The influence of invasive species can be widespread with direct impacts to competitors and prey species, and indirect impacts that can extend through the food web. In the western US, the invasion of brook trout into streams historically dominated by other salmonid species has become an issue of particular concern. Most of the work on brook trout invasion has focused on their impact to native salmonids, particularly those that are threatened or endangered. Surprisingly few studies have evaluated the broader impacts of brook trout on streams food webs as a whole. In this research, we use a mass balance ecosystem/foodweb model (Ecopath with Ecosim - EwE) to evaluate potential impacts of brook trout invasion not only on native salmonids, but on the broader biotic community in two Chinook salmon rearing streams in the Snake River basin of Idaho. Parameter estimates for each of the 17 groups in the EwE models were derived from direct field data collected in mid-summer or literature values for comparable species and environments. The food web model was then balanced by solving for ecotrophic efficiency (EE), the proportion of a taxa groups’ production that is utilized within the system. Once balanced, we manipulated brook trout abundance within the framework limitations of the model and evaluated the response of estimated biomass accumulation of other taxa groups. Long-term, multiple time-step analyses (Ecosim) could not be conducted due to the migratory life-history of salmon in this system.
Results/Conclusions
