by Eric Ettlinger, Aquatic Ecologist
The current state of affairs in Lagunitas Creek can be described as a glass-half-full/glass-half-empty situation. Or more accurately, a reservoir-full, streambed-empty situation. By the end of December the coho salmon run was on track to be larger than the parent generation of three years ago and continue the generational improvements we’ve seen for each of the last five years. But then came the unrelenting storms of the last two weeks. On the positive side those storms filled MMWD’s reservoirs and produced the high flows that can create and improve salmon habitats in Lagunitas Creek. On the negative side those flows destroyed many coho redds, washed away some of our salmon habitat structures, and severely hampered our survey work. We’ve heard rumors of fresh coho out there (and steelhead should be starting to spawn too), but we haven’t been able to see them ourselves.
|The stream gauge in Samuel P. Taylor State Park at 2,500 cubic feet per second
The most recent storm raised Lagunitas Creek flows to 4,300 cubic feet per second, which was the third-highest flow in 35 years. In the coming months we’ll see if this flood had significant impacts on incubating salmon eggs and/or last year’s fry. Previous major floods in 1998 and 2006 resulted in very poor egg survival, and we expect to see relatively few fry again this summer. One-year-old juvenile coho have survived recent large floods successfully, likely by seeking out slow water areas on floodplains. Ironically, it may be moderate storm events that are most deadly, because flows stay confined in the stream channel and slow water habitats may be hard to find. This summer we’ll be enhancing a number of areas on Lagunitas Creek to provide exactly those kinds of slow water habitats. On an optimistic note, the floods this season have risen and receded rapidly, hopefully subjecting coho fry to fast, confined flows only briefly. In late March we’ll start counting the surviving smolts as they migrate to the ocean and, one way or the other, that data will contribute to our understanding of how salmon survive floods and what we can do to help.