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Southern Pygmy Perch (Nannoperca australis)

The Southern Pygmy Perch is a small, laterally compressed freshwater fish of slow-flowing streams, wetlands, billabongs, floodplains and farm dams in south-eastern Australia. It relies on dense aquatic and fringing vegetation, shallow refuge habitat and suitable flow connections, so clearing, wetland drainage, sedimentation, altered flows and introduced fish can affect populations on or near development sites. The Murray-Darling Basin lineage is listed as Vulnerable under the EPBC Act, while the species across its full national range was assessed as not eligible for national listing in the 2021 listing advice.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

Victoria, Flora and Fauna Guarantee Act 1988: Vulnerable.

Breeding season

Timing varies between regions and water regimes. The calendar below is a practical summary for south-eastern Australian populations, with Murray-Darling Basin breeding generally later and warmer than some Tasmanian observations.

Seasonal timing is not uniform across the full national range. Avoid relying on a calendar alone. Confirm local water temperature, flow, aquatic vegetation and recent fish records before clearing or dewatering.

  • Breeding: Spawning generally occurs from September to January. It has been recorded above 19 degrees Celsius in the Murray-Darling Basin and from 15 to 18 degrees Celsius in Tasmanian observations.
  • Eggs and larvae: Eggs hatch after 66 to 79 hours, or about three days. Eggs are scattered over aquatic vegetation and larvae are about 3 to 4 mm long at hatching.
  • Young fish and recruitment: Young fish remain close to aquatic cover. In the Barmah-Millewa Forest, juveniles recruited mainly from November to February, and recruitment could continue into May in Tasmania.
  • Floodplain movement and dispersal: Movement, recruitment and dispersal increase when spring and summer floodplain inundation connects creeks, wetlands, lakes and billabongs. Timing depends on rainfall, managed environmental water and local flow conditions.
  • Dry-period refuge use: Refuge use can occur in any month during drought or prolonged low flow. Risk increases when wetlands and shallow floodplain habitats dry, as recorded during the 2007 to 2008 Barmah-Millewa study period.
  • Highest clearing risk: Clearing or aquatic disturbance is most likely to harm the species from September to December, when adults spawn, eggs and larvae are present and dense aquatic vegetation is being used. Risk can extend into February or May where juveniles remain dependent on cover or where floodplain recruitment is occurring.

Identification

Southern Pygmy Perch is a very small native fish that is usually found within dense aquatic cover. Identification in Victoria and South Australia can be difficult because several pygmy perch species occur in the same region.

The body is laterally compressed. The back and sides range from cream, gold-orange or greenish-brown with mottling, and the belly is silver white. Fins are generally clear to dusky. Breeding males develop bright red to black colouration in the fins, particularly towards the fin bases.

Body length: Maximum recorded size is 85 mm; fish are rarely more than 65 mm.

Body shape: Small, laterally compressed and perch-like.

Breeding male colour: Bright red to black fin colouration.

Identification: Features for field identification

The species has a deep notch in the single dorsal fin. South Australian guidance describes a relatively large mouth and round eye pupil compared with Yarra Pygmy Perch. The lower edge of the preorbital bone is smooth and not serrated, which separates Southern Pygmy Perch from the closely related Yarra Pygmy Perch when examined by a suitably trained fish specialist.

  • Use an experienced freshwater fish ecologist or taxonomist where Southern Pygmy Perch may occur with Yarra Pygmy Perch or other pygmy perch species.
  • Do not rely on colour alone, because colour varies and breeding male colouration is seasonal.
  • Photograph live fish and record the site, habitat, waterbody type and capture method before release, subject to the relevant permit and animal ethics requirements.

Identification: Field signs and detection

There are no documented tracks, scats, calls, nests, sloughs or eyeshine to search for. Field detection depends on capturing or observing fish in shallow, vegetated water. The species can be cryptic within dense weed and woody cover.

  • Inspect shallow backwaters, billabongs, wetlands, farm dams and slow-flowing creek margins with dense submerged, emergent or overhanging vegetation.
  • Use methods selected by an appropriately authorised fish surveyor. Victorian surveys have used electrofishing, fine-mesh seines and collapsible or concertina traps, with traps useful where dense weed prevents effective seining.
  • Treat non-detection cautiously where habitat is dense, water is turbid or sites have recently dried, because absence from a single sample does not establish local absence.

Distribution: National range

The species occurs across south-eastern Australia in three broad regions: the southern Murray-Darling Basin, coastal catchments of South Australia and Victoria, and northern Tasmania. Populations are patchy and often separated between tributaries and catchments.

