Overfishing and climate change elevate extinction risk of endemic sharks and rays in the southwest Indian Ocean hotspot

PLoS One. 2024 Sep 5;19(9):e0306813. doi: 10.1371/journal.pone.0306813. eCollection 2024.

Abstract

Here, we summarise the extinction risk of the sharks and rays endemic to coastal, shelf, and slope waters of the southwest Indian Ocean and adjacent waters (SWIO+, Namibia to Kenya, including SWIO islands). This region is a hotspot of endemic and evolutionarily distinct sharks and rays. Nearly one-fifth (n = 13 of 70, 18.6%) of endemic sharks and rays are threatened, of these: one is Critically Endangered, five are Endangered, and seven are Vulnerable. A further seven (10.0%) are Near Threatened, 33 (47.1%) are Least Concern, and 17 (24.3%) are Data Deficient. While the primary threat is overfishing, there are the first signs that climate change is contributing to elevated extinction risk through habitat reduction and inshore distributional shifts. By backcasting their status, few endemic species were threatened in 1980, but this changed soon after the emergence of targeted shark and ray fisheries. South Africa has the highest national conservation responsibility, followed by Mozambique and Madagascar. Yet, while fisheries management and enforcement have improved in South Africa over recent decades, substantial improvements are urgently needed elsewhere. To avoid extinction and ensure robust populations of the region's endemic sharks and rays and maintain ecosystem functionality, there is an urgent need for the strict protection of Critically Endangered and Endangered species and sustainable management of Vulnerable, Near Threatened, and Least Concern species, underpinned by species-level data collection and reduction of incidental catch.

MeSH terms

  • Animals
  • Climate Change*
  • Conservation of Natural Resources*
  • Ecosystem
  • Endangered Species*
  • Extinction, Biological*
  • Fisheries
  • Indian Ocean
  • Sharks* / physiology
  • Skates, Fish*

Grants and funding

This contribution is part of the IUCN SSC Shark Specialist Group’s Global Shark Trends Project and was funded by the Shark Conservation Fund grant to NKD and Colin A. Simpfendorfer. The Shark Conservation Fund is a philanthropic collaborative that pools expertise and resources to meet the threats facing the world’s sharks and rays and a project of Rockefeller Philanthropy Advisors. PMK was supported by the Marine Biodiversity Hub, a collaborative partnership supported through funding from the Australian Government’s National Environmental Science Program (NESP). DAE was supported by the South African Institute for Aquatic Biodiversity, Save Our Seas Foundation grants 431 and 594, and the South African Shark and Ray Protection Project, implemented by the WILDTRUST and funded by the Shark Conservation Fund. RHB was supported by a grant (FED/2016/382-097/SVC-019 BIS) from the Indian Ocean Commission. CDS and HWK were supported by DAFF SA and funded by the Marine Living Resources Fund. NKD was supported by the Shark Conservation Fund and Discovery and Accelerator grants from Natural Science and Engineering Research Council and a Canada Research Chair. The National Research Foundation South African Institute for Aquatic Biodiversity provided in-kind support for the assessment workshop. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.