No abstract

The reaction of common carp (Cyprinus carpio L.) in an ice‐ and snow‐covered pond to depletion of dissolved oxygen (DO) in winter was recorded using radio telemetry. The carp moved from the deeper parts of the pond to the shallow areas near the tributary in search of better oxygenated water. Evidence was found that feeding occurred until December but ceased with the oxygen crisis. After the carp farmer started aeration to improve the oxygen supply, carp returned towards the deeper parts of the pond. The gross activity was significantly correlated with DO (P<0.001) and was not influenced by water temperature (P>0.05). The clear documentation of the carp's reaction to oxygen depletion suggests, that radio telemetry may be useful for investigating the effects of various stress factors on fish in pond aquaculture.

Summary The fat content and fillet yield of common carp (Cyprinus carpio) from three carp farms were investigated with respect to pond management and overall climatic conditions. The mean fat content of the trimmed fillet varied from 2.7 to 6.9% and differed significantly among the three facilities (P < 0.001). It is suggested that differences in the fillet fat content may be based on the climatic conditions as well as the different management strategies (feeding, stocking biomass). The mean fillet yield was calculated as 34.0–39.0%. No significant correlation between fish weight and fillet yield (ρ = −0.16) was found. Results suggest that producing smaller fish for fillets of serving size may lead to a higher production and conclude with lower production risks and costs.