But with the help of high-tech electronic devices the size of a grain of rice, managers of the Columbia River Basin salmon recovery program have been able to do just that since 1987. The tags emit a unique signal when the marked fish swims past scanners mounted at federal dams. Until this spring, only the fish ladders at Lower Granite Dam on the Snake River in eastern Washington state were equipped to detect returning adults. This year, PIT-tag sensors were installed in a fish ladder at Bonneville Dam on the Columbia River between Oregon and Washington. The sensors got their first test last week.
Computers connected to the sensors keep track of each fish.
They also are considering adding detectors in the ladders at McNary Dam in Eastern Oregon. Biologists are practically salivating at the prospect. We can use this tool to really find out what makes these fish tick. The PIT-tag program already has yielded results, although some scientists have questioned conclusions drawn from the findings because of the small sample size and the lack of a good control population. PIT-tag records that track individual salmon as they make their way past dams show that 40 percent to 50 percent survive the journey past four dams on the lower Snake River and four dams on the Columbia, the National Marine Fisheries Service says.