Its already been (being?) done:
http://www.nwifc.org/newsletter/28_3/13.asp Salmon Call Home On Way To Ocean
Once they migrate out to sea, scientists don’t have much information on where salmon go and what they do. But now, researchers are getting a rare glimpse into the saltwater life of salmon.
Using innovative technology, the Squaxin Island Tribe is tracking juvenile coho throughout southern Puget Sound as they make their way out to the ocean. “We know that in general salmon leave Puget Sound and head out into the ocean and return after a few years,” said Jeff Dickison, Policy Analyst with the Squaxin Island Tribe. “We’ve never been able to track them with this level of detail.”
Using an array of acoustic receivers located south of the Tacoma Narrows Bridge, the tribe tracked a group of juvenile salmon as they made their way out to the ocean. “This is one of the first times anyone will get a near real time look at individual salmon in the saltwater,” said Dickison. The pilot group of 48 will be followed up by nearly 200 coho this spring. “Last year we were making sure the technology was going to work for us. The real science starts in 2003.”
A weak hatchery coho run in 1999 convinced the Squaxin Island Tribe that they had to find out what happened to the juvenile salmon once they were released from the tribe’s netpen facility in Peale Passage. Although almost all other hatchery coho stocks that year in the Puget Sound came back at normal levels, south Sound hatchery coho returns were poor and no one knew why. “It wasn’t freshwater mortalities; these salmon are kept in saltwater netpens until they’re ready to be released,” said Dickison. “It was something that had to happen out in the sound or out in the ocean.”
When a tagged smolt passes between a pair of receivers, its individual frequency is picked up and can be tracked for several hundred yards. “If these salmon stay south of the Tacoma Narrows for any length of time, we are going to be able to gather a lot of detailed information,” said Dickison.
Compared to earlier techniques of tracking salmon, such as coded wire tags inserted in the snouts of juvenile salmon, acoustic tagging is timelier and provides much more information. “With coded wire tags, you basically have two pieces of information: where the salmon was released and where it died, whether in a stream after spawning or after harvest,” said Dickison. “But with acoustic tags, you can track many other aspects of salmon life in saltwater – for example, where a salmon might be feeding or how fast it travels through a particular area.”
Even though the technology is fairly new – some experiments in British Columbia have also been performed in the past few years – the south sound is a perfect place for it to get a test run, said Dickison. “There is only one place for these fish to leave the south sound, and that is through the Tacoma Narrows,” said Dickison. “It’s fairly easy for us to track a good amount of salmon.”
The acoustic tracking program, backed by Hatchery Reform funds, is expected to lead to more efficient hatchery operations, said Dickison. “Having more information on how these juvenile hatchery coho interact with the natural environment can suggest better ways to run the net pen operation.” Hatchery Reform is a systematic, science-driven effort to address how hatcheries can help recover and conserve naturally spawning salmon populations and support sustainable fisheries. – E. O'Connell