Efforts to reintroduce a sustainable population of native cod into the Brisbane and Bremer rivers are proving successful, with a native cod recorded using the Bremer River fishway near Ipswich for the first time since restocking efforts began.
Ipswich City Council Environment and Sustainability Committee Chairperson Councillor Jim Madden said tens of thousands of Mary River cod fingerlings had been released into Ipswich creeks and rivers over the past five years.
“Mary River cod are an apex predator and grow to more than a metre in length, and importantly they can stifle the reproductive abilities of exotic fish including tilapia, carp and mosquitofish,” Cr Madden said.
“Mary River cod fingerlings, through collaboration with Somerset and Wivenhoe Fish Stocking Association and other partners, have been released into to waterways where the extinct, but closely related, Brisbane River cod once existed.
“After five years of restocking cod into Ipswich waterways, this is the first time a mature specimen of the species has been observed navigating the Bremer River fishway.
“Mary River cod take four to five years to reach breeding maturity so it’s possible the fish recorded at the Bremer River fishway was among the first released into the waterway through the cod recovery program in 2020.
“This is a key milestone for restocking efforts because it’s a strong indication that conservation and fish passage initiatives are making a real difference in bringing back cod to local waterways after 100 years of extinction in the Bremer Catchment.”
Councillor Madden said the 90-metre rock-ramp fishway was built to restore fish passage past a 2.4 metre high weir, re-establishing connectivity between upstream and downstream reaches of the Bremer River.
“This connection is important for many native species – including the endangered Mary River cod – which rely on unimpeded access to upstream freshwater habitats throughout their life cycle to support healthy populations,” Councillor Madden said.
Catchment Solutions fisheries ecologist Matt Moore, who constructed the fishway, said the survey results were a huge achievement for the ecological health of South-East Queensland waterways.
“We’re not just helping the endangered Mary River cod, Australian bass and Sea mullet, important recreational and indigenous fishery species, were also recorded,” he said.
“With thousands of man-made barriers across our rivers, such as dams, weirs and culverts, fish populations have suffered. Well-designed fishways are essential for reversing that trend.”
Somerset and Wivenhoe Fish Stocking Association president Garry Fitzgerald said it was incredibly rewarding to see the fingerlings released years ago grow into adult healthy cod.
“This gives real hope for the species’ recovery,” he said.
“It has been possible with the support of all levels of government and community partners to help fund cod re-stocking efforts in the catchment, including CleanCo, which manages the fishway site.”
Swanbank Site Manager Trevor Turner said CleanCo is proud to play a role in local conservation efforts, with the latest survey results showing real progress.
“We’re proud to support fish restocking and fingerling releases here in Ipswich, and it’s great to see those efforts delivering real results for the Bremer River,” Mr Turner said.
“Seeing endangered Mary River cod successfully use the Swanbank fishway is very encouraging and it shows how working together locally can make a lasting difference to our environment.”