THIS is the face of death for many aquatic native species in the Redlands.
The fish is a female tilapia and the yellow beads in her mouth are her eggs.
African tilapia out-compete native species and are now found in virtually all Redland catchments, according to Redland City deputy mayor Wendy Boglary.
This fish was caught in Hilliards Creek by scientists working on a fishway which is aimed at improving the odds for native species.
Species like tilapia and carp now dominate many aquatic habitats due to high reproduction, simple food requirements and ability to live in a variety of conditions.
They can rapidly outnumber native fish and survive in places that are too tough for other species.
Unlike many native freshwater fishes, tilapia are able to retreat into saline waters during drought and move back upstream when conditions improve.
They affect native species by competing for habitat and food, behave aggressively and disturb plant beds.
Cr Boglary said council would soon engage experts to help with a pest fish control program.
Actions would likely focus on improving habitat, native fish protection and restocking, education and behavioural change. It was unlikely a single solution would work.
Cr Boglary said fishers should kill any tilapia they caught and dispose of them away from water.
Line fishing for carp and tilapia has been shown to significantly decrease populations. Bait like worms and corn worked well.
The species had become a problem because of people illegally releasing them, just as was done with commercial duck species being released into wetlands.
“I don’t think there is any way of wiping tilapia out now,’’ Cr Boglary said. “These pests have become well established in our creeks, dams and wetlands.
“However, if we all work together, we may be able to even up the odds for our native fish populations and tip the balance back in their favour.
“It is not a problem that council can fix alone and a joint effort is required by everyone.’’
To stop tilapia taking over Redlands waterways, catchment quality had to be improved because native fish like shaded, cool water with plenty of in-stream habitat like snags, logs and creek bank vegetation.
Restocking with local native species like jungle perch, bass, sea mullet and long-finned eels also was an option.
The state Agriculture Department says keeping tilapia is illegal.
Tilapia were introduced into Australia in the 1970s as ornamental fish and are now regarded as one of the greatest threats to Australia's native biodiversity.
