By Jenny Neyman
When Sue Mauger, a stream ecologist with Cook InletKeeper, came to Alaska and took her first water temperature reading on the Anchor River, she thought she knew what she would find. It’s Alaska, after all, the land of glaciers and polar bears.
Lo and behold, though — the water wasn’t cold.
“I didn’t know if maybe I was just a little bit clueless, because I had assumed that, in Alaska, salmon streams were going to be very cold. And I would throw my thermometer in there and they would be in the 50s, high 50s, heading toward 60, and that just surprised me,” she said. “So finally, in 2002, I decided, ‘All right, I need to figure out how warm these systems really are.”
Thus began a project of gathering five years of temperature data on 48 nonglacial streams throughout the Cook Inlet watershed. She presented her findings at the Kenai Change conference on the developing effects of climate change on the Kenai Peninsula, held Saturday at Kenai Peninsula College’s Kenai River Campus.
The results of Mauger’s stream temperature monitoring project paints a picture that is increasingly chilling for salmon as the forecasted climate trend continues warming.
“And what I found was that, yes, we do actually have salmon-bearing systems in Alaska that are warm, and that are at temperatures that are stressful to salmon,” she said.
But nature is stressful, right? Especially to a creature that’s an integral link to the food chain. Well, there’s a difference between the stressors that creatures are adapted to handle, like migrating upstream to spawn, and out-of-the-ordinary stress that they aren’t used to enduring.
“Salmon are cold-water fish, and they thrive in colder waters, and when you start to add warmth to that water, they go through a lot of stress throughout their life cycles,” she said.
Eggs and fry don’t survive as well in warmer water, and juvenile salmon have reduced growth rates. Warmer water can cause salmon smolt to migrate out to salt water sooner, which can lower their survivability at sea. And salmon in warmer water are more susceptible to pollution, predation and disease. It’s just not what they’re acclimated to.
“Think of, you know, when we Alaskans go to Hawaii — the first couple days, you’re just kind of this big, blubbery mess because it is so hot you can’t even move. Well, a lot of the things that we’re dealing with are similar to what the fish are trying to deal with,” Mauger said.
Water at around 55 degrees stresses juvenile salmon, at 59 degrees it affects adults and at 68 degrees it stresses all life stages of salmon.
“They aren’t dying necessarily, in stream. These are generally sublethal effects, but they all have an effect on the long-term productivity of these populations,” she said.
The 48 Cook Inlet streams tested showed a wide range of temperatures. Not all were in the danger zone of affecting salmon, but some consistently were. Others got there during the summer, and all are going to be subjected to the continuing trend of increasing air temperatures that’s forecasted in coming years.
Mauger describes four categories of streams in her survey. Some are already warm enough to be stressful to salmon and are sensitive to increases in air temperature, meaning they will continue to warm. The Swanson River falls in that category, as a lowland system with a large watershed and lots of wetlands and connected lakes.
Other streams, like the Moose River, are warm but don’t tend to change much with air temperatures. The Moose, like the Swanson, is a big system with a lot of wetlands, but it’s at a higher elevation and is fed by snowmelt that helps keep it cool.
Cold streams that are sensitive to air temperatures are likely to get warmer as air temperatures increase. The Anchor and Ninilchik rivers, and Deep, Stariski and Crooked creeks are cool now, but probably won’t stay that way for long, she said.
Of the 20 Kenai Peninsula streams Mauger monitored, 40 percent are sensitive to air temperature increases, as much as 0.9 degree in water temperature for every one degree rise in air temperature. And warming appears to be happening at a faster rate than scientists initially estimated. A winter temperature model for the year 2090 on the Kenai Peninsula, estimated in 2010, predicts that temperatures from December to February on the lower Kenai Peninsula by the end of this century will be above freezing.
“Well, of course, this year we were above freeing,” Mauger said. “These were done based on, at the time, what they considered to be the most middle-of-the-road of the scenarios. Well, it’s clear already from this and many other modeling efforts that that middle of the road is way too optimistic, and that we’re somewhere in between the worse case and the middle of the road at this point.”
But there also are cold-temperature streams that aren’t as susceptible to rising air temperatures on the peninsula. These, like Quartz Creek, tend to be at high elevations with lots of snowmelt and lots of forest cover.
“That’s a system that is going to be cold for a very, very long time and fortunately there are a lot of streams on the Kenai Peninsula because of our terrain that will fall in this category. Which is great,” she said. “… The insensitive streams — those are systems that are cold and will be cold in the future and those will become really important refugia for salmon in the future. So as we get into temperatures that are very stressful, those systems will be incredibly important for keeping those populations viable through long patches of warm climate.”
A warming climate isn’t just affecting water temperatures. Less snowpack means less water volume, which can impede fish passage. Higher temperatures mean more glacial melt, which contributes more turbidity to lakes and streams. Declining forests can negatively affect the health of streams. Ocean acidification from increased carbon threatens salmon in the marine environment. And more and stronger storms in the fall and winter can scour gravel beds and dislodge entire populations of salmon eggs.
But the future of fish on the Kenai Peninsula isn’t all doom and gloom, Mauger said. For one thing, the Kenai Peninsula’s habitat is still in pretty good shape. And there are things humans can do to keep it that way, she said, such as preserving wetlands, making sure culverts and bridges don’t block fish passage, limiting development along waterways to preserve shade and good groundwater connection to the streams.
“We live in a relatively intact landscape, and that is probably our best hope for our salmon is to continue to provide them high-quality stream habitats, to have diversity of habitats, and creating resilience by having healthy habitat,” Mauger said.
After all, she said, it isn’t just Cook Inlet’s salmon populations at stake, it’s the perseverance of Cook Inlet’s culture, economy and lifestyle.
“This isn’t a fish tale, this is about the people, and this is about food security, this is about our way of life and it’s about how we identify ourselves as Alaskans and as people of the Kenai Peninsula,” she said. “So I hope that these are the things that are really driving why we have efforts like this today, and hopefully these are the reasons that will propel us to move forward beyond today.”