Compensatory growth in gibel carp (<i>carassius auratus gibelio</i>) after the stress of stocking density

Abstract

The research was performed to investigate the compensatory growth in gibel carp (Carassius auratus gibelio) after the stress of stocking density; the 8-week growth trial was performed in a proper system of 12 fibreglass tanks. Four different density groups were marked as C (control group), D1/2, D1/4 and D1/8, and the biomasses were converted into 1.98 kg/m3, 3.96 kg/m3, 7.91 kg/m3 and 15.82 kg/m3 respectively. Under density stress, the final weight, protein retention efficiency (PRE), feed conversion efficiency (FCE) and specific growth rate (SGR) of groups D1/2, D1/4 and D1/8 were significantly lower than group C (p < 0.05) and reduced with the increase in density. In the period of the recovery of activity space (5–8 weeks), groups D1/2, D1/4 and D1/8 have significantly higher feeding rate (FR), FCE and SGR than group C. There was no significant difference in body weight between group D1/2 and group C, while the body weight of group D1/4 and group D1/8 was still significantly lower than group C. The hepatosomatic index (HSI) of the D1/8 group was extremely low before and after the restoration of activity space (p < 0.05). Under stress, the lipid contents of group D1/4 and group D1/8 were significantly lower than group C. Subsequently, the recovery of activity space, the lipid content of group D1/8, was still significantly lower than group C. The results obtained indicated that the D1/2 group (3.96 kg/m3) successfully lead to wholly compensatory growth, while the D1/4 (7.91 kg/m3) and D1/8 (15.82 kg/m3) group partially lead to compensatory growth. So, higher density leads to poor compensation effect.