Critical swimming speed in intensively cultured European perch (\kur{Perca fluviatilis} L.): Influence of fish size, production system and repeated testing

Critical swimming speed and swimming performance in relation with different factors were tested this thesis in groups of European perch (Perca fluviatilis) with focus to utilize these results in intensive aquaculture. Thesis is consisted of four different experiments performed in swimming tunnel. In the first experiment were tested, if there are any differences in day distances of measuring between three groups of fish. Each group were measured three times. First group was measured in time (t) 0, 24 and 48 h, second group was measured in time (t) 0, 48 and 96 h. Finally, third group was measured in time (t) 0, 96 and 192 h. Second experiment was set to compare critical swimming speed in three weight categories of a fish. Weight categories of 100g, 200g and 250g were tested. In the third experiment were tested pond reared fish and aquaculture (RAS) reared fish. Results were compared together, if there are any differences. Last experiment was set to find out if there is any relationship between level of critical swimming speed and somatic indexes or fillet and caraccas yield. No one of experiments performed confirm expectations of results. In the first experiment was found that there no effect of repeated swimming tests on critical swimming speed as well as no effect of different recovery period (from previous test). In comparison of different weight categories were measured highest levels of critical swimming speed in 100g group without decreasing trend in for bigger size categories (200 and 250 g). Pond and intensively reared fish had same level in critical swimming speed. Moreover, fourth experiment did not confirm influence level of critical swimming speed to somatic indexes or fillet yield. Results of presented thesis can contribute on better technical design of rearing units for this gastronomically and economically interesting species in intensive aquaculture, mainly in RAS systems