Don't flush the goldfish! Imported fish are sicker than we knew

If you buy your loved one a Siamese fighting fish instead of a Siamese kitten this Christmas, just remind them that the same rules apply - if the relationship loses its magic, don't abandon your pet to the wild.

"Australia imports an estimated 18 million ornamental fish each year, and some of those pose a disease threat to domestic fish stocks in aquariums, fish farms and even to wild fish," saidDr Joy Becker, a lecturer in theFaculty of Veterinary Scienceat the University of Sydney.

The most popular imported ornamental fish in Australia are goldfish and the brilliantly coloured dwarf gourami, both imported from several countries in Southeast Asia.

There are strict Australian health controls including the requirement for a certificate of good health from the exporting country and quarantine periods for the imported fish.

While we do have success detecting fish disease and excluding those animals it is still a challenge to uncover some serious exotic diseases. One reason is that some of these diseases take longer to emerge than the duration of the imposed quarantine," said Dr Becker.

Dr Becker has researched two diseases in imported fish, dwarf gourami iridovirus (DGIV) and cyprinid herpesvirus 2 (CyHV2). While CyHV2 infects goldfish and is an issue for the domestic industry, it does not infect other species.

Of more concern is DGIV, which affects other fish species and killed Murray cod in Victoria in 2003. DGIV appears to infect both freshwater and marine fish species.

"My research looked at ornamental fish that were newly imported and in quarantine, pet stores and wholesalers. I also looked at domestic ornamental fish in aquaculture farms and in the wild," said Dr Becker.

DGIV was not expected to be present but was found in 20 percent of gouramis still in quarantine and approximately 15 percent of fish at wholesalers, recently released from quarantine. The virus was found in 30 percent of sick gouramis at pet shops and even at a domestic fish farm.

CyHV2 was not only found at wholesalers and fish farms but also in wild fish stocks.

"A major issue of concern is that people liberate their fish into local waterways, including rivers, dams and fountains in public areas, or they flush live fish down the toilet and are doing that in places where our wild fish stocks are at risk," said Dr Becker.

"Fish can survive being flushed, which is one reason we have feral populations of goldfish in many temperate parts of Australia and feral gourami in the northern more tropical waterways in Queensland."

The key message, according to Dr Becker, is not to release your pet fish into the wild and, if giving a fish, to remember that the lifespan of a goldfish or dwarf gourami can be many years.

But individual fish owners are only one part of the problem. "We also need to be more effective at stopping diseased fish entering the country, especially for dwarf gourami iridovirus," Dr Becker said.