It has been said that if you give a man a fish you feed him for a day, though if you teach a man to fish you feed him for life. But times have changed. Now we know that only if you save species of fish from overexploitation will there be hope of providing food for a lifetime, let alone for generations that follow.

Fish and other sea creatures historically valued solely as commodities are critically important to healthy ocean ecosystems, which in turn provide benefits to humankind. Yet the ocean is in deep trouble. Fish populations once thought to be inexhaustible now face the prospect of becoming extinct for any commercial purpose – and even completely disappearing – if policy changes are not made soon.

Iconic species such as bluefin tuna (pdf) and many kinds of sharks demonstrate the gravity of the issue. Optimistic reports find that between 18% and 28% of Atlantic bluefin tuna remain from the number in the sea half a century ago; others estimate that there are fewer than 10%. Meanwhile, a number of shark species (pdf) have declined by more than 90% in some areas, due largely to the growing international trade in shark fins.

It is not too late to save these animals and reverse their decline. Protection for whales, while not universal, has resulted in a gradual recovery of several greatly depleted species. African elephants, poached in many countries to a fraction of historic numbers for their ivory tusks, began to recover following a ban on international ivory commerce. International trade controls are working to give ocelots, jaguars, alligators and crocodiles, hunted for their skins, a better chance for survival.

Governments belonging to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites), a treaty used to protect wild animals and plants from overexploitation for international commerce, will soon meet in Qatar. There, they will decide whether or not Atlantic bluefin tuna and several shark species receive needed protections.

The treaty, among 175 countries, provides a vital, enforceable tool to prevent the depletion and eventual disappearance of species subject to trade. It limits or prohibits international trafficking in plants and animals that are at risk owing to such trade. If populations recover and sustainable use can be demonstrated, restrictions may be removed.

An expert panel assembled by the UN Food and Agriculture Organisation agrees that the Atlantic bluefin tuna merits a Cites Appendix I listing, which stops trade completely. International seafood markets and expensive sushi restaurants the world over prize these animals, giving them the distinction of the world's most expensive fish. They are being targeted relentlessly by modern industrial scale fishing operations that serve a high-end luxury market.

Delegates to the Cites meeting will also consider eight species of sharks for a level of protection that does not ban trade but requires export permits for any transactions once trade is confirmed to be legal and sustainable. As many as 73 million sharks are killed every year for their fins, a delicacy in China and other Asian markets. Some sharks, taken for their meat, may live for decades and have unusually low reproductive rates – characteristics that lead to rapid decline when fished commercially.

Unfortunately, delegations at many international fisheries management meetings have been led by each country's fisheries agency, and typically maintain close ties to the very industry they regulate. Over the years, these organisations have failed to prevent declines in Atlantic bluefin tuna and other heavily exploited species. With fish populations at a fraction of historic levels, it is time to act. International trade controls can make a difference for these species where the actions of individual countries have repeatedly failed.

The increased attention that will be focused on marine fish at the Cites meeting in March is welcome, given the dire status of bluefin tuna, hammerhead sharks and others that will be considered. It may take decades for these species to recover, but unless actions are taken now, the future appears bleak. Our children may condemn us for allowing them to disappear. Or maybe, just maybe, they will salute us for taking action while there still is time.