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Trout cod (Maccullochella macquariensis)

Trout cod is a large, endangered freshwater fish endemic to the southern Murray-Darling River system. It depends on deep flowing water with abundant woody debris, so river works, bank disturbance, sediment runoff, altered flows and barriers can affect habitat used by adults, larvae and juveniles.

Conservation status

Commonwealth, EPBC Act 1999: Endangered.

Victoria, Flora and Fauna Guarantee Act 1988: Endangered.

Australian Capital Territory, Nature Conservation Act 2014: Endangered.

Breeding season

Timing varies between catchments, but the main management period is spring breeding and early larval drift. Adult surveys are generally planned outside spawning, while larval surveys target the breeding period.

Survey guidelines recommend avoiding adult surveys during the spring breeding period where possible. If larval detection is required, drift sampling is undertaken during spawning, with appropriate approvals and fish welfare controls.

  • Resident adults: Adults show strong site fidelity and usually remain in small home areas, although occasional longer exploratory movements occur.
  • Breeding and spawning: Spawning occurs in spring, mainly October to November, at about 15°C water temperature. Eggs are adhesive and attached to hard surfaces.
  • Eggs and drifting larvae: Egg hatching begins about 5 days after fertilisation and may continue for up to 10 days. Larvae drift downstream for about 4 to 5 days, and larvae have been collected in November and December.
  • Juvenile recruitment: Young-of-year fish and recruitment records are associated with the spring breeding period, but the supplied documents do not define a longer fixed period of juvenile dependence.
  • Occasional movement: Most adults move little, but occasional exploratory movements of 20 to 70 km have been recorded. No consistent large-scale spawning migration is established in the supplied sources.
  • Highest clearing risk: Clearing, in-channel works, dewatering, snag disturbance and high sediment loads are most likely to harm breeding adults, eggs and drifting larvae from September to December, with peak risk in October and November.

Identification

Trout cod is a large, deep-bodied river fish that is often confused with Murray cod. Correct identification matters because Trout cod is protected and may occur in stocked or remnant populations near project areas.

Adults have a large mouth reaching to below the rear of the eye. The upper jaw projects beyond the lower jaw, the head profile is straight, the tail is rounded and the pelvic fins are positioned below the pectoral fins.

The body is usually blue-grey and speckled rather than yellow-green. Most individuals have a dark stripe through the eye, although this feature is also present in young Murray cod.

Recorded maximum: 850 mm total length and 16 kg

Usual current size: Usually less than 5 kg

Identification: Separating it from Murray cod

The overhanging upper jaw and blue-grey, speckled body are the main field characters separating Trout cod from the similarly shaped Murray cod, which is generally yellow-green. Juvenile Murray cod can also have an eye stripe, so that character should not be used alone.

Hybrids occur, including in the Murray-Darling system and at Cataract Reservoir. Suspected Trout cod or cod hybrids should be photographed and referred to a fish identification specialist rather than identified from a single character.

Sexual dimorphism: No obvious sexual dimorphism is reported

Identification risk: Confusion with Murray cod and hybrids is well documented

  • Do not retain or relocate a suspected Trout cod without the required authority.
  • Record clear photographs of the head, jaw profile, body pattern and fins where this can be done without harming the fish.

Identification: Field signs and survey records

There are no useful terrestrial signs such as tracks, scats, calls, eyeshine, burrows or tree hollows. In water, adults are most likely to be observed or captured around submerged or partly submerged trees, logs and snags, especially in deep water.

Breeding evidence includes adhesive eggs attached to a hard surface, male guarding of the eggs, and drifting larvae. Larvae hatch after about 5 to 10 days and disperse in the water column. Drift-net sampling during the breeding period can detect larvae, but adult handling and survey methods must minimise injury and stress.

Egg type: Demersal, adhesive eggs about 2.5 to 3.6 mm in diameter

Larval drift: Larvae drift downstream for about 4 to 5 days

  • Treat a fish captured near deep woody cover as a possible Trout cod until it has been identified.
  • Use experienced fish ecologists for surveys where Trout cod and Murray cod may co-occur.

