Bull trout finds its way over fish ladder

A bull trout has made its way through the fish ladder at the Thompson Falls Dam last week, bringing to 16 the total number of bull trout that have used the fish ladder since its installation in 2011. When they enter the ladder, each bull trout is tagged with a PIT tag, or Passive Integrated Transponder, and then they can continue their journey over the dam.

The ladder is checked daily during the months of March through October. There are antennas positioned in the fish ladder that can send out an alert when a fish has entered the bottom of the ladder and another one near the middle to show where in the ladder the fish is. There are also antennas at the mouth of the Thompson River and the Fish Trap Creek and West Fork of Thompson River tributaries.

The last bull trout that passed through the ladder before the newcomer was in 2017. Jon Hanson with Montana Fish, Wildlife & Parks anticipates that the numbers will stay the same in future years but is hopeful that bull trout will increasingly use the ladder.

"They were here long before we were so it's good to see them use the ladder," Hansen said.

The Thompson Falls fish ladder was built to help the bull trout reach spawning areas. Bull trout are now listed as threatened on the endangered species list.

Bull trout were once very common throughout the Pacific Northwest, Hanson said. Their range spread from northern California all the way to the Bearing Sea. Bull trout are extinct from California and are present in only one river system in Nevada. The populations in Oregon and Washington are at high risk for extinction.