Notes on the Occurrence and Distribution of Elasmobranchs in the Ten Thousand Islands Estuary, Florida
Pascale A. Steiner, Marcel Michel, and Patrick M. O’Donnell
Abstract.—The goal of this report is to contribute to existing information on the occurrence and distribution of elasmobranch species found in the mangrove estuary of the Ten Thousand Islands located in southwest Florida. A planned hydrologic restoration shall occur in this area in the near future, and this baseline data will be beneficial in documenting how changes in freshwater flow may influence top predators in this system. Sampling was conducted from 1997 to 2002 using a combination of gill nets and longlines. A total of 1862 elasmobranchs, including 17 species representing eight families, were reported. A total of 1,377 sharks, including nine species from three families, and 485 rajiformes, including eight species from five families, were captured. Sharks and rajiformes were caught in every month of the year, though there was large variation in the occurrence of species per month. Comparing fishing gears, 94% of all sharks were caught with gill nets and 6% were caught with longlines, while 100% of rajiformes were caught in gill nets. More than 52% of all shark catches were bonnetheads Sphyrna tiburo, 24% were blacktip sharks Carcharhinus limbatus, and 15% were bull sharks C. leucas. All other shark species were far less abundant (<5% of total sharks). Cownose rays Rhinoptera bonasus comprised almost 50% of the total catches of rajiformes, followed by stingrays Dasyatis sp. at 24% and spotted eagle rays Aetobatus narinari at 18%. All other rajiformes were less abundant (≤6%). This study delivers the first comprehensive account of the Ten Thousand Islands’ elasmobranch community with indications of its use as a shark nursery area.