Date of Award
Engineering and Applied Science
Earth and Environmental Sciences
Dr. Martin O'Connell
Dr. Mark Kulp
Dr. John McCorquodale
Dr. Demian Chapman
Dr. John Carlson
Anecdotal evidence suggested that immature lemon sharks (Negaprion brevirostris) occur at the Chandeleur Islands in southeastern Louisiana. From May 2009 to August 2011, the Nekton Research Laboratory at the University of New Orleans regularly sampled habitats at the Chandeleur Islands to confirm the presence of immature individuals of this species. During these efforts, 147 immature lemon sharks (neonates, young-of-the-year, and juveniles) were collected. Each shark was PIT tagged and a tissue sample was taken for genetic analyses. Sizes ranged from 56 – 177 cm total length. Sharks showed a preference for sandy substrate and smaller individuals showed significant preference for shallow waters. Collection data for N. brevirostris were obtained from various locations around the Gulf of Mexico for comparison. Based on a review of current literature, collection data, and microsatellite analysis it was possible to classify the Chandeleur Islands as an elasmobranch nursery ground under the definition presented by Huepel et al. (2007). Current literature and high densities of N. brevirostris suggests that the Chandeleur Islands are the only area in the northern Gulf of Mexico where neonatal and YOY lemon sharks have been recorded. Results from a combination of SPOT 5 satellite tags, PIT tags, and FLOY tags show that immature N. brevirostris at the Chandeleur Islands remain in the vicinity of the islands for several months. The abundance of juvenile sharks across years provides evidence of continuous use of these islands as a pupping area. Genetic analysis supports this information with 7 of 15 mothers returning across years. The combination of this information indicates that the Chandeleur Islands are the northern- and western-most documented nursery ground for this species. Special care should be given to this habitat as CPUE for N. brevirostris decreased significantly during this research following the 2010 Deepwater Horizon disaster and subsequent oil prevention measures. Genetic research indicates a high level of inbreeding and genetic separation between the Chandeleur Islands population and other known populations in Florida, Belize, and the Bahamas.
McKenzie, Jonathan F., "Occurrence and genetic diversity of lemon sharks (Negaprion brevirostris) at a nursery ground at the Chandeleur Islands, Louisiana." (2013). University of New Orleans Theses and Dissertations. 1653.