CalCOFI Reports, Vol. 30, 1989 - California Cooperative Oceanic ...
CalCOFI Reports, Vol. 30, 1989 - California Cooperative Oceanic ... CalCOFI Reports, Vol. 30, 1989 - California Cooperative Oceanic ...
LO AND METHOT: 1988 NORTHERN ANCHOVY SPAWNING BIOMASS CalCOFl Rep., Vol. 30,1989 1 08 5 0 6 I- E 04 87 - 1 m OBSERVED 0 ESTIMATED 084 n 87- 2 02 I I n I 0 0 1 2 3 07, , 0 5 , 0 1 2 3 4 06 05 6 03 04 04 02 02 01 01 n 0 0 1 2 3 4 AGE 0 1 2 3 AGE Figure 6. Observed and estimated age composition in 1987 for four periods: period 1, Jan.-Mar.; period 2, April and May; period 3, June and July; period 4, Aug.-Dec. (see table 3). In the assessment conducted last year with data through the winter of 1987 (Methot and Lo 1987) the 1986 year class was fixed at a high value because when unconstrained, the model assigned an even higher value to the 1986 year class. The same situation occurred in the current assessment, which used data through winter 1988. In this case we fixed the abundance of the 1987 year class at a high value, and estimated the 1986 year class to be somewhat lower than the assumed large 1987 year class. Consequently, the revised estimate of the spawning biomass in 1987 declined when the additional year of data was included. This revised estimate of the 1987 spawning biomass, 880,000 MT, is nearly identical to the alternative estimate, 840,000 MT, made by Methot and Lo (1987) under the assumption that availability to the fourth-period Mexican fishery has been 1.0 since 1983. The abundance of age 0 fish is difficult to assess because it is affected by two factors: the absolute abundance of age 0 fish in the population and the availability of these fish to the Mexican fishery. The availability ofjuvenile anchovy to the Mexican fishery is a critical parameter in the SS model. The abundance of juveniles relative to older fish in this fishery fluctuates because of year-to-year changes in the true relative abundance of these new recruits, and because of changes in their availability to the fishery. In the model, temporal changes in agespecific availability were assumed to be a function of long-term temperature trends, deviations from this trend, and deviation in weight at age. Estimated availability of these young fish to the Mexican fishery was very high during, and immediately following, the 1982-83 El Niiio (table 8). Consequently, high incidence of young fish during this period is partially explained by their increased availability to the fishery. In the fourth periods of 1985,1986, and perhaps 1987, the model predicts somewhat lower availability, while the abundance of age 0 fish stayed high. Thus the model indicates that the recruits of these three year classes were very abundant. We 30
~~~ ~ ~~ ~~ ~ ~~ ~ ~ ~- ~ ~~ ~ ~ - ~ -~ ~ ~ LO AND METHOT: 1988 NORTHERN ANCHOVY SPAWNING BIOMASS CalCOFl Rep., Vol. 30,1989 Year class -- 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 - TABLE 8 Recruitment to the Fishery at Ensenada, Mexico ~ Age 0 Period 3 -~ Period 4 0 E AV -. 0 E AV ,017 ,011 ,004 ,122 ,026 ,032 ,233 ,091 ,053 ,666 ,451 ,468 ,039 ,041 ,007 .194 ,198 ,205 ,100 ,152 .017 ,732 ,690 ,194 .046 ,146 ,013 ,365 .420 ,162 ,008 ,065 ,008 ,350 ,204 ,048 .060 ,103 ,039 ,251 ,231 ,160 ,045 ,159 ,015 ,481 ,632 ,215 ,104 ,111 ,015 .480 ,362 ,376 ,274 .213 ,043 ,730 ,755 ,714 - - - .702 ,530 ,725 ,091 ,171 ,028 ,672 ,544 .230 ,414 ,153 ,027 ,478 ,473 ,234 Age 1 Period 1 Period 2 ~_____ 0 E Av 0 E - - - 070 256 313 576 633 337 368 - - - - - - - - 652 692 - - - 502 447 - - - 576 488 - - - 110 338 587 767 384 899 873 - - - 631 656 - - - 457 592 - - - 701 708 914 722 ,549 767 ,824 Note: Age 0 anchovy are partially recruited to this fishery in the third period of the year. They typically are fully recruited in the second period of the following year. The symbols indicate the observed ratio of recruits to total numbers in the Mexican fishery (0), the ratio expected by the model (E), and the estimated, environmentally sensitive availability used by the model (Av). Av 1.00 ,211 - ,235 ,269 ,349 ,260 1.00 1 .oo ,326 1.00 1.00 intend to reexamine the submodel that predicts availability from environmental deviations, but it seems unlikely that the generally good fit apparent in table 8 can be substantially improved. ACKNOWLEDGMENTS We thank all those who contributed to the spawning biomass estimate, in particular W. Garcia F. of CRIP, INP, Mexico, for providing the agecomposition data of the Mexican fishery at Ensenada through the MEXUS-PACIFIC0 program; the individuals who collected, sorted, staged, and processed the plankton samples from the January 1988 CalCOFI cruise; all crew members of the NOAA ship David Starr Jordan; John Hunter for reading the manuscript; and two reviewers for their critiques. LITERATURE CITED Bindman, A. G. 1985. The 1985 spawning biomass of the northern anchovy. NMFS SWFC Admin. Rept. LJ-85-21,21 pp. Lasker, R., ed. 1985. An egg production method for estimating spawning biomass of pelagic fish application to the northern anchovy (Engradis mordax). U.S. Dep. Commer. NOAA Tech. Rep. NMFS 36, 99 pp. Lo, N. C. H. 1985. Egg production of the central stock of northern anchovy, Engraulis mordax, 1951-82. Fish. Bull., U. S. 83:137-150. MacCall, A. D. 1974. The mortality rate ofEngraulis mordax in southern California. Calif. Coop. Oceanic Fish. Invest. Rep. 17:131-135. Mais, K. F. 1974. Pelagic fish surveys in the California Current. Calif. Dep. Fish Game Fish. Bull. 162.79 pp. Methot, R. D. 1986. Synthetic estimates of historical abundance and mortality for northern anchovy, Engraulis mordax. NMFS SWFC Admin. Rep. LJ-86-29,85 pp. -. In press. Synthetic estimates of historical abundance and mortality for northern anchovy. In Mathematical analysis of fish stock dynamics, E. Vetter and B. Megrey, eds. Methot, R. D., and N. C. H. Lo. 1987. Spawning biomass of the northern anchovy in 1987. NMFS SWFC Admin. Rep. LJ-87-14,46 PP. PFMC. Pacific Fishery Management Council. 1983. Northern anchovy fishery management plan. PFMC, Metro Center, 2000 SW First Ave., Portland, OR 97201. Secretaria de pesca de Mexico. 1988. Boletin anual temporada 1987, centro regional de investigacibn pesquera, ediado en coordinacibn con la cimara nacional de la industria pesquera delegacibn, Ensenada, Baja California. Smith, P. E., W. Flerx, and R. P. Hewitt. 1985. The CalCOFI vertical egg tow (CalVET) net. In An egg production method for estimating spawning biomass of pelagic fish: application to the northern anchovy, Engraulis mordax, R. Lasker, ed. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 36, pp. 27-32. Thomson, C., C. Scannell, and J. Morgan. 1988. Status for the California coastal pelagic fisheries in 1987. NMFSISWFC Admin. Rep. LJ-88-18. 31
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LO AND METHOT: 1988 NORTHERN ANCHOVY SPAWNING BIOMASS<br />
CalCOFl Rep., <strong>Vol</strong>. <strong>30</strong>,<strong>1989</strong><br />
Year<br />
class<br />
--<br />
1975<br />
1976<br />
1977<br />
1978<br />
1979<br />
1980<br />
1981<br />
1982<br />
1983<br />
1984<br />
1985<br />
1986<br />
1987<br />
-<br />
TABLE 8<br />
Recruitment to the Fishery at Ensenada, Mexico<br />
~<br />
Age 0<br />
Period 3<br />
-~<br />
Period 4<br />
0 E AV<br />
-.<br />
0 E AV<br />
,017 ,011 ,004 ,122 ,026 ,032<br />
,233 ,091 ,053 ,666 ,451 ,468<br />
,039 ,041 ,007 .194 ,198 ,205<br />
,100 ,152 .017 ,732 ,690 ,194<br />
.046 ,146 ,013 ,365 .420 ,162<br />
,008 ,065 ,008 ,350 ,204 ,048<br />
.060 ,103 ,039 ,251 ,231 ,160<br />
,045 ,159 ,015 ,481 ,632 ,215<br />
,104 ,111 ,015 .480 ,362 ,376<br />
,274 .213 ,043 ,7<strong>30</strong> ,755 ,714<br />
- - - .702 ,5<strong>30</strong> ,725<br />
,091 ,171 ,028 ,672 ,544 .2<strong>30</strong><br />
,414 ,153 ,027 ,478 ,473 ,234<br />
Age 1<br />
Period 1<br />
Period 2<br />
~_____<br />
0 E Av 0 E<br />
