The WWF has slated the EU Council of Ministers for not including compulsory measures in the final fisheries agreement thrashed out in Brussels in December.
The WWF warned North Sea cod were still under threat and criticised EU ministers for failing to put in place compulsory measures to protect young fish.
It questioned the EU's approval of voluntary protection measures. "Whether this will actually lead to fishermen avoiding cod at sea remains to be seen. It will only be effective if enough boats adopt the plans," said WWF senior marine policy officer Helen McLachlan.
"This year we saw the first glimmer of hope for numbers of cod in the North Sea in many years. 2008 will be a major challenge for governments and fishermen to prove they are able to help recover this stock."
However, the Scottish Fishermen's Federation (SFF) welcomed the deal, which would allow Scotland to push ahead with a flexible management regime to ensure the number of days boats can go to sea remains unchanged for 2008.
The EU agreement sees reductions in days at sea for the West Coast of 10% to 18%, depending on mesh size, and 10% for the North Sea.
But the decision to give the go-ahead for the first time to a Scottish-administered conservation scheme will enable boats to gain back lost days in exchange for targeted cod avoidance measures, the SFF said.
This approach includes real-time area closures to fishing, more selective nets to allow smaller fish to escape and independent observers on boats.
"We welcome that a Scottish-administered scheme has been agreed, which will provide flexibility to effort management and provide incentives for skippers to adopt targeted and effective conservation measures," said SFF chief executive Bertie Armstrong.
"For the West Coast, the quota for Rockall haddock was increased substantially by 50%; the West of Scotland cod quota is down by 18% and megrim is unchanged.
"The quota for West of Scotland herring has been reduced by 20%."