Jellyfish Sightings Surge at Lac La Pêche in Gatineau Park

A recent encounter with jellyfish at Lac La Pêche in Gatineau Park has raised questions about the presence of these creatures in freshwater lakes. On September 20, 2023, J.P. Le Maitre, an avid outdoorsman, spotted what he initially thought were small jellyfish while canoeing. “I noticed dozens of what I thought looked like tiny little jellyfish,” Le Maitre recalled. Initially skeptical, he was surprised to see them swimming in the lake, which is located in Quebec, Canada.

The following day, Le Maitre confirmed his suspicions as he and a friend paddled through a lake teeming with the jellyfish, which he described as translucent and hazy white, measuring no larger than a quarter or a loonie. “You could not enter the water without swimming through hundreds of them,” he said. This sudden appearance prompted inquiries into the nature and implications of these jellyfish.

The National Capital Commission (NCC), which manages Gatineau Park, identified the jellyfish as Craspedacusta sowerbyi. This species was first documented in Lac La Pêche in 2007, with reports indicating that they are harmless to humans. Nevertheless, the NCC acknowledged that their appearances are “sporadic and short-lived,” with minimal impact on the ecosystem.

Recent research, however, suggests that the claim of being “harmless” may need reevaluation. Beatrix Beisner, a limnologist at L’Université du Québec à Montréal, pointed to recent journal articles that detail cases of jellyfish stings. One case from this year involved a woman in France who experienced a painful sting while retrieving her dog from a lake inhabited by jellyfish. In another incident documented in Argentina, multiple cases of jellyfish envenomation were noted.

Experts attribute the increasing sightings of freshwater jellyfish to rising lake temperatures, a change linked to climate change. Beisner has observed that warmer water encourages the jellyfish to enter their “medusa” phase, where they reproduce sexually. “We are seeing more sightings, and I think it is because of climate change,” Beisner stated. She noted that lakes are frequently reaching temperatures above 25 degrees Celsius, which appears to be critical for jellyfish blooms.

The NCC has urged visitors to Gatineau Park to thoroughly clean their watercraft to prevent the spread of invasive species. Although Ottawa Riverkeeper does not currently classify freshwater jellyfish among its top invasive species of concern, the organization acknowledges that their continued spread could pose environmental challenges. Director Larissa Holman emphasized the need for awareness regarding the introduction of any invasive species.

While the jellyfish may not yet significantly impact local ecosystems, the potential for increased competition for resources is a concern. Juvenile fish, which share similar feeding habits, could be affected if jellyfish blooms overlap with their feeding seasons. Beisner pointed out that the jellyfish might pose a threat to these young fish, even if no direct observations of predation have been confirmed.

Le Maitre himself remains cautious about the jellyfish’s potential effects. On that day in Lac La Pêche, he refrained from swimming, uncertain about the jellyfish’s nature. “I had no idea if it was anything potentially toxic,” he reflected. Despite the eerie experience, he found it fascinating and struggled to convince friends of his encounter.

As sightings of Craspedacusta sowerbyi continue to rise, the phenomenon serves as a reminder of the dynamic and sometimes unpredictable nature of freshwater ecosystems. The increasing frequency of jellyfish blooms may warrant closer monitoring as researchers continue to study their impact on local wildlife and water quality.