An Undersea Catastrophe

Within the space of two decades, the salmon we eat have gone from being mainly caught on the high seas to being mainly raised in pens. It has actually become a challenge to find fresh or frozen wild salmon in Canadian stores and restaurants. One of the tricks these days is to realize that anything labelled “Atlantic” has come from a farm, while most of the tinned stuff is still caught in the wild by fishers.

The magnitude of this event in the history of humans is hard to overestimate. It is the first time we have been able—with whatever success—to domesticate a wild carnivore for mass consumption, despite thousands of years of failed attempts. (Yes, salmon are carnivores, living primarily on zooplankton when small and then on larger marine animals and fish as they mature.)

According to natural historian Terry Glavin, who wrote the introduction to A Stain upon the Sea: West Coast Salmon Farming, edited by Stephen Hume and several others, this fact...