Kenai River | AK Fire Science Highlights

Fishing on the Kenai River (courtesy of John Winters)

Jordan Smith and Chase Lamborn, from Utah State University, recently completed a study of fire impacts on fishing in the Kenai River from the 2019 Swan Lake fire. Their study–funded by the Joint Fire Science Program— combined a literature review with interviews of local experts to identify impacts. The Kenai River is important: not only is it the most popular sportfishing destination in Alaska, averaging 275,000 angler days per year, it also produces 1/3 of the commercial salmon harvest in the Cook Inlet basin. Smith interviewed a small but diverse group of stakeholders who had extensive experience with the KR watershed, including agency resource managers, fishing advocates, people from non-profits, tribal members, and business owners. In addition to fire impacts, the study established a model of the Kenai River as a social-ecological system, which could be used to determine impacts from other kinds of disturbance.

Interviewees pointed out that a certain amount of luck, such as the lack of heavy rains post-fire to add big sediment loads as well as the fire’s location missing key Chinook spawning watersheds—limited any direct reported impacts of fire on fish. There were, however, impacts to resource users and businesses—primarily due visitors avoiding the area and road/river closures which restricted access during a brief, but critical, period of the summer. Nevertheless, a terrific early 2019 sockeye run (3-5x above preceding few years) helped to offset impacts on the sport fishery by encouraging anglers with high bag limits and success rates.

The literature review part of the study highlighted potential impacts to rearing and spawning habitats, water quality and fish passage. Most sobering are examples where populations failed to recover after fire, but these are the exception, not the rule. Adverse impacts are most likely from high-severity fires becasue they can lead to erosion and flooding. These events can induce loss of stream fishes, and generally require 3-10 years to recover when spawning habitat is affected. For the Kenai River, early-run chinook salmon were identified as the most vulnerable to this type of event. Although Smith et al. did not directly measure water temperature, stream flow, sediments, or mercury levels following fire on the Kenai, they provide a useful literature review of examples from elsewhere. They point out that with stream temperatures increasing and flows decreasing in the western continental US (a combination which can be deadly for fish), the threat of fire-related warming may become more serious in the future than it has been in the past.