Analysis of the reproductive potential of two stocks of Engraulis anchoita in the Argentine Sea

PÁJARO, M.; LEONARDUZZI, E.; HANSEN, J.; MACCHI, G. J.

CIENCIAS MARINAS

INST INVESTIGACIONES OCEANOLOGICAS, U A B C, APARTADO POSTAL 423

Año: 2011 vol. 37 p. 603 - 618

0185-3880

Relative batch fecundity, spawning frequency, size at 50% maturity, sex ratio, and egg production were estimated for the Bonaerense and Patagonian Engraulis anchoita stocks. Samples were collected during 19 research surveys carried out over the main spawning seasons and areas of both groups from 1993 to 2008. Reproductive potential between stocks was compared by analyzing the length-class structure and considering environmental variations. Daily egg production varied between 0.2 × 10^7 and 7.3 × 10^7 oocytes and the mean annual value was higher for the Bonaerense than the Patagonian stock (2.9 × 10^7 and 0.54 × 10^7 oocytes, respectively). In both stocks, larger size classes produced more oocytes than smaller and more abundant females. No correlation was observed between egg production and adult biomass and between egg production and age-1 recruits. Length at first maturity was lower for the Bonaerense than the Patagonian stock (100.3 and 119.8 mm total length, respectively). Bonaerense and Patagonian spawning frequency estimates were 0.125 and 0.116 (statistically significant differences were not observed, P > 0.788), and mean relative batch fecundity values were 508 and 493 oocytes g-1 (P > 0.680), respectively. Mean annual relative batch fecundity values for the Bonaerense stock showed a negative trend in the period 1993-2008, coinciding with a 4 ºC increase in mean sea surface temperature in the area during the same period.