In New South Wales, the historical range included the Lachlan, Murrumbidgee and Murray catchments. Remnant Murray-Darling Basin populations occur in tributaries of the Lachlan and Murray systems, including Blakney Creek, Coppabella Creek and the upper Billabong Creek catchment. The species is considered locally extinct in the Murrumbidgee catchment and in parts of the lower Murray system.

In Victoria, records and remnant populations occur in the Mitta Mitta, Kiewa, Ovens, Goulburn-Broken, Campaspe, Avoca and Wimmera catchments. The Loddon catchment appears to have lost the species. The Campaspe catchment, especially upstream of Lake Eppalock and around Jews Harp Creek, has been identified as a relatively strong Victorian area.

In South Australia, the species occurs in tributaries draining the Mount Lofty Ranges into the lower Murray and Lower Lakes, including the Angas, Finniss and Tookayerta systems and Hindmarsh Island. It also occurs in coastal South Australian catchments. In Tasmania, it occurs in northern catchments from Doctor's Creek to the Anson River, including the Macquarie catchment. It also occurs on King Island and Flinders Island.

Elevation: Recorded from lowland to upland zones in the Murray-Darling Basin, approximately 0 to 580 m above sea level; Tasmanian records extend to about 300 m.

Broad regions: Southern Murray-Darling Basin; coastal South Australian and Victorian catchments; northern Tasmanian catchments; King Island and Flinders Island.

Distribution: Strongholds and subpopulations

Murray-Darling Basin populations are strongly structured between catchments, with little or no migration between many catchments. Connectivity can occur within streams, but nearby tributaries may hold genetically isolated populations.

In New South Wales, only three remnant natural populations were known outside the Murray River in the 2021 assessment: Blakney Creek in the upper Lachlan catchment, Coppabella Creek near the upper Murray, and the upper Billabong Creek catchment. A translocated population was established in Pudman Creek, where fish survived and recruited but had not spread by 2013.

In Victoria, fragmented populations have been especially associated with the granite creek country of the Strathbogie Ranges and the upper Avoca River. Coastal Victorian populations have been described as relatively robust, although survey coverage is uneven.

Known New South Wales remnant populations outside the Murray River: Three natural remnant populations were identified in the 2021 Murray-Darling Basin assessment.

Blakney Creek change: Distribution contracted by 51 percent in stream length between 2007 and 2013; later monitoring recorded very low abundance and increasing Redfin distribution.

Lower Lakes: Abundance and geographic distribution increased gradually after the Millennium Drought, although the species remains locally extinct in parts of the lower Murray River channel.

Distribution: Population trend

The national population size is not known. The species has declined substantially in parts of the Murray-Darling Basin, with local extinctions and severe fragmentation, while some Victorian and coastal populations persist and some South Australian Lower Lakes populations have increased after drought.

A five-year study in the Barmah-Millewa Forest caught 96 fish. More than half were caught during the 2005 to 2006 season, when prolonged spring and summer inundation occurred. No fish were caught in 2007 to 2008 after many floodplain sites dried.

Barmah-Millewa study catch: 96 Southern Pygmy Perch over five years, including 50 during 2005 to 2006.

Murray-Darling Basin trend: A population reduction greater than 30 percent over the assessed ten-year period was inferred for the Murray-Darling Basin lineage.

National mature population: No reliable national estimate is available; the listing advice considered it likely to exceed 10,000 mature individuals across the full national range, but this was not a measured total.

Habitat: Waterbodies and vegetation

Southern Pygmy Perch occupies shallow, low-gradient freshwater habitats with little flow, especially where aquatic vegetation and woody cover are dense. Habitats may be permanent or seasonally connected to floodplains, but isolated populations need persistent refuge water during dry periods.

Typical habitat includes slow-flowing creeks, backwaters, billabongs, floodplain wetlands, lagoons, lakes, tributary streams and farm dams. Fish are usually associated with shallow margins containing submerged, emergent or overhanging vegetation, algae, pond weeds, water ribbon, club rush, Typha, grasses and woody debris.

Dense macrophytes provide living space, feeding surfaces, spawning substrate and cover from predators. Shaded riparian margins and complex snags can add cover, particularly where aquatic plant growth is limited.

  • Map all aquatic vegetation, woody debris, shallow margins, backwaters and connected wetlands before clearing or construction.
  • Maintain undisturbed vegetated buffers around occupied or potentially suitable waterbodies and avoid stock access where it damages the margins.
  • Keep aquatic plants and woody cover intact unless removal is required for an approved recovery or habitat management action.

