For generations, native Chinook salmon have made their spring migration up the Columbia River…

But over the past few decades, as their population has dwindled, salmon have been overtaken by a non-native species of fish hailing from the East Coast - THE SHAD.

Shad runs now number in the millions, while just about 700 thousand native Chinook make the trip up the Columbia each year. 

What’s behind the rise of this East Coast interloper? Humans, of course. 

But the effects of Shad on the local ecosystem? Well, that’s a bit more complicated.

Soundside host Libby Denkmann sat down with Seattle Times environment reporter Lynda Mapes to find out more about the "Chrome Tide."

GUEST: Seattle Times environment reporter Lynda Mapes

RELATED LINK: There’s a new top fish of the Columbia River — and it doesn’t mind the warm water | The Seattle Times