In late April the Inland Fisheries Service (IFS) received a report from Launceston angler Logan Reid who caught a large redfin perch (Perca fluviatilis) in Four Springs Lake. This capture was of concern given Four Springs Lake is thought to be free of redfin perch, however they are present downstream of the lake.

The perch was frozen and handed to the IFS for further investigation. It measured 410 mm (fork length), weighed 1.4 kg, and was a mature female holding 95 g of eggs. The ear bones of the fish (otoliths) were removed for age analysis, and it was found to be nine years old (processed and aged by IMAS researcher Pete Coulson).

Based on this information, in early May the IFS conducted an extensive two-day survey, consisting of boat electrofishing, box trapping, and fine mesh fyke netting.

Despite the intensive effort, no redfin perch were found, suggesting a population is not established. Further details on this survey will be published in a separate news article.

While the source of the single fish is unknown, the survey results and size/age of the fish suggest this capture is a ‘one-off’ that entered the lake a long time ago and has managed to avoid capture since.

In addition, previous surveys of the lake undertaken in recent years, and the high angling pressure experienced each season, provide strong evidence that a redfin population has not established.

However, the IFS is asking anglers to remain vigilant and report any suspected sightings (or captures) when the new brown trout season commences on Saturday 2 August 2025. Take a photo of the fish, or carcass if found and if possible, retain it.  Please take note of the location where any suspect fish were seen (or caught), as well as the date, and contact the IFS promptly on 1300 INFISH or infish@ifs.tas.gov.au

The IFS is planning additional monitoring work in Four Springs Lake, including a redfin perch eDNA survey to confirm the initial survey results.

Redfin perch are an invasive species introduced to Tasmania in the 1860’s, and are now established in many areas of the state. Due to their aggressive nature and ability to reproduce rapidly and overpopulate water bodies, they pose a threat to our native fish and trout. Anglers can help reduce the spread of pests in Tasmanian waterways by not transferring fish between waters. Offences may incur significant penalties.

The IFS would like to thank Logan for the prompt reporting of the capture.