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Administrator for Fisheries
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iii

ABSTRACT

The 1995 Alaska Fisheries Science Center West Coast

triennial bottom trawl survey was conducted to assess stocks of

groundfish inhabiting the continental shelf waters off the coasts

of California, Oregon, Washington, and British Columbia. This

was the seventh survey in an ongoing series to monitor long-term

trends in the distribution and abundance of these groundfish

populations.

The objectives of the 1995 survey were similar to those of

the previous surveys in the series. We have made minor changes

in the survey design over the years. The three most recent

surveys have shifted emphasis away from estimating rockfish

abundance, as had been the case from 1977 through 1986, toward

assessing a broader range of groundfish species. The current

design also focuses upon precisely estimating the near-bottom

component of the Pacific hake and juvenile (age l+) sablefish

resource. The survey encompassed the coastal waters from Pt.

Conception, California, to central Vancouver Island, British

Columbia (34°30'-49°40'N lat.). The depth range of the survey

was extended in 1995 for more complete coverage of the habitat of

shelf rockfish. The 1980-86 surveys had covered depths from

55-366 m; in 1995, we surveyed between 55 and 500 m. A total of

533 stations were occupied, of which 522 were successfully

sampled. Catches included 155 different species of fish and 112

different species of invertebrates.
iv

This report documents survey design and the methods used in

1995, summarizes biological and environmental data collected, and

presents the results of standard analyses of distribution,

abundance, and biological parameters for the commercially

important groundfish species in the region. Data on water

temperature, catch composition, relative abundance, and

geographic distribution are reported. Estimates of biomass,

population abundance, length composition and age composition are

also presented. Data appendices are located in a separate

companion volume.
V

CONTENTS

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

SURVEY METHODS ...................

Survey Period and Sampling Area ........

Vessels and Sampling Gear ...........

Survey Area Stratification ..........

Trawl Station Allocation ...........

Trawling Procedures ..............

Catch Sampling and Oceanographic Data Collection

Data Analyses . . . . . . . . . . .

RESULTS . . . . . . . . . . . . . . . . .

Haul, Catch, and Biological Data .

Temperature Data . . . . . . . . .

Relative Abundance . . . . . . . .

Biomass and Population Estimates .

Length Composition . . . . . . . .

Age Compositions . . . . . . . . .

Length-Weight Relationships . . . .

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CITATIONS................................................... 27
INTRODUCTION

In 1995, the seventh in an ongoing series of groundfish

assessment surveys of the continental shelf resources off the

coasts of California, Oregon, Washington, and British Columbia

was carried out by the Resource Assessment and Conservation

Engineering (RACE) Division of the Alaska Fisheries Science

Center (AFSC). These bottom trawl surveys, initiated in 1977 and

repeated triennially, have been designed to provide resource

managers with fishery-independent data about the distribution,

abundance, and biological characteristics of several commercially

important species, particularly Pacific hake (also known as

Pacific whiting), Merluccius productus, sablefish, Anoplopoma

fimbria, and many of the shelf and slope rockfish (genus

Sebastes) species (Wilkins 1996). Hydroacoustic surveys of the

off-bottom component of the Pacific hake population have been

conducted concurrently with these bottom trawl surveys by the

Midwater Assessment and Conservation Engineering (MACE) Task of

the RACE Division.

The first of these bottom trawl surveys, conducted in 1977

(Gunderson and Sample 1980), sampled between Pt. Hueneme,

California, (34°00'N lat.) and the U.S. -Canada border in depths

ranging from 91 to 457 m. The sampling effort was stratified by

depth and latitude according to fishery catch information. The

following two surveys, conducted in 1980 (Coleman 1986) and 1983

(Weinberg et al. 1984), emphasized obtaining better biomass

estimates of canary (Sebastes pinniger) and yellowtail rockfish
2

(S. flavidus), while maintaining the important general goals of a

multispecies monitoring program. In 1980, strata were adjusted

and sampling depths shifted to cover the 55-366 m depth interval,

while the latitudinal boundaries extended from Monterey Bay,

California (36°48'N lat.), to northern Vancouver Island, British

Columbia (50°00'N lat.). The same area was surveyed using the

same survey design in 1983 but only extended as far north as

Vancouver Island's Estevan Point (49°15'N lat.). The results of

the 1980 and 1983 surveys indicated that further work was needed

to improve the precision of canary and yellowtail rockfish

abundance estimates. Consequently, in 1986 the sampling effort

was reallocated to concentrate on the 92-219 m depth interval

north of 42°35'N lat., where canary and yellowtail rockfish were

thought to be most abundant (Coleman 1988). Results of these

first four surveys were also used to examine trends in the

distribution and abundance of 14 of the more commercially

important groundfish species (Dark and Wilkins 1994).

Despite efforts to improve the precision of rockfish

abundance estimates over the first four iterations of the

triennial survey, the large variances of the estimates remained a

problem. We concluded that precise estimates of rockfish

abundance were not possible using current trawl survey methods

and realistic sampling levels. It was clear that higher priority

should be given to obtaining the information that our survey was

able to provide well. Consequently, beginning in 1989 the

triennial bottom trawl survey was designed to monitor a broad
3

range of demersal species and also focus on providing precise

estimates of the demersal component of the Pacific hake stock and

sablefish pre-recruits (age l+) (Weinberg et al. 1994, Zimmermann

et al. 1994). Weinberg (1994) used the results of the 1977-92

surveys to describe rockfish community structure and species

assemblages. His findings, as well as recent assessments of

slope and shelf rockfish stocks (Rogers et al. 1996) indicated

that more complete depth coverage of the habitats of these

species during our surveys would improve our ability to assess

them. In 1995, we redirected a portion of our samples from four

small areas of high density sampling for Pacific hake and

sablefish and placed them in a new, deeper depth stratum between

367 and 500 m that extended along the entire coast.

The specific objectives of the 1995 survey were

1) to describe and assess the demersal component of the

Pacific hake resource;

2) to describe and assess the abundance of the pre-recruit

component of sablefish, specifically those 1.5 years old

because the abundance of these pre-recruits estimated from

trawl survey data has been shown to be consistent with that

inferred from commercial catch levels;

3) to describe and assess shelf and slope rockfish stocks

throughout their entire depth ranges;

4) to monitor the status of other important groundfish

stocks;
4

5) to determine the biological characteristics (e.g., size

and age compositions, size at maturity, length/weight

relationships and feeding habits) of key groundfish

species;

6) to continue studies on the movement of juvenile

sablefish through tagging;

7) to collect oceanographic data describing the habitat,

including surface temperatures, bottom temperatures, and

water column temperature profiles at each sampling station;

and

8) to collect samples requested for special studies

conducted by scientists at various fishery agencies and

academic institutions.

