Fish prices have rocketed since the start of November when strong winds and torrential rain forced vessels and trawlers to a virtual standstill.
And with the unsettled weather expected to continue well into next week, the fishermen's union, the Cornish Fish Producers Organisation (CFPO), fears even greater losses of income.
Chief executive Paul Trebilcock said the situation was grim. "This prolonged period for the boats to be in is quite unusual," he said. "In the winter months you'd expect gales for a week or a few days but to have a three to four week period is quite unusual.
Unpleasant
"In the first week of November boats were at sea, but since then only a few of them have been going out.
"A few of the bigger boats went out last week, but came back in again. They said it was particularly unpleasant, and working conditions were difficult."
Supplies of freshly caught fish have started to dry up since the weather turned sour and prices have gone up by 20 to 30% in Newlyn. The price of monkfish and Dover sole has nearly doubled.
Andy Wheeler, of the CFPO, said: "Whenever the weather is poor, prices go up – it's not unusual.
"Monkfish and Dover sole can go up to £20 a kilogram compared to between £10 and £12."
The CFPO says the situation is the same across the South West, where some merchants have started to use their freezer stock or source from abroad to supply their customers.
"There has been very little fish on the market," Mr Trebilcock said.
"For three weeks they have not made any money so people are finding it very hard, and that creates problems. It's all pretty grim, so fingers crossed for better weather."
Newlyn fish merchant Robin Turner agreed. He said the weather had cost him thousands of pounds.
He said: "Basically it's a month with no income and I still have to pay my staff.
"It costs companies a lot of money to survive, it can be catastrophic. But hopefully it will be over by the end of this week."
But another Newlyn fish merchant, Nick Howells, believe things could be much worse. "Boats are catching up on other work," he said. "You get periods like this when there's not a lot on the market but most of them are getting on with things. We have been through this before and there's nothing you can do about it."
According to the Met Office, November rainfall up until November 24 was 167mm.
Forecaster John Hammond said: "Generally it looks like we are getting some more unsettled weather and there is no sign of any prolonged dry weather. In Newlyn winds are going to be strong and near to gale force with a mixture of showers and some clear spells."
article copyright WESTERN MORNING NEWS