Can sharks be fished sustainably?

Canadian filmmaker and conservationist Rob Stewartwas best known as a man who loved sharks.

The documentarian was filming in the Florida Keys when he disappeared during a dive earlier this month. Following a days-long search, his body was found last week.

Stewart was a vocal opponent of shark fishing. But just how big of a problem is the shark trade? New researchis looking at whether sharks can be fished sustainablyor if their catch should be banned altogether.

Why are sharks so important?

Sharks are crucial to the health of the oceans.They're an apex predator nothing eats them, but they eat a lot of other ocean-dwellers.Sharks often feed on sick and weak animals, thereby making those populations that much healthier.The sheer volume of biomass they consume has an impact on all animals underneath them on the food chain.

Take, for example, a shark preying on a particular population of tuna. If there are no sharks, all of a sudden the tuna populations explodes. This might be good for your local sushi restaurant, but it's disastrous for the ocean. Tuna will then decimate the populations of smaller fish,impacting everything right down to the plankton. You get the picture sharks are good!

What's the status of shark stocks?

There are almost 440 known species of shark. Some of them are considered threatened, while other species are considered healthy. The iconic great white?It's on the vulnerable list. The truly terrifying-looking daggernose shark? It's critically endangered.

The problem with trying to quantify anything that lives in the ocean is that we simply do not know enough about these creatures to make anything more than an estimate of populations.For instance, it is still unknown where great whites breed andwhere they nurse their young.It just goes to show how little we know about an animal that inspires such wonder and fear in humans.

Why do people fish sharks?

There's one main reason: shark fin soup.

Of the 100 million sharks killed every year, most are destined for shark fin soup. And though it's an important cultural food and status symbol in some Asian cultures, it has never been shown to have any medical benefit, let alone nutritional value.I'll repeat: the fin of the shark adds absolutely nothing to the flavour, nutrition or benefit of shark fin soup.

Sois there a way to make shark fishing sustainable? Researchers from James Cook University in Australia and Simon Fraser University in B.C. have teamed up to find out.

According to Nick Dulvy, one of the senior researchers, sustainable shark fishing is theoretically possible.

"We know from 60 years of fisheries theory that fisheries can be made sustainable," he said.

But the objection to sharkfishing is that they are too long lived, take too long to reproduce, and their numbers are too poorly understood to truly be confident in the sustainability of catching sharks.

So, can shark fishing be sustainable?

Researchers found hope that it can. After looking at a number of shark species, scientists realized that sustainable fishing is already occurring but often by accident.

"It turns out that there's a whole bunch of fish that are fished sustainably, but kind of by accident. It's just pure luck that they're sustainable. For example, blue shark out in the Atlantic are fished sustainably, but there isn't actually very strong management on those species," said Dulvy.

Surely it's not all good news?

No. There's reason to hope, but not without action.

Researchers found that in the European shark populations they surveyed, there weren't any examples of sharks that were fished sustainably. The only locations that had sustainable shark fishing were New Zealand, Canada, the United States and Australia not surprising considering these countries are generally associated with high regulation and oversight in everything that they do, including fisheries.

Only nine per cent of the shark populations they looked at a total of 47 different species are actually fished sustainably. Half of the healthy shark populations are considered sustainable because they are managed.

In other words, shark fishing can only be considered truly sustainable if it is carefullymanaged.

But the best way for you to protect sharks and their crucial role in the ocean?Don't eat shark fin soup.