Experts have failed to find an explanation for the thousands of crab deaths along England’s shoreline over the last two years.
Mass poisoning linked to the area’s industrial past or an algal bloom were initially thought to have killed the crabs, but the crustacean mortality expert panel (CMEP) couldn’t find evidence for those claims.
The CMEP was responsible for providing an independent scientific assessment of all the possible causes of the mass crustacean mortality incident using all the relevant available data.
From October 2021, dead crabs began washing up in large numbers at beaches on the northeast coast of England. This unusual mortality continued through October and November 2021 and occasionally through 2022. The animals were found along at least 70 km of coastline.
According to the report, some crabs showed unusual twitching before they died, and other marine animals remained largely unaffected.
Fishing groups said decades-old toxic chemicals could have been released by drilling activity. The panel examined disease pathology, harmful algal bloom, chemical toxicity, and dredging as possible explanations for the deaths.
The report said that despite the lack of direct evidence of such a pathogen, a novel pathogen is considered the most likely cause of mortality because it would explain the critical observations like the twitching. But the report stressed that this novel pathogen explanation is “about as likely as not.”
The report added it was also possible that several of the factors considered could have operated together to lead to the crab deaths.
“For example, if there was a harmful algal bloom, that could have given greater stress to the environment generally, there could have been slightly lower oxygen as a result of that, and that could have triggered the mass mortality as they are less able to cope with viral load, for example, of this potential new pathogen,” Tammy Horton, a research scientist at the National Oceanography Centre and co-author of the study, told news media The Guardian.
On Friday, British Environment Minister Therese Coffey said she would consider if further analysis by government scientists might establish a definitive cause.