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 Champlai n have declined in recent years while densities have increased, sugges ting resource limitation. At high densities, predators have the potent ial to influence prey communities, but these effects can be highly com plex. Using in situ mesh cages in an unmanipulated littoral zone setti ng, we examined the effects of two densities (0.5 and 1.5/m(2)) of yel low perch on (i) their growth and (ii) the abundance of major prey gro ups in the benthic community. Yellow perch growth rates were significa ntly lower in the high-density treatment than in the low-density treat ment. Because site characteristics were not manipulated, measured cova riates 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 tr eatment for three of the six prey groups examined (predatory chironomi ds, 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 benthi c community structure was only moderate.