Platies (Xiphophorus maculatus) are a popular aquarium fish that have become a pest in some Queensland waterways due to people deliberately (or accidentally in the case of backyard ponds) releasing them.

Platies spread between water bodies during flood events (like the one in February/March 2022). Recent monitoring discovered platies established in two creeks on the west coast of K’gari – Bogimbah and Poyungan.

Growing to around 6cm, they are a stout fish with rounded dorsal (upper) and tail fins and an upturned mouth. In aquariums, they are highly variable in colours, but in the wild, they are generally yellow-olive brown with 2–5 distinct bars along their body.

Native to Central America, platies are now established in many areas including Hawaii, the United States, Puerto Rico, Palau, Madagascar, Jamaica, Columbia, Sri Lanka, Bahamas, and Australia (particularly in coastal drainage around Brisbane and in the Wet Tropics region in North Queensland).

Classified as potential pests in countries where they have been introduced, platies will compete with native fish for food and space, dominating waterways due to their high ability to reproduce and survive in habitats not suitable for native fish. This is particularly problematic for K’gari, which supports several species of threatened fish including the Endangered Oxleyan pygmy perch (Nannoperca oxleyana), Vulnerable honey blue-eye (Pseudomugil mellis), and ornate rainbowfish (Rhadinocentrus ornatus).

Platies love warm springs, canals and ditches with slow-moving water, silty bottoms and weedy banks and can survive in waterways that are too degraded for native fish. Reaching sexual maturity after only 3-4 months, platies reproduce frequently and in high numbers giving birth to live young. The fish are omnivorous, feeding on any available food source including worms, crustaceans, native fish eggs and fry, insects, and plant matter. 

Platies are certainly NOT welcome on K’gari. So, what do you do if you find a platy?

If you catch platies in the wild, humanely kill them and do not return them to the water. Report all invasive fish captures through the Department of Agriculture and Fisheries’ online reporting form. Take photos, if possible.

For anyone looking for a place to dispose of unwanted aquarium fish, please give them to your friends or a pet shop rather than letting them go in the wild. Releasing live fish into Queensland waters is illegal as a breach of your general biosecurity obligation under the Biosecurity Act 2014. Under the Biosecurity Act 2014 everyone has a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with spreading or introducing pest fish. This includes any fish that is not native to Australia.

Article contributed by Sue Sargent, FINIA