Sales of mackerel in the Westcountry have fallen after the Marine Conservation Society (MCS) removed the popular fish from its list of those suitable to eat.
The South West Handline Fishermen's Association said fishmongers' customers had taken the advice to heart.
And association secretary David Muirhead said the society's comments, made last month, had hit a "sustainable" local fleet when the issues lay elsewhere.
"Most of the mackerel is caught by large trawlers fishing off the north Scottish coast and further north," he added. "These vessels are capable of catching several hundred tonnes per night. In contrast, most of the mackerel caught in the South West is taken by small vessels fishing with handlines. This is a highly sustainable method of catching fish and causes absolutely no danger to the stocks."
Mr Muirhead highlighted that the local handline fleet had just 0.83% of the total UK quota for mackerel.
A MCS spokesman said: "Our advice clearly states that for people to ensure they eat mackerel as sustainably as possible, they source it from local fisheries using traditional methods such as handlining. This is the reverse of the effect we might have anticipated."