Salmon research surveys temps, glacier melt, invasive species
PALMER — Changing rivers could affect salmon populations in Alaska, according to researchers at a symposium organized by the Mat-Su Basin Salmon Habitat Partnership.
Future changes to flow and temperature — two factors that affect salmon survival — were discussed Nov. 14 at the old Palmer Railroad depot.
The waterways that flow into Upper Cook Inlet from around the Matanuska and Susitna valleys contain the most salmon stocks of concern in the state, and much money and time has been spent trying to understand the runs and help restore them through various efforts.
The habitat partnership organized the sixth annual symposium to talk about science and conservation issues that affect salmon.
Cook Inletkeeper’s Sue Mauger shared the steam temperature research her organization is conducting in the Mat-Su area.
The group is planning long-term water temperature monitoring efforts on Wasilla Creek, Little Willow Creek, Fish Creek and the Deshka, based on the work it has done so far.
From 2008 to 2012, water temperature data was collected every fifteen minutes, although the work was primarily based on a seven-day rolling average of the temperature.
The state has certain standards regarding what temperatures are considered livable for salmon, and Mauger worked to determine when those were met and exceeded in 21 Mat-Su streams based on ongoing data collection.
Then, Mauger and her colleagues worked to determine what variables were at play when rivers were at various temperatures. Based on the modeling they did, they can try to predict future temperature changes, she said.
The team found that certain streams were cold and staying cold, while others are warming. Jim Creek and the Deshka, two popular salmon fishing waterways that have had issues with salmon returns, are warm and getting warmer.
The warmest waterways were those with a small slope and low elevation in a large watershed. Steeper rivers, and those at a higher elevation, were colder.
Mauger’s research is also underway elsewhere in Cook Inlet, including on the Kenai Peninsula, and the team also looked at the relationship of air and water temperatures to feed into an Inlet-wide modeling effort.
Mauger said that in the future, research could be done to examine how salmon utilize cold pockets in warm streams, and how riparian habitat can provide shade to cool warm streams. The habitat partnership could also use the information to help focus its protection on cool streams, she said.
Alaska Pacific University’s Mike Loso talked about his work to understand the effects of melting glaciers.
Glaciers are a major contributor to many of the state’s rivers, including some of those in the Mat-Su region. As they melt, they change the flow in those streams, potentially affecting salmon runs.
Loso’s work focuses on the Eklutna Basin, comparing the flow on the east fork and west fork. The west fork is nearly half fed by ice melt, while the east fork is only about 13 percent ice-fed.
His work so far has shown that the more-glaciated fork, which has also been melting significantly in recent years, has different flow characteristics than the fork that is less reliant on a glacier.
As glaciers retreat, rivers have more early water, less mid-season water and bigger fall floods, Loso explained. Initially, there is more run-off, but eventually, the melting will slow and there will be less water entering the river each year.
The implications of that, he said, are that for the next few decades, certain rivers could have increased flow, but eventually that will taper off, and in the long-term, those rivers could have less water in them.
Flooding and flow can both affect salmon habitat and populations. It also has implications for potential hydropower projects, Loso said.
While glacial melt and warming rivers are hard to change locally, partners also talked about their work on habitat, a third major factor for salmon survival.
Corrine Smith, who works for The Nature Conservancy, discussed the habitat partnership’s future plans.
“Our focus is on habitat,” Smith said. “We want to make sure, as Howard Delo said, when the fish come back they have some place to go.”
Bill Rice, who works for the U.S. Fish and Wildlife Service, talked about the water reservation program for area waterways, and the work the group has done on estuaries.
“There’s been a lot of activity here,” Rice said, noting that more than 7,000 acres have estuary habitat have been protected since 2005.
Rice also talked about work on policy and management in the Mat-Su Borough, including management plans for the Matanuska River, wetlands and storm water that all address fish habitat.
Several participants also talked about invasive plants and northern pike. That fish is thought to prey on and outcompete salmon, and is considered a threat to salmon populations.
On Alexander Creek, the Alaksa Department of Fish and Game, or ADFG, is working to eradicate northern pike. Right now, the project is primarily based on catching the pike in nets and removing them from the creek, and tracking some with radio telemetry to better understand where they go and how they survive.
Catching and removing the fish will likely continue well into the future, but the goal is to reduce the number so that it is a smaller effort, according to ADFG’s David Rutz.
Another pike project is at Big Lake, where the U.S. Fish and Wildlife Service plans to catch them through the ice this winter, and is trying to capture and radio tag the pikes to see where they go.
A better understanding of their patterns could help focus eradication efforts.
Louisa Branchflower from the Palmer Soil and Water Conservation District presented her work to map Cottonwood Creek, and surveying for invasive plants along the way. This past summer, Branchflower and her colleagues surveyed the upper portion of the river, and found reed canary grass, which can take over salmon habitat, through a significant stretch.
Molly Dischner can be reached at [email protected].