Invasive species. What a buzzword. I’m going to go out on a bit of a ledge here and assume everybody has at least heard the term thrown around. With a world more connected than at any point in history, it’s quite easy for organisms to hitch a ride with humans to new environments they’ve never encountered before. Hell, even 1000 years ago it was possible for yeast to get from Patagonia to Germany and induce an explosion of a new style of beer.
But that’s the less-common pleasant surprise than the environmental nightmare that is more typical of invasive species. Take, for example, the zebra mussels that have completely taken over the beds of the Great Lakes. Or the cane toad that has gone out of control in Australia and other tropical regions.
When a new species in introduced to an environment, there’s always the chance that they’ll take over. They might be able to eat everything around them but have no natural predators in the area. Or they might just reproduce faster than the native species. For whatever reason, they outcompete the locals, explode in population, and drive the native species’ numbers down to near or complete extinction.
But every now and then, the hard work and determination of knowledgable scientists can turn the tide.
A recent study from the University of Wisconsin tells one of these tales. In Sparkling Lake, one of northern Wisconsin’s ridiculous smattering of small lakes, the rusty crayfish had all but taken over. Whether for defensive purposes or sheer evil genius, they used their claws to snip aquatic plants right at their roots and completely deforest the lakebed. The consequence: the removal of critical cover for other species who then had nowhere to hide from predators.
Today, native species like pumpkinseed fish and bluegills have rebounded, as have the natural fauna of the lake. The crayfish, on the other hand, have not fared so well; they are relatively rare in Sparking Lake’s waters. The rebounding population of smallmouth fish is prettying on crayfish larvae and juveniles, and species that were down to their final few dozen specimens are back in force. So what was the secret?
Four years’ worth of crayfish boils.
Researchers from the University of Wisconsin spent entire summers and plenty of time and money meticulously catching the invasive crayfish. “We were catching 1,000 a day and eating them all the time,” said former postdoc and lead author Gretchen Hansen, who now works with the Wisconsin Department of Natural Resources.
Now there’s a summer job I want to have. Get paid to spend your time outdoors, eating ridiculous numbers of crayfish, all the while working toward a doctorate.
Of course, the news isn’t good for all species. The environment and food chain is never that simple. No matter how well-intentioned our conservation efforts, there’s always the chance – even likelihood – that it will have unintended consequences.
“Sparkling Lake used to have tons of mayfly larvae, but now you can’t find any,” Hansen says of an invertebrate species that made up a key element of the lake’s food web. “We thought they would rebound, but they haven’t. But it’s a transient thing, and we only know how the lake is now, four years later. That doesn’t mean that’s what it’ll be like in another four years.”
The study, “Food web consequences of long-term invasive crayfish control,” was published in the Canadian Journal of Fisheries and Aquatic Sciences by Hansen and a handful of corresponding authors all from the University of Wisconsin’s Center for Limnology (study of lakes).