"The decline is terminal, unless we introduce much more effective management immediately," said the study by the university's International Network on Water, Environment and Health (INWEH).

"This is one more voice added to the chorus about how bad the situation for the world's coasts is," Peter Sale, INWEH assistant director, told Reuters. Fixing the problems "do not mean spending more money but spending it more wisely".

High prices for foods such as wheat and rice may mean people press for more fishing, he said. A conclusion in the report said "management of fisheries is failing".

"Even in a developing country that critically needs more food it is better to have a management system in place that means they have some fish rather than none at all," he said.

The study said world fish catches peaked in the late 1980s with larger species, such as tuna and swordfish, being progressively fished out.

A UN summit in Rome from June 3-5 is considering ways to defuse a world food crisis which threatens up to 1 billion people with hunger, caused by factors including rising populations, high oil prices and a shift to biofuels.

"Coastal marine systems have declined progressively in recent decades due to the growth of human populations and their demands on the marine environment and resources," the report said. "Bays and estuaries, sea grasses, and mangroves and wetlands have suffered dramatically in the past 50 years."

Run-off from fertilisers were adding to "dead zones" along the coasts and corals could be under threat from warmer oceans.

The UN climate panel projected last year that world sea levels will rise by between 18 and 59 cm (7-23 inches) this century due to heat-trapping emissions of greenhouse gases, mainly from burning fossil fuels that are melting ice sheets.