A ban on fishing sandeels in the North Sea is welcome but comes too late for this year's seabirds, says the Royal Society for the Protection of Birds.
Seabirds such as puffins feed on sandeels (Image: George McCarthy/rspb-images.com)
Brussels is expected to close the sandeel fishery this month to allow stocks of the small fish to recover.
Many seabirds feed on the sandeel and its decline was blamed for the worst breeding season on record in 2004.
But the RSPB says seabirds are breeding late again this year, and some are not even bothering to nest at all.
"Seabirds have delayed their breeding this year, so what sandeel peak there is this summer will have passed when many seabirds and their chicks most need the food," said Dr Euan Dunn, head of marine policy at the RSPB.
"Climate change and the rise in North Sea temperatures may well be the major cause of the sandeel decline and, if so, will take years to reverse.
"Because of that we need to make sure that other human action, notably fishing, doesn't make things worse for sandeels and seabirds in the short term."
Industrial fishing catches millions of tonnes of small fish - species like sandeels, sprats and anchovies - to turn into meal and oil, much of it to feed farmed fish.
This reduces the catch for seabirds such as kittiwakes, arctic terns, guillemots, and puffins, which rely on the fish during the breeding season as a source of nutrition and to feed their young.
If they cannot find enough to eat, the birds either stop breeding that year or nest too late.
Surveys in April and early May revealed that sandeel numbers in the North Sea were just half of the 300,000 million fish required to permit fishing to continue.
Scientists have advised that the fishery be closed and the European Commission is to accept the recommendation this month.
But the RSPB says kittiwakes on Orkney and Shetland are building nests exceptionally late and few breeding Arctic terns or Arctic skuas have been found.
"The indications are at the moment that late breeding birds will be in real breeding trouble," Dr Dunn told the BBC News website. "And those that breed early will still be struggling to find sandeel food."