A recent analysis published in Nature documents a dramatic, and ongoing, global decline of oceanic shark and ray populations by nearly three-quarters (71%) over the past 50 years, primarily due to overfishing.
This decline coincides with a tripling of catches, amounting to an 18-fold increase in Relative Fishing Pressure (exploitation relative to the number of fish left).
Worrying risk of extinction
For all 31 oceanic shark and ray species analysed, the risk of extinction has increased substantially since 1980.
Three-quarters (75%) of these iconic species now qualify as threatened with extinction under the International Union for Conservation of Nature (IUCN) Red List criteria.
Falling short of UN Sustainability and Biodiversity Goals
The authors calculated two Biodiversity Indicators established by the United Nations Convention on Biological Diversity: The Living Planet Index (LPI) on global population changes since 1970 and the Red List Index (RLI), which tracks changes in the relative extinction risk of species taxa.
These indicators quantify progress toward the UN Sustainable Development Goals (SDGs) and specific Aichi Biodiversity Targets (to reverse population declines and use marine resources sustainably), neither of which were met for these species in 2020.
Key to the analysis was use of the very elegant statistical trend analysis software - Just another Redlist Assessment (JARA) - which was conceptualised and developed by JRC scientist and co-author of the study, Henning Winker.
While there are numerous pressures on sharks and rays, every single Red List assessment for the 31 species concluded that the major threat was “Biological Resource Use” and, more specifically, “Fishing and Harvesting Aquatic Resources” – i.e. overfishing.
The catch of oceanic shark and rays has increased three-fold since 1970. Around 1990, a dramatic rise in catches coincided with increased retention of sharks to meet growing international market demands for meat, fins, and gill plates.
Glimmers of hope show that conservation measures work
While the study highlights the urgent need for action, there are also a few signs of hope, as “Great” White Sharks and Northwest Atlantic Hammerhead Shark populations are showing signs of recovery, thanks largely to strictly enforced conservation measures.
Recommendations for policymakers
To avert population collapse and myriad negative consequences for associated economic and ecological systems, the authors call for strict prohibitions and precautionary science-based fishing limits.
Such action is imperative for functioning ecosystems, long-term sustainability, and economic benefits.
- Half a century of global decline in oceanic sharks and rays
- Just another Redlist Assessment (JARA)
- Red List Index (RLI)
- Living Planet Index (LPI)
- 3 mars 2021