Harbour porpoises are one of the most commonly sighted marine mammals around the UK; unfortunately it is also one of the most commonly stranded as well. A figure which has been steadily rising over the last few decades to the point where even the EU Commission has stepped in to demand the UK does more to protect their porpoise populations. Now new data released by the UK Cetacean Strandings Investigation Programme has shown that over the last 25 years the number of porpoises that have starved to death has increased.
As a cause of death, starvation was relatively unheard of amongst harbour porpoises before the new millennium. But with the onset of the noughties the observed starvation rate massively increased. Between 2003 and 2014, 16% of UK strandings were found to have starved. This may not seem like a huge percentage however in the 12 years previous to that it was only 4%!
This leap in numbers has got scientists scratching their heads. No other marine mammal appears to be suffering the same fate, with their starvation rates still remaining relatively low since the 1990’s. Thus whatever is causing this, is only impacting the harbour porpoises and has only been impacting them for the last decade or two.
There are two main theories currently; either the porpoise population has gotten to big to support itself or there is a lack of small fish which is their main prey.
Harbour porpoise populations are not well established in the UK so we are currently unable to tell if overpopulation is responsible. Similar to a lack of prey though this would potentially cause starvation as there would be increased competition for food.
Perhaps more interestingly is the role humans may inadvertently be playing here. Both harbour porpoises and larger fish mainly predate on the smaller fish species. As we have begun to practice more sustainable fishing techniques in our waters, the number of larger fish has risen and so to has competition for food. Have we created the increased starvation amongst harbour porpoises by being more environmentally friendly?
Featured Image of Harbour Porpoises by Nicola Hodgins
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