Distribution: National range

Trout cod is endemic to the southern Murray-Darling River system. Its former range was much wider than its current distribution, and many records are from populations that disappeared or were later re-established by stocking.

Historical records include the Murray River in South Australia and New South Wales, the Murrumbidgee River in New South Wales and the ACT, the Macquarie River in New South Wales, and the Goulburn, Broken, Campaspe, Ovens, King, Buffalo and Mitta Mitta rivers in Victoria.

Relevant bioregions include the Riverina, South Eastern Highlands, Victorian Midlands, NSW South Western Slopes and Sydney Basin. In the ACT, historical and reintroduced records are concentrated in the Murrumbidgee and Cotter river systems.

States and territories with historical or current records: New South Wales, Victoria, Australian Capital Territory and South Australia

Primary drainage: Southern Murray-Darling River system

Former ACT range: The Murrumbidgee River through the ACT and adjoining reaches above and below the territory

Distribution: Strongholds and re-established populations

The only known natural remnant population identified in the recovery documents is in the Murray River between Yarrawonga and Barmah, extending downstream towards the Barmah and Torrumbarry area in later monitoring.

Self-sustaining or breeding re-established populations have been reported in Seven Creeks in Victoria, the mid-Murrumbidgee River, the lower Ovens River and parts of the Goulburn River. In the ACT, Bendora Reservoir is the main reproducing reintroduced population, while riverine records in the Murrumbidgee require care because hybridisation with Murray cod has been documented.

  • Check current state and territory records before works near the Murray River, Seven Creeks, Ovens River, Goulburn River, Murrumbidgee River or Cotter River.
  • Treat stocked populations as conservation populations even where their long-term persistence or breeding status is uncertain.

Distribution: Population status

Trout cod underwent a major decline in range and abundance and was reduced to one natural breeding population by the late twentieth century. Hatchery breeding and stocking have established additional populations, but many remain vulnerable to local fish kills, fishing, barriers, sedimentation and poor water quality.

There is no single national population estimate in the supplied documents. Monitoring has recorded recruitment and expanding distributions in some re-established populations, including the Ovens River and mid-Murrumbidgee River.

Known natural remnant populations: One population identified in the recovery documents

Documented stocking effort: More than 1.56 million fish released into 17 areas and 32 sites across eight catchments

Natural recruitment: Observed or inferred in at least six stocked areas in the 2013 review

Habitat: River habitat

Trout cod is primarily a riverine species of medium to large rivers and larger streams. It can persist in reservoirs following stocking, but its strongest habitat association is with deep flowing water and structural woody cover.

Adults occur in flowing water in the mid to upper reaches of rivers and streams. Recorded habitats range from the large, deep Murray River, with sand, silt and clay substrates, to narrower rocky streams such as Seven Creeks, with pools, rapids, cascades, rock, gravel and sand.

The species is most abundant where large woody debris is plentiful in deep water. In the Murray River, preferred positions have high quantities of woody debris, deeper water, relatively high surface velocity and are away from the bank.

Murray River habitat: Typically 60 to 100 m wide, deeper than 3 m, flowing, with abundant woody debris

Seven Creeks habitat: About 5 to 7 m wide, with pools generally less than 2 m deep and interspersed rapids and cascades

  • Map snags, branch piles, log jams, deep pools, steep clay banks, boulders, rapids and fish passage structures before construction.
  • Include downstream reaches that could receive sediment, turbid runoff, contaminants, deoxygenated water or altered flows.

Habitat: Structural features

Trout cod use snags, branch piles, boulders, steep clay banks and other cover. Adults have strong site fidelity and often remain near a home snag or small local area.

Deep habitat and structural diversity are important. Sand accumulation can fill pools, reduce depth and remove the spaces between rocks used by juvenile fish and aquatic invertebrates.

Adult home area: Often less than 500 m centred on a home snag in the lower Murrumbidgee River

Preferred depth: A preference for deeper habitats, including depths greater than 2.4 m in lowland rivers

  • Do not remove, lop, realign or bury woody habitat unless authorised and unavoidable.
  • Keep bank vegetation and stable banks intact where they protect deep pools, cover and water quality.
  • Prevent sediment from entering pools, riffles and areas containing woody habitat.

