By Alex Kirby BBC News Online environment correspondent

If you wanted to devise the quickest way of emptying Europe's seas, the Common Fisheries Policy (CFP) is hard to beat.

In its two decades, half of all North Sea fish stocks have fallen so low that they are at risk of collapse.

Member states use the CFP to protect their national interests. It does little for the notoriously unterritorial fish.

But the reforms proposed by the European Fisheries Commissioner, Franz Fischler, could prove a sea change.

The problem is brutally simple. Fish breeding rates remain roughly constant, while fishing technology improves by leaps and bounds.

Vanishingly elusive prey

So more and faster trawlers have been catching what fish they could find. Some European Union members catch fish far too young to breed, leaving a dwindling band of spawning fish.

Worries mount in the fish markets

The solution that Mr Fischler proposes is also essentially simple. He wants to reduce the effort that EU countries invest in fishing.

Presenting his proposals, he said: "The desperate race for fish has to stop.

"Over-capacity is the enemy - not only of the fish stocks, but also of the future of our fishermen."

There are practical steps that member states can take to reduce over-capacity, including:

• ending subsidies for building new trawlers, and paying crew members to leave the industry
• limiting the number of days the remaining vessels spend at sea
• putting spawning grounds out of bounds to allow the fish to reproduce
• using nets with larger mesh sizes or special panels to let juvenile fish escape.

Mr Fischler has already proposed some of these. Others are likely to be suggested later this year.

His proposals, conservationists say, are based on the idea that the state of the stocks should decide how much fishing will be allowed.

Protecting the whole

Dr Euan Dunn, of the UK's Royal Society for the Protection of Birds (RSPB), welcomes this clear statement of principle.

Dr Dunn told BBC News Online: "The single most important thing you can do environmentally is to go for a substantial reduction of fishing effort.

All marine species need protecting

"That's what Franz Fischler is doing, and it will help to alleviate pressure on the marine environment across the board," he said.

The RSPB wants a policy which protects fisheries as part of the entire ecosystem, concerned for sea mammals, birds and other creatures as well as commercially valuable fish stocks.

WWF, the global environment campaign, said the proposals did too little to protect the environment, and to cut the accidental catch of species like dolphins and turtles.

All to fight for

It also said they were too weak on "access agreements", which let the EU buy fishing rights from West African and other countries.

But Dr Dunn told BBC News Online: "I'd be very surprised if the proposals open the floodgates to an export of EU capacity to third countries. Brussels is aware of the danger.

"The plans are ambitious, a high-water mark for the CFP. The Commission has done its work, and the onus is now on the fisheries ministers.

"They've got a huge task. The coalition of southern EU states opposing Franz Fischler is very powerful, and I think there's going to be a real battle."