Individual variation and feeding interactions between and within two freshwater fish species pumpkinseed (Lepomis gibbosus) and yellow perch (Perca flavescens).

摘要

Variation in feeding behaviour was studied among young individuals of pumpkinseed (Lepomis gibbosus) and yellow perch (Perca flavescens). Three types of food, Drosophila, Daphnia and Artemia were used for the experiments. Eight individuals of pumpkinseed differed significantly in their number of feeding attempts, in time interval between feeding attempts (in the beginning, middle and towards the end of the experiment), feeding angle, number of unsuccessful attempts and regurgitations. Most of the differences in the time interval between feeding attempts were observed in the middle and towards the end of the experiment. When the experimental diet was composed of three types of foods (Drosophila, Daphnia and Artemia) in a mixture, the total number of feeding attempts in the experiment decreased. Mixing the food types also reduced the feeding efficiency of individuals which was evidenced by the increased time interval between the feeding attempts and the increased unsuccessful attempts and regurgitations. Individuals of pumpkinseed showed the highest preference for Daphnia. On the basis of the above feeding variables, groups of individuals of differing feeding patterns were identified.; Similar patterns were observed for the eight individuals of yellow perch. Perch fed more efficiently on Artemia, however, two individuals of perch were more efficient on feeding on Daphnia.; Effects of the presence of conspecifics and increasing population density were examined on the variation among individuals of the pumpkinseed and yellow perch, for two types of food, (Daphnia and Artemia), separately and in a mixture. The effects of conspecifics were not equal on each individual of pumpkinseed and yellow perch. Only the weaker individuals were affected more by the presence of other conspecifics than the stronger ones. The increasing population density of conspecifics increased the variation among the individuals of both species.; The effect of the presence of heterospecifics (yellow perch) were also examined on individuals of pumpkinseed for similar food types and feeding variables. At low experimental densities the effects of the heterospecifics were not significant. However, at high densities yellow perch affected the feeding behaviour of pumpkinseed individuals significantly. The effects of conspecifics on pumpkinseed were always greater than heterospecifics. Yellow perch did not affect the feeding behaviour of all the individuals of pumpkinseed equally.