Imagine standing in the shallows of your lake and peering down at your feet through the water. If you were to trace a one square metre box around your feet and fill it with 100 small fish, that, says Steven Cooke, a professor and conservation researcher in Carleton University’s Biology Department, would equal the devastatingly invasive force of the round goby.
Native to the Black Sea and the Caspian Sea, the round goby, a small, bottom-dwelling fish, was recently discovered near Smiths Falls in the Rideau Canal. The round goby was found around last November by an environmental consulting firm hired by Parks Canada to salvage fish from a lock along the Rideau Canal.
“They were doing some infrastructure work in the lock over the winter, so they had to dewater the lock,” Cooke says. “Any time you dewater things, you send in a crew to collect the fish so the fish don’t die. Then they would normally release them upstream or downstream from the lock.” As the firm was going through the contents of the lock, catching fish, they came across 17 round goby.
Cooke surmises that the round goby found its way into the Rideau Canal via humans. “The two most likely [theories] would be a bait-bucket transfer. So, someone goes fishing…they were using goby as bait and they didn’t want to kill them, so they just let them go thinking they were being kind to the fish,” he says. “Or alternatively, it was from ballast water in boats. Often times when we think of ballast water, we think of a big lake ferry or major transport vessels for oil and grains and coal and so on. But some of the higher end and larger yachts and ski boats also have ballast water.”
The round goby has already established itself in the Great Lakes and the Trent Severn system. Cooke says he’s worried it may already be too late for the Rideau Canal as well. “By the point in time where we can catch them in reasonable number, it’s too late for trying to eradicate them. Fish eradication, especially in riverine systems, are almost impossible to achieve.”
Cooke’s research team has a $600,000 grant from the federal government to study how fish, plants, turtles, water, and nutrients move through the Rideau Canal system. A major subsection of this is observing how invasive and endemic fish move through the canal system. When Cooke heard about the round goby, he saw it as an opportunity to expand their research. His team has since caught and tagged 50 round gobies with tiny electronic transmitters. “The idea is if we can figure out when they move and how they move, then that might give us some opportunities to prevent or slow their spread,” he says.
The reason round gobies are so threatening to the local ecosystem is because they displace native creatures like crayfish, darters, and log perch. Cooke adds that while these creatures aren’t of particular concern to anglers and recreational fishermen, they form the “foundation of food webs and are eaten by things like bass and pike that people do care about.”
The round goby is also a voracious nest predator. They stay near the floor of waterbodies, attacking the nests of species like the small-mouth bass and the large-mouth bass. The bass already have to defend their nests from predators like bluegill, pumpkinseed, and yellow perch. “Then, all of a sudden you introduce a new hyper-abundant nest predator, and it creates a lot more work for the [bass] and he has to expend a lot more energy,” Cooke says.
Due to its abundant nature, the round goby is out-competing species like darters and log perch, and, as a result, eliminating them. The issue with this, Cooke says, is if “10 years from now, a disease comes through and wipes out all of the goby, well, there’s nothing now in that part of the food web.” By becoming the dominant species, the round goby is making the entire ecosystem less resilient.
On the plus side, small-mouth bass have begun to see the round goby as prey, gobbling up hundreds. Their vast number have caused the small-mouth bass to grow to unprecedented sizes. “In the St. Lawrence now, they’re catching gigantic fish, and that’s been attributed largely to the round goby,” Cooke says. That is, as long as the small-mouth bass doesn’t fall prey to the round goby during its egg or baby stage.
In order to prevent the spread of invasive fish like the round goby, Cooke stresses how important it is not to move them. “In Ontario, you’re not allowed to release bait fish,” he says. Even if you bought the bait fish at a store, it’s illegal to throw them into a lake at the end of the day.
He also advises boaters to be extra cautious when transferring their boat between lakes, especially if the boat carries ballast. This can help spread invasive species to disconnected lakes. “Anything we can do to stop the spread, to essentially make sure what’s happened in Smiths Falls does not happen elsewhere,” Cooke says.