A scientist says it’s good news for the Swan River’s ecosystem as bull sharks move in to give birth to their pups and hunt.
A scientist says it’s good news for the Swan River’s ecosystem as bull sharks move in to give birth to their pups and hunt.
By Hannah Murphy
October 2, 2025 — 3.00am
A shark scientist predicts the number of bull sharks in the Swan River will climb over the coming months, a week after a school of the animals forced the closure of City of Fremantle beaches.
The school was spotted near the old Fremantle Traffic Bridge near the site where 16-year-old Stella Berry was killed by a bull shark in 2023.
The sightings were reported to the Department of Primary Industries and Regional Development, which sent a boat out to tag the sharks as part of its broader shark tracking program initiated after Stella’s death.
However, Australian Marine Conservation Society scientist Dr Leo Guida said it was likely bull shark numbers in the Swan would increase as the weather heated up – which was a positive sign for the river’s ecosystem.
“Healthy numbers of sharks are crucial for healthy ecosystems on which many of us depend on for work, play and culture,” he said.
“A number of factors could be driving schooling behaviour, including the presence and variety of prey items – the reasons why these very areas have been popular with fishers.
“As we head into the warmer months, bull sharks will increasingly use coastal and estuarine habitats to feed and pup.
“Understanding the population size, where, when and how they move are all crucial elements that can better inform safety and ecologically responsible management of Australian fisheries.”
A spokeswoman from the Department of Primary Industries and Regional Development did not respond to questions regarding if it had begun tagging sharks from last week’s school, but said no one had reported the animals since.
“[The department] has not received any further public reports of shark sightings in the Swan Canning Estuary over the long weekend and is continuing to monitor the situation,” she said.
The department said its broader tracking program was due to begin in coming months regardless.
“[The department] will be continuing its bull shark tagging research program in the Swan Canning Estuary from late spring through to early autumn,” a spokeswoman said.
“[We are] also working with Department of Biodiversity, Conservation and Attractions to build on the research and track the movements of juvenile bull sharks in the Swan Canning Estuary.”
To date, both departments have caught and tagged a total of six bull sharks.
Only two were caught in the Swan Canning Estuary.
The department said anyone who spotted a shark should report it to Water Police immediately.
Hannah Murphy is a journalist with WAtoday.Connect via email.
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