Some shark populations are estimated to be at less than 10 percent of their original levels, with some species possibly in danger of extinction. This is bad news not only for sharks, but for the many cultures that rely on them for protein in their diets.
Ecologists, too, warn of the effects of the decline in shark species and other top predators that are part of the ocean ecosystems. Eliminating sharks may induce what scientists call “ecological cascades,” where one effect induces yet another - sometimes with profound consequences.
One example of that process is the rise in populations of certain rays – key shark prey – in regions where shark populations have declined.
While healthy ray populations are important, too many means too much bottom feeding that can threaten seagrass beds and the shellfish that inhabit them. Those seagrass beds also serve as nurseries for many other species.
So losing sharks may seriously degrade marine ecosystems, which could threaten the fisheries tied to them. In addition, sharks can help control populations of invasive and exotic species – a growing problem as ocean ecosystems change.
Nations move to protect sharks
Fortunately there is some good news amid all the bad. Careful fisheries management can help sustain shark populations.
For example, spiny dogfish sharks, once seriously depleted in northeastern United States waters, have come back much faster than expected and now support a greatly expanded fishery.
Blacktip sharks in the Gulf of Mexico were just determined to be in healthy condition as a species. There is even some evidence that great white shark populations along the California coast may be increasing in response to careful management and improving prey populations.
Individual nations are making important down-payments to help rebuild shark populations. Well-designed marine conservation areas and other types of shark sanctuaries can provide real benefits, if linked to sustainable fishing in waters through which sharks migrate.
I have seen the potential first-hand, diving with abundant large sharks in Cuba’s Gardens of the Queen (Jardines de la Reina) National Park.
But even there – more than 50 miles off the southern coast of Cuba – sharks and other important species are taken when they wander outside the park, clear evidence that even the best area-based management must be tied to sustainable fishing.
Nations are now starting to work together to preserve migratory fishes such as sharks.
The U.S., Mexico and Cuba, for example, are exchanging shark population information in a first step toward shared management of sharks that migrate back and forth through the waters of the Gulf of Mexico.
This tri-national program is in its early stages, but its potential is exciting.
So, if the news on sharks today is often bad, it isn’t always so. And the good news lets us peek at a possible future in which populations of shark and other top predators are rebuilt, and whole marine ecosystems are becoming more stable and resilient.
There is much work to do, but a great vision is here today to power it.