REPRODUCTIVE CYCLE AND MORTALITY OF THE JAPANESE OYSTER CRASSOSTREA GIGAS CULTURED IN BAHÍA FALSA, BAJA CALIFORNIA, MÉXICO.

The gonadal development by estimating the percentage of cell components of the mantle (MC) of cultured oysters (Crassostrea gigas) and mortality were studied in the Bahía Falsa, B. C. México from May 1996 to April 1997. Two localities, inner and outer zones of the Bay, were considered. Oysters were grouped in accordance with their position in the culture art, upper, middle, and lower level. Differences among the percentage of developing gametes (DG) and ripe gametes (RG) were according to the locality of the Bay and the position of the oysters in the culture art. In the outer locality, ripe gametes started to appear in February and reached their maximum proportion in May and June (around 60%). There was a trend of minor percentages of DG and RG in the lower level. Reproductive activity extends to November in the upper and middle levels. From September to January the no reproductive period was in curse. In the inner locality the percentage of ripe gametes also started to appear in February but their percentages were higher (around 80%) in May and June than in the outer locality. The reproductive activity ends in September. Percentage of vesicular cells (VC) increased from June to January. There was minor percentage of DG and RG in the lower level. There was no relationship between the gonadic cycle and mortality of oysters but it was with the level of the culture art, and there was an increase in mortality values in the lower than in the middle and upper levels of the culture art and a major mortality in the outer than in the inner studied localities. [ABSTRACT FROM AUTHOR]