By Jeremy Cooke
BBC rural affairs correspondent
The UK fishing industry is warning it faces ruin because of EU quotas which result in thousands of tonnes of dead fish being dumped back into the sea.
Phil Walsh's crew exceeded their cod quota by June
It says fishing crews often continue catching large amounts of fish such as cod by accident after exceeding quotas - and have no option but to dump them.
Ministers are pushing for a quota increase to help solve the problem.
But environmentalists have called for a change in practices, such as avoiding areas with large numbers of white fish.
European Union quotas strictly limit the amount of fish that vessels can bring back to port, but there is no restriction on the amount of fish they actually catch.
As a result, boats fishing in the "mixed fishery" of the North Sea often catch a species or size of fish which is above their quota and have to throw the "discard" back.
The EU estimates that between 40% and 60% of fish caught by trawlers in this area is dumped back into the sea.
Trawler skipper Phil Walsh told BBC News he had landed all of the cod he was allowed by June this year.
Since then, he has been fishing for prawns and dumping prime whiting, haddock and cod, which would fetch as much as £13.50/kg on a supermarket shelf.
"I can't describe the feeling really," he said.
"It's your livelihood and you spend your life trying to catch it and then you have to throw it back over the side.
"It's an impossible situation and, unless it is sorted out soon, we will all be finished."
Many Scottish and English fishermen say they have seen a huge increase in the number of cod in the North Sea this year and now want an increase in the quota level for cod and other white fish they catch.
Decline in numbers
But environmentalists, who have for years been sounding the alarm bell over the decline of North Sea fish stocks, say now is not the time to increase the amount being caught.
They say quotas are essential to ensure spawning stocks are allowed to mature and to breed.
But, like the fishermen, activists such as the World Wildlife Fund's Helen McLachlan agree that throwing dead cod back into the water is not the answer.
Instead, she said, there must be a change in fishing practices.
"Nobody wants discards," she said.
"So let's not catch the fish in the first place.
"Let's avoid areas where there are going to be large spawning stocks of fish, let's avoid juveniles... let's use selective gear so [a fisherman can say], 'I will only catch prawns, I will not catch white fish'."
Oliver Knowles, a campaigner for Greenpeace, also believes quotas are not working for the UK's mixed fisheries.
He told BBC Radio 4's Today programme: "By the government's own figures, of the 186 million fish caught in UK waters last year, 117 million of them were thrown away dead as waste.
"That's actually 63% of the catch, so it's clear that we do need to do something about this."
But he added that some kind of limit was needed.
The Scotland-based super-trawlers, with their state-of-the-art technology, say they find it hard to be 100% specific in targeting the species and size of their catch.
And so they, like the hard-pressed inshore fishermen south of the border, continue to discard huge amounts of good fish.
"I feel very bitter because we've been so long trying to protect the cod," said trawler skipper David Mell.
"[We've had] decommissioning, increased our mesh size, we've been through a lot of pain really.... [But] I thought I would never see the day that I had to throw adult cod overboard."
Fisheries Minister Jonathan Shaw said he agreed it was an "absolute waste" to throw good quality fish back into the sea.
He told the Today programme he would be pushing for an EU quota increase as well as looking at technological solutions, such as nets that would catch only certain kinds of fish.
"What is important is we have fish tomorrow as well as today," he said.
"We have seen a recovery in cod in the North Sea in particular - now that is good news.
"So that is why we will be pressing the commission at the annual round in December for an increase in cod and hopefully that will help the fishermen."
EU Fisheries Commissioner Joe Borg - who is instrumental in setting the laws and limits - agreed that discarding fish was "immoral" but said there was no clear solution.
"The problem is when we come to work out the details of how to eliminate discarding but at the same time have sustainable fisheries - that is the big problem."