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NOM Technical Memorandum NMFS-AFSC­

$l'.qTE 5 Of P'" 

The 1997 Pacific West Coast


Upper Continental Slope Trawl Survey of


Groundfish Resources off Washington


Oregon, and California: Estimates of 

Distribution, Abundance, and 

Length Composition 

R. R. Lauth 

s. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration 

National Marine Fisheries Service 

Alaska Fisheries Science Center 

February 1999

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: 

Lauth, R. R. 1999. The 1997 Pacific West Coast upper continental 

slope trawl survey of groundfish resources off Washington, Oregon 

and California: Estimates of distribution, abundance, and length 

composition. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC98, 284 p. 

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

the National Marine Fisheries Service, NOAA. 
.., . () q:.

~Q ATMOS~~


i9/('

I . . 'C( (I). -z. NOAA Technical Memorandum NMFS-AFSCI91"MENT Of cO 

The 1997 Pacific West Coast


Upper Continental Slope Trawl Survey of


Groundfish Resources off Washington


Oregon, and California: Estimates of 

Distribution , Abundance, and 

Length Composition 

R. R. Lauth 

Alaska Fisheries Science Center 

Resource Assessment and Conservation Engineering Division


7600 Sand Point Way N. , BIN C- 15700


Seattle, WA 98115-0070


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 

February 1999 
This document is available to the public through: 

National Technical Information Service 

S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

www. ntis.gov 
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iii 

ABSTRACT 

The Alaska Fisheries Science Center I s Resource Assessment 

and Conservation Engineering Division (RACE) conducted a 

groundf ish bottom trawl survey of the West Coast upper 

continental slope (WCUCS) in 1997. The survey area stretched 

from the U. -Canada border (near Nitinat Canyon) to 34O50lN lat. 

(near Pt. Arguello) in waters from 183 to 1, 280 m deep. This was 

the tenth survey in an ongoing series to monitor long-term trends 

in the distribution and abundance of WCUCS groundfish 

populations. The spatial coverage of the WCUCS groundfish trawl 

survey was expanded in 1997 to include all of the International 

North Pacific Fisheries Commission statistical areas between 

Point Conception (34030 IN lat. ) and the U. S. /Canada border. 

Sampling density was reduced to one-third the density of previous 

surveys so that the expanded area could be surveyed wi thin a 5-

week period. Sampling was conducted aboard the NOAA ship Miller 

Freeman. We successfully sampled 182 of the 200 stations that we 

had previously established. Catches included 149 different 

species of fishes from 55 fish families. Two-hundred and twelve 

different invertebrates representing 10 phyla and 18 classes were 

caught but only 125 of these invertebrates were identified to the 

species level. with all depth strata combined and when all INPFC 

areas and depths were combined , Pacific whiting (Merluccius 

productus) and spiny dogfish (Squalus acanthias) had the highest 

catch rates in the U. S. -Vancouver , Columbia, and Eureka INPFC 

areas. In the Monterey and Conception INPFC areas , Dover sole 

(Microstomus pacificus), longspine thornyhead (Sebastoblobus 
altivelis), Pacific whiting, and sablefish (Anoplopoma fimbria)


had the highest catch rates when all depths were combined. The 

biomass estimates for the Dover sole , sablef ish , longspine


thornyhead , and shortspine thornyhead (Sebastolobus alascanus) 

varied by stratum and INPFC area. The total biomass estimates for 

all INPFC areas and strata combined were 109 858 t , 71, 019 t, 

101, 636 t , and 26 393 t for Dover sole , sablefish , longspine 

thornyhead , and shortspine thornyhead, respectively 

The survey des ign and the methods used are described , the 

data collected are summarized , and the results of analyses of 

distribution , abundance , and biological parameters are presented. 

Data on water temperature , patch composition , relative abundance 

and geographic distribution are reported. Estimates of biomass 

population abundance , and length composition are also presented. 

