Blue and Mako sharks, the main types of sharks found in Britain are being killed on their routes across the Atlantic by 60-mile (96 kilometre) fishing lines armed with hooks used by Iberian fishing fleets.
As many as three to four million sharks are being killed annually by the longline fishing, the UK's Sunday Times reported recently.
Tourists and shark anglers in Cornwall in the UK's west used to catch thousands of sharks annually, and now only catch hundreds.
"We found that the sharks are congregating where warm and cool currents meet. These are highly productive areas that attract fish – and that attracts sharks too," David Sims, professor of marine ecology at the MBA, told the Sunday Times.
Fishing vessels also find themselves in these waters, where overfishing poses a problem to vulnerable species of fish.
At the rate in which these vessels fish, fish populations do not have enough time to breed, Sims said.
"The basic problem is not really one of Spanish and Portuguese fleets 'stealing' sharks from the UK: it's that the European Union still doesn't have a management plan for sharks," Alex Bartoli of the Shark Alliance told The Local.
"Fleets fish for tuna and swordfish in these areas and sharks are a secondary capture. But there are no limits on the number of sharks captured or on the size of the fish that can be taken," he explained
The Shark Alliance, a group of non-governmental organizations, has repeatedly called for closer regulation of shark fishing in the EU in a bid to protect the animals.