Threats to sharks Sharks face innumerable threats in today’s global oceans. Having existed virtually unchanged for over 400 million years, they are at greater risk of extinction today than ever before. Presently, some of the most significant threats to sharks are: Biological vulnerability Sharks are apex predators. Like other apex predators (lions, bears, cheetah, etc), the population sizes of sharks are naturally limited by the carrying capacity of their environment. This means the number of sharks in the oceans is already low. If fished unsustainably the consequences on marine food webs could be disastrous and will likely have far-reaching, negative impacts on the entire marine environment. Fisheries As the human population continues to grow, there is increasing global demand for new sources of protein to fill the dietary requirements of many developing and developed nations. Coupled with continuing declines in fish populations, focus is now being placed on the development of shark fisheries to meet these growing demands. However, given their inherent susceptibility to overfishing – many shark species possess life-history characteristics more similar to long-lived mammals than fish – most shark populations are unable to withstand an increase in fishing pressure. Left unmonitored and inappropriately managed most shark fisheries collapse, resulting in the characteristic “boom and bust” nature of these fisheries. Globally, sharks are threatened by a wide range of fisheries. These include: 1. bycatch fisheries; 2. target fisheries; 3. recreational fisheries; 4. illegal fisheries; 5. bather protection nets. In South Africa, there are several fisheries which either target sharks or catch them as bycatch. These include the demersal (bottom) longline, pelagic (open ocean) longline, handline, trek net, bather protection net, recreational, and hake and prawn trawl fisheries. Other than regulations governing the protection of the great white shark, there are few other management measures in place for commercially exploited sharks. Shark fin trade The expansion of the East Asian population and consequent growth of a middle class with disposable income has been largely responsible for the rise in demand for shark fin soup. “Finning” is the practice of removing the fins of a shark and dumping the live carcass at sea, where the shark proceeds to suffocate and drown. It is an extremely cruel and wasteful practice (it only uses between 1-5% of the body weight), particularly given increasing demand for seafood protein products. The IUCN estimates that tens of millions of sharks are finned annually, and a recent study suggested that fins of between 26 and 73 million sharks are traded globally each year. Shark fins are currently among the most expensive seafood products, and can be sold for up to US$1000 per kilogram. Public misperception & persecution A lack of understanding of sharks has led to unabashed hunting of many animals since the movie “Jaws” was aired. Many people view sharks as senseless killing machines, which actively hunt down humans. In fact, although some shark species are opportunistic predators (eating whatever is available to them at any given time), many species are very specialized, eating crustaceans, squid, molluscs and other small marine creatures. The unmanaged global persecution of many shark species is likely to have a detrimental effect on their populations. Habitat loss & degradation Many shark species rely on coastal bays, estuaries and inshore waters as nursery and pupping grounds. These critical habitats are being quickly degraded by the increasing presence of human activities in coastal zones. Also, the widespread destruction of coral reefs due to sedimentation, global warming and dynamite fishing has negative impacts on those species commonly associated with coral reefs. The presence of large numbers of sharks near a coral reef acts as an indicator of the health of a reef. Climate change The effects of climate change on the marine environment remain largely unquantified. However, the very stability of these ecosystems is at risk due to changes in weather patterns, water temperature, food availability, and current patterns. Sharks are indicator species, meaning that a healthy shark population means a healthy ocean.
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