Home Biologist Hot, Dry Summer Impacts Chinook Salmon in Chehalis Basin

Hot, Dry Summer Impacts Chinook Salmon in Chehalis Basin

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By Dan Hammock / Le Monde Quotidien

Dead and dying spring chinook salmon were found in the Newaukum River basin this summer.

The root of the problem lies in the historic Pacific Northwest heat wave this summer and the ongoing drought.

The Chehalis River watershed, which covers parts of Lewis, Thurston, Grays Harbor and Mason County, has had no measurable rainfall for 85 days.

This exceeds the previous 55-day rainless streak established in 1960. The Washington State Department of Ecology called March to May 2021 the second driest on record since 1895.

The heat wave and lack of rain left many waters warmer than usual and lowered water levels in many of our lakes and rivers.

What effect has this hot, dry summer had on our Salmon in the Chehalis River Basin?

According to Lea Ronne, a fish biologist with the Washington Department of Fish and Wildlife, who studied the Newaukum River streams in Lewis County this summer, “23 spring chinook were said to have been killed, the heat being the main contributing factor. Water temperatures in parts of the basin were as high as 88 degrees Fahrenheit. Salmon is a cold water species and begins to feel stress at 64.4 degrees Fahrenheit.

Lea continued, “In hot weather, salmon depend on water from the lower layers of deeper pools that is cooler than the rest of the water to provide a ‘cold water refuge’.

Refuges are areas where species can survive in adverse conditions.

“This summer, many people also sought refuge from the heat and swam in the deeper Chehalis River and its tributaries. Swimming mixed the water layers, causing the cold water layers to shed from the bottom of the river.

“These human conflicts coincided with the movement of the spring chinook and were the ‘straw that broke the camel’s back,’ as these spring chinooks had been in the freshwater river system for some time and more sensitive to the stress and illness, ”according to Lea.

What can be done in the future to protect salmon habitat while improving the resilience of salmon?

The main way people can prevent such mortalities from reoccurring is to protect and help create additional deep pools for salmon. You can help by:

• Use water wisely. The less water you use in your home and garden means more water is left in rivers, streams, or groundwater. Groundwater recharges our streams and rivers to maintain stream flows and provide cooler water temperatures.

• Protect or plant native vegetation along the riparian corridors of our streams and rivers. Large trees and overhanging vegetation are essential to keep the water in our streams and rivers fresh.

• Leave or place large logs in the river. Large woods help create habitat complexity and deeper water pools with cold water salmon can take refuge.

• If you observe dead or dying fish in the summer, please report it on the State Department of Fisheries and Wildlife’s Environmental Fish / Shellfish Die-off Report form which can be found at: wdfw.wa .gov.

• After documenting or reporting dead or dying fish, push the fish downstream to release key fish nutrients into the river that native plants and wildlife require. It also protects pets from potentially dangerous contact with salmon carcasses.

Rain is in the immediate forecast, and we could get higher than normal rain levels in the coming months, according to the state climatologist’s office.

For more information on how to protect salmon in your local rivers and streams, please contact Kirsten Harma, Chehalis Basin Main Entity Coordinator at 360-488-3232 or email kharma@chehalistribe.org. Or contact Lea Ronne, Fish Biologist III, WDFW at lea.ronne@dfw.wa.gov.


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