Habitat: Climate and temperature

The species has been associated with cooler upper reaches, but the natural remnant population occurs in the mid-Murray below Yarrawonga. It is therefore not restricted to upland streams.

Water temperatures recorded at wild and breeding sites include winter minima of 5 to 10°C and summer maxima of 20 to 25°C. Temperatures of 25°C or more for several days increased bacterial or fungal infection risk in captivity.

Recorded seasonal water temperatures: About 5 to 10°C in winter and 20 to 25°C in summer

Elevation limit: No specific elevation limit is provided; records span mid-Murray rivers, larger streams and South Eastern Highlands waterways

  • Assess water temperature, dissolved oxygen and flow changes where works occur below dams, weirs or water extraction points.
  • Treat cold-water releases, warm low flows and sudden temperature changes as potential habitat impacts.

Foraging habitat: Diet

Trout cod is a large carnivore and sit-and-wait predator. It forages around deep cover, woody debris, banks and other structures that allow it to ambush aquatic and terrestrial prey.

The adult diet is dominated by shrimps and crayfish, which make up about 75% in the cited study. Other prey includes aquatic insect larvae, freshwater prawns, other aquatic and terrestrial macroinvertebrates, and fish.

Juveniles also depend on aquatic invertebrate communities. Sediment that reduces benthic habitat can reduce prey availability as well as directly affecting fish habitat.

Dominant prey: Shrimps and crayfish, about 75% of the recorded diet

Other prey: Aquatic and terrestrial macroinvertebrates, freshwater prawns and fish

  • Protect snags, boulders, undercut banks, pools and riffle margins that support crustaceans, insect larvae and small fish.
  • Prevent sediment, fertiliser, pesticide and other runoff from degrading aquatic invertebrate habitat.

Foraging habitat: Foraging area and behaviour

Adults generally remain close to a home snag and use small local areas, although occasional exploratory movements of 20 to 70 km have been recorded before fish return to their home site.

The species is most active in low light, from dusk to dawn. It uses cover and flowing water rather than relying on open, shallow margins.

Typical adult home area: Less than 500 m in one lower Murrumbidgee study

Recorded exploratory movement: 20 to 70 km, with return to the home site

Peak activity: Dusk to dawn

  • Inspect deep snags and adjacent flow paths at dawn, dusk or night when safe and permitted.
  • Consider both the snag and its nearby deep-water feeding area when defining the area at risk from works.

Breeding habitat: Breeding biology

Trout cod breeds in spring when water temperature reaches about 15°C. Breeding habitat includes hard surfaces suitable for egg attachment, nearby cover for adults and flowing water for larval dispersal.

Females produce adhesive eggs that are attached to a hard surface. The male is understood to guard and tend the eggs. Larvae hatch after about 5 to 10 days and drift in the water column before settling into juvenile habitat.

Spawning has been reported around October to November. Adult surveys should avoid the spawning period where possible, while larval drift surveys are timed to the breeding period.

Breeding season: Spring, mainly October to November

Spawning temperature: About 15°C

Eggs: About 1,200 to 11,000 eggs reported; eggs are demersal, adhesive and about 2.5 to 3.6 mm in diameter

Incubation: Hatching begins after about 5 days and may continue for up to 10 days

Age at maturity: About 3 to 5 years

Lifespan: Thought to be about 20 to 25 years

  • Avoid in-water works, snag disturbance, dewatering, blasting and high sediment loads during the October to November breeding period where possible.
  • If works must occur during breeding, obtain species-specific advice and protect hard spawning surfaces, deep cover and downstream drift pathways.

Breeding habitat: Breeding habitat features

Breeding requires a hard surface for egg attachment, such as suitable structural habitat, and water conditions that support egg development and larval drift. Woody habitat, banks and deeper water also provide cover for breeding adults.

Larvae can be transported downstream and may be lost to irrigation channels, pumps or unsuitable flows. Sediment can smother adhesive eggs or prevent them attaching to the substrate.

