AVERY COOPER: More sockeye are swimming up the lower Yakima River. That’s after heavy machinery removed a landbridge that blocked the river’s flow. NWPB’s senior environmental correspondent Courtney Flatt has the story.

COURTNEY FLATT: It’s been about six months since excavators scooped out the Bateman Island Causeway in the Tri-Cities. The stagnant water behind the earthen landbridge could get really hot in the summer – and created space for predators to snack on salmon.

Now that the water is no longer blocked, biologists say they’ve seen an increase in sockeye salmon in the lower Yakima River. Almost 400 sockeye. That’s with surprisingly low sockeye numbers elsewhere – and a years-long drought.

Zac  Zacavish is a research biologist with the Yakama Nation. He says sockeye need to move quickly during hot months.

ZAC ZACAVISH: “So having that causeway out allows them to just queue in and boogie.” (0:03)

FLATT: Zacavish says these sockeye numbers are likely the highest percentage since the Yakama Nation first released sockeye for its reintroduction program in 2009.

I’m Courtney Flatt in Richland, Washington.