Fauna Spotters logo

River Blackfish (upper Wannon River form) (Gadopsis marmoratus (upper Wannon))

The River Blackfish, upper Wannon River form is a small-range, bottom-dwelling freshwater fish from western Victoria. It depends on clear flowing water, woody cover and sheltered pools, so stream crossings, bank works, de-snagging and sediment runoff can affect it on works sites. The upper Wannon River form is listed as critically endangered in Victoria.

Conservation status

Victoria, Flora and Fauna Guarantee Act 1988: Critically endangered.

Breeding season

River Blackfish breed in freshwater from late spring to summer, with spawning recorded from November to January and linked to water temperatures of about 16°C. Timing in the upper Wannon form is poorly known and may vary with local water temperature and flow conditions.

Breeding mode: Egg laying in freshwater. Adhesive eggs are deposited on sheltered surfaces, and the male guards the eggs and attached larvae.

Egg numbers: Usually 20 to 500 eggs are reported. A 30 cm female may lay about 500 eggs.

Breeding sites: Submerged hollow logs, rock crevices, rocks, gravel beds and areas below undercut banks.

Incubation: About 14 to 16 days, depending on water temperature.

Early development: Larvae may remain attached to the egg casing for about 3 weeks after hatching. Fledging and weaning do not apply.

Age at maturity: Estimates range from 2 to 3 years to 4 to 5 years.

Breeding frequency: Not recorded

The upper Wannon form has limited form-specific biological information, so breeding timing should be checked against local water temperature, flow and recent fish observations each year.

  • Spawning and egg laying: Spawning occurs in spring to early summer, with November to January records for River Blackfish.
  • Eggs and attached larvae: Eggs hatch after about 14 to 16 days, and larvae may remain attached for a further three weeks.
  • Nocturnal feeding and shelter use: Adults are bottom dwelling and mainly active at night, using pools, snags, logs, rocks, undercut banks and other cover throughout the year.
  • Limited local movement: River Blackfish are non-migratory and generally remain within a small home range, commonly about 20 to 30 m.
  • Highest clearing risk: Avoid disturbing submerged logs, rock crevices, undercut banks, snags and riparian cover from November to February, when eggs and attached or recently detached young may be present.

Identification: Appearance and size

River Blackfish are dark, slippery, bottom-dwelling fish that usually stay close to cover. The upper Wannon River form is a distinct morphological form, with a reduced number of dorsal fin spines compared with other River Blackfish populations.

The body may be pale green, yellowish, brown, grey or almost black. It commonly has darker blotches or marbling, with a pale blue, yellow or purple-grey underside.

The upper jaw projects beyond the lower jaw. The mouth is large, the snout is rounded and the body has a heavy coating of slime. The dorsal and anal fins are long and low, and the tail is rounded.

Body position: Bottom dwelling, usually close to logs, rocks, undercut banks or other cover.

Activity: Mostly active at night, late in the evening and early in the morning.

  • Usually about 20 to 30 cm long.
  • River Blackfish generally can grow to about 60 cm, although large fish are uncommon in many inland catchments.
  • Dorsal fin with six to 13 spines in River Blackfish generally. The upper Wannon form has a recognised reduction in dorsal fin spines.

Identification: Similar species

The Two-spined Blackfish is the main similar fish of concern in Victorian freshwater surveys. River Blackfish generally have more than three dorsal fin spines, while the Two-spined Blackfish has two spines.

Identification of the upper Wannon form should be confirmed by an appropriately experienced freshwater fish ecologist, especially where formal records or threatened species decisions are involved.

  • Check dorsal fin structure carefully.
  • Do not rely on colour alone, as River Blackfish colour varies widely.

Identification: Calls and field signs

Fish do not produce calls or echolocation signals that can be used to locate them during ordinary site inspections. Direct observation, netting or electrofishing by appropriately authorised personnel is normally needed to confirm presence.

Look for suitable habitat rather than relying on droppings, nests, whitewash, stains or odour. Eggs may be attached inside submerged hollow logs or rock cavities, but these sites are difficult to inspect without disturbing habitat.

  • Dark fish sheltering beneath logs, rocks or undercut banks.
  • Small fish or juveniles among leaf litter, aquatic vegetation and wood debris.
  • Eggs attached to sheltered submerged surfaces, particularly inside hollow logs or rock cavities.

