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Sharks Have Survived 5 Major Extinctions

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Sharks have survived 5 major extinctions, and only recently are the number of sharks is beginning to decline. This suggests that human exploitation is the main reason for the drastic loss of sharks and therefore, the overall effect on marine life, and indirectly the effect on human life via fisheries (fig1 and 2). In just under 50 years, slaughter of sharks has risen by 400% to
Figure 1. Graph showing an overall increase in global shark catch. approximately 800,000 tonnes per year[1], so now, around 90% of the shark population has been wiped out[2]. Sharks are very late at developing sexual maturity; for example, female great white sharks do not reach maturity until they’re about 10 years old and when they are eventually mature enough, they only give birth to a few pups a year. This slow reproduction process results in sharks being

killed faster than they reproduce, ultimately reducing the population size. The radical change
Figure 2 shows relative changes in population abundance of pelagic sharks in the Central Pacific (Ward & Myers 2005), Northwest Atlantic (Baum et al. 2003), Eastern USA (Myers et al. 2007), Gulf of Mexico (Baum & Myers 2004), and the Mediterranean (Ferretti et al. 2008) in shark population causes growing concern for other marine animals such as tuna, sea turtles and billfish. A study was carried out by the University of Miami to demonstrate the effect shark hunting has on the bay scallop. As shark populations decreased, the number of their

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