Freshwater Guardian - Freshwater fishing news from the Department of Fisheries, Western Australia
Issue No. 3, March 2015

The Murray cod controversy

Murray cod (Maccullochella peelii)

The recent capture of a Murray cod (Maccullochella peelii) in a lake in Canning Vale sparked considerable interest in the media and the fishing community.

This was the second location where our researchers doing metropolitan pest fish surveys have captured Murray cod. There's no denying it’s a spectacular fish but it doesn’t belong in the lakes and rivers of Western Australia.

There is considerable risk to the environment from such a large, long-lived (up to 80 years) predatory species. In this instance, the lake where the Murray cod had been released is one of the rare places in the Perth metropolitan area with a population of southwest freshwater native pygmy perch.

Even worse, Murray cod don’t just eat fish and crustaceans; they also feed on turtles, waterbirds and even small mammals. Initial data suggests that the Murray cod recently captured may have contributed to an observed decline in the population of oblong turtles in the lake.

Murray cod are a significant threat to native WA species, particularly marron. To manage this risk, the Department relies on help from the public. We all have a responsibility to protect and preserve our delicate natural environment and you can help by:

  • never releasing noxious fish species in or near waterways (please read our Don’t dump that fish brochure); and
  • reporting any sightings of aquatic pests using WA PestWatch.

Trout – cooler than ever!

Metal roof over trout hatchery ponds

Summertime in a hatchery can be very stressful for both trout (Oncorhynchus mykiss) and staff.  Summer temperatures in Pemberton can be extreme, with water temperatures reaching 28°C or above; too much even for our high temperature-tolerant super trout.

Pond-shading has gone through various designs; from a wisteria tree in the early years, to large timber poles with wire netting, to shade cloth panels during summer.

In 2004, storms ruined the timber structure so a steel-framed roof was built over the eight trout ponds. The four outside trout yearling ponds were only covered by shade cloth panels.

In the summer of 2012/13, extreme hot weather heated the water in the outside ponds to above 28°C, killing many yearling trout but the trout under the steel-framed roof suffered only minor losses.

Yearling trout are a vital part of the annual release strategy, so in November 2014 we invested $85,000 in a new steel roof over the four outside yearling ponds. The young fish will have a much better chance of survival during extreme temperatures and will be available for release during the autumn/winter months.

“You did surgery on a fish?!”

Fish surgery

This is the usual question when people hear about an operation to place acoustic transmitter tags inside native freshwater catfish (Tandanus bosktocki).

The aim was to compare movement patterns of freshwater catfish against environmental variables to inform environmental water planning by the Department of Water.

This project began early in 2013 and was coordinated by the Department of Water with a surgical team (Dr Jo Bannister, Dr Fran Stephens and Paul Hillier) from our Fish Health Laboratory.

Our aquatic animal pathologists usually diagnose disease in various aquatic animals that ‘swim’ into their laboratory, but this project allowed them to exercise their veterinary clinical skills. 

It's simple to insert a tag but having the skills to perform the surgery gently, control the anaesthesia, monitor recovery, reduce infection risk and treat wounds makes all the difference to the patient’s survival.

The surgery places a tiny six millimetre tag into the belly of the fish. Fifty fish were tagged at two south-west sites and, to this day, all 50 are alive and swimming! And in 2015, more will be tagged...

Caught in the act!

Cartons of live fish

Fisheries Officers from our Biosecurity Compliance Section have increased efforts to stop the illegal translocation of live non-native fish.

Officers ran operations at the Perth Domestic and International Airport, with Department of Agriculture and Food WA, and the help of various freight companies.

Over 600 cartons of live fish were inspected, revealing a large variety of ornamental and other live fish, including some for the restaurant trade. In three incidents, live non-native fish were seized and this is likely to result in prosecution.

In one incident, officers detected the illegal movement of arowana and bichir through the domestic airport, then executed a search warrant at the offender’s residence in Perth’s northern suburbs. With the NSW Department of Primary Industries, they are pursuing interstate accomplices.

Anyone translocating live non-endemic fish into WA, or accidentally or deliberately releasing pest fish into the State’s waterways, places our aquatic environment at risk. The correct advice must be obtained from the Department’s Translocation Officer before importing any live fish, or you risk a $10,000 fine.

For the correct disposal of unwanted species, please see our Don’t dump that fish brochure.

Protection for native freshwater fish

Western Trout Minnow

Most species of native freshwater fish are too small to be deliberately targeted by recreational fishers, but we are aware of incidents where they have been used as live bait for redfin perch in south-west rivers and dams.

These local fish are vulnerable, especially to environmental change, and have now been given total protection under fisheries legislation.

Seven species of freshwater fish (including the little pygmy perch, pictured) have now joined the hairy marron on the list of totally protected species.