Habitat: Hydrology and water quality

The species prefers waters with salinity below 3.3 ppt. It tolerates a broad temperature range and very low dissolved oxygen, but remains dependent on suitable shallow refuge habitat and sufficient water persistence.

Floodplain inundation increases recruitment and dispersal. In the Barmah-Millewa Forest, recruitment and the number of occupied sites increased during prolonged spring and summer inundation. Conversely, prolonged drying can cause local catastrophic mortality.

  • Prevent sediment, concrete washout, hydrocarbons and other pollutants from entering occupied or connected waterbodies.
  • Avoid works that drain, isolate or rapidly dewater wetlands, billabongs, farm dams or shallow refuge pools.
  • Assess both direct aquatic impacts and changes to lateral connections between creeks, rivers, wetlands and floodplains.

Habitat: Elevation and regional setting

Within the Murray-Darling Basin, the species occurs from lowland to upland zones, approximately 0 to 580 m above sea level. Tasmanian records extend to about 300 m. Its distribution is centred on temperate south-eastern Australia, with populations also present in coastal catchments and islands.

Murray-Darling Basin elevation range: Approximately 0 to 580 m above sea level.

Tasmanian elevation record: About 300 m above sea level in the Macquarie River catchment.

Foraging habitat: Food

Southern Pygmy Perch feeds within aquatic vegetation, on submerged surfaces and around shallow cover. It is insectivorous and planktivorous rather than a plant-eater.

The diet includes amphipods and ostracods associated with the bottom or aquatic plants, together with cladocerans and copepods. It also takes larval chironomids and mayflies, adult hemipterans and other terrestrial insects that fall onto the water. South Australian guidance describes the species as taking small macroinvertebrates from underwater surfaces.

  • Retain aquatic plants, submerged wood and shallow edge cover that support small crustaceans and aquatic insect larvae.
  • Prevent sedimentation and turbidity that can smother feeding surfaces and reduce aquatic invertebrate habitat.
  • Avoid pesticide or other contaminant discharges to occupied waterbodies and connected wetlands.

Foraging habitat: Where it feeds

Foraging occurs among submerged and emergent plants, around snags and on shallow underwater surfaces in still or slow-flowing water. Floodplain inundation can increase food and habitat availability, support juvenile growth and allow fish to spread through newly connected sites.

  • Prioritise shallow vegetated margins, backwaters and inundated floodplain habitat when assessing potential foraging habitat.
  • Do not assume that open water without visible fish is unsuitable, because individuals may remain within dense weed or woody cover.
  • Survey connected off-channel habitat as well as the main creek or river channel.

Foraging habitat: Foraging range

  • No species-specific foraging range or home-range measurement was provided in the supplied documents.
  • Assess foraging habitat at the scale of the occupied waterbody and its connected backwaters, wetlands and floodplain margins rather than using a fixed terrestrial radius.

Breeding habitat: Breeding biology

Breeding is associated with rising water temperature and dense aquatic vegetation. Floodplain inundation can improve recruitment and dispersal, but spawning itself can occur in vegetated shallow water without a major flood.

Females scatter demersal, transparent, spherical and essentially non-adhesive eggs over aquatic vegetation. Spawning has been recorded from September to January, with Murray-Darling Basin spawning generally reported when water temperatures rise above 19 degrees Celsius. Tasmanian observations recorded spawning from October to December at 15 to 18 degrees Celsius. In the Barmah-Millewa Forest, juveniles were spawned around October and young fish recruited mainly from November to February.

Breeding season: Generally September to January; October is a documented peak in the Barmah-Millewa Forest. Tasmania records include October to December.

Spawning temperature: Above 19 degrees Celsius in the Murray-Darling Basin; 15 to 18 degrees Celsius in the Tasmanian observations.

Egg number: Reported female counts range from 78 eggs in a 37 mm fish to 4,217 eggs in a 57 mm fish.

Egg type and incubation: Demersal, transparent, spherical and essentially non-adhesive; hatching occurs after 66 to 79 hours, or about three days.

Larval size at hatching: Approximately 3 to 4 mm long.

Age at maturity: Usually by the end of the first year or during the second year; both sexes matured in the first year in one Tasmanian study.

Lifespan: Individuals may live to at least 3 to 5 years, with populations commonly dominated by fish aged 1 to 3 years.

