2007 Volume 71 Issue 4 Pages 255-262
We assessed how litter piles (i.e., terrestrial leaves and twigs) in the river mouth act as a refuge for the marine amphipod (Anisogammarus pugettensis) from predation. We compared the survival rates of A. pugettensis under predation pressure from flounder (Pleuronectes schrenki) using different organic debris particle size classes and different amounts of debris (batch sizes). Particle size classes were <10, 10-50, and 50<mm, which were supplied in 0-, 5-, or 50-g batches. After 24 h, A. pugettensis survival was higher in larger batches of debris regardless of particle size. In addition, we conducted feeding experiments using kelp and terrestrial leaves as food resources for A. pugettensis in June and October 2005 to estimate the usage of these food resources. Although A. pugettensis that were fed only terrestrial leaves exhibited negative growth rates, carbon stable isotope analysis in both experimental seasons indicated that terrestrial leaves were part of the A. pugettensis diet. From these experiments, we concluded that terrestrial leaves are occasionally used as a food resource by A. pugettensis, although their principal role is as a refuge.
