In what backers called a "historic" moment for EU fisheries policy, member states have agreed to ban the discarding of fish but with exceptions.

Though not the total discard ban sought by the European Commission and members of the European Parliament, the agreement announced Wednesday nonetheless represented the first time EU members had moved to officially limit discards, in which fish that can't be legally caught -- most often juveniles -- are thrown back into the sea, often to die.

The measure would require fishing fleets to carry out costly modifications to their equipment and change their methods so they don't accidentally catch prohibited fish.

The discard ban is essential in achieving the larger goal of sustainably managing and replenishing fish stocks and overfishing in EU waters, backers say.

The European Parliament took a hard line in a February vote, calling for a total ban to take effect 2015, one year later than sought by European Fisheries Commissioner Maria Damanaki.

Such a quick timetable, however, was opposed by the fishing industry and some EU members, such as France, Spain, Portugal and Malta, which contended it was unrealistic for their fleets to adapt quickly enough.

They pressed for a delay, and for the most part, got it under a five-year phase-in approach.

Irish Minister for Agriculture, Food and Marine Simon Coveney announced the results of the negotiations in Brussels after two days of hard bargaining among the members of the EU Fisheries Council.

"The discarding issue was always going to be contentious and resolving it difficult, not that there was any disagreement on the overall objective, but because there were divergent views on the associated management tools needed to make a discard ban a reality in practice," he said.

Under the agreement, a discard ban on pelagic species, such as herring and mackerel, would start in January 2014, but wouldn't take effect in the North Sea until 2016. The Mediterranean wouldn't be covered until 2017.

Meanwhile, the discard ban would apply to the main demersal stocks -- including such species as cod, haddock and whiting -- in the North Sea and the Atlantic North and South Western waters beginning in 2016.

Finally, the ban will apply to Mediterranean, Black Sea and all other EU waters beginning in 2017.

After the phase-in period, however, the new policy would allow discards for up to 7 percent of the annual catch under certain circumstances.

The measure now goes to a "trilogue" in which the European Parliament, European Commission and member states will try to agree on a final version to be voted on by the Parliament in an April plenary session.

"This is a historic moment in reforming the broken Common Fisheries Policy," British Fisheries Minister Richard Benyon said. "The scandal of discards has gone on for too long and I'm delighted that the U.K. has taken such a central role in securing this agreement.

"I am disappointed that some of the measures required to put this ban into place are no longer as ambitious as I had hoped but it's a price I am willing to accept if it means we can get the other details right."

Sweden, however, refused to back the agreement and several MEPs said they were disappointed by a lack of an outright ban on discards, the Financial Times reported.

Swedish Green MEP Isabella Lovin said Parliament would fight back against what she called the "gutting" of plans for a "more sustainable fisheries policy."