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Desert Mogurnda (Mogurnda larapintae)

The Desert Mogurnda is a small freshwater fish endemic to the Finke River system in the Northern Territory. It occupies permanent freshwater pools and rocky waterholes, including drought refuges that can be affected by changes to flow, water quality, sediment and fringing vegetation during development works.

Conservation status

Northern Territory, Territory Parks and Wildlife Conservation Act 1976: Near threatened.

Breeding season

The supplied documents do not provide monthly breeding or dispersal information for Desert Mogurnda. The seasonal profile below therefore identifies the information gap and applies year-round protection to permanent pools and drought refuges.

Monthly breeding, young and movement information for Desert Mogurnda was not provided in the supplied documents. Project-specific aquatic surveys should be timed and designed with local hydrology in mind.

  • Drought refuge use: Permanent pools can provide refuge during dry periods. The cited documents do not identify months when refuge use peaks.
  • Highest clearing risk: No seasonal clearing-risk peak is documented. Disturbance to permanent pools, rocky waterholes, fringing vegetation or connecting drainage should be treated as a year-round risk because these features can function as drought refuges.

Identification

The Desert Mogurnda is an elongated, laterally compressed fish with a bluntly rounded head, two dorsal fins and a rounded caudal fin. It has a distinctive mottled and barred colour pattern, but field identification should take account of the species' restricted range and its history of confusion with other Mogurnda species.

Adults are brown to mauve above, grading to tan or whitish below. The sides usually have 10 to 11 narrow bars formed by partly fused yellowish to cream spots, with many small reddish spots in adults.

The head has three reddish-brown diagonal stripes, pale areas between the stripes, and one or two short diagonal stripes behind the upper rear corner of the eye. The side behind the pectoral fin and the upper belly are yellowish.

The dorsal, anal and caudal fins are greyish to dusky yellow-brown. The second dorsal and anal fins have pale margins, darker submarginal markings and reddish-brown spots.

Maximum recorded size: Around 13 cm standard length.

Scales: Head and body scaled except for the lips, snout tip, preorbital region, lower jaw and chin.

  • Body elongate and laterally compressed, becoming more strongly compressed towards the rear.
  • Head bluntly rounded, with a gently arched snout and nape.
  • Lower jaw protruding, with an oblique mouth reaching to the front edge of the pupil.
  • Two dorsal fins, with the first rounded and lower than the second.
  • Pelvic fins separate and pointed, rather than fused.

Identification: Similar species and sexing

The species was formerly included within the broader concept of Mogurnda mogurnda. Other Mogurnda species occur in central Australia, including an unresolved population in the Davenport Ranges, so identification outside the known Finke system should be checked against current taxonomic and locality information.

Sexual dimorphism is generally inconspicuous. The supplied sources do not provide a reliable field character for separating males and females.

  • Do not assume that every purple-spotted or barred Mogurnda in central Australia is M. larapintae.
  • Record the exact waterbody and drainage location, retain clear photographs of the head, fins and colour pattern, and seek expert confirmation for unusual records.
  • The separate pelvic fins help distinguish this species from gobies with fused pelvic fins.

Identification: Field signs

There are no documented species-specific tracks, scats, calls, nests, sloughs or eyeshine. The relevant field evidence is the fish itself, its use of permanent pools and its occurrence in rocky waterholes or shallow pools with aquatic and emergent vegetation.

Mogurnda can climb or move out of water. Captive Desert Mogurnda were observed climbing tank walls and remaining out of water for more than 5 minutes, so fish may occur above the immediate water edge during handling or disturbance.

  • Inspect pool margins, rock overhangs, submerged cover and dense rushes, reeds or sedges when searching for fish.
  • Treat fish stranded in shallow margins or found outside the water as potentially alive and return them to suitable water only under the project fauna handling protocol.
  • Do not use absence from a single daytime observation as evidence that a pool is unoccupied.

