Showcasing sharks of Washington this shark week
We are coming up on the “fins” of Shark Week, which wraps up July 31. Did you know that Washington’s marine areas are consistently home to about 12 species of sharks and more than 530 species roam the waters worldwide!
The 12 shark species regularly found in Washington waters include the spiny dogfish, tope shark (also known as a soupfin shark), basking shark, blue shark, bluntnose sixgill shark, broadnose sevengill shark, brown catshark, common thresher shark, pacific sleeper shark, shortfin mako, salmon shark and great white shark.
“As apex predators, sharks play an important role in the ecosystem by maintaining the species below them in the food chain,” said Lisa Hillier, a Washington Department of Fish and Wildlife (WDFW) biologist in the marine fish science unit. “They help remove the weak and the sick as well as keeping the balance with competitors helping to ensure species diversity.”
Other notable reasons why sharks are important is they serve as an indicator for ocean health; as predators, they shift their prey’s spatial habitat, which alters the feeding strategy and diets of other species; and through the spatial controls and abundance, sharks indirectly maintain the seagrass habitats.
The earliest known sharks roamed the waters around 420 million years ago, but most modern sharks can be tracked back about 100 million years (most fossils are teeth). Sharks range in size from the 6.7 inches (dwarf lantern shark) to the whale shark which measure up to 40 feet long.
Did you know that sharks have about 30,000 teeth in a lifetime, and that the cartilage that makes up the skeletons of sharks is about half the density of normal bone?
Another interesting fact is sharks take water in through their mouths and push it over their gills in order to breathe in a process called ram ventilation. While some can pump water over their gills at rest, others don’t have that ability and must always keep swimming to breathe.
Not all sharks reach monstrous size, and the average shark species is under 6 feet long, weighing less than 30 pounds.
Sharks tend to get a bad rap from movies like Jaws, and 84% of people see this image when you say “shark.” This movie led to the senseless killing of tens of thousands of sharks.
According to Hillier, between 1837 — when record keeping began — and 2021, only two unprovoked shark attacks have occurred in Washington and the last was in 2017.
Great White Sharks are known to swim off the Washington coast and travel as far north as British Columbia.
The most abundant shark species in Washington’s marine areas is the spiny dogfish (Squalus suckleyi) also known as a mud shark. The spiny dogfish can measure up to four and a half feet long and weigh in at 20 lbs. This shark is unique in that is has one of the longest gestation periods of any organism, staying pregnant up to 24 months.
“Dogfish are definitely the most abundant in Puget Sound, and they form an integral part of the fish population,” said Bob Pacunski, a WDFW marine biologist. “In the past we’ve done some tagging of dogfish and while we know most don’t travel very far, we actually recovered a tag from one individual that made to Japan.”
In the 1940s, the spiny dogfish was heavily fished for their liver oil and fished for food from the 1970s until recently. In fact, a relative of the dogfish that inhabits the marine waters around the United Kingdom are highly sought after and used for fish and chips.
Salmon anglers often give dogfish an unfavorable reputation as more of a nuisance fish but they play an important role in the Sound’s ecosystem.
“Dogfish aren’t our enemy and they’re even fun to catch by recreational anglers,” Pacunski said. “If the dogfish went away then we know something is out of whack in Puget Sound.”
The spiny dogfish have light turquoise green eyes, dorsal fins, sandpaper-like skin, and white spots along its entire body. The species name “suckleyi” refers to the shark’s two sharp spines near the dorsal fins that pack a mild venom. Dogfish are a long-lived species averaging 30 to 40 years but can live up to nearly 70 years.
Dogfish often aggregate in large schools that can range into the thousands. Their diet includes fish, squid, crab, jellyfish, sea cucumber and shrimp.
While sharks are seen in local waterways, they do remain a mystery overall. WDFW regularly monitors them through trawl surveys, collecting videos, shark sampling, tracking trends, dissections, and studying cause of death by those found washed up onshore.
Recently, WDFW marine biologists in a collaboration with NOAA and OSU have been tracking sevengill sharks and located them in deep southern Puget Sound. Tags have been put on a couple of sevengill sharks so they can be tracked to get a better idea of what brings them into the area.
“It might be food that is now attracting them down this far into Puget Sound or they could have been here for years,” Hillier said. “We have documented sevengill sharks in places like Willapa Bay, but this new tagging research will hopefully shed some light on sevengill use of the Puget Sound.”
To learn more about sharks this Shark Week, visit WDFW’s website at https://wdfw.wa.gov/species-habitats/species/bottomfish/shark-skate-ratfish.