Biological aspects of sea snakes caught incidentally by commercial trawlers of Goa, west coast of India

Abstract

Sea snakes occur in trawl hauls as by-catch, incurring mortality in populations inhabiting commercial fishing grounds (less than 20 m depth) along the coastal inshore waters of Goa. Observations of this incidental catch show that true sea snakes inhabiting inshore waters comprise two species: Enhydrina schistosa and Lapemis curtus, contributing 65 and 35 percent of the population respectively. 70 trawl operations over a period of 17 months with a total fishing effort of 110 hours yielded 43 individuals, all females, which numerically contributed approx 1 percent to the total trawl catch. Seasonal variations indicate that there is an increasing trend in abundance from post-monsoon to pre-monsoon season. The capture of a gravid female from the estuarine inshore waters during January suggests parturition and recruitment among sea snakes during the post-monsoon season. An assessment of the food composition in the stomach content revealed completely digested prey in smaller individuals, whereas in larger-sized individuals these items were either undigested or semi-digested. Qualitative assessment of gut content of sea snakes revealed the dominance of finfish (Ariidae, Engraulidae, Clupeidae). A biological assessment of a gravid female and the association of sea snakes with a barnacle species (Octolasmis grayii) are described.