Would you like to know more about the state of sharks, in particular where they are most endangered and what conservation efforts exist to protect the apex predators of the seas? Want to learn what you can do to help? Get the answers in our Q&A with conservation expert, Sonja Fordham, of the Ocean Conservancy.
Q: What kind of effect is the overfishing of certain species like tuna having on sharks' populations? And what is being done to limit the amounts of fish that are caught to stop this? And what effects will occur if certain shark species unfortunately go extinct or move out of certain areas because of their depleting food sources?
- Toni
A: This is a great question that's a bit tricky to answer, except for the part about what is being done to stop tuna and shark overfishing, as the simple answer there is "not enough." More on that later.
First, we know that most sharks, as top predators, play key roles in keeping ocean ecosystems in balance. Sharks generally feed on weak and wounded individuals in prey populations and thereby keep them healthy and in check. The effects of removing sharks (or their prey) are difficult to predict, but scientists generally warn that consequences are likely to be not only negative, but cascading and often counter-intuitive. For example, in one case study from the tropics, the depletion of tiger sharks resulted in a decline in tuna; some might expect that tuna numbers would increase if predatory sharks were removed. In this case, however, the tuna declined because the sharks had been keeping populations of other tuna predators in check.
Beyond ecosystem effects, overfishing of species like tuna can have a negative impact on shark populations when fishermen searching for alternative species turn their attention to sharks, which, in most cases, are more vulnerable and subject to less research and fewer fishing limits than more traditional food fish (although many tuna populations are also seriously overfished due to inadequate fisheries management). Too often, due to their slow growth and low priority, sharks are overfished before restrictions on new fisheries are put in place. The key to changing this sad situation lies with people like you, who are enlightened enough to see the importance of sharks and committed enough to speak up about it.
The topics you raise are likely to be discussed at this year's meeting of the International Commission for the Conservation of Atlantic Tunas (ICCAT), the first international fisheries body to ban shark finning and consider limiting the number of sharks taken in the tuna fisheries it governs. You can help by asking the US government's fisheries service (and all ICCAT member countries) to act this year to require the release of endangered porbeagle sharks and reduce overall fishing pressure to guard against overfishing of mako sharks as well as tuna. ICCAT and other international tuna commissions also need encouragement to improve enforcement of their shark finning bans by requiring that sharks be landed with their fins attached.
