Abstract

In April 2015, the Cayman Islands gave full legal protection to all sharks and other elasmobranchs throughout its Exclusive Economic Zone. This was the culmination of a research programme initiated in 2008 to determine the status of sharks in Cayman waters and assess the need for their conservation. A Facebook linked citizen science scheme and interviews with fishers, as well as BRUVS and longline surveys, were used to monitor the principal species, among which Caribbean reef sharks (Carcharhinus perezi), blacktip sharks (C. limbatus) and nurse sharks (Ginglymostoma cirratum) are the most common, while tiger sharks (Galeocerdo cuvier), silky sharks (C. falciformis), oceanic whitetip sharks (C. longimanus) and great hammerhead sharks (Sphyrna mokarran) occur locally or seasonally in small numbers. The results of eight years of surveys indicate that shark abundance on Little Cayman is about three times that on the other two islands, and that while abundances in the Cayman Islands overall are higher than many Caribbean locations, they are markedly less than those within large protected or unexploited areas elsewhere or than in the historic past. To investigate the ranges of individual sharks in comparison to the Cayman Islands existing Marine Protected Areas (MPAs) medium-bodied species have been fitted with acoustic tags and larger-bodied ones with SPOT GPS tags. The results have revealed that while some individuals of smaller shark species may be semi-resident within a part of an island, they may also travel significant distances around or between islands. Two Caribbean reef sharks travelled from Grand Cayman to Little Cayman, a distance of about 150 km through water at least 1000 metres deep, one of them completing the return journey twice. Larger sharks were found to travel much greater distances: the majority of seven tagged tiger sharks travelled widely across the Caribbean basin, one returning seasonally to Grand Cayman for at least three further years, while among 18 tagged oceanic whitetip sharks many not only crossed the Caribbean but travelled in to the Gulf of Mexico. The scale of shark movements strongly supported the need for protection on a much larger scale than the existing MPA network could achieve. In further support of the case for shark conserva-tion, an environmental economics study revealed that both residents and visitors value the marine life highly, more so than the islands’ Caribbean culture or fishing. The Non-Consumptive Use Value of sharks to the Cayman Islands, through tourism and recreation, was estimated at US $46.8 to 62.6 million/yr, compared with an estimated Consumptive Use Value, if sharks were sustainably fished, of no more than US $1.3 million/yr.

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