Growth, cannibalism, and survival relations in larvae of European catfish, Silurus glanis (Actinopterygii: Siluriformes: Siluridae)—attempts to mitigate sibling cannibalism

Background. Under culture conditions, intra-cohort cannibalism is one of the main factors that affects the growth and survival of fishes, especially during the early life stages of carnivorous species. Cannibalism is chiefly influenced by environmental factors, but parental effects cannot be excluded. The complete elimination of cannibalism in the larviculture of carnivorous fish species is virtually impossible, but it may be possible to mitigate its impact through a better understanding of the extrinsic and intrinsic factors that affect the intensity of cannibalism. The presently reported study had two complementary objectives: a) it examined how the growth–cannibalism–survival dynamics in cultured larvae of European catfish, Silurus glanis Linnaeus, 1758, is affected by maternal influence, and b) it evaluated the possibility of reducing cannibalism while supplementing food with tryptophan (TRP), which is a precursor of serotonin that has a becalming effect on fish. Materials and methods. Two 30-day experiments were conducted (0L : 24D, 26.5–27.0°C). In the first experiment, 3–day old larvae of European catfish originating from four female parents (f1, f2, f3, and f4) were cultured in full siblings groups. In the second experiment, larvae from all four progenies were reared together and fed commercial diets supplemented with different doses of tryptophan (T0, T1, T2). Fish mortality including cannibalism, growth, and biomass were estimated every 10 days during both experiments. Results. In both experiments, cannibalism was the main cause of mortality and losses to type II (complete) cannibalism were higher than those caused by type I (incomplete) cannibalism. No maternal influence on cannibalistic behaviour was found. Tryptophan supplementation had no significant effect on fish growth or survival. Conclusion. The results of presently reported studies confirmed that cannibalism is an important factor affecting survival in larviculture of European catfish. Controlled conditions used in initial rearing of European catfish larvae, significantly enhanced the survival of juvenile catfish in comparison to traditional pond culture.