Distribution: Australian range

The upper Wannon River form occurs in western Victoria and has been isolated from other mainland River Blackfish populations for a long period. Its restricted distribution and isolation increase the consequence of losing individual habitat patches or local populations.

River Blackfish are endemic to south-eastern Australia and are widespread in Victoria. The upper Wannon River form occurs in the upper Wannon River system in western Victoria.

River Blackfish also occur in other Victorian coastal and inland catchments, as well as parts of the Murray-Darling Basin in New South Wales, Queensland and South Australia. These records should not be assumed to represent the upper Wannon form.

  • State relevant to this profile: Victoria.
  • Region for the upper Wannon form: upper Wannon River system, western Victoria.
  • The broader species occurs in clear streams, lowland rivers, lakes, reservoirs and some farm dams where suitable cover remains.

Distribution: Site-scale distribution

On a development site, apparently short sections of suitable stream may support fish using a small home range. A site without fish records should not be treated as unoccupied where connected pools, snags, undercut banks and clear flowing water remain.

Check upstream and downstream habitat, not only the proposed disturbance footprint. Barriers, drying sections and poor water quality may divide populations into small isolated patches.

  • Map pools, riffles, runs, snags, rock cover, undercut banks and connected flow paths.
  • Record barriers such as poorly designed culverts, weirs and temporary crossings.
  • Treat confirmed records and suitable connected habitat as high sensitivity areas pending advice from the relevant Victorian authority.

Distribution: Overseas range

The River Blackfish is native to Australia. No overseas range is relevant to this profile.

Habitat: Stream and river features

The upper Wannon River form is expected to have similar habitat requirements to other River Blackfish south of the Great Dividing Range. On works sites, focus on water quality, flow, cover and the condition of the stream margins.

Look for clear, gently flowing or slow-flowing water with permanent or reliable pools. River Blackfish use pools, riffles and runs, including lowland and foothill reaches.

Preferred habitat usually has rocky or gravel substrates, deep holes, undercut banks and shelter from high-velocity flows. Water temperatures used by River Blackfish generally range from 5 to 25 degrees Celsius.

  • Clear flowing streams and connected pools.
  • Deep pools beside snag piles or other submerged structure.
  • Rocky, gravel or cobble beds with low sediment loads.
  • Undercut banks and shaded margins.

Habitat: Cover and riparian setting

Retain large woody habitat, fallen timber, boulders, aquatic vegetation and leaf litter. Overhanging or fringing native vegetation provides shade, bank stability and future instream cover.

Small hollow logs in shaded streams can provide both shelter and egg-laying sites. Avoid treating snags or woody debris as obstructions unless a specific safety or hydraulic risk has been demonstrated.

  • Native riparian vegetation, including overhanging trees and understorey.
  • Emergent vegetation such as reeds where it is part of the natural stream margin.
  • Submerged logs, root masses, boulders and rock cavities.
  • Forested or well-vegetated catchments with limited soil erosion.

Habitat: Practical site checks

Before clearing, excavation, dewatering or installing a crossing, walk the affected reach and assess habitat continuity. Include upstream and downstream areas that may receive sediment, altered flows or contaminated runoff.

Keep machinery, spoil, fuel and concrete washout away from the channel and flood-prone margins. Plan controls before work starts, as fish may remain in small pools even when the surrounding channel appears unsuitable.

  • Identify isolated pools that could become stranded during dewatering or low flows.
  • Mark snags, undercut banks and rock cavities within and beside the work area.
  • Check whether temporary access or crossings will block fish passage or concentrate flow.
  • Use qualified freshwater fish personnel for any capture, handling or relocation decision.

Foraging habitat: Food and feeding areas

River Blackfish are nocturnal ambush predators. They forage around the cover and edges of pools, runs and slow-flowing stream sections rather than in exposed open water.

The diet includes aquatic insect larvae, crustaceans, molluscs, worms, terrestrial invertebrates and smaller fish. Local food use varies with available prey and stream condition.

Adults may move at night from a daytime shelter to nearby feeding areas. Their small home range means that damage to one pool or snag complex can remove both shelter and feeding habitat.

Feeding period: Mainly night, late evening and early morning.

Foraging style: Opportunistic carnivore and ambush predator.

  • Snag piles and woody debris with slow water around them.
  • Rock edges, undercut banks and pool margins.
  • Leaf litter and aquatic vegetation that support aquatic invertebrates.
  • Clear, well-oxygenated water with low sediment loads.

