.Clouded by Coho

Last winter’s coho run spawns hope

By Cole Hershey

The rains of 2021 were a soothing balm to the drying lands of California, filling reservoirs to the edges of dams across Marin and Sonoma counties.

During and proceeding these heavy downpours, many in the media noted the season as a miracle for the coho salmon that live in Lagunitas Creek in Marin County, stretching their spawning across the watershed into areas they have not been seen in over a decade. The rains of late 2021 helped the Lagunitas coho, as in [1] the most plentiful streams in all of California lay nearly 400 nests (called redds), according to preliminary data acquired by the Bohemian.

While this preliminary number is nearly double the coho redds found last year, when looking at seasons historically, the number may have less to do with the rains than many observed.

Coho spend parts of their lives in freshwater and parts of their lives in the ocean. They live in freshwaters for a year and a half before they venture out to the ocean, only returning to breed in their third year of life, after which they pass away. For coho conservationists, the important information to observe is the parent generations and their offspring generations, meaning the salmon spawning season three years prior.

As it currently stands, the coho redd count is higher than the previous generation. The data is still being collected by the National Park Service, Marin Municipal Watershed District, and the Salmon Protection and Watershed Network (SPAWN).

“The generation following has always been greater than the one that preceded it,” said Preston Brown, director of watershed conservation at SPAWN.

“Those rains in December which drew headlines said, ‘Yeah coho! Coho everywhere!’” remarked Brown. “But when you look at it, the number of coho was just a little above average, at least in Lagunitas.”

In the Russian River Watershed of Sonoma County, where coho are known to make redds, the appearance of a large swelling of coho also occurred. The large number of coho observed in this watershed [2] was due to the heavy rains shortening their spawning season, which gave off the appearance of more coho in the stream, according to a recent Sonoma Water report.

Due to the heavy rains before their spawning season began, coho swam further upstream than usual, reaching higher into small tributaries. Since they spread out across the watershed further than usual, it gave the appearance that the run was more bountiful than other years.

“They were in amazingly high places, so it painted this picture that could be sort of misconstrued,” said Brown.

This occurred in Sonoma as well for the threatened Chinook salmon. However, exact numbers are hard to discern, seeing as Chinook are listed as threatened, unlike steelhead and coho, so monitoring their numbers across California has not been prioritized.

“Because the rains were so perfect—they came right at the right time at the right amount of duration—it made these little tributaries full of water,” said Brown. “Coho were getting up into those waters where they hadn’t been seen in maybe 10 years or so.”

As the winter season continued, however, there was very little rain to show, quickly drying Lagunitas creek, which has very little groundwater to maintain its flow throughout the summer. By the beginning of spring in some tributaries further upstream, the pools of water were beginning to lower into trickles.

“We got these coho spawning in these tiny tiny tributaries, and once those eggs hatch and the fish are swimming around, those tributaries [could] start to go dry,” said Brown.

Luckily, the April rains greatly aided the coho living further upstream.

The fact that the coho spawned so far upstream, according to Eric Ettlinger, aquatic ecologist for the Marin Municipal Water District, is the important takeaway from this year’s run of endangered coho. 

“Even if we hadn’t gotten those spring rains, I think salmon spawned in enough places that we would’ve gotten a good juvenile population this year, regardless,” Ettlinger said.

This, Ettlinger explained, is because there was a wider variety of habitats and locations where the salmon could thrive.

“There’s this idea of a portfolio where you want as much diversity as possible in order to maximize your returns,” Ettlinger said. “You want them to have as many options as possible, and this winter we saw that.”

While this year has been a positive moment for coho, steelhead and Chinook alike, California is heading yet again into an exceptionally hot and dry summer, with nearly all of the state in a severe drought.

According to a 2019 report by the National Oceanic and Atmospheric Association, most coho in California are at a very high risk from[3]  climate change, due to a greater sensitivity to ocean acidification, along with water temperatures and other stressors.

“This population here is particularly vulnerable to climate change,” said Ettlinger. “[This] is the southernmost wild coho population in the world, and climate change is going to have the biggest impact on populations [of all species] closer to the equator.”

Due to large-scale fishing, along with habitat loss mainly from large-scale dam building across California, coho have been greatly reduced from their historical numbers, when the streams all across Northern California used to run red with coho. Since their listing as endangered in 1996, coho populations in California have steadily been on the incline.

While there is little to be done to reduce the temperature of ocean water, other than eliminating the use of fossil fuels, there are things to be done to help coho survive in a less hospitable climate.

Marin Water for decades has been adding logs and other plants into streams themselves, something that has been proven to help juvenile coho survive through the summer.

According to Ettlinger, while dams across the county have created many setbacks for the salmon, the release of water from the reservoirs may give coho in Lagunitas a better chance in the future.

“Ironically, the cold water that’s released from our reservoir, Kent Lake, year round may be one of the reasons that this population will persist when other populations in the region are not going to,” Ettlinger said. “So that acts as a buffer against the rise in temperatures that are expected with climate change.”

SPAWN, for one, helps with countless restoration activities across the watershed, such as running a native plant nursery and reestablishing historical floodplains. This June, SPAWN made an agreement with Marin County to implement a new stream conservation ordinance to help protect stream banks and floodplains from building.

However, the work of protecting coho salmon in the North Bay is not relegated just to the small watershed of Lagunitas Creek.

In 2021, a study was conducted in Dry Creek, a small tributary of the Russian River, in order to understand why many smolts, young coho traveling to the ocean, do not make it to the Pacific. While this was the first year of the study using hatchery-caught coho to study the effects of predators on the young fish, it is data Sonoma Water could use in order to inform how they proceed with ongoing restoration projects aimed at saving coho.

One potential tool, which now could be used to help mitigate the effects of drought and climate change on coho in streams, is beavers.

“A group of us are working to reintroduce beavers into Lagunitas Creek,” said Ettlinger. “It would be really beneficial to coho in particular because coho like slow water, they like wood in the channel and beavers can create a really ideal nursery habitat. So that would be a big change.”

In May of this year, the state of California approved five new staff members to lead a beaver restoration assessment program across the state, signaling a shift in how the government may feel about the animals, seeing as the rodent has a great many benefits to the land beyond coho restoration.

It should be noted that beaver relocation is currently illegal under state law, California being one of the few states west of the Rocky mountain range to do so.

With the work of countless individuals across Sonoma and Marin counties, coho are steadily increasing in number, and there is still plenty of reason to hold out hope. According to Brown, coho, a keystone species like the beaver, are critical for the preservation of coastal ecosystems and local economies. Even in Sonoma County, the fish were once so plentiful that there was a cannery in the southern region of the Russian River Watershed.

While coho are still far from those booming numbers, with the tireless work from Marin Municipal Water District, SPAWN and Coho Partnerships in Sonoma County, coho are slowly but surely on the rise.


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