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Ecologist Alexander Wilson spent most of the summer of 2014 floating in a boat on Canada’s Opinicon Lake in eastern Ontario. Over the course of about six weeks, the Deakin University researcher landed 200 of the lake’s bass. While he is a recreational angler, this particular fishing effort wasn’t for fun. It was for science. He wanted to find out how recreational fishing might drive evolution by changing the genetic makeup of fish communities.
If certain individual fish have traits that make them more susceptible to being caught, then fishers can unknowingly select for or against those traits. If fishy personalities are heritable, then anglers could unintentionally be altering the genetic landscape of the species they target. While some researchers have investigated this possibility for large-scale commercial fisheries, fewer have considered recreational anglers.
That’s why Wilson found himself combining his personal and professional interests, reeling in 100 rock bass and another 100 largemouth bass. Half were caught using an active crank system that drags a bright, dangly, noisy lure through the water, while the other half were fished more passively with a drab, simple, silent lure that dangles motionless. If the techniques selectively attracted fish with different temperaments, then the bolder fish might be more likely to go after the garish lures, while more timid fish would be more likely to nibble at the boring ones.
Once landed, the fish were brought back to a laboratory where the researchers evaluated their personalities. The researchers timed how long the fish waited before emerging from their holding pens into a larger tank, how long they continued to avoid fishing nets after being captured, and how close they would tolerate a looming net before trying to swim away from it. Bolder fish would be more eager to explore their new habitats, less fearful of approaching nets, and so on.
As predicted, the fish caught with the passive method were more cautious, hesitant to swim out of the comfort of their holding pens. Those hooked by the active method were on average bolder, daring to adventure into the unknown experimental fish tank.
While different fishing techniques attract fish with different personalities, it isn’t yet clear just what the implications for their populations are. “It’s difficult to have a concrete conservation take-home lesson now, but the fact that there’s differential catch suggests there’s a whole series of other questions you’d want to ask,” says UCLA evolutionary biologist Dan Blumstein, who was not involved in the study. And that’s the case for fish that swim through salty seas as well as those that prefer fresher waters.
If personality differences are encoded into their DNA, and if recreational fishers in a given region predominantly use a single fishing technique, then the consequences for the genetic landscape of the fish could be extensive. For now, these are unanswered questions, but we do know that wildlife populations with less genetic diversity tend to be less able to withstand the stresses of extreme weather, disease, and climate change, for example. Indeed, as Natasha Loder wrote nearly a decade ago in Conservation Magazine, “fishing may be such a powerful evolutionary force that we are running up a Darwinian debt for future generations.” It’s a problem that fisheries managers need to be prepared to tackle.