Chronicle Herald

Scientists taking ‘holistic approach’ to Atlantic salmon sea survival question

Aaron Beswick

May 9, 2019
“20 seconds … ten …” whispered Kevyn Janisse.

“… go.”

With that Christina Semeniuk, a biology professor from the University of Windsor, crawled through the mud of the floorless tent perched on a bank of Sheet Harbour’s West River. Keeping her head low, she lifted the plastic cormorant decoy over the plywood side of the aquarium and dipped its plastic beak into the water.

She repeated the manoeuvre for the other two aquariums and scurried out again on all fours.

She did this all in the hope of terrifying a few baby salmon that got themselves caught up in a scientific experiment on their way to the sea.

The hypothesis of the scientists working by the river is that salmon are just like us: Where they come from informs who they are.

That affects how they behave when they leave their rivers for the big wide world and, ultimately, whether they make it home.

“It’s not just the amount of smolts heading out a river, it’s their health,” said Edmund Halfyard, a research scientist with the Nova Scotia Salmon Association.

“We’re taking a holistic approach and linking their health to how they behave and at-sea survival.”

Acid, lime, and a laboured heart

The waters of the rivers had been polluted by decades of acid rain from North America’s manufacturing heartland during the boom years of the 1950s and ’60s.

The Clean Air Act of 1990 mitigated that and along most of North America’s eastern seaboard, the droplets of water feeding the rivers became less toxic to life.

“Most” being the critical term, because on the glacially stripped stone shoulders of the Eastern and South Shores along with the Maine coast, the damage was done. They lack the soil to further buffer any more damage.

The salmon have stopped coming back to most of the area’s rivers.

The few that survive two and a half years in the rivers head out to the Atlantic with gills resembling the lungs of lifelong smoker. Their bones are weaker because they struggle to produce calcium. Their hearts have had to beat harder, burning more energy.

When they started counting salmon smolts heading out of the river through the mid 2000s, estimates suggested 3,300 of the juveniles were making it to the sea.

“The West River, Sheet Harbour, became a demonstration river for acid rain mitigation through the entire area,” said Halfyard.

In 2005, a lime douser was installed in the river to lower the water’s acidity. They added a second on another tributary in 2017 and have begun helicopter liming areas of the watershed.

Now over 10,000 baby salmon survive to head out to sea each spring. But despite this, fewer than 100 return each year to spawn.

“We don’t know why,” said Halfyard.

In fact, no-one knows why at-sea survival has plunged since the early 1990s for salmon from all rivers on the eastern seaboard.

Many are trying to figure that one out.

Getting ready for release

This team of scientists from the Nova Scotia Salmon Association, the Atlantic Salmon Federation, Dalhousie University, the Ocean Tracking Network, The University of Windsor and Fisheries and Oceans Canada, are focusing on how a healthy river leads to healthy smolts and how healthy smolts behave in the wild.

The smolts heading to sea are collected at two points — one from a portion of the river that is treated with lime and one that isn’t.

They go into aquariums in the first tent for a personality test.

Their behaviour is monitored and they’re given a score for how much they move around and whether they eat when fed. Then comes Semeniuk with her plastic cormorant — a major predator for smolts on the Eastern Shore. They are monitored via GoPro cameras to see if they hide. They’re given time to calm down and then they’re fed again to see if they come out to eat.

The smolts then go the second tent where a swab of their gills is taken to test for the presence of enzymes symptomatic of their bodies preparing to deal with the salt water waiting a few kilometres downstream.

Then it’s a dip in an anesthetic bath and a two-centimetre-long acoustic transmitter is inserted into their bodies before they are stitched up and returned to the river.

Lines of receivers in the open water belonging to the Ocean Tracking Network will detect where they go. The information will be combined with the physical and personality checkup they got at Halfyard’s tents.

The research is ongoing and a published paper won’t be coming until well after the last hope of receiving pings from the transmitters, which have a 200 day battery life, has passed.

“But we are seeing a significant difference between the smolts that came from the area that had received acid mitigation measures and those from the other area,” said Semeniuk.

A day earlier, Federal Fisheries Minister Jonathan Wilkinson was visiting the headquarters of the St. Mary’s River Association to announce $1.8 million in funding to expand work like what’s been done on the West River.

The plan is to expand liming along the West River and to start it on the St. Mary’s.

The money will also go toward river restoration efforts both organizations have been working at for years — creating deep pools for salmon to rest and cool down in when they make their journeys back upriver to spawn.

Both rivers have seen decades of work by volunteers already.

And along both, the work of restoration and of learning has been fueled by hope that we can undo some of the damage done.

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