The primary objectives of this study in 1979 was to determine the seasonal distribution and relative abundance of selected fish species, with rainbow trout being the primary selected species, and to characterize the seasonal habitat requirements of these species. In 1983 these objectives were expanded to include also quantifying the important habitat parameters associated with spawning and rearing of these species and measuring fish density in spawning and rearing habitats to provide an estimate of habitat quality.
Rainbow trout (Oncorhynchus mykiss) were captured in the Iliamna drainage from 1986 to 1991. Abundance estimates of spawning trout found in the Kvichak River (at outlet of Lake Iliamna near village of Igiugig, southwestern Alaska) were derived using the Jolly-Seber estimator. Estimates of survival and age were also determined.
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 the large (31,221 km2) and complex Susitna River basin of southcentral Alaska during 2003-2004 and 2013-2014. We found that trout overwintered in mainstem habitats near tributary mouths from November to 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 complete their life histories, it will be critical to take a broad and multiscale approach to their management in light of anticipated future land use and climate change.
Results of the 1991 studies of upper Cook Inlet (southern Alaska) rainbow trout (Oncorhynchus mykiss) in the Susitna River providing baseline age and size composition statistics and stock structure information, for the Cook Inlet Rainbow Trout Management Plan.
Report of a study to estimate abundance of rainbow trout (Oncorhynchus mykiss) in the Agulowak and Agulukpak Rivers near Bristol Bay in southwestern Alaska during 1992, and also to estimate age, length and weight compositions.
Report summarizing findings related to estimates of age composition, mean length, and mean length-at-age of rainbow trout (Oncorhynchus mykiss), sampled by hoop traps, electrofishing, hook and line in the Susitna River Drainage (Deshka River, Lake Creek, Talachulitna River, Kashwitna River and Peters Creek) in south central Alaska.
