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Silver Perch (Bidyanus bidyanus)

Silver perch is a medium-sized native freshwater fish endemic to the Murray-Darling Basin. It uses connected rivers, anabranches, tributaries and floodplain habitats, and is particularly sensitive to flow alteration, barriers to fish movement, loss of lotic habitat and poor water quality on development sites.

Conservation status

Commonwealth, EPBC Act 1999: Endangered.

Queensland, Nature Conservation Act 1992: Endangered.

Victoria, Flora and Fauna Guarantee Act 1988: Endangered.

Australian Capital Territory, Nature Conservation Act 2014: Endangered.

Breeding season

The timing below describes a typical river population in the Murray-Darling Basin. Local conditions vary with flow, temperature, drought, stocking history and river connectivity.

The absence of a fish during a single survey does not demonstrate absence. Silver perch can move hundreds of kilometres and may use a reach intermittently in response to flow conditions.

  • Breeding: Spawning occurs from October to February. It generally follows upstream migration, a rise in water level and warmer water, and may peak at night between 9 pm and 1 am.
  • Breeding: February can still include spawning, with the October to February season spanning spring and summer.
  • Young: Eggs hatch in under 36 hours. Larvae drift downstream, become free swimming after about 5 days, and juveniles move upstream between October and April.
  • Movement and dispersal: Juveniles move upstream from October to April. Adults generally move upstream from November to February, and larger movements are associated with elevated flows and floods.
  • Highest clearing risk: October to April overlaps spawning, egg and larval drift, juvenile movement and access to nursery habitat. Avoid in-channel clearing, dewatering, barriers and high-turbidity works during this period where practical.

Identification

Silver perch is a deep-bodied, laterally compressed fish with a small head and mouth. It is usually silvery-grey to greenish-olive or brown on the back, with a lighter belly, dusky fins and a slightly forked tail.

Adults become deeper-bodied and more laterally compressed with age. The scales are small, the dorsal fin has a spiny front section and a softer rayed rear section, and the tail is weakly or slightly forked.

Typical river size: About 30 to 40 cm and up to 1.5 kg

Maximum size: Up to 61 cm and about 7.7 to 8 kg

  • Look for a grey to grey-brown back, silvery sides, a pale belly and dusky fins.
  • The head, eyes and mouth are relatively small compared with the body.
  • Some fish have dark scale edges that give the sides a faint chequered appearance.

Identification: Distinguishing features

Silver perch can be confused with golden perch and Macquarie perch in the Murray-Darling Basin. Silver perch has much smaller scales than those species and a forked tail. It belongs to the grunter family, Terapontidae, rather than the temperate perch family Percichthyidae.

  • Do not rely on colour alone, as body colour varies from silvery-grey to olive or brown.
  • The only other described Bidyanus species, Welch's grunter, is not found in the Murray-Darling Basin. Silver perch has more lateral line scales than Welch's grunter.
  • Fish stocked outside the natural range may be difficult to interpret as wild records. Confirm the location, stocking history and diagnostic characters before treating a record as evidence of a natural population.

Identification: Field signs and detection

There are no reliable terrestrial field signs such as tracks, scats, nests or burrows. Live fish may occur in schools and are often near the surface in clear water. Terapontid fish can produce an audible grunting sound when alarmed or stressed, including during capture.

  • Record fish rescued, trapped or observed during dewatering, salvage or aquatic surveys, including photographs and accurate location data.
  • Treat fish movement through a fishway, schooling activity or repeated captures as evidence of use of the connected river reach.
  • Use fish handling, rescue and disease-control procedures appropriate for threatened freshwater fish. Avoid transferring water, mud or equipment between catchments without effective cleaning and disinfection.

Distribution: Natural range

Silver perch is endemic to the Murray-Darling Basin, with its natural range extending across lowland and some historically occupied upland river systems in Queensland, New South Wales, the Australian Capital Territory, Victoria and South Australia. Hatchery translocations and stocked reservoirs occur in several other states, but these areas are not part of the natural distribution used for conservation assessment.

The historical range extended from the Lower Lakes and lower Murray in South Australia through the Murray, Murrumbidgee, Lachlan, Darling-Baaka and Victorian tributaries, north through the Barwon, Paroo, Warrego, Macquarie, Namoi, Gwydir, Culgoa and Condamine river systems in New South Wales and Queensland.

More than 90 per cent of recent sites are below 200 m elevation. Historical records also came from upland and montane reaches, including the Murrumbidgee and Macquarie systems and sites above 700 m, although some recent high-elevation records may be stocked fish.

