Susitna Basin Rainbow Trout Research

Study Area/Background

The lower Susitna River basin of Southcentral Alaska, is the focus of our study, and is a network of turbid, glacially influenced mainstem rivers and clear-water, runoff-fed tributaries (see map below). The Susitna River ultimately drains into the Upper Cook Inlet of the Gulf of Alaska.

The Susitna River basin is home to substantial spawning runs of Chinook, pink, chum, sockeye, and coho salmon, as well as a large population of resident rainbow trout (see below pictures). These salmon and trout are the targets of a popular sportfishery. Fishing for rainbow trout in Susitna basin is catch-and-release only for spawning-size adults, and trout are subjected to moderate pressure from fly fishermen during the summer months (June-September). Trout in the Susitna basin rely heavily on salmon egg subsidies for food, and are dependent on healthy salmon spawning runs to gain sufficient energy reserves to survive the winter months.

Recent and impending human development in the Matanuska-Susitna Region will likely have an effect on fish populations in Susitna River tributaries. The Susitna-Watana hydroelectric dam scheduled to begin construction as soon as 2015 may have long-reaching effects on the Lower Susitna River ecosystem, possibly affecting rainbow trout and salmon populations. Future anthropogenic land development (expected to double within the next 50 years) in the Susitna River valley may cause greater sedimentation, thinning of important riparian zones and increased sportfishing pressure. In light of these developments, it is necessary to gain an understanding of the movements and habitat utilization of rainbow trout in the Susitna Basin to identify potential issues that may affect this economically and ecologically important species.

Research Questions

1. What habitats are used by rainbow trout during different seasons and hydrological conditions?

2. Do trout move between tributaries in the Susitna River basin?

3. Are there significant sex-biased (male vs. female) patterns of habitat use and movements?

Methods

We implanted radio telemetry tags into adult rainbow trout larger than 16 3/4 inches in length during 2003 and 2013-2014. Trout were captured in Willow, Montana, and Chunilna (Clear) Creeks and the Kashwitna River, and were tracked from the air and on foot over the course of one year. Fish locations were used to identify movement patterns and important habitats for rainbow trout during overwintering, feeding, and spawning seasons.

Video of a rainbow trout released back into Willow Creek after surgery:

Results

See 'Results' page for information!

Funding/Support

Primary funding for this project was provided by the Alaska Department of Fish and Game and the Mat-Su Basin Salmon Habitat Partnership. Other support and affiliate entities are included below.