Caught incidentally in the commercial fishery off the outer Washington coast with longline and jig handline gear.
The litter size for bluntnose sixgill sharks ranges from 22 to 108 pups! Due to their prevalence in deepwater habitat, evidence indicates this is one of the most widespread shark species in the world.
Description and Range
The bluntnose sixgill shark has a heavy, powerful body with a broad head and small florescent green-blue eyes. They range in color from brown to tan to black, with darker colored spots on the sides. This species has a light colored lateral line down the sides and on the fins’ edges. They have one dorsal fin located near the base of the tail. The pectoral fins are broad with rounded edges. This species has six gill slits, rather than the five of most other shark species, which gives the species its name. The mouth of this species is ventral with 6 rows of lower, bladelike, comb-shaped teeth on each side. Teeth in the upper jaw have one strong cusp and several smaller cusps, and are used for gripping food while the lower jaw saws pieces away. As an adult the bluntnose sixgill shark can grow to a massive size, with females generally growing larger than males.
Bluntnose sixgill sharks can grow up to at least 550 cm (18 ft) in length, and 590 kg (1,300 lbs) in weight. Males average between 309–330 cm (10.14–10.8 ft) in length, and females are larger, averaging between 350 and 420 cm (11.5–13.8 ft) in length. Female weight varies greatly with reproductive stage due to large litter size.
Maximum age is 80 years old, though typical aging techniques for this species perform poorly due to low levels of calcification in most body structures.
The bluntnose sixgill shark is circumglobal: both in tropical and temperate waters. In the Eastern Pacific, they are found from the Aleutian Islands, Alaska to Baja California, Mexico. They are a highly migratory species that typically inhabits water depths greater than 90 m (300 ft), and has been recorded as deep as 1,875 meters (6,152 ft). This species is a deepsea shark, but like most fish that prefer the deep, they may move to shallower depths to feed. In some areas, such as Puget Sound, females move into shallow water to give birth, at which time they may be encountered by divers.
Sensitivity to climate change
Though limited information is available regarding the sensitivity of bluntnose sixgill sharks to climate change (particularly in Washington), there are a number of ways in which this species may be sensitive to changing ocean conditions. In general, increases in temperature may affect movement and migration patterns of sharks. The use of Puget Sound by juvenile sixgill sharks and their high site fidelity within Puget Sound could make them sensitive to climate-related changes, such as increases in temperature or potential decreases in oxygen, which could potentially lead to declines in prey availability (e.g., other sharks and rays, fish). Because sixgills are scavengers that target a wide range of prey, they may be able to shift prey species due to changes in abundance, but the high site fidelity of juveniles within Puget Sound, as well as their life history characteristics (slow growth, long generation times, low fecundity) may increase their sensitivity to climate-induced changes in Puget Sound. However, it appears Puget Sound sixgills are part of a larger, much more broadly distributed population, suggesting possible resilience to climate impacts.
Exposure to climate change
- Increased ocean temperatures
- Decreased oxygen
Rules and seasons
Recreational fishing for bluntnose sixgill sharks is closed in all Washington waters.
|January 30, 1991