(Courtesy of the University of Windsor)
The first time she saw a group of male round gobies in their nests, pumping out billows of pheromones to attract females to lay their eggs, Lynda Corkum couldn’t help but think of an old boy’s club.
“It reminded me of a bunch of men, sitting in a crowded room smoking cigars,” the University of Windsor biologist joked.
It’s a simple metaphor to describe a complicated process, but an apt one nonetheless. Round gobies, a small, but very aggressive invasive species of fish invaded the Great Lakes in 1990 when they were transported here in the ballast tanks of ocean-going freighters from the Black Sea. Their numbers are now in the billions and they threaten to decimate native species such as walleye and trout and do serious damage to the multi-million dollar sport fishing industry here.
Bottom-dwelling male gobies occupy crevices and nest anywhere they can find enclosed places – even in the artificial reefs formed by the hundreds of ship wrecks in the Great Lakes – and send out plumes of pheromones to entice females to come in and lay their eggs for fertilization. Pheromones include hormone-like molecules that send signals to animals of the same species.
Corkum is part of a strategic group of scientists examining methods of trapping gobies to slow down their alarmingly rapid spread. The group includes UWindsor chemist Stephen Loeb, Ontario Ministry of Natural Resources scientist Tim Johnson, UWindsor biologists Dennis Higgs and principal investigator Barb Zielinski and Keith Tierney, formerly a post doc at UWindsor and now a faculty member at the University of Alberta.
“The idea is to use a multi-disciplinary collaborative approach to protect the spawning grounds of particular types of game fish,” said Zielinski.
Loeb, a Canada Research Chair in supramolecular chemistry and functional materials, was brought on board for his expertise in chemical structures. The group will identify the chemical structure of the goby’s pheromone and monitor its concentration in water in order to recreate it and incorporate it into traps that will be used to lure females.
Those traps will include recordings of underwater mating calls emitted by male gobies. Higgs recorded those sounds and developed a trap with an underwater speaker to play them back, but said the sound alone is not enough to lure females. Using a multi-sensory combination of pheromones and recorded mating calls may be the best approach, the group believes.
“We’ll never get rid of all of the gobies, but this could be an effective way to control their population and slow their spread into inland rivers and streams,” said Higgs.
At last count, there were more than 9 billion gobies just in the western basin of Lake Erie. The gobies feed on the eggs of fish such as lake sturgeon – which conservation managers are currently trying to restock in the Detroit River – while aggressively protecting their own eggs from other predators. Several females can lay up to 10,000 eggs at a time in one nest and unlike other species which typically spawn only once a year, they will spawn repeatedly throughout their mating season.
And because they’re bottom-feeders, gobies compound the problem by transferring contaminants they’ve consumed from the lake’s floor up the food chain and into other fish that feed on them, Corkum said.
“The round goby has become a dominant species in the Great Lakes,” said Zielinski. “This invasion threatens the recreational fishing industry and the survival of indigenous fish. The damage will continue to spread unless we develop a targeted approach for biological control in specific sensitive locations.”