Hawaiian Reef Sharks: possible competition for food causing massive decline

RTSea: For reef sharks, commercial shark fishing isn't the only thing that threatens their survival. In reef communities near populated islands, an additional threat comes from the taking of fish by local fishermen - fish that often constitute a major portion of the sharks' diets. When local and/or commercial fishermen compete for the same food source as reef shark species, it can be a crippling blow to the shark population. A recent study by Hawaii's Joint Institute for Marine and Atmospheric Research showed a drastic reduction in reef shark populations around populated islands in Hawaii as opposed to more uninhabited islands or pristine reefs. "We found 90-97 percent decline in reef shark abundance: white tip, grey, galapagos and nurse sharks," said Marc Nadon, a researcher with the Institute. The researchers have not been able to determine a more specific cause but look to accidental bycatch (sharks are now more protected, at least from legal commercial shark fishing, due to recent legislation) and overall fishing pressure as contributing factors. "70 percent of reef shark diet is reef fish, so if you remove the food source it would be logical that reef shark would follow the same trend and decline," said Nadon. While the researchers will be doing more studies this fall, their research's concern with competition for food has support based on what has been observed in other island nations. Both Samoa and the Marianas have seen major declines in reef shark populations around populated islands compared to other unspoiled reefs. Source: RTSea

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