Larval dispersal: Larvae drift downstream for about 4 to 5 days

Breeding evidence: Drifting larvae and young fish have been used to confirm recruitment in re-established populations

  • Identify hard submerged surfaces, snags, logs, boulders and deep pools upstream and downstream of the work area.
  • Maintain adequate flow and prevent fine sediment from settling on spawning surfaces.
  • Screen or isolate pumps and diversions where larvae or juvenile fish could be drawn into infrastructure.

Sheltering habitat: Primary refuges

Trout cod shelters in submerged woody structure and other deep-water cover. It does not use terrestrial dens, hollows, burrows or roosts.

Adults commonly occur within, beneath or beside snags, branch piles and other large woody debris. In smaller streams, fish also use boulders and cover in shallower water, while larger fish are often found in deeper pools.

Steep clay banks, undercut banks, boulders, rock piles and deep pools can provide additional refuge. The most important shelter sites may be patchy and limited in supply.

Deep-water association: Adults use woody debris close to deeper water and relatively high surface velocity

Small-stream refuge: Boulders, logs and other cover in shallow water, with larger fish using deeper pools

Terrestrial refuge signs: No dens, hollows, burrows, roosts or other terrestrial refuge structures are relevant

  • Mark submerged logs, snags, branch piles, boulders, undercut banks and deep pools as aquatic habitat before access, piling or bank works.
  • Do not use snag removal or realignment as a routine method for improving access or flow.
  • Where removal is unavoidable, obtain advice on replacement structural habitat and avoid isolating remaining cover.

Sheltering habitat: Site fidelity

Adults show strong site fidelity and usually make limited movements. In one study, 75% of tagged adults moved less than 25 m over four years. This means that damage to a single occupied snag or pool can affect a resident fish for a long period.

Occasional longer movements of 20 to 70 km have been recorded, so barriers and works outside the immediate home area can still affect access to habitat and population connectivity.

Adults moving less than 25 m: 75% of tagged adults in a four-year mid-Murray study

Reported home area: Less than 500 m centred on a home snag in the lower Murrumbidgee River

  • Assume a fish may remain associated with a particular snag or pool even when it is not detected during a brief survey.
  • Retain connectivity between deep pools and woody cover, particularly at crossings, weirs, culverts and temporary cofferdams.

Threats: Clearing and habitat disturbance

Trout cod has declined through the combined effects of habitat loss, flow alteration, barriers, poor water quality, introduced fish and fishing. Construction activities can intensify several of these pressures in a short period.

Removal, lopping or realignment of large woody debris destroys preferred adult habitat and can fragment remaining habitat. Bank clearing, riparian degradation, rock removal and works that fill pools reduce cover, depth and water quality.

Sediment from roads, earthworks, stock access, fires and exposed banks can fill pools, reduce substrate variation, smother adhesive eggs and reduce aquatic invertebrate prey.

Key habitat feature at risk: Large woody debris in deep, flowing water

Egg vulnerability: Fine sediment can smother adhesive eggs or prevent attachment

  • Keep machinery, access tracks, stockpiles and laydown areas out of the riparian zone and away from deep pools and snags.
  • Use sediment and erosion controls before earthworks begin, maintain them during works and inspect them after rainfall.
  • Do not remove woody debris from the channel unless there is a demonstrated safety requirement and an approved habitat replacement plan.
  • Prevent concrete washout, hydrocarbons, chemicals, high turbidity water and deoxygenated water from entering the river.

Threats: Hydrology and barriers

River regulation, water abstraction, reduced flooding, altered seasonality, cold-water releases and barriers can reduce habitat quality, interrupt movement and prevent recolonisation. Dams, weirs, culverts, causeways, levees, pumps and areas of unsuitable flow can all act as barriers.

Larvae and small fish may be lost to irrigation infrastructure. Reduced flow can also leave natural rock bars and cascades impassable and can increase the concentration of effluent or other contaminants.

Movement pattern: Usually limited, but occasional movements of 20 to 70 km occur

Documented barrier issue: Yarrawonga Weir has limited upstream expansion of the Murray River population

  • Maintain fish passage during temporary works and provide a site-specific passage plan for cofferdams, crossings, culverts and weirs.
  • Assess upstream and downstream effects, including changes to depth, velocity, temperature, dissolved oxygen and larval drift.
  • Do not dewater a pool or isolate a snag without an authorised fish rescue and relocation procedure.

