A hunger for shark fin soup — a brothy, gelatinous dish that’s considered a delicacy in East Asia — is responsible for the deaths of about 73 million sharks each year. It was previously believed that many of these sharks were being caught in international waters, beyond the authority of any individual country, but a new study has upended this assumption: it found that fins were actually coming from sharks present in coastal waters, within countries’ exclusive economic zones.
“It definitely gives us new information we didn’t have before … [and] repositions where the problem is occurring,” lead author Kyle Van Houtan, chief scientist at Monterey Bay Aquarium, told Mongabay. “But it also may give us some challenges that we didn’t realize we had.”
Each country or jurisdiction has its own rules regarding the capture, trade and sale of shark fins. While many have outwardly banned the practice of shark finning — which involves slicing the fins off a shark, often while still alive, and then discarding the body — it can still be legal to take and sell fins from a shark that has been legally fished. And while some sharks can be legally traded across international borders, the trade of other species is either strictly regulated or prohibited.
But once fins have been skinned, dried and bleached in preparation for sale, it’s difficult to distinguish which species they came from, and whether they were acquired legally or illegally. The international nature of the trade also means that the fins can be moved around several times before ending up in a shop.
“Even if you have fins for sale in Vancouver or San Francisco, they very well could have gone through Hong Kong for processing at some point, and then shipped over to another market,” Van Houtan said. “Between reexport and transhipment … it’s really hard to understand where these [fins] come from.”
The new study, published Oct. 28 in Biology Letters, helps shed light on the intricate shark fin trade in two main ways. First, the team used DNA barcoding techniques to analyze 500 shark fin samples from four market locations — Hong Kong, Vancouver, San Francisco and northern Brazil — and identify which species they belonged to. While many samples came from oceanic species such as thresher sharks and hammerheads, most were identified as “requiem” shark species, such as reef sharks and silky sharks, which tend to live closer to the coast.
Second, the team generated species distribution models to show where many of these shark fins were likely coming from.
“Think of it as a heat map,” Van Houtan said. “Probably the most famous heat maps that people look at are precipitation maps on a weather application or a weather broadcast. It basically says where the rain is most intense, and where there’s no rain at all. It’s essentially the same thing that we’re doing [by] showing the greatest probability of the fishing activity — where it occurred to produce the pile of fins in that market.”
The study showed that the majority of shark fins came from the coastal regions of five countries: Australia, Indonesia, the United States, Mexico and Brazil.
“What our results say is that we haven’t been looking in the right places to combat this,” Van Houtan said, adding that previous conservation efforts have focused in the waters around Asia.
Co-author Stephen Palumbi, a marine biology professor at Stanford University’s Hopkins Marine Station in Monterey, California, said the species distribution models paint a global picture of the shark fin trade.
“What excites me about this is being able to take the data in … and add them all up, layer by layer by layer, and see a picture emerging,” Palumbi told Mongabay. “Yes, there are still lots of oceanic sharks in our data, and they’re still a huge conservation issue, particularly because they’re in danger. But there’s a lot of other species and they’re coming from lots of other places around the world, and in largely coastal areas.”
The findings present a double-edged sword for conservation. On one hand, they can help focus efforts to monitor and enforce fishing activities in coastal regions, Van Houtan said. But on the other hand, he said, doing so is easier said than done, especially when it comes to tracking fishing vessels by their automatic identification system (AIS) trackers.
“It’s not perhaps large ocean-going vessels, but a lot of vessels [that are] under 10 meters [and] don’t have to have AIS tracking,” he said. “We have our work cut out for us because … there’s a lot of enforcement gaps [with these vessels] in the US or beyond.”
Loren McClenachan, a marine ecologist at Colby College and fisheries management expert, said that shark finning isn’t the only problem for sharks. They are also threatened by overfishing for meat, recreational fishing, and getting caught as bycatch, she said. However, finning remains a major problem, and McClenachan, who was not involved in the new study, said its findings could help tackle the issue.
“Global markets for high value animal parts are notoriously difficult to monitor and regulate because it’s usually impossible to trace dried products like sharkfin back to an animal in the water,” McClenachan told Mongabay in an email. “High-tech approaches like genetic barcoding and niche modeling are key to solving this conservation problem. If we can correctly identify the locations of sharks supplying global markets, conservation efforts can protect vulnerable species in the water, where they’re at risk. The surprising result that much of the sharkfin in global markets comes from coastal sharks in a few key countries means that focusing conservation efforts in those coastal waters is essential.”
The more information that’s fed into these species distribution models, the more insights they can yield to help curb the illegal shark fin trade, Van Houtan says.
“I really hope it makes some progress for the wildlife trade,” he said. “It’s something which needs some good news.”
Van Houtan, K. S., Gagné, T. O., Reygondeau, G., Tanaka, K. R., Palumbi, S. R., & Jorgensen, S. J. (2020). Coastal sharks supply the global shark fin trade. Biology Letters, 16. doi:10.1098/rsbl.2020.0609
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