Study Finds Drastic Decline in Reef Shark Population
April 29, 2012

Study Finds Drastic Decline in Reef Shark Population

An international team of marine scientists has discovered that the population of reef sharks living the Pacific Ocean have decreased by at least 90% over the past several decades, claims a new study published online Friday in the journal Conservation Biology.

As part of the study, a group of eight scientists used underwater surveys collected over the past 10 years from 46 different US Pacific islands and atolls as part of the National Oceanic and Atmospheric Association (NOAA) Pacific Reef Assessment and Monitoring Program, the University of Miami Rosenstiel School of Marine & Atmospheric Science, one of the institutions involved in the research, said in an April 27 statement.

In an article published by the Washington Post Friday, writer Juliet Eilperin said that the eight-person team attributes much of the population decline to human fishing.

According to LiveScience Senior Writer Stephanie Pappas, study leader Marc Nadon, a doctoral candidate at the University of Miami, and colleague pulled shark-sighting data from over 1,607 dives in the central and western Pacific region, including in the waters surrounding Hawaii and American Samoa. They focused specifically on five species of sharks -- gray reef sharks, blacktip reef sharks, whitetip reef sharks, Galapagos sharks and tawny nurse sharks.

After analyzing their data, the researchers discovered that the sharks were less well off the closer they were to people, regardless of how large or small the nearby human populace was, according to Eilperin. In fact, the population of each of these types of sharks, "'increased substantially as human population decreased' and the productivity and temperature of the ocean increased," he added.

"Around each of the heavily populated areas we surveyed -- in the main Hawaiian Islands, the Mariana Archipelago and American Samoa -- reef shark numbers were greatly depressed compared to reefs in the same regions that were simply further away from humans," Nadon said in a statement, according to AFP reporter Kerry Sheridan. "We estimate that less than 10 percent of the baseline numbers remain in these areas."

One of the study's co-authors, Julia Baum from the University of Victoria in Canada, told CNN's Matthew Knight that the most likely cause of the declining population is fishing, as the sharks are either accidentally caught in commercial fishing nets or purposely targeted for their valuable fins. She says that reef shark fins can sell for as much as $100 per kilogram, especially in Asian markets where they are used for shark fin soup.

"The pattern -- of very low reef shark numbers near inhabited islands -- was remarkably consistent, irrespective of ocean conditions or region," Baum told Sheridan on Friday. "Wherever there are people there are not reef sharks, so by implication they must have declined. But we can't say what period that decline happened over."