Last July, National Geographic reported that global populations of migratory fish have declined by 76 percent over the past half-century. Habitat loss was cited as one of the main culprits, and dams as a major cause of habitat loss. This type of cause and effect in worldwide decline holds true in the Pacific Northwest. It doesn’t take a degree in marine biology to see that dams are bad for fish. But it might take someone with a PhD to convince you that salmon don’t need rivers.