Results of the Coastal Pacific Whiting, Merluccius productus,Surveys in 1977 and 1980

MARTIN O. NELSON and THOMAS A. DARK

47° JO'

39°30'

43°30'

3r 30'

49" 30'N

Callforn,a

-'1''''30'IO,eqon

~19n ..." ••v ..u

~19S0'(ld19S3

Coocepl,on

Monte.ey

,,-:'2·2'~=====-====-==-==-="======~33° 30129°00'W 124" 00' 11~ 00'

Figure 1. - Areas surveyed in1977 and 1980, and INPFCstatistical areas by which surveydata were summarized.

ducted between depths of 30 and 200fathoms with stations allocated be­tween two depth strata, 30-99 and100-200 fathoms. Due to a change inthe target rockfish species, samplingof the relatively small 201-260 fathomdepth stratum, which had beensampled in 1977, was eliminated; thischange was not considered significantbecause less than 2 percent of thewhiting biomass estimate derivedfrom the 1977 bottom trawl surveywas located in that depth stratum.

(34°08'N) to Kyuquot Sound, Van­couver Island (50°00'N), except thatbottom trawl sampling was limited tothe area south of Cape Flattery,Wash. (48°3CYN). In 1980 the surveybegan off Santa Cruz, Calif.(36° 50'N) and again ended at50°00'N. The change in geographicrange between years was due mainlyto changes in the objectives of therockfish investigations and to the lackof Pacific whiting (other than juvenilefish) south of Santa Cruz. The surveyeach year included two or morevessels for bottom trawl sampling anda single vessel equipped with echo in­tegrator and midwater trawlingsystems to sample the off-bottomcomponent of the population. Theestimates of abundance generated bythe bottom trawl and echo integrator­midwater trawl surveys were con­sidered additive and representative ofthe total population. Figure 1 showsthe survey areas for 1977 and 1980and International North Pacific Fish­eries Commission (lNPFC) statisticalareas used to summarize the surveydata.

Bottom Trawl Surveys

Methods used in the 1977 bottomtrawl surveys are described by Dark etal. (1980) and Gunderson and Sample(1980). The 1980 bottom trawl surveywas similar to that conducted in 1977.Sampling effort was again allocatedon the basis of target species abun­dance as indicated by commercialcatch statistics, including a special ef­fort to sample whiting most intensive­ly in the area off southern Oregonwhere the fishery had been focusedduring 1977-79. Sampling was con-

Introduction

The authors are with the Northwest and AlaskaFisheries Center, National Marine FisheriesService, NOAA, 7600 Sand Point Way N.E.,Bin C15700, Seattle, WA 98115.

A major research vessel survey wasconducted jn 1977 by the NationalMarine Fisheries Service (NMFS) andcooperating agencies to help assess thestatus of Pacific whiting, Mer/ucciusproductus, and other groundfishspecies, especially important speciesof rockfish, Sebastes spp., in theCalifornia to Vancouver Island, B.C.,region (Dark et aI., 1980; Gundersonand Sample, 1980). This was the firstof a triennial series of comprehensivemultispecies groundfish surveys, andit was followed by a comparablesurvey in 1980. Both surveys includedbottom trawl and acoustic (echo in­tegrator)-midwater trawl sampling. Aprimary objective of each year'ssurvey program was to determine thedistribution, biomass, and the length­and-age composition of the ex­ploitable portion of the whitingpopulation. This report summarizesmethodologies used in those surveysand presents results obtained forPacific whiting.

Methods

In both years, the surveys were con­ducted during July through Septem­ber, a period of the year when Paci ficwhiting are between their northwardfeeding migration and southwardspawning migration and coastwisemovements appear to be relativelylocalized. In 1977 the survey includedthe area from Port Hueneme, Calif.

82 Marine Fisheries Review

Biomass estimates were calculatedby the "area-swept" method (assum­ing 100 percent trawl efficiency) andlength samples were weighted bycatch per unit effort (CPUE) to pro­vide estimates of population lengthcompositions by INPFC areas. Age­length keys were derived by INPFCarea and applied to area length fre­quencies to obtain estimates ofpopulation age compositions byINPFC area. Details are presented byDark et al. (1980). The trawl gear,catch sampling methodology, andabundance and biological parameterestimation procedures used in 1980were identical to those employed in1977. Requirements for whiting bio­logical samples in 1980 included thecollection of at least 200 otoliths fromeach depth stratum in each of 12biological sampling areas described byDark et al. (1983).

Echo Integrator-MidwaterTrawl Surveys

The 1977 echo integrator-midwatertrawl survey design and proceduresare described by Dark et al. (1980).The 1980 survey was conductedsimilarly along a zigzag trackline withtransects running obliquely acrossisobaths. The average distance be­tween adjacent transects was 5 n.mi.in 1977, whereas in 1980 it varied be­tween 5 and 7.5 n.mi., dependingprimarily on observed populationdensities. In 1980 the shorewardboundary of the survey area was the30-fathom isobath as opposed to a50-fathom boundary in 1977, and inboth years the seaward boundary was250 fathoms. Transects were extendedif whiting schools were present at theplanned bathymetric limits.

The configuration and use of theecho integration system are describedby Traynor and Ehrenberg (1979),Dark et al. (1980), and Traynor andNelson (1981). Echo sign was sampledto identify acoustic targets by speciesand to collect biological data by usinga midwater trawl with a verticalmouth opening of 18-20 m. Codendmesh sizes (stretched measure) in thetrawls were 33 mm (1977) and 46 mm(1980). Each trawl haul was direc'ted

47(2),1985

at selected fish echo targets using acable netsounder system. Most trawlhauls were made during the day butsome trawling was done at night inconjunction with the collection ofwhiting target strength data, as well asto provide whiting biological samplesfrom areas inadequately sampled dur­ing the day. Biological sampling re­quirements and procedures used forprocessing trawl catches for speciescomposition data and biological datawere not significantly different fromthose used on the bottom trawlsurveys.

