Bold California experiment may bring Chinook salmon back to their old habitat. 06/24/2020
Young Chinook salmon, more commonly known as King salmon, once grew up in the verdant floodplains of California’s Central Valley, which stretches for 450 miles through the state’s interior. Here in the nutrient-rich shallows, salmon grew strong enough to make their way through rivers and streams to the San Francisco Bay and out into the open ocean.
Today, this valley is covered by farmland and walled off by a byzantine system of dams, dikes and canals — the salmon are shut out. But a new project pairing rice farmers with salmon conservationists might be changing that.
The California Rice Commission’s salmon pilot project is an ambitious undertaking borne of a key insight: Flooded rice fields look much like the floodplains where salmon once matured. Rice farmers typically flood their fields in winter to help leftover plant matter decompose. So why not let the salmon grow up there, too?
Similar tests have examined the concept over more than a decade, with promising results. This particular project is led by scientists from the University of California, Davis, and hosted at River Garden Farms, just north of Sacramento. Its aim is to find standardized practices for applying the techniques on a wide scale, and it’s supported by $1.4 million in funding from the USDA’s Natural Resources Conservation Service, agrochemical company Syngenta, and other agricultural industry companies. Scientists involved with the project hope to see whether flooded rice fields could be a viable replacement for lost salmon territory. If successful, the program could lay the groundwork for a mutually beneficial collaboration between wildlife managers and farmers.
Wild Salmon in the Rice Fields
Salmon once thrived off the California coast, a source of bountiful food for indigenous fishermen. But today, some populations in the state are threatened, in part because their habitat in the Central Valley has disappeared (Read more: California Salmon Crisis Closes West Coast Fishery). Giving them back their land could cause Chinook numbers to grow once again and resurrect this source of healthy, sustainable seafood.
A salmon’s size when it reaches the ocean is a major factor in determining whether it will survive – it must be large enough to fend for itself (Katz JVE 2017). And a big component of that development is having enough to eat. Salmon maturing in their ancestral territory in the Central Valley had access to more than enough food, courtesy of seasonally inundated floodplains that were warm and shallow. This encouraged the growth of algae and the invertebrates that feed on it. These in turn fed the young salmon.
But today, less than five percent of those floodplains remain (Katz JVE 2017). While Chinook salmon populations in Alaska are considered healthy, California Coastal Chinook are listed as threatened (read more: Trolling for Top-Quality Alaskan King). That’s because young salmon in California have lost the land that supported a key stage in their life-cycle. Without their adolescent feeding grounds, the salmon may not grow big enough to survive in the ocean and eventually return to spawn. And supporting these growing salmon could play a big role in ensuring the health of their populations long-term.
Now the rice project is attempting to mimic those long-lost, natural conditions. In eight test plots in a flooded rice field, the scientists are watching 9,000 Chinook salmon mature. Some of the salmon were tagged with implanted trackers to see if they made it down the Sacramento River and under the Golden Gate Bridge to the Pacific Ocean. Finally, these “wild” fish will be compared with hatchery-raised fish to see if they fare better.
While the data has yet to be fully collected and analyzed, a 2017 study hinted that fish reared in the rice fields grew as big as fish raised in a natural floodplain environment (Katz JVE 2017). And early results from similar rice field salmon farming operations indicate the idea could be successful. Salmon raised at a site called Knaggs Ranch, for example, grow bigger than their counterparts raised as controls.
What about pesticides applied to rice fields? Researchers say those chemicals are applied months earlier, and break down relatively quickly in that environment, long before the fish take up their winter residence (Rice fields could be the savior for California's imperiled Chinook salmon, 2020).
Healthier Wild Salmon a Win For All
If the California Rice Commission’s salmon pilot project does turn out to yield bigger, stronger salmon, it could lead to more widespread adoption of these techniques. Rice farming in California currently covers about 550,000 acres, according to the University of California Division of Agriculture and Natural Resources. That land, already flooded by farmers in the winter, could be put to use helping wild salmon develop. And other measures, like removing dams that prevent salmon from returning upstream to spawn are helping as well.
Allowing salmon to return to the valley in a way that integrates seamlessly into existing agricultural operations is a win for everyone — including you.
That’s because putting wild salmon on your plate is healthier and more environmentally friendly than farmed salmon. Farmed fish are fed diets often heavy in vegetable oils instead of natural fish feed, shifting the balance of their crucial omega-3 fatty acids toward less-healthy omega-6s (Fry JP 2016). And farmed salmon are often infected with sea lice, infestations that can jump to wild populations and harm their health (Hemmingsen W 2020).
Chinook, or King salmon, are considered to be the richest and most flavorful of all wild salmon. That’s partly because of their bountiful fat reserves, which pack in flavor and omega-3 fatty acids. Chinook salmon are also full of Vitamin D and the antioxidant astaxanthin.
Sustainable fishing techniques can ensure that wild populations both remain healthy and continue to provide us with a natural source of this fresh, nutrient-packed seafood. More wild salmon means farmed fish are harder to justify, both economically and environmentally. And someday soon, some of those salmon may have grown up in a valley in central California — denizens of the West Coast through and through.
Fry JP, Love DC, MacDonald GK, et al. Environmental health impacts of feeding crops to farmed fish. Environment International. 2016;91:201-214. doi:10.1016/j.envint.2016.02.022
Hemmingsen W, MacKenzie K, Sagerup K, Remen M, Bloch-Hansen K, Dagbjartarson Imsland AK. Caligus elongatus and other sea lice of the genus Caligus as parasites of farmed salmonids: A review. Aquaculture. 2020;522:735160. doi:10.1016/j.aquaculture.2020.735160
Katz JVE, Jeffres C, Conrad JL, et al. Floodplain farm fields provide novel rearing habitat for Chinook salmon. Dias JM, ed. PLOS ONE. 2017;12(6):e0177409. doi:10.1371/journal.pone.0177409
Rice fields could be the savior for California's imperiled Chinook salmon. The Counter. https://thecounter.org/california-chinook-salmon-rice-fields-biographic/. Published January 14, 2020. Accessed June 19, 2020.