Estimation of drift gillnets selectivity for Carrangoids papuensis in Kanyakumari coast of South India

Abstract

Size selectivity parameters of drift gillnet for Carangoides ferdau and Caranx papuensis were estimated from catches obtained from the nets of 13.5, 14, 14.5 and 15 cm stretched mesh sizes operated in the Kanyakumari coast of South India from September 2002 to April 2004. In this study, maximum likelihood procedure was followed and a proprietary software GILLNET (Constat, Denmark) was used to fit selection curves viz., normal location, normal scale, log-normal, gamma and bi-normal. Of them, bi-normal model was found as best-fit for both the catch data. The fishing power influenced the selectivity of the gear in the case of C. ferdau while there was no influence in the other species C. papuensis. There was no significant difference between better-fit and best-fit models in both catch data. Modal length increased with mesh size. Shape and size of the selectivity curves were uniform in size. The mesh size 14.5 cm performed better than modeled by capturing larger size group of fishes with narrow selection range. Entangling and gilling appeared as common capture pattern in both the species. Over dispersion was found in the best-fit bi-normal model which also indicated the lack of fit and suggested for multi-nomial fitting of data.