In one West Seattle creek, salmon die before they spawn. To figure out why, volunteers are counting the dead fish.

At first glance, Longfellow Creek doesn't look that bad. Look a little closer, like these volunteers are looking and you can see a brown film that could be anything.

"Unfortunately, since Longfellow is such an urban creek, the salmon suffer from the toxic cocktail pollutants that wash into Longfellow," said Americorps Volunteer Coordinator Kerry McGowan.

Kerry McGowan coordinates volunteers for the project run by Puget Soundkeeper Alliance. Volunteers walk the waterway daily. Tuesday, Emily Favell and Jessica Daiker scoured the creek for salmon that died before spawning.

The fish are measured and their bellies are cut open to check for eggs. This year, 44% of Longfellow's salmon are dying before spawning.

"Which is actually lower than what we've seen in the past. Usually it's 60%-90%. In a natural pristine stream, it's 1%. It's negligible," McGowan said.

The pre-spawn mortality study tracks changes over time. Longfellow Creek is a dump site for storm water runoff in West Seattle. The chemical soup is lethal for coho. Sometimes it's even hard to tell if the salmon here are dead or alive.

"In the past, especially after a rain fall event, we've seen coho swimming in a disoriented pattern, gaping at the mouth, surface swimming, they look like they have no sense of direction. Usually they die a few hours after seeing that," McGowan said.

The salmon survey will help conservationists track the health of the habitat around Longfellow Creek, as well as inform plans to reduce flooding and run-off.

Longfellow Creek is one of only two salmon bearing streams in metro Seattle.