The procedures used to derivebiomass estimates were basically thesame as those described by Dark et al.(1980). Whiting aggregations wereidentified from the characteristics oftheir echo signatures and analysis oftrawl species composition data. Ag­gregation boundaries were delineatedby examining the distribution of in­dividual (I min. interval) density(kg/m2 surface area) estimates alongthe survey transects. All the echo in­tegrator data for whiting were scaledto estimates of absolute density byassuming an average target strength(i.e., the target strength of the averagescattering cross section) of - 35dB/kg for the length range en­countered on the surveys. Thevariance (due to sampling) of eachbiomass estimate was calculated usingcluster sampling techniques in themanner described by Dark et al.(1980) and Williamson (1982).

The length distributions of whiting,by INPFC area, were estimated bycombining unweighted midwatertrawl length-frequency samples. Ageand length keys based on otolithsamples were constructed for eachINPFC area and applied to the lengthdistributions to provide percentageage compositions. Procedures fordeveloping age-specific biomass andpopulation estimates are still beingdeveloped. In this paper, estimates ofbiomass by age group and INPFCarea are presented for 1980.

Estimation of Total Biomass

Total estimates of whiting biomasswere made by summing the bottom

trawl survey and acoustic surveyestimates. Although the acousticsystem was capable of sampling to adepth of about 3 m above bottom,target detection actually varied be­tween 3 and 10 m off the bottom, de­pending on the bottom gradient andother factors. It is highly unlikely thetotal estimate was substantially in­creased by the occurrence of whitingin the small interval sampled by bothtechniques. While the bottom trawland acoustic surveys were conductedsynoptically to the extent possible, weacknowledge the potential for the ex­change of bottom and midwaterwhiting aggregations which couldhave resulted in some fish beingcounted by both surveys. Any infla­tion of biomass estimates due to the"double counting" problem wouldtend to be compensated by bottomtrawl estimates which are consideredto be conservative because 100 percenttrawl efficiency is assumed.

Distribution and Abundance

Bottom Trawl Surveys

In 1977, the bottom trawl surveycovered 37,700 km2 and included 666useful hauls (Fig. 2). In 1980, 502hauls were successfully completed in a48,722 km2 survey area (Fig. 3).Estimates of relative abundance, interms of kilograms caught per kilo­meter trawled, are shown geograph­ically in Figures 4 and 5. During the1977 survey, whiting at low densities« 21 kg/km) were distributed muchmore uniformly than in 1980, but inboth years higher densities were veryunevenly distributed. Table I givesCPUE values by INPFC area anddepth, and the most noticeablefeatures are the reduction in CPUE asdepth increased and differences inCPUE among INPFC areas. Thehighest densities were found on thecontinental shelf « 100 fathoms) inboth years. Densities were highest andsimilar in the Columbia, Eureka, andMonterey areas in 1977, but max­imum densities shifted southward in1980. The extraordinarily high CPUEin the Monterey area in 1980 was dueto the presence of a large proportion

83

of the very abundant 1977 year class.The concentration of these young (age3) fish in the Monterey area was con­sistent with the strong tendency forwhiting size and age to decrease withlatitude.

Between 1977 and 1980, there was alarge increase in the biomass of whit­ing estimated to be available tobottom trawls, and the geographicdistribution of biomass changedsignificantly (Table 2 and Fig. 6). In1977, the Columbia area contained 47percent of the estimated biomass; 26percent of the total was in theMonterey area. The relatively lowbiomass (6,560 metric tons (t» in theVancouver area was partially due tothe fact that only a small part of thearea was included in the bottom trawlsurvey. Most of the population in theConception area was age 0 fish whichprobably were not sampled represent­atively. In 1980, 75 percent of the bio­mass was located in the Montereyarea and no other INPFC area con­tained over 11 percent. In theMonterey area, 77 percent of theestimated population was age 3 fish ofthe 1977 year class. In both years,most whiting were located on the con­tinental shelf. Only 13 percent and 3percent of the biomass estimatesbased on bottom trawl samples for1977 and 1980, respectively, werefound in depths greater than 100fathoms.

The 95 percent confidence intervalsassociated with individual INPFCarea-depth biomass estimates for 1977ranged from ± 34 to ± 152 percent ofthe point estimates and averaged ± 57percent. In 1980, confidence intervalsranged from ± 45 percent to ± 160percent with an average of ± 82 per­cent. The variance of the biomassestimates was higher in 1980 eventhough the 1980 sampling was de­signed to increase precision. This isprobably largely because the distribu­tion of whiting in 1980 was asyn­chronous with the survey design,which was based on a predicteddistribution derived from fisherystatistics.

./' J<oo

.""

..

....

Figure 2. - Geographic distribution of bottom trawl stations in 1977.

Figure 3. -Geographic distribution of bottom trawl stations in 1980.

Tablel.-The number 01 bollom trawl hauls and ayerage catch per unit 01 effort (kg/km) 01 Pacific whiling byINPFC area and depth stratum lor 1977 and 1980.

Vancouver! Columbia Eureka Monterey' ConceptionYear and

depth No. of No. of No. of No. of No. of(fathoms) hauls kg/km hauls kg/km hauls kg/km hauls kg/km hauls kg/km

197750·99 32 19.7 104 42.1 20 48.1 78 369 28 7.4100·149 17 6.9 51 9.0 14 9.0 43 13.8 29 10.5150·199 14 14.5 33 5.8 13 6.0 44 10.7 19 8.5200·250 7 2.3 40 5.1 12 1.7 41 4.1 25 1.6

198030-99 65 172 249 16.3 24 52.2 56 218.0100·200 20 6.1 56 3.6 12 15.2 20 19.6

'As indicated in the text and in Figures 2 and 3, there were significant differences between 1977 and 1980 in thelatitudinal extent of the sampling in the Vancouyer and Monterey INPFC areas.