Breeding habitat: Breeding habitat features

Spawning is likely to occur in dense macrophyte beds. Floodplains and inundated wetlands can provide nursery habitat, and young fish remain close to cover. In the Barmah-Millewa Forest, prolonged spring and summer inundation was associated with higher recruitment, faster juvenile growth and occupation of more sites.

  • Protect submerged, emergent and fringing vegetation during the breeding season and through the juvenile period.
  • Maintain shallow, low-flow or still-water habitat with suitable plant cover and nearby refuge pools.
  • Retain hydrological connections that allow adults, larvae and juveniles to use inundated floodplain habitat and later return to persistent water.

Sheltering habitat: Cover and refuge habitat

The species shelters within dense aquatic vegetation, woody debris and shallow refuge pools. It does not construct nests, burrows or dens.

Important cover includes submerged plants, algae, pond weeds, emergent plants, overhanging grasses, water ribbon, club rush, Typha, rocks and snags. Deep pools and backwaters can provide refuge during drought and after sedimentation has reduced shallow habitat.

Juveniles remain close to aquatic cover. Adults and juveniles may occupy floodplain wetlands, creeks, lakes and farm dams when these retain suitable vegetation and water.

  • Retain dense aquatic and fringing vegetation, snags and refuge pools within and beside the work area.
  • Fence or otherwise exclude stock from occupied margins where trampling or grazing removes cover.
  • Avoid sediment deposition that fills deep pools and backwaters or removes permanent refuge water.

Sheltering habitat: Dry-period refuges

Prolonged drought can dry floodplain wetlands and cause severe local losses. During the 2007 to 2008 dry period in the Barmah-Millewa Forest, many sites dried completely and emergency watering and relocation from drying pools to more permanent refuge areas were undertaken.

  • Identify permanent pools, farm dams and other refuge water before works begin in dry periods.
  • Do not pump, drain or isolate refuge water without a species-specific risk assessment and the required approvals.
  • If fish are at risk from unavoidable dewatering, obtain advice from the relevant state fisheries or threatened species authority before capture or relocation.

Sheltering habitat: Structures not used

No dens, burrows, hollows, roosts, nests, tracks, scats or other terrestrial shelter structures are known for this fish. No shelter size threshold was provided in the supplied documents.

  • Assess aquatic cover and water persistence rather than terrestrial refuge features.
  • Use aquatic habitat mapping and fish survey methods where potential habitat is present.

Threats: Clearing and habitat loss

The main risks are loss of aquatic and riparian vegetation, isolation of waterbodies and floodplains, altered flow, sedimentation and introduced fish. These risks are amplified because many populations are small, fragmented and genetically distinct between catchments.

Removal of riparian or aquatic vegetation can eliminate feeding, shelter and spawning habitat. Clearing, unrestricted stock access, wetland drainage, levees and urban or agricultural development have reduced suitable habitat. Even small losses may affect remnant populations where neighbouring streams are not well connected.

  • Avoid clearing aquatic plants, emergent edge vegetation, snags and shaded riparian margins.
  • Prevent machinery access through shallow margins, wetlands and occupied creek beds.
  • Use exclusion fencing and clearly marked no-go areas around aquatic habitat during construction.
  • Restore native riparian and aquatic vegetation where disturbance cannot be avoided, using local advice on suitable species such as Vallisneria where appropriate.

Threats: Fragmentation, roads and infrastructure

Dams, weirs, levees, culverts and regulators can interrupt movement between streams, billabongs, wetlands and floodplains. Reduced lateral connectivity limits breeding, recruitment, dispersal and recolonisation. The supplied documents do not provide a species-specific road mortality rate, but road crossings can create risks through culvert barriers, sediment runoff, dewatering and loss of vegetated margins.

  • Survey upstream and downstream of road crossings, culverts, bridge sites and waterway crossings where suitable habitat occurs.
  • Design crossings to retain water depth, aquatic cover and movement pathways, and prevent construction sediment entering the waterway.
  • Assess temporary access tracks, cofferdams, pumps and drainage changes as potential aquatic barriers or mortality risks.
  • Maintain or restore lateral connections to wetlands and floodplains where the project affects them.

Threats: Hydrology and sediment

River regulation has reduced the timing, frequency and magnitude of natural floods in the Murray-Darling Basin. Drought, reduced rainfall, increased evaporation and altered water levels can dry wetlands and remove refuge habitat. Erosion and sedimentation can fill pools, reduce water depth and degrade aquatic plant habitat. Bushfire ash and sediment slugs can affect waterways downstream of burned areas.