Distribution: Range and strongholds

The Desert Mogurnda has a very restricted Australian range. It is known only from the Finke River system in the Northern Territory, within the arid Lake Eyre drainage region.

The species is endemic to the Finke River system in the Northern Territory. Records include the upper Finke, the Palmer River and sections of the mid-Finke drainage.

It has been recorded in shallow water in a long-term but temporary stony pool in upper Ellery Creek and in dense rushes, reeds and sedges at Two Mile Waterhole above Glen Helen Gorge. It is not recorded from the Hugh River section in the cited inventory.

States and territories: Northern Territory only.

Drainage system: Finke River system, within the Lake Eyre Drainage Division.

Known system-wide fish diversity: The Finke River system was reported to support nine fish species in the cited inventory.

  • Upper Finke River.
  • Palmer River section of the Finke system.
  • Mid-Finke records extending to at least the Stuart Highway bridge area.
  • Permanent and long-lasting pools that function as drought refuges.

Distribution: Population status

No total population estimate, density estimate or generation length is provided in the supplied documents. The species was described as relatively abundant at some surveyed sites, and its Near Threatened status in the Northern Territory reflects its restricted distribution and dependence on a limited number of drought refuges.

Population abundance can vary widely in temporary inland waterbodies. Further survey is required, particularly in the upper Palmer River and upper Finke River sections.

Quantitative population size: Not reported in the supplied documents.

Documented trend: No quantitative population trend is reported.

Northern Territory status: Near Threatened.

  • Do not infer population absence from a failed or single sampling event.
  • Map all permanent and long-lasting pools within the project area and assess their connection to the Finke system.
  • Treat confirmed records and suitable drought refuge pools as high-sensitivity aquatic habitat during project planning.

Habitat: Waterbodies and structure

Desert Mogurnda habitat is concentrated in freshwater pools within the arid Finke River system. The most important sites are permanent or long-lasting pools that provide refuge through dry periods.

The species inhabits permanent freshwater and rocky waterholes. Survey records also include shallow, stony pools and pools with dense rushes, reeds and sedges.

Important physical features include hard substrate for spawning, rocky margins, submerged cover and water that persists through dry periods. Permanent pools are particularly important because drought can remove fish habitat from temporary channels.

  • Permanent freshwater pools and rocky waterholes.
  • Shallow stony pools within the Finke drainage.
  • Dense rush, reed and sedge margins.
  • Rocky structure and hard surfaces within or beside the water.
  • Pools that remain available as drought refuges.

Habitat: Environmental limits

The species occurs in the arid Northern Territory, but the supplied documents do not give a reliable elevation range, water temperature range or flow threshold for Desert Mogurnda.

The species is associated with a highly isolated river system. Maintain natural connections between pools where practicable, while protecting permanent refuges from direct disturbance, pollution, excessive sediment and altered inflows.

  • Avoid drawing down, isolating or filling permanent pools.
  • Prevent sediment, chemicals, concrete washout and other pollutants from entering pools or connecting channels.
  • Retain fringing rushes, reeds and sedges where they occur at occupied or potentially occupied pools.
  • Plan works around the full pool margin and connecting flow path, not only the open-water area.

Foraging habitat: Diet and feeding sites

The Desert Mogurnda is a benthic freshwater predator. Its diet is reported as likely to include small aquatic animals rather than particular plant foods.

The likely diet consists of insect larvae, small crustaceans and small fishes. The supplied sources do not describe a measured diet, feeding rate or foraging range.

Foraging habitat is therefore expected to include shallow pool margins, rocky waterholes, submerged structure and vegetated edges where small aquatic prey occur.

Likely prey: Insect larvae, small crustaceans and small fishes.

Foraging range: Not reported.

  • Retain aquatic and emergent vegetation that supports insect larvae and other small prey.
  • Avoid removing rocks, submerged cover and pool-edge structure from occupied waterbodies.
  • Keep water clear enough for prey habitat to persist by controlling erosion and sediment entry.
  • Do not use chemical treatments in or near occupied pools unless they have been assessed for impacts on fish and aquatic invertebrates.

