For example, numbers of porbeagle sharks, swift, ocean-going sharks once commercially valuable, declined dramatically until, by 1960, commercial fishers could no longer catch enough of them to cover their expenses. Thirty years later, porbeagle populations still have not recovered. As researchers begin to better understand the devastation human activities have brought to many shark populations, they also better understand the benefits sharks provide. Losing these top-level predators produces devastating effects to local ecosystems. Moreover, medical researchers are interested in learning more about sharks, particularly their immune systems.
Sharks recover rapidly from severe injuries.
They appear to be nearly impervious to infection, cancers, and circulatory diseases. For decades some people have believed that shark cartilage has anticancer properties. Although recent scientific studies challenge this belief, medical researchers continue to investigate the shark immune system in hopes of one day applying its secrets to fight human disease. To prevent the effects of overfishing and other human activities in the United States, state and federal management plans restrict the number of sharks that can be legally killed. Plans also require that fishers take entire sharks, instead of just the fins, preventing the practice of cutting off the fins and leaving the rest of the fish to waste.