  • Maintain environmental water requirements and avoid unapproved changes to low flows, ponding, floodplain inundation or wetland drainage.
  • Use effective erosion and sediment controls before earthworks, particularly near ephemeral or seasonally connected waterways.
  • Protect deep pools, backwaters and permanent refuge habitat from infilling or dewatering.
  • After fire or vegetation removal, inspect downstream waterbodies for ash, sediment and water-quality impacts before works continue.

Threats: Introduced fish

Redfin and Brown or Rainbow Trout prey on Southern Pygmy Perch. Eastern Gambusia can eat eggs and juveniles, nip fins and has been observed attacking juvenile Southern Pygmy Perch. Carp and Goldfish increase turbidity and damage submerged macrophytes, reducing habitat and potentially competing with or indirectly harming the species.

  • Do not move water, fish, aquatic plants or equipment between catchments without appropriate biosecurity controls.
  • Record introduced fish observed during aquatic surveys and report them through the relevant state system.
  • Do not return captured Redfin or other declared pest fish to the water where state rules prohibit release.
  • Prevent temporary works from creating warm, isolated pools that favour introduced fish or concentrate predators.

Threats: Fire and climate-related events

Bushfire can increase water temperature, alter water chemistry and deliver ash and sediment to streams. More intense fire seasons, changing rainfall, drought and reduced runoff are expected to place additional pressure on isolated freshwater populations. The species is especially vulnerable where a catchment contains only one or a few small populations.

  • Protect riparian vegetation and permanent refuge pools during fire mitigation and post-fire works.
  • Stabilise burned or cleared soil before rainfall where runoff could enter occupied waterways.
  • Include drought, flood, fire and water-quality contingencies in project environmental management plans.

Threats: Disease and handling

The supplied documents do not identify a specific disease as a major threat. Handling, capture and relocation can still spread aquatic pathogens or injure fish if biosecurity and animal welfare procedures are not followed.

  • Use clean, disinfected equipment between waterbodies and follow state aquatic biosecurity requirements.
  • Obtain the required permits and specialist advice before any capture, salvage, translocation or release.
  • Minimise handling time and keep captured fish in suitable, oxygenated water while awaiting identification or release.

Survey methodology: 1. Targeted aquatic sampling

Southern Pygmy Perch is a small freshwater fish, usually less than 65 mm and up to 85 mm long. Surveys must focus on slow flowing or still water with dense aquatic or overhanging vegetation, woody debris, shallow wetlands, billabongs, farm dams and floodplain habitats.

Use an experienced freshwater fish ecologist to survey retained and potentially affected waterbodies, including pools, backwaters, wetlands, billabongs, farm dams and slow flowing creek margins.

Electrofishing has been used successfully in Victoria. Use fine mesh seines where vegetation and access allow, and use collapsible or concertina traps in dense weed where seining is ineffective.

Southern Pygmy Perch can be confused with other pygmy perches in Victoria and South Australia. Have an experienced ichthyologist confirm identifications, especially where Yarra Pygmy Perch or other pygmy perches may occur.

Maximum recorded length: 85 mm

Preferred salinity: Less than 3.3 parts per thousand

Preferred habitat: Slow flowing or still water with aquatic macrophytes or wood at shallow depths

  • Sample aquatic vegetation, woody debris, shallow margins and backwaters rather than relying only on open water.
  • Record the waterbody, coordinates, water depth, flow, water quality, salinity, aquatic vegetation, overhanging vegetation, snags, bank condition and connections to wetlands or floodplains.
  • Use methods that minimise damage to macrophytes and release non-target native fish promptly, in accordance with the relevant permit and animal ethics requirements.

Survey methodology: 2. Seasonal and hydrological timing

Plan surveys in spring and summer when fish are active and spawning or recruitment may be detected. In the Murray-Darling Basin, spawning can occur above 19 degrees Celsius and as early as September.

Give priority to periods following suitable inundation of floodplain wetlands, where safe and practicable. Recruitment and dispersal increased during floodplain inundation at Barmah-Millewa Forest.

Also survey during dry conditions where works may affect refuge pools, because drying can concentrate fish or cause catastrophic mortality in isolated wetlands.

Murray-Darling Basin spawning period: May begin in September, with spawning associated with water temperatures above 19 degrees Celsius

Published floodplain study period: Monthly sampling from mid-September to the end of February over five years

Floodplain study effort: Eleven sites, including four creeks, two lakes and five smaller wetlands

  • Survey aquatic vegetation and shallow floodplain habitat from September to January where the program is intended to detect spawning habitat or young fish.
  • Do not treat a failed survey during dry conditions as proof of absence if the habitat has recently dried, access is poor or the waterbody is disconnected.
  • Repeat surveys across contrasting hydrological conditions where the project may affect a waterbody that is intermittently connected to a river or floodplain.