Breeding habitat: Breeding sites

Desert Mogurnda is an egg-laying fish that deposits adhesive eggs on hard substrate. The male guards the eggs until hatching.

Breeding habitat requires persistent freshwater, a hard surface for attachment of adhesive eggs and nearby cover suitable for a benthic fish. Rocky waterholes and pools containing exposed or submerged hard substrate are therefore important.

The supplied documents do not state the breeding months, clutch size, incubation period, age at maturity or lifespan for this species.

Reproductive mode: Oviparous benthic spawner.

Eggs: Adhesive eggs deposited on hard substrate.

Parental care: Male guards the eggs until hatching.

Breeding season: Not reported in the supplied documents.

Clutch size: Not reported.

Incubation period: Not reported.

Age at maturity and lifespan: Not reported.

  • Protect rocks, firm banks and other hard surfaces within the water and at the pool margin.
  • Avoid rapid changes in water level that could expose eggs or disturb guarding males.
  • Prevent sediment deposition from covering hard spawning surfaces.
  • Retain pool-edge cover and aquatic vegetation around potential spawning areas.

Sheltering habitat: Refuges and cover

Sheltering habitat is associated with permanent or long-lasting pools, rocky structure and vegetated margins. These features also provide refuge during the dry periods that characterise the arid Finke system.

The key refuges are permanent pools and long-lasting waterholes. The cited assessment identifies a limited number of permanent pools as a major component of vulnerability for arid Northern Territory fishes.

Records from the Finke system include rocky waterholes, shallow stony pools and dense rush, reed and sedge habitat. The supplied documents do not provide dimensions for pools, crevices or other shelter structures.

Known refuge type: Permanent freshwater pools and long-lasting waterholes.

Shelter dimensions: Not reported.

  • Protect permanent and long-lasting pools from drawdown, filling and physical disturbance.
  • Retain rocky margins, submerged rocks and other hard structure.
  • Retain dense rushes, reeds and sedges where they occur around occupied pools.
  • Inspect pool margins and cover before dewatering, netting, excavation or other aquatic works.
  • Use fish rescue and relocation procedures where works cannot avoid an occupied pool.

Sheltering habitat: Behaviour relevant to handling

Mogurnda can climb and may move out of water. This behaviour has been observed in captive Desert Mogurnda, which climbed tank walls and remained out of water for more than 5 minutes.

Containment, dewatering and fauna handling controls should prevent fish escaping from holding equipment or becoming stranded on dry ground.

  • Cover holding containers securely.
  • Check equipment, banks and rock edges for stranded fish after disturbance.
  • Keep rescued fish wet and shaded during identification and transfer.

Threats: Water and habitat disturbance

The main risks are loss or degradation of permanent drought refuges, poor water quality, sedimentation, altered hydrology and competition or disease from introduced fish. Project activities can affect the species even when works do not directly remove open water.

The limited number of permanent pools that provide drought refuge is a key vulnerability. Pool filling, drawdown, altered inflows, changed flood behaviour or loss of connections between pools can reduce available habitat.

Accelerated erosion and siltation may adversely affect arid Northern Territory fishes. Past intense grazing reduced fringing aquatic vegetation at some Finke waterholes, although vegetation recovery has followed changed management and feral horse control.

  • Keep spoil, sediment and runoff out of pools and connecting channels.
  • Avoid changing the depth, outlet, inlet or flow path of permanent waterholes.
  • Use erosion and sediment controls before ground disturbance begins.
  • Prevent heavy machinery and stock access from damaging pool margins and fringing vegetation.
  • Do not isolate a pool from its natural drainage connection without assessment of fish passage and refuge function.

