A Review of Trawl Selectivity Studies carried out along Indian Coast

Abstract

Though trawling contributes significantly to landings in India, issues like bycatch which comprises of juveniles of commercially important species and impacts to the sea bottom are often implicated. There has been a significant increase in the capacity, both in terms of number and in terms of the size of trawlers during the last decade in India. Technical measures like closed season and gear modification are proposed in the Marine Fisheries Regulation Acts of different states. A large number of Bycatch Reduction Devices (BRDs) have been field tested along the Indian waters which have proven to be effective for exclusion of juveniles. Among the different BRDs, square mesh codends are the most popular, due to its conceptual simplicity and ease of modifications of the existing codends. A large number of studies related to the selection parameters for trawlnets of different mesh sizes, are reported from India. This study attempts to review the results of these studies with respect to methods used for deriving the selection parameters. It is observed that variation exists in the methodology adopted for deriving selection parameters among the reports. None of the studies have analyzed the operational factors that affect selectivity of the gear and similarly the survival of the escapees from the BRDs is not quantified. Though preliminary in nature, the selectivity estimates available now are good enough for coming out with proposals regarding the optimum mesh required for individual species. Inclusion of factors affecting selection into the studies, biological parameters of the targeted species and modeling approaches will help in refining the results already available and a development and adoption of a standard protocol for trawl selectivity studies will help significantly