Abstract

The aim of this study was to undertake a baseline-survey on the spatial distribution, relative abundance and size composition of reef-associated sharks in St Eustatius, Saba and the Saba Bank, windward islands of the Caribbean Netherlands. From 2012 to 2014 376 sites were surveyed with stereo Baited Remote Underwater Video (sBRUV) deployments. Videos were analysed for shark presence and individual sharks were measured using stereo-video, enabling accurate length measurements. A total of 153 sharks belonging to six species were recorded. Mean probability of observing at least one shark per recording is 0.29. In 4.3% of the video deployments two or more sharks were observed. Nurse shark was the most frequently observed species (n = 78) followed by Caribbean reef shark (n = 62), blacktip reef shark (n = 6), tiger shark (n = 5), great hammerhead shark (n = 1) and silky shark (n = 1). Significant spatial differences in geographic location were found for abundances of G. cirratum and C. perezi. Mean probability of observing these shark species on St Eustatius and the Saba Bank was found to be twice as high as compared to Saba. Habitat complexity and depth also had significant effects on total shark abundances. Mean probability of observing a reef-associated shark increased with habitat complexity and decreased with depth. The effect of management zone was not significant. Individuals of G. cirratum were significantly larger on the Saba Bank and in sites with low habitat complexity. Judging by total shark abundances, the shark populations of the Saba Bank, Saba and St Eustatius appear to be in reasonably healthy state compared to other areas in the Caribbean. The vast majority of observed sharks were juveniles, indicating that these shallow waters may be used as nursery areas.

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