Appendices include position and catch listings for each haul, 

catch rates of fish and invertebrates , and population size 

compositions. 
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......................................... ...................................... ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .............................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

CONTENTS


. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

INTRODUCTION . . . . 1


SURVEY METHODS 

Survey Period and Sampling Area 

Vessels and Sampling Gear 

Trawl station Allocation


Trawl ing Procedures 

Catch Sampling Procedures and Biological Data Collection .. 8


Oceanographic Data Collection


Data Analysis


RESULTS . . . . . . . . . o 

Haul , Catch, and Biological Data ......................... 

Temperature Data 

Relative Density and Distribution of Species ............. 14


Biomass and Population Estimates ......................... 15


Size and Age Composition ................................. 17


Length-Weight Relationships .............................. 18


Requests for Other Data Analyses ......................... 18


ACICNOWLEDGMENTS . . 

TABLES . . . . . . . . . . . . . . . . . . . . . 21


FIGURES 

CITATIONS 157


APPENDIX A . . . . . . 
 161 Haul and Catch Information .............................. 161


APPENDIX B . . . . . . . . . . . 
 183 

Relative Abundance 183


INTRODUCTION 

Fishery- independent data obtained from the Alaska Fisheries 

science Center (AFSC) West Coast upper continental slope 

(WCUCS) groundf ish trawl surveys are used by fishery managers to 

assess stock conditions and to establish annual harvest 

guidelines for the commercially valuable fish species inhabiting 

the WCUCS. These species , referred to as the deepwater complex 

(DWC), include sablefish (Anoplopoma fimbria), shortspine 

thornyhead (Sebastolobus alascanus), longspine thornyhead (S. 

al tivelis), and Dover sole (Microstomus pacificus) The Resource 

Assessment and Conservation Engineering (RACE) Division of the 

AFSC conducted its first groundf ish assessment survey of the 

WCUCS in 1984 and has done so annually since 1988. The WCUCS 

covers habi ta t 183 -1 , 280 m deep from the U. S. -Canada border to 

30lN lat. and is divided into five International North Pacific 

Fisheries Commission (INPFC) statistical areas including the 

U. S. -VancoQver , Columbia , Eureka , Monterey, and Conception areas 

(Fig. 1) 

The spatial coverage of annual slope surveys has varied. 

Prior to 1997 , WcUCS groundfish bottom trawl surveys were limited 

in their spatial coverage of INPFc areas because of limited 

vessel time and other logistic considerations. The 1996 survey 

was the most extensive and covered the U. S. -Vancouver and 

Columbia INPFC areas (Lauth 1997a) The U. S. -Vancouver INPFC 

area was surveyed once before in 1993 in addition to the northern 

portion of the Columbia INPFC area (Lauth et ale 1997) Central 
and/or southern sections of the Columbia INPFC area (450301 to


43000 IN lat. ) were also surveyed in 1984, 1988 , 1989 , and 1992


(Raymore et ale 1990 , Parks 'et ale 1993, Lauth et ale 1997). The 

Eureka INPFC area was surveyed in 1990 (Lauth et ale 1997) and 

again in 1995 (Lauth 1997b), and the northern section of the 

Monterey INPFC area (38020 I to 400 30 IN lat. ) was surveyed in 1991


(Lauth et ale 1997) The Southwest Fisheries Science Center


(SWFSC) conducted two other groundf ish bottom trawl surveys in


1987 and 1988 which covered parts of the Conception and Monterey


INPFC areas between 34030 I and 36030 I N lat. (Butler et ale 

1989) . 

During the 1993 AFSC survey, concerns were raised about the


poor performance of the slope survey trawl and, consequently, the


validity of slope survey data. These concerns prompted an 

external review of the slope survey by a panel of fishery 

scientists in July 1995. The panel criticized the lack of 

synoptici ty in survey coverage and the performance of survey gear 

(Parma et ale 1995) Survey gear performance was investigated 

during an experimental gear cruise aboard the NOAA ship Miller 

Freeman in 1994. During that cruise , we experimented with ways 

to stabilize the sampling trawl , learned more about how to 

evaluate trawl performance , and investigated al ternati ve methods 

of surveying groundfish resources using a video camera sled. 

