A new study published in Science reveals that overfishing has led to a dramatic decline of over 50% in the populations of sharks, rays, and chimaeras since 1970. Researchers have developed the Aquatic Red List Index (RLI), which indicates a 19% increase in extinction risk for these species. The findings highlight that the overfishing of large species in coastal and pelagic environments threatens up to 22% of ecological functions.
Chondrichthyans, an ancient and diverse group of over 1,199 species, face growing threats from targeted fishing, bycatch, habitat degradation, climate change, and pollution. One-third of these species are now at risk of extinction.
The study emphasizes that shark and ray populations have declined progressively, first in rivers and estuaries, then across oceans and into the deep sea. The depletion of the largest and most functionally vital species, such as sawfishes and rhino rays, has been followed by declines in hammerheads, requiem sharks, and stingrays.
This decline disrupts marine food webs and compromises ecosystem functions. Sharks play a critical role as apex predators, while rays contribute to sediment oxygenation and marine productivity.
Despite these challenges, positive conservation trends offer hope. Effective solutions include reducing fishing pressures, strengthening fisheries governance, and eliminating harmful subsidies. Bright spots of progress are emerging in countries like Australia, Canada, New Zealand, and parts of Europe.
The RLI serves as a vital tool for governments to monitor biodiversity conservation efforts and guide future initiatives, ensuring sustainable management of ocean ecosystems.
