The effect of cover on food consumption and growth in two freshwater fish species used in experimental studies

To define suitable holding conditions for fish used in experimental studies on food consumption and growth, the effect of cover on growth at two ration levels was quantified for immature individuals of two common, freshwater species: the threespine stickleback (Gasterosteus aculeatus: Gasterosteidae) and the European minnow (Phoxinus phoxinus: Cyprinidae). In the European minnow, the presence of cover significantly increased growth rates and also the rate of food consumption at ad libitum rations; however, cover had no significant effect on the growth of the threespine stickleback. In both species, fish fed ad libitum rations had higher growth rates than fish fed 4% of body weight per day. This study illustrates the need for species specific holding conditions and illustrates an approach to welfare using measurements of traits closely related to fitness.