Scientists have found that plans to use a “fish disco” to deter migratory marine life from the nearby Hinkley Point C nuclear reactor could help save 90% of fish from the power plant’s water intake pipes – but the solution is set to cost its developer £700m.

EDF Energy, which is building the Hinkley Point C nuclear plant in Somerset, said research it commissioned from scientists at Swansea University had found that using an acoustic deterrent system helped to ward off the “vast majority” of fish it tagged for the experiment.

The costly system, informally referred to as a “fish disco”, is designed to use more than 300 underwater speakers to emit sound pulses to repel fish from the water intake pipes, which will suck in water from the River Severn to help cool Hinkley’s reactors.

EDF said it expected to spend about £700m on the solution, or 1.5% of the total cost of building the £46bn project, which would give Britain’s first new nuclear power plant in a generation “more fish protection than any other power station in the world”.

This should help to save about 44 tonnes of fish a year – equivalent to the annual catch of a small fishing vessel. The company declined to speculate on the total cost per fish saved over the 25-year life of the reactor’s subsidy contract.

EDF has argued against the requirement to fit an acoustic deterrent in the past, instead suggesting that it could construct salt marshes to help protect marine life.

Under EDF’s subsidy contract it will earn a set return for the electricity generated by Hinkley, meaning it will need to absorb the extra cost of the fish disco rather than add it on to household bills.

The system is expected to include special mouths fitted to the intake pipes to slow the water suction and allow fish to escape from as close as 2 metres away, and a fish recovery system which returns fish sucked into the pipes.

The scientists found that only one of its tagged twaite shad fish came within 30 metres of the test intake pipes when the speakers were turned on, compared with the 14 seen in the same area without the system turned on.

In good news for the salmon population, the research found that those migrating to the Atlantic generally use the main channel of the Severn, which is well away from Hinkley Point C’s water intake pipes. In two years, only two tagged salmon were detected within 1km of the intakes, the scientists said.

Dr David Clarke, a fisheries scientist and marine ecologist at Swansea University, said: “These early results are very encouraging with the system clearly working. Our results show that a large majority of the tagged shad avoid an area extending some 60 metres from the intake heads protected by the acoustic fish deterrent system.”

Chris Fayers, the head of environment at Hinkley Point C, said: “Because the system works even better than we had hoped, it means we can meet all of our planning obligations and should not need to create 900 acres of salt marsh as environmental compensation. And it’s good news for a power station that will generate the reliable, low carbon electricity that the country needs.”

The results of the research will be submitted for regulatory consideration and approval by the Marine Management Organisation later this year.