Overfishing caused global numbers of oceanic sharks and rays to fall 71% in past 50 years

A devil ray, one of the oceanic rays in decline worldwide due to ovefishing, at a fish market in Sabah in Malaysia. PHOTO: PETER KYNE

SINGAPORE - Global numbers of oceanic sharks and rays have plummeted 71 per cent over the past 50 years, a new study by an international research team has found.

The decline since 1970 is primarily due to overfishing, say the researchers of their paper published in January in the scientific journal Nature.

One of the study's authors, Dr Peter Kyne of the Charles Darwin University in Australia, said the biology of these species limit how fast they can reproduce and therefore sustain fishing pressure.

"These large species mature at a late age, and typically have few young. Some species may reproduce only every second or third year," he said.

It is their strategy to produce fewer but larger offspring that will face fewer potential predators than smaller babies. "Their individual chance of survival is high in the absence of fishing," Dr Kyne said.

But humans and their appetite for meat, fins and gill plates are driving these species to extinction.

Commenting on a new Singapore study which had found that many processed and cooked fish products were of threatened elasmobranch species, Dr Kyne said there was overlap between species in his pelagic paper and those detected in the Singapore study.

For instance, the Singapore researchers found that many samples here were of devil fish and silky sharks. They also found manta rays, hammerheads and thresher sharks. These were all species that experienced sharp declines in numbers, Dr Kyne said.

But his team had found some bright spots, with white sharks and porbeagles - a type of shark - showing signs of recovery due to fishing restrictions.

He said for places like Singapore where most of the shark products are imported, strong monitoring of imports is required to ensure compliance with Cites regulations. Cites is the Convention on International Trade in Endangered Species of Wild Fauna and Flora, which Singapore is signatory to.

In 2017, a report by wildlife trade monitoring group Traffic and conservation group World Wide Fund for Nature found that Singapore was the third largest importer of shark fin after Hong Kong and Malaysia.

"Using genetic barcoding to detect mislabelled and potentially illegally traded species is an important tool for monitoring, compliance, and enforcement," he added.

Consumers can also help by not eating products made from highly threatened species.

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