WHITE SHARKS IN CANADA
Following the seasonal journeys of the North Atlantic’s most iconic predator.PART 2Why Come North?
What draws North Atlantic white sharks back to Canadian waters year after year
A white shark entering Canadian waters has not crossed into a separate life. It has moved into the northern end of a range that can stretch from Atlantic Canada to the subtropical waters of the southeastern United States and the Gulf of Mexico.
The question “Why come north?” sounds as if it should have one clean answer. Food. Temperature. Instinct. In reality, each is part of a moving equation—and different sharks may solve it differently.
Canada’s 2025 recovery strategy describes Atlantic Canadian waters as the northern extent of the Northwest Atlantic population’s distribution. Only a portion of that broader population enters Canadian waters in a given year, mainly in summer and fall. They are not Canadian residents in the ordinary sense. They are seasonal participants in an ocean-scale system.
The ocean changes, and the sharks move with it.
Historical records and modern telemetry describe a broad annual rhythm. In spring, white shark occurrence expands northward along the continental shelf. Sharks remain at northern latitudes through summer and into fall. By November and December, the distribution begins shifting south.
That pattern is real, but it is not a timetable followed identically by every animal. Migration timing varies among years and among individuals. Some sharks remain coastal; others travel offshore. Some return to familiar seasonal areas, while others appear to use different strategies.
Generalized movement pattern—not a prediction for an individual shark.
Prey helps explain the journey. It does not reduce it to seals.
Large white sharks are capable predators and scavengers of marine mammals. Atlantic Canada holds major grey seal colonies, and Canadian recovery documents identify the presence of seal rookeries as one possible influence on white shark distribution.
But the simple story—“sharks come north because there are seals”—breaks down under scrutiny. Long-term acoustic monitoring near Sable Island has produced surprisingly little evidence of tagged white sharks at that enormous seal breeding colony. In summer, seals redistribute among many smaller feeding areas. Sharks may be following a dispersed prey field rather than converging on one obvious colony.
Age matters too. Juvenile white sharks are predominantly fish and squid eaters and have not yet reached a size that makes seals an efficient target. Their Canadian movements may be tied to pelagic and bottom-dwelling fishes, squid, coastal productivity, and the opportunity to forage with less competition.
Warm enough is not the same as temperature explains everything.
White sharks can retain metabolic heat and tolerate a wide range of conditions, but the northern edge of their range is still seasonal. Summer warming makes Canadian shelf waters more accessible, while winter cooling helps close that seasonal window.
In the largest Canadian-focused tagging analysis to date, sharks in Canadian waters experienced a more restricted temperature range and used proportionately less of the water column than elsewhere. From June through November, satellite-tagged sharks were mainly in coastal locations inside the 200-metre depth contour and generally used the upper 100 metres.
The researchers also cautioned against treating one preferred temperature as a universal switch. Temperature interacts with prey, bathymetry, life stage, behaviour, and the energetic cost of reaching distant habitat. It defines opportunity; it does not act alone.
Study summary for June–November; not a physiological limit.
The sharks most likely to come north are not necessarily the largest.
Analysis of tagging data from 2010–2020 found that juveniles were 4.7 times more likely than adults to move into Canadian waters; subadults were 3.4 times more likely. That makes the northern range edge a selective habitat used disproportionately by particular life stages.
One explanation is that younger sharks disperse more widely through suitable coastal habitat while searching for abundant fish and squid. Adults may have other energetic priorities, established seasonal destinations, or movement strategies that take them elsewhere.
RELATIVE LIKELIHOOD OF NORTHWARD MOVEMENT
A seasonal habitat can still be essential habitat.
Only a small and highly variable component of the tagged Northwest Atlantic population was detected in Canada each year. That does not make Canadian waters incidental. It means their role must be understood at the scale of an annual life.
A shark may feed in Nova Scotia, cross international boundaries during migration, overwinter far to the south, and encounter fishing gear in another jurisdiction. Protection in one place cannot compensate completely for mortality in another.
This is why the distinction at the heart of this series matters: they do not live in Canada. They return to Canada. The return tells us that seasonal Canadian habitat provides something worth crossing an ocean corridor to reach—sometimes repeatedly, and not always for the same reason.
Canada is not the whole story of these sharks. It is one indispensable chapter in a life written across the Northwest Atlantic.