Catch rates as indicators of ecosystem health and exploitation status in the shrimp fishery in the South China sea

Based on catch and effort data analyses covering the period 1996–2002, time series of catch rates in the trawl fisheries in the South China Sea along the coasts of Bac Lieu and Ca Mau in South East Vietnam were estimated. The indicators include catch rates for total shrimp catch, five major shrimp catch groups and 15 commercial shrimp groups estimated as quarterly averages for trawlers divided into five size groups. The analyses indicated that despite a reduction in catch rates, shrimp is still the principal resource for the trawl fleets in South Vietnam. Seasonality in the shrimp catch rates that might reflect seasonality in shrimp recruitment was found, making this resource potentially suitable for a fishery management system based on closed seasons. Further, the data indicate that the major part of the catches are comprised of low value species belonging to the genera Parapenaeopsis; whereas the most valuable species, i.e. the Penaeus and Metapenaeus catch groups have been significantly depleted during the period investigated. Based on the experiences from the present analysis, recommendations are presented with regard to adjustments of the enumerator data collection programme to fulfil the requirement of a dynamic fishery management system.