Survey methodology: 3. Traps, electrofishing and detection interpretation

A published Barmah-Millewa study used modified quatrefoil light traps and sweep net electrofishing. It used five replicate samples of each method at each site, or three replicates in smaller wetlands.

Use the published effort as a project planning reference where comparable floodplain habitat is affected, and adapt the method to waterbody size, access, safety and permit conditions.

Interpret non-detection cautiously. The species is small, cryptic and strongly associated with dense cover, and many sites in the published study dried completely during drought.

Published trap and electrofishing effort: Five replicates of each method at each site, reduced to three replicates in smaller wetlands

Published survey result: Ninety-six fish were collected over five years, with no fish collected in the final year when most wetland sites were dry

Survey methods identified in guidance: Electrofishing, fine mesh seines, collapsible traps and concertina traps

  • Inspect and sample dense submerged, emergent and fringing vegetation, because the species feeds, shelters and spawns in or near aquatic plants.
  • Use traps or fine mesh methods in dense weed where electrofishing or seining would damage habitat or give poor coverage.
  • Record sampling gear, replicate number, duration, area sampled, waterbody length or area inspected, water level, flow and vegetation density so that detection effort can be assessed.

Survey methodology: Minimum effort and reporting

  • Engage a freshwater fish ecologist and, in Victoria or South Australia, arrange expert identification where pygmy perch species could be confused.
  • Survey every waterbody, wetland connection, refuge pool and damp depression that could receive sediment, altered flows, dewatering or machinery access.
  • Use a combination of electrofishing, fine mesh seine or suitable trap methods selected for the habitat, rather than relying on visual inspection alone.
  • Document the search area, method, replicate effort, dates, weather, water level, flow, water quality, vegetation condition, fish captured and non-target mortality.
  • Record a location as occupied when a Southern Pygmy Perch is detected, and map nearby connected and apparently suitable habitat.
  • Submit verified records to the relevant state wildlife or biodiversity database and provide records to the project environmental officer and approving authority where required.
  • Check current Commonwealth and state survey, animal ethics, fish collection, relocation and biosecurity requirements before sampling.

Before habitat disturbance: Avoid and minimise habitat loss

Treat any suitable freshwater habitat as a potential impact area until survey evidence and current government records show otherwise. The highest risk comes from losing aquatic vegetation, refuge pools, wetland connections and water quality.

  • Keep works, access tracks, spoil, fuel, concrete washout and sediment controls out of occupied and suitable aquatic habitat wherever practicable.
  • Retain dense submerged, emergent and fringing vegetation, overhanging vegetation, snags, woody debris, shallow backwaters, deep refuge pools and permanent water.
  • Maintain the connection between creeks, wetlands, billabongs and floodplains where the project could interrupt fish movement, recruitment or dispersal.
  • Prevent changes to flow, drainage, water depth, water temperature, salinity and dissolved oxygen that could isolate or dry refuge habitat.
  • Do not assume that a small wetland or farm dam is low value. Victorian refuge projects selected dams with permanent water, abundant fringing, submerged and emergent vegetation, riparian shade and restricted stock access.

Before habitat disturbance: Approvals and project planning

Commonwealth assessment relevant to the Basin lineage: Vulnerable under the EPBC Act conservation advice

Commonwealth whole-species assessment in the supplied advice: The national extent was assessed as not eligible, with the Murray-Darling Basin lineage assessed separately

State listing supplied for this profile: Victoria, Vulnerable

  • Check the current EPBC Act listing and determine whether the affected population is the Murray-Darling Basin lineage, which has a separate Commonwealth conservation assessment as Vulnerable.
  • Refer the action under the EPBC Act if it may have a significant impact on a nationally listed population or its habitat.
  • Obtain the relevant state fish collection, handling, relocation, threatened species and wildlife permits before any survey, salvage or translocation.
  • Confirm whether works need approval under state water, fisheries, pollution, wetland, native vegetation or threatened species legislation.
  • Prepare a fauna and aquatic habitat management plan that identifies no-go areas, access routes, dewatering controls, fish salvage methods, authorised handlers, relocation sites, stop-work triggers and reporting requirements.
  • Stage works so that connected habitat and refuge pools remain available until the affected area has been surveyed and any approved fish salvage is complete.

