Deep-sea sharks threatened by overfishing, study warns

Professor Nick Dulvy remembers the collapse of the northern cod fishery in 1992.

“It’s been nothing short of a social and economic disaster for Canada,” said the biology professor at Simon Fraser University in Burnaby, British Columbia.

For this holder of the Canada Research Chair in Marine Biodiversity and Conservation at this university, and for other researchers, the “notorious” events of that year offer historic lessons on unsustainable fishing practices that still resonate today.

Professor Dulvy is among researchers around the world sounding the alarm about threats to deep-sea sharks and rays from overfishing and international demand for liver meat and oil shark.

The Canadian researcher contributed to the writing of a study published Thursday in the journal Sciencewhich highlights the need to immediately regulate international trade and fishing to avoid “irreversible” consequences.

Ordinary people are mainly interested in more “charismatic” shark species, such as the hammerhead shark, the great white shark or the mako, but deep-sea species are threatened due to improvements in fishing technologies, underlines Professor Dulvy.

“There is increasing awareness of coastal shark issues and it is much easier to attract public attention and get policy makers to make changes based on these more charismatic species,” he said. he declares.

“But it’s very easy to forget what’s going on in the deep ocean, and we hear a lot about mining in the deep ocean. But the reality is that the biggest threat to the ocean depths we face today is overfishing. »

As coastal waters around the world shrink, the drive to fish deeper means shark and ray populations become “collateral damage” in commercial fishing activities.

Deep-sea shark species, he said, play a “poorly understood but important role in regulating deep ocean ecosystems.”

Deep-sea sharks are targeted for their liver oil, and today the substance is found in a number of everyday consumer products, he says. “If you ask anyone about it, they will never have heard of it, but the reality is that we have probably all used or ingested it. »

Shark liver oil is thus used in cosmetics and nutritional supplements, “nutraceuticals” and even in vaccines, explains Professor Dulvy. “No one really has a choice whether or not to use liver oil because the product is not labeled in any way. »

Regulations to stem the trade in shark fins and manta ray gills have progressed, and Mr Dulvy says “now is the time to really draw attention to the plight of deep-sea sharks as a result of the trade.” international level of their liver oil.

“The trade in shark liver oil has been little studied and is overshadowed by the more visible global trade in shark fins and rhino rays, devil ray gills, and their meat,” says the ‘study. “Shark liver oil is one of the most widely used shark products. »

The study points out that deep-sea species were “very little threatened” before 1970. But a change “coincided with the advent and expansion of most deep-sea fisheries” – the number of threatened species increased more than doubled in just 25 years, between 1980 and 2005.

The research ends with both a warning and a call to action to regulate the shark liver oil trade, which Dulvy says will allow future generations to gaze upon some of these “super cool organisms.” .

“We have the evidence to act more proactively on behalf of the deep ocean and learn from the mistakes that have led to more than half of coastal and pelagic species being threatened,” the scientific article concludes.

“Effective precautionary measures are needed to ensure that the largest ecosystem on the planet maintains its biodiversity and that half of the world’s shark and ray species are protected from the global extinction crisis. »


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