Round Goby Threatening Ontario River Ecosystems

September 12, 2009

Release from: Sharon Hill
Windsor Star (Canada)

The invasive round goby has moved into rivers in Southwestern Ontario and could wipe out already rare fish and mussels.

"The ones that are endangered, they're already at the brink," University of Toronto PhD student and researcher Mark Poos said Friday. "The ones that are rare or endangered might actually be doomed."

Poos is the first author on a research paper that talks about the first evidence of the invasion of round goby from the Great Lakes into rivers including the Thames, Ausable, Sydenham and Grand rivers in Ontario.

The research discovered the round goby was eating or out-competing 89 per cent or 17 of 19 bottom-dwelling fish in the rivers.

That includes the threatened eastern sand darter and the endangered madtom.

The round goby was also having a negative impact on 17 per cent of mussels including globally endangered mussels such as the mudpuppy and the northern riffleshell mussels. The goby can eat small mussels and reduce the number of native fish that juvenile mussels use as a host.

The University of Toronto researcher said the Thames River, which joins Lake St. Clair at Lighthouse Cove, has more endangered fish and mussels than anywhere else in Canada.

"Finding round gobies in these spots is a big concern," he said.

The round goby from the Black and Caspian sea region in eastern Europe was first discovered in 1990 in the St. Clair River.

Within five years the round goby had spread through the Great Lakes.

Some scientists didn't expect the lake-dwelling round goby to move into rivers with where the goby would have to compete for food with established species and in spots where their preferred food -- zebra mussels -- were not present, he said.

Instead, within the last five years, researchers found the round goby moving in "at the pretty alarming rate. We started finding round goby in rivers that didn't have them before."

The round goby could not only decrease the population of native fish and mussels, it could help other non-native species invade the rivers too, he said.

Daniel Heath, a geneticist at the Great Lakes Institute for Environmental Research at the University of Windsor, said the travelling gobies are worrying. Heath said a student is looking for the round goby in local rivers and he'd bet they could be here too.

For two years, Heath and Dennis Higgs, a University of Windsor biology professor, have been studying whether the round gobies that head up river are genetically different from the ones in the lakes.

Heath said the move to rivers is troubling for two reasons. The last thing rare species need in a voracious invader and the rivers will take round gobies to other inland lakes.

He said the round goby would wreak havoc in smaller lakes.

The round goby, which reaches about 176 mm in length, is aggressive, has a broad diet, spawns a number of times a year and grows faster than other fish.

Poos said work could be done to try to slow the spread. Research is being done at the University of Windsor on pheromones which could be used to attract and catch the fish, he said.

Anglers should not release round gobies back into the water, should not use them as bait and should not move fish, he said.