The big garoupa displayed as the centrepiece of a business lunch or the shark's fin soup that highlights an expensive dinner represent tradition and wealth; however, in affluent societies such as Hong Kong, such fish are being consumed at rates that are driving many species into extinction. Unwittingly, we are contributing to denigration of ecological systems - and the consequences are serious. Societies define themselves through cultural traditions; but in an ever-evolving world, they have to face an undeniable reality: that some practices are no longer environmentally sustainable. While some of the damage that has been done is irreparable, some can be reversed through replenishing stocks - although it will involve us going with less of our favourite foods so that nature and time can heal the wounds. Governments, through regional and international agencies, are already working towards such goals for the worst- affected species. But as Japan's ignoring of the rules on catching southern bluefin tuna shows, this is not enough. The nation has been penalised for catching 20 per cent more of the species than allowed last year by having its quota for the fish cut in half for the next five years. A recent report by the environmental group WWF concluded there was a need for immediate protection of dwindling bluefin tuna stocks in the Mediterranean and eastern Atlantic, where it said illegal overfishing exceeded quotas by at least 40 per cent. Bluefin tuna is prized in Japan to make the traditional delicacies sashimi and sushi. The bulk of the world's annual bluefin catch - 150,000 tonnes - goes to the country, although demand is also rising globally. As a result, bluefin prices are higher than for any other fish - and fishing fleets are often willing to break the rules. With the world eating more fish than ever before, the threat extends beyond bluefin tuna. Experts contend that because of our appetite for sea creatures, many popular species are in trouble. Modern vessels and new technologies such as satellite and sonar tracking mean that more fish are being caught and the bigger species, such as bluefin tuna, are not able to breed quickly enough to replenish numbers. Fishing methods used to target a particular species often catch fish that are not wanted and many of these die and are discarded. The oceans are almost depleted of the valuable, bigger fish at the top of the marine food chain and fisheries are rapidly working their way through the lower strata. This has ramifications for marine ecosystems and other wildlife; the biology, chemistry and physical structure of the Earth are being permanently changed. We have to be more cautious and protect our ocean resources. Overfishing has to stop and stricter quotas and harsher penalties need to be imposed by watchdog organisations. Above all, governments must ensure that their fishing fleets abide by the rules.