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Communication for the NABS Annual meeting, Duluth, 1999
EFFECTS OF MOSQUITOFISH (GAMBUSIA AFFINIS) ON TWO VERNAL POOL ORGANISMS, AMBYSTOMA CALIFORNIENSE LARVAE AND LINDERIELLA OCCIDENTALIS
K.E. Leyse1, S.P. Lawler1, and T. Strange2. 1Department of Entomology, University of California Davis, 1 Shields Ave, Davis, CA 95616, 2San Joaquin County Mosquito and Vector Control District, 7759 Airport Way, Stockton, CA 95206
California tiger salamanders, Ambystoma californiense, and California fairy shrimp, Linderiella occidentalis, two California endemics that occur in vernal pools, are threatened by loss of suitable habitat. Such loss of habitat is known to occur due to land type conversion, but may also occur when exotic species, such as mosquitofish (Gambusia affinis), are introduced to a body of water. In two separate experiments, we tested the effects of G. affinis on A. californiense larvae and on L. occidentalis to determine the extent to which fish affected abundance of these species. We used 6 3.05m x 6.1m x .6m ponds for each experiment. Six ponds were each stocked with 600 L. occidentalis and six ponds were each stocked with 42 A. californiense larvae. Twelve adult mosquitofish (approximate mosquito control stocking rates) were added to each of three ponds in each experiment. Lab experiments tested potential mechanisms underlying changes in population numbers. Mosquitofish significantly reduced fairy shrimp numbers. In contrast, we did not detect an effect of mosquitofish on growth or number of salamander larvae reaching metamorphosis. Results suggest that stocking mosquitofish at standard rates in vernal pools during early spring can affect fairy shrimp, but may not impact A. californiense
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