A Baited Remote Underwater Video System (BRUVS)
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Environ Biol Fish https://doi.org/10.1007/s10641-020-01004-4 A baited remote underwater video system (BRUVS) assessment of elasmobranch diversity and abundance on the eastern Caicos Bank (Turks and Caicos Islands); an environment in transition Stephan Bruns & Aaron C. Henderson Received: 26 January 2020 /Accepted: 5 July 2020 # Springer Nature B.V. 2020 Abstract The present study was undertaken to assess efforts in the Turks and Caicos Islands should continue the diversity and abundance of elasmobranch fishes in to focus on coral reef areas, less dramatic environments coral reef and sand flat environments on the eastern such as sand flats should not be ignored. Caicos Bank, with a view to informing marine spatial planning as the island of South Caicos and its environs Keywords Caribbean region . Chondrichthyes . transition to a tourism-based economy. Using baited Biodiversity . BRUVS . Coral reef remote underwater video systems (BRUVS), the nurse shark Ginglymostoma cirratum, Caribbean reef shark Carcharhinus perezi, spotted eagle ray Aetobatus Introduction narinari, southern stingray Hypanus americanus, lemon shark Negaprion brevirostris, tiger shark Galeocerdo Populations of elasmobranch fishes (sharks, skates, cuvier, blacknose shark Carcharhinus acronotus,and rays) have undergone dramatic declines on a global great hammerhead shark Sphyrna mokarran were ob- scale in recent decades (Dulvy et al. 2014). While in- served to use these waters, with G. cirratum and dustrial longline fleets are responsible for the largest C. perezi being particularly abundant. Species diversity component of elasmobranch landings worldwide and overall abundance was greater in the reef environ- (Worm et al. 2013), landings from artisanal fishers can ment than on the sand flats, but G. cirratum was equally also be considerable, especially in developing countries abundant in both environments. Furthermore, even reef- (Walker 1998). However, although the impacts of fish- associated species such as C. perezi were occasionally ing on elasmobranch stocks, both targeted and non- encountered on the flats a considerable distance from the targeted, remain a major concern, habitat loss/ reef. This indicates that although marine conservation degradation and climate change also pose notable S. Bruns : A. C. Henderson (*) S. Bruns The School for Field Studies, Center for Marine Resource Studies, Marine and Freshwater Research Centre, Galway-Mayo Institute South Caicos, Turks and Caicos Islands of Technology, Galway, Ireland e-mail: [email protected] A. C. Henderson Biology Department, UAE University, Al Ain, United Arab Emirates Environ Biol Fish threats. This is particularly true of species that use Brooks et al. 2011;Bondetal.2012;Goetzeand shallow, coastal environments (Knip et al. 2010). Fullwood 2013;Espinozaetal.2014). Historically, information on the biology and ecology of The present study was undertaken to assess the elas- elasmobranch species has typically been gleaned from a mobranch fauna of the eastern Caicos Bank (Turks and combination of fishery-dependent and fishery-independent Caicos Islands) in the Tropical Northwestern Atlantic sources. Their potentially negative impacts notwithstand- (Fig. 1), using a BRUVS approach. Although this region ing, commercial fisheries have provided researchers with of the Caicos Bank supports the bulk of the country’s access to the large numbers of specimens required for commercial fishing activity, most fishing effort is con- fundamental life-history assessments (age and growth char- cerned with spiny lobster Panulirus argus and queen acteristics, size at maturity, annual reproductive cycle etc.) conch Lobatus gigas, with finfish forming a relatively (e.g. Henderson et al. 2002), as well as providing important minor component of the landings (Vaughan 2004). information on species’ occurrences and distributions (e.g. While sharks are opportunistically captured by fishers Henderson et al. 2005). Fishery-independent approaches on occasion (A. Henderson, pers. obs.), there is current- can, and have been, employed in regions were relevant ly no directed fishery for any elasmobranch species. commercial fishing activities do not exist, or when the live However, South Caicos, the island at the epicentre of release of study animals is desirable - for conservation the fishing industry is currently undergoing a transition reasons, or because the research question at hand requires toward a tourism economy (Zuidema et al. 2011), with it (e.g. Morrissey and Gruber 1993). the recent completion of the island’s first major hotel Unfortunately, even when the utmost care is taken, the and the transfer of most coastal public land to a private, capture, work-up and