CalCOFI Reports, Vol. 27, 1986 - California Cooperative Oceanic ...

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BINDMAN: 1985 NORTHERN ANCHOVY SPAWNING BIOMASSCalCOFI Rep., Vol. XXVII, 198618rL2; = number of larvae caught at each stationin region 2, andAi = area represented by station i.The final biomass estimate for the survey area plus thenorthern area was 458,025 + 63,718 = 521,742 MT.The variance of this estimate was not computed. However,the coefficient of variation is certainly larger thanthe 19% associated with the entire region of the EPMsurvey (Table 2).PROPORTION FEMALE BY WEIGHTFigure 10. Frequency distribution of female fraction by weight.BIOMASS ESTIMATE AND VARIANCEUsing equations 1 and 2, I estimated the spawningbiomass for the portion of the population range coveredby the survey to be 458,025 MT, with a standard errorof 85,872 MT. This gives a coefficient of variation of18.75% The values of the parameters that were used inthe estimate, and their variances and covariancesappear in Tables 2 and 3. The northern part of thepopulation range was not covered by this survey.The results of the Mys Babushkina cruise show that,as in past years, there is spawning off San Francisco.The Soviet cruise covered the area from Point Conception(CalCOFI line 80.0) north to line 70.7-thenorthern extent of our biomass survey (region 2)-aswell as the region north of line 70.7 (region 1). TheSoviets used a bongo net to collect anchovy eggsand larvae. Because larvae are less patchy than eggs, Iused “scanned” larvae counts (Figure 3) as an indicatorof relative spawning biomass in the two regions. Specificfecundity and subsequent mortality rates ofeggs and larvae are assumed to be constant throughoutthe spawning area. The biomass of region 1 was calculatedas:B1 = B2*where B1 =B2 -Llj -2 (Ll; * Ai)C (L2; * A;)1= 63,718MTestimated spawning biomass of region1,29,090 MT is the spawning biomass ofregion 2 (biomass equation),number of larvae caught at each stationin region 1,DISCUSSIONThe 1985 egg production method estimate of thespawning biomass of the central subpopulation of thenorthern anchovy is up by 61% from its lowest point(since 1980) in 1984. Table 4 lists the historical time seriesof parameters. The change in spawning biomass iscaused by a 3 1 % increase in egg production and a 13%increase in the daily specific fecundity from 1984. Thedecrease in daily specific fecundity results from a dropin the spawning fraction to a level average for 1980-84and an increase in batch fecundity. The larger batch fecundityis strongly related to a 21 % increase in femaleweight, because the two are highly correlated (Table3). The ratio of batch fecundity and mean weight (FIW)estimates the specific batch fecundity (Table 4). The increasein this ratio is less than the rise in batch fecundity,implying that much of the growth in batch fecundityis due to a larger average female weight. The egg mortalityrate Z was higher this year than it has been since1980. The very large 1980 rate, along with this year’shigh Z value, demonstrates the variability of Z. Femalefraction remained very high compared to the yearsbefore 1984. The daily specific fecundity is lower than1984 but is still above the average for 1980-83.The EPM spawning biomass estimate can be comparedto an annual acoustic survey, which provided ameasure of total anchovy biomass. The California Departmentof Fish and Game conducted an acoustic andmidwater trawl survey of the northern anchovy in February1985 (Cruise Report 85-X-1 , K.F. Mais, CDFG,Long Beach, California). The cruise was restricted tothe area between Point Conception (CalCOFI Iine80.0) and the U.S.-Mexican fishery boundary. Inagreement with our results, Mais reports that the geographicdistribution of anchovies was more offshoreTABLE 3Covariances between Adult ParametersF S Female fraction (R)Female weight (W) 66.25495 0,00076 0.00064759Batch fecundity (F) 0.53235 0.44352668Spawning fraction (S) 0.0000553122
