Aquatic community responses to stream restoration: effects of wood and salmon analog additions

Abstract

Many aquatic ecosystems in the Pacific Northwest have been impacted by land use activities. Often these impacts have resulted in deleterious effects that directly or indirectly limited the capacity of habitat to produce fish. Habitat restoration potentially increases the quantity and quality of resources available to the aquatic communities within these impaired systems, thus increasing biotic integrity and fish production. In this study, responses of aquatic communities exposed to woody debris bundle and salmon analog additions were measured in the year following creation of off-channel, fish habitat in southcentral Alaska. Biofilm, invertebrates and juvenile coho salmon, Oncorhynchus kisutch, were sampled in four treatment types (control, wood, analog, and analog+wood). Biofilm significantly increased in analog enriched treatments. No treatment effects were detected in benthic invertebrate responses, however, treatment differences were detected in coho diets. Coho density and standing stock were significantly higher in the wood treatment, and coho in the control treatment showed signs of density-dependent limitations. Condition for fish was highest in the analog enriched treatments after treatment additions. These results suggest salmon analog and woody debris bundle additions may be viable short-term restoration tools, providing a boost in food and shelter for aquatic communities in habitats undergoing restoration.