A mix of causes that include fisheries and cannibalism have been suggested in the deaths of almost 300 seals whose carcasses washed ashore in the past four years.
The survey by the Irish Seal Sanctuary began in 2012 and relies largely on the support of the public to record the location of dead seals and to take photographs of the scene.
While the nature of the survey is non-scientific, some post-mortem studies at University College Dublin have identified injuries believed to be consistent with older bull seals attacking young members of the grey seal population.
The phenomenon may be responsible for injuries previously thought to have been caused by propellers, but further scientific research is necessary to confirm this.
In its second dead seal database report, covering the two years to May 2016, the Irish Seal Sanctuary says that 104 carcasses were washed ashore in 77 cases reported to it by the public.
The project discounts possible duplicate reports and cases of misidentified species, based on photographic evidence.
The numbers are down slightly from 171 dead seals recorded in 140 reports in the previous two years.
However, the latest report includes cases notified to the seal sanctuary from 13 counties, two more than in the previous two-year period, with the biggest number of carcasses found in counties Dublin (26), Cork (19), Wexford (12), and Waterford (11).
While numbers showing evidence of being tangled in fishery nets were small, the report said a separate study of mammals caught in tangle nets off Co Mayo showed much higher seal numbers than those reported to its survey. This indicates only a portion of seals caught in nets end up washing ashore. it said. Some people had reported freeing seals found in nets onshore, while many carcasses were entangled in plastic litter.
However, it was not possible to tell if the litter entanglements happened before or after the seals died.
The database of dead seals showed the highest numbers in Waterford and Wexford were found in December and January which may or may not be coincidental to inshore herring and sprat fishery happening at the same time, the seal sanctuary said.
The two main seal species in Ireland, the common and grey seal, are protec- ted under the country’s wildlife laws.
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