The effect of vertebrate predation on lotic macroinvertebrate communities in Québec, Canada

To test the role of vertebrate predation on benthic community structure, experiments were performed in two third-order streams in northern Quebec, Canada. Predators were either enclosed in or excluded from replicate benthic cages (20 × 30 × 10 cm). Ruisseau du Cran Carre (RCC) has a normal complement of fish, while Low Hope Creek (LHC) is fishless. In June 1983, two species of fish were manipulated (one fish per cage, five replicate cages per treatment) in RCC, while the salamander Eurycea bislineata was manipulated in LHC. In August 1983, brook trout fry were manipulated in both streams. It was anticipated that the fauna in LHC, having had no previous contact with fish, would be more susceptible to fish predation than the fauna of RCC. Gut analysis revealed that fish did feed in the cages. However, neither fish predation nor salamander predation had significant effects on prey communities in either stream in June. Community parameters (species richness and diversity, and total numbers of individuals) wer...