Regular survey work resumed in 1995 after several changes were 

made to the sampling trawl and to towing protocol. The changes 
stabilized the slope trawl and resulted in more consistent trawl 

performance (Lauth et al. , 1998) 

The spatial coverage of WCUCS groundf ish trawl surveys was 

expanded in 1997 to include all of the INPFC areas between Point 

Conception (N. 340301 lat. ) and the U. -Canada border. Sampling 

density was reduced compared to previous surveys so that the 

expanded area could be surveyed within a 5-week period. 

The obj ecti ve of this report is to document the survey 

design and field procedures , summarize the survey data , and 

present the results of the standard RACE analyses for the 1997 

WCUCS survey for each of the INPFC statistical areas. Included 

are summaries of catches , distribution, abundance , and size 

composition for major components of the community, as well as 

analyses of age-length and length-weight relationships of 

selected species. 
SURVEY METHODS


Survey Period and Samplinq Area


The u. S. -Vancouver , Columbia, Eureka , Monterey, and 

Conception INPFC statistical areas (U. S. -Canada border to 34030 IN 

lat. ) were surveyed between 20 October and 25 November. Survey 

sampling began near Cape Arguello (34050 IN lat. ) and progressed 

northward to Nitinat Canyon (4S0 051N lat. , Fig. 1). Water depth 

at survey stations ranged between 183 and 1, 280 m (100-700 fm). 

Vessels and Samplinq Gear


The NOAA Ship Miller Freeman is a 65. 5 m stern trawler


powered by a 2 300 continuous horsepower engine. The ship is 

equipped with dual net reels , a Rapp-Hydema warp tensioning 

system , Wesmar Fish Eye net sonar system , Furuno netsonde , EQ-50 

depth sounder , and Global Positioning System (GPS) navigational 

aids. A high-opening Nor eastern trawl (Fig. 2) constructed of 

polyethylene mesh and equipped with mudsweep roller gear (Fig. 

was used to collect all samples. This trawl , built and rigged to 

RACE Division gear standards , has a 27. 2 m headrope and a 37. 4 m 

f ootrope . The body is constructed of 127 mm stretched-mesh 

polyethylene netting, 89 mm stretched-mesh web in the codend , and 

a 32 mm stretched -mesh codend liner. Three 55 m dandylines made 

of 16 mm galvanized steel cable lead from each wing to a pair of 
8 x 2. 7 m steel V-doors weighing 1, 000 kg each. Each door has 

a 4-point bridle on its backside made with 13-rom long-link chain 

having 33 links forward and 22 links aft in both the top and 

bottom. Instruments attached to the trawl gear to monitor gear 

performance included the SCANMAR equipment for measuring net 

dimensions , a Furuno wireless netsonde for real-time monitoring 

of the headrope height , and one bottom contact sensor on the 

f ootrope . A Wesmar net sonar was attached to the net headrope 

and used to assure that the trawl gear was performing to 

engineering specif ications during the wire marking procedure and 

during the initial gear calibration. A Richard Brancker XL-200 

submersible data logger was attached to the trawl and used in 

conjunction with a Trimble Global Positioning System (GPS) unit 

to record data on the tj~~, depth, water temperature , and 

geodetic position during each trawl. These data were combined 

with fishing dimensions of the net , producing a comprehensive set 

of haul data describing gear performance in space and time. 

Trawl station Allocation


There were 200 stations along 31 east-west tracklines spaced 

50 km apart between the U. S. -Canada border and 34 50 IN lat. near 

Cape Arguello. stations south of Bodega Head (38 20 IN lat. ) were


new and othose to the north were a subset of the stations already 

sampled during previous WCUCS surveys (Lauth 1997a and Lauth 

1997b , Lauth et ale 1997 , Parks et ale 1993) A combined 
systematic and random design was used for selecting the survey 