  • Southern Murray-Darling Basin: Murray River and anabranches, Lower Darling-Baaka, Murrumbidgee, Lachlan, Edward-Wakool, Goulburn, Ovens, Campaspe and Loddon systems.
  • Northern Murray-Darling Basin: Upper Darling-Baaka, Paroo, Warrego, Barwon, Macquarie-Bogan, Namoi, Gwydir, Culgoa and Condamine-Balonne systems.
  • States and territory within the natural range: Queensland, New South Wales, Victoria, South Australia and the Australian Capital Territory.

Distribution: Strongholds and subpopulations

The mid-Murray is the species' stronghold and the main source of recruitment for much of the southern Basin. The Southern Murray-Darling Basin is treated as a set of connected subpopulations that can function as a large metapopulation when fish can move between rivers and anabranches.

Northern Basin subpopulations are sparse and highly imperilled. The Paroo, Barwon, Condamine-Balonne and Lower Murray subpopulations are important because they occur near range limits, may have distinctive genetic or environmental characteristics, or provide source and conduit functions.

Recent distributional dataset: 769 sites and 5,485 catch records from 1999 to 2022

Southern Basin share of records: About 95.7 per cent of catch records in the 1999 to 2022 dataset

Torrumbarry to Wentworth share: About 63.2 per cent of catch records in that dataset

Murray River stronghold: More than 85 per cent of all catch records in the Murray-Darling Basin came from the Torrumbarry to Wentworth and Yarrawonga to Torrumbarry subpopulations

  • The Torrumbarry to Wentworth and Yarrawonga to Torrumbarry sections of the Murray contain most recent records.
  • The mid-Murray is a source area for the Lower Darling-Baaka, Lower Murray, Campaspe, Goulburn, Broken and Edward systems.
  • The species is functionally extinct in the ACT and is on the brink of functional extinction in many northern valleys.

Distribution: Population trend

The species was formerly widespread and abundant, but has declined substantially across the Basin. Counts at Euston Weir fell by about 95 per cent over 50 years in the conservation assessment, while other sources report a decline of about 93 per cent between the 1940s and 1990s.

The current distribution is wide, patchy and variable. Some local southern populations may be stable or declining slightly, but abundance is low and northern population trajectories are difficult to estimate because catches are sparse and stocking can obscure whether fish are wild or introduced.

  • Treat any record from a natural river as potentially significant, especially outside the mid-Murray stronghold.
  • Check whether a record is near a stocked reservoir, conservation stocking site or hatchery release area before inferring a naturally reproducing population.
  • The current EPBC listing is Endangered. The change from the former Critically Endangered category reflects new information and assessment methods, not a demonstrated recovery.

Habitat: River and floodplain habitat

Silver perch uses a broad range of freshwater river habitats, from lowland alluvial channels to historically occupied clear, rocky upland reaches. It generally prefers free-flowing water and is now concentrated in lowland river reaches with persistent lotic habitat.

Suitable habitat includes main river channels, runs, riffles, anabranches, tributary reaches, lagoons and floodplain-connected habitats. Adults and juveniles may move between main stems, tributaries, anabranches and floodplains over very long distances.

In upland areas, historical records were mainly from main river channels rather than small tributary creeks. The species is often near the surface in clear water and historically formed large schools.

  • Retain flowing channel habitat and connections to tributaries, anabranches and floodplain nursery areas.
  • Protect deep refuge pools and perennial reaches during dewatering, excavation, bank works and flow diversion.
  • Avoid creating isolated pools or disconnected river sections through temporary bunding, cofferdams, crossings or reduced environmental releases.

Habitat: Physical structure and water conditions

Silver perch does not appear to depend on coarse woody debris at the fine microhabitat scale in the same way as Murray cod or golden perch. However, woody habitat remains important at broader scales because it affects channel form, flow hydraulics and productivity.

The species can survive water temperatures from about 2 to 37 degrees Celsius, but only for short periods at the extreme ends of that range. Persistent poor water quality, low dissolved oxygen, high temperatures and sedimentation can reduce habitat suitability.

Recorded temperature tolerance: About 2 to 37 degrees Celsius, with only short-term survival at the extremes

Recent site elevation pattern: More than 90 per cent of sites were below 200 m elevation

Historical upper records: Records occurred at elevations above 700 m, including in the Murrumbidgee and Macquarie systems

  • Maintain sufficient depth, flowing water and water quality in occupied reaches.
  • Control sediment entering waterways from exposed soil, roads, stock access, earthworks, fire-affected catchments and disturbed banks.
  • Retain and restore riparian vegetation to provide shade, stabilise banks and filter sediment from runoff.
  • Avoid assuming that an apparently open, snag-poor reach is unsuitable without considering flow, depth, connectivity and recent records.

Habitat: Connectivity

Connectivity is a habitat requirement because silver perch undertakes long-distance movements for feeding, dispersal, recruitment and spawning. Dams, weirs, road crossings, low-flow barriers, water diversions and temporary construction structures can divide populations and prevent access to suitable habitat.

