A conservation effort to bring Atlantic salmon back to strong levels in Fundy National Park reached a milestone Wednesday.

More than 500 mature inner Bay of Fundy Atlantic salmon were released into two rivers in the park, the result of years of collaboration between the federal and provincial governments, Fort Folly First Nation, the aquaculture industry, the Canadian Rivers Institute and more.

Since 2001, the salmon population has been at risk of being lost in the park as it was noticed that fish leaving the park's rivers weren't coming back from their trip into the Bay of Fundy.

"They leave in the spring and come back the following year as adults to spawn," said Corey Clarke, an ecologist at Fundy National Park. "And the problem with this population is that they fail to return from the marine environment."

hi-salmon-release

Over 500 mature inner Bay of Fundy Atlantic salmon were released into two rivers in Fundy National Park Wednesday. (CBC)

The team developed a unique solution that, from initial trials, seems to be working: they keep some of them from going into the bay, and instead take them at a special site in Grand Manan, called the Wild Conservation Marine Farm.

"This type of program collects a few of them as they leave the river, grows them to adults in captivity with our partners at Cooke Aquaculture, Department of Fisheries and Oceans and other partners, and then we release them back into the river as mature adults," said Clarke.

That's what they did on Wednesday, as the now-mature fish were first trucked to the park, then sent by helicopter in baskets to various spots on the two rivers to be released.

After 15 years working on the program, this is the largest release, and they are on track for another 1,000 next year.

si-atlantic-salmon

The salmon were taken from Fundy National Park as they were leaving the rivers, and raised to maturity at a special aquaculture site on Grand Manan, which only held the wild salmon. (CBC)

The goal is for the next generation to be able to grow to maturity normally.

"The ultimate success is in returning adults," said Clarke. "We want these adults to spawn, produce offspring that survive well, and ideally survive the time out here in the Bay of Fundy to return as adults."

Clarke said they are already seeing encouraging signs in some of the earlier tests, as some of the fish released last year did return to spawn as adults.

The two rivers in the park where they released the salmon would have held about 1,000 fish in the past, so Clarke said putting 500 back into them is a significant step.

With files from Tori Weldon