The Role of Predation in the Shrimp Stock Collapse in the Southern Gulf of Mexico

摘要

The Campeche Sound, in the southern Gulf of Mexico, has historically been an important area for the exploitation of shrimp. Highest yields were obtained in the early 1970s with nearly 25,000 metric tons (mt) per year. However, catches declined 50% by1980 and 90% by the late 1990s. Currently yields amount to around 1,500 mt. Several hypotheses have been suggested to explain the stock decline, including high fishing intensity, environmental changes, impact of the oil industry, and degradation of coastal areas. In this contribution, we explore the influence of predation in the shrimp stock collapse. The approach is based on a trophic model using Ecopath for the period of 1978-1981, previous to the drastic decline in shrimp yields. The model considersexplicidy the interaction of two interdependent ecosystems, the Terminos Lagoon and the adjacent continental shelf. Shrimp life history was partitioned to juveniles living in the lagoon and adults on the continental shelf. They are linked through a stock—recruitment relationship. The model provides the starting point for dynamic simulations using Ecosim. Simulations were calibrated using the historical exploitation pattern. Several scenarios show how shrimp is vulnerable to predators assuming bottom up, top down, and mixed control. When bottom up control is assumed, the model does not simulate the historical stock depletion. Under top down control, depletion was higher than recorded by the fishery. Mixed control scenario was closest to historical data trend. Results suggest that predation has an important role in the shrimp stock depletion.