- - - 070 256<br />
313 576 633 337 368<br />
- - - - -<br />
- - - 652 692<br />
- - - 502 447<br />
- - - 576 488<br />
- - - 110 338<br />
587 767 384 899 873<br />
- - - 631 656<br />
- - - 457 592<br />
- - - 701 708<br />
914 722 ,549 767 ,824<br />
Note: Age 0 anchovy are partially recruited to this fishery in the third period of the year. They typically are fully recruited in the second period of<br />
the following year. The symbols indicate the observed ratio of recruits to total numbers in the Mexican fishery (0), the ratio expected by the model<br />
(E), and the estimated, environmentally sensitive availability used by the model (Av).<br />
Av<br />
1.00<br />
,211<br />
-<br />
,235<br />
,269<br />
,349<br />
,260<br />
1.00<br />
1 .oo<br />
,326<br />
1.00<br />
1.00<br />
intend to reexamine the submodel that predicts<br />
availability from environmental deviations, but it<br />
seems unlikely that the generally good fit apparent<br />
in table 8 can be substantially improved.<br />
ACKNOWLEDGMENTS<br />
We thank all those who contributed to the spawning<br />
biomass estimate, in particular W. Garcia F.<br />
of CRIP, INP, Mexico, for providing the agecomposition<br />
data of the Mexican fishery at Ensenada<br />
through the MEXUS-PACIFIC0 program;<br />
the individuals who collected, sorted, staged, and<br />
processed the plankton samples from the January<br />
1988 <strong>CalCOFI</strong> cruise; all crew members of the<br />
NOAA ship David Starr Jordan; John Hunter for<br />
reading the manuscript; and two reviewers for their<br />
critiques.<br />
LITERATURE CITED<br />
Bindman, A. G. 1985. The 1985 spawning biomass of the northern<br />
anchovy. NMFS SWFC Admin. Rept. LJ-85-21,21 pp.<br />
Lasker, R., ed. 1985. An egg production method for estimating spawning<br />
biomass of pelagic fish application to the northern anchovy<br />
(Engradis mordax). U.S. Dep. Commer. NOAA Tech. Rep. NMFS<br />
36, 99 pp.<br />
Lo, N. C. H. 1985. Egg production of the central stock of northern<br />
anchovy, Engraulis mordax, 1951-82. Fish. Bull., U. S. 83:137-150.<br />
MacCall, A. D. 1974. The mortality rate ofEngraulis mordax in southern<br />
<strong>California</strong>. Calif. Coop. <strong>Oceanic</strong> Fish. Invest. Rep. 17:131-135.<br />
Mais, K. F. 1974. Pelagic fish surveys in the <strong>California</strong> Current. Calif.<br />
Dep. Fish Game Fish. Bull. 162.79 pp.<br />
Methot, R. D. 1986. Synthetic estimates of historical abundance and<br />
mortality for northern anchovy, Engraulis mordax. NMFS SWFC<br />
Admin. Rep. LJ-86-29,85 pp.<br />
-. In press. Synthetic estimates of historical abundance and mortality<br />
for northern anchovy. In Mathematical analysis of fish stock<br />
dynamics, E. Vetter and B. Megrey, eds.<br />
Methot, R. D., and N. C. H. Lo. 1987. Spawning biomass of the<br />
northern anchovy in 1987. NMFS SWFC Admin. Rep. LJ-87-14,46<br />
PP.<br />
PFMC. Pacific Fishery Management Council. 1983. Northern anchovy<br />
fishery management plan. PFMC, Metro Center, 2000 SW First<br />
Ave., Portland, OR 97201.<br />
Secretaria de pesca de Mexico. 1988. Boletin anual temporada 1987,<br />
centro regional de investigacibn pesquera, ediado en coordinacibn<br />
con la cimara nacional de la industria pesquera delegacibn, Ensenada,<br />
Baja <strong>California</strong>.<br />
Smith, P. E., W. Flerx, and R. P. Hewitt. 1985. The <strong>CalCOFI</strong> vertical<br />
egg tow (CalVET) net. In An egg production method for estimating<br />
spawning biomass of pelagic fish: application to the northern anchovy,<br />
Engraulis mordax, R. Lasker, ed. U.S. Dep. Commer.,<br />
NOAA Tech. Rep. NMFS 36, pp. 27-32.<br />
Thomson, C., C. Scannell, and J. Morgan. 1988. Status for the <strong>California</strong><br />
coastal pelagic fisheries in 1987. NMFSISWFC Admin. Rep.<br />
LJ-88-18.<br />
31
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