Aggressive aquarium fish released into the Mackay River have spread widely
A very aggressive and invasive fish species that feed on native fish has been found to be much more prevalent in a major North Queensland waterway than previously thought.
- The jaguar cichlid has spread to Fursden, Lagoon, McCreadys, Bakers and Sandy Creeks and the Gooseponds
- The fish threatens vulnerable native freshwater fish and grows to 45 cm
- Chances are, someone released their aquarium fish back into the stream.
QUT Masters research student Michael Mottley used environmental DNA analysis (eDNA) to detect the aquarium escapee, the jaguar cichlid, in the Mackay Pioneer River and streams and that he had pierced the weirs upstream of the river to threaten already vulnerable native freshwater species.
Mr Mottley said the eDNA analysis was carried out from water samples containing traces of mitochondrial DNA from scales or feces released into the water by the jaguar cichlid, he It is therefore not necessary to see the fish to know that it is present.
“This species was first found at Fursden Creek in 2014 and is believed to have entered waterways upon being released from an aquarium,” said Mr Mottley.
âThe jaguar cichlid, so named for its black spots, stays small in an aquarium but grows up to 18 inches in rivers and freshwater lakes.
âIt is classified as a nuisance fish because it is very aggressive and feeds on native fish, their young and their eggs.
âAs an aquarium fish, there are only a few equally aggressive species that could live in their aquarium without being eaten.
âThe public could distinguish the jaguar cichlid not only by markings but also by its unique dorsal fin. Native species similar in shape to the jaguar cichlid have two dorsal fins.
Mr Mottley said his research mapped the distribution of cichlids.
“We found that this fish had passed through the weirs upstream so that someone may have released them upstream, or that they were carried by the floodwaters.”
QUT ecologist Dr David Hurwood said, âWe need to know their distribution and abundance for management.
âEradication is difficult, but we can try to stop the spread by detecting it early and alerting the public to its presence. “
Trent Power, a member of the Mackay Regional Pest Management Group and an environmentalist for Catchment Solutions, said he was surprised to detect jaguar cichild DNA above Dumbleton Weir, given that the fishway had not been functioning for nearly a decade. ‘decade and that the spillway was impassable even during severe flooding.
âIt’s very likely that someone released the fish upstream at some point. Often times, these are members of the public who inadvertently collect harmful fish from the wild for their aquarium and then release the fish back into the wild when they no longer want to keep any fish.
âIf the release site is in another watercourse or in another part of the watershed, a new population can become established.
MRPMG, Reef Catchments and Mackay Regional Council supported this research which began in 2020.
Shelley Molloy, MRPMG member and Mackay Regional Council officer, said the jaguar cichlid poses a continuing risk to native fish communities and the best defense is to prevent their spread to new waterways.
âThe Mackay Regional Pest Management Group urges people to familiarize themselves with its appearance, especially those who collect fish for aquariums,â she said.
âPlease do not release unwanted aquarium fish into waterways. You must return the fish to the place of purchase or bring the fish to a competent authority.
Members of the public can turn over suspicious fish by contacting the Department of Agriculture and Fisheries on 13 25 23 or their local council.
Mr Mottley’s eDNA results showed that the harmful fish had spread from Fursden Creek to Lagoon Creek and the Gooseponds. Jaguar ciclid DNA has also been detected in McCreadys, Bakers Creek, Sandy Creek, and the Pioneer River upstream of Dumbleton and Marian weirs.