by Eric Ettlinger
Coho salmon appear to have completed their spawning run for the 2011-12 season. Only two live fish (both males) were observed last week. MMWD biologists will be conducting spawner surveys again this week in sections of creek that haven’t been surveyed recently, so a few more coho redds may still be found. For now our season totals stand at 130 coho redds and 340 live coho. Most spawning occurred in the main stem of Lagunitas Creek, but 23 redds were seen in San Geronimo Creek and 11 were seen in another tributary, Devil’s Gulch. National Park Service biologists reported seeing coho spawning in another Lagunitas tributary, Cheda Creek, for the first time in four years. Three redds were also seen in small tributaries to San Geronimo Creek. This year’s coho run was smaller than average, but five times larger than the parent generation of three years ago. This is a very hopeful sign that Central California Coast coho are making a comeback after three years of abysmal spawning runs.
Steelhead are also spawning in larger numbers than have been seen in recent years. Steelhead spawning generally peaks in February and continues into April, and to date we’ve counted 60 steelhead redds and 93 live steelhead. Half of the steelhead redds have been seen in San Geronimo Creek. As with coho, this year’s steelhead are unusually large (see photo), which is an indication that they found plenty of food in the ocean.
Even without the final tallies, it’s not too early to start speculating about why coho and steelhead numbers are up. Of the 2,100 or so coho smolts (adolescent fish) that migrated to the ocean in 2010, approximately 12 percent returned. The rate of coho marine survival in the previous four years ranged between two and five percent. Improving ocean productivity is likely the primary factor that allowed salmon to grow larger and survive at a higher rate. Another potential factor contributing to the coho comeback is the Giacomini Wetlands restoration. In 2008 the National Park Service restored over 500 acres of tidal marsh at the mouth of Lagunitas Creek, providing additional rearing habitat for young salmonids on their way to the ocean. This season’s coho were only the second cohort to have access to this new habitat. Coho numbers from other California streams will hopefully be reported soon, and we should then be able to tease apart which factors improved regionally and which improvements were specific to Lagunitas Creek.