Idaho Power Can’t Say Why Salmon Died Turbid River Conditions May Have Been A Reason

Idaho Power Co. said Wednesday it is trying to determine why more than 100 salmon, including up to five wild spring chinook salmon, died Monday during routine trapping operations at its Hells Canyon fish trap.

Besides the five wild spring chinook, another 96 hatchery fish, also trapped on Monday, died. The utility and the Idaho Fish and Game Department said turbid river conditions and stress may have contributed to the deaths.

Idaho Power said 25 dead salmon were discovered in the collection facility after a truckload of fish was on its way 20 miles upstream to the Oxbow Hatchery. Two of them are believed to be wild salmon. Another 30 spring chinook salmon found in the collection facility at the same time were returned to the river unharmed.

A second group of dead fish was discovered when the truck arrived at the Oxbow Hatchery. There, 76 fish were found dead, including three believed to be of wild origin.

Because of turbid water conditions, trap workers were not able to accurately determine the exact number of fish that had been trapped. Idaho Power said as a result, more fish were loaded into the transport truck than could be supported by the truck’s life support system.

Normally, no more than 70-80 fish are placed in a tanker, which is equipped with a system to inject oxygen into the water.

Spokesman Denis Lopez said it’s also possible that some of the salmon were dead when they were loaded into the tanker, but the water made it difficult for hatchery workers to see the fish.

Utility biologist Paul Abbott said contributing to overfilling of the transport truck was the high number of fish trapped on the first day of operations. Ordinarily, the trap yields very few fish during its initial operation.

“Normally we catch only a small number of fish on the first day of trapping,” Abbott said. “Returns observed at Idaho Power’s Rapid River Hatchery gave us no indication such a large number of fish were present.

“Based on their experience and observations, our employees believed there were about 70 fish in the trap at the end of the day. Because of the low visibility in the turbid water, our workers couldn’t accurately see just how many fish we had in the trap,” Abbott said.

The fish trap had just resumed operations after it was severely damaged by flood stage river flows through the company’s three-dam Hells Canyon complex earlier this year.