Project contributes to high returns of endangered salmon
A multi-disciplinary and collaborative research project at Memorial University has contributed to 25-year high returns of the endangered Inner Bay of Fundy Atlantic salmon to Fundy National Park (FNP) rivers.
Corey Clarke, a part-time masters student in the environmental science interdisciplinary program at Memorial, is co-supervised by Dr. Craig Purchase at Memorial and Dr. Dylan Fraser at Concordia. The New Brunswick native is a Parks Canada employee planning to formally wrap up his studies in September.
As a park employee, Mr. Clarke had been part of a diverse team for many years that had at been actively trying to figure out how many Atlantic salmon there were left in Fundy and trying to, at the very least, hold on to the remaining population.
“In the early 2000’s the team collected a sample of wild juvenile salmon during their natural spring migration as smolts from park rivers to the Bay of Fundy,” said Mr. Clarke. “Within only a couple years, smolt collections declined to zero, suggesting that adult returns to park rivers in previous years had effectively ceased and that the team had collected a sample from the last remaining salmon in Fundy.”
The live smolt were transported to a captive rearing facility operated by the Department of Fisheries and Oceans (DFO). While at the hatchery, these remnant wild FNP fish were genotyped and eventually spawned in captivity – beginning the sophisticated Live Gene Bank (LGB) program for park salmon stocks. This program ‘banks’ representatives of all families of park stocks in captivity to produce offspring, which are released into park rivers. Smolts continue to be collected each spring to contribute future stock to the LGB, as a sort of ‘life-support’ for the park’s salmon stocks.
Mr. Clarke says after a decade of study, the team repeatedly demonstrated that fish released to park rivers at different juvenile stages did produce smolt migrating to the sea, but failed to return from the Bay of Fundy 18 months later to spawn, as they had up until the late 1980’s when the population crashed.
This is when an innovative project was proposed which aimed to rear a portion of collected smolts in sea cages in the Bay of Fundy where they would naturally live for 18 months before returning to spawn.
“We met with the Atlantic Canada Fish Farmers Association in New Brunswick and a couple of companies came forward right away and said they would rear some for us so we could have adults to work with that were grown at sea in addition to those from the hatchery,” said Mr. Clarke.
In 2010, a portion of smolts were taken from one of the rivers in Fundy National Park and raised in sea cages in southwestern New Brunswick, while a control group were raised as usual in the hatchery. Roughly 18 months later, the adults produced were released inside the Inner Bay of Fundy and tracked for return to park rivers, or they were used in an experiment comparing the survival of offspring from cage reared and hatchery reared parents. The offspring survival project largely became the basis of his masters’ project with Drs. Purchase and Fraser.
“For the tracking project, approximately 300 fish were loaded into the hull of a large lobster boat and steamed from the cage site in Southwestern New Brunswick to the Inner Bay of Fundy and released,” said Clarke. “About 10 per cent of them had acoustic tags to be detected by receivers placed at the mouth of the Park and adjacent rivers should the salmon return.
“Every released fish had a colored tag on the outside that divers could see during surveys and also a small ‘PIT’ tag implanted under the skin when captured as a smolt, about the size of a grain of rice, which you could scan like a bag of chips to get a number. So every fish is permanently identifiable as part of this project.”
That year, according to the acoustic tags and diver surveys, at least a dozen fish returned to the river their river of origin and at least another three-dozen went back to an adjacent park river which was closer to the release site.
“It was very encouraging. We hadn't seen very many returns in the last decade, less than five returning fish most years. We demonstrated that despite a decade of captive rearing assistance, these fish retained some instinct to return to the river, which was good.”
Back at the hatchery, the eggs from the cage-reared fish were surviving better than the eggs from hatchery-reared parents but interestingly, it was how the fish were released to the river as juveniles that seemed to have the most impact on offspring survival. Preliminary results suggest that fish released to the wild just after hatching produced better surviving offspring than those released after 5 months of rearing in the hatchery regardless of where they were reared, sea cage or hatchery, for months between smolt and adult stages.
“I think that’s an interesting result that can be useful for any group considering the use of captive rearing for restoration of salmon populations,” said Mr. Clarke. “The idea is that you want as much wild exposure as possible but perhaps, most importantly, during earliest life stages – although even naturalized captive exposure in later in life stages can have advantages.”
In late fall of 2011, when the spawning experiments and masters’ field work was complete, the team released the remaining fish, reared either in sea cages or the hatchery, back to the mouth of the river they were collected as smolt.
The excitement began in late summer of 2012 during the park’s annual dive surveys. Clarke received a radio call from a diver elsewhere on the river reporting dozens of salmon in a pool he was surveying.
“At first we thought maybe it was just a fluke great return year for wild fish, as that many salmon in a single pool hadn’t been observed in Fundy for decades. The next day we went back to the pool with a seine net and corralled many of the salmon near shore to sample and check them for tags.
“Scanning one at a time, all but one of the 30 fish carried a pit tag proving they were fish released a year earlier. So, a year after we had finished our experiments and released the fish as adults, they came back and with greater success than the release at sea.”
Managers of the park’s salmon recovery program, as well as other salmon conservation groups, are now considering incorporating this type of rearing strategy into future recovery efforts.
“The sea cage is well designed for growing large numbers of adult fish and can be very cost effective compared to the hatchery environment. Its good news for an industry that sometimes battles negative public perception, to have them partnering with conservation efforts, especially those showing signs of success.
“The dedication to this conservation project for an endangered salmon population shown by the industry association, and in particular by the entire Admiral Fish Farms company, our main industry collaborator, was both impressive and key to our success.