Threats: Fishing, predators and disease

Trout cod are susceptible to angling and may be caught through misidentification as Murray cod. Illegal take, injury and post-release mortality can affect small populations. Brown trout and redfin perch may prey on juveniles or compete for food and space, while carp and other introduced fish can alter habitat and food resources.

Introduced fish can carry diseases and parasites. Hatchery releases also require disease screening and careful handling to avoid transferring disease to wild populations.

Known introduced threats: Brown trout, redfin perch, carp, goldfish, gambusia and oriental weatherloach

Hybridisation risk: Trout cod and Murray cod hybridise, with high levels documented in Cataract Reservoir

  • Keep workers and the public informed that Trout cod must not be taken or retained.
  • Use experienced fish ecologists for capture, identification, handling and release.
  • Do not release bait, aquarium fish or other non-native fish into waterways.
  • Clean and disinfect sampling and aquatic construction equipment between catchments where disease transfer is possible.

Threats: Fire, climate and water quality

Bushfire can be followed by heavy ash and sediment runoff, fish kills and long-lasting loss of pool and substrate habitat. Poor water quality, low dissolved oxygen, nutrient enrichment, contaminants and thermal pollution can also cause mortality.

Warmer and drier conditions may reduce flows, increase sediment delivery after intense rainfall and alter temperature cues for spawning. Climate effects can be greater where populations are isolated by barriers or confined to small habitat patches.

Water-quality fish-kill example: A 2004 Goulburn River fish kill included at least 20 Trout cod after very low dissolved oxygen

Thermal sensitivity: Fish held at 25°C or above for more than a few days were more prone to bacterial or fungal infection in captivity

  • After fire or intense rainfall, inspect downstream pools for ash, sediment, fish distress and reduced dissolved oxygen before commencing in-channel works.
  • Avoid exposing additional soil before forecast heavy rain and stabilise disturbed banks promptly.
  • Monitor temperature, turbidity, dissolved oxygen and conductivity when works occur below dams, near discharges or during low flows.

Survey methodology: 1. Define the aquatic survey area

Trout cod is a threatened riverine fish. Surveys must cover the project area and waterways that may be affected downstream, with particular attention to deep water containing submerged woody debris, snags, logs, boulders and steep or undercut banks.

Map the project footprint, access tracks, upstream and downstream reaches, connected tributaries, impoundments, wetlands and any areas that may receive altered flows, sediment or pollutants.

Record habitat condition, water depth and velocity, turbidity, woody debris, boulders, bank cover, barriers and potential spawning or larval drift habitat.

Use state and territory databases, the Australian Faunal Directory, the protected matters search tool, recovery plans, published records and local knowledge to identify known or potential trout cod locations.

Survey methodology: 2. Adult survey by angling

Use experienced fish surveyors and lure fishing with barbless hooks as a primary method for adult trout cod where safe access is available.

Survey around submerged or partly submerged trees, logs and snags in deep water, including habitat close to riverbanks and areas with cover near faster flowing water.

Target dawn, dusk or night, when cod are more active.

Spring and summer can increase activity, but avoid October and November where adult survey work could interfere with spawning.

Treat angling as a detection method, not recreational fishing, and release captured fish immediately with minimal handling.

Most effective adult method in cited surveys: Experienced angling was the most effective method in upper Murray surveys.

Spawning period: Around October to November.

Typical adult habitat: Deep water with abundant woody debris, often near riverbanks.

Survey methodology: 3. Electrofishing and visual survey

Use boat based or backpack electrofishing only by trained operators following the Australian Code of Electrofishing Practice and an approved fish handling procedure.

Use boat electrofishing for suitable deeper reaches and backpack electrofishing for shallow pools and riffles up to about hip depth.

Daytime electrofishing is most effective in low turbidity, but cod may hide in clear water; night electrofishing with lights can improve detection.

Combine electrofishing with angling where practicable because the two methods have different size and habitat biases.

Use daytime snorkelling in clear water for visual searches, while recognising that deep, turbid or fast flowing water will reduce detection.

