At least 20 eagle rays and two rig sharks have been found dead at Porirua Harbour.
Volunteers from the Wellington Coast Clean-Up Crew discovered the dead marine life during a clean-up on Sunday afternoon.
Lorraine Shaab, from the clean-up crew, said the group started about 2.30pm at low tide so volunteers could cross the inlet to reach an area where rubbish collects.
“Unfortunately, that’s how we saw all the rays,” she said.
“It was just heartbreaking.”
Shaab said some of the dead rays were found in the mudflats and others were in the water.
Biosecurity New Zealand’s Aquatic Health team manager Mike Taylor said recent stormy weather or possible predatory action from orca could be behind the deaths.
He said exotic disease had not been ruled out.
Specialist staff visited the site on Monday to collect samples for testing at an animal health laboratory.
The Department of Conservation confirmed it had been alerted, but said it would not be involved because the affected animals were not protected species.
