Trois-Rivières fishing festival cancelled after abrupt death of 1000s of rainbow trout

Fish biologist Pierre Magnan says a lack of oxygen likely caused more than half the trout introduced to a pond last Friday to die suddenly — forcing the municipality to cancel its participation in the annual fishing festival.

The festival is a chance for families to grab their rods and reels and fish for three days without a permit in selected places across Quebec. Last year, the 18th annual event attracted 79,000 participants.

However, this year festivities in Trois-Rivières were brought to an unexpected halt.

Festival organizers filled a pond in Pie-XII Park with 2,000 rainbow trout on Friday, inviting would-be anglers — especially those between nine and 12 years of age — to fish them for free that day and over the weekend.

However, within an hour, nearly all of the trout were afloat belly-up, dead.

Fish might have suffocated

The fish "did not survive their new environment," the City of Trois-Rivières said in a news release issued late in the day, Friday. All the weekend's events had to be cancelled.

Magnan hypothesized that the trout died from a lack of oxygen.  

"It's very important to look at the relationship between the water temperature and the concentration of oxygen," said Magnan, a professor of biology at the Université du Québec à Trois-Rivières (UQATR).

"You can think there is a lot of oxygen, but if the temperature is too high, the fish aren't able to absorb it."

Such mass die-offs are rare, Magnan said, because Quebecers have long mastered the science of stocking fish ponds.

The City of Trois-Rivières is still studying what happened.