BINDMAN: 1985 NORTHERN ANCHOVY SPAWNING BIOMASSCalCOFI Rep., Vol. XXVII, 1986TABLE 4Time Series of Egg Production Parameters (1980-85)Daily egg production ( I 012 eggsiday)I980 1981 I982 1983 1984 1985“26.34 20.96 13.51 17.25 12.98 16.95Egg mortality rate0.450.140. I60.18 0.170.29Average female weight (g)17.4413.3718.8311.20 12.0214.50Batch fecundity (eggs)7,7518,32910,8455,297 5,4857,343Spawning fraction0. I420. I060.1200.094 0.1600.120Female fraction0.4780.5010.4720.549 0.5820.609Daily specific fecundity ( IO6 eggs/day/MT)30.2833.0332.5324.35 42.4337.00Specific batch fecundity (eggdg)444623576473 456506Spawning biomass (10’ MT)870635415652 309522’Coef. of variation for (B)0.260.220.060.21 0.170.19”Calif. Dept. Fish and Game498 493 233 46 1 479acoustic biomass estimateto to to to tof , nj MT)1 v I. - -, 598 59 1 247 504 560’Does not include San Francisco area’Includes San Francisco‘Does not include Mexican portion of anchovy population627to753‘and southward than in any other survey year. He alsoreported that the bulk of the population was “located inan arc of 80 miles west to south, and 30 miles east tosouth of San Clemente Island.” This is where oursurvey found the greatest density of anchovy eggs (Figure1). Mais calculated the total biomass of anchovies(not spawning biomass) to be 627,000-753,000 MT inU.S. waters off southern California. This is up 30.8%-34.5% from his results of 1984. He concludes thatthe 1985 estimate is the highest in five years andthat it would have been higher if the proportion of theanchovy population located in Mexican waters beenincluded.In previous years the survey area was divided intoregions in order to reduce the variance of the parametersand the variance of the biomass estimate (Picquelleand Hewitt 1983; Hewitt 1984). The regionalizationwas indicated because there were significantdifferences in one or more parameters betweenregions. There is no indication that regionalizationwould have reduced the variance of this year’sestimates.Anchovy eggs were found much farther offshorethan in any year since the egg production methodsurveys began in 1980. A large number of eggs far offshoremay have been missed by our survey. Asmentioned earlier, if a significant number were missed,there would be a downward bias in our biomass estimate.ACKNOWLEDGMENTSA. MacCall of the Southwest Fisheries Center(SWFC) coordinated this year’s biomass estimate. Wewould like to sincerely thank all those who took part inthis year’s project. J. Hunter, R. Lasker, G. Moser, andJ. Thrailkill of SWFC, and L. Farrar of SWFC and theNational Ocean Service directed the field collections,laboratory processing, and data analysis. The cruisewas conducted by the crew of NOAA ship David SturrJordan with its captain M. Roll. W. Flerx (SWFC) ledthe team of scientists participating on the cruise: theywere, from SWFC, D. Abramenkoff, D. Ambrose, P.Arenas, J. Butler, and E. Lynn; and, from Mexico, A.Cota, F. Diaz, I. Vomend, and G. Vueltiflor. Laboratoryprocessing of the samples was by L. Dunn, M.Farrell, J. Haddox, A. Lumpkins, and F. Pocinich ofScripps Institution of Oceanography (SIO), and by D.Ambrose, M. Busby, D. Gruber, E. Lynn, B.Macewicz, B. MacCall, P. Paloma, E. Sandknop, andE. Stevens of SWFC. N. Lo and P. Smith (SWFC)provided advice, and N. Lo’s program was used to assignages to the eggs. R. Ford (SWFC) entered the data,and R. Charter (SWFC) and Cindy Meyer (SWFC)produced the computer graphics. Roy Allen (SWFC)23
Page 1: REPORTSVOLUMECICTCIBERXXVll1986
Page 4 and 5: EDITOR Julie OlfeSPANISH EDITOR Pat
Page 7: COMMITTEE REPORTCalCOFI Rep., Vol.
Page 10 and 11: FISHERIES REVIEW: 1985CalCOFl Rep.,
Page 12 and 13: FISHERIES REVIEW: 1985CalCOFI Rep.,
Page 18 and 19: BINDMAN: 1985 NORTHERN ANCHOVY SPAW
Page 22 and 23: ~~ ~BINDMAN: 1985 NORTHERN ANCHOVY
Page 28 and 29: WOLF AND SMITH: MAGNITUDE OF SARDIN
Page 34 and 35: PUBLICATIONSCalCOFI Rep., Vol. XXVI
Page 37 and 38: Part I1SYMPOSIUM OF THE CALCOFI CON
Page 39 and 40: PETERSEN ET AL.: NEARSHORE HYDROGRA
Page 55 and 56: LAVENBERG ET AL.: SOUTHERN CALIFORN
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STEPHENS ET AL.: LARVAL FISH RECRUI
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Part 111SCIENTIFIC CONTRIBUTIONS
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ESPINO AND WOSNITZA-MENDO: PERUVIAN
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MacGREGOR: SEBASTES ABUNDANCECalCOF
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LLUCH-BELDA ET AL.: GULF OF CALIFOR
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DuracionQUINONEZ-VELAZQUEZ Y GOMEZ-
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FIEDLER: OFFSHORE ENTRAINMENT OF AN
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SCHMITT: SELECTIVITY AND FEEDING OF
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ARCOS AND FLEMINGER: CALANOID COPEP
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CHEN: VERTICAL DISTRIBUTION OF PELA
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CHEN: VERTlCAL DISTRIBUTlON OF PELA
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BRINTON ET AL.: GULF OF CALIFORNIA
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METHOT: FRAME TRAWLCalCOFI Rep., Vo
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-130' 125. 120' 11.5. 110.I I I I I
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