37 7th Veterinary Report - Department of Primary Industries ...

Silver Perch Larval Malformation,Discoordination and Acute Death Syndrome
1. Silver Perch Larval Malformation, Discoordination and Acute Death (SPMDAD) Syndrome is a complex
fish health disorder within the scope of syndromes described by the Noosa Fish Health Investigation
Task Force. Although there is insufficient pathological data to study the development of SPMDAD in
detail, this epidemiological and toxicological assessment provided a necessary starting point. It is a
significant fish health disorder within the context of agrichemical spray drift risk assessment and
mitigation.
2. SPMDAD is a toxin related and acute condition. This is supported by the observation that activated
charcoal filtration of spawning tank water improved the survival rate of affected fish larvae. SPMDAD
causes severe morbidity and mortality of affected fish resulting in estimated rates of mortality in
fertilised fish embryos of 99%, of malformation in embryos of 25% and of swimming discoordination in
hatched fish larvae of 65%.
3. Spray drift contamination occurred through a breach in the hatchery spray drift biosecurity program by
the opening of the hatchery door in the evenings and through lack of covering over water storage
tanks. This contributed to the contamination of the hatchery air environment and potentially water
used for fish spawning with trichlorphon/dichlorvos and nonylphenol. Both agrichemicals have been
reported to be used recently by the macadamia plantation. However, the actual exposure
concentration to the affected fish eggs and larvae are not known due to lack of water samples from the
hatchery tanks.
4. Nonylphenol has been shown to cause lethal and non‐lethal fish embryonic deformities. Nonylphenol
has been shown to cause hatching failures in Australian native fish. Nonylphenol exposure may explain
the malformation and hatching failure observed. Trichlorphon/dichlorvos are agrichemicals with
neurological toxicities which may explain the swimming discoordination observed. A combination of
toxicities by nonylphenol and trichlorphon/dichlorvos may result in acute death of fish embryos and
larvae.
5. Definitive studies on the toxicity of nonylphenol and trichlorphon/dichlorvos are indicated to provide
risk mitigation information in relation to agrichemical spray drift scenarios for fish hatchery operations.
Summary Risk Assessment Statement
Silver Perch Larval Malformation, Discoordination and Acute Death (SPMDAD) Syndrome can be
explained by agrichemical spray drift contamination into a hatchery environment involving nonylphenol
and trichlorphon/dichlorvos.
The issue of uncertainty is with respect to the actual exposure scenarios and the exposure
concentrations at which silver perch fish eggs, embryos and fish larvae would not experience SPMDAD.
The recommendations of this report are :
A. Spray drift protection measures in a hatchery environment should consider the following risk factors :
o Opening of the door of the hatchery at night time even in the absence of spray activities at night. Day
time spray residue may still be present in the air for an undeterimined period depending on wind
and temperature conditions as well as agrichemical behaviour. Therefore the hatchery door should
be closed with only very short periods of opening for ventilation and other activities.
o All water storage tanks inside the hatchery can be contaminated if the concentration in the air of
agrichemical spray droplets is high enough. Therefore tank covers may mitigate the risk of
contamination in this situation.
o Use and replenishment of activated charcoal filtration of water used in spawning tanks should be a
standard preventative procedure as long as it is applied to treat water prior to exposure of fish eggs
to potentially contaminated water.
Report to Noosa Fish Health Investigation Task Force
7th Veterinary Report
Executive Summary of Veterinary Investigations
Page 16 of 27