Environmental influence on the secondary productivity and fish abundance in coastal fishing grounds off Mangalore, south-eastern Arabian Sea

Abstract

Environmental parameters influence the productivity and abundance of fish in marine ecosystems. In this study, we attempted to analyse the relationship between environmental parameters and abundance of fish in trawling grounds in south-eastern Arabian Sea along the coast of Karnataka. Among the 85 species of finfishes and shellfishes caught in the trawling grounds, 41 finfish species, 24 crustaceans, 18 molluscs and two echinoderms were recorded. Seasonal differences were seen in biomass with the highest biomass during the post-monsoon period (October-January). Water temperature and nutrients were the key contributing factors of seasonal differences in the biotic communities studied. Season specific diagnostic species were identified using SIMPER analysis. Squilla which formed the major prey item of most of the demersal fishes dominated (>40%) coastal grounds throughout all seasons. This could be considered as a fishery indicator of the region. The dominance and abundance of copepods was found to be influenced by sea surface temperature (SST) and nutrients. The results of the study have implications on the fishery, knowledge on environmental factors influencing the abundance and importance of non-commercial species in sustaining the fishery in the region.