Bacteria toxic to fish blamed for deaths of catfish

More dead catfish than usual are washing up on the banks of the Ottawa River east of the city, prompting the Ottawa Riverkeepers to monitor what it believes is higher bacteria levels in some parts of the river.

Reports have been received by the group from around Hawkesbury, 110 kilometres east of Ottawa, that there have been more dead fish than in an average year.

Mike Gasher, whose house backs onto the river near Hawkesbury, said that he returned home after some time away and found “quite a few ” (carcasses) along the shore. I think my neighbour counted eight or nine.

“It’s just a nuisance,” he said. “When they wash up on the shore they really smell.”

The riverkeepers said that the organization is monitoring the situation.

“We have received calls about a larger-than-average number of fish deaths, mostly catfish, in the Ottawa River near Hawkesbury in the surrounding areas,” said Larissa Holman, river-watch coordinator with the group.

“We think the fish are likely being killed due to the presence of columnaris, a naturally occurring bacteria that tends to proliferate in warmer weather.”

In 2006, the Ministry of Natural Resources believed that it was columnaris that killed hundreds of fish in the river. It poses no risk to humans, but can be deadly for various species of fish.

Catfish like to hang out in bays and in shallow areas to feed, so they’re going to be affected because columnaris grows well in those areas, Holman said.

While officials with the Ministry of Natural Resources and Forestry said that they are aware of the reports of dead catfish and are keeping an eye on the situation, they are not too concerned at this point, but said if more reports come in further investigation may be required.

“We did talk with the Ottawa Riverkeepers, and we understand that the die-off isn’t widespread or big, so there are no plans to attend the site at this time,” said Jolanta Kowalski, senior media relations officer with the ministry.

Officials with the Rideau Valley Conservation Authority said that while water levels had been slightly lower than average in the Rideau River, they were not aware of any reports of fish-death trends. Data from the Ottawa River Regulation Planning Board shows that water levels in the Ottawa area are close to the average recorded since documentation began in 1965.

While these reports are no cause for alarm, for either humans or catfish, columnaris has been associated with the wider challenges facing Ontario rivers as the impacts of climate change continue to grow.

In a 2011 report prepared for Natural Resources Canada called Fish, Fisheries, and Water Resources: Adapting to Ontario’s Changing Climate, researchers from Queen’s University and Mississippi Valley Conservation noted that as water temperatures rise, Ontario rivers could “expect outbreaks/fish deaths associated with toxic-producing strains of bacteria such as columnaris.”

Fish deaths have the potential to spike in late summer as warm weather and lower water levels pose a threat to some fish species, and those are the indicators that officials monitor.

Holman said it’s important to emphasize that columnaris is no threat to humans, and that any reports of fish deaths should not be taken as a sign that the river is unsafe.

“The Ottawa River is a great freshwater resource,” she said. “It’s a healthy river that people should feel comfortable taking advantage of.”

The Ottawa River, the secondlargest river in Eastern Canada, extends 1,271 kilometres with a 34.6-million-acre watershed, according to the riverkeepers website.