release of live animals tends to be at overseas developer. This will likely lead to a dramatic least somewhat invasive (e.g. Whitney et al. 2017). In the shift in the island’s demographics, coastal development, case of sharks and other elasmobranchs, the most common and increased pressure on marine resources (Davenport capture techniques are with baited hooks or demersal trawl. and Davenport 2006). Both approaches are known to induce capture stress (Dodd Relatively little is known about the elasmobranch and Duggan 1982; Skomal 2007; Brooks et al. 2012), and fauna of the Caicos Bank or the roles these species play hooks necessarily puncture the skin causing additional in the country’s coastal ecosystems. Previous elasmo- localised tissue trauma. Therefore, it is unsurprising that branch studies have investigated nearshore habitat post-release mortality has been highlighted as a matter of utilisation by juvenile lemon sharks Negaprion considerable concern (Heberer et al. 2010). Nevertheless, brevirostris (Henderson et al. 2010; Henderson et al. the physical capture of study animals is currently unavoid- 2016), but information on the presence of other species able when the collection of certain tissue samples is re- beyond the nearshore environment is lacking. Given the quired (e.g. blood), or when particular types of tags or other potential disturbance to local elasmobranch populations equipment must be attached to the study animal (see through increased fishing activity, water-based recrea- Hammerschlag et al. 2011). tion, and coastal development associated with the tran- Baited Remote Underwater Video Systems sition to a tourism economy (Juhel et al. 2018), the (BRUVS) offer an alternative, non-invasive and non- present study was established to assess elasmobranch destructive, approach to data collection in cases where diversity and abundance in areas that are likely to see specimen capture is not absolutely necessary (Cappo dramatic increases in human activity in the coming et al. 2003; Cappo et al. 2004; Santana-Garcon et al. years. The utilisation of BRUVS to address this goal 2014; Whitmarsh et al. 2017), e.g. when the research is has the added advantages of (a) providing a baseline primarily concerned with species occurrence and rela- visual record of the study sites that could be utilised in tive abundance (Espinoza et al. 2014). These systems future research, and (b) allowing species’ behaviours to use bait to attract nearby animals to a video camera, the be observed. footage from which is analysed post-deployment. This design is well suited to elasmobranch studies given the mobile, predatory nature of this taxon, and their highly- Materials and methods developed sense of smell. Indeed, BRUVS have been successfully utilised in a number of elasmobranch stud- This study was undertaken adjacent to South Caicos in ies, particularly in shallow, tropical environments (e.g. the Turks and Caicos Islands. The waters surrounding Environ Biol Fish Fig. 1 Elasmobranch species encounters on BRUVS deployed off South Caicos. The sampling site outlined on the left is referred to herein as ‘the Flats’ while the sampling site outlined on the right is ‘the Reef’ this island encompass a variety of environments includ- Park (ACLSNP), a circa 4 km2 Marine Protected Area ing coral reef, mangrove and seagrass ecosystems, as (MPA) in which all fishing activity is currently well sand flats and open ocean. The nearshore environ- prohibited, but which is open to boating and water- ment (mangrove forests, seagrass meadows, shallow based recreation. This MPA contains a number of dive sand flats) has been surveyed for elasmobranchs previ- sites with permanent moorings, which currently see only ously (Henderson et al. 2010; Henderson et al. 2016), so periodic use; however, as tourism on the island in- the present study focused on coral reef and deeper sand creases, it seems likely that boat traffic and diving flat environments. The study area was divided into two activity will increase dramatically throughout the sampling sites, namely a section of continuous fringing MPA. It is also possible that the boundary of the reef (‘the Reef’) to the south of the island, and a sand flat MPA, or its status, could be changed to facilitate eco- site (‘the Flats’) to the southwest (Fig. 1). nomic interests, as has already happened with the nearby The Reef is characterised by a variety of hexacorals, Bell Sound Nature Reserve. octocorals and sponges, interspersed with sandy patches The Flats are characterised by a predominantly sandy (Fig. 2a), ranging from a depth of approximately 2 m substrate with sparse seagrass, macroalgae and close to shore down to approximately 40 m at the drop- octocorals (Fig. 2b), and a depth range of approximately off. The boundary of this sampling site mostly follows 2–8