Search

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]

Background. An ongoing quest for alternative feed sources in global aquaculture includes insect breeding for feed and food production. The aim of this study was to evaluate the effect of partial to full replacement of commercial diets with live insects on growth and health parameters of rainbow trout, as well as on sensory and texture attributes and fatty acid composition of fish muscle. Material and methods. Five isocaloric diets containing commercial pellets and live insects were evaluated in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), in a 60-day feeding trial. Control Group (K) was fed commercial pellets only. In other groups, 25% gross energy of pellets was replaced by live adult house cricket, Acheta domestica (Group C), live superworm, Zophobas morio larvae (Group L), or a combination of 12.5% crude energy of each (group LC). The insect-only group (I) was fed live cricket and superworm only (50% by 50% crude energy). Results. No significant differences were found in growth, survival, feed conversion ratio (dry basis), or energy utilization between groups. The protein efficiency ratio was highest in Group K and decreased with increasing cricket proportion. Insect inclusion was associated with lower content of nutritionally valuable n-3 fatty acid in fish muscle. Subjective sensory evaluation of cooked fillets revealed significantly less acceptable taste, aroma, and aftertaste in Group I than for Groups K, L, and LC. Some differences were found in the whiteness and redness of fillets between groups. The control group had significantly lower hardness compared to those receiving insect diets. No gross morphological or histopathological anomalies of viscera in any group and no significant differences in 7-ethoxyresorufin-O-deethylase activity were observed. Conclusions. Live insects replaced the commercial diet of the equivalent caloric level without negative effects on the growth or health of rainbow trout. The lower content of n-3 fatty acids and differences in color and texture of fillets from fish fed insects may influence acceptability to consumers. The high cost of insects compared to commercial feed currently limits their widespread use in trout production. [ABSTRACT FROM AUTHOR]