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.
Avault, J. W. 1996. Fundamentals of Aquaculture. AVA Publishing Company, Baton Rouge.
Bechard, M. & Márquez, C. 2001. Mortality of wintering Ospreys at aquaculture facilities in Colombia. In Abstracts of the 4th Eurasian Congress on Raptors, p. 18. Estación Biológica Doñana & Raptors Research Foundation, Seville.
Cramp, S. & Simmons, K. E. L. (eds) 1980. The Birds of the Western Palearctic. Vol. 2. Oxford University Press, Oxford.
Dunstan, T. C. 1974. Feeding activities of Ospreys in Minnesota. Wilson Bull., 86, 74–76.
Edwards, T. 1998. Temporal and social aspects of the foraging ecology of a piscivore, the Osprey (Pandion haliaetus). PhD thesis, University of Florida.
Egna, H. S. & Boyd, C. E. 1997. Dynamics of Pond Aquaculture. CRC Press, Boca Raton, New York.
Elts, J., Kuresoo, A., Leibak, E., Leito, A., Lilleleht, V., Luigujõe, L., Lõhmus, A., Mägi, E. & Ots, M. 2003. Eesti lindude staatus, pesitsusaegne ja talvine arvukus 1998.–2002. a. Hirundo, 16, 58–83.
Enneveer, N. 1985. Kalakasvatus. Valgus, Tallinn.
Feare, C. J. 1991. Control of bird pest populations. In Bird Population Studies (Perrins, C. M., Lebreton, J. D. & Hirons, G. J. M., eds), pp. 463–478. Oxford University Press, Oxford.
Häkkinen, I. 1978. Diet of the Osprey Pandion haliaetus in Finland. Ornis Scand., 9, 111–116.
Hallikainen, M. 2001. Luonnonsuojelulailla rauhoitettujen lintujen aiheuttamien vahinkojen torjuminen. Menetelmät ja niiden soveltuvuus Suomen olosuhteisiin. Ymperistöministeriö, Helsinki.
Helander, B. 1983. Reproduction of the White-tailed Sea Eagle Haliaeetus albicilla (L.) in Sweden, in relation to food and residue levels of organochlorine and mercury compounds in the eggs. PhD Dissertation. Stockholm University, Sweden.
Helander, B. & Stjernberg, T. 2002. Action Plan for the Conservation of White-tailed Sea Eagle (Haliaeetus albicilla). Birdlife International, Strasbourg.
Jetmar, F. 2000. Occurrence and changes in numbers of birds on the Opatov fishpond system. Sylvia, 36, 127–153.
Lõhmus, A. 2001. Habitat selection in a recovering Osprey Pandion haliaetus population. Ibis, 143, 651–657.
McLarney, W. 1984. The Freshwater Aquaculture Book. Hartley & Marks, Washington.
Mečionis, R. & Jusys, V. 1994. The White-tailed Eagle (Haliaeetus albicilla) at Kuršių lagoon. Acta Ornithol. Lit., 9–10, 138–142.
Meske, C. 1985. Fish Aquculture. Technology and Experiments. Pergamon, Oxford.
Mizera, T. 1995. Why is the Osprey Pandion haliaetus a rare breeding species in Poland? Vogelwelt, 116, 197–198.
Moll, K. H. 1962. Der Fischadler Pandion haliaetus. Neue Brehm-Bücherei, Wittenberg Lutherstadt.
Naylor, R. L., Goldburg, R. J., Primavera, J. H., Kautsky, N., Beveridge, M. C. M., Clay, J., Folke, C., Lubchenco, J., Mooney, H. & Troell, M. 2000. Effect of aquaculture on world fish supplies. Nature, 405, 1017–1024.
Nilsson, S. G. & Nilsson, I. N. 1976. Numbers, food consumption, and fish predation by birds in Lake Möckeln, southern Sweden. Ornis Scand., 7, 61–70.
Paaver, T. 2000. Eesti kalakasvatuse uued arengujooned – väikekalakasvatuse osa kasv. Eesti Kalakasvataja, 3.
Pettay, T., Cairenius, S. & Ellermaa, M. 2004. Linnut Virossa – suomalaisten havainnot 1990–2002. Viron Lintuseura, Kotka.
Puhk, M. & Tohvert, T. 1978. Karpkalakasvatuse normatiive. Sotsialistlik Põllumajandus, 13, 618–620.
Randla, T. & Tammur, E. 1996. The White-tailed Sea Eagle Haliaeetus albicilla population and breeding productivity in Estonia and some regions of NW Europe. In Eagle Studies (Meyburg, B.-U. & Chancellor, R. D., eds), pp. 51–56. WWGBP, Berlin, London & Paris.
Saurola, P. & Koivu, J. 1987. Sääksi. Kanta-Hämeen Lintumiehet ry, Forssa.
Statistical Office of Estonia 2005. Commercial catch and realisation in fish farms by species. In Statistical Database. http://www.stat.ee
Sulkava, S., Tornberg, R. & Koivusaari, J. 1997. Diet of the White-tailed Eagle Haliaeetus albicilla in Finland. Ornis Fenn., 74, 65–78.
Tohvert, T & Paaver, T. 1999. Kalakasvatus Eestis. Tõravere trükikoda, Tartu.
Yodzis, P. 2001. Must top predators be culled for the sake of fisheries? Trends Ecol. Evol., 16, 78–84.
