Written by: Aquatic Ecologist Eric Ettlinger
February was a very wet month for Marin County, and opportunities to conduct spawner surveys have been limited. On only three occasions were stream flows low enough to conduct surveys in tributary streams, and we didn’t get into Lagunitas Creek at all. During these few surveys we saw 33 steelhead redds, bringing the season total up to 99, which is about average for the end of February. We’re now past the typical peak in steelhead spawning but hopefully we’ll get back into the creek in March.
Last week’s atmospheric river dumped between eight and ten inches of rain on various locations in the Lagunitas Creek watershed. Stream flows peaked at 4,100 cubic feet per second (cfs), which is the kind of flood that recurs, on average, every eight years or so. Past floods like this have mobilized streambed sediment, either uncovering or entombing incubating salmonid eggs, and resulted in survival rates of only about two percent. Looking on the bright side, over 600,000 coho eggs were laid during this year’s large coho run, and survival rates don’t have to be very high to produce typical numbers of fry. The biggest risk now is that a late-season storm will wash out coho fry after they’ve emerged from the gravel. Fingers crossed.
| Lagunitas Creek at about 4,000 CFS on February 26, 2019.