Watching streams to see how salmon respondNovember 18th, 2009 by cdunagan
I often play a guessing game that involves rainfall and streamflows: Are we getting the right amount of rain to help our salmon, or are the rains causing streamflows to be too high or too low?
It is easy to come up with an answer when we’ve had hardly any rain. The streams are running low; salmon are ready to swim upstream; and fish in the stream are obviously struggling through shallow water. We’ve seen this kind of condition in early fall during many recent years.
When can we say we’ve had enough rain? Well, certainly when a wide variety of streams and rivers are flooding over their banks. But because of the complexity of natural systems, there may never be a “just right” level for salmon.
I was up above Wildcat Lake in Central Kitsap yesterday,
discussing the conditions with Jon Oleyar, a biologist for the
Suquamish Tribe. Thanks to recent rains, coho salmon are well
distributed throughout the Chico Creek watershed, which includes
Jon was excited to find coho far up in streams where he has rarely if ever seen them. The bad news was, for the stream we were watching, the fish seemed to be blocked by a perched culvert where water was gushing out — a culvert that kept the fish from reaching a beautiful stream with overhanging vegetation and plenty of spawning gravel.
Apparently, few fish have made it upstream of this culvert, Oleyar said, because he has never seen a dead salmon on the other side of the road. And while it was exciting to see large salmon get this far upstream, it was disappointing to find their path blocked.
“I had a smile on my face until I realized they couldn’t get through,” Jon told me, and I quoted him in a story I wrote for today’s Kitsap Sun.
For these coho, heavy rains of the past few days have brought them to new habitat. Yet the flows through the pipe have kept them from going any farther. I will watch as the flows drop over time to see if there is a level that allows them to swim through — although they will need to leap up into the culvert to do so.
Meanwhile, the main channel of Chico Creek, five miles downstream, was flowing high and fast, although it wasn’t flooding. I’m not sure if this is good or bad.
Rocks and log weirs, which can be obstacles at low flow, were now submerged, presenting no obstacle at all. On the other hand, resting pools were gone, and salmon were fighting the current and probably using up their energy. Was the flow high enough to wash salmon eggs out of the gravel? I don’t have a clue.
It is easy to see why biologists talk about the value of “structure” in the streams. Fallen trees normally don’t block the entire stream. Even when they do, it is just a short time before the force of the water creates openings for salmon to swim through. Beneficiallly, extensive “structure” creates pools for salmon to rest and hide, no matter how high the flows may be.
The answer to the question of “too much or too little rain?” seems to vary from stream to stream and even upstream and downstream in the same watershed. It is interesting to observe a stream over time to see how streamflows respond to various rates of rainfall and how salmon respond to various rates of flow.
For Kitsap County residents, we have produced an interactive map on the Kitsap Sun Web site that shows where one may look for salmon. Not all the locations have salmon at the same time, but it may be worth a look.