This report documents the survey design and field

procedures used, summarizes the data collected, and presents the

results of the standard PACE analyses. Included are summaries of

catches, relative densities, distributions, and estimates of

biomass, population abundance, and size compositions for selected

species. Age compositions are also included for six species for

which ages have been determined from otoliths or fin ray

collections and length-weight relationships are described for

many groundfish species. For the sake of brevity, our discussion

concentrates on the primary target species of this survey,

Pacific hake and sablefish, in the areas of most concern to
5

management. Unabridged printouts of the results of analyses,

which include numerous species, are available upon request as

appendices bound in a separate volume. Electronic data files and

files containing results of analyses (e.g., size and age

composition) can also be obtained from the authors upon request.

SURVEY METHODS

Survey Period and Sampling Area

The 1995 survey was conducted from 6 June to 24 September,

which is slightly earlier than the time period of previous

triennial surveys (mid-July through September). Operations began

off Pt. Conception, California, and proceeded northward to

central Vancouver Island off Clayoquot Sound (34°30'-49°40' N

lat.). We sampled stations between the depths of 55 and 500 m.

The survey area has started at Point Conception since 1989 to

allow us to detect concentrations of juvenile Pacific hake and

sablefish which may be present only between Point Conception and

Monterey Bay. Stations in Canada were sampled to help estimate

density at the northern limit of the Pacific hake distribution

and to collect more complete data sets on transboundary stocks

such as yellowtail rockfish, Pacific ocean perch, Sebastes

alutus, and lingcod, Ophiodon elongatus.

Vessels and Sampling Gear

Two trawlers, the R/V Alaska and the F/V Vesteraalen, were

chartered to conduct the bottom trawl survey. Pertinent details
6

about these vessels are presented in Table 1. Each vessel was

equipped with dual net reels, modern electronics, and Loran C and

Global Positioning System (GPS) navigational aids.

The standard RACE high-opening Nor'eastern trawl,

constructed of polyethylene mesh and equipped with bobbin roller

gear, was used aboard both vessels throughout the 1995 survey

(Fig. 1). This trawl has a 27.2 m headrope and a 37.4 m

footrope. All trawls were rigged consistently with RACE survey

gear standards employing three 55 m dandylines (1.59 cm steel

cable) connected to each wing and fished with 2.1 x 1.5 m steel

V-doors weighing approximately 567 kg each.

Measurements of the trawl's horizontal (wingtip to wingtip)

and vertical opening (center of headrope to bottom) were

collected throughout the duration of 413 (79%) of the

successfully completed tows using a SCANMAR net mensuration

system. Mean net widths and heights were calculated for each

successfully measured trawl haul. The overall mean path width of

the net was 12.53 m (range 10.09-14.49 m) for all measured trawl

hauls by the R/V Alaska and 13.92 m (range 10.95-16.58 m) for all

measured trawl hauls by the F/V Vesteraalen. In those instances

when horizontal measurements were unavailable, the average net

width (m) was estimated using the following relationships (C.

Rose, Alaska Fish. Sci. Cent., pers. commun., April 1996):
7

R/V Alaska

Net width = 10.76 m if scope (wire out) < 221 m

= 12.05 m if scope > 221 m and < 360 m

= 12.70 m if scope > 360 m

F/V Vesteraalen

Net width = 15.74 - 875.38 / S

where: S = scope (m).

These equations were derived by examining the relationship

between mean net width and a set of variables known to be

important in determining the horizontal opening of the net (Rose

1993).

Survey Area Stratification

The 1995 triennial survey sampled the entire survey area

with a nearly uniform sampling density, which was similar to the

low-density levels used in prior (1977-92) surveys. In the two

previous surveys, the shallow depths (<183 m) in four latitudinal

strata had been sampled at a higher rate to increase the

precision of juvenile sablefish abundance estimates. The higherdensity sampling in these areas was scaled back to normal density

for the 1995 survey. Ten latitudinal strata of similar size were

used during the analyses to ensure that catch rates of various

species were extrapolated to meaningful areas of their respective

habitats.
8

The survey area was also stratified by depth, since most

groundfish species in the area exhibit a strong depth range

preference. All previous West Coast triennial surveys have been

divided into two major depth strata: 55-183 m representing a

continental shelf habitat and 184-366 m representing the shelf

break and the uppermost continental slope. Pacific hake and

juvenile sablefish catch rates, in particular, are usually

significantly higher in the shallower stratum. An additional

deeper depth stratum (366-500 m) was added to the design of the

1995 survey so that the survey area would encompass the entire

depth range of slope rockfish species. The survey area

stratification is displayed schematically in Figure 2.

Trawl Station Allocation

A systematic-random design was used to allocate trawl

stations to best achieve the primary survey objectives, which

were to estimate the abundance and biological characteristics of

Pacific hake and juvenile sablefish stocks and concurrently

monitor the condition of a broader range of commercially

important groundfish species. Tracklines were laid across the

survey area from the 55 m isobath due west extending to the 500 m

isobath at intervals of 18.5 km along the coast. Stations were

randomly placed along tracklines at the rate of one station per

7.4 km in the shallow stratum and one station per 9.3 km in the

two deeper stratum. At least one station was assigned to each

depth stratum along each trackline segment. A total of 610
9

stations were established. The number of stations allocated to

each stratum, as well as the number successfully sampled, are

shown in Table 2.

Trawling Procedures

Stations were located using GPS and then surveyed with the

echo sounder prior to towing. 'If the terrain was determined to

be too rugged to tow upon successfully, then an alternative site

was searched for within a l-nautical mile radius of the original

site. If no favorable ground was located within about 2 hours,

the station was declared untrawlable and abandoned.

Before starting the survey, each vessel conducted an

exercise to empirically establish the proper amount of trawl warp

to deploy at a given depth to assure that the net would fish

solidly on the bottom. We did this by deploying the trawl and

towing it at a speed of 1.54 m/sec (3.0 knots) over deep water,

increasing the length of trawl warp by 46 m (25 fm) intervals and

allowing the trawl to settle to an equilibrium depth at each warp

length. A micro-bathythermograph (MBT) was attached to the trawl

headrope during this exercise and the settling depth was recorded

for different trawl warp lengths. We tabulated the minimum

length of trawl warp needed to fish the trawl at any given bottom

depth and paid out an additional 90-150 m of warp to ensure solid

bottom contact.

We made concerted efforts to deploy the sampling trawl in

the same manner at each station so as to obtain standard samples.
1 0

Skippers set the trawl and payed out the prescribed amount of

trawl warp while traveling faster than the target towing speed.

