Christmas may be a season for visiting the neighbours, but Territorians are being urged not to let their pond fish do the same.

The Department of Primary Industry and Resources is issuing a reminder that large wet season downpours can lead to overflowing fishponds, which can result in non-native pond fish being washed into our creeks and rivers.

Aquatic Biosecurity Officer Dave Wilson said that for local fish populations, exotic fish like guppies and oscars were very unwelcome visitors.

“For many Territorians there is little better than a downpour that has your gutters and pool overflowing,” he said. “But an overflowing pond or outdoor aquarium is a problem.

“Once non-native fish find their way into waterways, they can reproduce in large numbers, compete for food and space, change the habitat and even eat the native fish.”

“They can also introduce disease and parasites into a healthy system, which can be devastating to the native fish populations,” he said.

But Mr Wilson said the solutions were quite simple.

“All you have to do is make sure that your pond has a screened overflow or spillway that stops fishing coming out with any excess water,” he said.

“The other option is to stock your pond with native fish instead. Many people don’t realise that there are some beautiful native fish varieties which are fantastic for ponds.

“Fish like blue-eyes, rainbow fish, glassfish and gudgeons are hardy. The smaller species eat mozzie wrigglers but not tadpoles and if they do happen to wash away, they are less likely to affect local fish populations in creeks and rivers.”

He said the other risk from overflowing ponds was the spread of exotic pond plants like Cabomba and Sagittaria platyphylla (also known as Sagittaria, delta arrowhead and broad leaf arrowhead).

“Not only can these species choke up waterways, but they can also be vectors for other problems,” he said. “They can hold algae, snail eggs, fish eggs and other insect pests.”

Mr Wilson said holidaymakers should not be tempted to set their pet fish free.

“Definitely don’t dump any fish from tanks and ponds back into local waterways and public ponds. If you can’t get a friend to look after them while you’re away, contact a local pet shop to see if they will take them.”

To find out more, or if you think you’ve spotted something that shouldn’t be there, take a photo, catch a sample if possible, call the Fishwatch Hotline on 1800 891 136 or report it on the NT Fishing Mate app (https://nt.gov.au/marine/recreational-fishing/get-the-free-fishing-mate-app).

Media contact: Lucy Buhr 0419 106 309