Historically, the entire Central Valley of California was a floodplain. In winter and spring, storm runoff and snowmelt would spill over riverbanks, creating vast biologically productive wetlands where aquatic life flourished. This incredible productivity supported a huge fishery in the Central Valley, where we once had one of the largest runs of Chinook in the world. However, as modern day California was developed, the Central Valley’s waterways were re-engineered and channelized to control the floods and divert water for human uses. Today, only 5% of Central Valley floodplains remain intact and three of the four native Chinook salmon runs are listed as threatened or endangered. In essence, levees are starving salmon and smelt populations.
To address these issues, CalTrout envisioned of a new way forward, designing a strategy to help Central Valley Chinook by reconnecting salmon populations with the floodplains. Central Valley Chinook salmon are specially adapted to rear on floodplains. As shown below, after just a few weeks, the fish that we raised on floodplains are twice as large as the same fish that spent that time in the river.
Floodplain habitat restoration for salmon in California’s Sacramento Valley falls into two strategies: providing access for fish to the foraging and rearing habitat on inundated floodplains (wet-side) and exporting the productivity of inundated floodplains to the river (dry-side). For the last decade, CalTrout’s wet-side programs have been working in the Yolo and Sutter Bypasses, which still flood occasionally and are accessible to fish. The new dry-side programs are conservation strategies that include all the flooded acreage existing outside the levee boundaries that still active floodplains but that fish don’t have access to.
Jacob further explains, “On the wet side, we’re bringing fish onto floodplains, and we’re doing that with the Nigiri project. On the dry side, we’re bringing floodplains back to the fish. We call that fish food.”
The photo below shows that invertebrate and zooplankton biomass produced on a floodplain is orders of magnitude more dense than that in a river-type ecosystem. That’s the food we’re delivering to the fish.
These projects were recently featured in Maven’s Notebook, a popular website dedicated to sharing news on California water. To read more in detail the work CalTrout and our Central Valley team is doing to proactively manage Central Valley native fish, click button below.