vol 23 bailey etal

8/8/2019 Vol 23 Bailey Etal

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY A N D FISHERYCalCOFl Rep., Vol. XXIII, 1982

THE LIFE HISTORY AND FISHERYOF PACIFIC WHITING, MERLUCClUS PRODUCTUS

KEVIN M. BAILEY,' ROBERT C. FRANCISNorthwest and Alaska Fisheries Center

National Marine Fisheries ServiceSeattle, Washington 981 12

ABSTRACTThe Pacific whiting is one of the most abundant and

important fishes of the California Current region. Thisreport synthesizes available data, published and un-published, o n the life history and population dynam icsof whiting. Aspects of the life history described aredistribution, spawning, early life history, feeding, andgrowth. Information on the population dynamics ofthe stock is summarized with attention to stock abun-dance, recruitment variability, and mortality. A syn-thesis of the fishery, its development and manage-ment, is presented.

RESUMENMerluccius productus es una de las especies mas

abundantes e importantes e n la regi6n de la Corriente deCalifornia. En este trabajo se recopilan 10s datos pu-blicados e inkditos sobre el ciclo de vida y dinim ica depoblaciones de M. productus. Los aspectos del ciclode vida que se discuten incluyen; di st rib uc ih , puesta,fases larvales y juveniles, alimentacibn y crecimien to.La informacih sobre la dinimica de la poblacih seresume en relaci6n con la abundancia de las existen-

cias, variaciones en el reclutamiento y la mortalidad.Se presenta ademis una shtesis de las pesquerias, sudesarrollo y administracibn.

INTRODUCTIONCommercially and ecologically the Pacific whiting

(also called Pacific hake), Merluccius productus, isone of the most important fish species on the westcoast of North America. It supports a large commer-cial fishery that has been dominated by foreign na-tions. In recent years, however, a U.S. fishery hasdeveloped through ventures with foreign nations. Be-sides being an important resource to man, whiting is

an important trophic link in the California Currentecosystem. As a large predator, whiting interacts withother fish and shellfish populations, notably the com-mercially important stocks of Pacific herring,Clupeaharengus pa llasi; northern anchovy, Engraulis mor-dux; and shrimp. Whiting is also important as prey inthe diets of marine mammals itnd large fishes.

The objective of this synopsis is to synthesize avail-able information on the biology and fishery of the'Current address: College of Fisheries, University of Washungton, Sea&, WA 98195[Manuscrip received January 1 1 , 1982.1

PAYSON R. STNENSScripps Institution of OceanographyUniversity of California, San Diego

La Jolla, California 92093

coastal stock of Pacific whiting. Since the publicationof a similar synopsis in 1970(U.S. Fish and WildlifeService 1970), a great deal of new information hasbecome available. M ost of this material is unpublishedand thus is generally unavailable to scientists, mana-gers, and fish ermen . Further goals of this synopsis areto present new information, particularly concerningthe migration of whiting, and to suggest areas ofneeded research.

THE CALIFORNIA CURRENT SYSTEM-THEHABITATOF PAC IFIC WHITING

Pacific whiting ranges from the Gulf of Alaska tothe Gulf of California (Ha rt 1973); however, it is mostabundant within the region of the California Currentsystem. The California Current system is the easternboundary curren t system of the North Pacific Ocean. Itextends from the coastal divergence of the westwinddrift at 45"N in winter (and50" in summer) southwardto about 23"N, where California Current water mixeswith equatorial water and bends westward to form theNorth Equatorial Current. The California CurrentIsystem is composed of (1) an equatorward surface

flow-the Californ ia Curren t;(2) a seasonally occur-ring poleward surface current identified as the David-son Current north of Pt. Conception, and as theCalifornia Countercurrent in southern California; and(3) a poleward subsurface flow-the California Un-dercurrent. Numerous gyres, including the SouthernCalifornia Eddy, are semipermanent features of theCalifornia Current system. The individual currents arebriefly discussed below; a more detailed review canbefound in Hickey (1979).

The flow of the California Current is driven bywinds and is slow, broad, and shallow. Water of theCalifornia Current is subarctic in physical and chemi-

cal properties at high latitudes, characterized by lowsalinity and temperature. As the water flows south-ward, it becomes more intermediate in nature throughmixing with the high-salinity and high-temperaturewater of the North Pacific Current and the CentralPacific water mass. Eventually, California Currentwater becomes semitropical off southern Mexico aftermixing with equatorial water.

The Davidson Current is the surface poleward flownorth of Pt. Conception that develops in winter. TheDavidson Current appears in October off Vancouver

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY AN DFISHERYCalCOFI Rep., Vol. XXIII, 1982

Island and de velop s later farther south . It exists off theOregon-Washington coast from October until Feb-ruary and off the California coast from No vembe r untilJanuary.

The C alifornia Undercurrent is a northward flow of

high-salinity,

high-temperature water occurring sea-ward o f the continental shelf and below the main pyc-nocline. Wooster and Jones (1970) reported that theundercurrent was found 75 km offshore of Cab0 Col-nett, Baja California, and was centered at 200-500-mdepth off the Oregon-Washington coast. A polewardundercurrent develops o ver the con tinental shelf in latesummer and early fall (Hickey 1979).

LIFE HISTORY

Stocks and DistributionStocks. At least four distinct stocks of Pacific whit-

ing may exist. These include (1) a coastal stock rang-ing from Canada to Baja California,(2) a Puget Soundstock, (3 ) a Strait of Georgia stock, and (4) a dwarfstock found off Baja California. Two of the stocks,h g e t Sound and the coastal stock, have been iden-tified as genetically distinct spawning stocks (Utterand Hodgins 1971).

The separate identities of the dwarf and coastalstocks are at present controversial. Ahlstrom andCoun t s (1955) examined l a rvae found o ff Ba j aCalifornia and were not able to distinguish two sepa-rate stocks, thus supporting a concept of one spawningstock. However, M acGregor (1971) and Vrooman andPaloma (1977) discussed several differences in adultdwarf whiting found off Baja California comparedwith the adult coastal whiting found farther north.Dwarf whiting grow slower from age one onwards,mature earlier, and have several different morphomet-ric and meristic characteristics compared with thecoastal whiting. Vrooman and Paloma( 1977) believedthat these differences indicate separate stocks. How-ever, the differences may not be genetic, and are notinconsistent with changes caused by environmentaleffects in the different habitats.

The remainder of this report deals with the coastalstock, which is the most abundant and commercially

important.Dis t r ibu t ion . As indicated previously, Pacif icwhiting are found within the coastal region of theCalifornia Current system. Normally whiting are notcaught seaward of the continental slope, althoughthere are occasional reports of whiting eggs and larvae(as well as of juveniles and adults) far seaward of theslope (Frey 1971). The latitudinal distribution ofwhiting varies seasonally. In autumn adult whitingmake an annual migration from the summertimefeeding grounds off the Pacific Northwest coast to

spawn in winter off the coasts of southern Californiaand Baja California. In spring and summ er, large fishmigrate northwards as far as central Vancouver Island,and juveniles remain off the Californias. The migra-tion of whiting is outlined in Figure 1 and is describedin detail below.

