Seeking a safe place for one of Canada's most endangered freshwater fish
CBC
The effort to save one of Canada's most endangered freshwater fish now involves electronic tracking of specimens bred in captivity and released into the Nova Scotia watershed that holds the world's only remaining wild population.
Last week, a final batch of 30 tagged Atlantic whitefish were released in the Petite Rivière system behind the town of Bridgewater on the province's South Shore.
"We have released fish into different parts of the system, the lake portion, riverine portion and as well into the estuary into salt water," said Jeremy Broome, a biologist with Fisheries and Oceans Canada assigned to the recovery team.
"So looking at which one of those might produce the best survival is important to us."
Tiny transponder tags were inserted with a hypodermic needle into 150 one-year-old fish spawned at the Dalhousie University Aquatron marine research facility in Halifax.
The fish were anesthetized, given one week to recover and released at various locations within the watershed. Fish were released into the estuary after acclimatizing to saltwater.
Devices installed at narrow points along the river system will send a signal when a tagged fish swims by.
"We are trialling different approaches, sort of spreading our eggs across different baskets to see what might work best," Broome said.
"If we can determine that survival is better with releases into the estuary, we're seeing more fish come back from that strategy that would be indicative that we would want to proceed with that approach."
This whitefish species is an ancient relative of Atlantic salmon and naturally anadromous, meaning they're born in freshwater, travel to the ocean and return to spawn.
They have survived only in the Petite Rivière watershed, which was landlocked for a century by a dam and serves as the water supply for the Town of Bridgewater.
A fish ladder was built there in 2012.
The recovery team hopes to see evidence that 1,100 untagged juveniles released last year and those tagged in 2023 return to spawn in the next year or two.
Nearly 40 years ago, the species was the first fish in Canada to be assessed as endangered by the Committee on the Status of Endangered Wildlife.
