Seals and porpoises being killed in increasing numbers by ducted propellers

Seal populations sliced up by ship propellers may face extinction warns conservation group
October 2013. WDC, Whale and Dolphin Conservation has called on the government to take immediate action after the release of more evidence linking the deaths of large numbers of healthy seals and harbour porpoises to injuries consistent with impact by ducted propellers used by a range of shipping vessels.

106 harbour seals & numerous porpoises
Between June 2008 and July 2012, 106 dead harbour seals and grey seals were found around the coast of the UK with a single continuous circular skin laceration spiralling down the body and numerous harbour porpoise strandings have also been found with the same ‘corkscrew' cuts to the skin similar to the seal cases.

Ducted propellers
These injuries have been linked to the ducted propellers used by vessels such as tugs, self-propelled barges and rigs, various types of offshore support vessels and research boats. Studies reveal that in some cases, there was an apparent correlation between the appearance of carcasses on shore and the presence of work boats operating in the vicinity.

Incidents like this in the UK were originally reported from 2008, but examination of historic data shows that injuries may have been occurring long before then and, in certain cases, appear also to coincide with the recent expansion of the offshore renewable energy industry and the associated increase in work boat activity.

Tip of the iceberg
Worryingly, it seems most likely that these cases are the tip of the iceberg. Only seals or porpoises that die in coastal waters are washed ashore and not all of these will be found, reported, then diagnosed. Therefore, assuming many carcasses do not make it ashore, the potential impact could be much greater and, in the case of declining harbour seals, could even be having negative effects on population levels.

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