eesti teaduste
akadeemia kirjastus
Estonian Journal of Ecology
The impact of the White-tailed Eagle Haliaeetus albicilla and the Osprey Pandion haliaetus on Estonian Common Carp Cyprinus carpio production: How large is the economic loss?; 209–223

Joosep Tuvi, Ülo Väli

Protected bird species have been suspected to be a cause of a significant economic loss at Estonian fish farms, but its extent has remained unexplored. We counted the number of White-tailed Eagles and Ospreys, and the quantity of fish they take, and analysed the economic loss in five carp farms in 2001–2004. Each of Estonian four larger carp farms was used by a pair of breeding White-tailed Eagles, and by up to three immature birds, whereas Ospreys were recorded at all five studied farms. The average daily number of foraging White-tailed Eagles per farm was 1.3–3.3; the number of birds was constant during the breeding period but differed between years. The average number of Ospreys (0.5–2.8) fluctuated both within and between years. White-tailed Eagles foraged upon 300–1050 g third-year fish, and caught on average 0.4 fish per day per eagle. Ospreys took third-year fish at the beginning of the breeding season but second-year fish later; they always selected fish weighing 200–400 g, and caught 0.3–3.7 fish per day. The total amount of fish taken by the two species differed significantly between years and regions. The extent of loss caused to a fish farm depended on the methodology used for estimation. Calculations based on potential final weight of fish were on average 44% higher than those based on current weight, and constituted up to 4% of the total price of fish sold, and 2% of the total weight of fish reared by the company.


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