Estimaciones de atresia mayor en la temporada reproductiva 1999-2000 en la sardina monterrey (Sardinops sagax) en Bahía Magdalena, México

Abstract

The gonadosomatic index (GSI) and the gonadic relative index (GRI) were used for monthly monitoring of Pacific sardine maturity in Bahia Magdalena, Mexico, for the reproductive season of 1999-2000. These indices showed ah increase in gonadic growth in January and March, and a decline in February. Histological analysis of ovaries showed a short spawning season. Juvenile fish were recorded in December. Adults appeared until January. In February, high incidence of atresia in oocytes at the cortical alveolli stage was detected. Later, atresia occurred in advanced vitellogenic oocytes. The active female frequency ranged from 11 to 55% in the spawning season of 1999-2000. Atresia on isolated oocyte frequency was 9% in January 2000, at the beginning of the spawning season. The incidence of major atresia started in February, and reached 54% in March, indicating the end of the spawning season. These results were compared with time series from 1980-1990 on Pacific sardine reproduction in Bahia Magdalena. Evidence indicates that the Pacific sardine spawning season was reduced to two months, and that the active female frequency was low. Environmental influence on ovary reabsorption and skip reproduction season is discussed.