White shrimp (Penaeus setiferus) recruitment overfishing

Abstract

White shrimp, Penaeus setiferus, is one of the major species exploited in the Gulf of Mexico. Annual catches reached a peak of 1200-2000 t during 1970-80. In the following years, there was a marked decline that took the fishery to less than one-fifth of its highest production levels. Decline was associated first with decreasing fishing power of the fleet and later with the establishment of a new artisanal drift-net fishery. The artisanal fishery has the following characteristics: it acts selectively on spawners older than eight months, its fishing effort increases during spawning periods when white shrimp school and are more vulnerable to drift-nets, and it has displayed an explosive growth rate due to the high profitability. Previous evidence of a spawning stock-recruitment relationship for white shrimp suggests that a recruitment failure had taken place. The relationship between spawning and recruitment, based on the main cohorts of the two annual generations, exhibited a negative tendency that drove the stock down to near-critical spawner biomasses. Environmental influences on recruitment, although important for annual variations, are unlikely to be responsible for this decline. Decline in yield may be attributable to recruitment overfishing, as spawning stock was reduced to almost 8% of virgin biomass. White shrimp have a high resilience to overfishing, as the stock displayed a quick recovery after the artisanal fishing effort decreased. Managing white shrimp with a precautionary approach requires the maintenance of spawning stock at more than 17-20% of virgin biomass.