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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Life Histories
INTERACTIONS OF AN ENDEMIC SNAIL AND MOLLUSCIVORE FISH: NEGATIVE EFFECTS ON SNAIL DENSITIES.
H.M. Kloeppel1, J.C. Marks1, and D.A. Hendrickson2. 1Departments of Biology, Northern Arizona University, Flagstaff, 2Department of Intigrated Biology, University of Texas, Austin
Cuatro Ciénegas, a protected area in Northern Mexico, is an ecologically unique and important environment that provides habitat for an abundance of endemic aquatic species. The distribution and behavior of the endemic Hydrobiid snail Mexipyrgus carranzae and its interactions with its polymorphic fish predator Herichthys minckleyi are not well understood. The objective of this study was to understand the vertical spatial distribution of M. carranzae and evaluate the effect of molluscivore fish densities, water chemistry, and temperature on snail densities in 13 pools throughout the Cuatro Ciénegas basin. M. carranzae vertically stratifies within the soft, flocculent sediments of the pools down to a depth of 10-20 cm to possibly avoid fish predation. A fish-exclosure experiment demonstrated that snail densities increased two-fold in the absence of fish. Finally, snail densities increased from day to night in the top 5 cm of the sediments, suggesting snail vertical migration through the sediments at night. These results suggest that molluscivore fish negatively affect snail densities and that snails vertically stratify in the sediments during the day and migrate to the surface to feed at night, escaping fish predation.
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