Quantifying Shark Distribution Patterns and Species-Habitat Associations: Implications of Marine Park Zoning

Simpfendorfer CA (2014) Quantifying Shark Distribution Patterns and Species-Habitat Associations: Implications of Marine Park Zoning. PLoS ONE 9(9): e106885. doi:10.1371/journal.pone.0106885 Quantifying Shark Distribution Patterns and Species-Habitat Associations: Implications of Marine Park Zoning Mario Espinoza 0 Mike Cappo 0 Michelle R. Heupel 0 Andrew J. Tobin 0 Colin A. Simpfendorfer 0 Christopher J. Fulton, The Australian National University, Australia 0 1 Centre for Sustainable Tropical Fisheries and Aquaculture and School of Earth and Environmental Sciences, James Cook University , Townsville, Queensland , Australia , 2 Quantifying shark distribution patterns and species-specific habitat associations in response to geographic and environmental drivers is critical to assessing risk of exposure to fishing, habitat degradation, and the effects of climate change. The present study examined shark distribution patterns, species-habitat associations, and marine reserve use with baited remote underwater video stations (BRUVS) along the entire Great Barrier Reef Marine Park (GBRMP) over a ten year period. Overall, 21 species of sharks from five families and two orders were recorded. Grey reef Carcharhinus amblyrhynchos, silvertip C. albimarginatus, tiger Galeocerdo cuvier, and sliteye Loxodon macrorhinus sharks were the most abundant species (.64% of shark abundances). Multivariate regression trees showed that hard coral cover produced the primary split separating shark assemblages. Four indicator species had consistently higher abundances and contributed to explaining most of the differences in shark assemblages: C. amblyrhynchos, C. albimarginatus, G. cuvier, and whitetip reef Triaenodon obesus sharks. Relative distance along the GBRMP had the greatest influence on shark occurrence and species richness, which increased at both ends of the sampling range (southern and northern sites) relative to intermediate latitudes. Hard coral cover and distance across the shelf were also important predictors of shark distribution. The relative abundance of sharks was significantly higher in non-fished sites, highlighting the conservation value and benefits of the GBRMP zoning. However, our results also showed that hard coral cover had a large effect on the abundance of reef-associated shark species, indicating that coral reef health may be important for the success of marine protected areas. Therefore, understanding shark distribution patterns, species-habitat associations, and the drivers responsible for those patterns is essential for developing sound management and conservation approaches. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: Funding for this analysis was provided by the Australian Governments National Environmental Research Program (Tropical Ecosystems Hub Project 6.1) awarded to MRH, CAS, and AJT. MRH was supported by a Future Fellowship (#FT100101004) from the Australian Research Council, and ME was supported by Australian Endeavour and AIMS@JCU Scholarships. This study is also an output of the Great Barrier Reef Seabed Biodiversity Project, which was funded by the CRC Reef Research Centre, the Fisheries Research and Development Corporation (FRDC), and the National Oceans Office, and led by R. Pitcher (Principal Investigator, CSIRO), P. Doherty (AIMS), J. Hooper (QM), and N. Gribble (QDPIF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Predicting shark occurrences and species-specific habitat associations in response to geographic, habitat and environmental drivers can be a powerful approach in regional conservation planning [1]. Distribution patterns of shark biodiversity are generally associated with latitudinal and bathymetric gradients [2,3]. Shark species richness typically increases toward the equator and peaks in shallow continental shelf waters (,200 m), where approximately 41% of all species occur [2,4]. However, the drivers responsible for shark occurrences and species-habitat associations can vary considerably between regions and are often poorly understood. While some species exhibit a strong association with particular habitats (i.e. coral reefs) [57], in general, most sharks tend to use a wide variety of habitats along the continental shelf [811], potentially acting as energy links in the transfer of nutrients from one system to another [12]. Therefore, understanding species-specific habitat associations over large spatial scales can be a valuable approach to identify important areas for shark conservation, as well as elucidate complex ecological processes such as connectivity within and across ecosystems. The Great Barrier Reef (GBR) is one of the most productive and globally important hot spots of marine biodiversity [4,13]. Within the GBR, elasmobranchs comprise a highly diverse group (134 species from 41 families) characterized by a wide range of lifehistory strategies [14] and varying degrees of vulnerability to both climate and anthropogenic pressures [8,11,15]. Sharks represent approximately 60% of the GBRs elasmobranch diversity and are thought to play a key role in the structure and functioning of marine communities through top down predation pressure on lower trophic levels [16,17]. However, several shark species are subject to fishing pressure (e.g. some species are taken intentionally, or as bycatch, in a variety of fisheries), which in some cases has resulted in significant declines in the abundance of reef sharks [1820]. Moreover, increased frequency of disturbances and anthropogenic activities within the GBR are having a major impact on coral reefs [21,22], and ultimately on reef-associated sharks. Therefore, knowledge of shark species ranges and habitat associations along the GBR must be understood to assess the risk of exposure to fishing, habitat degradation and the effects of climate change [15,23]. The GBR has the largest and most intensively managed network of Marine Protected Areas (MPAs) in the world, ranging from open-access (areas open to all human activities) to no-entry [24,25]. Approximately 33% of the GBRMP has been designated as no-take zones (areas closed to all forms of fishing), providing protection to a range of bioregions [24]. Marine reserve networks such as the GBRMP are thought to offer greater protection for mobile species by reducing their exposure to fisheries [25,26]. Although the benefits of MPAs for individual shark species have been poorly documented [5,2729], a variety of models and empirical studies suggest that spatial management approaches are critical for shark conservation [5,30], and ultimately may help maintain ecosystem resilience [31,32]. The use of fish habitats and s (...truncated)