bottom trawl stations. Sampling was conducted between 183 and 

280 m in six strata of 183 m (100 fm) depth intervals (183-

365 m , 366-547 m , 548-730 m, 731-913 m, 914-1 095 m , and 1, 096-

280 m). The number of sampling stations within each depth 

stratum were allocated proportional to the trackline length 

across each depth interval at the rate of one station per 13. 0 

of linear trackline length (e.g. a stratum with a trackline 

length of 30 km would be allocated stations). Tracklines were 

50 km apart and positioned roughly perpend i cu I ar to the 

coastline. To assure even depth coverage within a stratum , the 

depth range of each stratum was divided into a number of bins 

equal to the number of stations scheduled to be surveyed that 

year. Nominally, a bin was identified by its midpoint target 

depth. stations were then randomly assigned to tracklines by 

picking target depths without replacement. 

Trawling Procedures


Sampling was done on a 24-hour basis. stations were located 

by GPS and echosounder and then surveyed prior to towing. If the 

terrain was determined to be too rough or too steep to allow the 

successful completion of a tow , we searched for an alternate site 

with a similar target depth within a 10 km radius of the 

original. If no favorable ground was located the station was 

declared untrawlable and abandoned. I f the gear was damaged 
during the tow severely enough to affect catch composition , or if 

the gear performance was in any way judged to be unacceptable 

(e.g. , mud , large trap entangled in the net) , the haul was 

considered unsatisfactory and the station was either repeated or 

abandoned. Unsuccessful tows were not used in the analyses. 

Scientists , off icers , and deck crew worked together to 

standardize fishing procedures. A scientist familiar with 

trawling was always present in the trawl house during fishing 

operations to monitor adherence to standardized protocols. Also, 

AFSC gear experts participated in the cruise to ensure that the 

trawl gear and associated rigging were properly maintained. The 

scope ratio varied with depth and ranged from 2. 5: 1 at shallower 

depths to 1. 6: 1 at the deepest depths (Table 1) Vessel speed 

while the trawl was being set was between 5. 5 and 6. 5 km/hr. 

Vessel speed gradually decreased to 4. 3 km/hr (2. 3 knots) at 

brakeset and this speed was maintained as closely as possible


throughout each haul. The target duration of a trawl sample was 

30 minutes. A haul began when the ground-gear first touched 

bottom and ended when it lost contact with the bottom. The 

Furuno net sounder was used to monitor ground-gear contact during 

a haul , but actual bottom time was determined from the bottom 

contact sensor data upon completion of the tow. Posi tion data 

were collected at 2-sec intervals for each haul using a Global


Positioning System (GPS) receiver. The position data were used 

to monitor ground speed , track the trawl I s path , and estimate 

distance fished. Average vessel speed over ground and distance-
fished were calculated from the position data and the trawl I s 

actual bottom time. 

Catch sampling Procedures and Biological Data Collection


standard RACE catch sampling procedures were followed as 

described by smith and Bakkala (1982). Catches less than 

1 metric ton (t) were dumped directly onto a sorting table for 

processing. Catches larger than 1 t were weighed by an 

electronic load cell and then dumped onto the deck, into the fish 

bin, onto the sorting table , or any combination of the three. 

all cases , the entire catch was processed. Large catches were 

made more manageable for processing by weighing and measuring a 

random subsample of the dominant f ish species (e. g., Pacif 

whiting or spiny dogf ish) and discarding the remainder of that 

species overboard. The non-subsample catch weight for that 

species was the difference between the sum of the subsample 

weight for that species and the catch weights for all other 

species and the total catch weight measured by the electronic 

load cell. Fishes and invertebrates were identified to species 

as time and expertise permitted. After the catches were sorted 

by species , weighed , and enumerated , biological data and 

specimens were collected. Samples of all fish species were 

measured to characterize their size composition. Sex 

determination and fork length measurements were done for up to 

200 specimens of each of the primary target species , rockfishes 
and flatfishes from each haul. The same was done for grenadiers 

except they were measured from the tip of their snout to the 

insertion of the anal f in ray. other non-target species were 

measured as unsexed and all skates and rays were measured from


wingtip-to-wingtip. otoliths were collected for age


determination from arrowtooth flounder (Atheresthes stomias),


darkblotched rockfish (8ebastes crameri), Dover sole, Pacific


grenadier (Coryphaenoides acrolepis), sablefish, shortspine 

thornyhead , splitnose rockfish (8. diploproa), and longspine 

thornyhead. otoli th collections were depth- , area- , and sizestratified so that sampling effort was more evenly spread over 

the entire survey area. There were three depth zones (183-549 m 

550-914 m , and 915-1 280 m) and three geographical areas. 

