THE EFFECT OF LIGHT AND STOCKING DENSITY ON THE RESULTS OF REARING OF EUROPEAN CATFISH (SILURUS GLANIS L.) LARVAE
Jacek Kozłowski, Paweł Poczyczyński
Warmia and Masuria University in Olsztyn
ABSTRACT. Two experiments were carried out on European catfish larvae fed artificial feeds, in which the effects of light and stocking density on fish growth and survival were studied. In experiment 1 the fish were reared in illuminated (group A) or dark (group B) tanks, for 28 days, at 28oC, in water recirculation system. The final average fish body length was 61.1 mm (A) and 62.0 mm (B), and body weight: 2265.5, and 2192.0 mg respectively. No statistically significant differences were observed (Chi-square test, P<0.05). Total fish mortality reached 80.1% (A), and 69.3% (B), in which losses due to cannibalism represented 53.7% and 43.7% respectively. Fish survival was 19.9% in group A and 30.7% in group B. Statistically significant differences were observed between the groups. In experiment 2, European catfish larvae were reared in 3 groups of different stocking density: 15 ind. dm-3 (C), 25 ind. dm-3 (D), and 50 ind. dm-3 (E), for 21 days at 26oC, in water recirculation system. The final average fish body length reached 21.4, 20.5, and 21.6 mm in C, D, and E groups respectively, and did not significantly differ. Fish body weights were 88.3, 78.7 and 79.0 mg respectively, and the value for group C was significantly higher compared to D and E (Chi-square test, P<0.05). Fish mortality was 43.6%, 51.1% and 72.9% in C, D, and E respectively, of this cannibalism represented 20.3, 22.9 and 36.2%. Survival was higher at lower stocking densities, and equal to: 56.4% (C), 48.9% (D), and 27.1% (E). Mortality, survival and cannibalism were significantly lower in group E compared to C and D.
Key words: EUROPEAN CATFISH, REARING, LIGHT, STOCKING DENSITY