84 Marine Fisheries Review

PACIFIC HAKECATCH (kg/km) I

c::J NO CATCH

§l ·21[]I] 21-50

051-100

."00

, '33°30'N

119°00'W124°30'W123°00'W

, ! E) , 39° 06'N

123G W126 0 W

PACIFIC HAKECATCH(kq/krn} i

c::J NO CATCH

§l.21[]I] 21-50

lj51-100

.>100

44 G 1S'N' >'1 ,126°00'W

-l::..~~ 49° OO'N , < )·I.s&a 4(t Ii Z 2± Ai 1440 15'H 39° OS'N

......'<:>~

I

ill~

~.,.,

~

~

47' OO'NI- A ".-:;;;;r. I I- ~"I, -142' OO'N

1 LP~, I I - ~ I I- ~, 136' OO'N

Figure 4, - Pacific whiting density (kg/km) contours as determined from the 1977 bottom trawl survey,

~

36 DOH40 OON4S OON

~I~ \~~r~~ ] ~f[".. " \ « 1:1 40 DON

44 JON

39 JON

49001'1 1~ If

[ 44 Dati

39 DON

.. '" ] /Uft ~ <J '"

J8 JO/'l

48 CON 43 OON

Un,",",y.d~47 JOti 42 JON 38 DON

" .. ~

~47 DON

CO,," _,,_m~42 OOH

~ ~~~ ~ J7 '0'

46 JON -HIiNO catch

41 JON

HOO:"'" 101}-200 "I I III -JII "-- '-'-- - fI+- 37 DOH

M > 200

Catch kg/km

\i\~ L~ I iiI ro

• I Catch kg/km

iNO catch ~ No catch1-100 1-100

? 100-20040 JON I

... 101}-200 \ Ht 36 JON

.... > 200 :, > 200

127 Jow 126 JOW 125 JOW 124 Jow 123 Jaw 125 JOW 124 Jow 123 JDW 1250011 124 JO .... 124 0010' 123 JO.... 123 00\01 122 JOw 122 00101 121 JO ....

Figure 5.-Pacific whiting density (kg/km) contours as determined from the 1980 bottom trawl survey.

~S·"'~

f.:::0"'<1i;'::t

Table 2.-Eslimated biomass (metric tons) and associated 95 percent contidence intervals of Pacific whiting from bot·tom trawl surveys of 1977 and 1980 by INPFC area and depth stratum.

Year and Biomass (t)depth(fathom) Vancouver Columbia Eureka Monterey Conception Total

19770·99 5,680 29,703 8,792 15,546 780 60,501

± 5,572 (98%) ± 12,767 (43%) ± 10,019 (114%) ± 9,521 (61 %) ±410 (53%) ± 19,251 (32%)

100·149 420 1,592 416 1,707 953 5,088±310 (74%) ± 1,072 (67%) ± 221 (53%) ± 2,603 (152%) ± 450 (47%) ±2,818 (55%

150·199 423 800 227 758 540 2,748±281 (66%) ±482 (60%) ± 175 (77%) ±656 (87%) ±247 (46%) ± 879 (32%)

200·250 37 822 66 255 123 1,303±30 (81%) ±326 (40%) ± 70 (106%) ±86 (34%) ±90 (73%) ± 348 (27%)

Total 6,560 32,917 9,501 18,266 2,396 69,640± 7,873 (120%) ± 12,951 (39%) ± 10,223 (105%) ± 10,036 (55%) ± 652 (27%) ± 16,313 (23%)

198030·99 15,976 19,093 10,689 141,449 187,207

± 12,157 (76%) ± 8,550 (45%) ± 12,059 (113%) ± 82,624 (58%) + 84,724 (45%)

100·200 1,310 1,063 792 2,375 5,540± 1,205 (92%) ± 563 (53%) ± 1,192 (151%) ± 1,526 (64%) + 2,216 (40%)

Total 17,286 20,156 11,481 143,824 192,747± 12,191 (71%) + 8,631 (43%) ± 12,171 (106%) ±82,855 ± 84,754 (44%)

HiO,OOOr

~'OOOI~ ...,"~ 30.000

~ 20.000

iD

1177 1880 ,.77 1'80 Hll1 11110 1.77 11ao

Vancouver Columbia Eureka Monterey

Figure 6. - Bottom trawlsurvey estimates of Pacificwhiting biomass byINPFC area for 1970 and1980.

Acoustic-MidwaterTrawl Surveys

The total distances of the acousticsurvey tracklines (Fig. 7, 8) were 6,464km in 1977 and 4,445 km in 1980. Thetrackline was shorter in 1980 mainlybecause of the reductions in geo­graphic coverage and average transect

Figure 7. - Acoustic survey trackline andgeographic distribution of midwater

trawl hauls in 1977.

Figure 8. - Acoustic survey trackline andgeographic distribution of midwater

trawl hauls in 1980.

47(2),1985 87

density. The number of successfulmidwater trawl hauls completed eachyear, by INPFC area, is shown inTable 3. The smaller amount of trawlsampling in the Vancouver area in1980 was largely the result of vesseloperation problems which reducedthe time available to conduct thesurvey. This decrease in sampling ef­fort was unfortunate because thenumber of species which occur insignificant quantities in midwater ishighest in the Vancouver area andidentification and delineation ofwhiting schools is more difficult thanin the other areas. In addition to whit­ing, the more abundant species in thearea include walleye pollock,Theragra chalcogramma; Pacific her­ring, Clupea harengus pallasi; spinydogfish, Squalus acanthias; yellowtailrockfish, Sebastes flavidus; andredstripe rockfish, Sebastes proriger(Table 4).

Estimates of the biomass of the off­bottom component of the whitingpopulation are shown by year andINPFC area in Figure 9 and by year,INPFC area, and subarea in Table 5.In 1977 the biomass estimates for theVancouver, Columbia, and EurekaINPFC areas were very similar andtogether they included 90 percent ofthe total estimate. Biomass estimateswere not made for the Conception

600

500

c0

400E'0."C

300~§

~ 2000iii

100

1977 80 77 80 77 80 77 80

Vancouver Columbia Eureka Monterey

Figure 9. - Acoustic surveyestimates of Pacific whitingbiomass by INPFC area for 1977and 1980.

88

Table 3.-Number of midwater trawl hauls for 1977 and 1980, by INPFC area andbottom depth (fathoms).

