A major new report has called on the UK government to ban fishing in a third of UK waters to conserve fish stocks.
Prof Sir Tom Blundell: "Seas are being challenged"
The Royal Commission on Environmental Pollution (RCEP) also wants to see a ban on deep-sea trawling and a smaller fishing fleet.
The report's author, Professor Sir Tom Blundell, said the dramatic decline in the state of the British marine environment meant drastic action was now needed.
"Our seas are being challenged; the home of Nemo that we've seen in the cartoon recently is just being removed in many places," he told BBC News.
"Trawling scrapes the bottom; we fish down the fish chain, taking out the large species. We have huge bycatches - 30%, sometimes 50%. This is simply not sustainable."
The commission's report - Turning The Tide, Addressing The Impact Of Fisheries On The Marine Environment - echoes many scientific studies and statements.
The International Council for the Exploration of the Seas (Ices), the body that advises EU ministers on the state of stocks, has once again urged a total ban on cod fishing in the North Sea, the Irish Sea and west of Scotland in 2005.
One recent scientific model of the North Sea's ecosystem suggested the total stock of fish in the region had dropped from 26 million tonnes to 10 million in just over a century.
The UK's fishing industry has already been scaled back in recent years as EU fisheries policies have sought to preserve stocks.
The RCEP recommendation that the industry should now face further restrictions on "fishing effort", with many more boats decommissioned and large areas of UK waters put out of bounds is already being fiercely opposed.
The trawling industry has little faith in the science community's ability to judge the true state of fish stocks.
"We halved our whitefish fleet two years ago and the half that is left is fishing on half time. The idea that we have done nothing is absolutely nonsense; we've done a great deal," Hamish Morrison, chief executive of the Scottish Fishermen's Federation told the BBC.
UK MARINE LIFE
Over 44,000 species, from plankton to whales
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"I think there is a problem with timing. Scientists are always working two years behind the game. This is manifestly the case with this report.
"These recommendations won't happen because you are asking other European countries to accept closed areas and loss of fish, and there won't be a majority for it in the Council of Ministers."
But Professor Callum Roberts, a marine conservation biologist at York University and adviser to the RCEP, said changes were still required.
"At the moment many of the methods we use to catch fish [such as bottom-trawling] destroy habitats in the process. People have likened it to clear-cutting a forest to catch squirrels," he said.
"If we were to use more environmentally sound methods, like hook-and-line and traps to catch fish, then it would have much less impact.
NORTH SEA RESERVE NETWORK
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"We have seen the British fishing industry in steep decline since the 1980s; the number of people employed, the number of vessels out there, the number of fish landed - all have gone down.
"The reason is the current management of the fisheries is simply not working."
The UK fisheries minister, Ben Bradshaw, seems unlikely, however, to support the closure of 30% of UK waters.
He told the BBC that to pursue such a policy would probably put the Scottish whitefish industry out of business.
"There are signs that cod has stopped declining and other stocks like haddock are at record highs.
"It doesn't seem reasonable to take action that puts fishermen and fishing communities out of business and then the stocks recover and you have no fishing industry left to take advantage of that.
"I don't think we would want to put our fishermen out of business when, for example, haddock stocks are at a 30-year high and shellfish and herring are doing very well."
Range of measures
Charles Clover, author of The End Of The Line, a look into over-fishing across the world, said there was good evidence that marine reserves could benefit fisheries in the medium to long term.
"People are talking about these closures being unrealistic; they're not. The eastern US had a particularly bad problem in the 1980s - they were where we are now. They closed huge areas. They brought back the fish stocks - they brought back the cod, the haddock, the flounder and the scallops."
The European Commission will put forward its own proposals on reforming EU fisheries policy on Wednesday. This will include significant closures in the northern part of the North Sea, part of the southern North Sea and areas off the Iberian peninsula.
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John Farnell is the EU's director for fisheries conservation. He said the commission was set to approve reforms that would include the closure of the best 40% of cod-fishing areas in the North Sea.
"We certainly think closed areas can play a role in conserving fish stocks but those measures have to be combined with other measures that are already part of the reformed CFP."
He said the RCEP's idea for a 30% closure of UK waters had the look of a "blunt instrument".
"I would be a little surprised if similar proposals were made for closing 30% of the UK landmass to farming in order to improve biodiversity. We have to avoid simple, single solutions to fisheries management."