fisherman
Well-known member
ermmmm......have we met?
Thousands of crabs and lobsters washed up on Yorkshire beaches,
- Thread starter Concerto
- Start date
Greg2
Well-known member
Paralytic Shellfish Toxins were the cause of deaths in dogs having consumed dead sea creatures on beaches in Norfolk and Suffolk
https://www.eastern-ifca.gov.uk/wp-content/uploads/2019/05/2019_05_16_EMFF_Press_release.pdf
Hydrozoan
Well-known member
Interesting, thanks; that project was triggered by incidents in early 2018, and I see that it ran until August 2021 so I guess it will probably not have considered the incident in the OP.
Greg2
Well-known member
Thats right, it hasn’t directly although Cefas have been involved in both. Interestingly PST’s are caused by algeal blooms and the mystery with the dog deaths scenario was that such blooms don’t occur during the winter months so identifying the source was a key objective.
Hydrozoan
Well-known member
Although blooms are for obvious reasons most prevalent and intense in the period from spring to late summer, I see there is some evidence that 'churning' by storms may produce blooms in winter - including this for the North Sea:
'Some researchers have found that numbers of plankton can actually begin to increase in the middle of winter, when growth conditions would seem to be at their worst. Studies suggest that winter storms churn the ocean and cause deep water mixing. This water mixing allows for phytoplankton to grow and live at depth without being spotted by their predators.'
Satellite captures giant algal bloom in North Sea
Greg2
Well-known member
Yes, that was a consideration in the work that Eastern IFCA and Cefas did. An interesting dimension was the furthest distance between incidents of dogs becoming unwell - north Essex and north Norfolk.
Hydrozoan
Well-known member
The recently published (17 January 2023) report of the panel of independent experts convened by Defra's Chief Scientific Advisor makes interesting reading: Independent Expert Assessment of unusual crustacean mortality in the north-east of England in 2021 and 2022 (publishing.service.gov.uk). The report categorises possible causes as follows:
Pathogen new to UK waters - As likely as not (33-66% probability)
Harmful algal bloom - Unlikely (<33% probability)
Chemical toxicity (including pyridine) from shore-based sources and sediment - Very unlikely (<10% probability)
Capital dredging on the Tees - Exceptionally unlikely (<1% probability)
Maintenance dredging - Very unlikely (<10% probability)
Chemical toxicity from point source(s) or dredging was considered Very unlikely or Exceptionally unlikely because '... no source of sufficient amount of any toxic material could be identified, despite a range of relevant sediment and water measurements, and based on expert assessment of this and literature evidence'.
A direct toxic effect of a harmful algal bloom was considered Unlikely because (i) although a bloom was considered likely to have occurred in the area in September 2021, it was considered unlikely to have persisted after a storm in early October and (ii) a toxic bloom would be expected to affect other organisms. Anoxia, as an indirect effect of a bloom, was also considered Unlikely because (i) it would not explain the 'twitching' behaviour seen in some crabs, (ii) it would likely affect other organisms, and (iii) crab deaths continued for some time after the bloom was likely to be present.
A pathogen new to UK waters was considered the most likely cause (As likely as not), because pathogens are known to cause similar symptoms, including the twitching, and because an '... amoebic crustacean disease, belonging to a similar group of parasites causing mortalities in the USA, has recently been found for the first time in UK waters in crabs on the south coast'.
Whilst a combination of causes cannot be ruled out, no particularly likely combination was identified.
Pathogen new to UK waters - As likely as not (33-66% probability)
Harmful algal bloom - Unlikely (<33% probability)
Chemical toxicity (including pyridine) from shore-based sources and sediment - Very unlikely (<10% probability)
Capital dredging on the Tees - Exceptionally unlikely (<1% probability)
Maintenance dredging - Very unlikely (<10% probability)
Chemical toxicity from point source(s) or dredging was considered Very unlikely or Exceptionally unlikely because '... no source of sufficient amount of any toxic material could be identified, despite a range of relevant sediment and water measurements, and based on expert assessment of this and literature evidence'.
A direct toxic effect of a harmful algal bloom was considered Unlikely because (i) although a bloom was considered likely to have occurred in the area in September 2021, it was considered unlikely to have persisted after a storm in early October and (ii) a toxic bloom would be expected to affect other organisms. Anoxia, as an indirect effect of a bloom, was also considered Unlikely because (i) it would not explain the 'twitching' behaviour seen in some crabs, (ii) it would likely affect other organisms, and (iii) crab deaths continued for some time after the bloom was likely to be present.
A pathogen new to UK waters was considered the most likely cause (As likely as not), because pathogens are known to cause similar symptoms, including the twitching, and because an '... amoebic crustacean disease, belonging to a similar group of parasites causing mortalities in the USA, has recently been found for the first time in UK waters in crabs on the south coast'.
Whilst a combination of causes cannot be ruled out, no particularly likely combination was identified.
penfold
Well-known member
While I can believe that the reporting also highlighted that the sampling carried out to monitor the capital dredging process was comically rubbish, even if they were unearthing deadly toxins it would be feasible to not detect them. A cynical man might think that was deliberate.
Spirit (of Glenans)
Well-known member
Crabs released from a damaged storage cage would just swim away, rather than washing up on shore, dead.