OLYMPIA - Additional emergency alarms are being installed at Naselle Hatchery on Willapa Bay after an equipment malfunction caused water flow to a rearing pond to stop Aug. 4, killing a large number of juvenile coho salmon, according to the Washington Department of Fish and Wildlife (WDFW).
WDFW Hatchery Division Manager John Kerwin said hatchery staff checking on the facility on the afternoon of Aug. 4 found that the water flow had stopped into a ½-acre asphalt-lined rearing pond, and much of the water had drained out, leaving most of the young coho salmon dead.
Kerwin said the lost fish, about 900,000, represents approximately 84 percent of the hatchery's annual coho production. The hatchery also rears about 5.5 million fall chinook, 65,000 steelhead and 35,000 rainbow trout. Those species were not affected by the incident.
Water flows and rearing pond levels are monitored both by staff during normal working hours and 24 hours a day by automated alarm systems.
Hatchery staff investigating the fish loss found a small twig had lodged between two probes of the electronic alarm system that monitors the rearing pond's water level. The twig "tricked" the system into thinking that the pond's water level was normal, when in fact about three-quarters of the water had emptied from the pond.
"We are taking immediate actions to ensure that another fish kill of this magnitude doesn't occur," Kerwin said. "A redundant alarm system will be installed as a back-up to the primary system.
"In future years, juvenile coho salmon will be reared in more than one pond to lessen the likelihood that a similar situation would affect such a large proportion of the population," Kerwin said.
The dead juvenile coho were the progeny of adults that returned to the hatchery last year. Surviving coho are scheduled to be released in June 2003. Fish are reared at Naselle to provide commercial, recreational and treaty Indian fishing opportunity along Washington's Pacific coast.
Kerwin said WDFW fisheries managers will be exploring options for lessening the impact that the loss will have on fisheries when the coho return as adults in the summer and fall of 2004.
"There are two other hatcheries within the Willapa Bay watershed that may be able to provide this facility with some juvenile coho production, but there is no way of completely overcoming the deficit this fish loss will create in both fisheries and escapement goals in 2004," Kerwin said. "Our primary concern will be getting enough of these fish back to the hatchery as adults so that we can continue to produce coho at Naselle."
State hatchery policies restrict the movement of salmon and salmon eggs, to protect distinct genetic populations of various salmon stocks and to prevent the spread of diseases from one watershed to another.