Round gobies the mother of all invasive fish

There is new exotic fish species running rampant these days and it has Ontario fish managers vexed and concerned.
It is a troubling pest called the round goby.
And it is now so abundant in some waters, particularly the Great Lakes, that natural resource agencies on both sides of the border are scrambling in what may be a futile attempt to halt its spread before it gains a toehold in inland lakes and rivers—and permanently alters native fish communities.
Like zebra and quagga mussels before them, round gobies are native to Eurasia. They are believed to have found their way to North America in the bilge water of ocean-going freighters.
Since it is easier for gigantic cargo vessels to navigate and buck the waves of the stormy Atlantic with weight in their cargo spaces, empty ships often fill their holds with water from the Caspian Sea or other European waterways before heading to North America.
The captains of the vessels are suppose to empty the ballast water into the salt-laden ocean before entering the freshwater environments of the St. Lawrence River and Great Lakes, but unscrupulous skippers often delay the purging process so they can make better time.
After all, time is money.
But when they subsequently empty their ballast wastewater into the Great Lakes, they also introduce exotic species like the round gobies. And they are finding Canadian conditions far too much to their liking.
Indeed, a team of Ontario natural resources scientists recently completed an underwater population census of round gobies in western Lake Erie and discovered more than 10 billion of the pests swarming on the bottom of the lake.
That’s right—10 billion of the weird-looking thick-lipped fish in just one section of the lake.
What’s worse is that as the goby population continues to rise, native species of sculpins and darters are rapidly disappearing—and some sportfish populations are crashing.
It is especially affecting walleye populations.
Indeed, there are presently so many gobies in Lake Erie that they represent the single largest biomass (pounds of fish) in the lake, prompting one Pennsylvania biologist to call them “the mother of all invasive fish species.”
The situation is so serious that there even is concern the gobies will find their way down the Susquehanna River and into Chesapeake Bay—potentially wiping out one of the most prolific shellfish fisheries on earth.
If the problem wasn’t so grave, it would be ironic. That’s because the small gobies—they average only about 18 cm, or seven inches, in length—are a natural predator of the zebra and quagga mussels that preceded them to North America.
So when the gobies arrived, they found a super-abundance of their favourite food.
But zebra and quagga mussels are filter feeders and, hence, chock full of just about every insidious chemical contaminant that has ever been released into the environment.
So gobies bioaccumulate the toxins and poisons, and then pass them on to any sportfish or person eating them. Not that sportfish populations appear to be denting the goby invasion.
Gobies, you see, are prolific spawners capable of breeding throughout the year. And being staunch nest protectors, they are effective at keeping predators at bay. So their populations are burgeoning.
And if you think the situation can’t possibly get any worse, you’d better think again. Some fish species, such as smallmouth and largemouth bass, relish eating gobies.
So much so that in Lake Erie, the only way anglers are successful these days is by dragging a heavy jig stuffed inside a goby-coloured tube bait along the bottom of the lake.
Of course, it is illegal to use live gobies for bait but the question on many people’s minds is how long it will take for some unscrupulous angler to haul a bucket full of gobies to an inland lake or river (Rainy Lake or Lake of the Woods, for instance) and then dump whatever is left over at the end of the day.
That is precisely how some believe round gobies found their way into two inland Ontario locations—one below the lock at Hastings on the Trent Severn Waterway near Peterborough and the other in the Pefferlaw River south of Highway 48 near Sutton.
As avid anglers well know, the Pefferlaw River flows directly into Lake Simcoe—one of the greatest bass fisheries in the province. The lock at Hastings, on the other hand, is the last barrier to the fish-rich Kawartha chain of lakes.
Sunset Country anglers can count their blessings and hope that round gobies keep their distance. But only time—and good luck—will tell.

Facebooktwitterredditpinterestlinkedinmail