by Matt Kieltyka, Simon Fraser University
Scientists from Simon Fraser University are part of an international team of researchers that has developed a new science-based indicator to assess the state of health of the oceans—and the possible risk of extinction of their species.
Recent biodiversity studies show an unprecedented loss of species, ecosystems and genetic diversity on land, but the extent to which these patterns are widespread in the oceans is not yet known.
In a new study published recently in the journal Science, researchers from Spain-based AZTI Technology Centre, in collaboration with SFU and the International Seafood Sustainability Foundation (ISSF), have developed a global indicator that measures the state of marine biodiversity based on changes in extinction risk recorded over seven decades in oceanic predatory fishes (52 populations of 18 different species of tuna, billfish and sharks).
The study reveals how, since the 1950s, the global extinction risk of oceanic predatory fishes has continuously worsened due to excessive fishing pressure until the late 2000s.
The results offer some hope after the global rebuilding of commercially important tuna and billfish species yet reveal a problem in the management of sharks captured incidentally by the same fisheries, showing the urgency of implementing actions to prevent their increasing risk of extinction.
Then, the implementation of management measures in international fisheries organizations effectively reduced fishing mortality, recovering tunas and billfishes. Yet the extinction risk in the undermanaged sharks continues to rise.
“It’s encouraging to see we’ve been able to halt declines of tunas and billfishes but the decline of sharks continues,” says SFU’s Nick Dulvy, distinguished professor and Canada Research Chair in Marine Biodiversity and Conservation.
“If we don’t do anything to mitigate overfishing and lack of effective management, the loss of these species threatens the balance of ecosystems and risk of food security and jobs in both developed and developing countries.”
The study’s authors believe it’s possible to replicate the successes of tuna and billfish fisheries management for sharks. They say oceanic sharks urgently need better management and protection from overfishing, by regulating trade, redefining priorities in international fisheries bodies and settling clear biodiversity goals and targets.
Implementing science-based catch limits and changing how and where gear is deployed can avoid and minimize the incidental catching of sharks, the study finds. This week’s CITES meeting in Panama offers a unique chance to regulate 90 per cent of the global shark fin trade.
Reference (open access)
MARIA JOSÉ JUAN-JORDÁ, HILARIO MURUA, HARITZ ARRIZABALAGA, GORKA MERINO, NATHAN PACOUREAU, AND NICHOLAS K. DULVY. 2022. Seventy years of tunas, billfishes, and sharks as sentinels of global ocean health. Science, Vol 378, Issue 6620 DOI: 10.1126/science.abj0211
