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

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WOLF AND SMITH: MAGNITUDE OF SARDINE SPAWNING BIOMASSCalCOFI Rep., Vol. XXVII. 198626120-16-10-6-z 20'W2) 1 6 -0WLL10-6-II19831984N : 881N : 245ae I I 1120 140 180 180 200 220 240 200261610-6-1985N : 5 88I I120 140 180 180 200 220 240 280STANDARD LENGTH (MM)Figure 3 Catch length frequencies of sardines landed incidentally withmackerel in 1983, 1984, and 1985 Mean weights of modal length classesforeach year are 1983, 130 g. 205-209 mm SL, 1984, 147 g. 210-214 mm SL,1985,143 g, 205-209 mm SLstantial portion of sardine spawning in recent years hasoccurred relatively near to shore (within the 75-m contour)and during summer and fall.Although the limited interpretation of the 1985 surveyis conclusive in the original objectives relative to20,000-ton spawning biomass, we resist broadeningthese few results for a biomass estimate or fisheryquota. The spawning area of 670 n.mi.* is nearly identicalto the 500 n.mi.* criterion adopted for this tech-nique. This means that any deviation from the assumedadult parameters could change the evaluation. Anothercritical feature is that we can estimate only the standingcrop of eggs from this small set, not the egg production.The two unevaluated factors are mortality rate ofthe eggs and the precision of the intercept estimate. Futuresurveys must quantify the mortality rate and thefrequency distribution of eggs.The estimated mean of positive samples in the 1985survey is high relative to samples of the 1930s to 1950s(Table 2). It appears that the high value is due to thechance encounter of more observations with highvalues. We believe the cause of this difference istechnical rather than biological, although this cannotbe determined from these few samples. It is importantto note that all the other distributions result fromoblique or horizontal tows and that the new results arefrom a vertical tow. The scale of the integration is 25cm for the CalVET net and on the order of meters for allbut one of the other nets, and kilometers for the highspeednet used in 1950. The smaller CalVET net willhave a greater probability of sampling zero eggs. Also,the sampling threshold of the CalVET net (1 egg in aCalVET is equivalent to 50 eggs in a 1 -m oblique tow)might cause the lower end of the frequency distributionof egg densities to be undersampled. Both of thesecharacteristics would cause the mean observed densityof positive samples to be inflated. This would implythat the entire area of sardine spawning was notdetected and that 20,000 tons is a conservativeestimate.The high mean value could also result from a lowerthan normal mortality or higher than normal per capitaegg production rate, which would imply a lowerspawning biomass. These biological factors will allhave to be separately assessed for the absolute biomassto be estimated from egg production rates.Analogous data from the anchovy egg productionprocedure indicate the great importance of the adultsampling effort for biomass estimation. If the intervalbetween batches of eggs is long, for example 20 days,the ratio of gonads with evidence of spawning in theprevious day is only 5%. This ratio would requiremany independent samples to precisely determine thespawning fraction. Individual samples of anchovy femalesrange from 0% spawning to over 40% when themean is 15%. Thus the overall precision of spawningbiomass estimates may be determined by the ability toobtain a sufficient number of independent samples ofadult females.In summary, at least one more year of field andlaboratory work on additional egg samples and adultcollections will be required before the procedure for anabsolute biomass estimate can be designed.30