No. of hauls, 1977 No. of hauls, 1980INPFC

area 50·75 76·100 > 100 Total 30·75 76·100 > 100 Total

Vancouver 17 19 6 '42 8 6 3 17Columbia 11 11 6 28 6 21 8 35Eureka 7 6 1 14 2 1 1 4Monterey 5 2 15 '22 9 2 5 16Conception 2 4 4 10

Total 42 42 32 116 25 30 17 72

lTen of the 42 hauls were concentrated in a relatively small area off the northernWashington coast during a 5-day cooperative acoustic survey with foreign researchvessels.2Four of the 22 hauls were made in that part of the Monterey area not surveyed in1980

Table 4.-Percent frequency of occurrence of selected species taken in midwater trawl hauls in 1977 and 1980, bycatch size and INPFC statistical area.

Catch range (Ib) Catch range (Ib)

Year >0 50·499 >500 >0 50·499 >500andspecies % (No.) % (No.) % (No.) % (No.) % (No.) % (No.)

Vancouver Columbia

(42 hauls) (28 hauls)1977Pacific whiting, Merlucc;us productus 83.3 (35) 40.5 (17) 23.8 (10) 96.4 (27) 32.1 (9) 21.4 (6)Walleye pollock, Theragra chafcograrn·rna 61.9 (26) 21.4 (9) 2.4 (1)Yellowtail rockfish, Sebastas flavidus 71.4 (30) 19.0 (8) 2.4 (1) 42.9 (12) 14.3 (4) 3.6 (1)Widow rockfish, Sebastes entomelas 21.4 (9) 7.1 (3) 4.8 (2) 39.3 (11) 17.9 (5)Shortbelly rockfish, Sebastas iordani 10.7 (3)Redstripe rockfish, Sebastes prorigar 11.9 (5) 4.8 (2) 21.4 (6) 10.7 (3)Canary rockfish, Sebastes pmn;ger 11.9 (5) 17.9 (5)Chilipepper, Sebastes goodeiBocaccio, Sebastes paucisp;nls 4.8 (2) 143 (4)Spiny dogfish, Squalus acanthias 50.0 (2) 4.8 (2) 95 (4) 143 (4)Pacific herring, Clupea harengus pallas; 42.9 (18) 48 (2) 4.8 (2) 14.3 (4)Northern anchovy, Engraulis mordax 10.7 (3)Eulachon, Thaleichthys pacificus 50.0 (21) 2.4 (1) 60.7 (12)Jack mackerel, Trachurus symmetricus 4.8 (2)Market squid, Loligo opafascens 3.6 (1)

Eureka (14 hauls) Monterey (22 hauls)

Pacific whiting 85.7 (12) 50.0 (7) 35.7 (5) 86.4 (19) 36.4 (8) 27.3 (6)Walleye pollockYellowtail rockfish 357 (5) 9.0 (2) 4.5 (1)Widow rocktish 286 (4) 14.3 (2) 9.0 (2)Shortbelly rockfish 36.4 (8) 3.6 (3)Redstripe rockfish 14.3 (2)Canary rockfish 21.4 (3) 4.5 (1) 4.5 (1)Chiiipepper 90 (2) 9.1 (2)Bocaccio 36.4 (8) 4.5 (1)Spiny dogfish 50.0 (7) 143 (2) 40.9 (9) 13.6 (3) 4.5 (1)Pacific herring 7.1 (1) 9.0 (2)Northern anchovyEulachon 35.7 (5)Jack mackerel 21.4 (3)Market squid 143 (2) 13.6 (2) 4.5 (1)

Conception (10 hauls) Total (116 hauls)

Pacific whiting 80.0 (8) 10.0 (1) 87.1 (101) 36.2 (42) 23.3 (27)Walleye pollock 22.4 (26) 7.8 (9) 0.9 (1)Yellowtail rockfish 42.2 (49) 11.2 (13) 1.7 (2)Widow rockfish 10.0 (1) 23.3 (27) 4.3 (5) 6.0 (7)Shortbelly rockfish 60.0 (6) 10.0 (1) 14.7 (17; 0.9 (1) 2.6 (3)Redstripe rockfish 11.2 (13) 4.3 (5)Canary rockfish 12.1 (14) 0.9 (1)Chilipepper 50.0 (5) 10.0 (1) 60 (7) 2.6 (3)Bocaccio 50.0 (5) 16.4 (19) 0.9 (1)Spiny dogfish 50.0 (5) 10.0 (1) 396 (46) 6.9 (8) 43 (5)Pacific herring 21.6 (25) 1.7 (2) 1.7 (2)Northern anchovy 10.0 (1) 69 (8) 0.9 (1)Eulachon 37.1 (43) 0.9 (1)Jacl< mackerel 4.3 (5)Market squid 80.0 (8) 10.00 (1) 10.00 (1) 12.1 (14) 1.7 (2) 09 (1)

Marine Fisheries Review

> 0 50·499 > 500 > 0 50·499 > 500

% (No.) % (No.) % (No.) % (No.) % (No.) % (No.)

differences in abundance withinINPFC areas, including a lack of fishin the southern part of the Montereyarea (lat. 35°30'-37°()()'N) and north­ern part of the Vancouver area (lat.49°25'-50°00'N), as well as a distinctdecrease in abundance between thesouthern (lat. 43 o()()'-45°()(),N) andnorthern (lat. 45°()(),-47°3O'N) parts ofthe Columbia area (Table 5).

The amount of change between1977 and 1980 in the total biomassestimates for the off-bottom compo-

Vancouver (17 hauls)

nent of the population was smallcompared to that for fish available tobottom trawls (Tables 2 and 5).However, due to the large size of the1977 year class, there was a similarbut somewhat less pronounced geo­graphic shift in abundance betweenyears. The biomass estimate for theMonterey area in 1980 accounted for43 percent of the total, while onlyabout 10 percent of the total wasfound there in 1977. Also, it wasestimated that over 75 percent of thebiomass in the area was composed of3-year-old fish. North of theMonterey area, the most significantchange in abundance occurred in theEureka area where the biomassestimate decreased by almost 50 per­cent between 1977 and 1980.

