Shark Numbers Have Dropped By 92% In 50 Years On Great Barrier Reef

Photo by Jakob Owens on Unsplash

new study has revealed a very disturbing and worrisome statistic that shark populations off the coast of Queensland have dropped by as much as 92% in the last 50 years.

These tropic waters, home to some of the most iconic sharks including the great white, tiger, and hammerhead sharks, use to be one of the most diverse and abundant ecosystems in the world as the Great Barrier Reef sits just off shore of the coastline. 

Researchers from the University of Queensland used data from a shark control programs that surveys over 1,100 miles of the coastline and includes the Great Barrier Reef.  The program began in 1962 and was used to try and help minimize shark-human interactions.

Before that, there are no official records of shark numbers so researchers have used the shark control data to reconstruct historical record of shark numbers and catches over the last half a century to understand the changes that have taken place.

“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, who led the study, 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.”

Australia is not the only place seeing the drop in shark numbers as sharks have seen a huge decrease in numbers worldwide due to overfishing, being a product of bycatch, shark finning and climate change. 

The controversial shark control program uses baited drumlines to bring down local populations to try and reduce shark encounters with beachgoers and swimmers. As a result of programs such as this, the study also revealed that fewer sharks reaching reproductive age.

“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.

The importance of sharks cannot be overstated due to them being a keystone species. Sharks are at the top of the food chain in virtually every part of the planets oceans. In that role, they keep populations of other fish healthy and in proper proportion for their eco-system.

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