Effects of repeated disturbances on feed intake, growth rates and energy expenditures of juvenile perch, Perca fluviatilis

As aquaculture of Eurasian perch (P. fluviatilis) develops, optimizing growth becomes increasingly important. Fish may be stressed by ordinary farming procedures such as handling and cleaning of tanks. This may induce behavioural changes, reduce feed intake, increase energy expenditures and thus reduce growth rates. In order to quantitatively evaluate the effect of disturbance on feed intake, growth rate and energy expenditures of perch, groups of fish were exposed to one of three treatments including control (no disturbance), moderate disturbance (shadows from movements above the tanks) and severe disturbance (shadows from movements above the tanks + simulating cleaning of tanks). Twelve groups were used for each treatment category. Average weight (and SD) of the fish was 39.6 g +/- 14.7. Feed intake and growth rates were registered at two different temperatures (16.6 +/- 0.7 degrees C and 22.7 +/- 1.1 degrees C) and energetic growth efficiency was calculated. Feed intake, growth rates and growth efficiency were significantly reduced by disturbance treatment (P <= 0.001). At both temperatures, disturbed groups of fish had lower feed intake and growth rates than undisturbed groups of fish, but the effect on growth efficiency was significant only at 17 degrees C (P<0.05). It is concluded that the observed reductions in growth rates are caused by increased energy expenditures for disturbed fish, and that more effort should be put into reducing disturbance of fish in both experimental and farming situations. (c) 2007 Elsevier B.V. All rights reserved.