Project title: Seasonal movements and habitat use of rainbow trout (Oncorhynchus mykiss) in the Susitna River basin, south-central Alaska.
Personnel Kevin Fraley (MS 2015) Funding source(s): Alaska Department of Fish and Game; Matanuska-Susitna Salmon Habitat Partnership Project description: Potamodromous Rainbow Trout are an important ecological and recreational resource in freshwater systems of Alaska, and increased human development, hydroelectric projects, declining Pacific salmon stocks, and climate change may threaten their populations. We used aerial and on-the-ground telemetry tracking, field-measured and remotely-sensed aquatic habitat characteristics, snorkel surveys, and resource selection and occupancy models to characterize seasonal movements and habitat use of adult Rainbow Trout (>400 mm FL) at multiple spatial and temporal scales across a large (31,221 km2) and complex Susitna River basin of southcentral Alaska during 2003-2004 (N = 148) and 2013-2014 (N = 84). We found that trout overwintered in mainstem habitats near tributary mouths from November-April. After ice-out in May, trout ascended tributaries up to 51 km to spawn, and afterward moved downstream to lower tributary reaches to intercept egg and flesh subsidies provided by spawning salmon in July and August. Trout transitioned back to mainstem overwintering habitats at the onset of autumn when salmon spawning activity waned. Fidelity to tributary of capture varied across seasons, but was high in three out of four drainages. Different habitat characteristics influenced Rainbow Trout habitat use during each season, including stream gradient and sinuosity in the winter, substrate suitability and sinuosity during spawning, mean annual flow during the pre- salmon feeding season, and Chinook salmon spawning potential after the arrival of adult salmon in freshwater. We found that during the ice-free feeding season trout responded to fine- scale (channel unit) characteristics rather than more coarse-scale (stream reach) variables. Weekly movements were significantly longer when spawning salmon were present compared to pre-arrival. We found no difference in movements and habitat use for a subset of fish for which sex was identified using genetic analysis. However, the observed sex ratio was heavily female- biased, which contrasts with what has been observed in other non-anadromous salmonid populations. As most trout undertake extensive movements within and among tributaries and make use of a variety of seasonal habitats to compete their life histories, it will be critical to take a broad and multi-scale approach to their management in light of anticipated future land use and climate change. Co-Investigators: Megan McPhee (UAF) Anupma Prakash (UAF) Rich Yanusz (ADFG) Sam Ivey (ADFG) |
Outreach:
Products: Peer-reviewed publications: Fraley, K.M., Falke, J.A., McPhee, M.V., and A. Prakash. 2018. Rainbow trout movement behavior and habitat occupancy are influenced by sex and Pacific salmon presence in an Alaska river system. Canadian Journal of Fisheries and Aquatic Sciences 75:525-537. Fraley, K. M., Falke, J. A., Yanusz, R., and S. Ivey. 2016. Seasonal movements and habitat use of potamodromous Rainbow Trout across a complex Alaska riverscape. Transactions of the American Fisheries Society 145:1077-1092. Thesis: Fraley, K. M. 2015. Seasonal movements and habitat use of rainbow trout in the Susitna River basin, southcentral Alaska. Unpublished Master's thesis. School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, Alaska. 105 pp. Oral and poster presentations: Fraley, K.M., Falke, J.A., Yanusz, R., and S. Ivey. 2015. Seasonal movements and habitat use of rainbow trout (Oncorhynchus mykiss) in the Susitna River basin, Southcentral Alaska. 2016 Matanuska-Susitna Salmon Habitat Partnership Salmon Symposium. November 19, 2015. Palmer, AK. Fraley, K.M., Falke, J.A., Yanusz, R., and S. Ivey. 2015. Seasonal movements and habitat use of rainbow trout (Oncorhynchus mykiss) in the Susitna River basin, Southcentral Alaska. American Fisheries Society Annual Meeting. August 17, 2015. Portland, OR. Fraley, K.M., Falke, J.A., Yanusz, R., and S. Ivey. 2015. Seasonal movements of Rainbow Trout (Oncorhynchus mykiss) in the Susitna River Basin, Southcentral Alaska. Alaska Cooperative Fish and Wildlife Research Unit Annual Research Review. March 25, 2015. Fairbanks, Alaska. Fraley, K.M., and J.A. Falke. 2014. Seasonal movements of Rainbow Trout (Oncorhynchus mykiss) in the Susitna River Basin, Southcentral Alaska. Alaska Chapter American Fisheries Society Meeting. October 23, 2014. Juneau, Alaska. |