The humble fish finger, a staple of children's menus, is to get a makeover in response to declining fish stocks. Cod will be replaced in Birds Eye fish fingers by pollock after experts warned that cod stocks are perilously low.

Pollock, a white fish found in seas round north Alaska, has a similar texture to cod, but its stocks are far more plentiful.

Birds Eye, which produces 80 per cent of the UK's fish fingers, is switching part of its catch from cod to pollock fish fingers in September. The company, which was bought from Unilever by the private equity group, Permira, for £1 billion (€1.49 billion) last year, sold £80.5m worth of fish fingers in the UK in the year to July 14th.

Pollock is already used in the company's fish fingers sold in mainland Europe. The company will initially replace 4,000 tonnes of cod with pollock; 17,000 tonnes of cod are used in British fish fingers every year.

Martin Glenn, chief executive of Birds Eye Iglo, said the motivation behind the move was "enlightened self-interest".

Stocks of cod are under so much pressure that big food companies no longer take their catch from the North Sea but from the Baltic, according to Mr Glenn, but those fisheries are also under increasing strain.

Canadian stocks of cod off the Grand Banks of Newfoundland in the north Atlantic collapsed in the early 1990s when they were fished out to serve thecountry's massive fish processing industry. The stocks have never recovered. Experts fear a similar fate awaits cod in other parts of the Atlantic.

Mr Glenn said it made sense to diversify the source of fish fingers to a more sustainable fish. "We would be crazy not to try to do it. We think there will be a fish finger franchise for a long time to come." The company has found people willing to accept pollock in tasting tests and will spend £7m advertising the new pollock fish fingers to consumers.

Rupert Howes, chief executive of the Marine Stewardship Council, which certifies certain fish stocks as "sustainable" based on its research into which are still present in sufficient numbers, said Birds Eye's decision "demonstrates their continued commitment to responsible fishing".

Mr Glenn said the swap had been made possible by the company's new private equity owners. Although Unilever had a policy on using fish from sustainable sources, he said it was not effective enough.

By contrast, he said: "Private equity is supposed to be viciously short-term, but the paradox is that it has allowed us to be far more strategic than under Unilever."- ( Financial Times service)