A disease or parasite new to UK waters may have caused the deaths of thousands of shellfish along the North East and North Yorkshire coast, a report said.
The government previously blamed “harmful algae”, while fishers commissioned a report which suggested it was due to the chemical pyridine.
The new report by 12 experts found it was “about as likely as not” a pathogen new to UK waters caused the die-off.
They said it was “very unlikely” dredging carried out nearby caused it.
They also ruled out toxic pollutants and harmful algal bloom.
However, current data, they said, “cannot be definitive”.
Although there was no direct evidence of a disease or parasite, the report added that theory would explain the twitching seen in dying crabs.
But it said it was possible a combination of factors – rather than one considered by the panel – could have led to the “unusual” deaths.
The report said pathogens known to cause similar symptoms had caused crustaceans to die around the world.
It said no significant pathogens were identified in the North East case but “full molecular screening was not conducted at the time of the initial investigation”.
Simon Clarke, Middlesbrough South and East Cleveland’s Conservative MP, said it was now “definitively clear” the deaths were not caused by “either capital or maintenance dredging of the Tees or anything else associated with the Teesworks site”.
He said it was a “concern” investigators had identified an unknown pathogen, adding: “There is now more to be done to investigate this and also to look at the support that we can offer our local fishermen to recover.”
Fishermen, including Adrian Noble in Whitby, had described the situation with the die-offs as “horrendous”
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