By Molly Kemp

For the past 14 years my spouse and I have run around like maniacs installing and maintaining stream temperature data collectors in Tenakee Inlet and Peril Strait salmon streams. 

Why? That is an entirely reasonable question.

This project grew out of the many summers we spent collecting otoliths from chum salmon carcasses, first for the Alaska Department of Fish and Game and later for the Sitka Sound Science Center.

We marched up and down salmons streams all over northern Southeast Alaska, dodging brown bears and rummaging through rotting fish.  

It was the best job in the world!

The summer of 2006 was  very hot and dry, and we witnessed disturbing changes in rivers we knew well. We were also struck by the uniquely resilient streams of upper Tenakee Inlet, where we observed higher flows and colder water.

While streams including the once-mighty Kadashan River were extremely short on water and returning salmon were huddled motionless and miserable in nearly stagnant pools, upper Tenakee Inlet streams seemed perfectly normal. Starting at Seal Bay, upper Tenakee Inlet streams had plenty of cold water and  were vibrant with happily spawning salmon.

The reason Upper Tenakee Inlet streams were in so much better shape seemed pretty clear.  Seal Bay, Long Bay, Goose Flats and Tenakee Head are mostly north facing, have intact forest cover, and are fed by higher elevation mountains with much deeper and longer lasting snow pack. Consequently those streams have more water, and colder water, during hot spells that leave other streams shrunken and warm.

The overall weather pattern in Tenakee Inlet seems to shift in the vicinity of Seal Bay. It’s not unusual for wind in the upper Inlet to be blowing in the opposite direction as the lower Inlet. While making daily skiff trips up Tenakee Inlet, we found the marine forecasts for Icy Straits more relevant than the forecast for North Chatham.

Everyone in Tenakee knows that the head of the Inlet is colder and gets more snow than the lower Inlet. We believe that these characteristics make upper Tenakee Inlet a refuge for salmon in a warming world. We see the pace of that  change accelerating yearly, and fear the implications for salmon on a regional scale.

The reality of a warming planet was forcibly brought home when we encountered a die-off in the Mole River on Admiralty Island. We estimated 8,000 fresh pinks and 150 beautiful chrome-bright coho had perished in the river mouth, after arriving on a tide that  left them stranded in a river without enough water and oxygen.

Cold water can hold more dissolved oxygen than warm water. Crowded fish in warm water may run out of oxygen and die, even if the temperature does not reach the limit of 21-23 degrees C that is considered lethal to salmon.

We started collecting stream temperature data in 2007 hoping to quantify our observations and demonstrate the unique value of upper Tenakee streams.  We bought battery powered temperature loggers with funds from  the Chichagof Conservation Council and  through Trout Unlimited , and  have installed and maintained  them with totally volunteer labor  in Seal Bay , Long Bay, Lower Goose, Tenakee Head , Kadashan and Trap Bay rivers.  For contrast we also installed  data loggers in  the south facing, heavily logged Sitkoh River in Peril Straits.

Our trips to download data have reinforced our observations of different weather patterns in Upper Tenakee Inlet. In the course of downloading data in April 2017 we found about four feet of snow on the ground at Tenakee Head, at the same time that flowers were blooming in the lower Inlet. 

Another year we found snow on Long Bay stream banks  in late June.

The graphs that follow show simple raw data – no rolling averages, no fancy analysis. The first graph compares temperatures of the streams in Long Bay and Sitkoh Bay in 2008.  The little up and downs are daily temperature variations, because this is raw data.  A statistician would smooth out the graphs, but I actually think it’s pretty interesting how much stream temperatures vary throughout the day.  It’s especially true when snow is involved. After a sunny day the stream temperature may actually go down when the snowmelt hits the stream.  On a cloudy day without snow melt, it might be warmer.

Sitkoh (green)- south exposure, relatively low elevation, heavily logged (Peril Straits)

Long ( blue) – north exposure, relatively high elevation and thus more snow pack, intact forest (Upper Tenakee)

This data appears to verify what we observed just by putting our hands in the water. The upper Tenakee Inlet stream was cooler all summer. Both gradually warmed up as the summer progressed,  tracking each other over time, with Long consistently cooler in all sorts of weather.

Now look at the next comparison, from the same period in the  blazing hot summer of 2019. That year low elevation watersheds like Sitkoh lost their snow pack really early, and started heating up fast, while the upper Tenakee Inlet stream in Long Bay plods along with cooler temperatures through the summer.  Sitkoh finally cools when rain returns in late summer.

Here’s another pair of comparisons. Seal Bay is one of the upper Tenakee streams. Kadashan is in the lower Inlet just a few miles away, but it is a relatively wide flat valley with relatively low elevation hills that lost all their snow pack by the end of May. The first graph shows Seal Bay compared to Sitkoh in the same hot summer. To me, this 2019 comparison looks very similar the Long Bay – Sitkoh comparison.

And next,  the Kadashan River compared to Seal. We fought tooth and nail to keep Kadashan from being clearcut back in the pulp mill days, and considered it the Inlet’s prize watershed. Kadashan’s value has not diminished, but things are changing.  The Kadashan temperature pattern looks an awful lot like Sitkoh in 2019. To me this confirms what we witnessed back in 2006, and it scares me half to death.

There seems to be growing recognition that people with long ties to a place may be aware of changes and patterns in a way that has real value in  the world of climate science. The job of identifying and protecting crucial pockets of habitat requires knowledge and commitment from all sectors.  

We think the water temperature data indicates  that during extreme hot weather periods like the summer of 2019 the streams of Upper Tenakee Inlet may offer a refuge to salmon while other island streams suffer from low flows and warming water. We have made the water temperature data we’ve collected available through University of Alaska Southeast and the Southeast Alaska Watershed Coalition, and hope to attract more research effort.  

Salmon tie every aspect of this ocean-forest world together.  We need to give salmon  every chance of refuge in a warming world, and recognize that places like upper Tenakee Inlet may have unique characteristics more valuable than any short term gain. The first step is making sure those watersheds  are kept intact.

We are deeply grateful for the guidance and donations of hardware from Trout Unlimited, the Norcross Foundation, the Southeast Alaska Watershed Coalition, and Cook Inletkeeper, and to many individuals who have helped with this project.