WOLF AND SMITH: MAGNITUDE OF SARDINE SPAWNING BIOMASSCalCOFI Rep., Vol. XXVII, 1986TABLE 2Pacific Sardine Egg Sample Frequency Distributions at Different Levels of Spawning BiomassaNet types and years#/IO m2CalVET CF&G 2-m 1 -m 0.5-m Hi-speed 1 -mx In(.x) 1985 1931-32 1941 1941 1950 1959.I25 -2.08 - b2 - - - -.5 -0.69 -4 - - - -2 0.69 -6 21- -288 2.08 - 7 22 8 -2832 3.47 - 14 16 15 -30128 4.85 4 12 31 29 77 23512 6.24 4 13 27 14 20 122,048 1.62 2 5 17 10 7 58,192 9.01 1 2 3 2 1 4Estimatedmean 1,564 544 569 619 406 410Biomass (MT)' 0.02 3.9 2.7 2.7 1 .0 0.2"(Smith and Richardson 1977)'Value below sampler threshold'(Murphy 1966)ACKNOWLEDGMENTSWe would like to acknowledge the editorial assistanceof two anonymous reviewers. Rocky French andTerry Palmisano helped with graphics. We thank thecrew of NOAA ship David Starr Jordan and her captain,M. Roll. J. Thrailkill of the National Marine FisheriesService (NMFS) was responsible for cruise logistics.The team of scientists participating on the surveyincluded W. Flerx, J. Metoyer, D. Abramenkoff ofNMFS; T. Dickerson of the California Departmentof Fish and Game; W. Bryan, S. Cummings, andC. Walker of Scripps Institution of Oceanography;E. Isidro of the University of Azores, Portugal; andS. Mildner and J. Mildner from Australia. DennisGruber and Evelyn Conley sorted the CalVET samplesand staged the sardine eggs. Betsy Stevens, ElaineSandknop, and Barbara Sumida MacCall providedassistance with egg staging. Celeste Santos Methotentered and edited the data. Rich Charter and CindyMeyer helped with data management.LITERATURE CITEDHatanaka, M. 1956. Biological studies on the population of the saury,Cololubis saira (Brevoort) Part I: reproduction and growth. Tohoku J.Agr. Res. V1(3):227-269.Hewitt, R.P. 1985. The 1984 spawning biomass of the northern anchovy.Calif. Coop. Oceanic Fish. Invest. Rep. 26:17-25.Hunter, J.R., and B. Macewicz. 1980. Sexual maturity, batch fecundity.spawning frequency, and temporal pattern of spawning for the northernanchovy, Engradis mordax, during the 1979 spawning season. Calif.Coop. Oceanic Fish. Invest. Rep. 21:139-149.Klingbeil, R.A. 1981. Status of the spawning biomass of the Pacific sardine,1980-81. Calif. Dept. Fish and Game, Mar. Resources Admin. Rep. No.81-1.6~.-. 1982. Status of the spawning biomass of the Pacific sardine, 1981-82. Calif. Dept. Fish and Game. Mar. Resources Admin. Rep. No. 81-2,7 P.-. 1983. Status of the spawning biomass of the Pacific sardine. 1982-83. Calif. Dept. Fish and Game. Mar. Resources Admin. Rep. No. 83- I ,5 P.Klingbeil, R.A., and P. Wolf. 1984. Status of the spawning biomass of thePacific sardine, 1983-84. Calif. Dept. Fish Game. Mar. ResourcesAdmin. Rep. No. 84-1, 7 p.MacCall, A.D. 1979. Population estimates for the waning years of thePacific sardine fishery. Calif. Coop. Oceanic Fish. Invest. Rep. 20:72-82.MacGregor. J.S. 1957. Fecundity of the Pacific sardine (Sardinopscuerulea). Fish. Bull. 121:427-449.Murphy, (3.1. 1966. Population biology of the Pacific sardine (Sardinopscaerulea). Proc. Cal. Acad. Sci. 34:l-84.Natrella, M.G. 1963. Experimental statistics. National Bureau of StandardsHandbook91, U.S. Supt. Doc.Parker, K. 1980. A direct method for estimating northern anchovy,Engraulis mordax, spawning biomass. Fish. Bull. 78541-544.Picquelle, S.J., and R.P. Hewitt. 1983. The northern anchovy spawningbiomass for the 1982-83 California fishing season. Calif. Coop. OceanicFish. Invest. Rep. 24:16-28.-. 1984. The 1983 spawning biomass of the northern anchovy. Calif.Coop. Oceanic Fish. Invest. Rep. 25: 16-27.Santander, H., P.E. Smith, and J. Alheit. 1982. Determination of samplingeffort required for estimating egg production of anchoveta (Engraulisringens) off Peru. Bol. Inst. Mar. Peru Callao 7:9- 18.Smith, P.E., S. de la Campa, and J.R. Thrailkill. 1976. Instituto National dePesca and CalCOFI statistical regional divisions for ichthyoplanktonsurveys. Southwest Fisheries Center Admin. Rep. LJ-36-31.Smith, P.E., and S.L. Richardson. 1977. Standard techniques for pelagicfish egg and larva surveys. FA0 Tech. Paper No. 175, 100 p.Wolf, P. 1985. Status of the spawning biomass of the Pacific sardine, 1984-85. Calif. Dept. Fish and Game. Mar. Resources Admin. Rep. No. 85-1,20 p.Wolf, P., and P.E. Smith. 1985. An inverse egg production method fordetermining the relative magnitude of Pacific sardine spawning biomassoff California. Calif. Coop. Oceanic Fish. Invest. Rep. 26:130-138.31
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 30 and 31: WOLF AND SMITH: MAGNITUDE OF SARDIN
Page 34 and 35: PUBLICATIONSCalCOFI Rep., Vol. XXVI
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