Trophic interactions between yellow perch (Perca flavescens) and their benthic prey in a littoral zone community

Yellow perch (Perca flavescens) growth rates in northern Lake Champlain have declined in recent years while densities have increased, suggesting resource limitation. At high densities, predators have the potential to influence prey communities, but these effects can be highly complex. Using in situ mesh cages in an unmanipulated littoral zone setting, we examined the effects of two densities (0.5 and 1.5/m(2)) of yellow perch on (i) their growth and (ii) the abundance of major prey groups in the benthic community. Yellow perch growth rates were significantly lower in the high-density treatment than in the low-density treatment. Because site characteristics were not manipulated, measured covariates reflecting sediment and vegetation variation between cages were used to help clarify treatment effects on benthos. Fish predation on invertebrate prey was significant only in the high-density predator treatment for three of the six prey groups examined (predatory chironomids, prey chironomids, and isopods). For this littoral zone community, availability and abundance of benthic prey strongly influenced yellow perch growth rates; but the effect of yellow perch predation on benthic community structure was only moderate.