Threats: Pollution and introduced species

Potential threats include chemical pollution, disease introduced with fish movements and competition from introduced species. Gambusia is identified as a particular concern if it becomes established in the Finke system.

Long intervals between floods could allow an introduced fish population to affect native species before the next major flow event. The cited inventory also records a report of Redfin introduced to the mid-Finke in the 1950s, although it did not appear to persist.

  • Do not release aquarium fish, bait fish or translocated native fish into Finke waterbodies.
  • Disinfect nets, buckets, traps, waders and other aquatic equipment between waterbodies in line with approved hygiene procedures.
  • Prevent fuel, oils, herbicides, concrete washout and other chemicals from entering aquatic habitat.
  • Report suspected Gambusia, Redfin or other introduced fish through the relevant Northern Territory authority.

Threats: Fire, roads and clearing

The supplied documents do not identify a species-specific road mortality rate, fire response or direct clearing threshold. Clearing and access works remain relevant where they remove fringing vegetation, increase erosion, disturb pool margins or alter surface-water delivery to permanent pools.

Fire planning should consider indirect effects such as loss of riparian cover, increased erosion and sediment delivery after rain. Road crossings and construction compounds should be kept away from permanent pools and natural drainage lines wherever practicable.

  • Survey permanent pools, rocky waterholes and connecting drainage lines before clearing or construction.
  • Keep clearing footprints, access tracks and laydown areas outside pool margins and fringing aquatic vegetation.
  • Design crossings to maintain natural flow and avoid concentrating sediment into pools.
  • Stabilise disturbed ground before the first rainfall likely to generate runoff.
  • Treat occupied pools and confirmed drought refuges as no-go aquatic habitat unless an approved fish rescue and impact management plan is in place.

Survey methodology: 1. Identify and inspect aquatic habitat

Desert Mogurnda is a small freshwater fish restricted to the Finke River system in the Northern Territory. Survey work must focus on permanent freshwater pools, rocky waterholes and associated rush, reed and sedge habitat, with methods suited to aquatic fauna rather than terrestrial fauna.

Map all permanent and long lasting pools, rocky waterholes, creek channels, floodouts and connected wetlands within and downstream of the proposed disturbance area.

Inspect shallow water, rock overhangs and dense rushes, reeds and sedges, as the species has been recorded in these habitats.

Plan repeat sampling where pools are temporary or water levels fluctuate, because fish abundance can change widely between drought, flood and recolonisation periods.

Known range: Finke River system, including the upper Finke, Palmer River and mid Finke sections of the drainage system.

Adult size: Up to about 13 cm standard length

Habitat: Permanent freshwater and rocky waterholes

Survey methodology: 2. Netting and active fish searches

Use seine nets, cast nets and other approved fish sampling equipment appropriate to the waterbody and site conditions.

Use seine netting where fish are abundant, the water is turbid, or the pool has a small or confined section where fish can be worked towards the bank.

Use cast nets in suitable clear or open water, including shallow areas and margins with cover.

Release captured fish promptly into the same waterbody unless a qualified aquatic fauna handler is authorised to retain or relocate them under the project plan.

  • Record the waterbody, sampling method, sampling area or reach, start and finish time, weather, water level, water clarity and all fish captured or observed.
  • Use extra care around rocky margins and submerged cover, where fish may shelter and where spawning substrates may occur.

Survey methodology: 3. Night and repeat sampling

Include night sampling where safe and permitted, because the Arid NT survey recorded some fish species more effectively at night and noted that cryptic fish may be missed by daytime sampling.

Repeat sampling across representative pools and connected reaches rather than treating one negative sample as evidence that the species is absent.

If water levels are low, sample each available drought refuge separately and record whether the pool is permanent, long lasting or temporary.

Where practical, undertake additional sampling after substantial wet periods, when connected surface water may allow recolonisation of previously dry pools.

