Field observations on white shrimp, Litopenaeus setiferus, during spring spawning season in South Carolina, U.S.A., 1980-2003

Abstract

Fishery dependent trawl samples taken in spring prior to commercial shrimp trawling season in South Carolina were analyzed for annual relative abundance, sex ratios, and ovarian development of white shrimp, Litopenaeus setiferus, during 1980-2003. Fishery independent trawl samples were analyzed for relative abundance and ovarian development of female L. setiferus during the same period. Relative abundance varied greatly among years, and was thought to be strongly influenced by winter water temperature. The decade of the 1990s was a period of mild winters and high abundance of white shrimp in South Carolina. Biological observations about size and sex ratios of shrimp were consistent with past studies done along the southeastern Atlantic coast. Proportions of male shrimp in fishery dependent collections appeared to increase with advance of maturation of female shrimp. After spawning, numbers of male shrimp declined, suggesting that males are attracted to location of females prior to spawning, as has been postulated in published laboratory studies. Analyses of fishery independent samples indicated a slight delay in time of maturation of female shrimp during cool temperatures in spring; conversely, spring seasons with warm temperatures seemed to speed up maturation. This study should help elucidate the location of spawning areas for L. setiferus off South Carolina, in addition to its primary purpose of managing the shrimp fishery on a biological basis.