Geographical areas were separated into southern (to 38050 IN


lat. ), central (to 43020 IN lat. ), and northern areas (to U. s. 

Canada border) otoliths were collected from size-stratified 

samples of 5 f ish per sex/ centimeter interval in each depth zone 

and geographical area. 

Additional biological collections were made at the request 

of other scientists from a number of laboratories , agencies , and 

universities interested in West Coast fishery resources. These 

collections were taken for studies involving age and growth 

genetics , and other fish. life history parameters. 
oceanographic Data collect~on 

Sea surface temperatures were taken at all stations using a


bucket thermometer. Bottom temperatures were measured using a 

Richard Brancker XL-200 data logger mounted to the trawl 

headrope. Additional information on temperature profiles from 

this cruises is available on request from the author. 

Data Analysis


Several analyses are performed routinely on RACE 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 used the area -swept method as described by Gunderson and 

Sample (1980) to estimate population biomass and numbers. 

Briefly, this method entails standardizing samples from each 

station into catch per unit of effort (CPUE) in terms of either 

kilograms or numbers per hectare (kg /ha , no. /ha) and calculating 

the arithmetic mean for each sampling stratum. Length - frequency 

data were weighted by CPUE (no. /ha) and expanded to the total 

estimated population abundance to estimate the population size 
p. 

composition for each species. Sablef ish age data were available 

for this report so size composition estimates were applied to 

age-length keys to obtain estimated age compositions. Sablef ish 

age-length keys were made by combining ages from all depths 

areas , and sexes to increase the sample size. since sablefish 

lengths at age were different between the sexes, and were more 

variable at greater depths , further analyses was done using three 

depth-specific (the same depth zones listed on 9) and sexspecif ic age-length keys. 
RESULTS€

Haul, catch, and Biological Data 

One-hundred-ninety tows were attempted during the survey. 

Out of 200 possible stations , 182 stations were sampled 

successfully (Fig. 1). Eighteen of the possible 200 stations 

were abandoned because the bottom was too rough or too steep. 

The remainder of the attempted tows were unsuccessful due to 

trawl hang-ups , net rips , bad bottom , excessive mud in the tows, 

crossing into an adjacent depth stratum , or gear deployment 

problems. SCANMAR net mensuration data were obtained from 142 

tows , submersible bathythermograph data from 186 tows , bottom 

contact sensor data from 188 tows , and GPS course and position 

data from 190 tows. Sampling densities ranged from 

2 . 0 hauls /1, 000 km2 in the U. S . -Vancouver INPFC area to 

1 hauls/1, 000 km2 in the Monterey INPFC area (Table 2). 

Mean net widths were calculated for each trawl haul. The 

relationship was linear between mean net width and gear depth 

and mean net width and wire length (Fig. 4). An overall mean 

path width of 16. 81 m was calculated for the entire survey using 

142 of the 182 tows with good performance. The range of mean net 

widths for these 142 tows was 13. 14 m to 19. 01 m and the standard 

deviation was O. 85 The overall mean path width was used in 

area-swept calculations for hauls where actual width measurements 

were unavailable. 

Table 3 summarizes the biological data collected from fish 
species. Specimen ages from collected otoliths were determined 

by researchers from the Pacific states Marine Fisheries 

commission and Oregon Department of Fish and wildlife. Results 

from collected data and specimens for several special studies 

requested by colleagues in other agencies or institutions will be 

reported elsewhere. 

