February 04, 2015

Pond drainage needed for Round Goby eradication

As published in The Erin Advocate

The Round Gobies of Hillsburgh have caused quite a stir among fisheries biologists and may soon find out just how unwelcome they in the Credit River watershed.

The Ministry of Natural Resources and Forestry (MNRF) considers the problem so severe that they have a plan to apply piscicide – a poison that would kill off every gill-breathing animal in six ponds and a short section of the West Credit River near Hillsburgh.

If the plan goes ahead this spring, they would draw down the water levels and use electrofishing to stun and capture quantities of desirable fish, which could be returned to the water once the poison is gone. Lower pond levels would allow the operation to be done with less of the chemical, called Rotenone.

Round Goby (neogobius melanstromus) arrived in the Great Lakes about 25 years ago, thanks to ships from the Black Sea. In 2013 some were dumped in Hillsburgh, probably from a bait bucket.

Since then they’ve been doing what comes naturally – feeding aggressively on diverse aquatic food supplies and spawning several times a year. Their ability to dominate the local environment qualifies them as an Invasive Species.

Since they became established in Lake Erie they have eliminated nearly all of the small bottom dwelling fish, such as darters and sculpins, which were once found there. They’ve also caused significant damage to the nests of Smallmouth Bass by consuming their eggs and young. They like to feed on zebra mussles, another invasive species.

They have advantages over some other fish, since they are able to survive in lower-quality water and have a sensory system that helps them gather food more aggressively.

At a public meeting last fall at the Hillsburgh Fire Hall, MNRF said if the Round Goby is not “controlled”, it is a major threat to native fish, including Brook Trout and other salmonids.

According to their presentation, “Downstream movement of goby to more suitable habitats could negatively impact the fish community of an additional 80+ km of the Credit River, which contains recreationally and economically important fisheries.”

MNRF had hoped to carry out the eradication last fall. It is now planned for the spring, but a final decision has not been made. They have promised to keep the community informed.

“MNRF will continue to work with landowners to secure permission to access properties for monitoring and treatment,” said Management Biologist Art Timmerman, in a letter sent to residents and Town Council.

Rotenone is the only registered piscicide in Canada, to be used as a “fisheries management tool”. It is a natural substance extracted from the roots of tropical plants, and only affects gill breathers.

MRNF says there will be no accumulation in the aquatic environment, no effect on birds or other wildlife and no threat to public health. They said this preferred option is “safe and effective, with immediate results at moderate cost.” Dead fish would have to be collected before the ponds are refilled.

Rotenone breaks down quickly in the water. All residue would be gone in one to four weeks, and oxidizing agents could be added to neutralize any downstream impact, MNRF says.

Round gobies have not been found upstream or downstream from Hillsburgh, probably because they prefer the relatively warm environment of the ponds, but once their population increases, they are likely to spread.

The ponds could be restored to their pre-treatment levels and restocked with native fish, depending on the preferences of the landowners.

The long-term future of the main Hillsburgh pond and the Station Street dam are currently being studied in an Environmental Assessment.