Baited Remote Underwater stereo0Video (stereo0BRUV) survey as a basis for elasmobranch conservation and management on Sint Maarten, Dutch Caribbean
Elasmobranch populations (sharks, rays and skates) worldwide have declined drastically over the past decades and the situation in the Dutch Caribbean is no different. In Sint Maarten waters a shark sanctuary was established in 2011 and will remain in effect until 2021. In this period the Nature Foundation Sint Maarten is required to compile data on the status of elasmobranch populations to demonstrate the effects of these regulations. A stereo[BRUV survey conducted from March till May 2015 has successfully provided baseline information to enable a future assessment of the effectiveness of the shark sanctuary. The results from this baseline study can be compared with other surveys in the Caribbean to provide further insights into the status of elasmobranchs in the region and compare effects of legislation and management measures. The immediate results from this study have given insights into the relative abundance, species composition and distribution of elasmobranchs across different management zones around Sint Maarten. The widely used sampling technique Baited Remote Underwater stereo[Video (stereo[BRUV) has been used to collect data over 113 deployments. Three different shark species were identified, Carcharhinus perezii (Caribbean reef shark), Ginglymostoma cirratum (nurse shark) and Galeocerdo cuvier (tiger shark) and two different ray species, Dasyatis americana (southern stingray) and Aetobatus narinari (spotted eagle ray). Relative abundance of D. americana was highest of all elasmobranch species in this survey and was found widely distributed across management zones and habitat types. All sharks measured in this study were juveniles, of which C. perezii and G. cirratum have been observed in relatively higher abundances inside the marine park compared to the area outside the marine park. Especially the Conservation Zone within the marine park has shown significant differences in the presence of these species compared to other management zones. This should however be treated with caution as the majority of deployments in the Conservation Zone consisted of reef habitat, for which both species have a preference. Furthermore, previous tourist[driven shark[feeding excursions around Sint Maarten may have an influence on their distribution. This survey on its own is not elaborate enough to provide supporting evidence towards an expansion of the existing marine park. However, the significant numbers of juvenile C. perezii and G. cirratum inside the marine park provide an indication that the shallow coastal waters with high coral reef cover inside the marine park provide an important and protective habitat for these species. These findings, coupled with the effects of Marine Protected Areas (MPAs) on shark populations, provide grounds for a continued protection and conservation of sharks through additional management measures in the marine park. For the juvenile C. perezii, an endemic species to the Caribbean, these grounds are even more solid by providing a spillover effect to adjacent areas around Sint Maarten.