Backpack electrofishing depth: Shallow pools and riffles to about hip height.

Important limitation: Electrofishing is less efficient in deeper, faster flowing water and can injure or kill fish if poorly operated.

Survey methodology: 4. Larval and juvenile survey

Sample drifting larvae with drift nets during the spawning season if the project could affect spawning or downstream larval transport.

Use light traps or small unbaited gee or bait traps only where larval or juvenile fish are the survey target and the method is appropriate to the waterbody.

Preserve and identify larvae using an experienced fish taxonomist because trout cod can be confused with Murray cod and hybrids are known.

Avoid adult survey disturbance during spawning, but use larval sampling during the spawning period where it is necessary to establish breeding.

Larval drift timing: Larvae drift after spawning in spring and have been collected in November.

Egg and larval information: Eggs are adhesive and attached to hard surfaces; larvae hatch after about 5 to 10 days and disperse in the water column.

Survey methodology: Minimum effort and reporting

  • Prepare a site specific survey design that states the length of river surveyed, number and location of sampling sites, method, operator, duration, time of day, season, water conditions and habitat sampled.
  • Use more than one method where practicable, because a single method can miss trout cod in deep water, clear water or low density populations.
  • Do not treat a non detection as proof of absence where suitable deep woody habitat was inaccessible or survey conditions reduced detection.
  • Record the fish, habitat and survey effort with photographs, coordinates and evidence of identification, including photographs or genetic samples where trout cod and Murray cod could be confused.
  • Submit confirmed records and relevant negative survey results to the relevant state or territory wildlife or biodiversity database, and provide records to the project approval holder and the relevant recovery or fisheries agency.
  • Report any injury, mortality, hybrid suspicion, fish kill, pollution event or newly discovered population promptly to the relevant state or territory fisheries or conservation authority.

Before habitat disturbance: Avoid and minimise habitat loss

Before works begin, treat occupied or suitable river habitat as a threatened species constraint. The main risks are loss of woody habitat, sedimentation, altered flows, barriers, poor water quality, cold water releases, alien fish, fishing mortality and hybridisation with Murray cod.

  • Redesign the works to retain deep pools, fast flowing reaches, undercut banks, boulders and large in stream woody habitat, especially snags in deep water near the bank.
  • Do not remove, lop, realign or bury logs, snags or other structural woody habitat unless the action is authorised and no practicable alternative exists.
  • Retain riparian vegetation and stabilise banks to reduce erosion, sediment entry and loss of shade.
  • Maintain fish passage and avoid placing temporary crossings, culverts, coffer dams, levees, pumps or other structures across the channel unless their effects have been assessed and approved.
  • Protect upstream and downstream habitat because sediment, altered flows, poor water quality and barriers can affect trout cod beyond the construction footprint.

Before habitat disturbance: Approvals and work planning

National status: Endangered under the EPBC Act.

State and territory status in supplied records: Endangered in the ACT and Victoria.

  • Check whether the action is likely to have a significant impact on this EPBC Act endangered species or its habitat, and obtain advice on an EPBC Act referral before works proceed where required.
  • Obtain all applicable state or territory fisheries, threatened species, waterway, vegetation clearing, water access and animal handling permits.
  • Engage a qualified freshwater fish ecologist and an authorised fish handling team where survey, capture, relocation or aquatic rescue is required.
  • Prepare a fauna and aquatic habitat management plan covering survey, fish rescue, water quality, sediment control, fish passage, stop work triggers, incident response and reporting.
  • Stage works to keep a connected refuge reach available and avoid isolating fish in dewatered sections.
  • Avoid adult disturbance during the October to November spawning period unless the work is necessary, authorised and supported by a species specific control plan.

Before habitat disturbance: Site preparation

  • Complete a pre-clearance aquatic survey before disturbing water, banks, snags, boulders, riparian vegetation or connected pools.
  • Mark retained snags, woody debris, deep pools, undercut banks, refuge areas, riparian vegetation and no go zones on construction plans and on the ground.
  • Install exclusion fencing or no entry markers where they can protect retained banks, pools, riparian vegetation and aquatic habitat without blocking fish passage.
  • Set out sediment, erosion, dewatering, spill and refuelling controls before machinery enters the riparian zone.
  • Inspect machinery, pumps, nets, tanks and other equipment to prevent transfer of fish, pathogens, weeds and contaminated sediment between waterways.
  • Plan a fish rescue and relocation route to nearby retained habitat within the same connected waterway, subject to approval by the relevant authority.

