The great cormorant’s menu is full of fish
The tiny islet of Äijäkari to the north of Ruissalo serves as a nesting site for over 1,700 pairs of great cormorants. Great cormorants feed exclusively on fish, and the hunting birds can often be seen in Airisto, off the coast of Ruissalo. They catch fish by diving to depths of 10–20 metres. Adult great cormorants need approximately half a kilogram of fish per day, so an individual bird eats nearly 50 kg of fish in a single summer, whereas the entire colony consumes tens of thousands of kilograms of fish. Studies have shown that the great cormorant’s most common catches are roach, viviparous blenny and perch, which make up 90% of its diet. The proportions of the economically more valuable zander and Baltic herring are small (4% and 1%, respectively).