Before habitat disturbance: Pre-clearance preparation

  • Complete targeted aquatic surveys before clearing, dewatering, bank disturbance, wetland filling, culvert installation or changes to environmental flows.
  • Map and mark occupied habitat, suitable habitat, aquatic vegetation beds, refuge pools, wetland inlets and outlets, floodplain connections and access exclusions before machinery arrives.
  • Install exclusion fencing or physical barriers where they can protect retained waterbodies and vegetation without blocking fish movement or flood flows.
  • Prepare clean equipment and a fish disease and weed hygiene procedure before moving machinery, nets, pumps or personnel between waterbodies.
  • Confirm a nearby retained waterbody for any approved relocation, and verify that it has suitable water quality, aquatic cover, permanent or reliable water and no incompatible introduced fish risk.

During habitat disturbance: Daily controls and machinery coordination

Keep machinery and sediment away from water and aquatic cover. A fauna spotter catcher must work as part of the daily construction team, with authority to stop an activity that could kill fish or damage occupied habitat.

  • Hold a daily pre-start briefing covering occupied habitat, exclusion zones, weather, water levels, dewatering, access routes and the spotter catcher’s stop-work authority.
  • Inspect fencing, sediment controls, pumps, screens, spill kits and waterway crossings before work starts and after rainfall or flooding.
  • Keep fuels, chemicals, concrete, spoil and washdown water away from waterbodies and prevent turbid runoff from entering retained habitat.
  • Use low-impact access and avoid driving through shallow vegetated margins, backwaters, refuge pools or wetland channels.
  • Do not start dewatering, pumping, excavation, bank grading, culvert work or vegetation removal until the authorised aquatic fauna team has checked the work area.

During habitat disturbance: Fish handling and relocation

  • Stop the relevant activity immediately if a Southern Pygmy Perch is found in a dewatering area, isolated pool, pump intake, excavation or other work zone.
  • Allow only people authorised under the project plan and relevant permits to capture, handle, identify or relocate the fish.
  • Keep captured fish in clean, oxygenated water of matching temperature and water quality, minimise handling and release them promptly into the approved nearby retained habitat.
  • Do not move fish between catchments or waterbodies unless the action is authorised as a translocation and the disease, genetic and ecological risks have been assessed.
  • Take a photograph and record the location, habitat, number, condition, method of capture, personnel and final disposition for every detection.
  • Send injured or distressed fish to the nominated aquatic wildlife veterinarian, government officer or authorised wildlife carer, where such a service is available and the permit allows it.

During habitat disturbance: Habitat feature and waterbody controls

  • Retain aquatic plants, snags, woody debris, rocks, overhanging vegetation, shallow margins and deep pools unless their removal is authorised and unavoidable.
  • Use screened pumps and prevent fish entrainment during dewatering, with the pump intake placed away from dense aquatic vegetation and refuge habitat where practicable.
  • Progressively isolate and inspect any wetted work area, then undertake approved fish salvage before the area is drained or filled.
  • Maintain downstream and lateral flow connections where required for fish movement, recruitment and dispersal.
  • Treat ash, sediment, fuel, concrete and other runoff as a fish impact. Stop work and contain the source if it enters or threatens a retained waterbody.

During habitat disturbance: Stop-work triggers and records

  • Stop work and notify the environmental manager if Southern Pygmy Perch, an unidentified pygmy perch, dead or distressed native fish, a drying refuge pool, unexpected wetland connectivity or a pollution event is detected.
  • Stop work if exclusion fencing fails, a machine enters a no-go area, a pump cannot be screened, or sediment controls are overtopped.
  • Have the ecologist confirm species identity before work resumes where Southern Pygmy Perch could be confused with Yarra Pygmy Perch or another pygmy perch.
  • Record daily inspections, weather, rainfall, water levels, water quality, turbidity, fish observations, captures, mortalities, relocations, incidents, corrective actions and permit notifications.
  • Report any threatened fish death, injury, unauthorised capture or unauthorised relocation to the relevant authority within the timeframe set by the approval or permit.

After habitat disturbance: Post-work inspection and monitoring

The site remains a potential impact area after machinery leaves. Check that aquatic habitat has not been isolated, silted, dried or stripped of cover, and keep controls in place until the waterbody and vegetation have stabilised.

