How this year’s high summer temperatures pose a threat to local trout, salmon

Local trout and salmon in the Spokane River are in danger this summer from recent hot weather.

Jule Schultz, the Waterkeeper for Spokane Riverkeeper, said that because of the recent heat wave and a warmer-than-average spring, “we were actually getting pretty high water temperatures already.”

High water temperatures are dangerous for certain species of fish, namely redband trout and salmon.

“The reason we have the water quality standards that we do in Washington state … are meant to protect our fish, which are very sensitive to temperature,” Shultz said.

Staci Lehman, a communications manager for the Washington Department of Fish and Wildlife, said higher water temperatures stress fish.

“We asked folks when temperatures get warm like this to fish earlier in the morning when the temperatures are lower,” Lehman said.

Lehman works with Spokane County and Newman Lake, and said that “temperatures have jumped up in the past couple days, which means the dissolved oxygen in the water goes down … and so that’s kind of when you start seeing issues.”

High water temps are dangerous for local fish for a few reasons. As temperatures increase, dissolved oxygen depletes, which is detrimental for fish populations.

High temperatures also “can cause issues like harmful algae blooms and increase the effects of toxics like pesticides or metals,” according to Schultz.

Algae blooms further deplete oxygen, and certain metals such as copper can adversely affect how fish survive. Copper, for example, harms the immune systems of fish, disrupts migration and negatively affects internal organs. Warmer water temperatures accelerate already harmful threats to fish.

However, the Spokane River’s temperature is not uniform. Schultz points out that at Sullivan Road, “the local aquifer flows into the river, cooling water temperatures in certain areas. And so downstream of Sullivan Road, we actually have pretty cool water temperatures. That oftentimes, even during very hot times of the year, meets our water temperature standards.”

These cooler parts of the river provide a safe haven for trout and other fish, Schultz said. But trout are still forced out of other areas they usually inhabit.

Even downstream, where temperatures are cooler, some areas are still considered too hot for some fish. Temperatures recently reached 66.5 degrees in a certain part of the river, which is around four degrees higher than what is considered optimal for redband trout.

Higher water temperatures occur because of higher air temperatures, and Schultz says that “nighttime air temperatures lead to high water temperatures.” This means that not only do daytime highs matter, but nighttime lows are more impactful on water temperatures.

Schultz spoke of the hot temperatures in certain areas of the Spokane River such as in one part of Spokane Valley, where the water reached 80.6 degrees.

Schultz said that he and his team have been monitoring water temperatures for around 10 years and have seen a slow but noticeable increase.

He said that local groups are working to restore not only streamside vegetation that cools down water, but floodplains and basins in the area to help protect local fish.