Influence of Oceanographic Variability on the Life Cycle and Spawning Period of Sardinella fimbriata in the Northern Part of Bay of Bengal

Abstract

Reproduction and distribution patterns of Sardinella fimbriata had responded differently to oceanographic changes in various parts of the world. This is the first report investigating the effects of oceanographic parameters on the maturation and spawning of S. fimbriata in the northern part of Bay of Bengal. Monthly precipitation rate, sea surface temperature (SST) and chlorophyll-a data were analyzed for possible correlation with Catch per Unit Effort (CPUE) of the fish species under study. Gonado-somatic Index, Gastro-somatic Index, and histology of the gonadal maturity stages were also studied. The peak spawning activity was found to take place during the period with the highest precipitation rate (r2 = 0.5006, p < 0.05) i.e. during September. Like precipitation, a similar positive correlation was also observed between SST and CPUE (r2 = 0.286, p < 0.05). On the contrary, no direct correlation between chlorophyll concentration and CPUE was found. Our study revealed that the Gonado-somatic index was higher during monsoon months (June–September) and conversely, the Gastro-somatic Index was higher during January–February. Histological study on the gonad of the S. fimbriata revealed the appearance of six different stages of gonadal maturity. The number of juveniles was higher during the post-monsoon period concurrently with high chlorophyll concentration. The growth and maturity of S. fimbriata are thereby found to be strongly associated with this recorded concurrence.