In all INPFC areas during bothyears, a majority of the biomass ofthe off-bottom component of thewhiting population was found overthe continental shelf, i.e., inside the100-fathom isobath (Fig. 10). Thepercentage of the total biomasslocated over the shelf increased from59 percent in 1977 to 75 percent in1980. This increase occurred partlybecause the 1980 survey includeddepths of 30-50 fathoms, whereas in1977 that depth zone was sampled

2.9 (1)

5.7 (2)2.9 (1)

34.3 (2)

5.7 (2)

14.3 (5)5.7 (2)2.9 (1)2.9 (1)

2B6 (10)

Catch range (Ib)

200 (7)11.4 (4)29 (1)

2B.6 (10)20.0 (7)11.4 (4)

B57 (30)

2B.6 (10)22.9 (B)B6 (3)5.7 (2)

11.4 (4)

Columbia (35 hauls)

5.9 (1)5.9 (1)

5.9 (1)5.9 (1)

11.B (2)

41.2 (7)11.B (2)17.6 (3)l1B (2)

Catch range (Ib)

Table 4.-Continued.

70.6 (12)235 (4)706 (12)11.B (2)

41.2 (7)5.9 (1)

70.6 (12) 35.3 (6)47.1 (B) 5.9 (1)

41.2 (7)

area because whiting aggregationswere not observed, although trawlsamples revealed age 0 fish dispersedin scattering layers. The Montereyarea estimate was only about one­third as large as that in any of thethree more northern INPFC areas.This probably was a reflection of thefact that the whiting population in1977 was composed primarily of fishthat were age 4 or older which arenormally distributed north of theMonterey area. There were noticeable

Pacific whitingWalleye pollockYellowtail rockfishWidow rockfishShortbelly rockfishRedstripe rockfishCanary rockfishChilipepperBocaccioSpiny dogfishPacific herringNorthern anchovyEulachonJack mackerelMarket squ id

Yearandspecies

19BO

Eureka (4 hauls) Monterey (16 hauls)

31.3 (5) 6.3 (1)50.0 (B) 6.3 (1)

31.3 (5)12.5 (2)37.5 (6) 12.5 (2)12.5 (2)

93.B (15) 1B.B (3)

63 (1)6.3 (1)

37.5 (6)

80 Vancouver ~ 1977

601980

40

20

~l.JIColumbia

U- n. CL..60

~40

i 20

~lJIMonterey

C. =- ~60

40

20

30-49 50-99 100-149 150-199 200-249 ~250

Bottom depth (fathoms)

Figure 10. - Distribution by depth,for each INPFC area, of acousticsurvey estimates of Pacific whitingbiomass for 1977 and 1980.

89

6.3 (1)

1.4 (1)4.2 (3)5.6 (4)2.B (2)

6.3 (1)

2.B (2)1.4 (1)

2.B (2)

lB.B (3)

50.0 (B)

41.7 (30)

2.B (2)1.4 (1)1.4 (1)

22.2 (16)4.2 (3)

11.1 (B)2.B (2)1.4 (1)1.4 (1)

11.1 (B)1.4 (1)

Total (72 hauls)

B4.7 (61)5.6 (4)

33.3 (24)16.7 (12)13.9 (10)125 (9)B.3 (6)B.3 (6)2.B (2)

37.5 (27)19.4 (14)

1.4 (1)23.6 (17)16.7 (12)16.7 (12)

750 (3)

25.0 (1)250 (1)

50.0 (2)

25.0 (1) 25.0 (1)25.0 (1)25.0 (1)

100.0 (4) 25.0 (1)Pacific WhitingWalleye pollockYellowtail rockfishWidow rockfishShortbelly rockfishRedstripe rockfishCanary rockfishChilipepperBocaccioSpiny dogfishPacific herringNorthern anchovyEulachonJack mackerelMarket squid

47(2),1985

Pacific WhitingWalleye pollockYellowtail rockfishWidow rockfishShortbelly rockfishRedstripe rockfishCanary rockfishChilipepperBocaccioSpiny dogfishPacific herringNorthern anchovyEulachonJack mackerelMarket squid

Table 5.-Acoustic survey eslimales of Pacific whiting biomass (I) and associaled 95% confidence intervals for 1977 and 1980, by INPFC area andlatitudinal subarea.

1977 1980

Percent 95% Percent 95%Latitudinal Biomass of confidence Latitudinal Biomass of confidence

INPFC area subarea (t) total interval subarea (t) total interval

48°.26'.49°26' 142,422 12.6 : 30,808 (: 22%) 48°.11'.49°26' 247,742 18.4 : 76,892 (: 31 %)Vancouver 47°.30'.48°26' 201,399 17.8 : 77,459 (: 39%) 48°.03'.48°10' 17,935 1.3 : 28,487 (: 16%)(47 °·30'·50 °30'N)' Area total 343,821 30.4 : 83,325 (: 24%) 4]0.27'.48°00" 56,658 4.7 : 26,068 (: 46%)

Area total 322,335 23.9 : 86,044 (: 27%)

46°.44'.4]030' 15,526 1.4 : 10,358 (:67%) 46°.40'.4]023' 76,813 5.7 : 13,625 (: 18%)45°.50'.46°44' 26,776 2.4 :3,415 (: 13%) 46°.21'.46°36' 19,802 1.5 :10,172 (:53%)45°.00'.45°50' 18,604 1.6 :3,834 (:21%) 45°.41'.46°12' 81,749 6.1 :35,504 (:13%)

Coiumbia 44 °·08'·45 °00' 55,966 5.0 :14,441 (:26%) 45°.10'.45°20' 9,158 0.7 : 2,354 (: 26%)(43°·00'·4]030'N) 43°.00'.44 °08' 199,568 17.7 : 65,879 (: 33%) 44 °·45'·44 °51' 5,516 0.4 : 3,038 (: 55%)

Area total 316,440 28.0 : 68,276 (: 22%) 44°.37'.44 °43' 4,614 0.3 : 3,460 (: 75%)43°.57'.43°59' 555 0.1 :482 (:87%)43°.51'.43°58' 3,513 0.3 : 3,427 (: 98%)42 °·59'·43 °35" 58,757 4.4 : 20,842 (: 35%)Area total 260,477 19.4 :44,979 (: 17%)

