Photo: Gunther Schmida

Other common names: European perch, redfin, English perch, Eurasian perch

Introduction

Redfin is a medium sized freshwater fish native to northern Europe. Redfin were first introduced to Australia in the 1860s for angling, and are now widespread across much of NSW, ACT, Victoria, Tasmania, south-eastern South Australia and the south-western corner of Western Australia.

Redfin are popular with some anglers because of their fighting qualities and taste. However, they are also voracious predators of other fish and invertebrates, can destroy recreational fisheries in enclosed waters by building up large numbers of stunted fish and eliminating other species, and can devastate native fish populations by carrying the EHN virus. For these reasons, redfin are considered a serious pest in NSW.

Description & biology

Description: Redfin belong to the family Percidae. They can be recognised by the following features:

• a deep body and a slightly forked tail;
• two distinctly separate dorsal fins, the first with 12-17 strong spines and a distinct black blotch at the rear;
• a pattern of five or more broad black vertical bands across the back, tapering on the sides (more prominent in younger fish);
• bright reddish-orange pelvic and anal fins and tail.

The body colour varies from olive green to grey on the back, fading to greenish or silvery on the sides and whitish on the belly.

Redfin can grow to 60 cm in length and around 10 kg in weight, but are more commonly found up to 45 cm and 1-2 kg.

Habitat: Redfin live in a wide variety of habitats, but prefer still or slow-flowing waters such as lakes, dams, billabongs, swamps and slower moving streams and rivers. They prefer areas with good shelter such as snags (submerged dead wood and trees), vegetation or rocks, but have also been caught in open water.

Feeding: Redfin perch are carnivorous and feed on a wide variety of foods ranging from small invertebrates (such as crustaceans, worms, molluscs and insect larvae) to fish. They are known to hunt fish either solitarily (by ambushing or stalking their prey) or in organised groups. In groups, they herd shoals of small fish until encircled or pinned against the bank; a few of the redfin then chase into the shoal while the majority hold position and prey on fleeing fish. Schools of redfin also use a similar method known as “beating”, where they flush out insects and small fish from weed beds or other shelter into open water, where they become easy prey for waiting redfin. Such methods give them their reputation as voracious predators.

Reproduction: Redfin spawn in late winter and spring, when they lay several hundred thousand eggs in a gelatinous ribbon amongst aquatic vegetation, submerged logs or other sheltered areas. The egg mass is unpalatable to most other fish and is hence generally protected from predation. The eggs develop and hatch in about a week, and the young fish school to help avoid predation. Redfin usually take 2-6 years to reach sexual maturity, but some have been found to be reproductively mature at 1 year of age.

Where are they in NSW?

Redfin are widespread throughout much of NSW and Victoria, particularly the cooler waters on either side of the Great Dividing Range but also into the central parts of each state. They are also known from the ACT, south-eastern South Australia, Tasmania and south-western Western Australia. Their distribution seems to be limited by an upper water temperature of around 31°C and they are rarely found in fast-flowing waters or high altitude areas.

In 2006 the NSW DPI discovered new populations of redfin in the upper part of the Lachlan as well as the Abercrombie and Wollondilly catchments. These areas, which were previously free of redfin, support some of the last known NSW populations of threatened native Macquarie perch and southern pygmy perch.

Known and probable distribution of redfin perch in NSW

NSW Department of Primary Industries and its employees disclaim any liability for an act done on the basis of information in the map and any consequences of such acts or omissions.

Known and probable distribution of redfin perch in NSW

NSW Department of Primary Industries and its employees disclaim any liability for an act done on the basis of information in the map and any consequences of such acts or omissions.

How did they get here?

Redfin were first introduced to Australia in the 1860s for angling. The recently discovered populations of redfin in the upper Lachlan, Abercrombie and Wollondilly catchments appear to have been introduced deliberately, as they are geographically isolated from existing populations and could not have spread naturally.

