A new global study blames overfishing for a more than 50% decline in sharks and rays since 1970, but also shows a clear path to preventing their numbers dwindling further.
James Cook University's Professor Colin Simpfendorfer was co-author of the analysis, published today in the journal Science.
He said it reveals overfishing has caused populations of chondrichthyan fishes – sharks, rays, and chimaeras (closely related to sharks) – to decline by more than half in the past 50 years.
"In addition to intentional targeting and bycatch, the threat to sharks is compounded by habitat degradation, climate change and pollution. The result is over one-third of chondrichthyans now face the threat of extinction," said Professor Simpfendorfer.
Lead author Professor Nicholas K. Dulvy from Simon Fraser University in Canada said the study shows how declines first occurred in rivers, estuaries and nearshore coastal waters before spreading across the oceans and then down into the deep sea.
"The sequential depletion of the largest and most functionally important species – such as sawfishes and rhino rays – was followed by the decline of large stingrays, eagle rays, angel sharks, hammerheads and requiem sharks. Eventually, fisheries turned to deep water sharks and skates for the liver oil and meat trade," said Professor Dulvy.
Professor Simpfendorfer said despite the alarming trends, the analysis illuminates a clear path to a solution.
"Nations can reduce the extinction risk by lowering fishing pressure to sustainable levels, strengthening fisheries governance, and eliminating harmful subsidies.
"Progress has already created bright spots of hope for chondrichthyans, including in Australia, Canada, New Zealand, United States, and parts of Europe and South Africa," he said.
Professor Simpfendorfer said chronic underassessment and undermanagement of fisheries is widespread, particularly in countries with weaker governance.
"Science-based fisheries catch limits and measures to minimise incidental catch, including spatial protections, are essential to ensure sustainability and to recover species to their ecological, social, and economic potential.
Link to study here. (Available after embargo lifts at 5am Friday 6 December AEST)
