HONOLULU April 25, 2012 -- Many shark populations have plummeted in the past three decades as a result of excessive harvesting for their fins, as an incidental catch of fisheries targeting other species, and in recreational fisheries. This is particularly true for oceanic species. However, until now, a lack of data prevented scientists from properly quantifying the status of Pacific reef sharks at a large geographic scale.
In a study published online April 27 in the journal Conservation Biology, an international team of marine scientists provide the first estimates of reef shark losses in the Pacific Ocean. Using underwater surveys conducted over the past decade across 46 U.S. Pacific islands and atolls, as part of NOAA's extensive Pacific Reef Assessment and Monitoring Program (www.pifsc.noaa.gov/cred/) the team compared reef shark numbers at reefs spanning from heavily impacted ones to those among the world's most pristine.
The numbers are sobering.
"We estimate that reef shark numbers have dropped substantially around populated islands, generally by more than 90 percent compared to those at the most untouched reefs", said Marc Nadon, lead author of the study and a scientist at the Joint Institute for Marine and Atmospheric Research (JIMAR) located at the University of Hawaii, as well as a PhD candidate with Dr. Jerry Ault at the University of Miami's Rosenstiel School of Marine & Atmospheric Science. "In short, people and sharks don't mix."
To obtain these estimates, Nadon and his colleagues used an innovative survey method, called 'towed-diver surveys,' which were designed specifically for the census of large, highly mobile reef fishes like sharks. The surveys involve paired SCUBA divers recording shark sightings while towed behind a small boat.
"Towed-diver surveys are key to our effort to quantify reef shark abundance," said Ivor Williams, head of
|Contact: Barbra Gonzalez|
University of Miami Rosenstiel School of Marine & Atmospheric Science