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

• The most critical period at onset of feeding in pikeperch Stizostedion luc\ioperca is short (<5 days at 20degreesC). 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 l(-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.

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