Recorded movement: Individuals have moved 897 km and up to about 1,200 km in the Murray system

Barrier example: The Menindee main weir separates northern and southern subpopulations except during occasional high floods

  • Map all upstream and downstream barriers within the affected reach and assess whether they block fish passage under the expected construction and operational flows.
  • Plan aquatic works to maintain a continuous wetted passage or provide an approved fish rescue and relocation response where passage cannot be maintained.
  • Do not treat a short-term interruption as low risk: fish may need to move during a narrow seasonal flow or spawning window.

Foraging habitat: Diet

Silver perch is an omnivore that feeds in freshwater channels and connected off-channel habitats. Its diet is flexible and overlaps with that of common carp, so habitat degradation and carp-related loss of aquatic vegetation can affect food availability.

Adults eat zooplankton, aquatic insects and their larvae, molluscs, small crustaceans, shrimps, worms, algae and aquatic plants. Diet varies with habitat and fish size, and the species is not normally cannibalistic of its young.

  • Key prey include aquatic insects, zooplankton, snails, worms and freshwater shrimps such as Paratya and Macrobrachium.
  • Retain aquatic vegetation and productive shallow margins where invertebrate and plankton food resources develop.
  • Do not assume that larger silver perch are exclusively herbivorous. Diet studies show continued use of animal prey and dietary flexibility.

Foraging habitat: Where and how it feeds

Silver perch feeds in flowing river reaches and connected floodplain, lagoon and anabranch habitats. Juveniles use productive areas accessed during elevated flows, while adults and juveniles can occupy extended river reaches and move between habitat units.

Foraging movement scale: Juveniles and adults can move through extended river reaches, with individual movements recorded up to about 1,200 km

Food-web overlap: Silver perch and common carp have overlapping diets, and carp may have replaced some of the species' former trophic role in parts of the Basin

  • Protect the links between main channels, anabranches, lagoons and floodplains where high flows provide access to feeding and nursery areas.
  • Limit activities that remove macrophytes, increase turbidity, fill pools with sediment or reduce flow through productive shallow margins.
  • Consider flow timing as well as flow volume, because altered flows can reduce food availability and prevent access to feeding habitat.

Breeding habitat: Breeding biology

Silver perch breeds in connected river systems when seasonal temperature and flow conditions provide suitable spawning and dispersal cues. Spawning is usually preceded by upstream movement and a rise in water level and temperature.

Spawning generally occurs at night, with egg densities suggesting a peak between about 9 pm and 1 am. Eggs and newly hatched larvae drift downstream, so spawning habitat must remain connected to downstream nursery areas.

Spawning season: October to February

Spawning cues: Often follows upstream migration, a rise in water level and warmer water; spawning has been recorded at about 16 to 28 degrees Celsius

Egg production: About 200,000 to 700,000 eggs per female, with other sources reporting approximately 170,000 to 250,000 eggs per kilogram of body weight

Egg size and hatching: Eggs are about 2.5 to 3 mm and hatch in under 36 hours, or about 30 to 31 hours at 26 to 27 degrees Celsius

Larval development: Larvae are about 3.6 mm at hatching, become free swimming after about 5 days and begin feeding by about day 6

Age at maturity: Males at about 3 years and females at about 5 years in wild populations; hatchery fish may mature earlier

Lifespan: Wild fish are commonly estimated to live about 15 years; the oldest recorded river fish was 17 years and a reservoir fish was 27 years

  • Protect flowing reaches used for upstream migration and spawning from dewatering, barriers, sudden flow reduction, noise and poorly timed in-channel works.
  • Maintain water quality and dissolved oxygen during spawning and early development.
  • Keep eggs and larvae in the river system where possible. Do not discharge turbid, contaminated or low-oxygen water into occupied spawning or nursery reaches.

Breeding habitat: Breeding habitat features

Spawning generally occurs in river channels after upstream migration, with eggs drifting in the current. Eggs occur at higher densities near the shore and near the bottom of the water column. Strong recruitment is associated with suitable spawning flows followed by extended high flows or flooding that gives juveniles access to productive nursery habitat.

  • Maintain free-flowing channel sections between spawning and downstream nursery areas.
  • Protect shallow margins, connected floodplains, anabranches and tributary habitats used by drifting larvae and dispersing juveniles.
  • Avoid barriers that prevent adults reaching spawning areas or juveniles reaching nursery habitat.
  • Use seasonal timing controls for works in occupied reaches, with the highest level of protection from October to April when spawning, larval drift and juvenile movement overlap.

Sheltering habitat: Aquatic refuges

Silver perch has no known terrestrial shelter structures such as dens, hollows, burrows or nests. In rivers, refuge is provided by persistent water, depth, connectivity and suitable hydraulic conditions rather than by a single specialised cover feature.

