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Shift in piscivory by salmonids following invasion of a minnow in an oligotrophic reservoir

March 16, 2024

Predation can play an important role in structuring ecological communities, and predator–prey dynamics can be altered following the introduction of new species. An unauthorized introduction of redside shiner (Richardsonius balteatus) into reservoirs in the Upper Skagit River, Washington, USA created concern that a consequent shift in predator–prey dynamics in the reservoirs could reduce recruitment and production of native salmonids in the basin. We estimated predation mortality in Ross Lake on nonnative redside shiner and juvenile native salmonids to evaluate the potential role of predation in regulating these populations and limiting survival of native species of concern. We used bioenergetics modelling and stable isotope analysis combined with directed field measurements of growth, seasonal diet and thermal experience of piscivorous salmonids to quantify their consumption demand on prey fishes to evaluate the relative magnitude of predation mortality on invasive redside shiners and native salmonids. While redside shiner are the dominant prey fish species in Ross Lake, the modest biomass of native salmonids consumed could translate into substantial mortality, the magnitude of which depended on the timing and size at which prey fishes were eaten. This information provides important context for how nonnative species may indirectly impact native species through shared predation (apparent competition) and can inform conservation decisions surrounding nonnative species control, sustainability of native salmonids and introductions of anadromous fishes.

Publication Year 2024
Title Shift in piscivory by salmonids following invasion of a minnow in an oligotrophic reservoir
DOI 10.1111/eff.12778
Authors Rachelle Carina Johnson, Marshal Hoy, Karl D. Stenberg, Jonathan H Mclean, Benjamin Lorenz Jensen, Tessa Julianne Code, Carl Ostberg, David Beauchamp
Publication Type Article
Publication Subtype Journal Article
Series Title Ecology of Freshwater Fish
Index ID 70252607
Record Source USGS Publications Warehouse
USGS Organization Western Fisheries Research Center