Question to the Department for Environment, Food and Rural Affairs:

To ask His Majesty's Government what evidence they have to suggest that the cause of mass marine deaths between the River Tees and the River Esk was the result of a new pathogen, given the presence of high levels of pyridine in dead crustaceans.

The Crustacean Mortality Expert Panel were unable to identify a clear and convincing single cause for the unusual crustacean mortality but considered a novel pathogen or disease to be, as likely as not (33 to 66% probability), the cause of the mass mortalities reported in the north-east of England in autumn 2021. This likelihood is based on key observations including mortality over a sustained period and along 70 km of coastline, the unusual twitching of dying crabs and the deaths being predominantly crabs rather than other species.

The panel concluded it was very unlikely that pyridine or another toxic pollutant caused the crab deaths, given there could not be sources of any significant volume of pyridine during the period of the crab deaths. Seawater measurements (by the Environment Agency and by York University) could not detect levels of pyridine sufficient to cause mortality during this period. Environment Agency tests for pyridine in crab tissue in the affected north-east coastal region as well from Penzance, Cornwall, and the Norfolk Wash indicated that pyridine can be found in crab tissue in most samples regardless of location. Sediment levels of pyridine from dredged material and other toxic chemicals found in sediments were significantly lower than the levels which would cause crab mortality.