Cooperative Fish and Wildlife Research Units Program: Maine
Education, Research and Technical Assistance for Managing Our Natural Resources

Lakes in Maine with natural and stocked fish populations support invertebrate communities that differ from those naturally without fish. The introduction of fish to historically fishless lakes also may affect the amphibian species that reside, breed, or feed in these water bodies. Introduced fish may affect amphibian species abundance and composition by changing food resources, eating the amphibians, eating aquatic insects that prey on amphibians, and by altering amphibian breeding and refuge sites. Amphibian species that are palatable to fish, for example, may be consumed by fish or may avoid fish by altering their movements in the landscape to locate alternative fishless sites. Lakes stocked with fish may become biological sinks for amphibian populations that continue to use the water bodies for egg-laying in spite of the presence of fish, resulting in their offspring, or the adults themselves, being consumed by fish. It is not clear whether there are mechanisms in naturally fishless lakes stocked with fish that allow amphibians to persist in these modified environments. Habitat characteristics such as structural complexity and egg laying sites as well as characteristics of eggs masses may affect breeding success in these permanent water bodies. Through this study, we hope to identify characteristics of Ambystoma maculatum (spotted salamander) egg masses occurring in fishless and fish-containing lakes and adjacent vernal pools and features of these habitats that make them suitable or unsuitable habitat for this species. Furthermore, we will determine if amphibian community composition differs among fishless and fish-containing lakes. Project objectives are: 1) Characterize amphibian communities of fishless and fish-containing lakes in Maine. 2) Determine if egg mass morphology and oviposition affect Ambystoma maculatum resistance to predation. 3) Determine effects of fishless lake, fish-containing lake, and vernal pool predators on survival of Ambystoma maculatum eggs and larvae. 4) Determine fitness of adult Ambystoma maculatum adults breeding in vernal pools, fishless lakes, and fish-containing lakes.