Experiment to Raise Salmons in Floodplains a Success

Scientists have discovered a new method of increasing the numbers of the long threatened salmons- raising them in flooded rice fields.

 A team of researchers at the University of California, Davis, through an experiment managed to increase the population of the small Chinook salmon. They introduced Chinook salmons into the flooded rice fields of Northern California, and successfully managed to recover the fattest, fastest growing salmon on record in the state's rivers.

The main aim of the experiment was to determine whether the fields that are flooded between the harvests, could act  as a substitute for the current depleted wetlands that served as nurseries  for juvenile salmon, reports Associated Press.

The report submitted to the U.S. Bureau of Reclamation describes the three concurrent studies conducted by UC researchers along with the California Department of Water Resources. The experiment was conducted in the floodplain of Yolo Bypass, which diverts floodwaters from Sacramento River. Yolo Bypass is the Central Valley's largest contiguous floodplain that offers critical fish and wildlife habitat. Agriculture is a main land use in the bypass, and rice is the primary crop.

"We're finding that land managers and regulatory agencies can use these agricultural fields to mimic natural processes," co-author Carson Jeffres, field and laboratory director of the Center for Watershed Sciences at UC Davis, said in a statement. "We still have some things to learn, but this report is a big step in understanding that."

They conducted tests on three rice field types: stubble, plowed and fallow. The researchers noticed that the fish did not prefer any of the three fields. Due to the high supply of food, the salmon growth rate boomed across habitats. But they preferred the habitat that had better water flow.

"It's like a dehydrated food web," said Jeffres of the harvested rice fields. "Just add water. All of those habitats are very productive for fish."

The experiment conducted last winter was able to generate productive aquatic food webs for salmon. The average growth rate of the salmon during the 41-day study was the highest ever recorded in the California fresh waters. The average growth of the juvenile Chinook was 0.93 mm per day, with the growth of 1.5 mm per day observed during the specific two week. The fish reared in plowed rice fields grew faster than those reared in stubble or weedy vegetation.

"These results are good news for the effort to rebuild salmon populations in California," said lead author Jacob Katz, a biologist with California Trout. "We've always suspected that when we mimic natural flood processes in agricultural fields, we give these fish a food-rich habitat they recognize and thrive in. These findings support that theory and provide a strong path forward for California land-use planners, conservationists and farmers alike. This is a win-win model that can be replicated around the state."