Bogdan Wziątek, Andrzej Martyniak, Katarzyna Stańczak, Piotr Hliwa
ABSTRACT. The aim of the study was to determine the food preferences of the black cormorant and to assess fisheries losses in Włocławski Reservoir. Twenty fish species were identified in the cormorant diet. The dominant species were ruff and perch (29.4% and 24.4 % of the weight share, respectively). Roach (11.9%) and Prussian carp (10.9%) were also important components of the cormorant diet. The share of invasive species from Gobiidae family was negligible (0.2%). Among the fish species important to commercial and recreational fisheries management, the most numerous in the cormorant diet were: ide (10 t; 2.7% of the weight share), pikeperch (8.6 t; 2.3%), asp (6.3 t; 1.79%), and pike (4.9 t; 1.3%). The fish biomass consumed by cormorants was a mean of 372.8 t annually, which is 46.6 kg per ha (range of 44.6 to 49.6 kg per ha). The analysis of fisheries losses in 2009 was estimated at 980,000 PLN.
Keywords: rainbow trout, yersinosis, vaccination, immersion
Przyjęto po recenzji 1.10.2010 r.