Why Are There So Many Seals On Cape Cod?

It’s no secret that the seal population of New England has been exploding, and with that has brought the return of white sharks in steady numbers. (According to Cape Cod Online, the island of Muskeget alone went from hosting 19 adult seals to at least 3500 in 17 years.)

This increase of seals has also brought a number of problems: a depleted fish stock, crowded beaches that turn away tourists, and even lowered water quality from seal feces.

Some groups, like the Seal Abatement Coalition, want to use to buffer zones and deterrents (like sound blasts) to keep seals away from areas used by humans. But according to the National Marine Fisheries Service, no one even knows how big a healthy seal population is supposed to be at Cape Cod, so it’s difficult to make conservation decisions for the population.

But why so many seals, now?

One reason is that the seal population has been protected by the Marine Mammal Protection Act of 1972, which forbids humans from harming and harassing marine mammals. Years of protection have enabled the seal populations to grow, limited only by the constraints of habitat, food supply, and predators.

Another reason appears to be that the white shark population, while on the rise, is still lagging behind the explosive growth of seals. One study estimated that white sharks suffered a 79% decline in the North Atlantic from 1986 to 2003. White sharks do not reproduce fast either, so it may take years before there is an adequate number of white sharks to keep the population growth of the seals at a stable state.

In this way, conserving white sharks leads to managing a healthy seal population. Swimmers and boaters should understand that sharing the water with great whites means sharing the beaches and land with fewer seals.


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