Biological aspects and catch trends of elasmobranchs in the inshore waters of Goa, west coast of India

Abstract

Despite being the top predators Elasmobranchs are dwindling due to excessive fishing pressure. However, very few studies along Indian coasts have focused on their eco-biological aspects. The present investigation comprising 158 trawl samples (220 h effort) along the nearshore fishing grounds of Goa revealed that the elasmobranch population comprised 10 species (2 sharks, 6 rays and 2 skates). Analysis of spatial variation revealed significant variations between the regions (abundance, alpha = 0.001, P= 0.000191; weight, alpha = 0.001, P = 2.14E-08) suggesting high catches along southern region, owing to lesser fresh water discharge due to absence of major estuarine system. Assessment of size class indicated that juveniles dominated the elasmobranch population with few stray occurrences of adults. Dietary analysis of the three commonly observed species revealed the dominance of teleosts (45.95 percent IRI), followed by crustaceans (40.19 percent IRI). Analysis of the catch trends (1969-2004) of elasmobranchs in this region indicated meagre contribution (0.05-5.04 percent) to the total marine fish landings of Goa. Further, the catch trends displayed decrease in recent times suggesting reduction in trophic level of the regional fishery perhaps caused by fishing out of carnivores coupled with increased catches of low trophic level fishes as evidenced in the present study. These findings have implications for the trophic web dynamics of the coastal waters, which in turn affect the coastal fisheries of the region.