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August 21, 2015
ROSEBURG, Ore. – High water temperatures and repeated bouts of bacteria and parasite infections beginning in May have killed over 150,000 summer steelhead fingerlings at Rock Creek Hatchery.
The hatchery began losing fish in May when warm water temperatures led to outbreaks of both a bacterial infection and external parasite common in fish hatcheries, according to Dan Meyer, ODFW hatchery manager.
“We immediately treated the fish and got them healthy, but once we moved them to outside raceways, the disease broke again and again,” Meyer said. “However, the combination of pathogens and unusually high temperatures created a perfect storm that we were never able to get out in front of.”
Although the majority of the fish died the week of July 9-17, when Meyer estimates losses were as high as 15 percent a day, hatchery staff didn’t realize the full extent of the loss until a routine inventory in early August. During much of June and July, when the fish were under constant treatment for infection, they were not healthy enough to withstand the sampling needed to get a more accurate count.
According Craig Banner, ODFW fish pathologist, columnaris (a bacterial infection) and ichthyphthirius (an external parasite often known as “ick”) are found in low levels in the North Umpqua River, which supplies water to the hatchery. When water temperatures rise, pathogen levels can increase rapidly, overwhelming a fish’s natural defenses. Water temperatures in the North Umpqua River exceeded 71 degrees in July, compared to previous years where highs were in the mid-60s.
Meyer said it will be difficult to accurately estimate the total extent of the loss until the fish are larger and ready for release in October. However, the loss is significant and Meyer estimates it could reach 95 percent. The impact on future fisheries is also difficult to predict. To meet the objectives of the Coastal Multi-species Conservation Plan, the hatchery had increased its summer steelhead production this year so there were more fish to start with. Also, summer steelhead in the Umpqua tend to return over a two year period so any declines in returns could be spread over time.
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