Billions of invasive round goby are in the Great Lakes. Researchers want to stop them from spreading inland

The round goby, an invasive fish species, has devastated the Great Lakes for decades. Scientists estimate its population to be in the billions, making eradication virtually impossible. However, a new study from the University of Toronto Scarborough suggests that the fight against the round goby is not yet lost. Researchers argue that the fish is now spreading beyond the Great Lakes into inland waterways, rivers, streams and lakes, where there is still a chance to curb its population growth.

Professor Nick Mandrak, who co-authored the study published in the Journal of Great Lakes Research, states that the Great Lakes are effectively lost to the round goby, as the species is now established throughout the system. However, the researchers believe that there is still time to manage the fish's spread into inland waterways, where it has begun to move upstream over the last 15 years.

The rate of expansion is relatively slow, averaging about 0.2–2 kilometers per year, providing an opportunity for intervention before the populations increase significantly.

The study, led by postdoctoral researcher Piatã Marques, emphasizes that the round goby's invasion is in a new phase, with the fish now moving into inland waters, including freshwater systems that are home to diverse and endangered species, such as the redside dace. Researchers are concerned that the round goby could outcompete these native fish for resources, further disrupting the inland freshwater ecosystems.

To manage the spread of the round goby, researchers propose a combination of methods tailored to smaller waterways, such as trapping, electrofishing, physical barriers, and rapid-response programs. These targeted approaches are more feasible in rivers and streams than in the vast Great Lakes. The researchers also suggest using environmental DNA (eDNA) monitoring to detect the presence of round gobies even when they are difficult to capture.

The team is currently studying various aspects of the round goby's behavior and adaptability, including its diet, competition with native species, how urbanization aids its upstream movement, and why it can successfully colonize new freshwater systems. By understanding the fish's characteristics and ecology, scientists hope to develop more effective control strategies and provide practical guidance for resource managers.

The ultimate goal is to protect the inland ecosystems, especially those containing endangered species, by acting before the round goby becomes established in these areas.