Chinook reach the ladder after a long journey up the Yukon River from the Bering Sea. It's one of the longest upstream salmon migrations in the world.

von Finster said the water was high in the river all of last summer, making it harder for salmon to travel upstream to reach Whitehorse, and then have enough energy to navigate the fish ladder around the Whitehorse hydroelectric dam.

"So first, the fish just simply weren't there. Secondly, the fish had to fight against the current going up and I think some of them probably were just exhausted when they hit the dam," he said.