Specialists in aquatic invasive species from the federal Department of Fisheries and Oceans (DFO) and Saint Mary’s University (SMU) announced the discovery of a new invasive species in Three Mile Lake on Thursday.
Near Lower Sackville, N.S., the DFO and SMU experts have found dozens of red swamp crayfish for the first time in Canada.
“We are very concerned because we don’t have native crayfish, so our species here are not accustomed to preying on crayfish. That really changes the dynamics in that food web,” said DFO Aquatic Invasive Species biologist Sarah Kingsbury.
The DFO was first alerted to the new species when a member of a local Facebook fishing group discovered what they thought was a freshwater lobster in the lake back in September 2022.
This summer, Kingsbury said 70 live crayfish have been captured and removed from Three Mile Lake.
“We’re not sure what it will look like overtime,” Kingsbury said. “Clearly the crayfish that we saw last year survived the winter because we’re now finding crayfish here this year.”
The red swamp crayfish — also known as crawfish or crawdads — comes from the Gulf Coastal Plain region which includes the southern United States and northern Mexico.
Growing up to 12 centimetres in length, the critters are generalist eaters that will snack on everything from zoo plankton to plants, fish eggs and any type of meat floating in the lake.
These new additions are now competing for the same food as native species.
“They’re highly invasive globally,” said SMU applied science graduate student Madison Bond. “They’re actually in every continent except for Antarctica. They’ve been spread through the pet trade and through bait.”
The team of specialists surveyed Third Lake, Three Mile Lake, Powder Mill Lake and the wetlands in between the bodies of water for crayfish and only found them present in Three Mile Lake.
The researchers are now working with federal and provincial partners to weigh different control options.
“This species is extremely plastic,” said Kingsbury. “It morphs easily, it adapts easily, it’s very robust. It’s one of the top 100 global invaders.”
Competing with native species for resources, space and calcium in the water, the crayfish can also alter the physical habitat through burrowing, causing potentially severe impacts on the ecosystem structure.
“This is a cold area for this crayfish to occur, so we don’t know how the temperature regimes or how those change in temperature from climate change will end up impacting the species behaviour and impacts,” Kingsbury said.
Bond will be heading back onto the water in the coming months to work on her thesis exploring the life cycle of the crustaceans and what behavioural patterns are seen in the species when in a Nova Scotian climate.
“They are known for their negative impacts,” said Bond. “So please do not spread them, if you find them please do not take them to another lake.”
Kingsbury warns Nova Scotians not to interact with the crayfish or move them, as they could be accidentally introduced elsewhere.