Shark deaths due to fishing have increased in recent years despite an international effort to reduce the harvesting of their fins, says a new study that included contributions from Canadian researchers.

The study, published in the journal Science, shows that the number of global fishing-related shark deaths rose to 80 million per year from 76 million between 2012 and 2019; however, during that same period the number of laws aimed at combating the practice known as shark finning 鈥� amputating a shark鈥檚 fins and tail before throwing the carcass back into the water 鈥� increased tenfold.

Around one-third of the sharks killed between 2012 and 2019 belonged to species facing extinction, study authors say.

鈥淭he number of threatened shark species around the world keeps going up, not down. So we need to do more,鈥� Dalhousie University biology professor and the study鈥檚 lead author, Boris Worm, said in an interview.

While some regulations around the world have successfully reduced shark mortality, increased deaths in other areas of the globe have offset that progress, he explained.

鈥淏ut we see some signs of hope that if you actually address mortality, not just finning, you can bring mortality down,鈥� he said.

Until now, no study had examined the effectiveness of measures to combat finning. Worm and other researchers examined shark mortality in the waters off 150 countries where the animals are fished, and deaths in open-ocean environments.

They found that coastal fishing was responsible for 95 per cent of all sharks caught and killed between 2012 and 2019. Mortality in these fisheries increased by four per cent in that time period. Meanwhile, mortality declined by seven per cent in offshore fisheries, especially in the Atlantic and western Pacific oceans.

Shark fins are highly prized in certain markets, particularly in Asia. While the crackdown on finning appears to have reduced the practice, it may have had the perverse effect of opening new markets for shark meat, study authors say. Now forbidden to harvest only fins, fishermen may be incentivized to sell the whole animal.

The researchers note an increase in demand for shark meat in countries such as Brazil and Italy. Because shark is a cheap substitute for other fish, study authors point out, the meat is often mislabelled and likely consumed unknowingly.

鈥淲e see these emerging markets for shark meat and shark oil and other shark products where we didn鈥檛 see them before,鈥� study co-author and Carleton University post-doctoral fellow Laurenne Schiller said in an interview. 鈥淚t really speaks to the fact that if you鈥檙e going to implement a regulation, you have to think about the potential for unintended consequences.鈥�

Highly effective measures to protect sharks are rare, the authors say. One such measure, Worm said, is a complete ban on their fishing. Another is strict regulations for fisheries to protect threatened species. Such a measure is already in place in Canada, where harvesters must release endangered species alive whenever possible, he explained.

Fisheries can also phase out indiscriminate fishing methods, for example by replacing equipment that catches sharks by mistake with gear that is more selective.

鈥淚f you look at shark health in any ecosystem, it鈥檚 a really good indicator of how healthy that marine environment is,鈥� Schiller said. 鈥淲hen we see this level of mortality and we see what鈥檚 working but also where we still need to 鈥� focus, we can think more critically about our role as humans in the protection of these species to hope for more resilient ecosystems into the future.鈥�

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