A guest post from Oliver Shipley at the Cape Eleuthera Institute. Photos courtesy of Sean Williams. Thanks Oliver!
Across the Caribbean, overexploitation has led to growing concern regarding the fate of apex predator populations, particularly sharks, which constitute an important structural component of many marine ecosystems. In 2011 The Bahamas outlawed the commercial fishing, and trade of any shark related products, providing a refuge from high levels of exploitation elsewhere in the Caribbean. The Caribbean reef shark (Carcharhinus perezi) is the quintessential coral reef predator across its sub-tropical range, and aside from its ecological importance on coral reefs, is arguably the most economically important elasmobranch species in The Bahamas. Caribbean reef sharks are thought to generate over $16 million annually to the Bahamian economy through ecotourism ventures such as shark diving. Despite the importance of Caribbean reef sharks, their broad scale movements, particularly their interactions with the boundary of the Bahamian Exclusive Economic Zone (EEZ) remain poorly defined. Such data is urgently required to examine the efficacy of the national shark sanctuary in protecting Caribbean reef shark populations.
Between 2010 and 2011 researchers from the Shark Research and Conservation Program, The Cape Eleuthera Institute (www.ceibahamas.org/sharks), The Bahamas, Microwave Telemetry Inc. (www.microwavetelemetry.com), Stony Brook University, USA, and University of Alberta, Canada, deployed 11 pop-up satellite archival tags, which provide time series geolocation, depth, and temperature estimates, on mature Caribbean reef sharks of both sexes. Animals were tagged off the coast of Eleuthera, an eastern family island of The Bahamas, with the goal to discern horizontal and vertical movements of Caribbean reef sharks and examine how this species interacts with the boundary of the Bahamian EEZ. Results indicated the tagged sub-population remained faithful to The Bahamas throughout variable deployment durations (30 – 243 days), and rarely traversed beyond the boundary of the Bahamian shark sanctuary. Interestingly, depth data also indicated that these reef-associated species perform mesopelagic excursions to depths exceeding 400m. These movements are hold significant ecological value, and likely provide vital connectivity between shallow and deep-water habitats. Although limited to a relatively small number of individuals, results from this study suggest some sub-populations of mature Caribbean reef sharks remain relatively well protected throughout the year. These observations hold great promise for vitality of Bahamian shark diving operations, and the associated economic benefits to the national Bahamian economy.
Shipley, O. N., Howey, L. A., Tolentino, E. R., Jordan, L. K., Ruppert, J. L., & Brooks, E. J. (2017). Horizontal and vertical movements of Caribbean reef sharks (Carcharhinus perezi): conservation implications of limited migration in a marine sanctuary. Royal Society Open Science, 4(2), 160611.