Cape Town - A long-awaited update into the investigation of the curious large-scale Cape fur Seal die-off has returned inconclusive results with no official cause determined behind the occurrence.
The probe followed the inexplicable deaths of seals along the South African and Namibian coasts which began in September 2020.
Sea Search environmental conservation organisation co-director and a lead researcher in the investigation, Tess Gridley, said the chronically sick animals remain unable to battle on and were still sadly suffering, however, the acute die-off stage had passed.
The Department Of Environment, Forestry and Fisheries (Deff), the Western Cape State Veterinary Services and the Cape Of Good Hope SPCA jointly released an update which showed that the deaths were resulting from a variety of factors, including malnutrition.
However, what was behind this particular malnutrition was what remained curious.
While the researchers said no definite causes had been determined yet, their strongest efforts continued in the ongoing investigation the Deff described as the first of its kind since a similar occurrence in 1994/95.
SPCA chief inspector Jaco Pieterse said dead and dying seals from the mortality event were still continuing to appear but the numbers in the Cape Town area reduced since the initial high mortality rate in September to December 2021.
“It is very frustrating that we do not have a definite answer of why the seals are dying. We continue to work closely with Deff and the state vet to find the cause of all the deaths. We are determined to find the reason,” Pieterse said.
The State Veterinary Laboratory conducted post-mortem examinations on seal pups and sub-adults following the die-off which found evidence of moderate to severe malnutrition.
“Clinical signs, including convulsions seen in the video footage received suggest possible biotoxin poisoning. As a result, extensive testing for significant parasites and viruses, including distemper, as well as bacterial infections were conducted on all carcasses,” said the department.
The department said because of the neurological signs witnessed, similar tests would be conducted on adult carcasses as part of a more thorough, well-rounded investigation by the State Vet.
When in September, droves of dead seal pups washed up at Lamberts Bay colony, Gridley said they took action and froze seven of the freshest seals (which died in less than 24 hours) to capture the environmental conditions they were exposed to before death.
Gridley said these frozen seals might help them understand the cause behind seal die-off in both South Africa and Namibia as previous research demonstrated that the naturally occurring, biotoxin domoic acid could lead to premature birthing (abortions) and death in seal pups.
“In total, 1 633 seals were buried or removed by municipalities between September and November 2021. Stakeholders, such as Sea Search Research and Conservation, assisted by launching a carcass reporting platform. Review of the data is still under-way,” said the department.