Important refuge areas include deep pools, perennial flowing reaches, connected anabranches and other sections that retain water during drought. When flows are reduced, river sections can become disconnected pools with declining water quality, rising temperature and falling dissolved oxygen.

Refuge risk during low flow: Reduced releases can cause a river to become a series of disconnected pools as water is lost through evaporation and infiltration

Known specialised shelter: No species-specific dens, hollows, burrows, roosts or nest structures are described in the supplied sources

  • Identify and protect deep pools and perennial reaches before starting dewatering or bank and bed works.
  • Do not isolate refuge pools from the main channel unless fish rescue and relocation has been planned with the relevant fisheries authority.
  • Maintain shade and bank stability to reduce heating, sedimentation and loss of pool depth.

Sheltering habitat: Cover and habitat structure

Silver perch does not show a strong fine-scale preference for rock or other structure and is not dependent on coarse woody snags in the same way as some other large Murray-Darling fish. Nevertheless, woody habitat and intact banks can support channel form, hydraulic diversity and aquatic productivity at larger scales.

  • Retain instream woody habitat where it is safe to do so and avoid unnecessary removal of snags or bank vegetation.
  • Protect macrophyte habitat, particularly where juvenile fish occur, because loss of aquatic vegetation associated with carp may affect young silver perch.
  • Keep construction lighting, vibration, turbidity and noise away from retained refuge pools where practical.

Threats: Hydrology and barriers

Silver perch is affected by interacting threats across the Murray-Darling Basin. Construction and infrastructure risks are greatest where works alter flow, interrupt fish passage, disturb riverbed or bank habitat, reduce water quality or remove access to spawning and nursery areas.

Altered flow timing and volume is a major threat. Regulation and extraction have removed or reduced perennial flowing reaches, changed seasonal patterns and reduced natural flood events that support movement, recruitment and access to floodplain habitat.

Dams, weirs, road crossings, low-flow barriers and temporary construction structures fragment populations. They can prevent adults moving upstream to spawn and prevent juveniles dispersing to nursery areas.

  • Maintain environmental flows and avoid unplanned reductions in downstream releases.
  • Design crossings, culverts, causeways, temporary access tracks and cofferdams to maintain fish passage under relevant flow conditions.
  • Schedule unavoidable barriers and channel isolation outside the October to April breeding, larval and juvenile movement period where possible.
  • Assess cumulative barriers upstream and downstream, not only the structure within the project footprint.

Threats: Clearing, earthworks and water quality

Riverbank clearing, riparian degradation, sediment mobilisation, bed disturbance and loss of aquatic vegetation reduce habitat quality. Sediment can fill pools, reduce depth and substrate diversity, and harm fish eggs and larvae. Poor water quality can also lower oxygen, alter temperature and increase disease susceptibility.

Water temperature tolerance: About 2 to 37 degrees Celsius, with only short-term survival at the extreme ends

Water-quality concern: Low oxygen, altered temperature, sediment, contaminants and nutrient concentration can cause fish stress or mortality

  • Keep cleared soil, spoil, concrete washout, fuels, chemicals and other contaminants out of waterways.
  • Use sediment and erosion controls before earthworks begin, and inspect them after rainfall and high flows.
  • Retain riparian shade and stabilise disturbed banks with appropriate native vegetation.
  • Avoid dredging, bed excavation, dewatering and high-turbidity works in occupied reaches during spawning and larval drift.
  • Monitor dissolved oxygen, temperature, turbidity and contaminants when works could affect retained fish or refuge pools.

Threats: Drought, climate and extreme events

Drought, heat, altered rainfall and more severe fire and flood events can reduce flows, dry refuge pools, increase water temperature, create hypoxic or anoxic conditions and increase sediment delivery after fire. Climate change may also shift spawning cues and reduce recruitment.

  • Protect drought refuge pools and retain water in occupied reaches during emergency water operations.
  • Plan post-fire erosion and sediment controls before runoff reaches the river.
  • Treat sudden fish kills, gasping fish or low-oxygen pools as an environmental incident and notify the relevant authority promptly.
  • Consider the combined effects of drought, water extraction, heat and construction when assessing residual risk.

Threats: Introduced fish, disease and fishing

Common carp can compete for food and contribute to the loss of macrophyte habitat. Redfin perch may compete with silver perch and prey on juveniles. Introduced fish and contaminated equipment can spread diseases and parasites, including pathogens to which silver perch is susceptible.

  • Prevent movement of live fish, bait, water, mud and aquatic plants between catchments unless authorised.
  • Clean, dry and disinfect nets, electrofishing equipment, pumps, boats, boots and vehicles between waterbodies.
  • Do not release rescued fish into a different catchment or waterbody without approval from the relevant fisheries authority.
  • Protect low-abundance populations from recreational harvest and illegal capture, particularly during breeding migrations.

