It is early winter, and sharks are on the move.
Unseen and unsuspected, our most common shark, the spiny dogfish, leaves its deepwater holes and heads for the open ocean. This must be an impressive migration. Spiny dogfish are abundant in the Salish Sea, the most common bottom-dwelling fish-eating predator.
Thousands upon thousands are on the move. They will return in spring.
But they are not the only sharks in the Salish Sea. A pair of discoveries in Hammersley Inlet, not so far from the Key Peninsula, has brought energy back to the idea that Puget Sound’s bays might be important to the life cycles of several larger shark species.
One of the largest sharks in the world, the bluntnose sixgill shark, appears to use the Salish Sea as a nursery. These are deep-sea animals that live around the world. Adults, which can exceed 18 feet in length, stay at ocean depths, but juveniles are encountered by divers here.
Randy Babich, a retired fisherman in Longbranch, has caught two sixgill sharks in his decades of salmon fishing in Washington. The sharks, he said, were approximately 13 feet.
“I did not harm them,” he said. “All sharks I hold in high esteem. They get a bad rap. Such fascinating creatures.”
A flurry of interest and research surrounded sixgill sharks in the early 2000s when divers began to report them in unusual abundance in Elliott Bay. Filming, tagging and genetic analysis revealed that the sharks stayed in loose sibling groups and moved from deeper water during the day to shallower water at night. They shifted their ranges north in winter. Then, after a number of years, they vanished.
Researchers think that sixgill sharks in the Salish Sea, once they reach a certain size, head for the open ocean. Like spiny dogfish, sixgills are ovoviviparous, meaning mothers hold their eggs to develop internally and give birth to litters of live young. Juvenile sharks may benefit from a place with abundant food and protected waters. But there may be other, longer cycles at play.
While much remains unknown about the sixgill shark’s life history, the spiny dogfish holds several distinctions. It is one of the longest-lived sharks, with some living over 80 years — right up there with rockfish. Its females reach sexual maturity later than any other shark, at an average of 35 years old. Its gestation period, at 18-22 months, compares with that of an elephant.
Such slow-reproducing sharks are vulnerable to population collapse. They did survive one fishing bonanza. In the 1930s, the livers of tope sharks and spiny dogfish were found to have high levels of vitamin A. By 1941, shark liver was worth $2,000 per ton and hundreds of boats were targeting sharks on the Pacific coast. During this time, according to Babich, several Gig Harbor boats trawled for dogfish off Neah Bay. The sharks got a lifeline in 1948 when vitamin A was successfully synthesized, and by 1950 the fleet had turned its attention elsewhere.
The tope shark, also known as the soupfin shark, is one of the thrilling Hammersley Inlet discoveries. It had never before been confirmed in Puget Sound. The team of researchers that caught, measured, and released it hypothesized that it is likely a new arrival, perhaps linked with warmer water temperatures and a spike in anchovy abundance. Tope sharks have yet to recover from the vitamin A plunder and are globally listed as critically endangered.
But the researchers were fishing for a different shark. In 2021, a Shelton fisherman began catching large sharks in Hammersley Inlet, and experts identified the species not as the expected sixgill shark but the unknown-from-Puget-Sound broadnose sevengill shark. Over the last two summers, the researchers have caught over a dozen sevengill sharks there, the largest a nearly 7-foot male.
Again they hypothesize that this is a novel development. A century of intensive study and fishing in the Salish Sea should have turned up some records if they had been here all along. Sevengill sharks eat all kinds of fish, rays, sharks, and marine mammals. One idea is that they are here because seals and sea lions have grown numerous here.
Perhaps the most incredible part of the discovery is that it occurred in one of the farthest reaches of the south Salish Sea, about as far from the ocean as you can get.
Might they be visiting the waters around the Key Peninsula?
While new sharks are appearing, another shark has all but vanished from the Salish Sea. Even its memory is nearly gone. It is the second-largest fish in the world, and it once summered here in large groups, especially around Vancouver Island, drawn by the Salish Sea’s massive plankton blooms.
It is the basking shark. These gentle giants grow to 40 feet and 10,000 pounds. They live in temperate oceans around the world and migrate mysteriously. When feeding, they swim slowly at the surface, seeming to bask in the warm water. Their cavernous mouth has gill slits that nearly encircle the head and bristle-like structures called gill rakers that filter plankton like a whale’s baleen.
In contrast to a sixgill shark, which might have a litter of 80 pups, each 2 feet long, basking sharks birth just a few large pups that reach up to 6 feet in length. Gestation is thought to last as long as three years. Many parts of their life cycle have never been observed.
Sightings are exceedingly rare. Before a Canadian guide found one this summer while paddleboarding alone near Salt Spring Island, none had been seen in the last four years. In our neck of the woods, a fisherman in a canoe encountered one near Harstine Island in 1997.
Basking sharks have also been targeted for their livers, which make up to 25 percent of their weight. Sharks lack swim bladders and use the oil in their huge livers to maintain buoyancy.
In the 1940s, Canadian fisheries authorities deemed basking sharks a destructive pest. They were common enough to impede boat traffic. They often became entangled in fishing gear. An eradication program over the next two decades killed over 1,000 basking sharks. It involved a blade mounted to the prow of a government patrol vessel that killed sharks by ramming them.
While basking sharks elsewhere, such as Ireland, show signs of recovery, our West Coast population remains exceedingly endangered. A group of local scientists has been formed to keep the memory of basking sharks in local waters alive. Gathering knowledge depends on sightings.
The Marine Life Center in Gig Harbor has an exhibit on Salish Sea sharks on display until June.
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