By Alex Kirby
BBC News Online environment correspondent
The fishing industry must change if many of the familiar fish round the UK coast are to stand any realistic chance of survival, Prince Charles has said.
The fishing industry faces a stormy future
He told a charity promoting sustainable fishing that overfishing threatens once-abundant species with extinction.
People should not stop eating fish, but should only eat species which were not in decline, the prince added.
Nine former UK environment secretaries and the present incumbent all say world fish stocks are collapsing already.
'Lessons are obvious'
The prince was speaking at a gala event to raise money for the work of the Marine Stewardship Council (MSC), which says it is the only global charity working exclusively to save global fish populations.
It seeks to do this by awarding its label to fisheries it judges sustainable: seven have been certified so far, and more than 40 others are at some stage of the certification process.
Prince Charles said that with cod stocks in the North Sea now at one tenth of the 1970 level, the "lessons are obvious".
But he insisted that asking people to stop eating fish altogether was not the answer.
"Nor would a so-called boycott achieve anything worthwhile," the prince said.
"There are undoubtedly some species of fish that are so threatened, and some fisheries that are so damaging, that we should try and avoid them completely, but neither of those things applies to any of the sort of wild fish widely available to consumers in this country."
The European Union agreed a contentious deal on fishing quotas last December intended to reverse the decline in several species.
A report due out soon from the Prime Minister's strategy unit is expected to urge radical restructuring of the UK's fishing industry, including the decommissioning of more boats.
Today's abundance belies tomorrow's scarcity
The prince wants consumers, supermarkets, fish processors and the fleets themselves to opt for sustainable fisheries, both to conserve the stocks and to save jobs.
Last month he said: "In addition to good science and good regulation, we need a system that harnesses the power of the consumer and provides economic incentives to well-managed fisheries.
"That is exactly what the MSC does, and that is why I have been such a strong supporter of its work right from the start."
Backing for the MSC also came from former environment secretaries and their serving colleague, Margaret Beckett.
In a letter to the London Sunday Times, they wrote: "The collapse of our fish stocks is no longer a distant nightmare. It is a present reality.
"Rich fishing grounds such as Canada's Grand Banks now yield no catch at all. In the English Channel, the North Sea and the Baltic, many stocks are in terminal decline.
"As our traditional fishing areas become less productive, so effort moves further afield, and the markets of the rich take fish that was destined for the poor, for whom it is the only source of protein."
Consumers are asked to avoid endangered fish
The MSC chairman, John Gummer, one of the letter's signatories, said: "If we allow species to be destroyed we are basically stealing from future generations."
But Barry Deas, chief executive of the National Federation of Fishermen's Organisations, is critical of the MSC.
He told the Sunday Times: "Fisheries are highly complex... It is impossible to go in and define a single fishery as sustainable in a way that is meaningful to consumers."
One industry source told BBC News Online: "I think the MSC is all smoke and mirrors on accreditation.
"One of the seven fisheries it's certified, the New Zealand hoki, wasn't properly assessed as far as I know."
Brendan May, the council's chief executive, told BBC News Online: "Our certification process certainly isn't smoke and mirrors - it's one of the most robust systems of auditing there is for any commodity.
"There's no such thing as a perfect fishery. What we're about is not perfection, but what is actually sustainable."