Our friends at the Pew Environment Group put together this extremely helpful graph that goes a long way in explaining just why taking sharks out of the ocean by the millions is a bad idea. It turns out that sharks’ biological life history much more closely resembles that of marine mammals – and even grizzly bears – than that of their fishy cousins.
While some fish like swordfish and mackerel are able to reach maturity quickly and spawn by the millions several times a year, making them more resilient to higher catch rates, sharks are slow-growing, late-maturing and give birth to small litters of live young. Some sharks, like the Atlantic Ocean’s dusky shark, do not mature until as late as 21 years of age and give birth to as few as three pups every three years.
A female shark that produced 10 pups every two years for 20 years would add only about 100 individuals to the population. In contrast, a female swordfish could theoretically contribute millions of offspring, and it is possible that thousands of these could survive if natural mortality from predators, disease, or starvation was low.
Every year, 70 million sharks are taken from the ocean, a rate far higher than these vulnerable creatures are able to withstand. They’ve been around for almost a half-billion years but now face severe threats. While the Asian appetite for shark fin soup fuels much of the shark trade, other products, from shark liver oil dietary supplements to squalene-based beauty products contribute to their dwindling populations.
Learn more about sharks and what Oceana is doing to ensure their survival.