Foraging habitat: Works-site risks to foraging habitat

Sediment can fill spaces between rocks and woody debris, reduce aquatic invertebrate habitat and smother eggs. Loss of riparian shade can also change water temperature and reduce the quality of feeding areas.

Avoid unnecessary removal of snags, boulders, leaf litter and aquatic vegetation. Keep runoff controlled so fine sediment does not enter pools or settle downstream.

  • Use stable, clearly defined machinery access points.
  • Install effective sediment and erosion controls before ground disturbance.
  • Stage spoil and materials outside drainage lines and flood-prone areas.
  • Restore disturbed banks with native vegetation and stable habitat features.

Breeding habitat: Spawning sites

River Blackfish spawn in freshwater from late spring to summer, generally around November to January. The upper Wannon form is poorly known, so assume that sheltered woody and rocky habitat may be used for breeding wherever suitable adults are present.

Eggs are deposited on sheltered submerged surfaces. Recorded sites include hollow logs, rock cavities, rocky crevices, gravel beds and areas below undercut banks.

Submerged woody habitat is particularly important because adults often use the inside of hollow logs for egg deposition. Eggs are adhesive and may be guarded by the male.

Breeding period: Late spring to summer, with November to January reported for River Blackfish generally.

Fecundity: Low compared with many freshwater fish. A typical female may produce a few hundred eggs, depending on body size.

  • Hollow logs and submerged snags.
  • Rock cavities and crevices.
  • Sheltered areas below undercut banks.
  • Suitable gravel or rocky surfaces in low-velocity water.

Breeding habitat: Breeding conditions

Spawning is associated with increasing water temperature, with River Blackfish generally spawning when water temperatures reach about 16 degrees Celsius. Shaded, well-oxygenated streams with stable flow and intact cover are preferred breeding settings.

Do not enter, move or clean out submerged logs, rock cavities or undercut banks during the breeding period unless the action has been assessed and approved.

  • Maintain shade over pools and spawning habitat.
  • Prevent sediment from entering egg-laying sites.
  • Avoid sudden changes in flow or water level.
  • Retain connected refuge habitat downstream of works.

Breeding habitat: Breeding protection on works sites

Where works could affect suitable breeding habitat, arrange a targeted freshwater fish assessment before disturbance. If fish, eggs or occupied habitat are found, stop work in the affected area and obtain advice from the project ecologist and relevant Victorian authorities.

Do not assume that moving a snag or relocating fish will protect the population. Capture and relocation require appropriate authorisation, trained personnel and a site-specific method.

  • Schedule in-channel works outside the late spring to summer breeding period where practicable.
  • Use staged works that retain flowing water and refuge pools.
  • Inspect dewatered areas for stranded fish before isolating or draining them.
  • Retain hollow logs and other potential spawning structures in place wherever possible.

Sheltering habitat: Adult cover

River Blackfish usually remain close to a small home range and seldom disperse long distances. Shelter is therefore needed within each occupied pool or stream reach, not only elsewhere in the catchment.

Adults commonly hold in a single pool beside a snag pile or other structural cover. They also use rock cover, boulders, undercut banks, submerged logs and sheltered areas with slow flow.

Open water without cover is less likely to support adults. Retain cover on both banks and within the channel where it does not create a demonstrated public safety or flood risk.

Typical home range: About 20 to 30 m, with some sources describing less than 30 m.

Movement: Non-migratory and generally reluctant to disperse long distances.

  • Snag piles and hollow logs.
  • Rock cavities, boulders and cobbles.
  • Undercut banks and root masses.
  • Deep pools with slow water beside cover.
  • Overhanging riparian vegetation.

Sheltering habitat: Juvenile cover

Larvae and first-year juveniles use leaf litter, emergent vegetation, riparian vegetation and wood debris. Juveniles may gather in sheltered shallow areas rather than occupying exposed current.

Bank clearing, removal of leaf litter and loss of low vegetation can remove juvenile refuge even when the main channel remains wet.

  • Leaf litter deposits in shallow margins.
  • Emergent and aquatic vegetation.
  • Fine woody debris and root mats.
  • Shallow sheltered edges connected to deeper pools.

Sheltering habitat: Protection during construction

Keep exclusion areas around occupied pools, snags and undercut banks clearly marked. Prevent machinery access to the channel unless the work method has been approved and fish protection measures are in place.

Maintain fish passage around temporary crossings, cofferdams and diversions. Check for stranded fish whenever flow is interrupted or water levels are lowered.

