By Roy Iwai, Multnomah County Water Quality Program
It’s a battle of natives and invaders. No, I’m not talking about American politics. You’ve probably read enough on that in today’s newspaper. This is a fight for stream habitat between non-native fishes and native salmon species in the upper Beaver Creek watershed. It’s a fight that humans unfortunately created out of self preservation, out of naivety, and without consideration for the consequences of these actions on our salmon’s survival.
First, let’s celebrate
There is a celebration going on at the Troutdale and Gresham border, where Multnomah County is installing a new bridge at Cochran Rd. This project replaces a 90 year old concrete box culvert with a sixty foot span bridge. The new structure sits high above the creek, complete with areas to remove pollutants from the stormwater that collects on the deck. There is a new stream channel underneath, where there was a concrete culvert before. This habitat has gravel, cobble, and boulders, like the natural channel upstream and downstream. Deer, coyote and beaver will travel along the stream here with ease, too.
The Cochran Rd bridge is part of the County’s commitment to help restore salmon in Beaver Creek. The project was conceived with one goal in mind: to remove the barrier of upstream migration for salmon. Like the Stark St Culvert Replacement project, completed in 2017, the Cochran Rd culvert was on the state priority fish barrier list. Removing these two barriers restores access into upper Beaver Creek for endangered steelhead trout, coho salmon, and a variety of other native fishes
Beaver Creek is a small stream, yet it is an important salmon stream in the Sandy River Watershed. It produces between 4 – 9% of the juvenile coho salmon, among the major tributaries of the Sandy River Watershed. Allowing fish to migrate upstream and downstream freely in all the seasons provides a major lift to these juvenile salmon that spend a year or more in the stream before heading out to sea to mature.
But, there’s a new fish in town.
Local biologists believe that sometime between 2010 and 2015, green sunfish were illegally introduced in the upper tributaries of Beaver Creek, presumably as mosquito control. Green sunfish are a warm water fish, akin to bluegill and pumpkinseed, which are native to the southeast United States. These fish are often stocked in lakes and ponds to feed smallmouth and largemouth bass.
During the construction of the Cochran Rd bridge in August 2019, biologists rescued and relocated all the fish in the water in and around the construction zone prior to beginning construction. This is a precautionary step before beginning work in a stream known as a “fish rescue”. They netted and removed over 300 green sunfish. This number dwarfs the number of native fish netted. This was a surprise. Two years earlier, during the Stark St culvert project, the number of all sunfish species combined was around fifty fish.
What does this mean for salmon and steelhead?
Despite the new habitat access, there will be serious competition for habitat and food between species. Sunfish and salmon species all rely on a variety of insects, worms and snails in the water. More sunfish means more competition for limited food that flows downstream.
Streamside restoration may be the key to give salmon species an edge on this competition.
Green sunfish are warm water species that thrive when the water is warm, and the flow is sluggish. They need temperatures above 70 F degrees to spawn. Salmon on the other hand prefer faster, colder water as they are native cold water fish. They thrive in water below 64 F degrees. Stream temperatures in Beaver Creek tend to be too warm in summer now. This gives the sunfish an advantage. However, streamside re-vegetation is occurring at a vigorous pace through the East Multnomah Soil & Water Conservation District’s Stream Care program. With more trees, we may help these salmon to survive.
Stream Care is a free program for local streamside landowners, where native plants are planted and maintained along streamsides for five years. If you are rooting for the salmon’s recovery, and you need more shade along your section of stream, please join the Stream Care program! https://emswcd.org/
If you are not a streamside landowner, the Sandy River Watershed Council has some fun volunteer opportunities for you and your family to help restore Beaver Creek. Restore Beaver Creek with the SRWC and SOLVE on December 7th, 2019 and February 8th, 2020.
Let’s work together and help restore our Beaver Creek. Go steelhead and coho!