As the Gulf of St. Lawrence warms, whales are changing menus and may share lunch

As the waters of the Gulf of St. Lawrence warm, new canadian research There is suggestion that the diet of some baleen whales is changing. And that’s because the menu is changing, too.

There has been a decline in Arctic krill, “which was a particularly important prey for fin whales in the 1990s,” said lead author Charlotte Tessier-Larivière of the Maurice Lamontagne Institute at Fisheries and Oceans Canada.

Their new research shows that fin and minke whales have shifted to eating more forage fish such as capelin, mackerel and herring – the primary diet of humpbacks in the area.

“Our study shows “Whale species are able to adjust their diets according to the varying availability of preferred prey,” Tessier-Lariviere told CBC News via email. “This is positive because it shows a certain ability to adapt – but we don’t know the full extent of their adaptability.”

And that raises a question: If they’re all eating the same type of fish, are there enough fish to go around? And what will happen if these prey species decline?

Hannah Wachter, campaigner for advocacy group Oceana, says that while she finds it encouraging that the study shows that some whale species are adapting, the results are also “troubling”.

“I think it confirms what scientists have been seeing in the Gulf for some time, and that is that the ocean is changing, climate change is having a real impact on our oceans, and many marine life from large whales to small bait fish are responding to those changes in real time.”

what are you eating

Sample taken in studyLeases were obtained from the tissues of each whale species as well as the tissues of their prey during the summer months for 28 years. Those samples were analyzed for C.Carbon and nitrogen isotopes, which are telltale signatures of diet.

Tessier-Lariviere says that as the whales eat, “the composition of the prey will be metabolized and incorporated into the tissues,” allowing researchers to know who is eating how much.

In the years following the study, signatures of more forage fish were found in the tissues of all three whale species.

What the whales are eating is “really important in the food web,” Watcher explained, calling those forage fish the backbone of these ecosystems.

smart sharing

But the study also found that despite signs that fin, minke and humpback whales were eating the same food, they were not stealing from each other. Instead, there were signs of “resource partitioning”, which occurs when there is limited supply.

The whales were eating from the same pools of fish, but the study indicated less overlap between whales in recent years, indicating they may be eating those fish at different times or places.

“They are highly intelligent creatures,” says Jenny Ray, CEO of BC Whales and North Coast Cetacean Society. “Even from year to year, there can be fluctuations with respect to prey availability for them. So they need to adapt.”

Ray led recent paper Humpback focused on practice of bubble net feeding by WHALace – a complex technique where whales release air bubbles into the water which they can use as a net or curtain to focus their prey, making it easier to hunt.

And he has observed cooperation between humpbacks and fin whalesWhen it comes to food on the West Coast, too.

“We’ve certainly seen that they may be foraging in the same area, somewhat dispersed from each other, but they may also be foraging at different depths,” Ray told CBC News from Alert Bay, B.C.

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Ray says the whales will try to adapt to changing conditions – learning new hunting techniques, as his team observed. She points to the recovery and survival of humpback whales in the Pacific after their numbers declined due to commercial whaling in the 20th century.

She says it’s important to study their habits and use that information to accurately identify which marine areas need to be protected.

“There seem to be certain areas where you see larger concentrations of whales more than other areas. So there’s something very valuable about that area,” Ray said.

Once they know an area is a whale hotspot, she says, they can work to protect it. “Because the whales themselves are telling us, ‘This is home, this place is important to us.’ “

The area studied in the St. Lawrence whale paper was not in a marine protected area, although existing protected areas exist in the depths of the St. Lawrence. also have plans to expand current fields.

Wachter says Canada needs to be “dynamic” when it comes to protected areas, noting that the whales themselves are adapting their habits.

“Safeguarding whales and protecting marine habitat in the future will depend on climate-informed adaptive management that looks not only at where whales have been historically, but where their food is going based on models and climate projections,” he said.