Trends in Shrimp Catch in the Hypoxic Area of the Northern Gulf of Mexico

Résumé du livre

Introduction: An effect of hypoxia on shrimp landings is expected, both through reducing catch in areas of high hypoxia and concentrating catches in adjacent areas. Investigations of seasonal hypoxia in Louisiana offshore reveal that infauna are killed and fish and shrimp are often sparse or absent (Rabalais and Harper, 1991 and 1992; Renaud, 1986). Comparison of hypoxic areas in the New York Bight and the northern Gulf of Mexico indicate similar reductions in abundance of infauna (Boesch and Rabalais, 1991). Although infauna typically recover during months without hypoxia, the community remains in an early successional state because of mortali-ties during the summer every year (Boesch and Rabalais, 1991). The affected area off of Louisiana is large, covering up to 9500 km 2 (Rabalais et al., 1991), which coincides with historical white shrimp (Penaeus setiferus) and brown shrimp (P. aztecus) fishing grounds (Lindner and Anderson, 1956; Christmas and Etzold, 1977). These shrimp rely upon benthic infaunal foods as the mainstay of their diets (McTigue and Zimmerman, 1991). The National Marine Fisheries Service has a database on monthly shrimp landing statistics for the Gulf of Mexico going back to 1960. The database is used to follow shrimp landings trends and estimate shrimp trawling effort for manage-ment of penaeid shrimp resources in the federal Exclusive Economic Zone (EEZ). Subareas of reported landings and effort include historical areas of hypoxia and thus may be useful in com-parisons of interrelationships. However, it must be recognized that the shrimp statistics database was not designed for detecting effects of hypoxia and reported subareas of landings may be undesirably large for ideal analysis. Notwithstand-ing this shortcoming, the number of data entries are relatively large and cover many years including the past decade when the area of hypoxia has been measured annually. With retrospective analysis, we may be able to observe trends that suggest relationships between shrimp landings or effort and the annual extent of hypoxia.