A total of 149 fish species representing 55 fish families 

were identif ied over the course of the survey. Table 4 lists the 

frequencies of occurrence , depth range , and the latitudinal range 

for all fishes identified in trawl samples. Similarly, Table 5


shows ranges and frequencies of occurrence for invertebrates


representing 10 phyla and 18 classes. Of the 212 invertebrates 

listed , 125 were identif ied to species. Appendix A presents 

detailed station information for each haul and catch weights of 

the major fish and invertebrate species caught in each haul. The 

number of individual fish length observations of each fish


species are reported in Tables 6 to 11 by depth stratum and INPFC


area. 

Tempera ture Data 

Sea surface temperatures ranged from 11. 70 to 18. gOC and 

bottom temperatures ranged from 3. 10 to 10. 3OC (Fig. 5). Mean 

sea surface temperature was 14. 7OC and mean bottom temperature 

was 5. Sea surface temperatures generally decreased and were 

more variable with increasing latitude. 
Bottom temperatures generally decreased with increasing depth 

wi thin the survey area. 

Relative Density and Distribution of Species


The 20 most abundant groundf ish and selected crab species 

are presented with all depth strata combined by INPFC area (Table 

12), with all INPFC areas combined by depth stratum (Table 13), 

and by INPFC area and depth stratum (Tables 14-18). Pacif ic 

whiting (Merluccius productus) and spiny dogfish (Squalus 

acanthias) had the' highest catch rates in the U. s. -Vancouver 

Columbia, and Eureka INPFC areas with all depth strata combined 

and when all INPFC areas and depths were combined (Table 12). 

the Monterey and Conception INPFC areas , Dover sole , longspine 

thornyhead , Pacific whiting, and sablefish had the highest catch 

rates when all depths were combined (Table 12). wi th all INPFC 

areas combined by depth stratum , Pacific whiting and spiny 

dogfish had the highest catch rates in the shallowest two strata 

(Table 13) The fishes with the highest catch rates in 

successively deeper strata were Dover sole , sablef ish , longspine 

thornyhead , and Pacif ic grenadier , respectively. 

Catch rates by depth stratum varied among the INPFC areas 

(Tables 14-18). In general , Pacif ic whiting were the dominant 

species in shallower strata in the U. s. -Vancouver , Columbia , and 

Eureka INPFC areas , and stripetail rockfish 
 (Sebastes saxicola), 

Pacific whiting, or Dover sole had the highest CPUE in the same 

two strata in the Monterey and Conception INPFC areas. For the 
deeper strata , the CPUE of longspine thornyhead was among the


highest catch rate for all INPFC areas , and either Pacific or


giant grenadier (Albatrossia pectoralis) 
 had among the top three


or four CPUEs in the deepest stratum. 

Complete listings of the relative abundance of all fish and


invertebrate species ranked by mean CPUE , depth stratum , and


INPFC area are presented in Appendix 


Maps of the geographical distribution and relative catch


rates of selected important groundfish species and true Tanner


crab (Chionoecetes tanneri) are presented in Figures 6-19 in 

alphabetical order. These maps show the locations of hauls where 

these species were caught. Catch rates were categorized as: 

greater than zero and less than or equal to the mean CPUEi 2) 

greater than the mean CPUE and less than or equal to one standard 

deviation from the meani 3) between one and two standard 

deviations greater than the mean CPUEi and 4) over two standard 

deviations greater than the mean CPUE. 

Biomass and Population Estimates


Abundance estimates of biomass in metric tons (t) and 

associated coefficients of variation (CV) are presented for 

selected taxa by stratum and area in Tables 19 through 24. 

Similarly, estimates of population numbers with associated CVs 

are presented for important species groups in Tables 25 through 

30. The total number of hauls and hauls with catch weight, catch 
number , and length data by stratum and area for the various taxa 

are represented in Tables 31 through 36. 

The biomass estimates for the DWC (see p. 1) varied by 

species , stratum , and INPFC area. The total biomass estimates 

for all INPFC areas and strata combined were 71, 019 t, 109, 858 

101, 636 t , and 26, 393 t for sablefish, Dover sole , longspine 

thornyhead, and shortspine thornyhead , respectively (Table 19). 

