How Will the Salmon Survive? Fisheries in a Warming California | KCET
How Will the Salmon Survive? Fisheries in a Warming California
Earlier in May, scientists released a report warning that as many as three fourths of California’s 31 types of native salmon and trout might go extinct within 100 years. The ominous forecast made headlines nationwide as reporters and editors highlighted the main takeaways – that climate change and a variety of human activities, including agriculture and development, would make most of California’s rivers and lakes where salmon and trout live uninhabitable for the fish, most of which need cold, clean water.
But there is a bright side to the report that isn’t being widely discussed. Even as California’s human population surges toward 50 million by 2050 and the climate grows hotter and drier, it might still be possible for people to share the landscape with salmon and trout. Things are looking good, in fact, for several species – including coastal rainbow trout and a few populations of both coho and Chinook salmon, the latter of which is the backbone of a major fishing industry.
“The good news is that we know a whole lot about these fish and what they need to survive,” says Peter Moyle, a biologist with UC Davis’s Center for Watershed Sciences and a coauthor of the analysis, titled State of the Salmonids II: Fish in Hot Water. The report is an update to a similar document published in 2008.
Moyle says there are places where California’s iconic native fishes could persist far into the future, and there are fisheries advocates around the state aggressively trying to protect and preserve them. Dams are coming down along the Klamath River, and vast floodplains that provide food and refuge for baby salmon and steelhead are being restored in the Central Valley. So are mountain meadows that hold cool water all summer and feed it slowly into icy trout streams. Similarly, conservation efforts are being focused on creeks and rivers fed by cold year-round springs – a unique type of habitat that will be vital for fish in a warmer future, and which could end up as their last wild holdouts.
Under current conditions, 23 species, subspecies and strains of California’s native salmon and trout are likely to go extinct sometime in the next 50 to 100 years. Central Coast coho, southern steelhead trout, the Kern River rainbow trout and the McCloud River redband trout – a rainbow trout subspecies – are on this list. So are the Sacramento River’s winter-run and spring-run Chinook salmon, according to a rating system developed by Moyle and his coauthors, UC Davis colleague Robert Lusardi and California Trout's conservation program coordinator Patrick J. Samuel.
The authors deemed other fishes less threatened. Coastal rainbow trout, for example, have been introduced into just about every suitable waterway in the state. Exceptionally tolerant of high water temperatures and poor water quality, they will probably thrive in the murky, tepid waters of California’s future, the report says. Northern California winter steelhead trout and fall-run Chinook are also looking at relatively bright futures, as long as populations continue to be supplemented by hatcheries (though these facilities, which produce genetically inferior fish that sometimes breed with wild fish, cause problems of their own, scientists say).
But maintaining populations of some of these fishes will take plenty of work, and Moyle, Lusardi and Samuel propose strategically aiming any and all conservation efforts at the habitat types that matter the most.
“We must protect the best of what habitats are left,” they write in their 106-page document, released on May 16. “Few fully functioning river ecosystems, with relatively intact watersheds and high-quality habitat, exist today in California…”
Most have been drained dry by agricultural irrigation, trampled by cattle, denuded by sloppy logging and mining operations, and made inaccessible for fish by dams. Booming North Coast production of marijuana, a water-intensive crop, is not helping, and streams that support endangered coho salmon and steelhead runs are often sucked dry in the summer by growing operations or reduced to bathtub warm trickles. These are intolerable conditions for most salmonids that will certainly worsen as less snow accumulates each winter and spring in the mountains.
More on climate change
The report explains how rivers now fed by melting snow will see increasingly variable flows in the future. Snow may melt more rapidly in the spring causing icy deluges downstream, but leaving the rivers abruptly dry, or nearly so, by summer. From this perspective, rivers which are fed by cool year-round springs – not just seasonal snowmelt – are significantly different and will be the key to preserving California’s salmon, Moyle says. That’s because these streams are more likely to continue to provide cool water that flows all year, allowing conservation efforts to be focused on secondary issues, like preserving gravel beds where fish lay their eggs, protecting banks from collapsing under the pressure of grazing livestock and guarding against excessive water diversions.
