Fishing leaders have called for government help after the coronavirus caused worldwide demand for seafood to fall drastically.
Jim Portus, of the South West Fish Producers Organisation, said markets for seafood had been "lost" in China, Italy, Spain and France.
In Newlyn, Cornwall, prices for pollock have dropped from £3 to 41p a kilo.
The Department of Environment, Food and Rural Affairs said it was "working closely" with the fishing industry.
Newlyn fisherman Jeremy Hosking said: "I rang our buyer and they don't want any landings of crab or lobsters.
"We have basically come unstuck overnight.
"We had six months of hardly any income and we are just about to start the season and the crisis is going to affect our livelihoods."
For some boats the cost of going to sea - fuel, crew wages, insurance and wear and tear - is now outweighing the return payment for the catch.
Newlyn fisherman Ryan Davey tweeted that he had to lay off seven crewmen. He added: "Well that's us tied up until this all blows over, prices on some fish down so low that with quota lease it cost us to catch it."
Well that’s us tied up until this all blows over, prices on some fish down so low that with quota lease it cost us to catch it! #msc hake prices low also and and big amounts will see the price of them drop very low as well. 7 men out of work......... pic.twitter.com/Jf3oFaij55— Ryan Davey (@Ryan_Davey1986) March 18, 2020
Cornwall fisherman Ian Jepson tweeted: "That's it. Game over."
That’s it. Game over. No shellfish market and I’ve just saw my first face mask 😷 in #newquay !! Stand by #cornwall. If any panic buyers need crab/lobster to go with all that rice and pasta you bought, call me 😂 #coronavirus sideaffects. No #fishing stay safe all x— F/V Three Jays ⚓️ (@ian_jepson) March 18, 2020
Paul Trebilcock of the Cornish Fish Producers Association said boats were curtailing fishing trips so that the market was not flooded.
"This isn't something that's going to be solved overnight," he said.
"And it's not just about fishermen, it's also about the communities they support."
Meanwhile restaurants have shut after people were advised to avoid social gatherings.
South West fish restaurateur Mitch Tonks tweeted that he was closing his eight Rockfish and Seahorse restaurants in Devon and Dorset to "take a part in the global fight against the spread of the coronavirus".
We have taken the difficult decision to close the Rockfish & Seahorse from Saturday. With the interests of our staff & customers utmost in our minds & actions we believe it's responsible thing to do. The full statements are here https://t.co/UqWUcfEmDg & https://t.co/jkEW23dVs0— MitchTonks (@MitchTonks) March 18, 2020
Barrie Deas, chief executive of the National Federation of Fishermen's Organisations, said he feared worse was to come.
There had been a "dramatic fall in prices for crab in China" as buyers faced "logistical difficulties and travel restrictions" triggered by the coronavirus, he said.
A spokeswoman for the Department of Environment, Food and Rural Affairs said: "We are talking to a wide range of representatives from the fishing and seafood industries and will work closely with them over the coming days and weeks."