Effect of water hardness, temperature, and tank wall color, on the effectiveness of swim bladder inflation and survival of Eurasian perch (Perca fluviatilis, L.) larvae reared under controlled conditions

Abstract

The study shows how water temperature, water hardness, and color of tank affect the swim bladder inflation effectiveness (SBIE) and survival in Eurasian perch larvae in controlled conditions. Three separate experimental rearings (in 50-L tanks) were conducted, where (1) water temperature (12 days, 3000 ind./tank; 15, 20, and 25 °C), (2) water hardness (12 days, 4600 ind./tank; 15 °C; and 5, 10, and 15°n), and (3) tank wall color (20 days, 25,000 ind./tank; tanks with black and white walls; 15 °C) constituted tested variables. During all of the experiments, the photoperiod was 24 h (24L:0D), and the intensity of light was 1500 lx at the water surface. In experiments 1 and 2, perch larvae were not fed and in experiment 3, from 5-day post-hatch (DPH), they were fed ad libitum with Artemia sp. nauplii. In experiment 1, the highest SBIE was observed for larvae reared at 15 °C (20.6 ± 1.1%) for 20 °C and 25 °C; the maximum SBIE was significantly lower (8.4 ± 2.9% and 13.0 ± 5.8%, respectively; p < 0.05). The mortality trend was similar for all of the tested temperatures, although at higher temperatures, the larvae were seen to die sooner. In experiment 2, there were no statistical differences (p > 0.05) in mortality of larvae and in final SBIE. The results of experiment 3 clearly suggests that the white tanks caused a significant (p < 0.05) reduction in survival rate (4.9 ± 3.2% and 24.6 ± 6.4%, for white and black tanks, respectively) as well as SBIE (7.7 ± 2.7% and 32.9 ± 3.6%, for white and black tanks, respectively; p < 0.05). The outcomes indicate that Eurasian perch larval rearing at 15 °C in black tanks is preferred.