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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 24

Lagunitas Coho – The Year in Review

Posted on February 24, 2015 at 2:03 PM by Ann Vallee

by Eric Ettlinger, Aquatic Ecologist

The final update on Lagunitas Creek coho for the 2014-15 season is somewhat overdue because of some unusually late spawners. Last week we observed eight fresh coho in Lagunitas Creek, which is exceptionally late for a run that peaked in mid-December. Coho are typically seen spawning in February only when the rainy season is delayed, like last year. Given this year’s early rains the best explanation I have for the extended run is that the parents of these fish may have been late spawners. Back in 2012 the last coho of the season were seen spawning on Valentine’s Day.

So, moving on to the postmortem … The best that can be said about this run is that it wasn’t smaller than the coho run three years ago, which is something. Our preliminary season total is 131 coho redds, or about 65% of average. This does not include spawning in Olema Creek or the tributaries to San Geronimo Creek, which are surveyed by the National Park Service and the Salmon Protection and Watershed Network (SPAWN), respectively. The marine survival rate of these fish was under 4%, which is well below the average of the last eight years.

The picture was brighter for other species. We counted the highest number of Chinook salmon redds (23) in eight years and the highest number of chum salmon (3) in a decade. The steelhead run got off to a late start due to the exceptionally dry January, but is now in full swing. To date we’ve seen 70 steelhead redds, which is approaching average for late February.

 lamprey pair -sm (2)
 Pacific lamprey pair
Finally, we saw the first Pacific lamprey of the season on January 29. We typically see these native, cartilaginous fishes spawning in March, as we’re wrapping up our salmonid spawner surveys. Our AmeriCorps members took this great picture of a pair using their sucker mouths to pull rocks from their redd. Their eggs will hatch into worm-like ammocoetes that will spend as much as seven years filter feeding in the streambed. Then they will migrate to the ocean and find a larger fish to latch on to and parasitize. They aren’t able to navigate back to their natal stream like the salmonids do, but when they’re large enough they’ll let go of their host and follow the scent of juvenile lamprey pheromones to whatever stream they’re close to. Like the salmon, this is a one-way trip and they die after spawning. Lamprey will continue to spawn in Lagunitas Creek through the spring.

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