• By Bob Johnson •
A team of researchers is waiting to learn how many of the small chinook salmon that were raised on the healthiest of food in Mike Dewit’s rice field in the Yolo Bypass, fitted with microtransmitters, and released into the Sacramento River in late April survive the arduous journey to San Francisco Bay and the ocean beyond.
The study of the survival to adulthood of these 900 young fish is part of an ambitious three-year $1.4 million pilot project aimed at learning if the rice fields can play an important role in providing habitat for salmon, as they already do for sandhill cranes and other waterfowl.
“The growers are very much into it,” says Paul Buttner, California Rice Commission project manager for the Helping Salmon in the Sacramento Valley project. “They understand the salmon fishery in the Sacramento Valley needs help, and if the rice fields can be part of it they find that exciting.”
Growers and researchers from the University of California, Davis, Center for Watershed Sciences, the California Department of Fish and Wildlife and California Trout came together to study how the fields can provide young salmon with nutritious food and protection from predators until they are ready to begin the long trip down the Sacramento River.
“We’re hoping to find that if salmon have a chance to get bigger, more of them will make it,” Buttner says. “A very few of them normally make it all the way to the ocean.”
Radio-tracking young salmon
In late April, a team of researchers from UC Davis, led by graduate student Rachelle Tallman, carefully inserted microtransmitters into the young fish that make it possible to track them as they make their way to the Golden Gate.
“We will know towards the end of the summer how many of them made it to the San Francisco Bay,” says UC Davis wildlife, fish and conservation biology associate professor Andrew Rypel. “Usually, about 3-5% of the fish released from the hatchery make it. Something like 20% would be great; anything above 10% would be good.”
Previous research has already shown the potential for rice fields as breeding grounds for zooplankton, which feed on algae and in turn serve as nutritious food for the young salmon, and as a source of calm water.
“We already know if you put salmon in rice fields they grow incredibly fast,” Buttner says. “The water is calmer than the river, and the fields have an incredibly nutritious food web. What we don’t know is if that means more of them will make it out to the ocean.”
Rice fields that can directly connect to the Sacramento River offer the best opportunity to replicate the habitat that young salmon historically counted on to get off to a healthy start in life.
“We would like them to voluntarily swim out of the field to the river,” Buttner said. “It pretty much has to be inside the levee, and that restricts us to about 30,000 acres of fields in the Sutter Bypass and Yolo Bypass. Historically, the salmon started in the floodplain, not the river. We have places we can replicate the floodplain; we’re test driving the idea of replicating the floodplain.”
Finding the right fields
After screening candidate fields for the first pilot, the project team selected a farm DeWit leases in the Yolo Bypass.
DeWit, who has farmed rice in Sacramento and Yolo counties for 30 years, supervised the work necessary to prepare the rice fields to be fish-friendly, and to clean out the drainage channel leading out of the fields to provide good water flow for the salmon as they head toward the Tule Canal.
“We know that we can provide the food,” DeWit says. “How to get the food to the fish is something to work on. We’re going to try to do a surrogate floodplain. Getting the fish to the floodplain is the hard part. Birds fly, so that part is easy with them. The science is there, so I know we can do it, but salmon don’t fly, that’s our hurdle.”
With the field and canal prepared, protective cages were put in place in DeWit’s field in March to ensure that the fish would be safe from predators as they grew large enough to be tagged with the transmitters and set loose for their journey down the Sacramento River.
The California Rice Commission is regularly updating progress of the research into Helping Salmon in the Sacramento Valley through a webpage devoted to the project (http://salmon.calrice.org/).
The project has attracted financial support from a range of sources including, among others, the U.S. Department of Agriculture Natural Resources Conservation Service, Syngenta, Valent and the California Almond Board.
Buttner says he hopes the result will be a well-defined conservation practice that will let the NRCS support participating farmers with both technical information and funds for the additional tractor work.
DeWit, who is a board member on both the California Rice Commission and the California Ricelands Waterbird Foundation and has been involved in wildlife-friendly farming for many years, sees the project as an opportunity to build on recent years of cooperation between rice farmers and environmentalists.
“We were at odds with the environmental community 20 or 30 years ago; it was us against them,” DeWit says. “We’ve learned to work with them and I think it’s been great. This is a way to further our relationship with our environmental partners.”
This article first appeared in AgAlert, the weekly newspaper of the California Farm Bureau Federation.