PARRISH ET AL.: AGE DEPENDENT FECUNDITY IN NORTHERN ANCHOVY 



Table 3.— Proportion of maturity stages 5 + 6, number of spawnings and fecundity of female northern anchovies sampled in the Sea 



Survey Program (lat. 29.5°-34.5°N) and San Pedro fishery. 



July 1 Aug. 1 Sept. Oct. Nov. Dec. 



Jan. 



Feb. 



Mar. 



Apr. May June Total 2 Eggs/g 3 



Prop. 5 + 6 

 Spawnings 

 Wt. (g) 

 No. eggs 



Prop 5 + 6 

 Spawnings 

 Wt. (g) 

 No. eggs 



Prop. 5 + 6 

 Spawnings 

 Wt. (g) 

 No. eggs 



Prop. 5 + 6 

 Spawnings 

 Wt. (g) 

 No. eggs 



Prop. 5 + 6 

 Spawnings 



0.000 

 0.000 



0.000 

 0.000 



0.002 0.000 

 0.062 0.000 



15.5 15.5 

 492 



0.022 0.024 

 0.682 0.744 



18.3 18.3 

 6,527 7,120 



0.021 0.016 

 0.651 0.496 



20.1 20.1 

 6,914 5,268 



0.017 

 0.527 



0.021 

 0.651 



0.000 

 0.000 

 11.2 

 



0.005 

 0.150 

 17.4 

 1,357 



0.005 

 0.150 

 19.1 

 1,506 



0.004 

 0.120 

 20.9 

 1,330 



0.008 

 0.240 



0.005 

 0.155 

 11.1 

 832 



0.007 

 0.217 

 16.8 

 1,887 



0.010 

 0.310 

 19.3 

 3,148 



0.013 

 0.403 

 21.8 

 4,680 



First spawning season 



0.000 0.000 0.005 0.087 0.023 

 0.000 0.000 0.155 2.436 0.713 



12.0 11.0 11.4 11.6 12.8 

 860 13,793 4,536 



Second spawning season 



0.001 0.001 0.015 0.110 0.132 

 0.030 0.031 0.465 3.080 4.092 



17.2 16.3 16.2 15.6 16.5 



268 261 8,881 24,626 34,866 



Third spawning season 



0.002 0.002 0.008 0.124 0.251 

 0.060 0.062 0.248 3.472 7.781 



19.2 19.3 19.1 18.0 20.7 



606 630 2,489 33,836 85,360 



Fourth-plus spawning seasons 



0.003 0.003 0.008 0.115 0.271 



0.090 0.093 0.248 3.220 8.401 



22.3 22.2 23.6 23.3 26.6 



1,071 1,102 2,952 37,390 110,293 



All spawning seasons combined 



0.011 0.002 0.002 0.010 0.107 0.151 

 0.341 0.060 0.062 0.310 2.996 4.681 



0.036 0.011 

 1 .080 0.341 



13.7 15.4 

 7,438 2,687 



0.065 0.021 

 1.950 0.651 



17.7 18.3 

 17,980 6,230 



0.101 0.031 

 3.030 0.961 



22.2 20.9 



35,891 10,655 



0.166 0.065 

 4.980 2.015 



26.5 25.7 



67,123 26,454 



0.004 

 0.120 

 13.6 

 819 



0.020 

 0.600 

 17.5 

 5,462 



0.026 

 0.780 

 22.7 

 9,467 



0.056 

 1.680 



25.7 



18,136 



0.094 0.044 0.012 

 2.820 1.364 0.360 



5.3 



32,514 2,803 



11.9 



102,174 6,550 



19.2 



205,819 11,434 



23.5 



322,957 13,861 



15.1 



'Missing data estimated from adjacent months, 

 includes 5% correction for spawning incidence bias. 

 3 Total eggs/February weight. 



be particularly susceptible to collapse; however, per- 

 turbations of recruitment is a potential threat to any 

 fishery in which one or two year classes comprise 

 the bulk of the landings. The stock-recruitment ap- 

 proach to understanding or predicting recruitment 

 has fallen into disfavor, at least in the small pelagic 

 fishes, because stock size has not proven to be a good 

 predictor of recruitment. In its pure form (Bever- 

 ton and Holt 1957; Cushing 1971; Ricker 1975) the 

 stock-recruitment concept is based on two factors: 

 1) Parent stock size is a measure of the reproduc- 

 tive potential of the stock, and 2) there are compen- 

 satory mechanisms which reduce the number of 

 recruits per spawner as the size of the parent stock 

 increases. This compensation occurs through some 

 mix of reduced fecundity of the parent stock, 

 reduced growth of the recruiting cohort and in- 

 creased mortality of the recruiting cohort. Recruit- 

 ment variations are usually attributed to changes 

 in environmental conditions, usually unknown, and 

 the causal mechanisms, also usually unknown, are 

 thought to occur during the early life history stages. 

 The present emphasis of recruitment research is on 

 the growth and mortality of the early life history 

 stages. Potential variations of stock fecundity as a 

 factor in recruitment variations has largely been 

 ignored. 

 There are now 6 years of egg production estimates 



available for the central stock of northern anchovy 

 (Bindman 1985). The mean spawning incidence for 

 these years is 0.124 and the spawning incidence 

 varied from 0.094 in the El Nino year of 1983 to 

 0.160 in 1984. This implies that the central stock 

 produced 70% more eggs, per unit of spawning 

 biomass, in 1984 than in 1983. Santander (1980) 

 showed that the Peruvian anchoveta had both re- 

 duced spawning and an alteration of the seasonal- 

 ity of spawning during the 1972 El Nino. The results 

 presented here, which show that fecundity is strong- 

 ly age dependent, suggest that the reduction in age 

 composition caused by heavy exploitation will great- 

 ly reduce the average fecundity per unit of biomass 

 and also result in a reduction in the length of the 

 spawning season. It appears that interyear varia- 

 tions in the age composition of a stock or in en- 

 vironmental factors associated with energy reserves 

 or egg production are likely to alter greatly a stock's 

 reproductive potential. If this is the case in other 

 species which have multiple spawning, much of the 

 variance in the stock-recruitment relationships of 

 these fishes may be due to the fact that spawning 

 biomass is a poor index of the reproductive poten- 

 tial of the stock. 



To date information concerning age-specific 

 reproductive potential has not been available for 

 multiple spawning fishes because of the difficulty 



515 



