Issue link: https://www.e-digitaleditions.com/i/1310869
RESEARCH UPDATE 21 Salmon Research Hints at Solutions for Water Availability In early 2020, Rachelle Tallman had an unusual job: "fish babysitter." A graduate student researcher at the University of California (UC), Davis, she spent the late winter and spring watching thousands of caged, juvenile salmon feasting in the zooplankton-rich waters of two flooded Sacramento Valley rice fields. As the fingerlings grew to reach nearly three inches long, it was time for Tallman to switch from babysitter to surgeon. "Fish are super squirmy," she said. "To keep them still enough for surgery would be difficult, so we do have to anaesthetize them." A quick dose of anesthetic calms the young fish long enough for the two-minute process needed to implant a tiny acoustic transmitter. Tallman's team repeated this fish-tagging routine nearly a thousand times before releasing the salmon into the Sacramento River toward their hoped-for destination – the Pacific Ocean. "For juvenile salmon, it's such a difficult life history," said Andrew Rypel, Ph.D., associate professor in Coldwater Fish Ecology at UC Davis. "They're born into a super dangerous world, and then they basically have to become marathoners and swim this massive distance. You look at the distance from the Coleman Fish Hatchery (on Battle Creek near Anderson, California) all the way to the Golden Gate Bridge – baby fish have to make that huge migration. So you can see why they often have low survivorship." In a wet year, Rypel said, the chances of a juvenile winter-run chinook salmon making it to the ocean might be upwards of 20%, but in drier years with lower river flows, those odds can drop into the 0-3% range. Rypel and other UC researchers are hoping to improve those odds by working with rice farmers on a project that is also supported by the Almond Board of California (ABC), other major sponsors including the USDA Natural Resources Conservation Service and Syngenta, and other supporting organizations. Their success would not only improve conditions for the salmon, whose numbers have declined dramatically over the past half century, but also for farmers – not just of rice, but also growers of almonds and other crops that depend on an increasingly limited water supply, partly due to tighter water restrictions intended to protect fish. "Declining fish populations in California place a major regulatory burden on people who use water, and agricultural communities are largely affected by this. Fish and farmers have been pitted against each other for some time," Rypel said. "Yet both groups' interests are more closely tied to each other than we previously realized. Fish need the farmers to help them, and I think farmers need the fish populations to get healthier. Thinking about sustainability in that sort of reconciled way is a relatively new concept in California, but in the long-run it's really the only path towards viable solutions for both fish and people." After growing in rice fields at River Garden Farms, the salmon are transported to a canal, where they await tagging before being sent on their journey toward the Pacific Ocean. Photo courtesy of Jim Morris, California Rice Commission By feeding on zooplankton — tiny bugs and other animals in rice field water — baby salmon can quickly grow to nearly three inches long. At that length, Tallman and other researchers can implant an acoustic transmitter in the salmon and track their progress to the ocean. Photo courtesy of Jim Morris, California Rice Commission