Growth of larval and juvenile perch: the importance of diet and fish density

In August, growth rate of young-of-the-year (YOY) perch in lake enclosures could be explained by both YOY density and mean cladoceran biomass, suggest ing that in a lake where YOY perch are dominant, growth may be density depe ndent in late summer and mediated through top-down control on daphnid bioma ss. In June, growth rate of YOY perch could not be fully explained by YOY d ensity or by mean cladoceran biomass, suggesting that growth and survival d uring the first part of the summer is negatively affected by a diet of Bosm ina and cyclopoid copepods only. The experiments also suggest why YOY perch have a slow growth and a low abundance in eutrophic lakes where small zoop lankton dominate. The June experiment also indicated that growth of late la rval or early juvenile perch improved when a larger cladoceran became avail able and was included in the diet. (C) 2000 The Fisheries Society of the Br itish Isles.