The vessel was slowed as the brakes were set on the trawl winches

and the gear was allowed to sink toward bottom. Before reaching

bottom, the speed of the vessel was increased to the target

towing speed of 1.54 m/sec (3.0 knots) so that the trawl was

nearly in its fishing configuration when it contacted the bottom.

We used information from the Scanmar, MBT, and GPS to determine

when and where the trawl reached bottom and settled into its

equilibrium fishing configuration. After achieving equilibrium,

the trawl was towed at 1.54 m/sec for 30 minutes. The net was

retrieved as quickly as possible to clearly delineate the time

and position of the endpoint of the sample. Skippers tried to

maintain a constant depth while towing. If the gear was damaged

during the tow severely enough to affect catch composition, the

haul was considered unsatisfactory and the station was either

repeated or abandoned. Unsuccessful tows were not used to

calculate biomass or population estimates. During the time the

two vessels were working together, they fished alternate

tracklines to enable comparison of their relative fishing powers.

Catch Sampling and Oceanographic Data Collection

The procedures for catch processing documented by Gunderson

and Sample (1980) were used in 1995. Briefly, catches which fit

on the sampling table (about one metric ton (t)) were processed

entirely, while larger catches were either weighed by an
11

electronic load cell (up to 4.5 t) or measured volumetrically,

then subsampled following methods described by Hughes (1976).

Catches were then sorted by species, weighed, and enumerated.

Fork length measurements (in centimeters) were obtained by sex

for primary and secondary target species1 whenever they were

caught. Lengths were also taken for other major components of

the catch when time allowed.

Otoliths (used for age determination), along with

individual specimen weight and maturity data, were collected from

a variety of species. Collections for Pacific hake and sablefish

were stratified by length interval (5 otoliths/sex/cm) for

biological subareas. Collections for canary and splitnose

rockfish (S. diploproa) were stratified by size intervals of 5 cm

or more (50-100 otoliths/interval) for the entire survey area.

Random collections were made for bocaccio (S.paucispinis),

yellowtail rockfish, Pacific ocean perch, darkblotched rockfish

(S. crameri), yelloweye rockfish (S. ruberrimus), yellowmouth

rockfish (S. reedi), chilipepper (S. goodei), silvergray (s.

brevispinis) rockfish, sharpchin rockfish (S. zacentrus), and

redstripe rockfish (S. proriger). Fin rays were collected from

lingcod for determining age. We collected stratified samples of

individual fish weights (5 observations per sex/cm interval from

each state and from Canada) from several additional commercially

'Primary target species are Pacific hake and sablefish.

Secondary target species include canary rockfish, yellowtail

rockfish, bocaccio, chilipepper, Pacific ocean perch, sharpchin

rockfish, splitnose rockfish, darkblotched rockfish, yelloweye

rockfish, yellowmouth rockfish, silvergray rockfish, and lingcod.
12

important species. Other requests for meristic data, and for

samples of stomach contents, tissues, and whole fish were also

fulfilled as time allowed.

Surface temperatures were measured with bucket thermometers

and MBTs. Water column temperature profiles and bottom

temperatures were also collected with MBTs.

Data Analyses

Several analyses are performed routinely on RACE bottom

trawl survey data. These include:

1) estimation of relative abundance,

2) estimation of population biomass,

3) estimation of population numbers, and

4) estimation of the population's size composition.

We use the area-swept method described by Gunderson and Sample

(1980) to calculate catch rates, which are in turn used to

estimate population biomass and numbers. Briefly, this method

entails standardizing species catch rates from each station into

catch per unit effort (CPUE) in terms of kilograms or numbers per

hectare trawled (kg/ha, no./ha) and calculating the arithmetic

mean CPUE for each sampling stratum. Relative abundance (mean

CPUE) of each species is then calculated for each International

North Pacific Fisheries Commission (INPFC) area as the sum of the

mean CPUEs of each appropriate sampling stratum weighted by their

respective stratum areas. Population biomass and numbers in each

stratum are estimated by multiplying the stratum mean CPUE by the
13

stratum area. Stratum estimates are summed to provide biomass

and population estimates for various portions of the survey area

(INPFC areas, U.S. waters, etc.). In cases where our sampling

strata straddle more than one INPFC area, we expand the overall

sampling stratum mean CPUE to the area of that portion of the

sampling stratum lying within the INPFC area.

The size composition of each species was estimated in a

manner similar to the population estimate. Length-frequency data

collected at each station were weighted by the CPUE (number/ha)

of that species at that station, summed over all hauls in a

stratum, and expanded to the stratum population estimate to

estimate the population. As with population estimates, stratum

estimates were summed to derive the estimated size compositions

for various portions of the survey area.

Ages were determined from otolith or fin ray samples

collected from groundfish species. The age compositions of these

stocks were estimated by multiplying their population size

composition by age-length keys (matrices of length vs. age)

constructed from the age data from corresponding or appropriately

pooled strata.
14

RESULTS

Haul, Catch, and Biological Data

During the 1995 survey, 522 of the 610 stations were

successfully sampled within the 55-500 m depth bounds. Twentyfour tows were unsuccessful due to damaged trawls and 76 stations

were abandoned due to untrawlable bottom. Sampling density

ranged from 0 to 11.97 hauls per 1,000 km2 in the shallow strata,

from 3.73 to 22.83 hauls per 1,000 km2

 in the middle strata, and

from 3.13 to 19.21 hauls per 1,000 km2

 in the deep strata (Table

2). Over the entire survey area, the sampling density was

slightly higher in the deep strata (12.66 hauls per 1,000 km2

)

than in the middle (10.25 hauls per 1,000 km2) or the shallow

(7.64 hauls per 1,000 km2) strata. Overall, the average sampling

density was also slightly higher in the U.S. portion of the

survey area than in Canada. Figure 3 shows the location of

successful tows by depth stratum.

A total of 155 fish species representing 54 families were

identified to the species level over the course of the survey

(Table 3). Members from several additional families were taken

but identified only to genus. Table 3 also lists the frequencies

of occurrence, depth ranges, and the range of distribution by

latitude for all fish taxa identified in trawl samples. The

greatest number of species taken (n=39) belonged to the rockfish

(Scorpaenidae) family, followed by the flatfishes (Bothidae,
15

Pleuronectidae, and Soleidae) with 20, and the sculpins

(Cottidae) with 11 species.

We measured the length of 313,327 fish. A summary of the

number of fish measured is presented in Table 4 by species, INPFC

area, and depth stratum. The number of specimens collected for

other biological samples (age structures, length-weight

relationships, maturity, food habits, etc.) are reported in Table

5. Appendix A (see separate Data Appendices volume) summarizes

the catch data by haul for each vessel.