SpawningSpawning scho ols of Pacific w hiting have been dif-

ficult to locate. Nelson and Larkins (1970), Tillman(1968 ), Bureau of Commercial Fisheries 1964 l, Eriche t a l . (198 0) , and StepanenkoZ repor t spaw ningschools off southern California in midwater at depthsof 130-500 m and over bottom depths correspondingto those of the continental slope. (Spawned at thesedepths, eggs float upwards to the base of the mixedlayer.) Ermakov (1974) also reports spawning overthe continental slope. H owever, Erich e t al. (1980)report a spaw ning school some 400 km seaward in thesouthern part of the Southern California Eddy, andStepanenko3 reports a spaw ning school about 30 0 kmoffshore in central California.

The distribution of egg s and small larvae (2-3 mm )indicates that whiting spawn from Cape Mendocino tosouthern Baja California. Almost all eggs and larvaeare located o ver water dep ths corresponding to depthsof the continental slope, except in the SouthernCalifornia Eddy, where eggs and larvae are oftenfound over very deep water and far out to sea (400km). Bailey (1981a) postulated that whiting spawn inthe California Undercurrent, which usually occurs

over the continetal slope at depths of 200-400 m, butspreads seaward some 200-400 km in the SouthernCalifornia Eddy and some other locations where ed-dies occur. Large concentrations of eggs and larvaeare found overlying areas of northward geostrophicflow at 200-m depth (Figure 2).

Variation may exist in the latitudinal distribution ofspawning. The location of the apparent northern frontof spawning is correlated to the sea surface tempera-ture (Table 1). Assuming that temperatues at the seasurface are correlated to those at the depth of spawn-ing, this indicates that in warm years when subtropicawater is farther north, spawning occurs at higher

latitudes. Alternatively, larvae may be transported bya northward flow.IBureau of Commercial Fisheries. 1964. Cruise report: exploratory cruise N o. 6 4 .Unpubl. manuscr. Northwest and Alaska Fish. C ent., Natl. Mar. F ish. Serv ., NOA A,2725 Montlake Blvd. E ., Seattle, WA 981 12.2Stepanenko, M. A. 1978. m e patterns of the abundance of the California anchovyand Pacific hake, and estimation of their biom ass, 1976-1977. Unpubl. manuscr.Pacific Sci entific Research Institute of Marine Fisheries and Oceanography (TINRO ),Vladivostok, USSR.3Stepanenko, M.A . 1980. Reproductive condition and assessment of the spawningstocks of Pacific hake, California anchovy, horse mackerel, and some other fishspecies in the California Current zone in 1979. Unpubl. manuscr. Pacific ScientificResearch Institute of Marine Fisheries and Oceanography (TINRO), Vladivostok,USSR.

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BAILEY ET AL.: ACIFIC WHITING LIFE HISTORY AN D FISHERYCalCOFI Rep., Vol. XXIII, 1982

w JYPACIFIC WHITING hM I G R A T I O N B E H AV IO R C A N A D A

I

By JulyIAugustmoving to outercontinental shelf

Cape Flat tery \.-:::WASHINGTON.

Destruction Island

Heceta Bank

- - - - - - _

W I N T E RMigrating offs hore over slopein California current (south)

OREGON

C A L I F O R N I A

4\

Spawning

Ea FeedingMain School ing Area

51 30N

4 1 30 N

43 30N

39 30N

3 5 30N

31 30N

27 30 N

138 O O U

Figure 1. Migratory patterns of Pacific whiting.

12 8 oou I 18 oou

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BADLEY ET AL.: PACIFIC WHITING LIFE HISTORY AND FISHERYCalCOFI Rep ., Vol. XXIII, 1982

I I I I 1I I I I 1200 115' 110I

130. 125'1 I I 4 1 I I 1 1 I

42\

46\\

44

\, ..:*Y

A4 2 \

\

*I

IIII

I

' A L ' O F I

JANUARY

1950-65 M E A N

GEOSTROPHIC FLOWAT 2 0 0 m DEPTHCAPEME NDOCINO ( T O P O G R A P H Y O F T H E 2 0 0 OEClOAR SURFACE,IN D Y N A M I C M E T E R S , R E L A T I V E T O T H E500-O E C I B A R S U R FA C E 1

4 0 0''

SANFRANCISCO

4 ? . . t 3

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. \\

- 4s ,

50.

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' C O G mea1 1 I I 1 I 1 1 I I I I I I 1 I 1 I 1 1

130- 125. 120" I 15' I O"

MEAN 200/500 b

JANUARY

_ _

Figure 2. Large catches of Pacific whiting eggs and larvae (all size classes) in January surveys, 1950-79, plotted on a chart showing geostropic flow at 2 00-m depth(from Wyllie 1967).

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BAILEY ET A L.: PACIFIC WHITING LIFE HISTORY AND FISHERYCalCOFI Rep., Vol. XXIII, 1982

TABLE 1The Northward Extent of 2-3-mm Standard Length WhitingLarvae' during January Surveys, Compared to the Average

January 50-Meter Temperature in the Los Angeles Bight

Year "C Rank Line Rank

1963 12.0 9 87 8 .51964 13.2 4 76 41965 12.4 7 80 61966 13.5 3 70 2.51968 12.8 5 70 2.51969 13.6 2 80 61972 12.2 8 87 8 .51975 12.6 6 80 61978 13.9 1 63 1

Temperature Distance

*Measured by the northernmost CalCOFI line where larvae occurred innumbers greater than 100 larvae/lO mz.Smaller line numbers are farther north. Temperature and northward extentof larvae are significantly correlated using a Spearman rank correlationstatistic (P


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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY AN D FISHERYCalCOFI Rep., Vol. XXIII, 1982

spots on the dorsal crown of the hea d, sturdy bodies,and 51-54 myomeres (Figure 4). Preserved yolk-saclarvae are 2.5-3.0 mm standard length. Shrinkage oflarvae due to handling is highly variable, from 1 0 4 %depending on the preservative and on the time fromdeath to preservation (Bailey, in press; Theilacker1981).

Time to absorption of the yolk is temperature de-pendent (Bailey, in press). At ambient temperatures,absorption of the yolk m ay take 120-200 hours. Amouth d evelops before the yolk is fully depleted, andyolk-sac larvae are observed to feed (Sumida andMoser 1980). Larvae take 150-250 hours to starveafter yolk depletion (Bailey, in press).

Daily growth of whiting larvae has been describedby counting growth increments on their otoliths(Bailey, in press). G rowth in length appears to be slowand cons tant for the first 20 days, after which it rapidly

accelerates (Figure 5).In the laboratory, predators on yolk-sac larvae are

m o r e v a r i e d t h a n t h o s e o n e g g s a n d i n c l u d eeuphausiids, medusae, ctenophores, amphipods, andcarnivorous copepods. Invertebrate predation onwhiting larvae is stage- or size-specific; larger larvaeare not as vulnerable to predators as yolk-sac larvae(Bailey and Yen, in press).

The diet of larval whiting is composed mostly ofcopepod eggs, calanoid copepod nauplii, copepo-dites,and copepod adults (Sumida and Moser 1980).Whiting larvae have relatively large mouths and feedon a broad size range of prey from 50-4 00 p m inwidth.

Competitors of whiting larvae in the ichthyo-plankton sharing the same temporal and spatial dis-tributions are California smoothtongue,Bathylaguss t i l b iu s , and snubnose b l acksme l t , B a t h y l a g u swesethi. Overlap in the vertical and horizontal dis-tr ibution also occurs with Vinciguer r ia luce t ia ;rockfish, Sebastes spp. ; and jack m ackerel,Trachurussymmetricus. Num erous carniv orous invertebrates arealso competitors.