Threats: Project response

A silver perch record may trigger assessment under the EPBC Act and relevant state or territory legislation. A project can affect the species even when fish are not observed during a site inspection, because fish move over large distances and may be present seasonally or in connected habitat.

EPBC status: Endangered from 16 July 2024

State or territory status supplied: Endangered in the ACT, Queensland and Victoria; the conservation advice also identifies Vulnerable status in New South Wales and Endangered non-statutory status in South Australia

Project example: A temporary reduction and cessation of dam releases into the Peel River was assessed as likely to significantly affect silver perch habitat because the river could become disconnected pools

  • Check current threatened-species mapping, recent records, stocking history and state requirements before works start.
  • Use suitably qualified aquatic ecologists and follow approved fish rescue, relocation, monitoring and reporting procedures.
  • Treat connected habitat adjoining a record as potentially relevant, including reaches upstream and downstream of the immediate works area.
  • Document all fish observations, rescues, mortalities, barriers, flow changes, water-quality incidents and corrective actions.

Survey methodology: 1. Desktop and habitat assessment

Silver perch are highly mobile freshwater fish. Survey effort should focus on connected river channels, flowing reaches, pools, anabranches, floodplain access points and barriers that may affect movement. No species-specific survey protocol is provided in the supplied documents, so use the relevant state fisheries survey standards and obtain any required approvals before sampling.

Review recent records, stocking history, fish passage structures, water extraction points and known subpopulations before fieldwork.

Map flowing channels, pools, riffles, runs, anabranches, tributary junctions, floodplain connections, weirs, dams and other barriers within and downstream of the work area.

Give particular attention to free-flowing habitat, because silver perch generally prefer flowing water and undertake long-distance movements among main channels, tributaries, anabranches and floodplain habitats.

Treat stocked fish and records from stocked impoundments separately from naturally derived records when assessing the local population.

Natural range: Murray-Darling Basin of eastern Australia

Typical current distribution: Mostly lowland sites, with more than 90 percent of recent sites below 200 metres above sea level

Spawning period: October to February

Recorded movement: Up to 897 kilometres in one Murray River example, with movements of up to 1,200 kilometres also recorded

  • Record channel condition, water depth, flow, connectivity, water temperature, dissolved oxygen, turbidity, aquatic vegetation, woody habitat, riparian condition and recent disturbance.
  • Identify whether the site could provide spawning, nursery, refuge or movement habitat, including habitat upstream and downstream of the proposed disturbance.

Survey methodology: 2. Targeted fish survey

Use a suitably qualified freshwater fish ecologist and the state or territory fisheries authority's approved sampling methods for the waterbody type.

Sample representative flowing and still-water habitats separately, including the full extent of the proposed impact area and accessible habitat immediately upstream and downstream.

Time surveys to include suitable flow and temperature conditions where practicable, noting that spawning and movement are associated with rises in water level, warmer conditions and spring or summer flows.

Use methods that can detect adults, juveniles and larvae where required by the project risk assessment, and record the method, effort, location, depth, flow, water quality and number and size of all fish captured.

Life history timing: Adults generally move upstream from November to February, while juveniles may move upstream from October to April

Maturity: Males generally mature at about 3 years and females at about 5 years, with earlier maturity reported in hatchery settings

Size: Typically 30 to 40 centimetres long and up to about 1.5 kilograms in rivers, although fish can reach about 61 centimetres and 8 kilograms

  • Do not rely on a single visit or a single fishway count to describe abundance, because silver perch counts can vary greatly between years and are linked to migration events and flow conditions.
  • Separate wild, stocked and rescued fish in the records where their origin is known or can reasonably be inferred.
  • Use non-destructive handling and release procedures approved by the relevant fisheries authority.

Survey methodology: 3. Detection and movement checks

Inspect fish passage structures, culverts, low-flow crossings, weir pools and disconnected pools because barriers and altered flows can prevent access to spawning, nursery and refuge habitat.

Where works may reduce flow, assess connected refuge pools and the risk of progressive habitat loss through evaporation, infiltration, reduced dissolved oxygen, temperature change and declining water quality.

Repeat observations after flow rises or other suitable movement conditions where the project may affect a known movement route.

Use fish rescue or relocation only under an approved plan and by authorised personnel; emergency rescue of adult silver perch from a drought-affected Peel River reach was undertaken by NSW Fisheries in the supplied project example.

Important movement trigger: High magnitude and extended flooding can drive extensive juvenile movement, while smaller to moderate discharges can also be used

Known project risk: Temporarily ceasing dam releases can leave a river as disconnected pools and reduce aquatic habitat quality

  • Record any fish kills, distressed fish, stranded fish, barriers, fishway use, drying pools, low oxygen conditions or evidence of recent migration.
  • Treat a single absence as inconclusive where sampling conditions, access, stocking history or catchability are poor.

