Shark Numbers Along The Great Barrier Reef Have Dropped By 92% In Just 50 Years

According to a study published by Marine Policy, the world’s shark population is experiencing a significant decline with perhaps 100 million or more sharks being lost every year. This time it is the turn of the top predators of Australia’s east coast, whose numbers have dropped straight down alarmingly in the last half a century.


In a new study, it has shown that species like hammerheads, great whites and tiger sharks that live in the waters off the coast of Queensland have dropped by as much as 92 percent in just 50 years.

University of Queensland and Griffith University researchers analyzed data from the program, which has used baited drum lines and nets since 1962 to minimize human-shark interactions and now spans 1760 km of the Queensland coastline.

To understand the changes that have taken place from the initial stage (then and now), researches have used shark control data to historical records of shark numbers and shark catches over the last half a century.

“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,” Dr. George Roff of UQ, explained in a statement.

“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.”

The shark control program uses aquatic trap used to lure and capture large sharks using baited hooks. Therefore, this reduces the statistical chance of a shark encounter with humans. As stated by in a study, published in Communications Biology, approximately 50,000 sharks have been trapped using this method. However the range of species caught has been diverse, proper species identification in the recordings only began in the 1990s, therefore the earliest records grouped them all into five categories such as hammerheads, tigers sharks, great whites, whale sharks, and “other”.

“What we found is that large apex sharks such as hammerheads, tigers and white sharks, have declined by 74 to 92 percent along Queensland’s coast,” Dr. Roff said.

“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,” Roff said.

Moreover, some sharks are reaching their reproductive age as well.

“The average size of sharks has also declined – tiger sharks and hammerhead sharks are getting smaller,” Roff said.

It is unpredictable the interactions between humans and sharks. It is evident that the shark typically comes off worst. Researchers estimated that approximately 100 million sharks are killed per year by humans. However, they add that this is a conservative estimate, and the true number could be as high as 273 million sharks killed annually by humans while sharks kill on average six humans a year.

Large fishing nets are not discerning about what they catch. Nicole McLachlan
Large fishing nets are not discerning about what they catch. Nicole McLachlan

To end with, researches have come to a conclusion that while the shark control programs are contributing towards the lessening numbers of species. It has also been the focus on the commercial side both for the Asian market and bycatch due to large fishing nets.


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