The vertical distribution of whiting eggs and larvae.Eggs are released at 130-500 m in spawning , and most

rise up wards to a depthof neutral buoyancy, usually at40-60-m depth, near the base of the mixed layer

TABLE 2Percent Biomass of Juvenile Pacific Whiting by

Depth Interval and by Age

Depth Ag e (YO(fathoms) 0 1 2 3

~~

0-99 95 .4 35.8 14.6 30.7100-199 4 .4 63 .4 59 .6 41 .8

0 . 2 0 . 8 2 5 .8 27 . 5

100.0 100.0 100.0 100.0- -50-199 -From th e summer 1977 Northwest and Alaska Fisheries Center bottom-trawl survey.

(Ahlstrom 1959). If a strong pycnocline does noexist, eggs and larvae may be distributed through thmixed layer. Some evidence exists that larger larvaemay be distributed deeper than small larvae (Bailey, inpress).

Juvenile stage. Not much is known about juvenilewhiting. Juveniles 1 -3 years of age are found primariloff central and southern California (Figure6). Most0-1 year-olds occur inshore of the 200-fathom (fmisobath, and older fish are distributed somewhafarther offshore than younger fish (Tab le 2). The foodof juvenile whiting is mainly copepods and euphausiids (P. Livingston The Feeding Biology of PacificWhiting, in review).

Adult Life HistoryMigratory behavior. Tagging of Merluccidae has

not proved feasible (Jones 19 74); thus the m igrationof Pacific whiting are inferred from survey andfisheries data.

Pacific whiting become scarce in survey catche(Table 3) and in the fishery (Table 4) from autumnuntil early spring (see also Jow 1973 ; Best 1963; Alto1972), and whiting eggs and larvae are most abundanin winter off California. These observations have ledto a hypothesis that adult whiting leave the coastawaters in autumn to migrate from the shelf and southward for spawning in winter, and then return northward in early spring (Alverson and Larkins 1969)This migratory pattern has been verified from morerecent data (Ermakov 1974; Dark et al. 1980).

Speeds of migration may be estimated from the se

quential appearance of fish up the coast after spawning. P ostspawning accumulations of wh iting normall

TABLE 3Average Trawl Catches (Pound per Hour) of Pacific Whiting by Month and Year

Year J a n . Mar. May July Aug. Sept. Nov. Dec .1961 - - - 2,403 - 9,784 -1962 - 45 71 - 11,131 - 42 5 -

Mean 100 45 123 2,403 7,723 9,7 84 438 97

97

-- ~ ~ ~ -- -75 - 4,315 - 45 0963 100

From Alton 1972.

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY AN D FISHERYCalCOFI Rep ., Vol. XXIII, 1982

Figure 4. Stag es of Pacific whiting larvae (from Ahlstrom and Counts 1955).

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY AND FISHERYCalCOFI Rep., Vol. XXIII, 1982

TABLE 4The Proportion of Soviet Catches in the INPFCVancouver-Columbia Area by Month, 1973-76

Month 1973 1974 1975 1976 X

1

23456789

101 112

---

.032

.008, 1 0 6,305.296,158,094--

--

,012,073,085.049,212.116,453---

----

,026,163.406

,167,136,086.016

-

-

---

,122,207,202,261.188.017

.002-

-

-

,003,026,060.131,281,210.234,049.004-

have appeared around San Francisco (38"N) in earlyMarch (Ermakov 1974; Erich et al. 1980) and havebeen later observed off southern Oregon(42"N) in the

third week of April for five consecutive years from1966 to 1971 (Ermakov 1974). A population travelingon this schedule would move, on the average, about10 k d d . By May, concentrations appear off Van-couver Island. These estimated mean populationspeeds compare favorably to speeds obtained fromdirect observation of individual schools. Ermakov(1974) concluded from direct observation of a leadschool that the northward migration is at speeds of

Ermakov (1974) hypothesized that the timing of thespaw ning migration w as linked to the seasonal appear-ance o f t he Dav idson Cur ren t o ff t he Oregon-Washington coast. Analysis of the movement of theSoviet fishing fleet in relation to Bakun's (1973,

5-1 1 k d d .

8 O r1

4 0 . 0 -w

0 5.0 10.0 15.0 20.0INCRWENTS3 0 . 0 -

20 .0 -

010 25 .O 50 .O 7 5 . 0 100.0 125.0 150.0

INCREMENTS

Figure 5. The growth of larvae caught off southern California determined fromotolith increments. A Gompertz curve was fitted to the data, Y = 1.72'exp[3.15 '(/ - exp [-0.02624'Xl)1.Insef?: dailygrowthforthef irst 20dayswas better fitted with a straight line (Y = 2.75 + 0.16x) (from Bailey,in press).

kGE 2

A G E ' r i

AGE I

n

AGE L

A R E A

Figure 6. The distribution of biomass by International North Pacific FisheriesCommission area for each age d ass in the 1977 Northwest and AlaskaFisheries Center trawl survey: Area 1, Conception; Area 2, Monterey; Area3, Eureka; Area 4, Columbia; Area 5, Vancouver (from Bailey and Ainley, inpress).

1975) indices of wind stress tends to support thihypothesis. Adult whiting generally begin to disappeafrom the Pacific Northwest in autumn when the windirection shifts and the Davidson Current appears.

Adult whiting also make seasonal inshore-offshormigrations. Ermakov (1974) reports that in spring anearly summer whiting schools concentrate over thcontinental slope. By mid-June, a large portion of thstock moves inshore to depths less than 100 m. Laterin early August, whiting move offshore, and by midOctober they begin to migrate southward for spawning. These observations of bathymetric migrations arsupported by data in Alton (1972) showing that thaverage depth of catches in bottom trawls decreased iearly summer and increased in autumn (Figure 7)These movements are similar to the dynamics of thCalifornia Undercurrent, which is located over thcontinental slope in spring and spreads over the shelin early sum mer (Huyer et al. 1975; Huyer and Sm it1976). Further research on the migration of w hiting irelation to ocean currents is needed and would be o

value to stock assessment and management efforts.Adult whiting also migrate on a diurnal scheduleFish are dispersed from near surface to 20-m depth anight (10 p.m. to 3 a.m.). They descend quickly adawn and form schools. At night they rise to the surface again in 30-40 min (Nelson and Larkins 1970Ermakov 1974). These diurnal migrations have beecompared to the migrations of their primary preyeupha usiids, as a causal mechanism (Alton and Nelso1970). As noted previously, spaw ning whiting do noappear to migrate vertically.

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORYANDFISHERYCalCOFl Rep., Vol. XXIII, 1982

TABLE 7The Percent Occurrence of Food Types in the Diet of Pacific Whiting Determined by Soviet Scientists.

Washington-Oregon CaliforniaMonth Month

6 9 10 3 4 5 6 1199.6 1. 2 40.2 83.3 83.1 99.8 84.0 93.5

Food type 5

Shrimp 4.9 0.4 17.3 1.3 -Squid - -Fish 14.3 -

*Erm akov, Y ., and A.M . K harchenko. 1976. Biological characteristics of Pacific hake and the estimation of its abundance in 19 75. Unpubl. manuscr. PacScientific Research Institute of Marine Fisheries and Oceanography (TINRO), Vladivostok,USSR.

