Pesticides from farms and cane fields washing into Queensland’s six main river systems could severely damage the state’s $80 million prawn industry, according to CSIRO research.
Pesticide run-off from farms was affecting crustaceans’ nervous systems and, in Bribie Island laboratory tests from 2017, tiger prawn larvae exposed to the level of pesticides found in the waterways would die.
Adult prawns, subjected to rigorous testing, showed no evidence of pesticide contamination.
The research also found that if subsequent field tests backed up the CSIRO’s findings, there could be a major impact on Queensland’s multimillion-dollar prawn industry and Australia’s $1 billion aquaculture industry.
The report, The impacts of modern-use pesticides on shrimp aquaculture; an assessment for north eastern Australia, was published in the February 2018 edition of the journal Ecotoxicology and Environmental Safety
CSIRO lead researcher Dr Sharon Hook said there was “one piece of evidence” that pesticides from farms were affecting crustaceans.
Dr Hook said the 2017 research must now be tested on larvae in the rivers where pesticide levels varied with stream flow.
“It seems to be preventing them from eating,” Dr Hook said.
“[Pesticides] are near the concentrations where they are just not able to catch live prey.
“But these lab studies were done in a beaker and we haven’t yet had the opportunity to test this in the real world.
“Scientists are a cautious breed. This is one piece of evidence and we would like to have a weight of evidence before we can say we have a cause and effect.”
Professor Jon Brodie, the chief scientist from James Cook University’s Catchment to Reef Processes research group, said the preliminary research was valuable.
“It again shows that we have pesticides above guideline levels in Queensland streams and particularly near the Great Barrier Reef where I work,” he said.
“That in itself is not news.
“But what this shows is that these sorts of levels can hurt prawns.”
More than 95 per cent of Australia’s prawn industry is in Queensland as prawns prefer water temperatures above 25 degrees.
Australian Prawn Farmers Association president Matt West said the CSIRO research showed pesticides were killing prawn larvae.
“I guess it’s the early stages of alarm bells, if you like, based on the results they have done in a lab,” Mr West said.
“What we are talking about is pesticides in estuaries in run-off from agricultural farms, which appears to be elevating.
“So we are getting mortality with our larvae stages.”
Mr West insisted rigorous annual tests with Queensland’s Department of Agriculture showed no pesticides at all in adult prawns.
“So there is no effect on human health in consuming these animals,” Mr West said.
Fisheries expert Dr Matt Landos said the situation was a “canary in the coal mine situation” for Australia’s prawn and crustacean industry.
“What they found was that at the low levels of these chemicals, in fact at staggering low levels, the prawns stopped eating,” he said.
“We now have the science.”
The CSIRO scientists investigated the impact of three common pesticides – bifenthrin, fipronil and imidacloprid – that they discovered in rivers near Mackay and Logan.
The scientists said all pesticide levels in Queensland’s coastal rivers were increasing as farms shifted from older-style organophosphate pesticides to modern neonicotinoid pesticides, following world trends.
Neonicotinoid pesticides influence receptors in the brains of sucking and chewing insects.
They make up more than 24 per cent of the world’s pesticides and were linked to honey-bee deaths in the United States in the early 2000s.
They are now widely used on Queensland’s cane farms and fruit and vegetable farms, and to control pests.
The CSIRO report found the pesticides had low toxicity to birds and mammals, but higher toxicity to fish and arthropods.
The team of scientists tested the “lethal toxicity” of the pesticides on baby black tiger prawns and found that: “Each of these insecticides was among pesticides detected in some samples collected from shrimp farm intake waters, and at concentrations approaching those that would either impact survival (fipronil) or their feeding rates (bifenthrin and imidacloprid).”
Dr Hook said Queensland’s Department of Environment and Science had decided recently to upgrade water quality guidelines on pesticides, however that could not be confirmed.
A spokesman for Queensland’s Department of Agriculture and Fisheries said the CSIRO research had yet to be evaluated.
“As yet we cannot confirm the accuracy of CSIRO’s conclusions,” the spokesman said.
The Australian Pesticides and Veterinary Medicines Authority described the CSIRO study as an “initial limited study” only.
“The APVMA will continue to monitor and consider any further scientific work on this issue,” a spokesman said.
The APVMA said a review of fipronil began in 2011 because of environmental concerns, while a review of bifenthrin was completed 10 years ago and imidacloprid had never been reviewed.