41 °.47'.43°00' 169,493 15.0 : 47,710 (: 28%) 40°.36'.42°00' 182,783 13.6 : 45,762 (: 25%)Eureka 40°.25'.41 °47" 191,451 17.0 :60,156 (:31%)(40°·30'·43°00'N) Area total 360,944 32.0 : 76,647 (: 21 %)

Monterey 38°.49'.40°16' 58,860 5.2 : 20,758 (: 35%) 40°.07'.40°15' 3,547 0.3 :2,131 (:60%)(35 °·30'·40 °30'N)' 3]0.07'.38°49' 49,227 4.4 : 25,705 (: 52%) 38°.54'.40°01' 158,534 11.8 :64,184 (:40%)

Area total 108,087 9.6 : 32,949 (: 30%) 37 °·49'·38 °47' 407,225 30.3 : 105,354 (: 26%)3]0·45'·3]047' 9,535 0.7 :10,530 (:110%)Area total 578,841 43.1 : 123,883 (: 21 %)

Total 1,129,292 100.0 :136,375 (:12%) Total 1,344,436 100.0 : 163,875 (: 12%)

lArea between lat 50°00' and 50°30' not surveyed.'Area south of lat. 36°55' not surveyed in 1980.'Includes small part of adjacent INPFC area to south.

only in the northern part of the Van­couver area. Only 7 percent and 3 per­cent of the total acoustic estimates ofbiomass for 1977 and 1980 were indepths greater than 200 fathoms.

Because of the survey method'shigh sampling rate, the estimatedprecision of the acoustic estimates ofbiomass was relatively high comparedwith the precision of bottom trawlbased estimates (Table 5). The 95 per­cent confidence intervals for INPFCsubarea biomass estimates in 1977ranged from ± 13 percent to ± 67percent with a mean of ± 33 percentof the point estimate. For 1980, thecorresponding range and mean were± 16 percent to ± I IO percent and± 51 percent of the point estimate. In1980 estimates were made for severalrelatively small concentrations ofwhiting, and the larger confidence in­tervals reflect the small sample sizes.In both years, none of the confidenceintervals for individual INPFC areasexceeded ± 30 percent. It should berecognized that the confidence inter­vals provide a measure of the preci-

90

sion of the biomass estimates, butthey do not incorporate the effect ofvariability in the target strengthparameter,

Age and Length Composition

Bottom Trawl Surveys

Whiting population-age composi­tions by INPFC area as determinedfrom the 1977 and 1980 bottom trawlsamples are shown in Figure I I. Dur­ing both years the population in mostareas was dominated by one or twoyear classes and the commonlyobserved increase in average age withlatitude was apparent.

In 1977 4- or 7-year-old whiting, orboth, representing the 1973 and 1970year classes, predominated in four offive INPFC areas, The abundance ofthese age groups relative to oneanother is mainly a function oflatitude. The very strong 1970 yearclass (age 7) was the most abundantage group in the Vancouver, Colum­bia, and Eureka areas. Four-year-oldwhiting (I973 year class) were the sec-

ond most abundant age group in theEureka area and were the dominantgroup in the Monterey area. The largesize of the 1973 year class was furtherevident in its unusually high abun­dance in the Vancouver and Colum­bia areas. The 1977 year class (age 0)was the dominant age group (82 per­cent) in the Conception area in 1977,but also was about 7 percent of thepopulation in the Monterey areawhich is indicative of its large size.

In 1980 the whiting populationsampled by bottom trawls in theEureka area and, especially theMonterey area, was completelydominated by 3-year-old fish of the1977 year class, Even though it wasalmost absent in the Vancouver andColumbia areas, that year class ac­counted for about 53 percent of thetotal biomass estimated by the bottomtrawl survey. In the Vancouver andColumbia areas there was no domi­nant age group. The 3-year-oldwhiting did not occur in significantnumbers that far north, and thestrong 1970 and 1973 year classes had

Marine Fisheries Review

WHITING AGE 1977 1980

Vancouver

Vancouver

_._._Females_Males

15

10

25

20

30

o 2 4 6 8 10 13 16 19 22 2:>

1980605550

"4035302520IS10

5o J.....-.,...J,ML,J.,.lP;'-r-~~I~9~27:2~25

1977

Columbia.055

_ 50z 45~ 40~ JS~ 30

2520IS10

5

o .J..,0~2"c4.J..,J,J.Ya.c.c, O.L...9'-J~'.~'~9~2~2~25 o 2 .; 6 8 , 0 13 16 19 22 25

30

25

20

15

10

Length (em)

10 20 30 40 50 60 70 80

Eureka

Monterey

25

10

20

30 Conception

15

10 20 30 40 50 60 70 80Length lem)

15

20

10

25

10

20

30

25

15

30

o 2 4 6 8 10 13 , 5 19 22 2SACE

Eureka

Montereyao7570.5.055

_ 50z 45'ti 40~ 35~ 30

25201510

5o .J..,J...Jl,J..l.,r;J.,JL,.l,L'=__~~~~~16 19 22 2S

.055

_ 50z 45~ 40~ 35~ 30

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5

o ~j.,l.1.c.cl.,.J..,l.,J..lo;"'":':""""'''''''''1"'":9""':':22:'""""':'2'5

~~ Conception

7570.5.055

_ 50z 45'ti 40::::. 3S~ 30

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5o-',..l,.u..-o,.,~~~~~~~~

o 2 4 5 8 , 0 13 \ 6 19 22 25AGE

Figure II. - Age compositions of Pacific whiting byINPFC area for 1977 and 1980, as determined frombottom trawl samples.

Figure 12. - Length distributions of Pacific whiting for1977 and 1980, by sex and INPFC area, as determinedfrom bottom trawl samples.

been significantly reduced in size bythe effects of fishing and natural mor­tality.