Euphausiids 81.6

15.2- 1. 3 -

12.4 37.7 5.6 0.9 1.4 1.4 10.9

----

L I , I 1 1 1 I3 0 4 0 5 0 G O 7 0 8 0 9 0 10 0 I 1 0 1 2 0

Age l y r i

Figure 8. The annual growth in weight of Pacific whiting (from Dark 1975, solidlines) compared o seasonal estimates of growth by age dass (from Francis,unpubl. manuscr., dotted lines).

also found that to accurately represent the seasonaldynamics of growth a separate weight-length equationwas needed for each age. Figure 8 gives a comparisonof the weight-age relationships arrived at by Dark(1975) for 1964-69 and Francis (1982) for 1976-80.

Feeding. The feeding behavior of Pacific whitinghas been studied by several investigators, but a com-prehensive seasonal and geographic examination offeeding is lacking.

Adult whiting probably do not feed on the spawninggrounds (Tillman 1968 ) but begin to feed raven-ously during the postspawning migration north (Er-makov 1974). In summer, whiting are observed tofeed at night towards the surface (Alton and Nelson1970); how ever, if patches of prey are abundant nearbottom, whiting may remain there at night to feed(Ermakov 1974).

There are apparent geographic, seasonal, annual,and size-specific differences in feeding behavior. Themost frequently occurring prey items in the summerdiet are euphausiids and Pacific sand lance,Ammo-dytes hexapterus, off Vancouver Island (Outram andHaegele 1972) and euphausiids and shrimps fromCalifornia to Washington (Alton and Nelson 1970;Gotshall 1969a). Ermakov and Kharchenko8 foundthat off Washington and Oregon euphausiids decrease

TABLE 8The Percent by Weight of Food Types in the Diet of PacificWhiting Determined by Polish Scientists* in Summer 1979

RegionFood type Eureka Columbia Vancouver

Euphausiids 94.2 94.0 85.6Juv. rockfish 1 .o 1. 6 -

5. 9acific hemn g - -6.6uv. Pacific herring -

Osmerids - 0. 4 -Pacific whiting 0.5 - -

2.0 0.1ablefish -Flatfish - 0. 4 -Squid 0.7 - -Shrimp - 1.6 -Other fish 3. 2 -Other 0.4 -

*Jackowski, E. 1980. Biological characteristics of Pacific whiting fromPolish surveys of the west coast of the U.S.A. and Canada in 197Unpubl. ma nuscr., presented at :he U. S.-P oland bilateral meetings, 1 98

-

1. 70.1

in frequency of occurrence in the diet in autumn compared to summer (Table 7). Shrimp and fish sometimes occu r frequently. Jacko wskiy found that isummer off Vancouver Island, Pacific herring werimportant in the diet of whiting (Table 8); and inorthern California waters where adult and juvenildistributions overlap, cannibalism is often observe(T . Dark, pers. comm.).

Livingston (The Feeding Biology of Pacif iWhiting, in review) found that Pacific herring weran important component in the diet of whiting ofOregon-Washington in 1980, composing almost 70%of the diet (by weight) of whiting greater than 55 cmand 50% of the diet of whiting less than 55 cm. Altonand Nelson (1970) found that in the spring and sum

m e r o f 1 9 6 5 a n d 1 9 6 6 , e u p h a u s i i d s , m o s t lyThysanoessa spinifera, composed 57% of the biomassof whiting stomach contents. Fish, mostly deepsesmelts or Osmeridae spp., composed another 34% ostomach contents.

Gotshalls ( 1969a) study demonstrated con siderableseasonality in the diet of w hiting off northern California. Crustaceans, which are the major food in spring

Jackowski, E. 1980. Biological characteristics of Pacific whitingfrom Polish sur-veys of the west coast of the U.S.A. and Canada in 1979. Unpubl. manuscr., pre-sented at the U.S.-Poland bilateral meetings.1980.See footnote 5 on page 8 5 .

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY ANDFISHERYCalCOFI Rep., Vol. XXIII, 1982

I

M l S C INVERTEBRATESt

40 ,80

40 CRABY - -F I S H

801

a 4G

~

E U P H A U S I I D S

-1

R O N T H

Figure 9. The percentage (by volume) of different food types in the diet ofPacific whiting by month (data from Gotshall 1969a).

and summer, decline in the diet in winter, and arereplaced by fish as the dominant food (Figure9). Inspring and summer an average of 50-60% of thestomach contents of whiting was ocean shrimp; how-ever, these results should be viewed conservativelybecause the sample size was small.

Larger whiting more frequently eat fish and lessfrequently eat euphausiids compared to smaller whit-ing (Figure 10). Larger whiting also appear to con-sistently eat more shrimp than smaller whiting (Fig-ure 11).

The question of whether whitings feeding on ocean

1

.60

>0

. 4 03

01

wcc

U

. 2 0

0

4 2 - 5 1 5 2 - 6 1 6 2 - 7 1

L E N G T H (CM)

113

r 010

t

v)\a

Icn

5

/ A -I O -# 2 0 - 3 0 - 4 0 - 5 0 - 6 0 - 7 0 -

1 9 6 4

1 9 6 5

0 1 9 6 6

19 2 9 3 9 49 5 9 6 9 8 9

L E N G T H

Figure 11 . The number of ocean shrimp per stomach of Pacific whiting offVancouver Island (data from Gotshall 196 9b).

shrimp is a significant factor in sh rimp abundance hasprovoked some co ntroversy. C atches of shrimp off theOregon-Washington coast have increased significantlysince the late 1960s, and this increase appears corre-

lated to the harvest of whiting(Figure 12). It has beenhypothesized that removing large whiting by fishinghas reduced predation pressure on the shrim p popula-tion. This same trend has occurred off the Californiacoast. However, other factors, such as increasingfishing effort or normal chan ges in ab undan ce, cannotbe ruled out as responsible for the increase in shrimpcatches, and the question of a whiting-shrimp interac-tion deserves more rigorous examination. Francis(1982) briefly addresses this issue.

I

g 6 0 1

80

rc

Figure 10 . Freque ncy of occurrence of prey types in different Pacific whitingsize classes off Vancouver Island (data from Outram and Haegele 1972).

Figure 12. Shrimp catches off the Oregon-Washington coast and catches OfPacific whiting.

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TABLE 9Distribution of Pacific Whiting Biomass by INPFC Area from Three Northwest and Alaska Fisheries Center Surveys

Year

Montereyand

Totalource Vancouver Columbia Eureka Conception

Metric tons1975* Midwater 3,791 165,941 25,596 42,020 237,348

Bonom 667 189,630 7,222 10,107 207,626Percentage 2 70 11 18

91 3 5ercentage -

Percentage 1 80 7 12



Percentage 29 29 31 11Midwater 322,335 260,476 182,783 578,841 1,344,435




Total 4,458 355,571 32,818 52,127 444,974

1977 Midwater 343,821 316,440 360,944 108,087 1,129,292

Bottom 6,560 32,917 9,501 20,662 69,640

Total 350,381 349,357 370,445 128,749 1,198,932

Bottom 16,678 16,938 13,579 127,647 174,832

Total 339,013 277,404 196,362 706,488 1,519,267

1980

*1975 areas do not correspond to 1977 and 1980 survey areas

Competitors. Competitors with Pacific whiting forfood resources are numerous. Among competitivefishes are other Gadidae; flatfish, Pleuronectidae;soles, Bothidae; smelts, Osmeridae; Cottidae; Pacificherring; albacore, Thunnus a la lunga ; Hexagram-midae; lingcod, Ophiodon elongatus; Myctophidae;rockfish, Scorpaenidae; sablefish, Anoplopoma fim-bria; and Salmonidae. Numerous marine mammalsmay also be competitors, including the rough-tootheddolphin, Steno bredanensis; gray whale, Eschrichtiusrobustus; minke whale, Balaenoptera acutorostrata;Bryde's whale, B. edeni ; sei whale, B. borealis; finwhale, B. physa1us;blue whale, B . musculus; hump-back whale, Megapte ra novaeangl iae ; and rightwhale, Balaena glacialis (Fiscus 1979).