Temperature Data

Sea surface temperatures measured at 541 stations using a

bucket thermometer ranged from 8.7° to 18.2°C. The overall mean

surface temperature was 13.6°C. Temperature profiles of the

water column (surface to bottom) were collected at 526 stations.

Bottom temperatures from these stations ranged from 5.4" to

9.7°C, averaging 7.3°C. Figures 4 and 5 illustrate the observed

surface and bottom temperatures, respectively, by latitude from

the 1995 survey and compare these data with temperature data

collected in previous triennial surveys.

Relative Abundance

The 20 most abundant groundfish species are presented by

depth stratum for the individual INPFC areas in Table 6. The

complete listings of the relative abundance of all fish ranked by

mean CPUE for each INPFC area and depth stratum are presented in
16

Appendix B (see separate volume of Data Appendices). Relative

catch rates of all fish and invertebrate species are also ranked

in Appendix B by depth stratum for all survey areas combined.

Average total fish densities were highest in the Monterey INPFC

area (212.6 kg/ha), followed by the Columbia (190.1 kg/ha),

Vancouver (148.4 kg/ha), Conception(l04.3 kg/ha), and Eureka

(88.2 kg/ha) INPFC areas.

Pacific hake was the most abundant species overall,

accounting for 53% of the total survey finfish CPUE (88.5 kg/ha)

and 57% in U.S. waters alone (98.2 kg/ha). The highest average

CPUE for Pacific hake was in the Columbia INPFC area

(126.6 kg/ha), where it comprised 66% of the area's total finfish

CPUE. Pacific hake were least abundant in the Conception INPFC

area (15.1 kg/ha) where it accounted for 14.5% of all fish.

Besides the Columbia INPFC area, Pacific hake also dominated

samples in the U.S. portion of the Vancouver INPFC area (122.7

kg/ha and in the Monterey (115.1 kg/ha) and Eureka (33.1 kg/ha)

INPFC areas.

Dover sole (Microstomus pacificus) and Pacific sanddab

(Citharichthys sordidus) were the second and third most abundant

fish species, respectively, both surveywide and in U.S. waters.

Mean Dover sole catch rates were 8.4 kg/ha in both areas, or

about 5% of the finfish CPUE. Pacific sanddab catch rates

averaged 7.2 kg/ha surveywide and 7.8 kg/ha in U.S. waters, or

about 4.5% of the finfish CPUE.
17

Sablefish ranked fourth in relative abundance among all

species both surveywide (5.7 kg/ha) and in U.S. waters

(5.5 kg/ha), accounting for 3% of the catch in both areas. Mean

catch rates of sablefish were highest in the Columbia INPFC area

(8.1 kg/ha), followed by the Eureka (7.2 kg/ha), Vancouver (5.0

kg/ha, Conception (3.2 kg/ha), and Monterey (2.6 kg/ha) INPFC

areas. Sablefish accounted for between 1.2% and 8.1% of INPFC

area fish catches.

Catch composition and relative densities varied widely

among geographic areas. In the total survey area, the four most

abundant species after Pacific hake (88.5 kg/ha) were Dover sole

(8.5 kg/ha), Pacific sanddab (7.2), sablefish (5.7 kg/ha), and

arrowtooth flounder (Atheresthes stomias) (5.0 kg/ha). These

five species as a group accounted for 69% of finfish CPUE. In

U.S. waters only, four of the same species were among the five

most abundant. Pacific hake (98.2 kg/ha) was most abundant,

followed by Dover sole (8.4 kg/ha), Pacific sanddab (7.8 kg/ha),

sablefish (5.5 kg/ha), and splitnose rockfish (4.9 kg/ha).

Moving from south to north and listed in order of abundance, the

five most prominent species in the Conception INPFC area were

splitnose rockfish (18.0 kg/ha), Pacific hake, Dover sole,

stripetail rockfish (S. saxicola), and spotted ratfish

(Hydrolagus collei); in the Monterey INPFC area: Pacific hake

(115.1 kg/ha), Dover sole, stripetail rockfish, splitnose

rockfish, and chilipepper; in the Eureka INPFC area: Pacific

hake (33.1 kg/ha), Dover sole, sablefish, Pacific herring, chub
1 8

mackerel (Scomber japonicus); in the Columbia INPFC area:

Pacific hake (126.6 kg/ha), Pacific sanddab, sablefish, Dover

sole, and jack mackerel (Trachurus symmetricus); in the U.S.

Vancouver INPFC area: Pacific hake (122.7 kg/ha), spiny dogfish

(Scpalus acanthias), Dover sole, arrowtooth flounder, and Pacific

halibut (Hippoglossus stenolepis); and in the Canadian Vancouver

INPFC area: arrowtooth flounder (27.7 kg/ha), Pacific hake, spiny

dogfish, Dover sole, and Pacific ocean perch.

The catch composition also varied among depth strata. In

the shallow stratum (55-183 m) for the entire survey area,

Pacific hake (130.4 kg/ha) dominated catches, followed by Pacific

sanddab, spiny dogfish, jack mackerel, and arrowtooth flounder.

The five most abundant species in the middle depth stratum (184-

366 m) were Pacific hake (30.6 kg/ha), splitnose rockfish,

stripetail rockfish, sablefish, and Dover sole. The five most

abundant species in the deep stratum (367-500 m) were Dover sole

(23.1 kg/ha), sablefish, Pacific hake, rex sole (Glyptocephalus

zachirus), and shortspine thornyhead (Sebastolobus alascanus).

Maps of the geographical distribution of the primary and

secondary target species, based on catch rates at each station,

are presented by species in Figures 6-34 in alphabetical order.

Yelloweye and yellowmouth rockfish, despite being secondary

target species, were not mapped because they were caught so

infrequently. Distribution maps of the following selected

additional groundfish species also appear:
19

Arrowtooth flounder

English sole

Pacific halibut

Redstripe rockfish

Spiny dogfish

Widow rockfish

Aurora rockfish Dover sole

Greenstriped rockfish Longspine thornyhead

Pacific sanddab Petrale sole

Rougheye rockfish Shortbelly rockfish

Stripetail rockfish Shortspine thornyhead

The distribution of each species is presented by relative

density classifications (high, moderate, and low) in the

distribution maps. For each species, all non-zero station catch

rates were sorted in decreasing order and classified in either

the top l0%, middle 30%, and lowest 60% of the catch rate values.

Stations where the species was not caught are also shown. The

distribution of sampling effort should be considered when viewing

these charts since heavier sampling in an area may give the

impression of high densities when, in fact, CPUE was only

moderate or low.