During habitat disturbance: Daily controls and machinery coordination

Keep the work area under daily ecological supervision where aquatic habitat is being disturbed. Trout cod are long lived, site faithful fish that can be harmed by capture, dewatering, sediment, poor water quality and loss of cover.

  • Hold a daily pre-start briefing with the site supervisor, machinery operators, environmental officer and fauna spotter catcher before work near the waterway.
  • Define the exclusion zone, access route, machinery limits, dewatering sequence, weather limits and stop work triggers at the pre-start briefing.
  • Keep machinery, refuelling, concrete, fuels, spoil, washdown water and chemicals out of the channel and riparian exclusion zones unless the approved method requires controlled access.
  • Use a fauna spotter catcher with aquatic fish experience to inspect each work area before machinery moves, during staged dewatering and whenever habitat is exposed.
  • Move machinery only on the spotter catcher's instruction where fish, water, logs, boulders, pools or bank habitat could be affected.
  • Stop or stage work during high turbidity, fish stranding, fish distress, a spill, fish kill, unexpected flow change, blocked fish passage or failure of erosion and sediment controls.

During habitat disturbance: Capture, handling and relocation

  • Only authorised and experienced personnel may capture, hold, identify, transport or release trout cod.
  • Use the least harmful approved method, keep fish in clean, oxygenated water, minimise air exposure and handling time, and do not handle fish unnecessarily.
  • Do not use recreational angling during construction; any approved capture method must be part of the fish rescue plan and conducted with barbless equipment where angling is used.
  • Confirm identification before release because trout cod, Murray cod and hybrids can be confused.
  • Relocate a live fish only under the approved plan, to suitable nearby retained habitat in the same connected waterway and at a location approved by the relevant authority.
  • Place injured or distressed fish with an authorised aquatic wildlife carer, veterinarian or relevant fisheries agency, and report any mortality immediately.

During habitat disturbance: Habitat feature controls

  • Do not remove snags, logs, boulders, deep pools or undercut banks unless they are within the approved impact area and the action has been assessed for trout cod effects.
  • If a log or boulder must be moved, retain it wet where practicable and place it back into an approved nearby location that provides deep water cover and does not obstruct fish passage.
  • Keep dewatering screens, pumps and hoses fish safe, inspect them regularly and prevent fish from entering pumps, irrigation channels or isolated work areas.
  • Progressively isolate and inspect each dewatered section so fish are not stranded in pools, under logs or against barriers.
  • Prevent sediment, ash, concrete, hydrocarbons and contaminated water from entering the channel, as sediment can fill pools, reduce habitat diversity and smother adhesive eggs.

During habitat disturbance: Findings and stop work

  • Stop work and protect the location if a trout cod, suspected trout cod, cod hybrid, fish kill, stranded fish or previously unmapped suitable habitat is found outside the approved impact area.
  • Keep machinery clear until the authorised aquatic ecologist or relevant authority has assessed the find and directed the response.
  • Record date, time, coordinates, waterway, habitat, fish measurements, photographs, identification basis, action taken, handler and release location for every capture or mortality.
  • Report a suspected hybrid or an unusual cod specimen for expert or genetic confirmation rather than relying on field appearance alone.
  • Record daily turbidity, dissolved oxygen where specified in the plan, water temperature, flow, sediment incidents, fish observations, equipment checks and corrective actions.

After habitat disturbance: Post-work inspection

After construction, verify that fish passage, water quality and structural habitat have been restored. Continue monitoring because trout cod populations may be small, site faithful and difficult to detect in deep or low density habitat.