Predators. Predators of Pacific whiting reported inthe literature include the great white shark,Carcharo-don carcharias; soupfin shark, Galeorhinus zyop-terus; Pacific electric ray, Tetranarce californica;bonito, Sarda chiliensis; albacore; bluefin tuna,Thun-nus thynnus; rockfish; sablefish; lingcod; dogfish,S q u a l u s a c a n t h i a s ; a n d a r r o w t o o t h f l o u n d e r,Atheresthes stomias (Best 1963; Nelson and Larkins1970; Pinkas et al. 1971). Marine mammals that feedon whiting include the California sea lion,Zalophuscalifornianus; northern elephant seal, Mirounga an-gustirostris; Pacific whiteside dolphin, Lagenorhyn-chus obliquidens; killer whale, Oreinus orca; Dallporpoise, Phocoenoides dalli; sperm whale, Physeterm a c r o c e p h a l u s ; nor thern sea l ion , E u m e t o p i a sjubatus; and northern fur seal, Callorhinus ursinus(Fiscus 1979).

Bailey and Ainley (1982) analyzed otoliths col-

lected from California sea lion scats at the FarallonIslands for 4 yrs, 1974-78, and describe the seasonaland annual dynamics of sea lion feeding on Pacificwhiting. Sea lions fed most heavily on whiting,primarily juveniles, in spring and summer and mayconsume about 185 thousand tons each year.

POPULATION DYNAMICS

Size of Stocks

The abund ance of the Pacific whiting stock has beenassessed from trawl-hydroacoustic surveys. In 1980the abundance of whiting from central California tosouthern Vancouver Island over the continental shelfwas estimated by scientists of the Northwest andAlaska Fisheries Center to be 1.52 million metric tons(MT). Most of th is b iomass was composed ofjuveniles off the coast of central California. Fromsimilar surveys in 1975 and 1977, the stock biomasswas estimated at 0.44 million and 1.20 million MT(Table 9 ) . Based on earlier surveys by the U . S .Bureau of Commercial Fisheries, Alverson (cited inTillman 1968) calculated about 0 .68 million MT of

whiting. Estimates of whiting abundance based onhydroacoustic methods (Kramer and Sm ith1970; Darket al. 1980), however, have limitations. Critical prob-lems include (1 ) the difficulty in calibrating targetstrength, (2) the failure to identify species by acousticsignals, and (3 ) the detection of whiting near thebottom (Thorne'O). Regardless of these problems

"'Thome, R.E. Assessment of population abundance by echo integration. SCOR,Working Group No. 52 . Symposium on assessment of micronekton, April 27-30,1980.

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whiting offer one of the more optimum circumstancesfor hydroacoustic assessment compared with manyother species.

Soviet scientists have determined that the averagebiomass of whiting from 1967-73 was 1.3 6 million

M T (Efimov", Ermakov and Kharchenko12, Volog-din"). They estimated 1.4 0 and 1.86 million MT ofwhiting in 1974 and 1975, respectively. The Sovietsconducted two surveys in 1979 with resulting esti-mates of 1.20 and 2.88 million MT.

Estimates of spawning biomass of whiting deter-mined from egg and larval surveys are considerablyhigher than those stated above. Ahlstrom (1968) cal-culated that the spawning biomass of whiting wasl . 8to 3 .6 million M T. StepanenkoI4 estimated that thespawning biomass of whiting was 2.4 million MT in1977 and 2.65 million MT in 1979.

Estimates of spawning biomass from egg and larvalsurveys are extremely crude in the case of whitingbecause: the size composition and fecundity of thespawners is relatively unk nown; the stage duration ofeggs and larvae was not used for these approxima-tions; fecundity schedules of adults are based on verylittle data; and it is unknown w hether whiting are mul-tiple spawners. Estimates are further confounded bythe extreme patchiness of eggs and larvae. In spite ofthese problems, ichthyoplankton surveysare useful forassessing the relative abundance of the stock, and theCalifornia Cooperative Oceanic Fisheries Investiga-tions (CalCOFI) ichthyoplankton surveys conductedsince 1950 have been useful in monitoring changes inthe spawning potential of the population. The spawn-ing stock appears to have decreased in the late 1960sand early 1970s compared with earlier years, but hasrecently increased to previous levels (Stauffer andSmith 1977).

RecruitmentBecause of the spatial distribution of age classes,

recruitment of the exploited stock occurs at 3-6 yearsof age depending on the location of fishing. Inter-annual variations in recruitment are great, as exempli-fied by the dominance of the age composition of thestock by strong year classes for several consecutiveyears (Figure 13).

The factors most often considered to affect repro-ductive success of marine fishes are cannibalism , food

"Efimov, Y. N . 1974. The size of stocks and status of fishery of Pacific hake.Unpubl. manuscr. Pacific Scientific Research Institute of Marine Fisheries andOceanography (TINRO), Vladivostok, USSR .

I2See footnote 5 on p g e 8 5.

"Vologdin, V. 1980. Results of the hydroacoustic surveys with trawlings off thePacific coast of North America in 1979. Unpubl. man uscr. Pacific Scientifi c ResearchInstitute of Marine Fisheries and Oceanography (TINRO), Vladivostok, USSR.I4See footnotes 2 and 3 on p g e 8 2.

100

50

0.-c

E 100

1966

1 9 6 1

1977

1968

1 9 6 1

1978

1 9 7 0

1 9 7 3 1 9 7 0

0

1 3 5 7 9 11 1 3 5 7 9 1 1

Age ( y r lFigure 13. Age compositions of Pacific whiting caught off Oregon and

Washington from research surveys (1966 and 1968) and from U.S. observerfishery data (1977 and 1978) (from Bailey 1981a.b).

supply, predation, and larval transport. Although can-nibalism is sometimes observed, it is probably fairlylow because the majority of adult whiting spend alimited time in the spawning area (1-3 mo). However,Sumida and Moser (1980) found that some large lar-vae eat smaller larvae, and there are a few reports ofadult predation on juveniles.

Bailey (in press) found that the food requirement ofwhiting larvae is low because of relatively low growthand metabolic rates. The large mouth size of larvaeenables first-feeding larvae to ingest a wide spectrumof food part icle s, including juve nile and adultcopepods (Sumida and Mo ser 1 980). Bailey (in press)calculated that a first-feeding whiting larva can satisfygrowth and metabolic requirements by ingesting 31copepod nauplii, 6 small calanoid adult copepods, or0 .6 Culunus copepodites per day. By comparison, afirst-feeding northern anchovy larva, with its smallmouth, must capture at least 200Gymnodinium cellsper day to satisfy metabolic (excluding growth) re-quirements alone (Hunter 1977). It was concluded that

starvation from first-feeding failure is probably not asvariable for whiting larvae as it appears to be fornorthern anchovy and that whiting may not be as de-pendent on finding patches of prey as are northernanchovy (Lasker 1975).

