Local indicators of abundance and demographics for the coastal shark assemblage of Bimini, Bahamas

Understanding population dynamics is essential for implementing effective conservation and management of coastal sharks. Fisheries-independent surveys can offer valuable information for such data-limited situations. A 12-year (2004-2015) standardized, shallow water longline survey was conducted monthly in the coastal waters of Bimini, Bahamas. Each monthly survey comprised five longline sets, totaling 75 hooks, with a soak time of 24 h. A total of 770 sharks from nine species were caught over the course of the study, with tiger (Galeocerdo cuvier), nurse (Ginglymostoma cirratum), blacktip (Carcharhinus limbatus) and lemon (Negaprion brevirostris) sharks comprising 95% of the catch. The majority of tiger (87%), nurse (62%), blacktip (67%), and lemon (82%) sharks were of immature lengths. A greater number of captured tiger (77%) and blacktip (66%) sharks were female, while nurse (55%) and lemon sharks (73%) were predominantly male. Poisson generalized additive models were used to analyze local abundance trends and examine how catch rates were influenced by year, month, location, tide, hour of capture, and lunar cycle. Seasonal trends indicate greater catches of the nurse, blacktip and lemon sharks during the summer months. Annual trends indicated relatively stable catch rates for the tiger, blacktip and lemon shark. Nurse shark catch rates were highly variable during the survey. Results from this study improve our understanding of the coastal shark assemblage in Bimini, Bahamas, and provide important local abundance trend information that could be beneficial for conservation and regional assessments.