  • Inspect the full work area and connected upstream and downstream reaches for stranded or injured fish, sediment deposits, bank collapse, blocked passage, damaged snags and altered pool depth.
  • Remove temporary barriers, pumps, pipes, access tracks and sediment controls only when the environmental officer confirms that removal will not release sediment or strand fish.
  • Confirm that retained and reinstated woody habitat remains in the water, is stable, provides cover and does not create an unsafe obstruction to fish passage.
  • Test water quality and discharge controls against the approved limits before releasing stored or diverted water back to the channel.
  • Complete a post-clearance aquatic survey using the approved combination of methods where the project disturbed suitable habitat or a known population.

After habitat disturbance: Monitoring and reporting

  • Monitor trout cod presence, recruitment, habitat condition, fish passage, water quality and sediment at the frequency and duration required by the approval or fauna management plan.
  • Use multiple sampling methods and include larvae, juveniles, sub-adults and adults where the objective is to assess establishment or breeding.
  • Compare results with pre-work data and report changes in catch rates, size classes, habitat use, mortality, hybrid occurrence and recruitment.
  • Submit confirmed records, survey data, incidents and monitoring results to the relevant state or territory biodiversity or fisheries database and approval authority.
  • Escalate adverse trends, repeated fish injury, fish kills, barrier failure or loss of woody habitat to the approval holder and relevant conservation or fisheries agency.

After habitat disturbance: Maintain controls and offsets

  • Maintain erosion, sediment, spill, fish passage and exclusion controls until the site is stable and the environmental officer signs them off.
  • Repair failed banks, scour protection, fishways, woody habitat structures and riparian fencing identified during monitoring.
  • Where approved impacts cannot be avoided, implement the required offset, habitat restoration or compensatory action for the affected trout cod habitat.
  • Keep all permits, photographs, spatial data, fauna records, handling forms, incident reports and rehabilitation results with the project environmental records.

Rehabilitation actions: Restore channel and woody habitat

Rehabilitation should recreate the river features used by trout cod, not just stabilise the bank. Priorities are deep connected water, structural woody habitat, intact riparian cover, low sediment input and safe fish passage.

  • Reinstate large structural woody habitat in deep water where it can provide cover and does not create a navigation or passage hazard.
  • Recreate scour pools and hydraulic diversity where sediment accumulation has reduced depth, using approved rock groynes, engineered log jams or comparable designs suited to the waterway.
  • Restore undercut banks, boulders, pool and riffle sequences and other features identified by the aquatic ecologist as suitable trout cod habitat.
  • Reconnect isolated pools and remove or modify temporary barriers so fish can move between retained habitat areas.
  • Do not install structures without considering flow, flood safety, sediment movement, fish passage and the risk of trapping fish.

Rehabilitation actions: Riparian, water quality and threat management

  • Replant and protect native riparian vegetation appropriate to the local river or stream community to shade the water, stabilise banks and reduce sediment entry.
  • Fence stock and control access where trampling or bank erosion threatens pools, snags or water quality.
  • Control weeds and invasive fish, including carp, redfin perch, trout, goldfish, gambusia and weatherloach, under approved state or territory programs.
  • Manage fire recovery and post-fire runoff to reduce ash, sediment and pollutant pulses into occupied or restored reaches.
  • Maintain environmental flows and water quality controls that support suitable temperature, oxygen, depth and connected habitat.

Rehabilitation actions: Rehabilitation monitoring

Recorded recovery measure in the Ovens River: Young of year trout cod were recorded in 7 of 10 monitoring years after stocking and integrated habitat, connectivity, riparian and awareness works.

Known habitat restoration examples: Rock groynes, engineered log jams, structural wood, rock, riparian revegetation and fishways have been used in trout cod recovery programs.

  • Monitor restored sites for woody habitat stability, pool depth, bank condition, sediment accumulation, fish passage, water quality and riparian survival.
  • Survey for trout cod across age classes using more than one method, with adult surveys outside the October to November spawning period and larval surveys during the spawning period where breeding assessment is required.
  • Use successful recruitment, a range of size classes, increasing or stable catch rates, use of restored habitat and continued passage as project success measures.
  • Continue monitoring long enough to detect recruitment because stocked or re-established populations may take years to breed and become self sustaining.
  • Report failures and adapt the design where restored habitat fills with sediment, becomes disconnected, is colonised by alien fish or is not used by trout cod.

Sources