The bluntnose sixgill shark, reaching up to 4.8 meters in length, is the largest predatory shark commonly found in Canada’s Pacific waters. It belongs to the family Hexanchidae, also known as cow sharks. The name “sixgill” comes from its six gill slits, unlike most sharks that have only five. This shark stands out with its single dorsal fin, whereas other sharks on Canada’s Pacific coast have two. Its coloration varies from dark brown or grey to black on the dorsal side, lightening towards the underside. It has a broad, depressed head, a blunt snout, and striking bright green eyes.

Bluntnose sixgill sharks are among the most widely distributed shark species, inhabiting continental and insular shelves in temperate and tropical seas globally. In Canada, they’re likely present throughout much of the Pacific waters, including inlets, the continental shelf and slope, and the Strait of Georgia. Currently, there are no reliable indicators to gauge their population in Canadian waters. Historical estimates suggest around 8000 individuals in the northeast Pacific, but this figure is uncertain. Over the last five years, encounters with immature sharks in the Strait of Georgia have dropped by over 90%, possibly due to environmental changes such as rising water temperatures, rather than by-catch mortality. In Atlantic Canada, they’ve only been spotted twice, indicating they’re rare or occasional visitors in these waters.

Primarily a deepwater species, bluntnose sixgill sharks are found from the surface to depths of 2500 meters, mostly over outer continental and insular shelves. Juveniles stay in shallower waters until adolescence, when they move deeper. In Canada’s Pacific waters, immature sharks sometimes venture into shallow areas, offering scuba divers a chance to observe them.

Mating and courtship likely occur in deep waters. These sharks are ovoviviparous, meaning the young hatch inside the female before being released. Females have a two-year reproductive cycle with a gestation period of 12-24 months, carrying 47-70 pups each measuring 61-73 cm. Females grow larger than males, reaching maturity at 421-482 cm, while males mature at 310 cm. Mature individuals are rarely found, and the species’ longevity is estimated to be up to 80 years, though this hasn’t been confirmed through aging studies. Bluntnose sixgill sharks are generalist nocturnal feeders with a wide variety of prey.

The main threat to these sharks in Canada is fishing, particularly as bycatch in halibut and spiny dogfish fisheries. Although there’s no current directed fishery for them, they were historically targeted for their skins, livers, and in an experimental fishery from the late 1980s to early 1990s, which was halted due to conservation concerns.