KAMILCHE (September 17, 2007) – Juvenile coho salmon are disappearing before they can migrate out of deep South Puget Sound, according to results of a three-year acoustic tracking study by the Squaxin Island Tribe. Only 6 of 175 young wild and hatchery coho fitted with acoustic tags were tracked beyond the Tacoma Narrows Bridge.
“That is an incredibly high drop off,” said Scott Steltzner, fisheries research biologist for the tribe. “Three to 4 percent of all South Puget Sound coho survive their entire three-year life cycle. We know that some juvenile salmon die along the way, but there shouldn’t be this drastic of a drop so soon.”
In addition to tagging hatchery coho from the tribe’s netpen facility in Peale Passage, the tribe also tagged and released wild coho from Mill Creek in Mason County. Fifteen receivers arranged between the Tacoma Narrows Bridge and Oakland Bay near Shelton tracked the acoustically tagged coho as they left deep South Puget Sound.
The study shows that fish disappear quickly as they swim north towards the narrows. Most of the tagged coho were detected by receivers near their release point, but only 25 made it halfway to the bridge.
The low number of coho surviving the relatively short journey points to an imbalance in the local ecosystem. “We know that a lot of coho aren’t making it very far, but we don’t know why,” said Steltzner. Possible causes could include a lack of food for the young fish or an over-abundance of predators. “If there aren’t enough fish for the coho to eat, or there are too many fish that eat coho, they aren’t going to have much of a chance.”
In addition to the tagging project, the Squaxin Island Tribe also tracks coho populations using smolt traps and spawning surveys. Smolt traps are devices that allow the tribe to safely capture and count juvenile salmon as they migrate downstream to sea. Spawning surveys are conducted to count returning adult salmon. “We get a good look at these salmon at the both ends of their lives, but what happens in the middle is still a mystery,” said Steltzner.
“If we’re seeing this many coho die so soon, Puget Sound if definitely not working the way it should,” said Andy Whitener, natural resources director for the Squaxin Island Tribe. “You can’t assume that this kind of drastic die off is natural and we know that Puget Sound has been impacted dramatically in recent years. This data shows the urgent need to find out why these fish are dying and how Puget Sound is ailing.”
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For more information, contact: Jeff Dickison, assistant natural resources director, Squaxin Island Tribe, (360) 432-3815. Scott Steltzner, biologist, Squaxin Island Tribe, (360) 432-3803. Emmett O’Connell, information officer, NWIFC, (360) 528-4304, [email protected].
