This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For decades, the round goby has been one of the Great Lakes' most destructive invasive species. Scientists estimate its population numbers in the billions, making eradication unrealistic.
But new U of T Scarborough research suggests the fight against the invasive fish is far from over. In a new study published in the Journal of Great Lakes Research, postdoctoral researcher Piatã Marques and Professor Nick Mandrak suggest governments and conservation agencies should rethink how they manage round goby as the fish expands beyond the Great Lakes into rivers, streams, lakes and other inland waterways. "The Great Lakes are essentially lost when it comes to round goby," says Mandrak.
"They're established throughout the lakes, they number in the billions, and we're never going to fully remove them from those systems. Now we're seeing them move into connected and isolated waters where we still have a chance to slow or even stop their spread." Their research shows the fish spreads more slowly through smaller waterways, creating an opportunity to contain or eliminate local populations before they become a problem. Originally native to the Black and Caspian seas, round goby arrived in the Great Lakes in the early 1990s in cargo ships' ballast.
Since then, they have spread throughout all five Great Lakes, where they compete aggressively with native fish for food and habitat, consume fish eggs and young, and alter aquatic food webs. Despite measuring about the length of a smartphone, round goby have an outsized impact on freshwater ecosystems. Their aggressive behavior, voracious appetite and ability to thrive in a wide range of conditions have helped them multiply into the billions.
Marques says the invasion has now entered a new phase. "Over roughly the last 15 years, we've started seeing round goby moving upstream into inland waters, including rivers, streams and ponds," he says. "These freshwater systems contain some of Ontario's richest biodiversity, including endangered species, so this is an area of concern." Among the species potentially at risk is the redside dace, an endangered fish that inhabits streams across the GTA.
Researchers worry round goby could outcompete this and other native fish for food and further disrupt inland freshwater ecosystems. Using more than two decades of GTA river monitoring data from local conservation agencies, Marques and Mandrak found round goby advances only a fraction of a kilometer to about two kilometers (1.2 miles) per year, providing a window for intervention before populations explode. Rivers and streams are smaller and more accessible than the Great Lakes, making targeted management more practical.
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