Tagged.

• Author: Schmitz, Richard F.
• Position: Tagging of Yukon River salmon

For some Yukon River salmon, this summer's spawning run will take a high-tech twist as fisheries biologists issue as many as 1,100 fish radio transmitters at a watery pull-over a little downstream from the village of Rampart.

The project is part of an international effort to better understand where and when the economically important run of fall chums spawn. Scientists are particularly excited about the project because of recent advances in the science of biotelemetry, explained Richard Wilmot, research geneticist with the National Marine Fisheries Service's Auke Bay Lab in Juneau.

Biotelemetry is the science of monitoring biological activity. It could include, keeping track of a cardiac patient's pulse with a heart monitor or tracking a garbage bear fitted with a radio collar. New technology is allowing scientists to increase knowledge in ways unimaginable a decade ago, Wilmot said.

"It's starting to get really big now. New kinds of tags are allowing scientists to measure (a fish's) body temperature as well as where it is," Wilmot explained.

New "archival tags" are also allowing scientists to study salt-water species, such as sablefish. Because tags cannot transmit through salt water, the archival tags use data chips to store information about body temperature or movement over a period of time. The tags are collected in the field or turned in by commercial anglers, and the data downloaded for analysis. (Those captured in the field are caught in sample nets deployed by fisheries researchers or are recovered from spawned-out fish on the spawning grounds.)

Thanks to the new tags, one remarkable discovery has already been noted by fisheries biologists. "We're learning all kinds of things about what fish are doing in the ocean," Wilmot said. "Particularly incredible is how far fish can travel in 24 hours. We're seeing huge vertical migrations in very short periods of time."

"It's still a fairly new technology," said Auke Bay Lab research biologist John Eiler. "At first, tags just put out a signal. Now you're at a point where you can look at temperature, depth, activity." Also, smaller tags mean increasingly smaller species can be studied, while new timing options allow tags to be pre-set to turn on at a later date-or to operate for a specific time each day.

The upper Yukon fall chum salmon study is based on a high-tech loop that begins with a small, $200 radio transmitter placed in the salmon's stomach-the stomach being a perfect place for the...