The Shasta River, a Klamath tributary, is one such river. A host stream for coho and Chinook, it begins on the northern flank of Mount Shasta at a spring of icy water that gurgles from the earth.
“If you look at it, it’s not a very big stream,” Moyle says. However, it provides wonderful habitat and, as one salmon river in a whole watershed, is disproportionately important to the Klamath fishery. Because its headwaters flow over volcanic rock, nutrients dissolve into the water and support abundant insect life, which juvenile salmon eat, Moyle says.
Coauthor Lusardi says at least 80,000 Chinook are believed to have once spawned in the Shasta River each year – several times more fish than spawned in the entire Klamath basin in 2016.
“In 2015, 6,745 individuals were counted [in the Shasta River],” Lusardi writes in an email exchange. “The preliminary returns in 2016 were much lower.”
The river, which has been seriously damaged by cattle grazing, currently hosts a pitiful run of a few dozen adult coho every season. Lusardi says UC Davis’s Center for Watershed Sciences, California Trout and The Nature Conservancy are collaborating on restoration measures to protect the waters in the Shasta River, which could potentially one day again be an important salmon river.
Other cold springs feed the Klamath system, too. Moyle says historical records indicate there are a number of these water sources in the middle reaches of the Klamath River, in parts of the watershed now submerged under reservoirs. However, formal plans are already advancing to remove the Klamath’s dams specifically to benefit fish.
“Remove the Iron Gate and the Copco dams and you almost immediately unveil some big spring systems which could be available for coho salmon,” Moyle says.
Dam removal will also open up several hundred miles of upstream habitat where Klamath salmon once spawned but which migrating fish have been unable to access for decades. This makes the Klamath, which begins in southern Oregon, a potential lifeline for future salmon and steelhead runs that, as long as conservation efforts are carried through, could support large populations of Chinook, coho and steelhead.
On the Sacramento River and its tributaries, dams that block migrating Chinook salmon were built almost 80 years ago and will probably always be integral parts of the state’s water supply system.
“Shasta Dam and Oroville Dam are obviously not going to go anywhere,” Moyle says.
In fact, while dam removal on the Klamath is expected to reboot some salmon and steelhead runs, on the Sacramento River, fish and dams share a more complex relationship. The reservoir behind Shasta Dam is hundreds of feet deep at the base of the dam. The water in the lake is thus usually very cold. When released into the river below, this water provides the conditions that salmon need to spawn.
“Ironically, these deep reservoirs with cold water at the bottom really act like spring systems,” Moyle says.
Overall, the dam has been a negative influence on salmonid populations. Shasta Dam makes it impossible for Chinook to spawn in several mountain tributaries to the Sacramento. One of those rivers is the McCloud. Fed by springs, it runs cold all year and historically provided important summertime habitat for huge numbers of migrating salmon. The federal agencies that struggle to balance the water needs of both people and fish are even considering reintroducing endangered winter-run Chinook to the McCloud. The program would require mechanical life support in perpetuity, since adult fish would depend on vehicle transport to get around the dam on their way upstream. Likewise, juveniles would need a lift back downstream of the barrier. Moyle calls this proposed McCloud project a “desperation measure” and points out that capturing the baby salmon born in the river would be extremely difficult.
Moyle and his coauthors consider several tributaries that enter the Sacramento River downstream of Shasta Dam, and which are fed by springs and kept cool all year, to be of much more importance as possible salmon streams of the future.
Battle Creek, for instance, which enters the bigger river near Red Bluff, receives much of its water from cold springs flowing from the flanks of the Lassen massif. Moyle says Battle Creek will remain a key spawning site for the steelhead and Chinook salmon – including fall-run and spring-run, and possibly winter-run – that may persist in California’s future.