  • Retain instream woody and rocky habitat.
  • Avoid de-snagging and unnecessary bank reshaping.
  • Use fish-friendly temporary crossings and maintain a continuous aquatic path where practicable.
  • Use trained fish handlers for any capture, inspection or relocation.

Threats: Instream habitat loss

The upper Wannon River form is critically endangered in Victoria and is vulnerable to localised losses. Development controls should focus on retaining habitat, preventing sediment and contaminants from entering water, and maintaining flow and connectivity.

Removing snags, hollow logs, boulders or undercut banks can remove shelter and breeding sites. Channel straightening, bed disturbance and bank reshaping can also reduce pool and riffle habitat.

Avoid de-snagging and retain natural structural habitat. If habitat must be disturbed, redesign the work first, then use a site-specific impact assessment and authorised mitigation.

  • Do not remove woody habitat unless there is a clear, assessed risk.
  • Keep excavation and construction plant out of the channel where practicable.
  • Protect pool margins, undercut banks and rock cavities.
  • Replace lost structural habitat only where approved, using a design suited to the reach.

Threats: Sediment, water quality and riparian damage

Sedimentation can smother eggs, fill rocky cover and reduce aquatic invertebrate prey. Clearing riparian vegetation increases erosion, removes shade and future snags, and can alter stream temperature.

Prevent sediment, hydrocarbons, concrete washout, chemicals and other contaminants from entering the waterway. Re-establish native riparian vegetation after works and keep livestock or machinery away from unstable banks.

  • Fence and clearly mark no-go areas beside the channel.
  • Use staged earthworks and effective erosion and sediment controls.
  • Maintain shade and native streamside vegetation.
  • Inspect controls after rainfall and repair failures promptly.

Threats: Flow alteration, barriers and climate stress

Reduced stream flows, prolonged drought, unnatural drying and altered temperature regimes can shrink refuge pools and interrupt movement between habitat patches. Culverts, weirs, temporary dams and poorly designed crossings can restrict fish passage.

Keep a continuous flow path where practicable and design crossings to suit the natural bed and expected low flows. Avoid works that strand fish in isolated pools or rapidly change water levels.

  • Plan in-channel works for lower-risk flow conditions while avoiding the breeding period where practicable.
  • Maintain downstream flow and pool connectivity during staged works.
  • Inspect culverts and temporary crossings for perched outlets, blockages and excessive water velocity.
  • Provide off-stream water for stock rather than allowing bank access to damage habitat.

Threats: Introduced fish, fishing and population isolation

Competition and predation from introduced trout can affect young River Blackfish. Recreational fishing pressure is also a concern because River Blackfish have low fecundity and small home ranges.

The isolated upper Wannon population has limited capacity to recolonise damaged habitat. Record all observations, protect connected reaches and report threatened fish findings through the project’s environmental incident process.

  • Do not stock or move fish between waterways.
  • Prevent accidental release of live bait or aquarium species.
  • Use clear procedures for fish rescue during dewatering.
  • Escalate any confirmed record, mortality or breeding site to the project ecologist and relevant Victorian authority.

Survey methodology: 1. Desktop assessment

The upper Wannon River form is poorly known and has a small home range. Surveys should focus on sheltered aquatic habitat, particularly pools with snags, hollow logs, rock cover, undercut banks and clear, gently flowing water.

Confirm whether the works intersect the upper Wannon River form’s known or potential range in western Victoria. Map pools, riffles, runs, snags, hollow logs, rocky cover, undercut banks, riparian vegetation, barriers and areas with groundwater influence.

Assess risks from dewatering, sediment, altered flows, snag removal, riparian clearing, contaminants, fish passage barriers, drought and introduced trout or other fish.

  • Obtain recent aquatic habitat and fish records from the relevant Victorian agencies and catchment authority.
  • Treat suitable habitat as potential habitat where records are old, absent or taxonomic identification is uncertain.
  • Check whether the proposal may affect a listed matter under the EPBC Act. Refer the project if required by the Act.

Survey methodology: 2. Aquatic fish survey

Use a suitably qualified freshwater fish ecologist to select methods for the waterbody and the survey objective. Electrofishing and fyke netting are suitable general methods, with bait traps considered where appropriate and lawful.

Sample pools, riffles and runs, including areas beside snags, hollow logs, rocks, undercut banks, leaf litter and aquatic vegetation. Include nearby suitable habitat if the work footprint is dry or inaccessible during the first visit.