Biomass and Population Estimates

Abundance estimates in metric tons of biomass and

associated 90% confidence intervals are presented for various

taxa in the total survey and by INPFC area and depth stratum in

Tables 7-10. Similarly, estimates of population numbers are

presented for important species groups in Tables 11-14. Detailed

listings of biomass and population estimates are presented for

the major species in Appendix C in the Data Appendices volume.

The on-bottom component of the Pacific hake population was

estimated to be 586,200 t for the entire area (Table 7). Two of

the five INPFC areas accounted for 75% of the total estimated

Pacific hake biomass: 49% in the Columbia INPFC area and 26% in
20

the Monterey area. Six percent (34,839 t) was in Canadian

waters. Pacific hake biomass was distributed mostly in the

shallow stratum (552,003 t or 94% of the total estimate), with

28,436 t (4%) in the middle depth stratum and 5,761 t (1%) in the

deep stratum (Tables 8-10).

The total sablefish biomass estimate was 30,472 t (Table

7). The Columbia and Vancouver INPFC areas contributed 54% and

25%, respectively, of the total sablefish biomass between the

depths of 55 and 500 m. Sablefish in Canadian waters (6,364 t)

amounted to 21% of the total. The distribution of sablefish

biomass was nearly uniform in the two shallower strata, with

11,869 t (39% of the total) in the shallow stratum and 11,814 t

(39%) in the middle depth stratum. We estimated 6,788 t of

sablefish (22%) in the deep stratum (Tables 8-10).

We should warn readers that the biomass and population

estimates presented are likely to be conservative since only a

portion of the stock may be available to the bottom trawl and

some escapement may occur. For lack of data on species-byspecies catchability, abundance calculations are based on the

assumption that all fish in front of the trawl and between the

wingtips are captured. The degree of conservative bias will vary

among species. For instance, a large portion of the total

Pacific hake stock is pelagic and would be missed by a bottom

trawl. Also, because roller gear is used, escapement underneath

the trawl is likely to occur, particularly for the flatfish
21

species. Furthermore, the survey covers limited portions of the

depth and geographic range of many of these species.

This survey is the main source of fishery-independent

information on the abundance, distribution, and length and agecomposition for most of these species. Other fishery-independent

data sources used for stock assessments include the AFSC echo

integration/midwater trawl survey of the West Coast Pacific hake

resource and the AFSC bottom trawl survey of upper continental

slope groundfish resources (sablefish, Dover sole, and

thornyheads). Stock assessment scientists utilize our survey

results, along with commercial catch and effort data, in order to

set the most appropriate catch levels.

Length Composition

Estimated population length compositions for several

groundfish species are presented in alphabetical order by sex and

INPFC area (Figs. 35-68). The length compositions for Pacific

hake and sablefish include separate presentations of their length

compositions by depth stratum. The length compositions of the

remaining species are presented for the combined depths only.

Computer files of estimated length compositions, by sex and INPFC

area, are available upon request for any species from which

length data were collected.

Three length modes were evident in the Pacific hake length

distributions. For the total survey area, there was a small peak

at 34.5 cm, but the majority of the population was found in two
22

peaks centered at 25 cm and 46.5 cm (Fig. 46). The overall

population mean length was 36.1 cm. Hake ranged in length from

4 to 83 cm. The male and female components of the population

were very similar with the average length of females (36.8 cm)

being only slightly longer than that of the males (35.3 cm). The

Conception INPFC area contained mostly small (<30 cm) and

intermediate-sized (30-40 cm) Pacific hake, the Monterey INPFC

area contained mostly intermediate-sized and large (>40 cm) hake,

and north of the Monterey INPFC area we found only small and

large hake. Pacific hake lengths averaged 30.9, 38.9, 39.6,

34.5, 41.1 and 31.4 cm in the Conception, Monterey, Eureka,

Columbia, U.S. Vancouver and Canadian Vancouver INPFC areas,

respectively. Mean lengths of Pacific hake generally increased

with depth except for in the Columbia INPFC area, where 40-50 cm

fish dominated the shallow stratum (Fig. 47). In other areas

hake were slightly longer in the middle strata than in the

shallow strata. Hake in the deep strata were generally much

longer than in

Sablefish

bounds of this

data from this

shallower strata.

inhabit a wide range of depths, exceeding the

survey. Its size distribution can be described by

survey for only the shallow end of its range. At

these depths, the estimated length distribution for sablefish was

generally bimodal with a narrow peak at 38 cm and a broader peak

around 53 cm (Fig. 57). A small group of fish between 15 and

25 cm long were also seen in the northern part of the survey

area; interestingly these were seen primarily at the deepest
23

stations of the Vancouver and Columbia INPFC areas (Fig. 60).

Sablefish samples from throughout the survey area ranged from 14

to 86 cm in length, but the overall average length of the

population was 46.2 cm. The average length of males was 46.7 cm

and the average length of females was 47.4 cm. Juvenile

sablefish (<42 cm) accounted for the majority of the populations

in the Conception (55%), Monterey (64%), and U.S.-Vancouver (68%)

INPFC areas, and somewhat less than half (34-45%) of the

populations in all other areas. Mean sablefish lengths were

lower in the Conception (41.0 cm), Monterey (41.4 cm), and U.S.-

Vancouver (39.0 cm) INPFC areas than in the remaining areas,

where mean length ranged from 46.6 to 51.1 cm. Mean sablefish

lengths in deep strata were greater than in the shallow strata in

all INPFC areas (Figs. 58-60) except in the Columbia and

Vancouver INPFC areas, where fish shorter than 25 cm dominated

the sablefish catch.

Age Compositions

Otoliths or dorsal fin rays were collected from specimens of

24 groundfish species (Table 5) to determine their ages. To

date, ages have been determined for the structures collected from

Pacific hake, lingcod, bocaccio, chilipepper, yellowtail

rockfish, and darkblotched rockfish. The age composition of

these species was estimated and is presented in Figures 69-74.

For this report, each of these species has been treated as a

single, homogenous stock and all age data collected during the
24

1995 survey has been used to estimate the species's length-age

relationship. When it has been appropriate, the age compositions

of

in

by

several of these resources have been estimated and presented

more geographic detail in stock assessment documents published

the Pacific Fishery Management Council.

The age composition of the Pacific hake resource (Fig. 69)

shows that the population is primarily supported by fish from

four or five year classes spawned in 1980, 1984, 1987, 1993, and

1994. Few fish from any other year class contribute to the size

of this resource. The lingcod resource, on the other hand, is

represented more evenly by fish between 1 and 7 years old

(Fig. 70). Bocaccio younger than age 4 were the most abundant in

the 1995 survey area (Fig. 71), though some older age groups,

particularly those between 8 and 12 years old, contributed

significantly to the size of the population.

