Non-native species found in the Pacific Northwest.

Project Title

Non-indigenous Species Impacts on Listed Salmonids

Description

Project 1: Non-indigenous species are recognized as one of the top environmental threats to global diversity and have been cited as a cause of decline in 42% of species listed under the U.S. Endangered Species Act. During their life cycle, salmonids traverse large geographic areas spanning freshwater, estuary and ocean habitats where they encounter numerous non-native species. To date, the cumulative impact of non-indigenous species on salmonids has not been described or quantified. In this paper, we examine the extent to which introduced species are a potentially important risk to threatened and endangered salmon, ultimately by contributing to higher levels of life-cycle mortality. We identify and categorize all documented introduced species in the Pacific Northwest, including fish, invertebrates, birds, plants, amphibians and others. Where data exist, we quantify the impact of non-indigenous species on populations of threatened and endangered salmonids. For example, birds and fish predators are reported to consume 0-40% of juvenile salmon in some habitats. These data indicate that the impact of non-indigenous species on salmon is equal to or greater than commonly addressed impacts (habitat, harvest, hatcheries and hydro-system) and suggest that managing non-indigenous species impacts may be imperative for the recovery of these fish.

Project 2: In streams throughout the Salmon River basin in Idaho, the presence of non-native brook trout is correlated with reduced survival of juvenile Chinook salmon. To identify potential mechanisms, we made in-stream observations of individual Chinook and brook trout, quantifying their distribution, habitat use and overlap, and interactions with neighboring fish. In Summit Creek, where native trout are rare and the abundances of brook trout and Chinook are similar by the end of the summer, we completed 278, 5-minute observations while snorkeling and used multiple regression analyses to identify variables explaining encounter rates, outcomes of encounters, and feeding rates. Encounters among fish were frequent, with Chinook displaced most often by larger brook trout. The size of neighboring fish was significant along with other environmental variables in explaining the rate and outcome of encounters. Brook trout were on average 1.5x larger than Chinook in late summer, indicting their potential impact on Chinook feeding behavior is large. Fish stomach contents were also examined to identify diet overlap and direct predation of brook trout on Chinook. Efforts to recover threatened Chinook will likely be most effective when impacts of non-native species are understood and considered.

Project 3: Where are predation impacts of smallmouth bass the greatest throughout the Columbia River Basin? Smallmouth bass are one of the most voracious non-native predators on juvenile salmonids. Recently published work in the Yakima demonstrated that smaller individuals have the greatest predation impacts. In collaboration with state and regional biologists, we will examine where impacts of bass are the largest and identify whether there are management actions that can be taken to reduce those impacts (i.e., bounty, manage size distribution).

Investigators

Beth Sanderson, Kate Macneale and Katie Barnas

Collaborators

Michelle Rub and Pip Corbois (Conservation Biology Division), Peter Kiffney

Support

NOAA Fisheries

Project Status

2 manuscripts submitted, data collection and further analysis in progress

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