Survey methodology: Minimum effort and reporting

  • Prepare a site-specific survey and aquatic fauna management plan before fieldwork, stating the sampling methods, effort, timing, access limits, animal welfare controls and decision rules for additional survey.
  • Document the survey area, dates, start and finish times, weather, flow and water quality, equipment, personnel qualifications, sampling effort, coordinates, photographs, species identification and fate of every captured fish.
  • Submit verified records and any threatened-species observations to the relevant state or territory wildlife or fisheries database, and provide records required by the project approval and the Australian Government species database.
  • Report silver perch records promptly to the project environmental officer and the relevant fisheries authority where the record may affect clearing, flow releases, fish rescue or construction controls.
  • Do not publish sensitive location information where release could increase fishing, collection or other risks.

Before habitat disturbance: Avoid and minimise

Avoiding changes to flow, connectivity and water quality is the first control for silver perch. Plan works around the river system, not only the immediate footprint, because fish may move through long reaches and depend on habitat upstream and downstream.

Retain flowing channel habitat, deep refuge pools, riffles, runs, anabranches, tributary junctions, floodplain connections and intact riparian vegetation.

Avoid removing or isolating aquatic habitat, changing channel geometry, infilling pools, increasing sediment inputs or creating new barriers to fish movement.

Maintain natural or approved environmental flows and avoid temporary or permanent reductions in downstream flow unless assessed, authorised and controlled through an environmental water plan.

Retain and protect riparian vegetation to provide shade, reduce erosion and filter sediment from runoff.

Avoid works during periods when silver perch are likely to be spawning or undertaking upstream movement, particularly October to February, unless the timing is justified by a project-specific aquatic fauna assessment.

  • Use the smallest practicable work area and keep machinery, stockpiles, fuels, concrete washout and spoil outside the riparian and aquatic exclusion zones.
  • Maintain a connected route around temporary crossings, cofferdams, pumps and other in-stream structures, or provide an approved fish passage arrangement.
  • Prevent contaminated water, sediment, chemicals, concrete and dewatering discharge from entering retained habitat.

Before habitat disturbance: Approvals and planning

Confirm the current EPBC Act status before works begin. Silver perch is listed as Endangered under the current Australian Government conservation advice, and a significant impact assessment may be required for actions affecting habitat or an important population.

Check state and territory threatened-species, fisheries, waterway, fish-passage, collection, handling and relocation requirements for the project location.

Define the aquatic impact footprint to include direct works, dewatering, altered flows, downstream water-quality effects, barriers and access tracks.

Prepare an aquatic fauna management plan that covers survey, exclusion zones, dewatering, rescue, relocation, injury response, stop-work triggers, reporting and reinstatement.

EPBC listing: Endangered, effective from 16 July 2024

Important source area: The mid-Murray is the main stronghold and source area for breeding and dispersal in the Southern Murray-Darling Basin

ACT status in supplied action plan: The species was considered no longer present as a viable population in the ACT, although stocked fish occur in some impoundments

  • Obtain written approval for any fish capture, transport, holding, marking, tissue sampling, release or conservation stocking.
  • Consult the relevant fisheries authority where the site is in or near a known subpopulation, source population, stocked reach, fishway or recognised movement corridor.
  • Include Traditional Owners and water managers in planning where the waterway has cultural significance or management knowledge relevant to the species.

Before habitat disturbance: Site preparation

Complete a pre-clearance aquatic habitat inspection immediately before works and repeat it after substantial rainfall, flow change, dewatering or a delay that could change fish presence.

Mark aquatic exclusion zones, riparian buffers, refuge pools, fish passage routes, access points and no-go areas on plans and on the ground.

Install exclusion fencing, sediment controls, pump screens and clean-water diversions where they will reduce entry into the work area without blocking fish movement.

Stage works so that fish can move away from the disturbance or can be safely rescued before isolation or dewatering begins.

Brief machinery operators, supervisors and fauna spotters on identification, stop-work triggers, communication methods and the limits of their authority.

  • Do not start in-stream works until the fauna spotter catcher or aquatic fauna specialist confirms that the approved controls are in place.
  • Use screened pump intakes and inspect them regularly during pumping.
  • Maintain a clean equipment protocol to reduce the spread of fish pathogens and parasites between waterways.

During habitat disturbance: Daily controls and supervision

Silver perch can be harmed by reduced flows, isolation, poor water quality, barriers and handling stress. The fauna spotter catcher must work as part of the construction team, with authority to stop work when approved controls are not effective.

Inspect flow, water level, dissolved oxygen where relevant, temperature, turbidity, sediment controls, pump screens, exclusion fencing and fish passage controls before work starts each day.

