by Eric Ettlinger
This has been another very good week for Lagunitas Creek coho salmon (and for the biologists who count them). We spent the last four days surveying all of the spawning reaches of Lagunitas Creek, plus the tributaries San Geronimo Creek and Devil’s Gulch, and found signs of spawning activity in every stream reach we surveyed. We saw 15 live coho and 23 new redds, which brings the season total to 26 salmon and 26 redds. We haven’t seen this many redds in November in ten years. It’s been the kind of week that makes handling a spawned-out, smelly salmon carcass a joyous experience (see photo).
Speaking of salmon carcasses, it may look like we handle them just for fun and photo opportunities, but we’re actually collecting important data on every carcass we find. We collect genetic material that tells us how Lagunitas Creek coho relate to other coho in the region (they’re pretty unique!). We also collect tiny bones called otoliths from within the salmon’s head that provide a record of the fish’s entire life. These two millimeter long bones tell us when the fish hatched, how old it was when it migrated to the ocean, how long it spent in the ocean, and how fast it grew at each stage of its life. It’s like a flight data recorder. A study being conducted at UC Berkeley is using the otoliths we collect to investigate where in the watershed these salmon hatched, which may indicate survival differences for fish growing up in different parts of the watershed. Understanding which fish have higher survival rates (and why) could indicate what habitat characteristics improve survival and even how habitat should be enhanced. So it turns out that these dead, smelly fish can tell us a lot about how to save them.