Predation on eggs and larvae is a difficult problemto assess and is poorly understood. A wide variety ofinvertebrate organisms are capable of feeding onwhiting eggs and larvae. Yolk-sac stages are mostvulnerable to predation by invertebrates (Bailey andYen, in press). Predation by invertebrates may be

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BAILEY ET A L.: PACIFIC WH ITING LIFE HISTORY AND FISHERYCalCOFI Rep., Vol. XXIII, 1982

20

Y = 34.56 + 1.66X R = .70; P = ,001)

- +i

t+

+

+

important in cold years when development is slowthrough the stages most vulnerable to predation.

Oceanographic conditions appear to play a majorrole in the recruitment of Pacific whiting (Bailey 1981a,b). The offshore distance of larvae is apparentlypositively correlated to indices of wind-driven Ekmantransport (Figure 1 4). Although there is a good deal ofvariability in this relationship, it is statistically sig-nificant and indicates that larvae may be transportedoffshore in years of high npw elling. Since the juvenilenursery is inshore over the continental shelf, advection

2 . 5

x

; .0z-cocn

'=1 . 5

Y = 1,449 0,020X R = -0.74; < 0.001)

a 1961

a

I A

0 . 5 L---30 -20 -10 0 30 20 30

U P W E L L I N GI N D E X

Figure 15. Log of th e year-class index against t he January upwelling index(from Bailey 1 981a ,b).

of larvae offshore is expected to be detrimental tosurvival. In fact, Ekman transport during the spawningmonths is negatively correlated to year-class strength(Figure 15). Further work must be done on the sur-vival of larvae swept offshore to test this hypothesis.

Temperature may also influence recruitment, possi-bly by the predation-temperature interactions notedabove and the previously described influence of temp -erature on the location of spawning. The averagewinter temperature and Ekman transport in a multipleregression model account for 68% of the observedvariation in an index of year-class strength (Bailey1981 a,b). There is no apparent relationship betweenspawning biomass of the population and recruitment.

MortalityEstimates of annual instantaneous n atural mortality

rates range w idely. These estim ates, as well as several

estimates for fishing and total mortality rates are pre-sented in Table 10. A cohort analysis performed byFrancis (1982 ) on the 1973-80 catch-by-age data givesestimates of age-specific fishery mortality (catcha-bility) as well as recruitment of the exploited stock atage 3.

TABLE 10Estimates of Annual Instantaneous Mortality Rates

of Pacific Whiting

Investigators Males Females Both Sexes

M : natural mortality

Tillman(1968)

Nelson and Larkins (1970)Efimov (1974)'PFMC2Jackowski (1980)3Ehrich, et al. (1980)Low (1978)4Francis (in prep.)

F: fishing mortalityEfimov ( 1974)'Ehrich, et al. (1980)Z: total mortality

Efimov ( 1974)lEhrich et al. (1980)

0.72 0.62 x=0.67OS60.3.5

0.300.560.50

0.19-0.86(variable

age-specificnatural

mortality)

0.30-0.60

0.300.67

0.651.23

'Efimov Y. N . 1974. The size of stocks and status of fishery of Pacifichake. Unpubl. manuscr. Pacific Scientific Research Institute of MarineFisheries and Oceanography (TINRO), Vladivostok, USSR.*Pacific Fishery Management Council. 1980. Pacific coast groundfishplan. Draft report. Pacific Fishery Management Council,526 S . W. MillSt., Portland, OR 97201,3Jackowski, E. 1980. Biological characteristics of Pacific whiting fromPolish surveys of the west coast of the U.S.A. and Canada in 1979.Unpubl. manuscr., presented at the U.S.-Poland bilateral meetings,1980.4Low, L.L. 1978. Hake natural mortality and yield potential. Unpubl.manuscr. Northwest and Alaska Fish. Cent. Natl. Mar. Fish. ServNOAA, 272.5 Montlake Blvd. E . , Seattle, WA 98112.

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Dynamics of the PopulationOver the past 200 years the Pacific whiting popula-

tion has experienced some major changes in abun-dance (Soutar and Isaacs 1974).Based on an analysisof fish scales depo sited in sed imen ts, at the turn of the

last century the population was almost an order ofmagnitude larger than recent abundance levels. Thesechanges in abundance have been correlated to changesin abundance of the northern anchovy (Soutar andIsaacs 1974) and are inversely correlated to offshoreEkman transport (Bailey 1981a,b).

Several mathematical models have been constructedthat simulate changes in the whiting population. Thes einclude models by Francis (1 98 2), Francis e t al.(1982), Bernard (Oregon State University, Newport,OR), Stevens and Goodman (Scripps Institution ofOceanography, La Jolla, CA), Tillman (1968), andRiffenburgh (1969).

THE P ACIFIC WHITING FISHERY

Historical Catches and EffortPacific whiting has been the target of a large foreign

fishery off the west coast of the United States andCanada (Table 11). A Soviet fishery for whiting beganin 19 66 with a catch of 137 thousand MT . From1973-76 Poland, West Germany, East Germany, andBulgaria joined fishing operations for Pacific whiting.Reported catches peaked in 1976 at 237 thousand M T.The average annual all-nation reported catch from1966 to 1980 was 162 thousand MT . (These catches

were compiled from data at the Northwest and AlaskaFisheries Center.)A small domestic fishery for whiting, used in the

manufacture of pet food, has existed since at least

TABLE 11Annual All-Nation Catches of Pacific Whiting (x lo 3 MT) in US .

and Canadian* Waters.

Domestic/Year U.S.S .R. Poland ioint venture Other Total

- 137.0966 137.0- 206.1967 206.1- 103.8968 103.8

1969 161.8 - - 0.12 161.91970 226.2 - - 2 .3 228.51971 151.8 - - 1.4 153.21972 150.8 - - 0.4 151.21973 143.8 2 .0 - 5.1 150.81974 173.7 44.3 - 8 .4 226.51975 155.4 57.2 - 5 .1 217.71976 158.0 25.7 - 53.0 236.81977 111.0 19.5 - 1.9 132.41978 70.9 27.3 2.7 3.4 104.2I979 96.8 22.3 13.1 3.6 135.91980 0.1 49.0 40.8 0 .8 90 .7

*Zyblut, E. 1981. Dept. of Fisheries and Oceans, Govt. of Canada, Van-couver, B.C. Personal communication.

- -

- -

- -

1879 (Jow 1973). This fishery has been rather insig-nificant, with catches in the range of 200-500 MT/yr.However, in recent years the domestic fishery has be-come important: U.S.-foreign joint-venture fishingcaught 9 thousand MT and 28 thousand MT in 1979

and 1980, respectively.Historical effort statistics for the fisher y, excludingCanadian waters, were calculated from weekly aerialsurveillance data from the NMFS Enforcement Divi-sion (supplied by Bill Dickenson, NMFS, NorthwestRegional Office, Seattle, WA). Effort for two classesof vessels-large Soviet BM RT stem trawlers andsmaller Soviet SRT side trawlers (see TechnicalAs-pects below)-were calculated in vessel-days on thefishing grounds. Effort by the SRT trawlers wasgreatest in 1966 and declined steadily (Table 12).Effort by the BMRT trawlers was greatest in 1975and 1976.