Keep machinery out of retained aquatic habitat and use designated access points and crossings.

Prevent fuel, hydraulic fluid, concrete slurry, sediment and contaminated dewatering water from entering the channel.

Use a suitably qualified aquatic fauna specialist for fish capture, rescue, holding and relocation, rather than relying on a terrestrial fauna spotter catcher without aquatic experience.

Coordinate machinery movements with the spotter catcher through a clear stop signal or radio call, and stop machinery immediately when the agreed signal is given.

  • Record daily flow conditions, work areas, inspections, incidents, captures, mortalities, relocations, water-quality events and corrective actions.
  • Keep a current map of open work fronts, isolated pools, retained habitat, release sites and temporary barriers.
  • Limit night works where they would prevent effective aquatic monitoring or increase the risk of fish stranding, unless the approved plan addresses those risks.

During habitat disturbance: Habitat feature handling

Treat the channel, flowing water, pools, riffles, runs, anabranches, floodplain connections, riparian vegetation and fish passage structures as habitat features requiring protection.

Do not drain, fill, isolate or pump a pool until the approved fish rescue procedure has been completed and the fauna specialist confirms that fish have been removed or that the action is safe.

Use staged dewatering, low-flow diversion and screened pumps where approved, and check isolated areas for fish before sediment, spoil or plant enters.

Keep woody debris, aquatic vegetation and natural substrates where they contribute to flow, cover, geomorphic function or juvenile habitat, noting that the species' fine-scale dependence on particular structures is not well understood.

Do not create a new barrier with a causeway, cofferdam, pipe, culvert, sediment fence or access track.

  • If a crossing or temporary structure must remain in place, maintain an approved fish passage route and inspect it after changes in flow.
  • Manage sediment and turbidity at the source, because sediment can fill pools, reduce depth and substrate variation, and damage fish habitat.
  • Treat fire-affected runoff, flood debris, chemical spills and low-oxygen water as aquatic fauna incidents requiring immediate environmental response.

During habitat disturbance: If silver perch is found

Stop the activity that could injure or isolate the fish and notify the site environmental officer and aquatic fauna specialist.

Do not handle the fish unless you are authorised, trained and acting under the approved fauna management plan or fisheries approval.

Identify and photograph the fish only where this can be done without adding handling stress, and record its location, habitat, condition, size and likely origin.

If relocation is approved, move the fish to suitable, connected habitat nearby or to the approved release site using the authorised equipment, water-quality controls and transport time limits.

Send injured or moribund fish to an approved aquatic veterinarian, fisheries facility or wildlife rehabilitation provider, following the direction of the relevant authority.

  • Do not release a fish into an unapproved waterbody, across a catchment boundary or into habitat with a different stocking or disease-management status.
  • Do not retain silver perch for recreational, aquaculture or personal use.
  • Escalate any capture during spawning or migration, repeated captures, fish kill, stranding, blocked passage or rapid water-quality decline to the project environmental officer and relevant fisheries authority.

During habitat disturbance: Stop-work triggers and records

  • Stop work if a silver perch is found within the work area and the approved rescue or exclusion controls are not operating.
  • Stop work if dewatering leaves fish stranded, if a refuge pool is drying unexpectedly, or if fish are observed schooling, distressed, gasping, injured or dying.
  • Stop work after a spill, uncontrolled sediment discharge, fish passage blockage, pump-screen failure or unapproved change to downstream flow.
  • Record the trigger, time, location, photographs, water conditions, people involved, fish numbers and sizes, action taken, release or treatment location, mortality and regulator notifications.
  • Restart only when the aquatic fauna specialist and the authorised project environmental officer confirm that the corrective action is complete and documented.

After habitat disturbance: Post-clearance checks

Completion of construction does not end the risk. Check that flow, passage, water quality and aquatic habitat have been restored, then monitor the reach for delayed effects and recruitment.

Inspect the entire impact area and downstream reach for stranded, injured or dead fish after dewatering, refilling, flow release and removal of temporary structures.

Confirm that the channel is connected, fish passage is open, pools retain suitable depth, banks are stable and no spoil, sediment, concrete or contaminated water remains in the waterway.

Remove temporary barriers, pumps, hoses, cofferdams, access tracks and exclusion materials that could obstruct fish movement or degrade habitat.

Complete a final aquatic fauna inspection before demobilisation and after the first substantial flow or rainfall event.

  • Photograph reinstated channel and riparian areas from fixed locations.
  • Check culverts, crossings, weirs and fishways for blockages, scour, perched outlets and debris accumulation.
  • Repair failed erosion, sediment and riparian controls promptly.

After habitat disturbance: Monitoring and reporting

Monitor the affected reach and suitable reference habitat using the methods and timing set out in the approved management plan and any approval conditions.