  • Do not rely on a single opportunistic visit to clear a waterbody for impact.
  • Use an experienced freshwater fish ecologist to select sampling locations, equipment and effort because the supplied documents do not provide a species specific minimum number of nights, hours, trap nights or transect length.

Survey methodology: Minimum effort and reporting

  • Survey every waterbody, channel or wetland that may be directly disturbed, dewatered, isolated or affected by sediment, pollution or altered flows.
  • Document the full sampling effort and conditions, including the number of sites, reaches, visits, hours, net sets, net dimensions where relevant, water depth, water level and detection results.
  • Treat non detection cautiously, particularly in large, clear, deep or structurally complex waterbodies and in temporary pools.
  • Have a project fauna management plan specify the authorised aquatic fauna personnel, capture and release procedures, dewatering controls, relocation decision process and stop work triggers.
  • Submit confirmed records, voucher details and spatial data to the relevant Northern Territory wildlife or biodiversity records database and report any new locality outside the known range to the relevant wildlife authority.
  • Retain photographs or specimens only under the required scientific, animal welfare and collection permits.

Before habitat disturbance: Avoid and minimise

Avoiding disturbance to occupied waterholes is the safest measure for this species. Project planning should protect drought refuge pools, rocky habitat and water quality across the Finke River system.

  • Redesign the project to retain permanent and long lasting freshwater pools, rocky waterholes and their wetted margins.
  • Retain dense rushes, reeds, sedges and other native fringing vegetation around occupied or potentially occupied pools.
  • Maintain surface water connections between retained pools where those connections support fish movement during flow events.
  • Prevent sediment, fuel, chemicals, concrete washout and other pollutants from entering pools or connected drainage lines.
  • Avoid creating barriers that isolate pools, including poorly designed crossings, temporary bunds, diversion banks and uncontrolled dewatering points.
  • Keep grazing and vehicle disturbance away from pool margins where practicable, because loss of fringing aquatic vegetation has previously affected arid NT waterholes.

Before habitat disturbance: Approvals and work planning

Northern Territory status: Near Threatened

Common habitat risk: A small number of permanent pools provide drought refuge for arid NT fish

  • Check the current EPBC Act list and referral requirements before works, even though the supplied state listing identifies the species as Near Threatened in the Northern Territory.
  • Confirm Territory Parks and Wildlife Act requirements, permits and wildlife authority conditions before capturing, handling, retaining, translocating or disturbing fish.
  • Schedule works to avoid dewatering or isolating pools and to reduce the time that fish are exposed to capture, handling or poor water quality.
  • Stage construction so that retained aquatic habitat remains connected and functional while each work area is completed.
  • Include species specific controls in the fauna management plan, including aquatic survey, water quality, dewatering, rescue, relocation, incident response and rehabilitation requirements.

Before habitat disturbance: Pre-clearance preparation

  • Complete a pre-clearance aquatic survey before machinery enters the pool, channel or wetland impact area.
  • Mark no-go aquatic habitat, retained pool margins, access routes, sediment controls and dewatering exclusion areas on plans and on the ground.
  • Install exclusion fencing or equivalent controls where they can keep machinery, vehicles, spoil and people away from retained water and fringing vegetation.
  • Brief all workers that this is an aquatic species and that terrestrial hollow, log and burrow checks do not replace fish surveys.
  • Confirm that the fauna spotter catcher has suitable fish handling equipment, aerated holding containers if authorised, clean water from the capture site, and a documented release or relocation location.

During habitat disturbance: Daily controls and supervision

Aquatic works can kill fish through direct crushing, stranding, dewatering, sedimentation, pollution or loss of refuge habitat. The fauna spotter catcher must work as part of the construction team and have authority to stop work when the controls are not effective.

