Scientists race to prevent extinction of Atlantic whitefish in Nova Scotia

There are now so few endangered Atlantic whitefish alive in Nova Scotia that researchers are capturing every juvenile they can find this year and whisking them from the wild to a federal fish hatchery for safekeeping.

It's part of the latest effort by the Department of Fisheries and Oceans to prevent what is widely seen as the looming extinction of this ancient relative of the Atlantic salmon.

The good news is that juvenile Atlantic whitefish are being seen in their last refuge in the Petite Rivière watershed near Bridgewater, N.S. No adults have been seen since 2014.

"That was one of the big questions starting out this year — we didn't know if the fish were extinct here yet," said Jeremy Broome, a federal biologist assigned to the whitefish recovery effort.

The capture of 19 juvenile whitefish this week is proof that at least some adults have survived to spawn.

Why the species is in trouble

Like salmon, Atlantic whitefish are anadromous — they spawn in freshwater and migrate to the sea, where they live much of their lives. Or they used to.

The damming of rivers, acid rain and poaching is blamed for their extirpation from their other known locations, the Tusket and Annis rivers in southern Nova Scotia.

Today, the three landlocked lakes that make up the Petite Rivière watershed are home to the last remaining population in the world.

Invasive predators, namely the smallmouth bass and chain pickerel — introduced by anglers — have now overrun two of the lakes and threaten to finish the whitefish.

DFO's 'temporary storage' solution

Every day this week, Broome and members of the Bluenose Coastal Action Foundation have checked traps installed in the 16-square-kilometre Petite ​Rivière watershed, consisting of Hebb, Milipsigate and Minamkeak lakes.

The researchers are looking for whitefish that are a week or two old and measure just 2½ centimetres long.

For the first time, the captured juveniles are being transported in an aerated cooler to the DFO biodiversity centre in Coldbrook, N.S., for "temporary storage." 

The department is looking for a permanent relocation site in the wild, which has proven difficult.

"Invasives are all over this province," said Broome. "It's getting harder and harder each year to find a place that would be invasive-free, and very frankly, we don't have a location for them just yet. We are working on that," he said.

'Renewed effort' from DFO 

Andy Breen is heartened by what he calls DFO's "renewed effort" this year, which includes installing two more fish traps and the decision to remove the larval fish for safekeeping.

Breen is the project co-ordinator for the Bluenose Coastal Action Foundation, which has been contracted for many years to carry out much of DFO's hands-on work, including installing the fish traps and recording data.

As a listed species-at-risk, the department is legally obligated to develop and implement a recovery strategy for the Atlantic whitefish.

The outlook, however, remains bleak.

"We haven't seen any adults. We do get these larval whitefish in a two-week window during May, but we never see many. We've had less than 100 in the last four years. Things are not looking good and this is the only location in the world for them," said Breen.

Breen has the sad distinction of being the last person to see adult whitefish in 2014. 

About 50 of the silver-sided fish were feeding at the surface behind a small dam at Milipsigate Lake.

The safe haven that wasn't

Years ago, DFO thought they had found a safe haven for the Atlantic whitefish at Anderson Lake on military property next to Magazine Hill in Dartmouth. The lake was free of bass and pickerel.

Between 2005 and 2012, large numbers of Atlantic whitefish reared in a captive-breeding program were put into the lake. 

Some grew to sexual maturity, but did not reproduce — or if they did, the eggs did not make it. The fish starved, were eaten or died of old age.

Anderson Lake did not produce a self-sustaining population.

The Harper government, however, used the existence of Anderson Lake to justify its 2012 decision to shut down the Atlantic whitefish captive-breeding program.

Hundred of adults were dumped in Anderson Lake when the breeding program shut down, but none survived.

Chain pickerel showed up in the Petite Rivière watershed shortly after the program was cancelled and the hatchery was dismantled.

Will captive-breeding program return?

Although 20 tiny whitefish are now swimming in a tank at its hatchery in Coldbrook, the Department of Fisheries has not committed to restarting the captive breeding program shut down by the previous government.

"We currently do not have approval for captive breeding. It's not off the table. It's being considered, but as of now we have approval for a translocation approach," said Broome.

He admits time is running out.

"If we were catching hundreds of juveniles, I would say we would have more time," said Broome.

Asked if an extinction is underway, Broome said "it's a real possibility that could happen within the next number of years."