Through SYRCL’s participation in the River Management Team (RMT), we get monthly updates on the number of Chinook and steelhead utilizing the fish ladders at Daguerre Point Dam. This year’s numbers, unfortunately, are significantly down from the recent past.
The RMT is a group of agency and non-profit representatives that work together to better understand and promote research on the Lower Yuba River. Members of the RMT include Yuba Water Agency, US Fish and Wildlife Service, State Water Resources Control Board, Dept of Water Resources, Pacific States Marine Fisheries Commission, CA Dept Fish and Wildlife, National Marine Fisheries Service, HDR (an engineering firm), and the US Army Corps of Engineers. The RMT helps fund restoration, research, and make science-informed decisions for the Lower Yuba River.
The RMT funds Pacific States Marine Fisheries Commission to provide the fish count updates. They do so through the use of VAKI River Watcher camera systems. These cameras are located in the fish ladders at Daguerre Point Dam and they take a picture of each fish (or otter) that swims past them. Specialized software then identifies what species the fish is. This process gives us a count, reported monthly during the RMT meeting, of the number and species of fish traveling up the Yuba.
So far this year, adult salmon returns are the lowest they’ve been in many years, about 65% of what they have been the last two years.
The “salmon year” hits its peak (the peak being numbers of adults and spawning activity) around the end of the calendar year, so we are likely to see more fish moving up the Lower Yuba River as water cools; however, we are unlikely to see these numbers increase significantly.
It’s impossible to attribute these low adult salmon returns to any single variable, as river conditions are only a small part of what the salmon have to overcome to get here. Some of the variables include:
- If the year that a salmon was born was a wet year, then there was lots of floodplain habitat for it to rear on, meaning it likely grew to be larger by the time it left freshwater. In addition, in wetter years the rivers stayed colder longer into the summer, so juveniles were less thermally stressed and more likely to survive the journey out into the ocean.
- Before juvenile salmon can reach the ocean, they must make it through the delta – a gauntlet of predators, water diversions, and poor water quality.
- Once in the ocean, salmon will spend roughly 2-5 years growing and can travel as far north as Alaska searching for food. Ocean conditions during this time period play an important role in how many salmon survive. As the ocean warms and acidifies, the primary marine food sources for salmon get harder to find and salmon eat less healthy food.
- On their way back to their ancestral river to spawn, salmon again must traverse the Bay, Delta, and swim upriver, contending with the same threats they faced as a juvenile. Warm water temperatures and low dissolved oxygen can all make it harder for salmon to return up the Yuba.
The majority of the adult salmon we are seeing return in this “fish year” were born in 2018. If you remember 2018, it was a major drought year – in the driest 30% of water years. This likely resulted in fewer juveniles surviving the rearing period in the Lower Yuba River as well as their journey to the Delta. The next few years in the ocean were variable.
As these adults began their journey back to the Yuba, they encountered very low dissolved oxygen in the Delta, further straining their ability to make it back to spawn. Conditions in the Delta this summer were such that a red tide formed, leading to a pretty major fish kill event.
Between the devastation caused by the mining practices of the past to the dramatic weather conditions as a result of climate change, optimal rearing habitat for juvenile Chinook is not readily available in the Lower Yuba River. In addition, we
- Can‘t control how much rain and snow falls
- Can‘t control ocean or river temperatures
What we CAN do is make sure that there’s plenty of high-quality rearing habitat available in the Lower Yuba in order to give the salmon a better chance at survival. Restoration projects like the ones SYRCL has completed at Hallwood and Long Bar do that. Still, we won’t be able to know how effective our restoration efforts are for AT LEAST four years, and that’s assuming all of the other things that are outside our control are ideal. We are confident, though, that our restoration efforts will be giving Yuba Salmon the best fighting chance we can.
You can help SYRCL continue this work by becoming a member today. Throughout the month of December, a generous donor will match your gift, doubling your impact to help SYRCL in its efforts to help Yuba Salmon Now.
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