Crab deaths on UK coast may be caused by unknown disease, finds report

A scientific committee has ruled out chemical poisons and algae as causes of crustacean mortality in north-east England, saying new diseases are the most likely cause.

To Jason Arunn Murugesu

Crab deaths seen in northeast England in 2021 and 2022 may have been caused by a previously unseen disease, according to the UK’s Department for Environment, Food and Rural Affairs (Defra). The convened scientific committee concluded that algae and chemical poisoning were unlikely causes of death, as previous studies had suggested.

In October 2021, tens of thousands of dead crabs and lobsters washed up in the Tees estuary on the North Yorkshire coast and further south in the fishing village of Whitby. In May 2022, his Defra study of deaths pointed to the rapid natural growth of algae in the ocean, also known as algal bloom, as a possible cause of death. However, the study also acknowledged that no single causative factor was found behind the deaths.

In October, a group of researchers commissioned by the fishing industry published an original study of the mass mortality. The team argued that algal bloom was unlikely to be the culprit, and instead was likely the release of pyridine in the sediment dredged to make way for a new freeport on the River Tees. suggested.

Britain’s Environment Secretary Therese Coffey has ordered Defra to set up an independent scientific commission to investigate the matter further. The Commission now reports that no single factor can be blamed for the mass mortality of crustaceans. Instead, they estimate a 33-66% chance that the mass mortality was caused by a new disease affecting only crabs and lobsters.

At a press conference, Tammy Horton of the UK’s National Oceanographic Center, who was part of the committee that wrote the report, said the new disease could explain why the crabs exhibited jerky behavior when they died.

Houghton said it could also explain why the mass deaths persisted for so long, and the fact that other marine life seemed unaffected. No evidence has been found, she added.

The report downplayed Defra’s initial suggestion that algal blooms were the cause of the deaths, and this failed to explain the spasms seen in the crabs. “I don’t think there’s anything wrong with previous reports,” he said. “As is often the case in science, our knowledge has deepened over time.”

The committee also said there was no possibility of pyridine poisoning due to the length of time the mass deaths occurred. “You need a large, continuous source of pyridine to trigger it.” [crab deaths] Obviously not. “

The Tees were last dredged before the mass die-off in December 2020, and no further dredging took place in the area until September 2022, the report said.

Henderson said if disease is the main cause of these crab deaths, it’s hard to know if it’s causing more deaths in the area. reporting [crab deaths] more often,” he said. “It’s hard to tell if something is anomalous until you’ve collated all the data.”

Horton said the disease appears to affect only crabs, so it’s unlikely to be dangerous to humans.

Rodney Forster of the University of Hull, UK, who took part in the second report of crab deaths that were ultimately blamed on dredging, said the new report was at best complete and strongly agrees with its findings. He says the debacle over the issue highlights the failure of Britain’s water monitoring system. “Our system is reactive, not proactive,” he says.

Due to budget cuts to government agencies, Forster said water quality in the UK is only measured at the surface and not at the crab-inhabited bottom. Toxic algae levels are also not monitored in areas of the UK not used for oyster and mussel farming, he says. That’s a big reason, he says.

“I think we underestimate the value of having a healthy and safe river,” says Forster. “To understand that, we need to measure certain parts of the ocean system. We need to be prepared for a changing climate.”