  • Survey during warmer conditions when fish catchability is better, while avoiding unsafe flows, extreme heat and periods when the site is drying.
  • Use more than one capture method where practical, because each method has detection bias.
  • Repeat surveys when detection is likely to be poor or when a threatened population may be affected. Set the effort and repeat visits through a site-specific aquatic survey plan.
  • Do not rely on a single negative result to clear suitable habitat.

Survey methodology: 3. Breeding and habitat checks

Inspect submerged logs, hollow logs, rock cavities, rocky crevices and areas below undercut banks for adhesive eggs, larvae or guarding adult fish. Spawning generally occurs from late spring to summer, with Victorian spawning reported from November to January and when water temperatures reach about 16°C.

Look for young fish among leaf litter, aquatic vegetation and wood debris. Record whether cover is continuous between pools and whether drying or barriers could isolate fish.

  • Use underwater viewing, careful visual inspection and non-destructive sampling where possible.
  • Do not lift, move or dismantle potential breeding structures without approval and a species-specific method.
  • Record water temperature, flow, depth, turbidity, conductivity or salinity where relevant, dissolved oxygen, substrate, cover, riparian condition and evidence of recent drying.
  • Record all fish captured, including identification confidence, length, sex if known, life stage, location, method, effort, photographs and release condition.

Survey methodology: 4. Survey timing and reporting

Plan at least one survey when the site is accessible and fish are detectable. Add a breeding-season visit where works may affect submerged structures or flowing habitat between November and January.

A monitoring program for an affected population should track abundance, breeding evidence and a range of size classes. Reference or control sites should be included where management actions are being tested.

  • Record start and finish times, personnel, equipment, weather, water conditions, site access, habitat sampled and any deviations from the approved method.
  • Map captures, breeding places, refuge pools, barriers, proposed impact areas and retained habitat.
  • Have an experienced aquatic ecologist review the results before finalising the work method.

Before habitat disturbance: 1. Avoidance and approvals

Avoid disturbance to occupied habitat wherever practicable. The upper Wannon River form is listed as critically endangered in Victoria, so assume that an occupied site has high conservation value until survey and agency advice show otherwise.

Redesign the footprint to retain pools, flowing reaches, snags, hollow logs, rock cover, undercut banks, aquatic vegetation and shaded riparian habitat. Maintain water levels, natural flow paths and fish passage.

Obtain advice from the relevant Victorian environment and fisheries authorities before clearing, dewatering, snag removal, in-stream works or fish handling. Secure all required permits for surveying, capture, possession, release, salvage or translocation.

  • Assess whether an EPBC Act referral is required because of potential impacts on a listed threatened species or other protected matter.
  • If work is proposed in Queensland, check protected wildlife requirements and whether a species management program is required for disturbance to a breeding place. This upper Wannon River form is mapped in Victoria.
  • Use only an approved translocation or salvage plan. Do not move fish between catchments without written approval.
  • Document the approval conditions in the construction environmental management plan.

Before habitat disturbance: 2. Pre-clearance survey and site marking

Complete a pre-clearance aquatic survey close enough to the works to reflect current conditions. Survey all habitat that may be isolated, dewatered, shaded, sediment affected or altered by access tracks, crossings and bank works.

Mark exclusion areas in the field. Include occupied pools, breeding structures, refuge habitat, riparian cover and the access route for machinery.

  • Use a site-specific buffer determined by the aquatic ecologist, hydraulic assessment and approval conditions. Do not apply an assumed generic buffer where one has not been assessed.
  • Retain snags and hollow logs unless removal is expressly approved and unavoidable.
  • Identify a safe fish refuge and emergency response area before works begin.
  • Photograph and map the site before disturbance.

Before habitat disturbance: 3. Timing and water management

Schedule works outside the November to January spawning period where practicable, particularly where submerged logs, rock cavities or undercut banks may be disturbed. Also avoid periods of low flow, pool disconnection and natural drying.

Maintain a continuous aquatic pathway around the work area. Prevent sudden drawdown, stranding and isolation of fish.

  • Prepare a staged dewatering and fish salvage plan before any water is removed.
  • Use clean water diversion, screened pumps and sediment controls suited to the site.
  • Keep concrete, fuels, chemicals, dirty water and contaminated soil out of the channel.
  • Stop work if flow conditions change, fish become stranded or the approved habitat protection measures cannot be maintained.

