30 July 2023
This may be the last day of Shark Week on the Discovery Channel but on Cape Cod it runs all year. A new study published this week in Marine Ecology Progress Series tagged and counted great white sharks (Carcharodon carcharias) off the coast of Cape Cod, Massachusetts and found that 800 individuals visited the area from 2015 to 2018. That means Cape Cod may have the highest density of white sharks in the world.
Fortunately all the sharks weren’t there at the same time. As lead author Megan Winton of the Atlantic White Shark Conservancy (AWSC) explains, great white sharks are highly migratory. Their population peaks on the Cape from July to November when the water is warm, as shown in this screenshot from AWSC’s logbook for 2022. Individual sharks spend a few hours or a few weeks in the area. (Click here to see AWSC’s shark data and download their shark app.)
The sharks are attracted to the Cape by the abundance seals, one of their favorite foods. A Google Haul Out survey of southeastern Massachusetts estimated maximum counts of gray seals at 30,000 to 50,000 animals in 2012 to 2015. Harbor seals arrive in the fall and add to the seal population. No wonder sharks show up. Gray seals provide a lot of meat, weighing as much as 800 pounds.
During our recent trip to Cape Cod I saw lots of seals at Chatham Fish Pier. Several swam by the fishing boats but the vast majority were hauled out on a sand bar across the harbor. See that lumpy line of gray blobs? Those are gray seals.
While on the Cape I didn’t see any sharks but I did see a No Swimming shark sign at Race Point. I was looking for birds and, as it turns out, diving seabirds give the hint that a shark may be nearby. Both feed on schools of fish, the birds from above, the sharks from below.
The abundance of sharks and seals in Cape Cod’s waters is an environmental success story. Gray seals were almost extinct in U.S. waters by the mid 20th century because of bounty hunting in Maine and Massachusetts from the late 1800s to 1962. The seal population began to recover, slowly, when the bounties ended. Sharks made a comeback because of the seals.
Learn more in this ABC News interview with lead author Megan Winton of Atlantic White Shark Conservancy.
p.s. Well, technically, it’s only Shark Week for 5 months on Cape Cod — mostly from July to November.
(photos from Wikimedia Commons and by Richard St. John, graph is a screenshot of AWSC’ logbook website; click on the links to see the originals)
It could be shark week at any location if they chose to come up .
When you are from here it’s always “on the cape” not on the “at the cape”.
Thank you, John. Since I’m “from away,” I wondered about that. Corrections made.