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The chondrichthyan lineage diverged from the osteichthyan line 440 million years ago, resulting in a vast evolutionary gulf between modern elasmobranchs and other vertebrates. Though this has supported the assumption that sharks are ancient, dangerous, and binary-minded, the few ethological studies done have noted intelligent actions including social exchanges. Yet their behaviour remains little known. On seeing that Carcharhinus melanopterus displayed complex actions during incidental meetings, a long-term ethological study of the species was carried out using artificial aggregations, at several sites in the fringe lagoon of Mo’orea Island, French Polynesia. Short and long-term behaviour was recorded in 473 individuals, including an ethogram, roaming patterns, social interactions, and cognition. C. melanopterus is considered sedentary, yet the home range could also be viewed as a place to pause between travels, for most individuals left for long periods. The study community and its visitors travelled in correlation with the lunar phase, in groups of up to six individuals, socializing with conspecifics encountered along the way, and displaying fluid social dynamics. C. melanopterus was highly alert to danger yet prone to investigate novel objects, a combination that generated a variety of tactics to remain hidden while investigating the environment. Basic to this was the use of the visual limit for escape or to screen their presence, indicating an awareness of being present and observable. Using their other senses, they could focus their attention on events beyond visual range and made swift decisions to act as circumstances unfolded. In their non-territorial, non-hierarchical society, any shark could lead, but it was usually the same ones that did so. Therefore, unusual individuals had a significant effect on events through social learning, suggesting the potential for culture. Actions in a variety of situations suggested complex cognition, and individuals displayed both positive and negative subjective states including playfulness.

A detailed analysis of fishing records has shown that the shark species accessible to global fisheries have been systematically depleted for decades. They were already fished to about 10 percent of their former levels by 2003. Now one species after another is being listed on the IUCN Red List of Threatened Species as their numbers drop towards extinction. Shark depletion has not been well documented and a large proportion of shark mortality has been bycatch, the target species being teleost fish. But with the rise in value of shark fins due to the shark fin trade, at the same time as teleost fish stocks have become severely overfished, sharks, along with tuna, have become the most valuable catches. Fishing on the high seas is scarcely profitable, and so is heavily supported by subsidies. But the shark fin trade, in which organized crime is heavily involved, is driven by enormous profits and provides a powerful demand for the fins of all sharks. Thus it is now being supplied by fisheries around the world. There is no interest in sustainability in consumer countries, and neither the will nor the resources to manage the trade exist. Although some shark fisheries might have been managed sustainably in some regions for certain species for meat, such fisheries are increasingly dependent on the shark fin trade.. The rising global demand for shark fins, coupled with the increasing depletion of the animals supplying that demand, makes commercial fishing for sharks unsustainable. Given their high ecological value across the aquatic ecosystems they inhabit, it is important that they receive more effective measures of protection going far beyond the currently existing ones. In particular, protection of all sharks, manta rays, devil rays and rhino rays through an Appendix I CITES listing should be effected immediately due to the scale of the global take of the shark fin trade and the state of shark depletion amply documented in the literature.