Shark Nursery Grounds of the Gulf of Mexico and the East Coast Waters of the United States

Shark Nursery Areas of Central Louisiana’s Nearshore Coastal Waters

Julie A. Neer, Jason K. Blackburn, and Bruce A. Thompson


Abstract.—In an effort to obtain information on how Louisiana’s nearshore coastal waters function as shark nursery habitat, a 3-year gill-net survey was conducted between May 1999 and September 2001. Sharks were identified to species, sexed, and assigned a maturity stage, and four length measurements were recorded. Catch per unit effort (CPUE) was calculated both on a set-by-set and annual basis to evaluate intra- and interannual variations in shark abundance. Pearson’s correlation and multiple linear regression were used to examine the relationships between CPUE and the environmental variables temperature, salinity, and dissolved oxygen. Kernel density analyses were conducted within a geographic information system to evaluate potential areas of high shark catch abundance. A total of 1,002 sharks representing eight species were captured during 320.42 h of gillnet sampling, for an overall CPUE of 3.13 sharks/net hour. The vast majority (~80%) of the sharks observed were neonate and young-of-the-year individuals, with the remaining 20% of the catch dominated by young juveniles. Differences in CPUE between 1999 and 2000 were nonsignificant (p = 0.084) while differences between 2000 and 2001 were significant (p = 0.025) for all species combined. Multiple linear regressions between CPUE and salinity, temperature, and dissolved oxygen were insignificant for all species with the exception of the blacktip shark Carcharhinus limbatus. Kernel density analysis indicated that the northern and eastern ends of East Casse Tete Island, the gulf side of East Timbalier Island, and the pass between the mainland and East Timbalier Island had consistently high CPUEs during all 3 years of the survey.