The stratum with the greatest estimated biomass for each DWC 

species was stratum 3 for sablefish (22%), stratum 2 for Dover 

sole (39%), stratum 4 for longspine thornyhead (35%), and stratum 

5 for shortspine thornyhead (23 %) . The INPFC area with the 

highest proportion of total estimated biomass for each DWC 

species was the Columbia area for sablefish (34%), and the 

Monterey area for Dover sole (35%), longspine thornyhead (30%), 

and shortspine thornyhead (29%). 

Readers should be aware that the biomass and population 

estimates presented here are not absolute estimates since herding 

by doors and bridles and escapement underneath the trawl' 

footrope , around the net's opening, and through the net' s meshes 

can affect the bottom trawl catches (Gunderson 1993). For lack 

of data on species-by-species catchabili ty, abundance 

calculations are based on the assumption that all fish in front 

of the trawl and between the wingtips are captured. The degree 

of bias introduced by this assumption probably varies among 

species. For instance , the ability of a fish to avoid the net 

will depend on the fish' s shape , size , speed , and its reaction to 

the part of the net encountered. Furthermore , the survey covers 
limited portions of the depth and geographic range of some of


these species. As mentioned previously, this survey targets many 

species and provides general information where it lacks in 

specific information. These surveys are the only f isheryindependent source of information on the abundance , distribution


and length and age-composition for many of these species. stock 

assessment scientists utilize our survey results , along with 

commercial catch data , in order to estimate acceptable biological 

catch levels. 

size and Age Composition


Estimated population length compositions for several


groundfish species are presented in Figures 20-73 by species and


by depth stratum. 

At the time this report was prepared , the only age data


available for analyses were those for sablef ish. Population 

estimates by age group and mean length at age are presented in


Tables 37-43 by INPFC area and all INPFC areas combined using an


age-length key for all depths , sexes , and areas combined.


Lengths at age were different between the sexes and were more


variable at greater depths for sablefish , so further analyses


were done using three depth-specific and sex-specific age-length 

keys. The depth strata used for the age-length keys were the 

same as the biological sampling strata except that sablefish from 

all INPFC areas were combined to increase the sample size. 

Results from these analyses are presented in Figures 68-73. 
Sablef ish age data and results of growth rate , population


age composition, and biomass-at-age analyses can be obtained upon 

request from the author in either printed or digital form. Age 

data and results from other species can be obtained as it becomes 

available. 

Length-Weight Relationships


From the in~i vidual f ish weight samples , we determined 

length-weight relationships for arrowtooth flounder , Dover sole, 

sablefish , shortspine thornyhead , longspine thornyhead , Pacific 

grenadier , and splitnose rockfish using a non-linear least 

squares regression model. Table 43 summarizes the length-weight 

relationships by sex and for all INPFC areas and sexes combined 

(including unsexed fish). 

Requests for Other Data Analyses


To avoid unnecessary detail and excessive printing costs 

appendices listing estimated length compositions for major 

species and abundance estimates for less commercially important 

species were not included in this report. However, if the reader 

requires these or other more detailed analyses , they can be 

obtained as either printed pages or as computer files upon 

request from Robert Lauth at (206) 526-4121 (phone) or 

bob. lauth~noaa.gov (email) 
ACKNOWL EDGMENT S 

I would like to thank all the cruise participants for their


hard work during the 1997 west Coast upper continental slope


groundfish survey. Participants included (in alphabetical order) 

Troy Buckley, Roger Clark, Bill Flerx , Robin Harrison , Allen


Harvison, Je~ry Hoff, Dan Kamikawa, steve Kupillas , Mike MacEwan


Michael Martin , Bob Mikus , Lisa Mooney, Heather Munro, Jay Orr, 

John Seaborn , Kate Shaw , Allen Shimada , Jim Smart , ICeith smith 

and Mark zimmermann. I would also like to express my 

appreciation to the off icers , the survey department , the 

electronics department , and the rest of the crew of the NOAA ship 

Miller Freeman for their valuable assistance during the 1997 West 

Coast continental slope groundfish trawl survey. Thanks 

especially to Commander John Clary who was motivated 

cooperati ve , conscientious , and obviously shared my sense of


urgency for completing the ambitious survey work , and to Bill


Floering who is always extremely helpful. Thanks also to Gary


Mundell for data editing and Bill Flerx, Ron Payne , Jerry


Hardman, Dave Roetcisoender , and Larry Haaga for gathering 

together all the equipment necessary for survey operations. 