Before habitat disturbance: 4. Crew induction and equipment

Induct all workers, plant operators, fauna spotter catchers and supervisors before entering the site. Explain the species’ appearance, habitat, breeding places, low dispersal ability and the location of exclusion areas.

Only authorised and appropriately trained personnel may capture, handle, identify, transport or release fish.

  • Show workers photographs or approved identification material and explain that River Blackfish have a long body, small scales, a long dorsal fin and mottled dark colouring.
  • Use clean, disinfected equipment between waterbodies to reduce disease and pest transfer.
  • Keep an approved fish handling kit, aerated containers, measuring equipment, shade and emergency contacts on site.
  • Display the stop-work authority and incident reporting process at the site office and induction point.

During habitat disturbance: 1. Sequential clearing and exclusion

Use a slow, staged approach and keep aquatic habitat connected. Stop work early if a fish, breeding place or unexpected water quality problem is found.

Clear from the least sensitive areas towards retained habitat, using the smallest practical work area. Complete terrestrial and riparian clearing without pushing debris, sediment or spoil into the channel.

Retain snags, hollow logs, rocks, undercut banks, leaf litter and aquatic vegetation in exclusion zones.

  • Fence or flag exclusion areas before plant arrives.
  • Keep machinery out of the channel unless the approved method allows access.
  • Use staged isolation and dewatering so fish can be surveyed and salvaged before each section is disturbed.
  • Check downstream and upstream refuge areas before starting each stage.

During habitat disturbance: 2. Stop-work and animal handling

Give the fauna spotter catcher or aquatic ecologist authority to stop work immediately. Stop for any River Blackfish, suspected breeding place, egg mass, guarding adult, stranded fish, unexpected flow change, pollution event or failure of sediment controls.

Handle fish only under the relevant approval and by authorised personnel. Keep handling brief, avoid heat and direct sun, and release animals only at the approved suitable habitat.

  • Do not touch eggs, larvae or a guarded breeding structure unless the approved method specifically permits it.
  • If an active breeding place is found, stop nearby work, establish an exclusion area, protect water quality and obtain advice from the approving authority and project ecologist before proceeding.
  • Colony or roost procedures do not apply to this fish. Treat aggregations of adults or juveniles as sensitive habitat and stop work until assessed.
  • Do not relocate fish casually, release them into another pool or transfer them between catchments.

During habitat disturbance: 3. Dewatering and salvage

Use a qualified aquatic fauna team for salvage from isolated pools, channels, sumps and pump lines. Inspect the work area repeatedly as water levels fall because fish may remain under cover or in shallow residual water.

Keep rescued fish in clean, oxygenated water at a suitable temperature and shade them from direct sunlight.

  • Screen pump intakes and check them regularly.
  • Search leaf litter, woody debris, rock edges and undercut margins before declaring an area clear.
  • Release fish to the approved nearby refuge habitat as soon as practicable, unless the permit requires another arrangement.
  • Record mortalities and any evidence of stress, injury or disease.

During habitat disturbance: 4. Injury, mortality and records

Treat an injured fish as a fauna incident. Keep it in clean, aerated water and contact the project ecologist and the relevant wildlife or fisheries authority for instructions.

Record all captures, releases, mortalities and breeding observations, including animals found during routine earthworks.

  • For each animal, record date, time, location, method, identification, length, life stage, condition, action taken and release location.
  • Record the cause and extent of any injury or mortality, with photographs where this can be done without further harm.
  • Report incidents within the timeframe set by the approval, permit and construction environmental management plan.
  • Stop and review the method before restarting if repeated injuries, mortalities or fish strandings occur.

After habitat disturbance: 1. Post-clearance checks

Keep the site under observation after the main disturbance. Small home ranges mean that local habitat damage may not be offset by apparently suitable habitat elsewhere.

Inspect the full work area, isolated pools, pump lines, sediment controls, downstream reach and retained habitat after dewatering and clearing. Confirm that no fish, eggs, larvae or stranded animals remain.

Check that snags, hollow logs, rocks, undercut banks and riparian cover identified for retention are intact.

  • Complete checks at the end of each work stage and after significant rainfall, flow changes or equipment failure.
  • Remove temporary barriers, hoses, screens and debris only when the aquatic ecologist confirms that doing so will not strand fish or release sediment.
  • Repair erosion, leaks and failed controls immediately.