The three other rockfish species which have been aged

exhibit similar profiles. These fish generally become fully

available to the survey and commercial trawl gear when they are

between 3 and 6 years old. Prior to that, they can be detected

by the survey trawl when the younger age groups are notably

abundant. Following their full recruitment to the gear, the age

composition figures (Figs. 72-74) track the relatively constant

decrease in their abundance as they age, a normal result of

natural and fishing-induced mortality.
25

Length-Weight Relationships

From the individual fish weight samples, we determined

length-weight relationships using a linear least-squares

regression model on log-transformed data. Results of these

analyses are summarized in Table 15 for males, females, and for

all fish combined (including unsexed fish). The following

equations describe the relationships for Pacific hake and

sablefish (sexes combined):

for males

for females

for all sexes

for males

for females

for all sexes
26

ACKNOWLEDGMENTS

Many individuals at the AFSC were involved with successfully

conducting the 1995 West Coast triennial bottom trawl survey at

sea, summarizing the results, and preparing this manuscript. We

would like to express our thanks to the captains and crew aboard

the R/V Alaska and the F/V Vesteraalen for providing safe and

efficient platforms from which to conduct our operations. We are

also appreciative to the National Marine Fisheries Service (NMFS)

biologists from the AFSC, Northwest Fisheries Science Center,

Southwest Fisheries Science Center, and NMFS Headquarters and

scientists from the Scripps Institute of Oceanography, various

other academic institutions, and the Oregon Department of Fish

and Wildlife who participated in this survey. Finally, the

authors would like to thank Frank Shaw and Bob Lauth for their

instrumental roles in editing the data.
27

CITATIONS

Coleman, B. A. 1986. The 1980 Pacific west coast bottom trawl

survey of groundfish resources: Estimates of distribution,

abundance, length and age composition. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-F/NWC-100, 181 p.

Coleman, B. A. 1988. The 1986 Pacific west coast bottom trawl

survey of groundfish resources: Estimates of distribution,

abundance, length and age composition. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-F/NWC-152, 145 p.

Dark, T. A., and M. E. Wilkins. 1994. Distribution, abundance,

and biological characteristics of groundfish off Washington,

Oregon, and California, 1977-1986. U.S. Dep. Commer., NOAA

Tech. Rep. NMFS 117, 73 p.

Gunderson, D. R., and T. M. Sample. 1980. Distribution and

abundance of rockfish off Washington, Oregon, and California

during 1977. Mar. Fish. Rev. 42(3-4):2-16.

Hughes, S. E. 1976. System for sampling large trawl catches of

research vessels. J. Fish. Res. Board Can. 33:833-839.

Rogers, J. B., D. Kamikawa, T. Builder, M. Kander, M. Wilkins, M.

Zimmermann, F. Wallace, and B. Culver. 1996. Status of the

remaining rockfish in the Sebastes complex in 1996 and

recommendations for management in 1997. Appendix E in:

Pacific Fishery Management Council. 1996. Appendix Volume

II: Status of the Pacific Coast Groundfish Fishery Through

1996 and Recommended Biological Catches for 1997: Stock

Assessment and Fishery Evaluation. (Document prepared for

the Council and its advisory entities.) Available from

Pacific Fishery Management Council, 2130 SW Fifth Avenue.

Suite 224, Portland, Oregon 97201.

Rose, C. S. 1993. Trawl width variation and its effects on

groundfish trawl survey results. Ph.D. diss., Univ.

Washington, Seattle, WA, 218 p.

Weinberg, K. L. 1994. Rockfish assemblages of the middle shelf

and upper slope off Oregon and Washington. Fish. Bull.,

U.S. 92(3):620-632.

Weinberg, K. L., M. E. Wilkins, and T. A. Dark. 1984. The 1983

Pacific west coast bottom trawl survey of groundfish

resources: Estimates of distribution, abundance, age and

length composition. U.S. Dep. Commer., NOAA Tech Memo.

NMFS-F/NWC-70, 376 p.
28

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. U.S. Dep.

Commer., NOAA Tech. Memo. NMFS-AFSC-33, 168 p.

Wilkins, M. E. 1996. Long term trends in abundance: Results of

triennial bottom trawl surveys of west coast groundfish

resources between 1977 and 1995. Appendix F in: Pacific

Fishery Management Council. 1996. Appendix Volume II:

Status of the Pacific Coast Groundfish Fishery Through 1996

and Recommended Biological Catches for 1997: Stock

Assessment and Fishery Evaluation. (Document prepared for

the Council and its advisory entities.) Available from

Pacific Fishery Management Council, 2130 SW Fifth Avenue.

Suite 224, Portland, Oregon 97201.

Zimmermann, M., M. E. Wilkins, R. R. Lauth, and K. L. Weinberg.

1994. The 1992 Pacific west coast bottom trawl survey of

groundfish resources: Estimates of distribution, abundance,

and length composition. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-AFSC-42, 110 p.
29

Table 1. --Attributes of the vessels and net used during the 1995

triennial West Coast groundfish survey.
Table 2.--Sampling stratum boundaries used for analyses, stratum areas (km*), and realized

sampling density (hauls/l,000 km2) based on successful tows during the 1995

triennial West Coast groundfish survey. Strata have been grouped according to

International North Pacific Fisheries Commission (INPFC) areas. Differences in

totals are due to rounding.

3 2

Table 3. --Frequency of occurrence, depth and latitude ranges for

fish species caught during the 1995 triennial West

Coast groundfish survey.

3 4

Table 3. --Continued.
35

Table 3. --Continued.
Table 4. --Number of length frequency measurements collected by International North Pacific

Fisheries Commission area and depth stratum (m) during the 1995 West Coast

triennial groundfish bottom trawl survey.
Table 4. --Continued.

39

Table 5. --Number of biological data samples collected during the

1995 triennial West Coast bottom trawl groundfish

survey.

*Dorsal finrays were collected from lingcod. Otoliths were

collected from all other species.
Table 6. --Mean catch per unit of effort (CPUE, kg/ha) for the 20 most abundant groundfish

species in each International North Pacific Fisheries Commission area and depth

stratum during the 1995 West Coast triennial groundfish survey.
Table 6. --Continued.
Table 6. --Continued.
Table 6. --Continued.
Table 6. --Continued.
Table 6. --Continued.



Table 7. --Estimates of fish biomass from the 1995 West Coast triennial bottom trawl survey

by International North Pacific Fisheries Commission (INPFC) area for all depth

strata combined (55-500 m). Precision of the estimates are presented as

coefficients of variation (CV%). "T" denotes trace value. Differences in totals

result from rounding.