Special thanks to Dave King and his net shed crew for all their 

help supplying and maintaining the trawl nets and accessories 

that we used for this survey. I am also grateful to Mark 

Wilkins , James Lee, and Gary Duker for carefully reviewing this 

manusc~ ipt 
21 

TABLES

To view tables, please download 

Tables from NOAA-TM-AFSC-98.pdf
75 

FIGURES

To view figures, please download 

Figures from NOAA-TM-AFSC-98.pdf
157


CITATIONS


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Eschmeyer , W. N ., E. S. Herald , and H. Hammann. 1983. field 

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Lauth , R. 1997a. The 1996 Pacific West Coast upper 

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APPENDIX A

To view Appendix A, please download 

Appendix A from NOAA-TM-AFSC-98.pdf
183 

 

APPENDIX B

To view Appendix B, please download 

Appendix B from NOAA-TM-AFSC-98.pdf
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. 

AFSCHill, P. S. , and D. P. DEMASTER. 1998. Alaska marine mammal stock assessments, 1998, 166 p. NTIS 

number pending. 

WING, B. L , M. M. MASUDA, C. M. GUTHRIE III , and J. H. HEllE 1998. Some size relationships and 

genetic variability of Atlantic salmon (Salmo salar) escapees captured in Alaska fisheries, 1990- , 32 p. 

NTIS No. PB99-118697. 

ORR, J. W. , M. A. BROWN , and D. C. BAKER. 1998. Guide to rockfishes (Scorpaenidae) of the genera 

Sebastes Sebastolobus, and Adelosebastes of the northeast Pacific Ocean , 46 p. NTIS No. PB99-

114217. 

THROWER , F. , R. MARTIN, and R. HEINTZ. 1998. Effect of seawater entry date on 24-hour plasma 

sodium concentration and survival of juvenile spring chinook salmon (Oncorhynchus tshawytscha) reared 

in marine net-pens, 18 p. NTIS No. PB98-173545. 

MURPHY, J. M., N. E MALONEY, and B. L WING. 1998. Distribution and abundance of zooplankton 

in the north Pacific Subarctic Frontal Zone and adjacent water masses, 31 p. NTIS No. PB98- 159163. 

FRITZ, L W. , and S. A. LOWE 1998. Seasonal distributions of Atka mackerel ' Pleurogrammus 

monoD~erygiYID in commercially-fished areas of the Aleutian Islands and Gulf of Alaska, 29 p. NTIS No. 

PB98-153703. 

WING, B. L , and J. J. PELLA. 1998. Time series analyses of climatological records from Auke Bay, 

Alaska, 90 p. NTIS No. PB98-149206. 

PACUNSKI, R. E , P. A. LIVINGSTON , and B. S. MillER. 1998. Food of flathead sole HiDDoglossoides 

elassodon in the eastern Bering Sea, 27 p. NTIS No. PB98-148679. 

WilKINS, M. E, M. ZIMMERMANN , and K. L WEINBERG. 1998. The 1995 Pacific west coast bottom 

trawl survey of groundfish resources: Estimates of distribution , abundance, and length and age 

composition , 138 p. plus Appendices. NTIS No. PB98-136252. 

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 No. PB98-139298. 

SINCLAIR, E H. (editor) 1997. Fur seal investigations, 1996, 115 p. NTIS No. PB98-131790. 

SINCLAIR, EH. (editor). 1997. Fur seal investigations, 1995, 188 p. NTIS No. PB98-131808. 

KINOSHITA, 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.