After habitat disturbance: 2. Release and relocation follow-up

Confirm the condition and location of all relocated fish. Use the approved release site and keep a clear chain of custody from capture to release.

Where translocation has been approved, monitor the receiving habitat and report any unusual mortality, disease signs or loss of water quality.

  • Do not assume that a fish released into a nearby pool has re-established successfully.
  • Record release habitat, water conditions, number and size of fish, and any subsequent recaptures.
  • Notify the relevant authority and project ecologist if fish cannot be released as planned.

After habitat disturbance: 3. Reporting and monitoring

Prepare a completion report that compares the approved method with what occurred on site. Include survey data, habitat maps, photographs, permits, incidents, fish handling records and rehabilitation actions.

For a site supporting the upper Wannon River form, establish repeat monitoring with reference or control sites where practicable.

  • Monitor fish presence, breeding evidence, recruitment and the range of size classes, not just total captures.
  • Use electrofishing or fyke netting only under approved methods and by qualified personnel.
  • Schedule repeat monitoring at intervals suited to the approval and risk, with one to two year intervals used for broader population-health monitoring where appropriate.
  • Track water quality, flow, sediment, cover, riparian condition and fish passage alongside fish results.

After habitat disturbance: 4. Incident review

Hold a review with the site supervisor, fauna team, aquatic ecologist and relevant authority after any fish mortality, breeding-place disturbance, major sediment release or unplanned dewatering.

Use the findings to change the work method before the next stage or future project.

  • Identify the first point at which the risk became apparent.
  • Record which control failed and who was notified.
  • Update inductions, exclusion mapping, equipment and stop-work triggers.
  • Close out each corrective action and retain the evidence.

Rehabilitation actions: 1. In-stream and bank habitat

Rehabilitation should restore cool, clear, gently flowing water and the cover used for shelter, feeding and spawning. Focus on connected habitat that can retain water through dry periods and support local recruitment.

Retain or reinstate woody habitat, stable rocks, undercut banks, deep pools, riffles and runs in designs approved by the aquatic ecologist. Use local materials that will not create a flood, erosion or fish passage hazard.

Restore shaded riparian vegetation and protect the bank from stock, machinery and uncontrolled access.

  • Fence waterways and provide off-stream stock water where grazing is a risk.
  • Revegetate stream edges with indigenous species suited to the local catchment.
  • Control weeds without allowing herbicide, sediment or green waste to enter the water.
  • Do not remove existing snags as part of routine maintenance.

Rehabilitation actions: 2. Replacement breeding structures

Where natural breeding structures have unavoidably been lost and approval supports replacement, install stable hollow logs, rock crevices or other submerged woody structures that resemble local habitat. River Blackfish deposit adhesive eggs on sheltered surfaces and males may guard the eggs.

Design and place structures with a freshwater fish ecologist and obtain approval before installation.

  • Anchor structures securely so they do not mobilise during flow events.
  • Place them in sheltered water near retained cover, while maintaining fish passage and avoiding excessive scour.
  • Do not use nest boxes, bat boxes, artificial roosts or terrestrial nest structures for this fish.
  • Inspect replacement structures for stability, sediment burial, eggs and fish use during monitoring.

Rehabilitation actions: 3. Water quality and flow

Restore conditions that support clear, oxygenated water and stable aquatic habitat. Protect groundwater-fed pools and avoid changes that cause unnatural drying or abrupt flow reduction.

Use permanent erosion and sediment controls until vegetation is established and the channel is stable.

  • Prevent sediment, contaminants, concrete washout and turbid water from entering the stream.
  • Maintain environmental flows and reconnect isolated habitat where approved and hydraulically safe.
  • Remove or modify fish passage barriers under an approved design.
  • Manage introduced trout and other pest fish through lawful, catchment-based programs rather than ad hoc removal.

Rehabilitation actions: 4. Long-term monitoring

Monitor rehabilitation during establishment and through suitable flow and breeding conditions. Assess whether habitat is being used, not only whether planting has survived.

Use fixed photo points and mapped habitat plots, supported by repeat fish surveys where the risk and approvals justify them.

  • Track fish presence, breeding evidence, juveniles, size classes and use of restored cover.
  • Track pool depth, flow, temperature, dissolved oxygen, turbidity, sediment, riparian shade and snag condition.
  • Compare results with reference sites where possible.
  • Keep monitoring until performance criteria are met and transfer ongoing maintenance to the responsible land or water manager.

Sources