Growth response of pikeperch larvae in relation to body size and zooplankton abundance

The most critical period at onset of feeding in pikeperch Stizostedion lucioperca is short (<5 days at 20° C). The larvae are sensitive to prey density during the first week of exogenous feeding. First-feeding larvae of 6.5 mm total length ( L_T ) needed prey densities of >585 prey l^?1 to maintain mass (C_maint), whereas 5 days older larvae of 7 mm L _T C_maint= 55 prey l^?1 and for 11 mm L _T larvae C_maint<10 prey 1^?1. Changes in specific growth rates for larvae of 7 and 11 mm were similar to a type-II functional response curve reaching a specific growth rate of 26 and 30% day^?1, respectively, at 1000 prey l^?1, whereas the 6·5 mm larvae showed a linear growth response reaching a specific growth rate of only 9% day ^?1 at 1000 prey l^?1. The results suggest that prey density is a limiting factor, which might contribute to the high variation between year-class Strengths.