Include fish passage, flow, water quality, aquatic habitat condition, fish observations, fish rescues, mortality, recruitment indicators and the condition of reinstated areas.

Continue monitoring through at least the relevant post-work spawning and movement period where the project altered flow, passage, channel habitat or water quality.

Compare results with pre-work observations and approved performance indicators, and investigate any decline or unexpected concentration of fish.

  • Submit compliance reports, survey data, maps, photographs and incident records to the approval authority and relevant state or territory wildlife or fisheries database.
  • Report new silver perch records, fish kills, failed passage, repeated stranding and unexpected impacts to the relevant regulator without waiting for the next routine report.
  • Retain monitoring and handling records in a form that allows individual events, locations and release outcomes to be audited.

After habitat disturbance: Residual impacts and offsets

Assess residual impacts after avoidance, minimisation, rescue and reinstatement measures have been applied.

Where an approval requires an offset, prepare and implement the approved Biodiversity Offset Management Plan or equivalent state measure.

Design any offset or conservation measure to improve habitat quality and conservation outcomes for silver perch, with objectives, actions, timeframes, performance indicators, monitoring, corrective actions, responsibilities and a legal mechanism for delivery.

Do not treat stocking alone as a substitute for protecting flowing habitat, passage, recruitment areas and water quality.

  • Demonstrate that offset actions are consistent with the current conservation advice and any applicable recovery or threat-abatement documents.
  • Maintain offset works and monitoring for the full period required by the approval.
  • Publish or provide plans and reports as required, while protecting sensitive ecological locations.

Rehabilitation actions: Restore channel and riparian habitat

Rehabilitation should restore a connected, flowing freshwater system with stable banks, shaded riparian habitat, refuge pools and safe fish movement. Use local reference reaches and the approved aquatic rehabilitation design to set site-specific targets.

Reinstate channel form, pool depth, riffles, runs and stable banks where construction has altered them.

Revegetate disturbed banks with locally appropriate native riparian species suited to the waterway and catchment, rather than relying on exotic pasture or ornamental plants.

Protect regenerating vegetation from grazing, trampling, weeds, erosion and repeated machinery access.

Control weed infestations and repair sediment sources from roads, stock access, drainage lines, fire-affected ground and construction areas.

Retain or reinstate woody habitat and aquatic vegetation where they support channel function, flow diversity, bank stability or juvenile habitat, while avoiding obstructions to fish passage.

  • Use erosion and sediment controls until vegetation is established and the bank is stable.
  • Maintain shade and riparian cover to moderate water temperature, reduce erosion and filter sediment runoff.
  • Do not place logs, rocks or other structures in a way that blocks the channel or creates a new barrier.

Rehabilitation actions: Restore passage and flow

Remove temporary barriers and rectify perched culverts, blocked crossings, weir-pool constraints and other project-related obstructions.

Design permanent crossings and fishways with the relevant fisheries authority and test their function across the expected range of flows.

Maintain approved environmental flows and seasonal flow variability needed for movement, spawning, downstream drift of eggs and larvae, and access to nursery habitat.

Reconnect anabranches, tributary junctions and floodplain access points where the project has severed or restricted them, subject to waterway approvals.

Protect deep pools and other refuge areas from infilling, excessive sedimentation, dewatering and unplanned extraction.

ACT action-plan objective: Support re-establishment of silver perch in the upper Murrumbidgee catchment by improving habitat and assisting regional actions where feasible

Relevant habitat measures: Maintain seasonal flow regimes, intact riparian zones, pool depths, low sediment inputs and fish passage

  • Inspect passage structures after construction, high flows and debris events.
  • Use the mid-Murray and other suitable local reference reaches to inform rehabilitation targets, recognising that habitat needs vary among subpopulations.
  • Do not use conservation stocking without a regional decision, suitable genetic provenance, disease controls and approval from the relevant authorities.

Rehabilitation actions: Monitoring and success measures

Monitor vegetation establishment, bank stability, sediment deposition, pool depth, flow connectivity, fish passage, water quality and aquatic fauna use.

Include surveys during and after the October to February spawning period where rehabilitation affects spawning or movement habitat.

Use repeatable locations and methods so that fish observations and habitat condition can be compared with pre-work data and a suitable reference reach.

Investigate and correct failures such as blocked passage, bank erosion, excessive sediment, weed dominance, low dissolved oxygen, loss of pool depth or unexpected fish mortality.

  • Set success measures before works begin, including stable banks, functioning passage, connected aquatic habitat, maintained refuge pools, established native riparian cover and no project-caused fish mortality.
  • Maintain weed, erosion, sediment, access and predator controls for the period specified in the rehabilitation plan.
  • Report monitoring outcomes, corrective actions and any silver perch records to the project environmental officer, approval authority and relevant state or territory database.

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