“The biggest threat to sharks is overfishing,” says Koehler. “That includes commercially targeted fishing, but also bycatch. This is where they don’t intentionally go for sharks – but due to the gear they use and the places they go, they do catch a lot of sharks. And they land them, and market them.”
Bycatch is one of the five biggest threats to life in the ocean, and sharks are amongst the most vulnerable. It’s not known how many sharks are killed by commercial fisheries every year but the number is thought to be in the hundreds of millions.
Bottom trawling is a particularly destructive method of fishing, says Koehler. “A heavy net, that’s weighed down, is dragged across the seafloor,” she explains. “You can imagine how much damage that does to the fine sponges, the corals, all those really fragile ecosystems. You basically remove them. And what you’ve got left is just a bare field of nothing.”
Everything in the fishers’ path is scraped up from the ocean floor, not just the target species but any species that happens to be there.
“Bottom trawling demolishes the benthic ecosystem. The whole food web – decimated,” adds Weber, “And a lot of these species that live on seamounts are very slow-growing. They have very slow life histories. Then these boom-bust fisheries turn up and go, ‘Whoa, there’s loads of fish’. They scoop them all up, and they’re gone.”