EU ministers are meeting to set fishing quotas for 2007 amid renewed calls for a total ban on catching cod.
British fishermen want a rollover of this year's imposed restrictions
The European Commission has recommended a 25% cut in cod and North Sea herring catches, lower plaice and sole quotas, and a six-month ban on anchovy fishing.
Scientists warned earlier this year that only a total ban on cod fishing would enable stocks to recover.
Environmentalists have urged ministers to listen to the warnings and "change course" on fisheries policies.
However, European Commission spokeswoman Mireille Thom told BBC Radio 4's Today programme that it was also important to consider the fishing industry.
"Obviously ending fishing... on cod would be most likely to give results, but we don't live in an ideal world," she said.
"We have a fishing industry in Europe and the EU is committed to ensuring the future of that industry and therefore the approach that has been chosen so far is a gradual approach, trying to balance the need to protect and rebuild the cod stocks and allow a degree of activity for the fishing fleet."
The talks are expected to continue for two days, with the haggling likely to continue into Wednesday night.
Outside the talks, demonstrators from the World Wide Fund for Nature dressed as chefs handed out restaurant menus for the year 2050 when they said the only fish meals available might be jellyfish and tofu cod.
British fishermen are calling for a rollover of this year's imposed restrictions, which reduced cod catches by 15%.
UK Fisheries Minister Ben Bradshaw has called the commission's recommendations for a 25% cut "drastic", adding that he did not believe any European states would support the proposal.
A few hours after the talks began, BBC Scotland reported that the commission had amended its proposal for a 25% cut in fishing days to 20% instead.
Chief executive of the Scottish Fishermen's Federation Bertie Armstrong said this was "still worrying", but pointed out it was only the first stage of the negotiations.
The European Commission says recovery plans for northern hake and Bay of Biscay sole have been working, and is proposing an increase in quotas.
It also says mackerel stocks are in good condition.
But it underlines scientists' warnings that "reductions in fishing pressure" will be necessary for the recovery of many other species, including cod, plaice, sole and southern hake.
The head of marine policy at the Royal Society for Protection of Birds, Euan Dunn, said fisheries ministers drove a stake deeper into the heart of the decimated cod stock every year.
"We urge them to have a vision of our waters as a fragile ecosystem, and to show the political will to protect it," he said.
The Madrid-based conservation group Oceana also urged the ministers to "change course in their fisheries policy and begin to consider the warnings arriving from all sides of the scientific world".
But Ms Thom pointed out that cod is caught by boats fishing for other species including haddock, whiting and prawns.
"If ministers were to decide that that's it, we're going to stop all catches of cod, then you have to stop all these fisheries," she said.
John Buchan, a fisherman based in Peterhead in Aberdeenshire, told the Today programme any further cuts would be devastating.
"We need every day out we can get. We just survived this year, on the days that we had," he said.
"If they cut it by 25% I can say this, no-one in the Scottish fleet would be viable."
Fishermen from Northern Ireland are also set to take an active role in the talks, with County Down-based trawlermen pushing for a 20% increase in their prawn catch.
Northern Irish prawn boats are currently allowed 220 days at sea but fishermen fear that number may now be reduced.