The length distributions of whitingfrom bottom trawl samples in 1977and 1980 (Fig. 12) reflect the moreprominent features of the age com-

positIOns. In both years, an increasein mean length with latitude is ap­parent for both sexes, and differencesin length range among INPFC areascorrespond with changes in thenumber of age groups represented inthe samples. The larger mean length

of females in most areas each year isin agreement with growth studies(Dark, 1975) which indicate that afterage 3, the average length-at-age offemales is greater than that of males.Also, it is apparent that among thelarger and older fish, females are

47(2),1985 91

Vancouver

1977605040302010O.......~.........................,........:;?-,........,

810121416

1980

o 2 4 6 810121416

Eureka and Monterey areas were bi­modal in 1980 and mean sizes were2.5.-5.0 cm smaller than in 1977,reflecting the presence of the abundant3-year-old age group together withsmaller numbers of 4- to to-year-olds.

Age

Figure 13. - Age compositIon of Pacific whiting byINPFC area for 1977 and 1980, as determined frommidwater trawl samples.

Eureka

Acoustic-MidwaterTrawl Surveys

Age compositions for 1977 and1980 from midwater trawl samples areshown in Figure 13. In 1977 the trendin age composition by INPFC areawas generally similar to that observedin the bottom trawl samples. In eachINPFC area except Conception, 4- or7-year-olds, or both, predominated.The midwater trawl and bottom trawlage compositions were most similar inthe Conception area where thepopulation was dominated by the ageo group. The most noticeable dif­ferences between the age compositiondetermined from the two types ofsampling occurred in the Columbiaarea where 1- and 2-year-old whitingwere represented in midwater trawlsamples, but absent in bottom trawlsamples; in the Eureka area where4-year-olds dominated in midwatertrawl samples instead of 7-year-oldsas in the bottom trawl samples; and inthe Monterey area where age 0specimens occurred in bottom trawlsamples but not in midwater trawlsamples.

The 1980 midwater trawl age com­positions for the Eureka andMonterey areas were also similar tothose determined from bottom trawlsamples, with both types of samplesclearly showing the dominance of the1977 year class in both areas. The im­portance of this year class is par­ticularly evident in estimates ofbiomass by age (Fig. 14). In the Van­couver and Columbia areas in 1980,where there was no dominant agegroup, there was noticeably morevariation between the midwater andbottom trawl age compositions. Inparticular, 8-year-olds werenoticeably less abundant in the mid­water trawl samples. It is suspectedthat this difference is due to samplingvariability or a bias in age determina-

o 2 4 6 810121416

0246810121416

o 2 4 6 810121416

Age

in the Conception area where unsexedage 0 fish (not shown in Fig. 12) weredominant). The 1980 length distribu­tions in the Vancouver and Columbiaareas were unimodal, but due to theabsence of a dominant age group, themodes were less pronounced than in1977. Length distributions in the

Columbia

Monterey

Conception

o 2 4 6 810121416

o 2 4 6 8 10 12 14 16

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more abundant. In 1977 there weresharp modes at 50-52 cm in the Van­couver and Columbia areas that wererelated to the dominance of 7-year-oldfish in those areas. In the moresouthern areas where younger agegroups were important, the lengthmodes were less pronounced (except

92 Marine Fisheries Review

Columbia

Vancouver

1980

_._.- Females-Males

1977

20

10

15

Monterey450

400

350

300

100r Vancouver

5:[, ! 1~'"=b!""od'6..'~!

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200

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o~~~~t?2h,~~:':-'::--:':-:'::-:'23456789101112131415161718

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Eureka

Age

Figure 14. -Acoustic surveyestimates of Pacific whiting biomassfor 1980, by age and INPFC area.

tions. As in the case of the bottomtrawl sample age composition, thestrength of the 1973 and 1970 yearclasses was still apparent in therelative abundance of 7- and lO-year­old fish in the Vancouver-Columbiaregion. In most instances, the lengthdistributions of midwater trawlsamples (Fig. 15) were similar to thoseof bottom trawl samples, with notice­able differences between the two typescorresponding with the more obviousdifferences in age composition men-

20

15

10

30

tioned previously. Although the dif­ferences were relatively small, therewas a consistent tendency for themean length of whiting taken in mid­water trawl hauls to be less than that

Monterey

in bottom trawl hauls. With the ex­ception of the Vancouver area in 1977and the Columbia area in 1980 (malesonly), this difference by gear type oc­curred for each sex, in each INPFCarea, during both years (Table 6).

Table 6.-Mean lengths (cm) 01 Pacilic whiting (male, lemale, and combined) In bottom trawl and mldwater trawlcatches by INPFC area lor 1977 and 1980.

INPFCarea Male Female Comb. Male Female Comb. Male Female Comb. Male Female Comb.

Vancouver 50.4 52.5 51.8 51.4 53.8 53.0 52.8 55.9 55.2 52.0 54.9 53.8Columbia 50.1 51.6 50.9 48.6 49.8 49.2 49.7 52.0 51.1 49.7 51.2 '50.0Eureka 47.1 48.6 48.0 45.2 45.7 45.4 44.8 45.8 45.3 42.4 43.0 42.7Monterey 44.2 47.0 '43.1 42.7 43.1 42.9 40.6 40.4 40.5 39.8 40.3 '39.6

'Includes unsexed specimens which were nearly all ",20 em.

Bottom trawl

1977

Midwater trawl Bottom trawl

1980

Midwater trawl

Total Biomass Estimates

Total whiting biomass estimateswere 1,198,932 t and 1,537,183 t in1977 and 1980, respectively (Table 7).In both years, a very large percentageof the total estimate and the estimatesfor each INPFC area' were derived

I Excluding the Conception area in 1977 whichhad no acoustic estimate.

47(2),1985 93

Table 7.-Combined bottom trawl survey and acoustic survey estimates of Pacific whiting biomass (t) for 1977 and 1980, by INPFC area.

