Friday, 13 February 2015

Cormorant Decline

European Shag
There are over forty species of cormorant worldwide, of which Scotland has two, the European Shag and rarer Great Cormorant. In some places, such as the US, the numbers in some cormorant species are huge, to the extent that, under pressure from fishing interests, large culls have taken place. For example, some 500,000 double-crested cormorants have been legally destroyed since 1998, yet an annual cull of 50,000 of this species represents less than 5% of its population.

Do we need to worry, then, that our local populations of cormorants and shags seem to have crashed? There are still a few around, but in nothing like the numbers of past years. If this area were rich in fish, one would expect us to be having an American problem: we don't.  Is, then, the loss of our cormorants a clear warning about fish stocks which we are ignoring?

Great Cormorant

There is some evidence that there is a problem with the shag population in this SNH paper (.pdf file here), which carries survey data to 2011.  Canna used to be particularly important as a breeding place for shags but huge damage was done to there by rats.  We have never seen a rat on West Ardnamurchan, so our loss is caused by something else.

The Scottish Government has just completed a consultation exercise on thirty proposed Marine Protection Areas, one of which, 'Loch Sunart to the Sound of Jura', includes a huge area running down the Sound of Mull to the south of us, while a second, 'Small Isles', covers some of the area to the north.  There's more about them on the Scottish Government website here.

US statistics from New Scientist 6th February 2015.

1 comment:

  1. Because Shags are deep diving it is thought that their sub sea pursuit of fish has lead to adaptations which reduce buoyancy; low body fat reserves and wettable feathers. Habitually they roost on rocks to dry out after foraging. This makes them vulnerable to winter gales when plumage remains wet for long periods. this could lead to higher mortality after prolonged periods of bad weather.