Salmon love snow; warm temperatures stress them out

Refuge Notebook
In-stream data loggers are used to record water temperatures every 15 minutes all summer long.

Many of us were bracing for a dramatic and messy break-up this year. Ice jams, flooding, clogged culverts, and rutted side roads seemed inevitable after all the snow that fell this winter. Instead, it has been a very gradual melt with little rainfall to speed up the process.


This welcome surprise makes our lives easier and also bodes well for our salmon this summer. With above average water levels stored in our hills during the winter, and the slow release this spring, we'll have more in-stream flow this summer allowing better fish passage in smaller creeks and cooler water temperatures.

And we'll know just how cool those temperatures are because this is the fifth year in a row that community organizations, Tribal entities, federal and state agencies, and a cadre of wonderful volunteers on the Kenai Peninsula -- and across Cook Inlet -- will work together to monitor temperatures in local salmon streams.

Until about 10 years ago, few people thought about temperatures in salmon streams. We're in Alaska -- healthy salmon, cold streams, no problem. But as the on-the-ground evidence of rapid climate change became more compelling, and a number of local water quality projects reported higher than expected in-stream temperatures, interest began to grow.

Why should we care about warming stream temperatures? Because warm temperatures stress salmon, making them more vulnerable to pollution, predation and disease. At all life stages, warm temperatures can have profound physiological or behavioral effects on wild salmon.

So when we talk about warm temperatures, what are we talking about? In areas where eggs are incubating in gravel or salmon fry are emerging, water above 55 degrees Fahrenheit is considered warm and stressful. In juvenile rearing areas and adult migration routes, temperatures above 59 degrees Fahrenheit feels to a salmon like the first day you get off the plane in hot and humid Houston -- it's hard to breathe and you're lethargic.

It took people by surprise then when stream temperatures on the Kenai Peninsula peaked above 68 degrees Fahrenheit in 2004 and 2005. While we found these warmer streams throughout the Cook Inlet watershed, they represent just a fraction of the salmon streams in the basin -- most of which have little or no water temperature data on record.

In 2001, the U.S. Geological Survey produced an important report compiling the limited historical stream temperature data from Cook Inlet streams, as well as air temperature data from seven climate stations. Based on the historical relationship between air and water temperature data and available global circulation models at that time, their conclusion was that non-glacial streams were expected to rise 5.4 degrees Fahrenheit or more in the coming years. For streams already above 68 degrees in 2004, this was sobering information.

The question it raised for me was: would all non-glacial streams warm at the same rate in relationship to increasing air temperatures, or were some streams -- such as the ones I was studying on the lower Kenai Peninsula -- likely to warm faster?

This question led me to work with other ecologists and resource managers to design the Stream Temperature Monitoring Network to help Alaskans understand how climate change -- and increases in air temperatures -- would affect water temperatures in a variety of Cook Inlet salmon streams.

Because glacial systems are generally very large with dynamic braided channels and are likely to remain cool in the near future, we concentrated on non-glacial systems. We selected 48 streams -- half of which fall within the Kenai Peninsula Borough -- which represent a range of watershed sizes, forest and wetland land covers, and headwater elevations.

We started collecting data in 2008. Cook Inletkeeper, Kenai Watershed Forum, and the Kenai Fish and Wildlife Field Office are working together to collect data in streams on the Kenai National Wildlife Refuge, including Hidden Creek, Swanson River, Nikolai Creek, and Funny River. We use in-stream data loggers and program them to collect a temperature reading every 15 minutes all summer long.

In addition to collecting temperature data, we are also working with climate scientists to understand how future air temperatures are likely to change by season. We are learning that July air temperatures may increase as much as 9 degrees Fahrenheit up in the Susitna River valley.

But more importantly for us on the Kenai Peninsula and west side of Cook Inlet, increasing winter air temperatures may put us above freezing for longer periods of time, thus drastically reducing snow accumulation.

In the summer of 2012 we will reach our 5-year data collection goal to capture recent annual variation. These data will play an important role in identifying the most temperature-sensitive salmon streams in Cook Inlet. With this information, we can then prioritize our conservation and restoration efforts to give our Alaska wild salmon a fighting chance as thermal change continues.

For our snow-loving salmon that need a deep snowpack to feed the rivers all summer long, the future looks warm. And for our salmon-loving communities that rely on healthy fish populations to feed our families and local economies, the future requires our attention now. As your memories of snow blowing and shoveling fade from this past winter, appreciate our exceptional snow year and the gradual spring break-up. Our salmon will be breathing easier, at least this summer.

Sue Mauger is the Science Director at Cook Inletkeeper in Homer and coordinates the Stream Temperature Monitoring Network ( You can find more information about the Kenai National Wildlife Refuge at or


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