To obtain a rough estimate of overall catch per unitof effort (CPUE) for the foreign fishery inU.S. wat-ers, SRT effort was converted to effective B MRT ef-fo r t by a s suming a r e l a t i ve f i sh ing power o fP ~ R T 0 .31 from the ratio of average horsepower ofSRT vessels to BMRT vessels (1150 HP).

Catchhtandard BM RT day indicates that the highestrates occured in 1967 and from 1977 to 1980. Sincethe latter period coincides cons picuously with passageof the Magnuson Fishery Conservation ManagementAct of 1976 (MFCM A) and the onset of intense ob-server coverage, these statistics indicate that actualcatches were possibly underreported from 1968 to1976.

TABLE 12Historcial Effort Statistics for the U.S.S.R.-Poland Foreign

Pacific Whiting Fishery (Solely) in U.S. Waters~ ~ ~~

StandardBMRT

BMRT RST days Catch CPLEYear vessel days vessel days Pqr=O 31 (1000 MT) (MTIBMRTday)

1966 2,670 14,490 7,128 137.0 19.21967 2,730 10,350 5,915 195.1 33.01968 5,677 2,079 6,317 68.0 10.81969 5,607 1,589 6,096 109.0 17.91970 7,847 658 8,049 200.8 24.9

1971 7,245 65 1 7,445 146.7 19.71972 5,131 518 5,290 111.3 21 .01973 5,904 - 5,904 141.1 23.91974 7,717 - 7,717 201.1 26.11975 10,401 - 10,401 196.9 18.91976 6,917 - 6,917 177.8 25.71977 4,076 - 4,076 127.2 31.21978 2,779 - 2,779 96.9 34.91979 4,452 - 4,452 114.9 25.81980 1,553 - 1,553 44.0 28.3

Assumptions - P s ~ = 0 . 3 1

CPUE = catch per unit effortPBMRT(Poland)=.OO

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BAILEY ET AL.: PACIFIC WHITING LIFE HISTORY AN D FISHERYCalCOFI Rep., Vol. XXIII, 1982

Technical AspectsAs the major country fishing for whiting, the Soviet

Union has improved its whiting fleet considerably. In1966 the fleet was mainly medium-sized side trawlers(SRTs) of about 500 gross tons. The proportion oflarge stern trawlers with freezing capacity (BMRTs)has gradually increased to replace the side trawlers.The typical BMRT is 3170 gross tons, has a crew of22-26, and uses a midwater trawl with a headropelength of 97 m . The daily production capacity is30-50MT of frozen fish and 20-35 MT of meal and oil.Support vessels in the fishery include factory ships,refrigerated transports, oil tankers, personnel carriers,tugs, and patrols.

The Soviet fishery is a well-coordinated expedition,and acoustics are used to guide the net over fish con-centrations. Prior to 1976, about 100 BMRTs wouldtypically participate in the fishery (Pruter 1976), bu t

lately the fleet has been reduced to ab out39 large sterntrawlers. In early years of the fishery most whitingwere filleted, and sm all fish were reduced to meal.Re-cently the average size of hake has become considera-bly smaller, and an increasing proportion of the catchis frozen whole.

The foreign fishery is closely tied to the migratorymovements of the whiting population. Historically,the fishery began in waters off Oregon in April andmoved northward as schools made their way up thecoast in summer. This was documented from aerialsightings of the Soviet fishery (Figure 16). In au-tumn, as fishing activity halted, whiting began tomigrate offshore and southward for spawning. Morerecently, fishing has been restricted by treaty to theperiod from June until October. Based on aerial sur-veillance records and Ermakovs (1974) analysis ofthe fishery, rich fishing grounds appear to be as-sociated with prominent geographical sites such asbanks, sh arp curves in the continental slope, andcanyons. Especially productive grounds are foundnear the Heceta Banks, Yaquina Head, Cape Flattery,Cape Blanco, and Destruction Island. Most fish arecaught in depths of 100-199 m (Table 13).

ManagementPrior to implementation of the MFCMA in 1977,

the foreign fishery was managed by bilateral agree-ment. Since 1977 management has been directed by aPreliminary M anagement P lan (PM P)IS for groundfishprepared by the Department of Commerce. Sub-sequently, the Pacific Fishery Management Councilhas prepared a fisheries management plan (FMP) forgroundfish, including whiting, which is currentlysPacific Fishery Management Council. 1980. Pacific coast groundfish plan. Draftreport. Pacific Fishery Management Council, 526 S . W. Mill St . , Portland, OR97201.

TABLE 13Catch (Percentage) by Depth Strata of Pacific Whiting Taken by

Foreign Trawlers in 1979

Depth (m) 0-99 100-199 200-299 300-399 400-499 >500

Percentaee 15.7 47 .7 2 6 . 2 6 . 9 2 . 3 1 . 2

From: French, R . , R. Nelson Jr., and J . Wall. 1980. Observations offoreign and joint venture fishing fleets off the coast of Washington, Ore-gon, and California, 1979. Unpubl. rep. Northwest and Alaska Fish.Cent., Natl. Mar. ish. Sew., NOAA, 2725 Montlake Blvd. E . , Seattle,WA 981 12.

under review. A conservative estimate of maximumsustained yield in the plan is 175.5 thousand M T. TheFMP specifies geographic and seasonal restrictionsmesh size, incidental catch levels, and an optimayield (in the form of quotas). Under the MFC MA o nlthe Soviets and Poles have been granted licenses as thmajor foreign interests that may fish for Pacific whiting. Recently. U.s. fishermen have become involvedin the whiting fishery through joint ventures in whicU.S . trawlers harvest whiting for delivery to foreigprocessing vessels.

Francis et al. ( 1982) present a managemen t analysiof the Pacific whiting fishery in which a policy algorithm is developed that aims to use strong year classes in a practical and efficient manner w hile protectinthe stock when it is in poor condition and environmental conditions do not appear conducive to immediate improvement.

Effects of the Fishery on the PopulationCom mercial fisheries may affect the abundance an

recruitment of marine fish populations in severaways. Besides reducing the total spawning biomass othe population, removing a stocks largest and oldesfish also ( 1 ) lowers the quality of the spawning product if offspring from sm aller fish are less fit (Hempe1979); (2 ) reduces the num ber of age classes that contribute to spawning; thus the maintenance of healthlevels of spawning stock depends on successful re

15 0-

n

0

4 5 6 7 8 9 1 0 1 1 1 2

M O N T H

Figure 16. The average monthly number of foreign vessels fishing Pacificwhiting sighted in aerial surveys, 1967-72 (squares) and the average per-centage of the catch in 3-m0 periods for the same years.

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17/18


cruitment from fewer age classes (Smith 1978); and(3) changes the distribution of spawning if the popula-tion stratifies by size or age on the spaw ning ground.

The spawning potential of the whiting populationhas had no discernible effect on recruitment from

1960-75 (Bailey 198 1a,b ), partly because of theoverwhelming effects of environmental factors. Forexample, the strong 1961 year class arose from anextremely low spawning stock, but under favorableenvironmental conditions it became a very strong yearclass. Similar situations gave rise to the strong 1970and 1973 year classes.

