Document: CYN-3-51-25

A pond experiment investigating the effects of small-bodied fishes on growth and survivorship of wood frog larvae.

PASZKOWSKI, C.*, B.EATON, T.GARTNER and B.GINGRAS

University of Alberta, Edmonton AB T6G 2E9, Canada ¹

Abstract:
The stocking of large, piscivorous fish species has been implicated as one factor contributing to the widespread decline of amphibian populations, but the effects of smaller fish species is less clear. We examined experimentally survivorship to metamorphosis of wood frog (Rana sylvatica) larvae in the presence of fathead minnow (Pimephales promelas) and brook stickleback (Culaea inconstans), two fishes that commonly occur in small shallow lakes in northern Alberta. Over 12,000 newly hatched wood frog larvae were introduced into each of three 360 m² ponds that had been divided in half to create two replicates of three treatments: Fishless, adult minnows present, or adult sticklebacks present. Trapping and visual surveys indicated that tadpoles disappeared rapidly from ponds with fish. We monitored metamorphs through pitfall-trapping and systematic searches. Six hundred and ten froglets were collected from the fishless pond, whereas only nine and 28 froglets emerged from the ponds with minnows and sticklebacks, respectively. The few metamorphs from ponds with fish emerged later and were larger. Our results demonstrate that even small-bodied fishes negatively affect wood frog larvae through predation or competition. Dramatic inter-annual variation in the densities of these fish populations, caused by winterkill, creates dynamic and unpredictable conditions for wood frog reproduction in small boreal lakes.

Keywords: Amphibians, Fishes, Interspecific interactions, Recruitment

This abstract is being presented at: 10:30 AM in session:
Poster Session #9: Fish, Lakes, Streams and Wetlands.