Number of returning coho salmon drops
October 19, 2010
By Laura Geggel
Hatchery may not have enough eggs for schools, co-ops
In any given year, about 30,000 coho salmon pass through the Hiram M. Chittenden Locks in Ballard, swimming to rivers and tributaries like Issaquah Creek, on a mission to reproduce before they die.
This year, coho counts are down, with only 3,608 coho swimming through the locks, as of Oct. 6. The Muckleshoot Tribe recorded the last low of 6,000 coho in 2002 and the highest run of 47,000 coho in 2000.
Many of the fish that swim through the locks make their way to Issaquah Creek and the Issaquah Salmon Hatchery. Others return to Bear Creek, the Cedar River and the other major streams of the Lake Washington and Lake Sammamish watershed.
As of Oct. 18, about 400 coho had arrived at the hatchery, Friends of the Issaquah Salmon Hatchery Executive Director Gestin Suttle said.
“Normally, they would have more than 1,000 at this point, so it is a low run this year,” Aaron Bosworth, district biologist with the state Department of Fish and Wildlife, said.
Each female coho has about 3,500 eggs. The hatchery needs 1.3 million eggs to successfully breed for the next season. When returns are met, the hatchery gives about 500,000 eggs to cooperatives and about 20,000 eggs to schools, which raise the fish and release them into the wild.
“We need at least 600 females to reach our program goal for eggs, so if you figured that even if half of those 400 on hand are females, that would still leave us short, so we are very concerned,” Suttle said.
Hatchery Supervisor Darin Combs said the department’s fish management is having ongoing discussions about how to handle the low coho return.
“We hate for the schools to not have their eggs,” Combs said. “I’m hoping we can cover those.”
Cooperatives, on the other hand, might not be so lucky. Only time would tell, Combs said.
Coho salmon, known to some as silver salmon, on average weigh eight pounds but can grow up to 31 pounds, according to the department’s website. They spend a year and a half both in fresh water and salt water, bringing their lifespan to about three years. At sea, “coho are very predacious, so any fish that will fit in their mouth, they’ll eat it,” said Issaquah Salmon Hatchery foreman John Kugen.
Coho can look similar to chinook salmon, except that they only have spots on the upper part of their tail, instead of all over their tail, Suttle said.
The Issaquah hatchery has bred coho salmon on and off since it first opened in 1936, Suttle said.
Citing low coho numbers, the department closed lakes Sammamish and Washington to coho fishing Oct. 2. Lake Sammamish is normally open for fishing Aug. 16 to Nov. 30 and Lake Washington is usually open from Sept. 16 to Oct. 31.
The Muckleshoot Tribe, which has rights to fish for coho in both lakes, has decided not to fish this season, Bosworth said.
“Once we realized the run was weak, they didn’t fish at all,” he said. “They have fish biologists that recommended they not fish on coho this year.”
It is unclear why the coho run is so low this year, but factors include poor ocean conditions, like warm waters or low oxygen levels.
Oddly enough, while coho returns in the southern Puget Sound are low, their numbers are normal in the northern part of the sound, Bosworth said. Fish from different areas travel to different parts of the ocean, which could explain why fish in the northern part of the sound are doing better.
Coho tend to come back in larger numbers after a heavy rainfall, and Combs said he was keeping his fingers crossed.
“I’m hoping it’s a fair amount of coho that come back with the next rain,” he said. “If not, that’s when we’ll start to worry.”
Laura Geggel: 392-6434, ext. 241, or firstname.lastname@example.org. Comment at www.issaquahpress.com.