The long life ofMerluccius sp p. , as well as of othergadids, is probably an adaptation to stabilize the stockfrom the effects of extreme recruitment variability,and reduction in the number of spawning age classesby heavy fishing must be a destabilizing influence. Ina population with few er age classes, the probability ofa stock collapse would increase if recruitment failureoccurred in a succession of years. This type of interac-tion appears to have influenced the recruitment ofother stocks. In an analysis of the population dynamicsof the Pacific sardine, Sardinops sagax, Murphy(1968) concluded that after the number of spawningage classes was reduced by fishing, several years ofrecruitment failure caused catastrophic population de-clines.

Since the mid-l960s, a change in the spawninggrounds of Pacific whiting has occurred. Larvae havebecome much less abundant off Baja California andmore abundant off central California compared withearlier years (Bailey 1980). In addition, the depositionof scales from young whiting markedly declined offBaja California from 1965-69 compared with earlierprefishing periods (Soutar and Isaacs 1974). Smith(1975) first suggested that this change was related tothe beginning of an intensive fishery for adults in1966. He suggested that large adults spawn farthersouth and that harvesting this component of the pop u-lation has caused the spawning decrease in the south-ern end of the range. Further analysis supports an in-teraction between the spawning distribution and thefishery (Bailey 1980, 1981a,b). Although the spawn-

ing location of whiting is related to temperature, the

lo a-c

C

80 .a

E

-(0._

60.

3

A 1951-66 Y = 0,23X - 4.80 ( R = .63; P < ,01)1967-75 Y = 0.1OX - 1 . 4 2 (R = ,84; P < O 1 )

3

C

E

0,

g 40 -

L

t-4

d

O L21 22 23 24 25

Sea surface temperature("C)Figure 17 . Regression s of the percentage of Pacific Whiting larvaeoffswthern

California comp ared to Baja California against the m ean Janu ary-M arch seasurface temperatureoff Baja California for the pre- and po stfishing periods,1951-66 an d 1967-75.

R. Lasker reviewed earlier versions of the manuscriptand made helpful comments. We also appreciate theencouragement of W. Wooster and R. Marasco.

LITERATURE CITEDAhlstrom, E.H . 1959. The vertical distribution of fish eggs and larvae off

California and Baja California, Fish. B ull., U .S. 60: 107- 146.- 1968. An evaluation of the fishery resources available to Califor-

nia fishermen. In D. Gilbert (ed.), The futureof the fishing industry ofthe United States. Univ. Wash. Press, Seattle, p. 65-80.

Ahlstrom, E.H., and R.C. Counts. 1955. Eggs and larvaeof the Pacifichake, Merluccius productus. Fish. Bull., U.S. 56:295-329.

Alton, M.S. 1972. Characteristics of the demersal fish faunas inhabitingthe outer continental shelf andslope off the northern Oregon coast.InA.T. Pruter and D.L. Alverson (eds.), The Columbia River estuary andadjacent ocean waters. Univ. Wash. Press, Seattle, p. 583-636.

Alton, M .S., and M . O . Nelson. 1970. Food of the Pacific hake,Merluc-ciusproductus, in Washington and northern Oregon coastal waters. U .S.Fish Wildl. Serv., Circ. 332:35-42.

Alverson, D.L., an d H.A. Larkins. 1969. Status of the knowledge of thePacific hake resource. Calif. Coop. Oceanic Fish. Invest. Rep.13:24-3 1.

Bailey, K.M. 1980. Recent changes in the distribution of hake larvae:causes and consequences. Calif. Coop. Oceanic Fish. Invest. Rep.21: 167-17 1.

recent change in the distribution of larvae is inde- - 1981a. An analysis of the spawning, early life history andre-pendent of-temperature changes. An analysis ofintercepts for pre- and post-spawning periods (Fig-

cruitment of the Pacific hake,Merluccius producrus. Ph.D. dissertation,Univ. Wash., Seattle.

- 1981b. Larval transport and the recruitment of Pacific hake,Merluccius productus. Mar. Ecol. 6 : 1-9.

covariance indicated significantly different slopes and

ure 17). - (in press). The early life history of Pacific hake, Merlucciusproductus. Fish. Bull., U.S.

Bailey, K . M . , and P. Ainley. 1982. The dynamics of California sea lionpredation on Pacific hake. Fisheries Research1:163- 176.

Bailey, K.M., and J . Yen (in press). Predation by a carnivorous marinecopepod, Euchuera elongaru Esterly, on eggs and larvae of the Pacifichake, Merluccius productu s. J . Plankton Res.

ACKNOWLEDGMENTSNumerous scientists at the and

and Southwest Fisheries Centers freely made dataavailable. T. Laevastu, R . Schwartzlose,T. Dark, and

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BAILEY ET AL.: PACIFIC W HITING LIFE HISTORY AN D FISHERYCalCOFI Rep., Vol. XXIII, 1982

Bakun, A . 1973. Coastal upwelling indices, west coast of North A merica,1946-7 . U.S. Dep. Commer., NOAA Tech. Rep. NMFS SSRF-671.

-. 1975. Daily and weekly upwelling indices, west coast of NorthAmerica, 1967-73. U.S. Dep. Commer., NOAA Tech. Rept. SSRF-693.

Best, E. A. 1963. Contribution to the biology of the Pacific hake,Merluc-cius productus. Calif. Coop. Oceanic Fish. Invest. Rep. 9:51-56.

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

Dark, T.A ., M. O. Nelson, J. Traynor, and E. Nunnallee. 1980. Thedistribution, abundance, and biological characteristics of Pacific whit-ing, Merluccius productus, in the California-British Columbia regionduring July-September 1977. Mar. Fish. Rev. 42(3-4):17-33.

Erich, S . , F. Mombeck, and G . Speiser. 1980. Investigations on thePacific hake stock (Merluccius productus) in the Northeast Pacific.Arch. Fishereiwiss 30:17-38.

Ermakov, Y.K. 1974. The biology and fishery of Pacific hake,Merlucciusproductus. Ph.D. dissertation, Pac. Sci. Inst. Mar. Fish. Oceanogr.(TINRO), Vladivostok, USSR (in Russian).

Fiscus, C. 1979. Interactions of marine mammals and Pacific hake. Mar.Fish. Rev. 41(10):1-9.

Foucher, R .P ., and R.J. Beamish. 1977. A review of oocyte development

in fishes with special reference to Pacific hake(Merluccius productus)Can. Fish. Mar. Serv. Tech. Rep. No. 755.

Francis, R.C. 1982. On the population and trophic dynamics of Pacificwhiting. U.S. Dep. Commer., Natl. Oceanic Atmos. Admin., Natl.Mar. Fish. Ser ., Northwest and Alaska Fish. Cent. , Seattle, Wash.,Processed Rep. 82-07, 68 p.

Francis, R .C., G.L . Swartzman, W.M . G etz, R. Haar, andK. Rose. 1982.A management analysis of the Pacific whiting fishery. U.S. Dep. Com-mer., Natl. Oceanic Atmos. Admin., Natl. Mar. Fish. Ser., Northwestand Alaska Fish. Cent., Seattle, Wash., Processed Rep. 82-06, 48 p.

Frey, H.W. 1971. Pacific hake. In H.W. Frey (ed.), Californias livingmarine resources and their utilization, p. 71-74. Calif. State Dep. FishGame. 148 p.

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