Stormy weather could be behind mass death of eagle rays at Porirua beach

Beach clean-up volunteers were shocked to find at least 20 dead eagle rays and two Rig Sharks at Porirua Harbour.

Lorraine Shaab from the Wellington Coast Clean-Up Crew said she and other volunteers made the discovery during a clean-up on Sunday afternoon.

"We started at 2.30pm at low tide because that's the only time you can cross the inlet to where the rubbish accumulates, and unfortunately, that's how we saw all the rays.

"It was just heartbreaking."

She said they found some of the rays in mudflats and some in the water.

Biosecurity New Zealand's Aquatic Health team manager, Mike Taylor, said they suspected recent stormy weather or potential predatory action from orcas could be to blame, but they had not ruled out exotic disease as a cause.

Specialist staff visited the site on Monday to collect samples and have them tested in an animal health laboratory.

The Department of Conservation confirmed they had been alerted to the mass death, but as the affected animals were not protected species, they would not be involved.