Stalking Steelhead With Science
Steelhead in Puget Sound have been listed as “threatened” under the Endangered Species Act since 2007. Millions of dollars have been spent improving the habitat of this iconic fish, but the population isn’t increasing. In fact, a lot of the fish aren’t even making it out of Puget Sound and scientists can’t pinpoint why.
The research vessel rocks back and forth on the gray winter waves. The Tacoma Narrows Bridge in the distance seems like the only stationary thing in the world right now.
Barry Berejikian stands on deck in a neon yellow coat. He’s a scientist with the National Oceanic and Atmospheric Administration in Seattle.
You might also call him a steelhead stalker.
And he’s about to launch a new experiment.
“This is the beginning so it’s pretty exciting," says Berejikian.
Berejikian wants to know what’s going on with these troubled fish.
To do that he’s going to tag 300 baby steelhead in the Nisqually and Green Rivers this spring.
And when those fish head to sea, he’ll be listening, so to speak – using keg-sized devices floating deep beneath the waves of Puget Sound.
The crew is dropping one off them back of the boat now.
“So right now we’re going to be deploying 8 of these acoustic telemetry receivers at the south end of the Tacoma Narrows which is about where we are now," says Berejikian.
The receivers are designed to pick up the signals from the tags in the steelhead when they swim within a couple hundred meters. The devices will be laid out in staggered rows across the sound in four places – between this site and the mouth of the Strait of Juan de Fuca.
“They’ll be anchored to the bottom and floating about 10-20 feet off the bottom," says Berejikian.
Ahearn (on tape): "So basically you’re setting up a gauntlet for out-migrating fish."
“Yeah we want to detect every fish that comes through so it’s kind of an aggressive approach but if you’re going to go to the trouble of doing the study you might as well go for it," says Berejikian.
This technology will enable Berejikian and other scientists to tag individual fish, then the devices will record them coming and going, in and out of Puget Sound.
The rivers in this part of Puget Sound are producing tens of thousands of baby steelhead every year. But scientists believe that only 20% of those fish make it to the ocean.
By following a sampling of fish, scientists can figure out where the fish are dying along their journey – and then they can start asking why that’s happening.
There are several hypotheses. Scientists are curious about the effects of more people and development in the region, disease in fish… and predators.
Steve Jeffries is with the Washington Department of Fish and Wildlife, which is collaborating with Berejikian on this research.
“The predators could be seals, sea lions, cormorants, porpoises," says Jeffries.
Jeffries is particularly curious about harbor seals, which have been known to eat steelhead and other salmon. Back in the 1970's the population in Puget Sound hovered around 2,000 seals.
“There’s about 13,000 harbor seals right now," says Jeffries.
Jeffries will be tagging 12 harbor seals in Puget Sound this spring. The tags will track the seal’s movements, and pick up on Berejikian’s tagged juvenile steelhead if they swim nearby.
“If we find out that the seals are feeding over here and the steelhead smolts are swimming through the same area then you’ve got this special overlap that it’s more likely that there is a predation going on," says Jeffries.
Ok, so what happens if the seals are eating the threatened steelhead?
“I don’t know what the answer to that question is. It’s an issue that’s going to be broached in the future. There’s no one thing that’s going to solve the problem," says Jeffries.
The researchers should have data from the tagging devices by early fall.
Copyright 2014 KUOW.