SEATTLE – A fish kill attributed to a lack of oxygen in Hood Canal this week may have been worse than 2003’s record kill on the fiordlike waterway, a scientist says.
This time, researchers are better prepared to track the reasons why oxygen levels are low – and why the low-oxygen water rose to the surface so quickly that fish, hovering near the surface to get what little oxygen was available, had no time to flee to healthier waters.
Thousands of dead fish washed ashore, most on Tuesday. There were no reports of additional deaths Thursday morning, so the event may have peaked.
“We sure hope so,” said oceanographer Jan Newton at the University of Washington.
The sheltered, 60-mile-long waterway west of Seattle separates the Kitsap Peninsula from the larger Olympic Peninsula. The portion of the canal affected by this year’s kill is between Tahuya and Lilliwaup – and is larger than the area of the 2003 kill, Newton said.
Since the 2003 fish kill shocked the region, 28 area groups formed a partnership – the Hood Canal Dissolved Oxygen Program – to work with state, local, federal and tribal policymakers. The state has installed four sophisticated buoys that monitor water quality. More research dollars have come available.
Hood Canal oxygen levels in 2004 were nearly as low as in 2003, but the low oxygen water remained at the bottom of the waterway, with little visible impact.
Several factors may have contributed to this kill.
State Fish and Wildlife Department scientist Greg Bargmann noted that a storm blew in last weekend.
Water at the surface absorbs oxygen from the air, so typically the top 50 feet or so are well oxygenated, he said. Below that, oxygen levels are lower. The canal is as deep as 350 feet in places.
“What we think happens is that there’s more nitrogen entering the water of Hood Canal that encourages the growth of small algae. As they deplete oxygen and as sunlight fades, the algae die and settle to the bottom and rot. That takes up oxygen in deeper water as bacteria feed on it,” Bargmann said.
When the wind blew in from the south over the weekend, it pushed the surface water to the north, toward the Hood Canal Bridge.
“The surface water leaves and the low-oxygen water comes all the way up from the bottom to the top, and fish and other animals suffocate,” Bargmann said. “I think that’s what happened Sunday and Monday in the canal.”
And it happened fast, he said: “Within hours, the upper-level oxygen supply was all gone.”
When the wind stopped Tuesday, he said, the surface water again absorbed oxygen, “so fish and other animals had a refuge.”
On Thursday, fish were no longer dying, “but they’re crowded into very shallow water, 20 feet or less,” Bargmann said. The refugees include deep-water creatures – shrimp, crab, ling cod, rockfish and octopus.
“They look like a dog that’s panting on a hot summer day,” Bargmann said. “They’re very listless.”