Abstract

The Argentine anchovy (Engraulis anchoita) spawns intensely in the Argentine Sea from October to January. At least two populations exist with different reproductive areas: Northern and Patagonian population. Daily Egg Production Method (DEPM) was applied to estimate the spawning biomass of both stocks in the 1996-2002 period. In the DEPM, biomass is derived from estimates of the daily egg production (Po) and the average number of eggs spawned daily. Po values ranged between 1.7 - 3.4*1013 eggs for the Northern and 0,5 - 1,1*1013 for the Patagonian stock. For both populations the percentage of females was 41-58%, spawning frequency (S) was 0.09 - 0.18 and relative fecundity was 421 - 646 g of fish ovary free. Spawning biomass ranged between 540,000 t and 1,271,000 t (CV: 0.65-0.95) for the Northern stock and between 133,000 t and 511,000 t (CV: 0,57-0,90) for the Patagonian stock. The high coefficients of variations were associated with the DEPM estimates, mainly reflection imprecision in the estimation of egg mortality rate and spawning frequency. Biomass values obtained with this method were lower than values calculated using the Acoustic Method. Moreover, anchovy biomass showed a large inter annual variation typically of small pelagic fish species. Results of this work indicated that the biomass of the argentine anchovy estimated with the DEPM showed a higher variance than the calculated for another Engraulis species. However, Po represents a satisfactory index to estimate the biomass of the Argentine Anchovy spawning population.

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