The Squaxin Island Tribe is collecting year-round temperature data on dozens of streams in deep South Sound.
“Salmon need clean, cold water in order to thrive in streams” said Erica Marbet, water resources biologist for the tribe. Using instream temperature monitors, or thermographs, the tribe has been monitoring temperatures in local streams for years.
Water above 70 degrees can be lethal to salmon. Warm water can spawn diseases and carries little of the dissolved oxygen that salmon need to breathe. Because salmon are cold-blooded, warm water increases their metabolic rate, forcing them to use energy needed for survival. If a returning adult salmon can’t find enough cool water, it may die before it has a chance to spawn.
By collecting data year-round, the tribe can see trends over time. “This kind of baseline monitoring is important because we’re trying to see what is happening over the long term,” Marbet said. “We can’t tell what’s really going on with only a few months of data.”
Temperature data is especially important for coho salmon because they spend at least an extra year in fresh water as juveniles. South Sound coho populations have been on a slow downward trend.
“During the times of low summer flow and high temperature, rearing juvenile salmon can die during their first year,” said Marbet. “That makes it all the more important for us to know where that warm water is.”
The tribe is also tying their data into a regional climate change database. The U.S. Forest Service is building a regional database across six western states, tracking the impact of climate change on stream temperatures. “By putting our data into this regional effort, we can see the tribe’s area in the right context,” Marbet said. “We also should be able to see how future climate change will impact these streams that are so vital to the tribe.”
In addition to temperature data, the tribe collects various types of water quality data on a number of creeks in the area. The tribe also operates several out-migrating juvenile salmon smolt traps and conducts adult salmon spawning surveys to track salmon populations.
“Temperature can act as a physical barrier to salmon in fresh water,” Marbet said. “A few weeks of hot, dry weather during a critical part of the year can have a dramatic impact on how many salmon a creek can produce.”