Debris washed into the creek from recent rains clogged an intake pipe, apparently causing the fish to die from oxygen deprivation, said Marcia House, a fish pathologist with the Northwest Indian Fisheries Commission. The dead fish were removed Wednesday.
"It appears to be a water-flow problem," House told the Kitsap Sun. "There were no indications of any fish-health problems."
Jay Zischke, the tribe's salmon program manager, said the loss amounted to about 90 percent of the 1.8 million juvenile chinook salmon that were set for release.
"It is painful to go through one of these events and see so many fish die rapidly," Zischke said.
The incident is expected to slash the number of adult chinook returning to Gorst Creek in 2010, when most of the adults would return to spawn, likely meaning reduced opportunities for recreational, commercial and tribal fishing, especially around Sinclair Inlet.
Tribal fisheries director said steps would be taken to prevent a recurrence of the problem, possibly by installing an alarm system to provide a warning when water flow is halted or by using aeration equipment to boost the oxygen level in the water, as is done in the winter when intake screens are frequently blocked by silt or debris.
The fish ponds are a joint operation of the Suquamish Tribe and the Kitsap Poggie Club in cooperation with the city of Bremerton and Washington Department of Fish and Wildlife.
"We put a lot of volunteer hours into this project, starting at the hatchery and then spending four days a week, twice a day, feeding the fish," said Ray Frederick, president of the Poggie Club.
Suquamish workers oversee the operation and handle the rest of the feeding.
The eggs are hatched at Grover's Creek in north Kitsap County after adult fish return to spawn, and the fry are then moved to Gorst to be reared in ponds and fed by hand until their release.