|Radio implants to track salmon through Delta
By Matt Weiser
Published: Saturday, Nov. 15, 2008 | Page 3B
A swarm of 6,000 bionic salmon has become the latest tool in an ongoing struggle to protect declining fish species in the Sacramento-San Joaquin Delta.
Researchers began releasing the radio-tagged salmon into the Sacramento River on Friday. It's an unprecedented effort to answer one of nature's mysteries: Why do young salmon choose one fork in the river instead of another on their migration to the sea?
Results of the $6 million study may show that both natural signals and human manipulation of water flows hold the answer.
The 8-inch chinook salmon were reared in a hatchery. Each has a tiny radio transmitter implanted in its belly, which emits a signal unique to each fish.
The first 300 salmon were released Friday into the Sacramento River just downstream of the Tower Bridge in Old Sacramento.
The U.S. Geological Survey, which is leading the study, has installed more than 50 sensors in the river between Sacramento and Pittsburg to pick up signals from the fish.
"This is pretty bleeding-edge stuff," said Jon Burau, USGS project chief.
Data from the study may also be used to show how a proposed water canal around the Delta might affect salmon.
The canal is similar to one rejected by voters in 1982. It is being sought by statewide water interests to protect another native fish, Delta smelt, which are killed by water deliveries from the Delta.
But a new canal's intake would be located somewhere south of Sacramento, potentially harming salmon instead.
"The data could be used for that, and I'm sure will be," said Jim Wilde, the study's coordinator at the California Department of Water Resources, which is funding the research. "What we want to get out of this is management tools."
Water interests got another reason to press for the canal Friday, when the California Fish and Game Commission added new Delta pumping restrictions to protect another smelt, the native longfin. The interim rules could mean a 50 percent cut in water supplies for Southern California next year.
DWR estimates the longfin protections will cut Delta water deliveries by 1.1 million acre-feet, or enough to serve more than 2 million homes.
"This is not people vs. fish," Commissioner Cindy Gustafson said after voting for the limits. "Because at some point, everything we do in our environment is coming back to affect the people. When we start damaging our ecosystem, it will have impacts."
The study will help improve existing water operations to protect fish, Wilde said.
Salmon survival in the Delta varies depending on how long fish stay in the estuary, where they go and how they migrate through its braided channels. Some water operations can be adjusted to vary these effects.
The research is important for both the endangered winter-run chinook salmon and the fall-run chinook. The latter make up nearly all of the West Coast's commercial salmon catch. A sudden decline in the fall run prompted the first statewide closure of salmon fishing this year.
The USGS equipped two key Sacramento River "intersections" with extra sensors to produce three-dimensional images of salmon behavior in the water column. These intersections, both near Walnut Grove, are at the Delta Cross-Channel Gates, operated by the U.S. Bureau of Reclamation, and at Georgiana Slough.
Salmon taking these detours leave the main river channel and end up in the Central Delta, where they are exposed to more predators and their path to the ocean becomes more complicated.
Surface currents may drive salmon into these detours. Researchers will deploy two custom-built robotic boats to measure those currents.
The aluminum craft, painted yellow, look like torpedoes with outriggers. As long as a kayak, they bristle with antennae and sensors. Computer programs and GPS signals will steer the boats in precise patterns to map the currents.
Results could prompt operational changes to persuade salmon to avoid the detours. They could also determine the best site for a canal intake. For instance, it might be bad to place the intake near a river bend, where currents could sweep fish into the canal.
"We want to be able to predict what the effect might be with future operations of the (water) system," said Burau. "We can do a pretty good job predicting where the water's going to go. We're trying to do that with salmon, too."
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