What are their impacts

Even though redfin have been in Australia for over 100 years, much of the information regarding their impacts is based on personal observations rather than scientific studies.

Redfin are voracious predators which consume a wide variety of fish and invertebrates, including small native species such as pygmy perch, rainbowfish and carp gudgeon, and the eggs and fry of larger fish such as silver perch, golden perch, Murray cod and introduced trout. This predation can seriously impact populations of native species and trout, and hence can also affect recreational fisheries for these species. For example, redfin were recorded as eliminating 20,000 newly released rainbow trout fry from a reservoir in south-western Australia in less than 72 hours.

Redfin are capable of rapidly populating new waterways and in stable water bodies (such as lakes and dams) they can form very dense populations. Under these conditions, redfin become stunted as they deplete the food supply, becoming worthless for angling. In such large numbers, they can also out-compete most other fish species.

One of the most significant threats to native fish from redfin is their potential to spread the viral disease Epizootic Haematopoietic Necrosis (EHN). This disease, which was first isolated in 1985 and is unique to Australia, can cause mass mortality in juvenile redfin perch during the summer months. A number of native species, including silver perch, Murray cod, mountain galaxias and particularly Macquarie perch, are highly susceptible to the disease, and EHN virus may be one factor responsible for the decline in various native species over the last couple of decades.

What is NSW DPI doing?

NSW DPI has an ongoing survey program throughout NSW to gather information on the distribution of freshwater fish species, including introduced pest fish such as redfin. The Department has also undertaken specific surveys to confirm the presence and abundance of redfin in new areas.

NSW DPI has considered a range of options for targeted control and/or containment of redfin to limit the impacts on threatened species. However, as with all pest fish in open waterways, it currently appears to be impossible to eradicate redfin populations or prevent natural dispersal to new areas.

Southern pygmy perch broodstock have been collected from one site under threat from redfin and will be used to form the basis of a conservation stocking program for re-introduction into sites with suitable habitat.

NSW DPI, together with Sydney University, has submitted a joint research application to look further at EHNV disease carried by redfin and the impacts on native species. This project aims to assist management in several ways including determining the extent of EHN distribution in the Murray-Darling Basin, developing tests to detect presence of EHN antibodies in native fish, assisting the selection of EHN resistant broodstock for conservation stocking activities, and informing the development of EHN containment policies.

The Hawkesbury-Nepean Catchment Management Authority is funding a NSW DPI project to look at options for excluding redfin from Macquarie perch habitats in that catchment, in response to new redfin populations in the Wollondilly River.

NSW DPI has also commenced an awareness raising campaign to alert anglers to the problems this fish can cause. The campaign has involved producing an educational poster (“Say no to feral fish: redfin perch”) which has been sent to all NSW fishing licence agents and recreational fishing clubs throughout NSW.

How can you help

• Don’t transfer redfin between waterways or introduce them into farm dams. New populations of redfin can quickly build up to large numbers, leading to stunted fish which are poor angling and poor eating and replace other recreational species.
• Don’t use live redfin (or any other live finfish) as bait in freshwater - it’s illegal and carries a high risk of infesting new areas with redfin.
• Obtain a permit to stock fish – and buy fingerlings from a registered hatchery to prevent contamination with unwanted species.
• Don’t return redfin to the water – large redfin are good sport and eating fish and there are no bag or size limits on them. Please keep ALL redfin you catch and don't release them into our waterways or dams.
• Prevent unwanted hitchhikers – check, clean, and dry boats and gear between waterways. Ensuring your boat and trailer are free of weed before re-launching can help avoid the possibility of spreading redfin eggs and juveniles.
• Assist efforts to restore our rivers (which can help native fauna to out-compete redfin and other pest fish), for example by taking part on a RiverCare or LandCare project or by conserving and restoring riparian vegetation on your own land.
• Take part in native fish restocking programs with your local angling group.

If you find what you believe is a redfin perch Report it!