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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Feb 04

Coho tail off, steelhead step up, and otters pig out

Posted on February 4, 2016 at 10:11 AM by Emma Detwiler

by Aquatic Ecologist Eric Ettlinger

The last three weeks have been very, very wet, and opportunities to get in local creeks have been rare. Over nine inches of rain has fallen since mid-January, raising Lagunitas Creek to a flow of 1,240 cubic feet per second on January 19 and filling Kent Lake to overflowing on January 22. The few surveys conducted in tributary streams found quite a few carcasses but only two new coho redds. Some coho may have continued to spawn (unseen) in the main stem of Lagunitas Creek, but it looks like the run was essentially over by mid-January. The preliminary season total stands at 271 coho redds – a nine percent increase from three years ago, and as reported previously, the highest count in nine years.

Steelhead spawning has been ramping up slowly, mostly in San Geronimo Creek, where we saw 13 new redds last week. MMWD surveys have documented 45 steelhead redds to date. Spawning typically peaks in mid-February, but early counts indicate a larger-than-average steelhead run. By next week flows in Lagunitas Creek will be low enough to resume surveys and we hope to finally see the redds that steelhead, and possibly coho, have built in recent weeks.

Lastly, a recent encounter with a family of river otters prompts me to address a question I get a lot: “Are otters a problem for salmon?” Otters do indeed seem to eat a lot of salmon. Many of the salmon carcasses we find show signs of otter predation, namely a bite to the head or throat, and we usually don’t see the carcasses that were dragged into the bushes. On the other hand, otters are native predators that subsist for most of the year on non-native crayfish. Our small otter population would have a negligible impact on a healthy salmon run. Otters may not be helping our efforts to bring back the salmon, but bringing back the salmon would surely benefit otters, other predators, and the ecosystem of which they are all members.

Check out this video of a family of four river otters taking a break from chasing salmon in San Geronimo Creek. At about eight seconds in the photographer accidentally makes a noise and the otters hide, poorly, behind a tree.

 Otter periscope - sm
 A river otter in San Geronimo Creek.


Megan Isadore
February 4, 2016 at 12:27 PM
Yes, river otters are thriving in Bay Area watersheds, a good sign of reasonably good watershed health. They certainly do eat salmon if they can get them opportunistically, but their main foods year round are slow-moving, plentiful fish like carp, large mouthed bass, crayfish, crabs, snails and mussels, frogs, and even waterbirds. Please participate in River Otter Ecology Project's Citizen Science effort and report your otter sightings at Click on the Otter Spotter icon, and don't forget to check out our online map of river otter sightings! Megan Isadore, River Otter Ecology Project and on Facebook!
Anonymous User
April 17, 2017 at 7:11 PM
Otter spotted in Lagoon 1 Corte Madera 6:30 PM 4/17/17.

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