Idaho Fish and Game released more than 1 million sockeye smolts from Sawtooth Hatchery into the Upper Salmon River on April 30 after detecting some mortality due to high-intensity runoff. Unusually warm weather in the Stanley area led to increased water temperature, low dissolved oxygen levels and high turbidity in the Upper Salmon River, which is the water source for the hatchery.
Water conditions in the hatchery raceways stressed and killed about 31,250 sockeye smolts, which is less than 3 percent of the total release. The fish were in their final stage of acclimation at Sawtooth Hatchery, and hatchery personnel planned to transport the fish to Redfish Lake Creek for release during May 5-7. The fish had been acclimating at Sawtooth Hatchery since they were trucked from Springfield Hatchery from April 19-28.
Rather than risking additional mortality, Fish and Game managers decided to release the remaining estimated 1,012,648 smolts slightly early and directly from the hatchery into the Upper Salmon River. This decision was based on fish conditions in the raceways and a forecast for continued warm weather.
The mortality event was limited to smolts in the raceways, and once released, no dead fish were apparent. The mortality at the hatchery did not reduce the release goal of at least 1 million smolts.
The release into the Upper Salmon River instead of Redfish Lake Creek will likely increase the number of adult sockeye that return to Sawtooth Hatchery in two to three years rather than migrating up Redfish Lake Creek. Sawtooth Hatchery has facilities to trap returning adult sockeye. Even for smolts released into Redfish Lake Creek, it is common for a portion of them returning as adult sockeye to be trapped at Sawtooth Hatchery.