Fishing leaders have reacted angrily to proposals to cut North Sea haddock catch limits by 40% next year.
Fishermen argue that haddock stocks are healthy
A scientists' report to European fisheries ministers also calls for a total ban on cod fishing in the area.
The Scottish White Fish Producers' Association said there was an abundance of haddock and described the proposal as "totally unacceptable".
The Scottish Executive said the report was "disappointing" and promised to attempt to mitigate the impact.
The report was produced by the International Council for the Exploration of the Sea (Ices).
The scientists' findings will be considered by fisheries ministers when they meet in Brussels later this year to set next year's quotas.
Ices recommended reducing the haddock quota from 66,000 tonnes to 39,000 tonnes in 2006.
George MacRae, the secretary of the Scottish White Fish Producers' Association, said the recommendations came as a shock.
"There was no previous warning of this, no discussion with the industry and no consultation with those affected," he said.
"Everyone has regarded the haddock stocks as being in good condition.
"The catch reduction is not due to inadequate stocks of haddock, it is due to a different method of calculation by the scientists."
He said he hoped that Scottish Fisheries Minister Ross Finnie's "strong" support would continue - and urged his European counterparts to listen to the industry.
The association's chairman, Mike Park, added: "We are at a time just now when the white fish fleet depends on haddock and the profitability of the sector is very slow.
"Now we have got to sit down and discuss how this is going to be managed."
A Scottish Executive spokeswoman said it would look for "mitigating management measures to minimise any impact".
"This is a disappointing scientific response to the positive and responsible measures introduced by the Scottish fleet in recent years," she said.
"Before any new cod recovery measures are brought forward as a result of the Ices findings the European Commission must ensure other member states follow Scotland's lead by delivering on existing conservation commitments.
"Any change in approach must take full account of the continued viability of the industry."
Conservative fisheries spokesman Ted Brocklebank said the proposed cod ban was "clearly absurd".
"The current situation is preposterous," he said.
"Unelected scientists are telling unelected European bureaucrats what to dictate to elected Scottish ministers - and the Scottish ministers are accepting it all with a smile and a handshake."
Scottish National Party fisheries spokesperson Richard Lochhead urged Mr Finnie to stand up for Scotland's fishing industry during the Brussels negotiations.
"The scientists may paint the worst possible picture, but it is clear that slashing haddock quota would have dire economic consequences for Scotland," he said.
"Any cut in haddock quota of this scale would be the straw that breaks the camel's back for many vessels that already operate on the brink of bankruptcy."