Sharks Like To Hang Out, But Their Spots Often Overlap With Commercial Fishers'

Many shark species tend to congregate in the same areas as industrial fishing ships, a study finds. As a result, tens of millions of sharks in the open ocean end up caught either as food or bycatch.

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Every year, tens of millions of sharks get hauled out of the ocean by fishing vessels. Many are killed by accident. Others are targeted for their fins used in shark fin soup. NPR's Nell Greenfieldboyce has more on a new study of where sharks are especially at risk.

NELL GREENFIELDBOYCE, BYLINE: Sharks are incredible travelers.

DAVID SIMS: They undertake huge journeys across ocean basin scales.

GREENFIELDBOYCE: David Sims is with the Marine Biological Association in the United Kingdom. He says even though sharks can travel miles each day, they sometimes like to stay in one spot. To see exactly where they stay and go, over 150 shark scientists from around the world recently decided to collaborate.

SIMS: We wanted to really take this big-scale sort of global view of where sharks were hanging out.

GREENFIELDBOYCE: The team tracked almost two dozen shark species using satellite tags on over 1,500 individual sharks. They also looked at the movements of thousands of fishing vessels using data from a safety system that ships use to avoid collisions. It turns out that in any given month, about a quarter of the space used by sharks in the ocean overlapped with the space used by industrial fishing.

SIMS: But if we look at those species, which actually are most at risk, we see that the overlap values are much, much higher.

GREENFIELDBOYCE: Take blue sharks in the North Atlantic. Seventy-six percent of the space they used each month was also covered by longline fishing. Elliott Hazen works at NOAA's Southwest Fisheries Science Center. He says this study in the journal Nature provides a really detailed look at the risk to sharks.

ELLIOT HAZEN: What's really exciting about that is that in - sometimes, in the beginning of the year for many of the regions, many of these shark species are not at risk. There's not a high fishing exposure index. But then later in the year, sometimes into the summer, you start to get higher overlap.

GREENFIELDBOYCE: He says these results could be used to create new conservation strategies that protect both the economic benefits of fishing and the sharks.

Nell Greenfieldboyce, NPR News.

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