Evaluating The Impact Of The Invasive Bullfrog (Lithobates catesbeianus) In The Aquatic Fauna’s Trophic Cascade At The New Mexico Río Mora National Wildlife Refuge

Presentation: Invasive species are known to cause devastating effects in introduced habitats. Invasive species can be introduced on purpose or by accident, most commonly by human activity. They are known to increase competition for habitat and food resources with native species. Invasive bullfrogs (Lithobates catesbeianus) were introduced along the Mora River at the Rio Mora National Wildlife Refuge. We have eradicated the bullfrogs in a section of the river to study their impact on the aquatic fauna. We found that the invasive northern crayfish (Orconectes virilis) is an important component of the diet of bullfrogs. In this study we hypothesized that the removal of bullfrogs in the Mora River will release the crayfish population from predation, which may lead to a mesopredator release. We used systematic sampling to determine the relative abundance and overall size of crayfish in both sites using baited minnow traps. There is a highly significant difference in mass between control (21.63 g) and experimental sites (18.58 g; p-value< 0.0001). However we did not find a significant difference in abundance between both sites. We hypothesize that the size difference between both sites is the results of increase recruitment and survival of young individuals that now suffer less predation, dragging the average down. Cursory evaluation of data on fish density shows a similar pattern where fish. Further examination of the data will provide us insight to the trophic interactions amongst bullfrogs, crayfish and fishes in the Mora River at the Rio Mora National Wildlife Refuge.