State of the Salmonids II names the Smith River, the Eel River, a Klamath tributary called Blue Creek, and Butte Creek, which feeds the Sacramento, as other important steelhead and salmon streams. The authors consider preserving “systems like these in perpetuity the highest priority” for protecting the diversity and natural abundance of salmonid populations.
The Scott River is another tributary to the Klamath considered a high-value conservation target.
“There is tremendous potential here for protecting coho,” Moyle says.
Sadly, it is almost a sure bet that, no matter what, about a dozen of the fishes discussed in the report will vanish from California – including chum and pink salmon, which are abundant in the Pacific Northwest. Others have comparatively bright futures in California, which marks the southern limit of salmonids’ geographic range in the Pacific. Because Chinook salmon are so valued as a food fish, it’s probable that hatcheries will almost always produce them in California and maintain some populations, even if natural ecosystems fail to support them indefinitely.
But of all the salmonids that the authors studied, none have such high prospects for thriving in the golden state as the coastal rainbow trout.
“It’s been introduced all over the place,” Moyle notes.
Other strains of rainbow trout – not technically different species but discussed as such in the report for the sake of simplicity, Moyle says – might vanish. The Kern River rainbow trout is probably doomed. In fact, one of the biggest threats is its close cousin, the coastal rainbow, which threatens to interbreed and genetically absorb the Kern River rainbow. Grazing of livestock on the banks of streams in the Kern watershed has also degraded much habitat.
Forest fires, which destroy shade-creating vegetation and can lead to devastating landslides and erosion into streams, are named as major threats to the survival of Little Kern golden trout, the McCloud redband and the Lahontan cutthroat, an enormous salmon-sized fish that historically lived in the Tahoe basin and much of the eastern Sierra Nevada. Forest fires will probably increase in intensity and frequency as the planet warms and forests become more arid.
Unique trout populations could benefit from the restoration of mountain meadows, Moyle and his coauthors concluded. So could a few salmon runs and the mountain whitefish, a small trout cousin more common in the Rocky Mountains and Canada. Since meadows can soak up water and hold it in boggy soils for months as it trickles out into gullies and stream headwaters, they can effectively replace some degree of the services currently provided by mountain snowpack.
Water accumulates in meadows because they are areas where the land almost entirely flattens out. The soggy soil that results inhibits the growth of trees.
“The whole idea with meadows is that they store a lot of water, and the better condition the meadows are in, and the less compacted the soils [by grazing cattle], the longer water hangs out in the meadow system and provides flows for streams,” Moyle explains.
More on salmon
Certain salmon streams that enter the Sacramento, like Mill Creek and Deer Creek – each important for spring-run Chinook – receive cold water for much of the summer from boggy mountain meadows. Mostly, though, meadow systems support what are chiefly trout rivers. Many of the streams that enter northeastern California’s Eagle Lake, for instance, were historically fed by meadows. Eagle Lake is home to a namesake strain of rainbow, famed as a game fish but highly threatened by competition with introduced eastern brook trout and by cattle grazing, which has destroyed the meadows alongside spawning creeks.
With the major threats identified for this unique trout, as well as for most other imperiled salmon and trout populations, there seems to be a genuine opportunity to preserve the state’s native fishes.
“I’d like to be optimistic and think that we can save them all,” Moyle says.
In the past few years, he notes, a promising thing has been happening on Putah Creek, a lower tributary of the Sacramento that enters the river after passing through Davis: Hundreds of Chinook salmon – and as many as about 1,500 – have been entering the system each fall to spawn, something that hasn’t happened for many years.
“It’s an example of a real opportunity to have a self-sustaining run of Chinook,” Moyle says.
In the worst-case scenario, California’s native salmonids will be represented by just coastal rainbows and some meager runs of Chinook and steelhead kept alive by fish hatcheries, Moyle says.
“These would be the types of salmon runs that are like tourist attractions, and people who come and see them will say, ‘Can you believe we once had a million of these fish?’”
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