ROSEBURG, Ore – Oregon Department of Fish and Wildlife hatchery staff are reporting an unusual level of loss among spring Chinook eggs and newly hatched fish at Cole Rivers Hatchery. Agency fish health specialists believe an algae overload and aging infrastructure is the likely cause of the loss.
Approximately 360,000 spring Chinook eggs and fry died since December 7 due to low dissolved oxygen and fungus resulting from excess algae and failing equipment that allowed silt and debris into the hatch house water supply. Fish health staff did not see signs of infection or parasites, but are processing samples for further testing.
Hatchery coordinator Ryan Couture said Cole Rivers Hatchery staff closely monitor fish and eggs during incubation and took immediate steps to try to slow fish loss.
“Last Friday, staff noticed the incubation egg tray screens were plugging up with abnormally high amounts of algae and eggs with fungus that were reducing water flow and oxygen to the developing fish,” Couture said. “Water temperatures were decreased to slow the level of fungus growth. Fry from some of the incubation trays were moved into troughs to try to decrease mortality. The remaining incubation trays were then spaced out to maximize water flow and oxygen levels.”
This loss is 15 percent of the hatchery’s total inventory of eyed eggs for spring Chinook with more than 1.9 million eggs remaining. Couture said the loss could be higher once fish are put into hatchery ponds, but the final count will not be available until the fish are marked in late spring. Loss after marking is typically minor.
“We should be able to meet smolt production goals, but won’t know until fish are marked,” Couture said. “We are hopeful any impacts to anglers will be minor.”
Cole Rivers Hatchery releases 1.7 million spring Chinook salmon as mitigation for spawning and rearing areas blocked by the William L. Jess Dam. ODFW staff have been discussing equipment repairs or replacement with the U.S. Army Corps of Engineers which built the hatchery in 1973 and continues to own and fund its operation.
Fish health staff are traveling to the hatchery today to further examine the spring Chinook eggs and inspect water treatment equipment.
Hatchery spring Chinook releases from current inventory are planned for August, September, and October 2019 and March 2020.