Title: Monitoring and evaluating the present status of the shrimp trawl fishery off the west coast of Sri Lanka

A well established shrimp trawl fishery exists in the coastal waters off Handala and Negombo off the western coast of Sri Lanka. These were investigated from 1997 to 2004 to assess production fluctuating trends, population parameters, mortality rates and stock status. Growth parameters (L∞ and K), mortality coefficients (Z, M and F), growth performance index (Ǿ) and exploitation ratios were estimated for Metapenaeus dobsoni and Penaeus indicus using FiSAT software. Probabilities of capture and recruitment patterns were stimulated for both species. Relative yield per recruit (Y´/R) and biomass per recruit (B´/R) curves were plotted to derive reference points and evaluate the exploitation rates of the two species. Dynamic biomass models were used to fit time serious catch and effort data in R package as an alternative approach to evaluating stock status. Total catch, effort, CPUE and by-catch showed seasonal variations. Monthly and annual shrimp abundance fluctuation analysis revealed that CPUE values recorded from May to September were significantly different from other periods (P<0.05), which apparently coincide with the southwest monsoonal period of the country. M. dobsoni, P. coromondalica and P. indicus were reported as major shrimp species from both fisheries. Mean annual shrimp production for the study period was estimated as 164 t and 125 t from Negombo and Handala respectively. Correlation between Handala and Negombo monthly shrimp production fluctuations showed that the two fisheries are functioning independently (r2 =0.102). Both Y‟/R and dynamic biomass model analysis concluded that Handala and Negombo shrimp trawl fisheries are operated below the MSY. Hence, there is potential to increase the utilisation based on further investigation on the resource. The present findings can be used as a baseline for future investigations.