A hammerhead shark entangled in a Queensland Shark Control Program net at Magnetic Island in Queensland, Australia. (Photo by Nicole McLachlan)
After reconstructing data from Queensland Shark Control Program over the last five decades, a new study by researchers from University of Queensland and Griffith University found that the population of large apex predators has decreased as much as 90 percent during that time.
Researchers analyzed data from the QSCP program to create an historical baseline so that they could explore changes in the number and sizes of sharks over the past half century. The QSCP has used baited drumlines and nets to catch ad remove large sharks from areas where they may come in contact with humans since 1962, leaving a valuable data trail.
“Explorers in the 19th century once described Australian coastlines as being ‘chock-full of sharks’, yet we don’t have a clear idea of how many sharks there used to be on Queensland beaches,” UQ School of Biological Sciences researcher Dr. George Roff said. “What we found is that large apex sharks such as hammerheads, tigers and white sharks, have declined by 74 to 92 per cent along Queensland’s coast and the chance of zero catch—catching no sharks at any given beach per year—has increased by as much as seven-fold. The average size of sharks has also declined—tiger sharks and hammerhead sharks are getting smaller.”
The findings, which were published this month in the journal Communications Biology, contradicts notions that the country is experiencing a population explosion.
“We will never know the exact numbers of sharks in our oceans more than half a century ago, but the data points to radical changes in our coastal ecosystems since the 1960s,” Roff said. “The data acts as a window into the past, revealing what was natural on our beaches, and provides important context for how we manage sharks. What may appear to be increases in shark numbers is in reality a fraction of past baselines, and the long-term trend shows ongoing declines.
“While often perceived as a danger to the public, sharks play important ecological roles in coastal ecosystems.”