Freshwater Guardian - Freshwater fishing news from the Department of Fisheries, Western Australia
Issue No. 4, July 2015

Native fish return to Lake Marmion

Lake Marmion is now ready for native fish

Exciting news! This month marks the successful end to a three-year project focused on the complete removal of a pest fish from Lake Marmion in Myaree. With support from the Minister for Fisheries, the Hon Ken Baston, two species of native fish were released back into the lake. 

The smooth criminal

Endangered hairy marron

On-ground action funded by the South West Catchments Council (SWCC) has enabled us, with help from the Cape-to-Cape Catchments Group and volunteers, to fish out more than 1,400 invasive marron from Margaret River.

Since their introduction into the river in the early 1980s, smooth marron have decimated the endemic hairy marron population for reasons largely unknown. Hairy marron are now only found in a number of small pools in the Margaret River where marron fishing is strictly banned.

Baited black box traps were used to remove the smooth marron and give the hairy marron a chance of recovering. Participants in the community-driven fish-out used a trial identification guide that we are developing to determine whether the marron were hairy, smooth or a cross between the two.

After 20 nights of sampling, catches indicated that almost all non-hairy marron of breeding size had been removed from the pools. With broader implementation, this method will hopefully give hairy marron a better chance of breeding success, with the aim of ultimately saving the species from extinction.

SWCC, a member of the Hairy Marron Recovery Team, recently provided funding for the completion of a new recovery plan which identifies recent advances in our understanding of the biology, ecology and ultimately the conservation of hairy marron.

To see a hairy marron for yourself, visit Perth Zoo to view a display of WA’s most iconic freshwater animal.

Don't dump that fish!

The release of ornamental fish is thought to be responsible for 22 out of the 34 species of pest fish known to be established in the Australian freshwater environment.

Unfortunately, many ornamental fish have also been released into the WA aquatic environment. Some of these species, including the pearl cichlid and Mozambique tilapia, have spread rapidly and now dominate some water bodies.

To encourage people not to release aquarium fish, Fisheries and the Swan River Trust have recently released a video about the Don’t Dump That Fish campaign to help protect WA’s unique freshwater environment.

Marron worms identified

Round white cysts encasing worms are clearly visible in the marron.

In January, our freshwater ecosystems and fish health teams investigated a public report of cysts being found in dam-caught marron.

Our research staff found sampled marron to have multiple round white cysts in their flesh which, when dissected, were found to contain worms.

Internationally-respected worm expert, the University of Queensland’s Dr Tom Cribb, preliminarily identified the worm as a species of trematode belonging to the Choanocotyle genus. The Fish Health Laboratory analysed the worm’s DNA and confirmed this identification. 

Trematode worms have an unusual and complex life cycle; growing in one or two intermediate hosts and then transferring to a final host animal to become adults and repeat the cycle. Likely hosts for this worm are aquatic snails, marron and turtles. All these hosts need to be present for the worm to complete its life cycle and proliferate.

This worm may have gone undetected in WA for years. An environmental change may have increased the number of host species causing the worms to become more widespread and detectable. Currently, there is no evidence that the worms pose a danger to human health, even if eaten.

The next steps for our laboratory will be to identify and confirm the hosts involved and to characterise the worm's other life stages. This will help to develop advice and strategies to manage this parasite.

You can help protect our environment by reporting any suspected fish pests or diseases, such as these worm cysts, to FishWatch on 1800 815 507.

Aquaponics - it's fishilicious!

Delicious thriving crops can be raised in the aquaponic system

Aquaponics, a blend of aquaculture and hydroponics that grows both fish and plants for personal consumption, is an increasingly popular hobby.

It works by pumping rich nutrients excreted by fish through a connected hydroponics system, where these are broken down by bacteria to provide organic food for plants. The water is then recirculated into the aquaculture system with a lower level of ammonia, making it more tolerable for the fish.

In WA, you need to obtain translocation approval to practice aquaponics with the list of permitted species including barramundi, silver perch and trout. If you keep fish for a commercial purpose, an aquaculture licence is also required.

Aquaponicists in WA cannot translocate some eastern state species such as Murray cod and jade perch, as they pose a threat to our own native and endemic freshwater fish. No fish should ever be released from any aquaculture system, including aquariums, into any natural water ways – see the Don’t Dump That Fish article above.

Aquaponics is a great way to grow your own organic vegetables, fruit, herbs and fish and, if done with biosecurity in mind, can also help reduce the spread of pests and diseases into our waterways.


In our March issue, we published a picture of a Western pygmy perch (Edelia vittata) instead of a little pygmy perch (Nannoperca pygmaea) (pictured). It is the little pygmy perch that is critically endangered and on the list of protected freshwater species.

Also in our March issue, please note that the image used in the 'Caught in the act' story is representative only – Fisheries Officers did not find any noxious listed or illegally imported fish in the boxes shown in the photo.

Image credit: Little pygmy perch photo by David Morgan.