Salmon smolts in dammed rivers have a higher survival rate than a free flowing watershed?

Surprisingly, smolts fared just as well negotiating the heavily dammed Columbia as they did going down the free-flowing Fraser. Comparing the rivers section by section, Chinook smolts traversing the dammed system actually had higher survival rates than their cousins in the Fraser. Adjusting estimates to consider the distance and time smolts had to migrate to reach the river mouth revealed that average survival rates were much higher for both species from the Snake River than for those in the undammed Fraser. In fact, no matter how they analyzed the data, the researchers reported, “survival is not worse in the Columbia despite the presence of an extensive network of dams.”

Plos Biology has published a paper outlining a recent study of downstream migrating salmon smolts that suggests dammed rivers enhance the survival rate of ocean-bound fish. A combination of factors are mentioned, but no conclusions are drawn.

A synopsis of the article has also been posted, absent the graphs and methodology.

They found some of the salmon – most just the length of a hot dog – could swim distances up to 2,500 kilometres in only a matter months, putting their pace at about a ‘Phelpsian’ two body lengths a second – a reference the researchers made to the record-setting Olympic swimmer Michael Phelps.

Considering Michael Phelps only had to keep it up for a minute or two, that’s some powerful biological programming.