Study reviews potential climate impacts on Kenai River salmon

Study reviews potential climate impacts on Kenai River salmon

Though the Kenai River’s salmon populations are still healthy compared to other Pacific salmon populations, a number of climate change-influenced factors could threaten them in the future.

A study published in the October 2017 issue of the journal Fisheries focuses on the Kenai River as a case study for what may happen to healthy salmon populations as the climate continues to change. Air and water temperatures have been warming over the past 50 years, according to weather records, and other factors in the environment may put stress on salmon throughout their lifecycles as well, the paper’s authors wrote.

The Kenai Peninsula’s economy heavily relies upon salmon abundance for the commercial fishery, sportfisheries and personal-use fisheries. When salmon are more scarce and fisheries managers have to restrict or close sportfisheries, multiple sections of the economy take note — sales tax revenue in the city of Kenai during the personal-use dipnet season may drop, and sales at guided angling services may drop. In the commercial fishery, when the salmon harvest came in significantly below expectations in 2016, reaching only about half the volume of salmon harvested the year before, it pushed total work earnings down on the peninsula, according to the 2017 Situations and Prospects report produced by the Kenai Peninsula Economic Development District.

The authors, who are all from Alaska and include Kenai National Wildlife Refuge supervisory biologist John Morton, detail the potential changes for salmon habitat as well as population trends and implications for management.

Lead author Erik Schoen of the University of Alaska Fairbanks wrote in an email that the researchers wanted to make a broad picture of the available research accessible to the public and to policy makers.

“Alaskans are really interested in fish and wildlife issues, and we’ve been watching all these changes unfold around us,” he wrote. “There has been a ton of great research to document changes on the Kenai, but some of it is only available in technical reports or online databases, and it’s not always easy to see the big picture.”

Major considerations for changing habitat are retreating glaciers, water temperature, increased risk of flooding and additional development and traffic along waterways. Air temperatures on the peninsula have trended warmer in all seasons except fall since the 1960s, according to records from the weather station at the Kenai Municipal Airport, and glaciers attached to the Harding and Sargent icefields — which contribute runoff to the Kenai River — have been retreating and losing mass consistently for the last-half century, with losses accelerating in the past approximately 20 years.

Non-glacial rivers are more subject to temperature fluctuations from warmer air temperatures than glacially fed rivers, according to the study, which drew from stream temperature research by Cook Inletkeeper Science Director Sue Mauger. Some short-term effects may be reduced zooplankton and sockeye salmon production as well as other microorganisms. Other net effects of retreating glaciers on salmon populations aren’t entirely clear and may not all be negative — for instance, additional meltwater flow can moderate water temperatures and add additional connectivity between river channels, according to the study.

“It remains unclear whether glacial mass loss will enhance or reduce the overall salmon productivity of the Gulf of Alaska region,” the study states.

At the same time, pressure on the stream systems has increased with more foot traffic, boat traffic and development within one kilometer of the banks. The population of the peninsula has grown by nearly 10,000 people since 2000, with the greatest density of people in the central peninsula area. Development has also impacted wetlands, which provide nutrients to streams and buffer streamflows by storing extra water and releasing it during dry periods, according to the study.

Human development has increased 20-fold in the Kenai River watershed between the 1980s and 2013, according to the study. More than a third of that development was concentrated in the area within one kilometer of the river between Skilak Lake and Cook Inlet. Human development has led to the introduction of invasive species such as elodea and northern pike that can harm salmon as well, according to the study.

Salmon populations naturally fluctuate over time and depend on a variety of conditions, both freshwater and marine. While some of those conditions are uncontrollable, others are based on management decisions, such as bag limits and fishing seasons. Mixed stocks fisheries like the Kenai can provide a challenge to management as well, leading to complex regulations on both commercial and sportfisheries.

