By Dr. Becker
A team of researchers at the National Marine Fisheries Service of the Southeast Fisheries Science Center has discovered that many of the sharks currently swimming in the world’s oceans are significantly older than was thought.1
According to the researchers, sand tiger sharks, and probably other large shark species as well, are 11 to 12 years older than estimates given prior to the study. The team arrived at their conclusion by evaluating the vertebrae of sand tiger sharks from the waters off the southeastern United States and also South Africa.
The Sand Tiger Shark
Despite his somewhat fearsome appearance, the sand tiger shark is quite mild-mannered and non-aggressive.
Also known as a sand shark, sand tiger, and gray nurse shark, this marine animal has a large body and a mouthful of teeth that point every which-way. His skin is a brownish-gray, with rust-colored spots on top and white underneath. Individual sharks range from 6.5 to 10.5 feet in length.
As their name implies, sand sharks tend to hang out along the shoreline and on the ocean floor very close to shore. They like warm or temperate waters and inhabit all the world’s oceans, except the eastern Pacific.
Sand tiger sharks are the only sharks that rise to the surface of the water to gulp air, which they store in their stomachs so they can float motionless in the water, waiting for prey. They primarily feed on small fish, but also eat the occasional crustacean or squid.
The sand tiger shark has one of the lowest reproduction rates of all sharks, which is why it is listed as vulnerable and is protected in much of its range.2
Sandbar Sharks May Also Be Much Older Than We Thought
The researchers also believe that along with sand tiger sharks, the sandbar shark may be much older than presently thought as well.
Also called the thickskin shark or brown shark, the sandbar shark is one of the biggest coastal sharks in existence, and like the sand tiger shark, is docile and non-aggressive. He has a heavy body and an unusually short snout for a shark. Females are longer than males, growing to 6.5 to a little over 8 feet in length. The average male is a few inches less than 6 feet. Body color ranges from a bluish grey to brownish grey to bronze, with a white underside.
Sandbar sharks are commonly found in shallow coastal waters such as bays, harbors, estuaries, or the mouths of rivers, in tropical or temperate waters worldwide.
Long-Lived Sharks Are More Vulnerable to Extinction
While some sharks appear to be quite long-lived, species that mature late, have long lifespans, and produce few offspring have low population growth rates and lengthy generation times. This combination of factors makes them more prone to extinction, since it is very difficult for them to bounce back from population losses.
Bottom line is that long-lived sharks like the sand tiger and also great whites, are apparently more vulnerable to commercial fishing stressors, climate change, and other human-caused threats.