System tracks Pacific salmon's progress

January 23, 2009 7:08:21 PM PST
The Pacific Ocean holds millions of secrets for scientists who are trying to better understand the life that flourishes at sea. But thanks to a new underwater tracking system, researchers are now able to solve some of those mysteries.

For decades, scientists have tried to figure out what happens to salmon once they hit the open sea.

"One of the biggest black boxes in salmon biology is where do salmon go? Where do they spend their time when they get into the ocean," said NOAA biologist Bruce MacFarlane.

MacFarlane is a biologist at the National Oceanic and Atmospheric Administration Research Center in Santa Cruz.

"So many salmon populations are in peril today. I think it's 11 of 13 distinct populations in California are in peril and are listed by the Endangered Species Act. We need to know as much as we can in order to improve their survival and to sustain their populations," said MacFarlane.

And thanks to new technology, he and others may soon know more.

The Pacific Ocean Shelf Tracking System, or POST, is a non-profit scientific collective. They coordinate a network of data receivers dropped in rows onto the ocean floor.

When fish embedded with tracking devices swim through tracking curtains, they leave behind valuable data about their migration. The first large scale deployment was in 2006.

"The POST array gives us a tool to get more insight into where they are spending their time," said MacFarlane.

There are currently nearly 300 POST receivers on the ocean floor.

"The data is recorded on a receiver, and then later on you go out and download it with acoustic modem or in some cases you actually pull up the receiver and download the data," said Churchill Grimes from the NOAA Fisheries Ecology Division.

In Washington state, the POST System has revealed significant scientific finds:

  • 40 percent of the salmon died within weeks of entering the ocean.
  • Dams may have less of an impact on salmon survival than previously thought.

    The POST Array is also proving to be a useful tool for monitoring other species, including sturgeon.

    "I am using POST to track the migration of green sturgeon among their spawning rivers and their estuaries where they aggregate in the summer time and learning about where they spend their winters - which had been a mystery," said NOAA biologist Steve Lindley.

    Lindley is tagging and tracking fish from California's Central Valley to the ocean. Most scientists believed the green sturgeon stayed close to home. The POST Array proved that theory wrong.

    "We found that green sturgeon from the Sacramento River migrate as far north as Northeast Alaska, and they spend much of their winter in the water's of British Columbia and Alaska," said Lindley.

    Soon Lindley may know just how long the green sturgeon spends outside the bay.

    The first POST array off the California coast were put in last July. Now, fish that migrate out of the Central Valley pass monitors at the Golden Gate Bridge, and also north near Point Reyes in Marin County.

    Over the next couple years, the system will continue to expand down the coast.

    "Once the post system is fully in place and fully realized, with curtains of monitors from the Aleutian Islands to Cabo San Lucas, it's almost like field of dreams. People will come, people will buy tags and people will want to know more about where fish go in the ocean," said MacFarlane.

    And with each fish tracked, more will be learned about preserving their future.

    Until the complete network can be put in place, researchers are fine tuning the technology to maximize their results. By 2010, they hope to make significant advances in the network's capabilities.

    Written and produced by Ken Miguel.