Assessment of an artisanal shrimp fishery of Litopenaeus vannamei in a lagoon-estuarine system based on the concept of maximum sustainable yield

The apparent simplicity of the concept of the surplus production model has promoted its wide application among fishery managers responsible for the exploitation of offshore shrimp stocks. However, no attempts have been made to utilize it for the assessment of shrimp populations exploited in coastal lagoons-estuarine systems. These are artisanal fisheries whose structure includes small boats and fixed fishing traps. In this study the concept of maximum sustainable yield was used (MSY) as a base for the evaluation of the shrimp fishery (Litopenaeus vannamei) in the lagoon-estuarine system Carretas-Pereyra, Gulf of Tehuantepec, Mexico. A dynamic biomass model was applied to analyze catch per unit effort (CPUE) of 1983-2006. In the commercial exploitation of the shrimp stock two main types of fishing methods are employed: stationary enclosures and cast nets. Maximum shrimp production (806 t) was recorded in 1987, followed by a sustained declining trend of CPUE thereafter. Even though fishing effort remained constant since 1995, the shrimp landings maintained a declining trend. Total shrimp production recorded from 2000 fell below the estimated level (mean= 58%) of maximum sustainable yield (MSY) at 248,393 kg yr^-1. Observed effort (505 fishing vessels) was 45% over the estimated effort at MSY (EMSY= 349 vessels). These results reveal conditions of overexploitation of the shrimp stock, a declining pattern in its abundance, and a serious risk of an economic collapse of the shrimp fishery in the study area.