Shark populations have fallen sharply in British and international waters because of a fleet of trawlers laying thousands of miles of semi-permanent nets on the sea bed.
The fishery is believed to be netting at least 50,000 tonnes of sharks a year in 180-mile long gill nets. The sharks are taken mainly for their oil, which is sold to cosmetic and health food companies, but are also increasingly being sold to supermarkets for their meat, according to a report by a group of Irish, Norwegian and British government investigators.
The damage done to several shark species as well as to monk fish has been immense, says the report. In the past 10 years, it says, stocks of north Atlantic deepwater sharks have fallen to about 20% of original levels.
"The gill net fishery for deepwater shark represents a serious threat to the future of stocks ... recognised to be among the most vulnerable fish species known in the north Atlantic. The current level of effort seems far in excess of what could be considered sustainable," said the report.
The boats, owned by Spanish companies registered mainly in Britain, work British, Irish and international waters near St Kilda, the islet of Rockall and the area west of the Hebrides.
"It is quite frightening what they are doing. Each boat is probably landing about 100 tonnes of shark a trip. They are also discarding vast amounts. This is big business. Something needs to be done urgently," said Dominic Rihan of the Irish fisheries board.
Although the fishery is unregulated, it is not illegal to use gill nets to catch shark in these waters. "The only regulations that apply are on mesh size and quotas. Shark quotas in EU waters were only brought in last year and it is very difficult to follow what is being landed. There is no regulation on the amount of fishing gear they can use. There is serious unreporting of catches. It is madness," said Mr Rihan.
Stocks of several deepwater sharks found in the north Atlantic have reportedly fallen to 20% of original levels in the past 10 years. Leafscale gulper shark and Portuguese dogfish numbers have crashed by 80% in 10 years. These animals are listed in the world conservation union Red list as endangered. "The fishery is a criminal waste of a rare marine resource," said Ali Hood of the Shark Trust.
On Monday this week the UK authorities sent out the FV Kirkella, to determine the scale of the problem in UK waters for the first time, The Guardian reports.