The cold, deep channels of Puget Sound may seem an unlikely home for sharks, yet the complex inland waters of the Salish Sea host a resident population of several species. The unique environment, characterized by low temperatures and deep basins, provides suitable habitat for at least a dozen species. These sharks maintain a presence that is largely unseen by the Sound’s human population.
The Abundant Resident: Spiny Dogfish
The most frequently encountered shark in Puget Sound is the Pacific Spiny Dogfish (Squalus acanthias), an abundant, slender shark that rarely exceeds five feet in length. This bottom-dwelling species is easily identified by its two dorsal fins, each featuring a sharp spine at its leading edge that can deliver a mild toxin. Dogfish form large, dense schools and play a significant role in the local food web, preying on small schooling fish like herring and sandlance, as well as various crustaceans.
Historically, this species was targeted heavily in the region, particularly during World War II, when its liver oil was sought as a source of Vitamin A, leading to rapid population declines. Dogfish are slow to reproduce; females do not mature until around 35 years old and have a gestation period of up to two years. Although targeted commercial fishing is now restricted, dogfish are still caught frequently as unwanted bycatch in other fisheries, posing an ongoing management challenge given their vulnerability in the southern portions of the Sound.
The Deep-Water Giant: Sixgill Shark
The Bluntnose Sixgill Shark (Hexanchus griseus) is the largest shark regularly inhabiting the Sound, with adults capable of reaching lengths of up to 20 feet and weights over 1,000 pounds in the open ocean. Unlike most sharks that possess five gill slits, the Sixgill has six. This massive species typically resides in the ocean’s deep, dark waters, often thousands of feet below the surface.
Puget Sound is believed to serve as an important nursery area for the Sixgill, where smaller juveniles spend their early years in relatively shallow, protected channels. Divers and researchers most often encounter these sub-adults in localized areas like Elliott Bay. The presence of pregnant females and young sharks in these shallower waters suggests the Sound provides a sheltered environment for pupping and development before they migrate to the deeper ocean as adults.
Other Occasional Visitors
Beyond the common residents, the Sound also sees the sporadic presence of several other shark species, either as transient visitors or deep-water specialists. The Salmon Shark (Lamna ditropis) is a powerful, fast-swimming predator often mistaken for the Great White Shark due to its similar coloration and body shape. These sharks are more common along the Washington coast but occasionally venture into the Sound, likely following their primary prey of salmon, herring, and squid.
Another small, deep-dwelling species is the Brown Catshark (Apristurus brunneus). These slender, dark-colored sharks prefer the soft, sandy bottoms of the deepest areas, sometimes reaching depths of 4,000 feet. More recently, species like the Broadnose Sevengill Shark (Notorynchus cepedianus) have been documented more frequently in the South Sound, suggesting that the dynamics of local shark populations are continually shifting.
Threat Level and Human Interaction
Despite the presence of large species like the Sixgill, the sharks of Puget Sound present no danger to humans. The few recorded, nonfatal shark incidents in Washington State have occurred exclusively in the coastal ocean waters. The deep-water habitat preference of the larger species means they rarely interact with swimmers or boaters, and the small dogfish are not known to pose a threat.
The primary risk in the Sound is not to humans, but from human activity toward the sharks, particularly incidental capture by fishing gear. Species like the Sixgill and Broadnose Sevengill are of conservation concern, and accidental mortalities due to interaction with fishing equipment are a problem. Responsible marine stewardship, including education on how to properly handle and release incidentally caught sharks, is important for managing the health and continued presence of these often-overlooked predators.