Scores of dead fish have appeared along the entire shoreline of Shelly Bay Beach in an occurrence suspected to be linked to an abundance of seaweed lowering oxygen levels in the water.

The Department of Environment and Natural Resources said it is investigating the situation but has not yet reached a conclusion on the cause of the deaths — predominantly of the redear herring, known locally as pilchards.

However, a spokeswoman said there had been a large amount of seaweed in the water and on the beach, washed in by the wind and currents. She said there were an unusual number of dead fish at the beach and that testing was required to determine whether the ocean in that area was still safe to swim in.

A walker contacted The Royal Gazette this week with photographs and video of the scene.

The department spokeswoman said: “The seaweed has turned the water green-brown as it breaks down. This process can lower oxygen levels in the water. Fish need oxygen to live, so low levels can harm them.

“Warm weather can make this worse. Shelly Bay is shallow so it can heat up quickly. The dead fish do not have sores or marks, so disease is not suspected.

“Similar low-oxygen events can happen when large amounts of plant material break down or when water is warm.

“A similar die-off of pilchards at Shelly Bay was last seen in 2015.”

The spokeswoman said there is a resident school of pilchards in the bay which puts them more at risk when conditions change. However, environment officers did also see one dead chub and two dead bream during a site visit on Monday.

She added: “The number of dead fish is unusual and shows that recent conditions in the bay were not normal.”

On the safety of the water, the spokeswoman added: “DENR has been speaking with the Department of Health, including the Environmental Health team, about water quality.

“The most recent test [on Monday] showed that the water met safety standards for swimming and more tests have been requested.

“Environmental Health continues to monitor conditions through its weekly seawater sampling programme, testing for enterococci and E. coli.

“DENR will continue to monitor the situation.

“While events like this are not common, they have happened before.

“DENR is working with other government departments to ensure the area is cleaned safely and as soon as possible. Results are published on the government portal at www.gov.bm.”

The spokeswoman reminded the public that there are no-netting rules in this area as a means of helping to protect fish stocks . However, she added that there is no sign this event is linked to illegal fishing.

Gary Weller, a retiree who was walking at the Hamilton Parish beauty spot on Monday morning, said he was shocked to see the dead fish in such numbers along the beach.

He said he had been told that more fish had been sighted on the sea floor about 50 feet from the shore.

Speaking to the Gazette from the beach, Mr Weller said: “There are hundreds of fish on the shore and in the water. There are too many to count.

“I am on the [pedestrian] bridge and there are tonnes of fry in the water, some of them are on their side.

“Right now, the wind is out of the southwest and there is a green haze in the water.”

• To see water quality results, visitwww.gov.bm/seawater-monitoring-programme-bathing-beaches