Boris Johnson believes a campaign to encourage people to eat British-caught fish could help the industry combat post-Brexit disruption.
The prime minister backed calls for a campaign in a video conference with Conservative MPs from coastal areas.
He also promised to do more to address concerns about quotas and the ban on shellfish exports to the EU.
Labour said it also wanted people to eat more British fish - but that in itself would not save the industry.
Mr Johnson's official spokeswoman, Allegra Stratton, said the prime minister's favourite fish was Scottish salmon.
Fishing industry leaders have accused the PM of being "in denial" about the scale of the problems facing it.
Buying British fish
Barrie Deas, chief executive of the National Federation of Fishermen's Organisations, said fishing communities were "very disappointed" with the post-Brexit trade deal signed by Mr Johnson.
This gave "free access" to EU fleets to fish in UK waters, he added, but without "securing revised quota shares that would reflect the UK's new status as an independent coastal state".
He did, however, welcome the idea of a buy British campaign.
His organisation was getting a lot of emails from members of the public asking where they could buy British fish, he told BBC News.
The problem, he added, was that the UK has a taste for foreign species, and tended to export most fish caught in its own waters.
The UK is a net importer of cod and tuna, for example, while hake, which is plentiful in UK waters, is exported to countries like Spain.
The UK fleet catches more mackerel than any other species, although 60% of that is landed abroad, according to official figures.
There was "enormous scope" for a campaign to change the public's addiction to "bland" white fish from abroad, said Mr Deas, perhaps "getting celebrity chefs involved in advocating British fish".
Sheryll Murray, Conservative MP for South-East Cornwall, who organised the call with coastal MPs, said Boris Johnson himself could front a campaign to promote previously obscure British-caught fish.
"I think he comes into his own, the prime minister, with his PR, and if anybody can sell to the British public 'buy red mullet, buy John Dory, buy grey mullet', then I think he will have a darn good go," she told BBC South West political editor Martyn Oates.
In his call to MPs, Mr Johnson promised an "action plan" to deal with export problems.
Great Grimsby MP Lia Nici told BBC political reporter Sarah Sanderson: "We discussed short-term measures how to make sure that businesses can stay viable with the problems they're having - but also longer term legislation and what the UK can do in order to grow the industry in the future."
The PM is also understood to have urged coastal communities to invest in infrastructure to prepare for larger catches, as boats are allowed to land more from UK waters over the next five years.
But Barrie Deas said the expanded quotas would "not provide the level of additional fishing opportunities necessary to underpin the regeneration of our coastal communities".
"In addition, EU fleets can continue to fish within our 6-12 mile limits," he added.
And Labour's shadow environment secretary Luke Pollard said "no amount of top spin from the prime minister" would make the structural problems facing the industry go away.
He wanted people to eat more British fish, he added, but "this in itself will not save the fishing industry from going under because of the poor deal that's been achieved over our exit from the European Union".