Risk of Predation to Stream invertebrates by Fish Across a Gradient of Habitat Complexity
We examined the role of habitat complexity and prey density on fish predation of stream invertebrates. We hypothesized that: 1) risk of predation to invertebrates would decrease as habitat complexity increased, and 2) predation effects would be proportional to prey density. In a field experiment, the number of amphipods (Gammarus pseudolimnaeus) consumed by mottled sculpins (Cottus bairdii) was compared between cages differing in densities of invertebrates (10 or 30 individuals/cage) and sizes of leaf packs (0, 1, 5, and 10 g). Sculpin cages were stocked with one mottled sculpin, and control cages were not stocked with a sculpin. The experiment had a full-factorial design. We found that the proportion of prey remaining in a cage increased with leaf pack size. In the absence of sculpins, the proportion of prey remaining did not change. The proportion of prey remaining was not influenced by the prey stocking density, suggesting the predation was proportional to prey density. Our results suggest that leaf packs provide refuge habitats from predation for stream invertebrates and that larger leaf packs are better refuge habitats than smaller leaf packs.
Faculty Mentor: Carl Ruetz
Page last modified July 14, 2009