Flora and Fauna Fridays
A weekly entry about the life of our estuary and watershed.
(Our apologies for the delayed publication.)
Editor’s note: Yes, there are sharks swimming wild in New York City’s open waters! This item by Paul Sieswerda, former animal curator of the New York Aquarium and now more famously our city’s whale whisperer (check out Gotham Whale!) come courtesy of Nature Calendar.
Bertha, a sand tiger shark photographed here by J.L. Maher of the Wildlife Conservation Society, was caught off the coast of Coney Island and lived at the aquarium for 43 years. Her species is so common in the New York Bight that the aquarium has traded young ones for others species from around the world. Our friends at the Safina Center report a shark attack on a Monterey Bay kayaker. More locally, Erik Baard had a harmless kayaking encounter with a blue shark shark past the Narrows years ago, but that tale will wait for another day.
“Sharks and the City”
By Paul Sieswerda
As a former Curator at a public aquarium and still a public marine ecology educator, I am often above, in, or under the ocean’s surface and I think that I’m not alone in having brief shivers when the thought of what sea creatures may be eying my activities passes through my mind. It’s just a flash of trepidation and doesn’t slow me down, but I have to admit to it.
Sharks, of course, are prominent on that list of imagery and probably somewhat realistic in tropical waters. But in New York? You’re right, that’s crazy.
The Chamber of Commerce may not like to publicize it, but the waters around New York are full of sharks. Fortunately, the species are not man-eaters or dangerous, but sharks are plentiful and varied. It should be stated however, that one of the most horrific episodes in shark attack history took place very close by. In 1916, four fatal attacks took place along the New Jersey coast within the first twelve days of July, in Beach Haven and Spring Lake, and miles inland, in Matawan Creek. Another victim was also attacked in Matawan, but survived with the loss of a leg. That history changed the world’s image of sharks when Peter Benchley popularized the factual story in the book, Jaws. Of course, the movie seared the fear of shark attacks further into the psyche of a worldwide population. The fishing fleet off Montauk catches enough monster sharks to keep the impression in the back of most New Yorkers’ minds. However, experience settles those fears for New York swimmers since the chance of a shark attack ranks about in the same neighborhood as the risks as from asteroids.
Our native sharks are benign to humans. Local species are fish eaters like the sand tiger shark or scavengers like the smooth dogfish. There are sandbar sharks as well cruising off Coney Island beach. These sharks are happy to hunt fish and leave humans completely alone. In fact, sand tiger sharks and sand bar sharks rarely take bait from fishermen, so they are not often caught on hook and line. The dogfish are another story, and many striper fishermen are disappointed to pull in a dogfish instead of a fat striper.
Sand tiger shark, Carcharias taurus
The New York Aquarium has a number of sand tiger sharks on display. One specimen lived in the collection over 40 years. How long do they live? The shark in the photo, Bertha, was the longest living shark recorded at an aquarium and it was probably a couple of years old when it was captured. Since then, the Aquarium has supplied itself and other institutions with sand tiger sharks. Local fishermen catch them in their nets and notify the Aquarium. Since these sharks are usually small they can be transported fairly easily. Some have been sent as far away as Japan. A “pupping” ground seems to be along the southern coast of Long Island. Young sand tigers are caught each year incidental to the fishermen’s target species.
First Come, First Served
Sand tigers have a strange method of development. The embryos practice hunting within the mother! This cannibalism before birth is called oophagy.
Eggs are produced in the shark mother’s two uterine tracks, one after another. As the first egg develops into an embryonic shark, it eats the next developing embryo. This continues until the birth of the two babies that have grown in each uterus. They grow strong feeding on their potential siblings. At birth, the young sand tiger sharks are forty inches (100 cm.) in length, and completely ready to hunt on their own.
From : Sharks by P. Sieswerda
The adult sand tigers are usually about seven feet in length. They have two equal sized dorsal fins set at the rear half of the body. The nose is pointed and often upturned. The most prominent feature are the teeth that Richard Ellis, author and naturalist, calls the “wickedest-looking teeth in all of sharkdom.”
These teeth, however, indicate that they are fish eaters and not prone to take bites out of large animals (species that do are a real danger to humans). Although they look ferocious, sand tigers have adapted a mouthful of fangs that are designed to effectively grasp slippery fish. Most sharks must continually swim at a speed that gives them lift, but sand tigers are able to keep from sinking by holding a gulp of surface air internally, allowing them to cruise at slow speed and save energy for quick lunges that catch their prey unaware. In aquariums, it was found that sand tigers needed a minimum depth in their tanks, not for any space requirement, but to allow them enough distance to launch themselves above the surface to gulp air.
Most New Yorkers will not see sand tiger sharks except at the New York Aquarium, but it may be interesting to know that when gazing out from a Brooklyn or Long Island beach, or even sharing the surf, there are sizeable sharks out there playing out their lives, with little threat to people and deserving only the slightest twinge of fear. Knowing the facts is comforting, but I think it’s human to worry a little.
Or is it just me?