1977 1980

Boltom trawl Acoustic TOlal Boltom trawl Acoustic Tolal

INPFC t I I I Iarea ('!o)' (%F (%)' (%)2 ('!o)' (%F (%)1 (%)2 (%)' (%)2 (%)' (%)2

Vancouver 6,560 9.4 343,821 30.4 350,821 293 17,286 9.0 322,335 23.9 339,621 22.1(1.9) (98.1) (100.0) (5.1) (949) (100.0)

Columbia 32,917 47.3 316,440 28.0 349,357 29.1 20.156 10.5 260.477 19.4 280,633 18.3(9.4) (90.6) (1000) (7.2) (92.8) (100.0)

Eureka 9,501 13.6 360,944 37.0 370,445 309 11.481 5.9 182,783 13.6 194,264 12.6(2.6) (97.4) (100.0) (5.9) (94.1) (100.0)

Monterey 18,266 262 108,087 9.6 126.353 10.5 143,824 74.6 578,841 43.1 722,665 47.0(14.5) (855) (100.0) (199) (80.1) (100.0)

Conception 2,396 3.4 2,396 02(100.0) (100.0)

Tolal 69,640 100.0 1,129,292 1000 1,198,932 100.0 192,747 1000 1,344.436 100.0 1,537,183 100.0(5.8) (94.2) (100.0) (125) (87.5) (100.0)

'Percentage by type of survey.'Percenlage of total for all INPFC areas combined.

from the acoustic survey, Except forthe Monterey area, the bottom trawlestimates were all less than 10 percentof the combined estimates. The dif­ference between the two types ofestimates was noticeably less in theMonterey area, particularly in 1980,and suggests that 2- and 3-year-oldwhiting may be relatively lessavailable to acoustic sampling thanolder age groups. The exceptionallylarge difference between the two typesof estimates in the Vancouver area in1977 was partially due to the absenceof bottom trawl sampling in most ofthat area. The distribution of thebiomass among INPFC areas wasessentially the same as that describedpreviously for the acoustic estimates.

Summary

The results of acoustic and bottomtrawl surveys conducted in 1977 and1980 have provided additional infor­mation on the biology and behaviorof Pacific whiting. The highlyvariable year-class strength reportedby others (Alverson and Larkins,1969; Dark, 1975; Bailey et al.,2) wasobserved in both years. The 1973 yearclass was dominant in 1977, and 3years later the 1977 year class was ex­tremely abundant. The estimatedbiomass increased about 28 percent

'Bailey, K. M., R. C. Francis, and P. R,Stevens. 1982. The life history and fishery ofPacific hake Merluccius productus. ProcessedRep. 82-03, 81 p, Northwest Alaska Fish. Cent.,Natl. Mar. Fish. Serv" NOAA, 7600 SandPoint Way N,E., Bin CI5700, Seattle, WA98115.

94

between 1977 and 1980 from1,129,000 t to 1,537,000 t, primarilydue to the recruitment of the 1977year class. Such variable recruitmentnot only influences the size of thewhiting resource but also affects itscoastwide distribution. The center ofabundance can occur almost any­where over about 12 degrees oflatitude depending, at least partly, onthe age structure of the population.Ten percent of the biomass was in theMonterey area in 1977, but 47 percentwas estimated to be there in 1980when the population was dominatedby 3-year-olds.

The coastwide distribution of thebottom component of the populationwas more uniform in 1977 than in1980 and in both years most of theresource was located over the con­tinental shelf in waters less than 100fathoms deep. On the average, 90 per­cent of the biomass was found to beaggregated in pelagic schoolsunavailable to the bottom trawls used.The mean size of whiting taken by

midwater trawl tended to be slightlysmaller than the mean size in bottomtrawl samples. This may be a reflec­tion of feeding behavior, with smallfish seeking euphasiids and plank­tonic organisms throughout the watercolumn and large fish focusing theirfeeding efforts on a greater array ofprey species including fish and shrimpfound adjacent to the bottom.

Further information about meth­ods and a discussion of the accuracyof biomass estimates and the role ofsurveys in assessments of Pacific

whiting can be found in Nelson andDark (In press).

Literature Cited

Alverson, D. L., and H. A, Larkins, 1969.Status of knowledge of the Pacific hakeresource. Calif. Coop. Oceanic Fish. Invest.Rep. 13:24-31.

Dark, T. A. 1975. Age and growth of Pa­cific hake (Merluccius productus). Fish. Bull.,U.S. 73:336-355.

--::::-=--=-' M. O. Nelson, J. J. Traynor, andE. P. Nunna1ee. 1980. The distribution,abundance, and biological characteristics ofPacific hake, Merluccius productus, in theCalifornia-British Columbia region duringJuly-September, 1977. Mar. Fish, Rev.42(3-4):17-33.

_:-::-::-:---:' M, E. Wilkins, and K. Edwards.1983. The results of a 1980 bottom trawlsurvey of the canary rockfish (Sebastes pin­ninger) , yellowtail rockfish (S. f1avidus) ,bocaccio (S, paucispinis), and chilipepper (S.goode/) resources in the Washington­California region, U.S. Dep, Commer. ,NOAA Tech. Memo. NMFS F/NWC-48, 40p.

Gunderson, D. R., and T. M. Sample. 1980.Distribution and abundance of rockfish offWashington, Oregon, and California during1977. Mar. Fish. Rev. 42(3-4):2-16.

Nelson, M. 0., and T. A. Dark. In press. Thedistribution, abundance, and biologicalfeatures of the Pacific whiting resource basedon 1977 and 1980 research vessel surveys. Int.North Pac. Fish, Comm. Bull.

Traynor, J. J" and J. E. Ehrenberg, 1979,Evaluation of the dual beam acoustic fishtarget strength measurement method. J. Fish,Res, Board Can, 36:1065-1071.

----:,----,---_, and M. O. Nelson. 1981. Cal­ibration of a computerized echo integrationand dual beam target strength measurementsystem. In J. B. Suomala (editor), Meeting onhydroacoustic methods for the estimation ofmarine fish populations, 25-29 June 1979,Volume 2, Part a, Contributed papers,discussion and comments, p. 395-424,Charles Stark Draper Lab" Inc., Cambridge,Mass.

Williamson, N, J. 1982, Cluster samplingestimation of the variance of abundanceestimates derived from quantitative echosounder surveys, Can, J, Fish. Aquat. Sci,39:229-231.

Marine Fisheries Review