  • Inspect all disturbed waterbodies, banks, channels, wetland connections, refuge pools and aquatic vegetation immediately after works and after the first substantial rainfall or flow event.
  • Repeat targeted fish surveys where the approval or fauna management plan requires confirmation of occupancy, mortality, recolonisation or breeding.
  • Check for Southern Pygmy Perch recruitment, adult persistence, fish condition, aquatic vegetation cover, water depth, flow connection, turbidity, salinity and introduced fish.
  • Compare results with pre-work records and investigate any loss of occupied habitat, reduced water quality, fish mortality or failure of wetland reconnection.
  • Maintain exclusion fencing, sediment controls, screened pump arrangements and no-go areas until the environmental manager signs them off.

After habitat disturbance: Reporting and residual impacts

  • Provide the client, environmental manager, relevant government agencies and approval holders with a close-out report covering survey effort, detections, captures, relocations, incidents, habitat loss and rehabilitation actions.
  • Update the relevant state wildlife database with verified records, including coordinates, date, method, abundance or count and confidence in identification.
  • Report any unavoidable residual impact through the approval process and implement approved offsets or compensatory habitat actions where required.
  • Retain raw field data, photographs, permits, chain-of-custody records, water quality results and fauna incident records for the period specified by the approval.

Rehabilitation actions: Restore aquatic and riparian habitat

Rehabilitation should restore the shallow, slow flowing or still water habitat that Southern Pygmy Perch uses for shelter, feeding and spawning. It should also restore wetland connections and reliable refuge habitat, not just replant the bank.

  • Re-establish dense native submerged, emergent and fringing vegetation in shallow water, including water ribbons and other locally appropriate native aquatic plants.
  • Restore shaded riparian margins and restrict stock access where grazing has damaged bank and aquatic vegetation.
  • Reinstate suitable snags, woody debris, rocks, deep pools and backwaters where they are consistent with the waterway design and will not create a flood or obstruction hazard.
  • Design wetlands, farm dams and off-channel habitats with permanent or reliable refuge water, shallow vegetated margins and a connection to the river or wetland system where appropriate.
  • Remove or manage weeds that displace native aquatic plants, while avoiding herbicide entry into water and retaining cover until replacement vegetation is established.

Rehabilitation actions: Restore connectivity and reduce threats

  • Remove or modify project barriers such as unsuitable culverts, levees, temporary crossings and regulators where approved, so fish can move between waterways and floodplain habitat.
  • Use environmental water or other approved flow arrangements to reconnect off-channel wetlands at suitable times for spawning, movement and recruitment.
  • Restore refuge pools and backwaters in sediment-affected channels rather than relying only on added timber structures.
  • Control Redfin, trout, Carp, Goldfish and Eastern Gambusia where an approved targeted program shows they threaten the restored population or its habitat.
  • Prevent new fish introductions and clean equipment between waterbodies to reduce transfer of invasive fish, pathogens and aquatic weeds.

Rehabilitation actions: Monitoring and success measures

Published evidence of flow benefit: Recruitment and dispersal increased during floodplain inundation at Barmah-Millewa Forest

Victorian refuge project result to monitor: About 500 adults were collected and translocated to four selected farm dams

Key habitat condition for Victorian refuge dams: Permanent water, abundant fringing, submerged and emergent vegetation, riparian shading and restricted stock access

  • Monitor aquatic vegetation establishment, riparian shade, water permanence, depth, salinity, turbidity, flow connection and refuge pool condition.
  • Use repeat fish surveys suited to the habitat, including electrofishing, fine mesh seine or traps, with the same locations and effort used for baseline monitoring where practicable.
  • Treat detection of adults and young fish, successful recruitment, persistence through dry periods and use of connected restored habitat as key biological outcomes.
  • Investigate failure if vegetation does not establish, waterbodies dry prematurely, introduced fish increase, connectivity is lost or Southern Pygmy Perch is absent from suitable habitat after the agreed monitoring period.
  • Where restoration is intended to create a refuge population, use an approved monitoring and translocation program. Victorian work has used vegetated farm dams with permanent water, riparian shade and restricted stock access as refuge sites.

Rehabilitation actions: Fire and extreme weather planning

  • Keep reliable refuge pools and connected vegetated waterbodies available before drought, heatwaves or severe fire weather.
  • After fire, inspect for ash and sediment slugs, increased water temperature, altered water chemistry and loss of riparian or aquatic vegetation before allowing normal site controls to lapse.
  • Use emergency watering or approved relocation only under the relevant authority’s direction and permit conditions.
  • Include post-fire and drought surveys in the monitoring plan because isolated populations can be exposed to catastrophic drying or runoff impacts.

Sources