Future conditions may be unpredictable and managers and policymakers should expect them, the authors wrote in the study. Large hatchery releases may threaten wild stocks, both through density reducing oxygen in the water and through competition for food. Managers may also want to consider protecting areas that are not productive salmon habitat now, but could be in the future, such as high glacial streams like the Snow River, the authors wrote. Also, riparian lowlands, which cover much of the western Kenai, appear as a priority, according to the study.

“On the Kenai Peninsula, lowland streams fed by groundwater and wetlands are considered the most vulnerable category of fish habitat, facing threats from a warming climate, invasive species, riparian development, and road crossings lacking adequate fish passage,” the study states.

Fishing-dependent communities like the Kenai may become more resilient to threatened stocks by diversifying their catches, but that could be challenging, especially within a limited entry system, Schoen wrote in an email. The take-home message from the study is that despite the worldwide scale of climate change, local decisions can still have impacts, he wrote.

“Salmon are incredibly adaptable, and they are facing serious challenges and new opportunities all at the same time,” he wrote. “We should expect some surprises in how they respond. Some of the salmon runs that Alaskans have relied on for generations are probably going to decline, but other runs may become more productive, and we have a chance to shape that with strong habitat protections. It’s encouraging to see people working hard to protect habitat on the Kenai and boosting the odds of our salmon runs staying strong.”

Reach Elizabeth Earl at elizabeth.earl@peninsulaclarion.com.

Study reviews potential climate impacts on Kenai River salmon
Study reviews potential climate impacts on Kenai River salmon

More in News

The Homer Spit stretching into Kachemak Bay is seen here on Thursday, Dec. 10, 2020 in Homer, Alaska. (Photo by Megan Pacer/Homer News)
Homer woman indicted over seaplane incident

Marian Tillion Beck was indicted on charges of negligent operation of a vessel and attempted interference with the navigation of a sea plane

Soldotna High School can be seen in this Sept. 2, 2021, photo, in Soldotna, Alaska. (Photo by Jeff Helminiak/Peninsula Clarion file)
‘Little Sweethearts’ family dance to debut at SoHi

The event will be hosted by SoHi’s freshmen student council

Soldotna City Council members interview city manager applicant Elke Doom (on screen) during a special city council meeting on Monday, Jan. 30, 2023. (Ashlyn O’Hara/Peninsula Clarion)
Doom, Bower named finalists for Soldotna manager gig

The two will visit Soldotna for in-person meetings on Feb. 7 and 13, respectively

The northern fur seal rescued by Alaska SeaLife Center staff is seen on Jan. 31, 2023, at the Alaska SeaLife Center in Seward, Alaska. (Photo courtesy Kaiti Grant/Alaska SeaLife Center)
Northern fur seal pup admitted to SeaLife Center rescue program

The pup was reported by Sitka residents using the center’s 24-hour stranding hotline

The Kenai Community Library children’s section is seen on Tuesday, Oct. 26, 2021. (Camille Botello/Peninsula Clarion)
Literary competition returns to local schools

Battle of the Books aims to instill in kids a love of reading

Clarise Larson / Juneau Empire
Climate activists hold a rally outside the Alaska State Capitol Friday afternoon in advocacy for legislative action to improve Alaska’s renewable energy development and future sustainability.
Climate activists hold rally near the Capitol

Statewide organizations advocate for legislative action

Shanon Davis, the executive director of the Soldotna Chamber of Commerce, hands out candy during the Sweeny’s St. Patrick’s Parade in Soldotna on March 17, 2022. (Camille Botello/Peninsula Clarion)
Davis to step down as Soldotna chamber head

Davis oversaw the implementation of Soldotna’s “Holding Our Own,” shop local program

Golden-yellow birch trees and spruce frame a view of Aurora Lagoon and Portlock Glacier from a trail in the Cottonwood-Eastland Unit of Kachemak Bay State Park off East End Road on Sunday, Oct. 3, 2021, near Homer, Alaska. (Photo by Michael Armstrong)
State parks advisory boards accepting applictions

Alaska State Park advisory boards provide state park managers with recommendations on management issues

Most Read