Refuges and risks: Evaluating the benefits of an expanded MPA network for mobile apex predators

Abstract

AimConcurrently, assessing the effectiveness of marine protected areas and evaluating the degree of risk from humans to key species provide valuable information that can be integrated into conservation management planning. Tiger sharks (Galeocerdo cuvier) are a wide‐ranging ecologically important species subject to various threats. The aim of this study was to identify “hotspots” of tiger shark habitat use in relation to protected areas and potential risks from fishing.LocationSouthwest Indian Ocean, east coast of South Africa and Mozambique.MethodsSatellite tags were fitted to 26 tiger sharks. A subset of 19 sharks with an average period at liberty of 197 (SD = 110) days were analysed using hotspot analysis to identify areas of core habitat use. The spatial and temporal overlap of significant hotspots with current and planned marine protected areas as well as risks from fishing and culling was then calculated.ResultsThere was a 5.97% spatial overlap between tiger shark hotspots and marine protected areas, which would increase significantly (p < .05) to 24.36% with the expansion of planned protected areas in South Africa and could be as high as 41.43% if Mozambique similarly expanded neighbouring protected area boundaries. Tiger sharks remained largely coastal, but only showed a spatial overlap of 5.12% with shark culling nets in South Africa. Only three sharks undertook open ocean migrations during which they were more likely to interact with longline fisheries in the region.Main conclusionsThis study demonstrates how spatial information can be used to assess the overlap between marine protected areas and the core habitats of top marine predators and highlights how congruent transnational conservation management can improve the effectiveness of protected areas. Core habitat use of marine apex predators may also be indicative of productive habitats, and therefore, predators such as tiger sharks could act as surrogate species for identifying key habitats to prioritize for conservation planning.

Satellite Tagging and Photographic Identification Reveal Connectivity Between Two UNESCO World Heritage Areas for Reef Manta Rays

“…While satellite tracking of tagged animals provides new insights into movements and habitat use, the integration and application of such data to conservation and management remains underutilised (Hays et al, 2016). Recent studies have showcased examples where movement data has informed aquatic conservation and management issues (Hays et al, 2019), including species stock boundaries and structure (Neilson et al, 2014), fishing mortality estimates (Byrne et al, 2017), identification of illegal and non-declared fishing vessels (Weimerskirch et al, 2020), and species behaviour and area utilisation (Schofield et al, 2013;Queiroz et al, 2016;Daly et al, 2018). Knowledge of species movements thus has the potential to provide valuable supporting information for the effective management of marine species.…”

Complex transboundary movements of marine megafauna in the Western Indian Ocean

“…The two sharks that were tracked for >60 days exhibited a divide in spatial use, with one remaining along the coast and continental shelf, while the second moved into the open ocean, similar to movements described in both Australia and the Hawaiian Islands (Papastamatiou et al ., ; Holmes et al ., ). Tiger sharks recently tracked off South Africa also demonstrated a mix of coastal and oceanic movements, however coastal movements were most prominent with relatively restricted spatial use (Daly et al ., ). The presence of tiger sharks in extremely shallow waters along the coast of Kenya as well as over the deep waters of the high seas highlights their vulnerability to multiple fishing operations.…”

“…Telemetry data voids are often the result of limited funding available for marine conservation work in conjunction with limited capacity that hinders both scientific research and ongoing compliance activities. However, new research in the WIO continues to become available (for example: Rohner et al ., and Daly et al ., ; published after the current meta‐analysis cut‐off date), suggesting that effort is being made to increase scientific knowledge in the region. Such studies are especially pertinent for the WIO to inform management as fisheries exploitation in both coastal and offshore waters are estimated to be approaching maximum harvest potential, yet uncertainty in catch data that limits stock assessments remains prevalent, further complicating efforts to manage many of these fisheries (FAO, ).…”

Identification of essential habitats: Including chimaeras into current shark protected areas

“…In the marine environment, marine protected areas (MPAs) or other forms of area closures are promoted as effective tools for protecting essential habitats, or hotspots of activity (Daly et al, ; Grüss et al, ; Lascelles, Langham, Ronconi, & Reid, ). However, MPAs are either general in conception or targeted at particular species, often because these are of economic or conservation importance (Lascelles et al, ).…”

“…Furthermore, for highly mobile species, MPAs are often planned with little prior knowledge of the species' spatial behaviour (Barnett, Abrantes, Seymour, & Fitzpatrick, ; Hooker et al, ). Therefore, identifying essential habitats within a species' broader distribution range is critical to assess if current MPAs are effective in protecting a given species (Daly et al, ).…”