The trade in exotic fish presents a continuing challenge for bacteriologists working to keep harmful pathogens out of WA waterways, but experts believe the State's biosecurity efforts are among the best in the country.
The importation of exotic aquarium fish into Australia is worth about $350 million annually, with 15.5 million fish imported in 2005.
The animals can be a source of exotic pathogens, bacteria and disease that cause havoc in Australia's freshwater and marine ecosystems.
Fish imported into Australia are subject to Department of Agriculture, Fisheries and Forestry biosecurity conditions and on arrival are held in quarantine for inspection.
In WA, fish showing signs of disease are sent to the Fish Health Unit at the Department of Fisheries, before bacteriology is conducted at the Department of Agriculture's Animal Health Laboratories.
Animal Health Laboratories expert Nicky Buller said she regularly received samples of suspected exotic pathogens. The samples are analysed and examined for culturing and identification.
"When DAFF biosecurity officers observe significant deaths among quarantined fish, we are supplied tissue samples for identification," Dr Buller said.
"We perform traditional culture procedures and DNA-based methods, but we also have introduced the matrix- assisted laser desorption/ionisation time-of-flight mass spectrometer for identifying samples.
"This technology utilises the proteins on the cell wall which are ionised by a laser beam and separated under vacuum.
"The mass is recorded on a detector and the resulting spectrograph is compared to the database to determine a probability, whether high or low, of it being a certain organism.
"In the last year, we have had a few exotic pathogens detected in quarantine and we have been able to identify them through traditional methods and with this new technology."
"Culturing" involves growing the bacteria for further study, which is a process that can present several challenges for researchers.
Bacteria from marine fish need to be cultured in media containing NaCl (sodium chloride), or magnesium and potassium ions, whereas bacteria from freshwater fish do not required added NaCl.
"It is a challenging task," Dr Buller said.
"You have to be able to recognise potential cases of exotic disease among the endemic cases, bacteria you wouldn't normally see in everyday diagnostics.
"There are also specific temperature and media requirements for different bacteria, and that means knowing what temperature is optimum for culturing."
Dr Buller is urging all West Australians to help reduce the disease risk to Australia's native fish by adopting practices such as disposing of dead aquarium fish in bleach in their household rubbish rather than flushing them down the toilet.This article first appeared at sciencewa.net.au