Great white shark breeding numbers in Australia revealed

They are protected and presumed to be in decline, but great white sharks may be fighting back with new research tracking how many are breeding in Australia each year.

New research has revealed how many great white sharks reproduce each year off the east coast of Australia — and challenges the claims by fishers and surfers that their numbers are increasing.

But the study also found great whites born since protection in 1999 are now becoming mature and able to breed, promising an increase in numbers in the near future.

In 2018 the CSIRO estimated that there were between 470 and 1030 adult white sharks, and when juveniles were included the number rose to between 2909 and 12,802 sharks,

Now new research from the University of Queensland estimates between 206 and 252 great white sharks successfully reproduce each year.

The study used DNA from juvenile and subadult sharks sampled from SMART-drumlines as part of the NSW government’s Shark Management Strategy to estimate the effective number of breeders, or parents, that breed each year.

One of the great white sharks spotted around Bermagui in NSW. Picture: Instagram/Jason Moyce

Data about the size of the shark was used to determine the year of birth for each shark.

Researcher Danielle Davinport from UQ Molecular Fisheries Laboratory said because the gestation period of a white shark is thought to be around 18 months, the implication is that not all female adult white sharks breed each year.

BITE CLUB: SHARK ATTACKS IN AUSTRALIA

“Monitoring the effective breeding population size can help early detection of population declines or increases,” Ms Davinport said.

After a record year of eight shark attack fatalities in 2020, the most since 1929, questions have been raised about whether the numbers of ­protected great white sharks are on the rise.

“By monitoring the effective number of breeders over time, we are hoping to address the age-old debate about whether white sharks on the east coast of Australia have increased in abundance after historic declines — ‘do we need to add further protections or are we already doing enough?’” Ms Davinport said.

“We found a stable trend in this study, so we need to continue monitoring in order to answer these questions.”

Great white sharks are breeding more in Australia. Picture: Instagram/Jason Moyce

Great whites were protected in 1999 with a ban on commercial and recreational fishing and the Environment Protection and Biodiversity Conservation Act in 2002 put a recovery plan in place.

“White sharks numbers declined significantly compared to historical baselines, up to 92 per cent over the past five decades based on data collected from the Queensland Shark Control Program,” Ms Davinport said.

“Overfishing and the direct impacts of bather protection nets were implicated in the decline of the white shark off the east coast of Australia.

“White sharks are vulnerable to declines because they have slow life histories; they are long-lived, slow growing and do not reproduce in ­Australian waters until approximately 5m — approximately 16 years of age for females — and the gestation period is 18 months.”

Despite anecdotal accounts of an increase in sightings and more great white attacks, the research team found little evidence of population growth.

But Ms Davinport said: “Interestingly, since protections were introduced in Australia in 1999, any sharks born since protections were enacted will only now be becoming mature, and hence able to reproduce to recover the population.”

However Bermagui commercial fisherman Jason Moyce said: “In the last five or so years we have definitely seen more great white sharks, especially juveniles, lots and lots more.”

BITE CLUB: SHARK ATTACKS IN AUSTRALIA

Originally published as Great white shark breeding numbers in Australia revealed