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The study tested the effect of daily feed ration (DFR: 0.5%, 0.75%, 1.0%, 1.25%, and 1.5% of fish biomass) on juvenile pikeperch (Sander lucioperca) with an initial body weight of 21.5 ± 5.1 g and total length of 144.5 ± 8.5 mm. The pikeperch were fed floating feed at 8-hour intervals for a duration of 84 days. By the end of the experiment, the group fed DFR of 1.5% exhibited the highest body weight (51.5 ± 16.1 g) and total length (188.2 ± 17.8 mm). The weight heterogeneity, measured as the coefficient of variation (CV), ranged between 30.29 and 33.24%. The specific heterogeneity rate (SHR) ranged from 304.44 to 334.94‰/day. The group with DFR of 1.0% exhibited the highest degree of heterogeneity. Minor fin erosion was observed in the caudal fin by the end of the experiment. No significant differences were revealed in selected biochemical parameters indicating the liver, spleen, and intestinal function. All the fish tested were adequately fed, being provided sufficient nutrients for the proper growth of pikeperch. The DFR of 1.5% was evaluated as the most favourable. This amount of feed supported a higher number of values for Fulton's coefficient (FC), specific growth rate (SGR), thermal growth rate (TGR), fish weight heterogeneity, growth of total fish biomass (BG), and optimum level of biochemical parameters in blood plasma. [ABSTRACT FROM AUTHOR]

An active preference for higher temperatures within a physiological optimum is beneficial for animal movement. For example, ascending temperatures induce an increase in cyprinid fish metabolism and swimming ability. Spring upstream migrations driven by the search for resources may be related to these increases. Conversely, downstream migrations in autumn follow a decrease in temperature. When fish migrations are driven by a search for resources, for example, food availability and reproduction, or to avoid predators, then the temperature effect can be reduced to approximately the threshold temperatures that induce up‐ and/or downstream movement. To test this assumption, we tracked the seasonal migrations of the common bream Abramis brama between a reservoir and its tributary using radio tags with temperature sensors during a 5‐year period. Upstream migrations of the species into the tributary were not motivated by seeking temperatures different from those in the reservoir, that is, fish body temperatures in both environments were comparable across seasons. However, for long‐distance migrations, increasing temperature did support upstream migrations. Temperature did not determine the direction or intensity of short‐distance migration of the species between the reservoir and the tributary. No significant influence of temperature was recorded for the downstream migrations according to the results of the generalised additive mixed model (GAMM1), which related movement distance as the explanatory variable to the signed fish body temperature as the response. The second model (GAMM2) relating fish body temperature as the explanatory variable to the signed movement distance as the response obtained a threshold value of 19.1°C for the upstream migrations and 1.5°C for the downstream migrations of the common bream. [ABSTRACT FROM AUTHOR]