Table 8. --Estimates of fish biomass from the 1995 West Coast triennial bottom trawl survey

by International North Pacific Fisheries Commission (INPFC) area for the

shallowest depth stratum (55-183 m). Precision of the estimates are presented as

coefficients of variation (CV%). "T" denotes trace value. Differences in totals

result from rounding.

Table 9. --Estimates of fish biomass from the 1995 West Coast triennial bottom trawl survey

by International North Pacific Fisheries Commission (INPFC) area for the middle

depth stratum (184-366 m). Precision of the estimates are presented as

coefficients of variation (CV%). "T" denotes trace value. Differences in totals

result from rounding.

Table 10. --Estimates of- fish biomass from the 1995 West Coast triennial bottom trawl survey

by International North Pacific Fisheries Commission (INPFC) area for the deepest

depth stratum (367-500 m). Precision of the estimates are presented as

coefficients of variation (CV%). "T" denotes trace value. Differences in totals

result from rounding.

Table 11. --Estimates of fish population numbers (x 1,000) from the 1995 West Coast triennial

bottom trawl survey by International North Pacific Fisheries Commission (INPFC)

area for all depth strata combined (55-500 m). Precision of the estimates are

presented as coefficients of variation (CV%). "T" denotes trace value.

Differences in totals result from rounding.
Table 11. --Continued.
Table 12.--Estimates of fish population numbers (x 1,000) from the 1995 West Coast triennial

bottom trawl survey by International North Pacific Fisheries Commission (INPFC)

area for the shallowest depth stratum (55-183 m). Precision of the estimates are

presented as coefficients of variation (CV%). "T" denotes trace value.

Differences in totals result from rounding.

Table 13.--Estimates of fish population numbers (x 1,000) from the 1995 West Coast triennial

bottom trawl survey by International North Pacific Fisheries Commission (INPFC)

area for the middle depth stratum (184-366 m). Precision of the estimates are

presented as coefficients of variation (CV%). "T" denotes trace value.

Differences in totals result from rounding.

Table 14. --Estimates of fish population numbers (x 1,000) from the 1995 West Coast triennial

bottom trawl survey by International North Pacific Fisheries Commission (INPFC)

area for the deepest depth stratum (367-500 m). Precision of the estimates are

presented as coefficients of variation (CV%). "T" denotes trace value.

Differences in totals result from rounding.

65

Table 15. --The length-weight relationships from the 1995

triennial West Coast survey using a non-linear

least squares fit for the following equation:

Fish weight (grams) = a * {Fork length (cm)}b


Figure 1 .--The standardized poly-Nor’Eastern trawl and accessories used to sample groundfish

during the 1995 West Coast triennial bottom trawl survey.
Figure 2.--The 1995 West Coast triennial bottom trawl survey area and stratification scheme

(stratum numbers shown), also showing International North Pacific Fisheries

Commission statistical areas.
Figure 3.--Locations of stations successfully sampled in each depth stratum during the 1995 West

Coast triennial bottom trawl survey.
Figure 4. --Sea surface temperatures, averaged by one-half degree latitude, observed

during the 1977-95 West Coast triennial bottom trawl surveys.
Figure 5. --Bottom temperatures, averaged by one-half degree latitude, observed during

the 1980-95 West Coast triennial bottom trawl surveys.
Figure 6.--Arrowtooth flounder distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 7.--Aurora rockfish distribution and relative abundance measured in catch rates (kg/ha) from

the 1995 West Coast triennial bottom trawl survey.
Figure 8.--Bocaccio distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 9.--Canary rockfish distribution and relative abundance measured in catch rates (kg/ha) from

the 1995 West Coast triennial bottom trawl survey.
Figure l0.--Chilipepper distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 11 .--Darkblotched rockfish distribution and relative abundance measured in catch rates

(kg/ha) from the 1995 West Coast triennial bottom trawl survey.
Figure 12.--Dover sole distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 13.--English sole distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 14.--Greenstriped rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 15 .--Lingcod distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 16.--Longspine thornyhead distribution and relative abundance measured in catch rates

(kg/ha) from the 1995 West Coast triennial bottom trawl survey.
Figure 17.--Pacific hake distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 18.--Pacific halibut distribution and relative abundance measured in catch rates (kg/ha) from

the 1995 West Coast triennial bottom trawl survey.
Figure l9.--Pacific ocean perch distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 20.--Pacific sanddab distribution and relative abundance measured in catch rates (kg/ha) from

the 1995 West Coast triennial bottom trawl survey.

Figure 22.--Redstripe rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 23 .--Rex sole distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 24.--Rougheye rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 25.--Sablefish distribution and relative abundance measured in catch rates (kg/ha) from the

1995 West Coast triennial bottom trawl survey.
Figure 26.--Sharpchin rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 27.--Shortbelly rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 28.--Shortspine thornyhead distribution and relative abundance measured in catch rates

(kg/ha) from the 1995 West Coast triennial bottom trawl survey.
Figure 29.--Silvergray rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 30.--Spiny dogfish distribution and relative abundance measured in catch rates (kg/ha) from

the 1995 West Coast triennial bottom trawl survey.
Figure 31 .--Splitnose rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 32.--Stripetail rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 33 .--Widow rockfish distribution and relative abundance measured in catch rates (kg/ha) from

the 1995 West Coast triennial bottom trawl survey.
Figure 34.--Yellowtail rockfish distribution and relative abundance measured in catch rates (kg/ha)

from the 1995 West Coast triennial bottom trawl survey.
Figure 35.-- Estimated population size composition and mean lengths of arrowtooth flounder by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 36.-- Estimated population size composition and mean lengths of aurora rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 37.-- Estimated population size composition and mean lengths of bocaccio by sex and International

North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995 triennial

bottom trawl survey.

Figure 39.-- Estimated population size composition and mean lengths of chilipepper by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.

Figure 41.-- Estimated population size composition and mean lengths of Dover sole by sex and International

North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995 triennial

bottom trawl survey.
Figure 42.-- Estimated population size composition and mean lengths of English sole by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 43.-- Estimated population size composition and mean lengths of greenstriped rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 44.-- Estimated population size composition and mean lengths of lingcod by sex and International

North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995 triennial

bottom trawl survey.
Figure 45.-- Estimated population size composition and mean lengths of longspine thornyhead by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 46.-- Estimated population size composition and mean lengths of Pacific hake by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 47.-- Estimated population size composition and mean lengths of Pacific hake by sex and

International North Pacific Fisheries Commission area for the shallow depth stratum

(55-183 m) from the 1995 triennial bottom trawl survey.
Figure 48.-- Estimated population size composition and mean lengths of Pacific hake by sex and

International North Pacific Fisheries Commission area for the middle depth stratum

(184-366 m) from the 1995 triennial bottom trawl survey.
Figure 49.-- Estimated population size composition and mean lengths of Pacific hake by sex and International

North Pacific Fisheries Commission area for the deep depth stratum (367-500 m) from the 1995

triennial bottom trawl survey.
Figure 50.-- Estimated population size composition and mean length of Pacific halibut by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 51.-- Estimated population size composition of Pacific ocean perch by sex and International North

Pacific Fisheries Commission area for all depths (55-500 m) from the 1995 triennial bottom

trawl survey.
Figure 52.-- Estimated population size composition and mean lengths of Pacific sanddab by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.

