Gotcha!

Lots of people worry about farmed salmon escaping from their cages and trying to go native. Genetic pollution? Competition? Disease? All kinds of things can happen (including, of course, nothing at all), and there’s lots of debate about that.

Nevertheless, everybody agrees that, when an Atlantic salmon turns up loose in British Columbia, it’s escaped from a farm. Salmon farmers, of course, hate to have to report every escape, which means the “official” figures are less than perfect.

But now, the long arm of the fisheries law has a new weapon: forensic DNA analysis.

On TV crime shows, suspects always look extra-shifty when they’re asked for a bit of DNA (“Relax, it’s just a routine test. Anyway, you don’t have anything to worry about. Do you?”) After what happened in Norway recently, salmon farmers are going to have to get used to the same thing. Because, when sports and commercial fishers suddenly started catching what looked like escaped salmon in one fjord in 2006, and none of the farms in the region owned up to an escape, officials from the Norwegian Directorate for Fisheries descended on the farms and took DNA samples from the fish in the net cages.

What happened when they compared the farm-fish DNA to the DNA from escapees (whose remains were also tested)? Almost all of the escapees clearly came from one farm. The farm's owners owned up to a “cage incident.”

The recent scientific paper reporting all this is, like all scientific papers, dry as dust. But the authors let down their guard long enough to say this: “It is hoped that knowledge of the existence of this method will increase the likelihood of farmers sending out reports of fish losses to the authorities.”

In other words, “gotcha!”