Despite announcing the detection of an invasive freshwater mollusc in the Brisbane River authorities will not attempt to eradicate it.
The invasive freshwater Corbicula fluminea is a bivalve gold clam native to Asia and was detected in several parts of the Brisbane River in February.
Its large spawning capacity, producing up to 400 offspring per day, can crowd out native species and block waterways, water treatment plants, and dams.
The clam typically ranges from 1 to 5 centimetres (2 inches) in size, with a distinctive triangular shape and a yellowish or brownish shell, often marked with concentric ridges.
This clam is capable of rapid reproduction, with females producing thousands of eggs per year. Additionally, Corbicula fluminea is a filter feeder, meaning it can quickly deplete food sources in an introduced environment, and it can tolerate diverse environments.
The clam is often unintentionally introduced to new environments through the movement of boats, equipment, and even the aquarium trade.
Queensland’s Department of Agriculture and Fisheries (DAF) said in a statement that it has known about the invasion for over a year.
“It has been reported that the clams now identified as this species were first noted in low numbers at Colleges Crossing early in 2023,” it said.
It is believed to be contained to areas in the Ipswich region of the river.
The statement indicated a decision not to start eradication was made in January this year after the National Biosecurity Management Consultative Committee met.
They concluded that as the clam was already well established in the river, effective eradication methods would be redundant.
“Freshwater gold clam has not been successfully eradicated from any locality it has invaded globally,” said the DAF.
These claims are supported by evidence from Asia, South America, and Europe where attempts to extinguish the clam after experimenting have failed with several methods.
In New Zealand, the gold clam has taken a foothold in the Waikato River where it was first noticed in May 2023.
“Wake boats present a higher risk of transmitting the freshwater gold clam as there is currently no known reliable method of cleaning the internal tanks and bladders,” they said.
The DAF said a national surveillance program and preparedness strategy had been initiated.However, the lack of action on eradication has raised concerns with the Invasive Species Council which said there would be significant environmental consequences if the infestation were to spread further.
“It tends to become extremely abundant, sometimes more than 10,000 a square metre, and outcompete native mussels,” said Carol Booth from the Invasive Species Council.
“During extreme weather events, large numbers can die and release toxic amounts of ammonia.”
Ms. Booth referenced a research paper that detailed the total global cost of the clam was greater than US$12 billion over the past 40 years, which she said was an underestimate of the true cost implications as data was taken only from documented cases in North America.