Figure 54.-- Estimated population size composition and mean lengths of redstripe rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 55.-- Estimated population size composition and mean lengths of rex sole by sex and International

North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995 triennial

bottom trawl survey.

Figure 57.-- Estimated population size composition and mean lengths of sablefish by sex and International

North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995 triennial

bottom trawl survey.

Figure 59.-- Estimated population size composition and mean lengths of sablefish by sex and International

North Pacific Fisheries Commission area for the middle depth stratum (184-366 m) from the 1995

triennial bottom trawl survey.
Figure 60.-- Estimated population size composition and mean lengths of sablefish by sex and International

North Pacific Fisheries Commission area for the deep depth stratum (367-500 m) from the 1995

triennial bottom trawl survey.
Figure 61.-- Estimated population size composition and mean lengths of Pacific sanddab by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 62.-- Estimated population size composition and mean lengths of shortbelly rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 63.-- Estimated population size composition and mean lengths of shortspine thornyhead by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 64-- Estimated population size composition and mean lengths of silvergray rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 65.-- Estimated population size composition and mean lengths of splitnose rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 66.-- Estimated population size composition and mean lengths of stripetail rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 67.-- Estimated population size composition and mean lengths of widow rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 68.-- Estimated population size composition and mean lengths of yellowtail rockfish by sex and

International North Pacific Fisheries Commission area for all depths (55-500 m) from the 1995

triennial bottom trawl survey.
Figure 69.- The age composition of the Pacific hake resource off

California, Oregon, Washington, and British Columbia in 1995,

based upon results of the National Marine Fisheries Service's

triennial bottom trawl survey of groundfish resources.

Figure 70.- The age composition of the lingcod resource off California,

Oregon, Washington, and British Columbia in 1995, based upon

results of the National Marine Fisheries Service's triennial

bottom trawl survey of groundfish resources.
Oregon, Washington, and British Columbia in 1995, based upon

results of the National Marine Fisheries Service's triennial

bottom trawl survey of groundfish resources.

Figure 72.- The age composition of the chilipepper resource off

California, Oregon, Washington, and British Columbia in 1995,

based upon results of the National Marine Fisheries Service's

triennial bottom trawl survey of groundfish resources.
Figure 73.- The age composition of the darkblotched rockfish resource off

California, Oregon, Washington, and British Columbia in 1995,

based upon results of the National Marine Fisheries Service's

triennial bottom trawl survey of groundfish resources.

Figure 74.- The age composition of the yellowtail rockfish resource off

California, Oregon, Washington, and British Columbia in 1995,

based upon results of the National Marine Fisheries Service's

triennial bottom trawl survey of groundfish resources.
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.

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FRITZ, L. W., A. GREIG, and R. F. REUTER. 1998. Catch-per-unit-effort, length, and depth distributions

of major groundfish and bycatch species in the Bering Sea, Aleutian Islands, and Gulf of Alaska regions

based on groundfish fishery observer data, 179 p. NTIS number pending.

SINCLAIR, E. H. (editor) 1997. Fur seal investigations, 1996, 115 p. NTIS number pending.

SINCLAIR, E.H. (editor). 1997. Fur seal investigations, 1995, 188 p. NTIS number pending.

KINOSHlTA, R. K., A. GREIG, and J. M. TERRY. 1998. Economic status of the groundfish fisheries off

Alaska, 1996, 91 p. NTIS No. PB98-126170.

LAAKE, J., D. RUGH, and L. BARAFF. 1998. Observations of harbor porpoise in the vicinity of acoustic

alarms on a set gill net, 40 p. NTIS No. PB98-117641.

RUTECKI, T. L., M. F. SIGLER, and H. H. ZENGER JR. 1997. Data report: National Marine Fisheries

Service longline surveys, 1991-96, 64 p. NTIS No. PB98-108822.

MARTIN, M. H. 1997. Data report: 1996 Gulf of Alaska bottom trawl survey, 235 p. NTIS No. PB98-

103930.

LAUTH, R. R. 1997. The 1996 Pacific West Coast upper continental slope trawl survey of groundfish

resources off Washington and Oregon: Estimates of distribution, abundance, and length composition,

156 p. NTIS No. PB97-208912.

LAUTH, R. R. 1997. The 1995 Pacific West Coast upper continental slope trawl survey of groundfish

resources off southern Oregon and northern Caiifornia: Estimates of distribution, abundance, and length

composition, 110 p. NTIS No. PB97-208920.

LAUTH, R. R., M. E. WILKINS, and P. A. RAYMORE JR. 1997. Results of trawl surveys of groundfish

resources of the West Coast upper continental slope from 1989 to 1993, 342 p. NTIS No. PB97-208904.

HILL, P. S., D. P. DEMASTER, and R. J. SMALL. 1997. Alaska marine mammal stock assessments,

1996, 150 p. NTIS No. PB97-203277.

CHUMBLEY, K., J. SEASE, M. STRICK, and R. TOWELL. 1997. Field studies of Steller sea lions

(Eumetopias jubatus) at Marmot Island, Alaska, 1979 through 1994, 99 p. NTIS No. PB97-203376.

OSMEK, S., J. CALAMBOKIDIS, J. LAAKE, P. GEARIN, R. DELONG, J. SCORDINO, S. JEFFRIES, and

R. BROWN. 1997. Assessment of the status of harbor porpoise (Phocoena phocoena) in Oregon and

Washington waters, 46 p. NTIS No. PB97-198436.

WING, B. L., C. W. DERRAH, and V. M. O’CONNELL. 1997. Ichthyoplankton in the eastern Gulf of

Alaska, May 1990,42 p. NTIS No. PB97-174379.

WILSON, C. D., and M. A. GUTTORMSEN. 1997. Echo integration-trawl survey of Pacific whiting,

Merluccius productus, off the west coasts of the United States and Canada during July-September 1995,

70 p. NTIS No. PB97-174387.

CELEWYCZ, A. G., and A. C. WERTHEIMER. 1997. Suitability of Dry Bay, southeastern Alaska, as

rearing habitat for juvenile salmon, 19 p. NTIS No. PB97-161343.