  • Inspect exclusion fencing, sediment barriers, bunds, pumps, access tracks and retained pool margins before work starts each day.
  • Keep plant, spoil, fuels, wash water and concrete products outside retained aquatic habitat and drainage lines.
  • Prevent uncontrolled water release, rapid drawdown, fish stranding and transfer of contaminated water between pools.
  • Use clean equipment between waterbodies to reduce the risk of disease and introduced fish transfer.
  • Have the fauna spotter catcher present for aquatic disturbance, dewatering, bank works, crossing installation and removal of temporary barriers.
  • Stop work if controls fail, fish are stranded, unexpected aquatic habitat is identified, water quality deteriorates, or a fish is found in the active impact area.

During habitat disturbance: Dewatering, capture and relocation

  • Do not commence dewatering until an aquatic fauna ecologist or other authorised person has inspected the area and approved the capture and release sequence.
  • Work from shallow margins towards deeper water where practicable, checking rock overhangs, dense vegetation and isolated puddles for stranded fish.
  • Keep captured fish in clean, oxygenated water from the capture location and minimise handling, crowding, heat exposure and time out of water.
  • Do not allow untrained workers to handle, identify, retain or relocate Desert Mogurnda.
  • Release fish into nearby retained habitat only when this is authorised, environmentally suitable and specified by the fauna management plan or wildlife authority.
  • Do not move fish between catchments or introduce fish to an unoccupied waterbody without explicit approval.

During habitat disturbance: If a fish is found

  • Stop the relevant activity and protect the immediate area from machinery, people, sediment and further water loss.
  • Have the authorised aquatic fauna handler identify and photograph the fish where this can be done without harmful handling.
  • Record the location, waterbody, condition, water level, water quality issue, activity underway and action taken.
  • Place an injured fish in suitable clean, oxygenated water and transfer it promptly to a veterinarian, licensed wildlife carer or other approved aquatic animal care facility.
  • Escalate any mortality, disease concern, pollution event, mass stranding or repeated capture to the project manager and relevant Northern Territory wildlife authority.
  • Resume work only after the fauna handler and project environmental officer confirm that the approved control measures are operating.

After habitat disturbance: Post-clearance checks

Post works checks should confirm that fish were not stranded or harmed and that retained waterbodies still function as habitat. Monitoring should focus on permanent pools, water quality, connectivity and introduced species.

  • Inspect the completed work area, pump discharge points, isolated puddles, rock margins and retained vegetation for stranded, injured or dead fish.
  • Check that temporary barriers, crossings and diversion structures have not blocked movement between retained aquatic habitats.
  • Remove temporary materials, spoil and sediment controls only when their removal will not release sediment or pollutants into the waterbody.
  • Record all animals handled, released, relocated, injured or found dead, with photographs and coordinates where possible.

After habitat disturbance: Monitoring and reporting

  • Monitor retained pools and affected reaches at the frequency specified in the approval, fauna management plan or rehabilitation plan.
  • Use the same sampling locations and methods where possible so that post works results can be compared with pre works records.
  • Check for continued presence of native fish, suitable water depth, fringing rushes, reeds and sedges, stable rocky margins, sediment accumulation and evidence of pollution.
  • Report mortality, habitat loss, failed water connections, erosion, siltation, introduced fish or disease concerns to the relevant authority and project approval holder.
  • Maintain exclusion fencing, sediment controls and access restrictions until the environmental officer confirms that the habitat is stable.

After habitat disturbance: Offsets and corrective action

  • Apply any offset, restoration or compensatory habitat requirement imposed by the approval or Northern Territory wildlife authority.
  • Investigate corrective action where a retained pool dries because of project works, becomes isolated, receives excess sediment or loses aquatic vegetation.
  • Use additional survey effort where monitoring results indicate that the species has declined or that the original survey did not adequately detect fish.

Rehabilitation actions: Restore aquatic habitat

Rehabilitation should restore permanent or long lasting freshwater refuge, rocky structure, native fringing vegetation and safe surface water connections. Success should be measured by habitat condition and confirmed fish use, not by revegetation alone.

  • Reinstate natural pool shape, depth variation, rocky margins and submerged rock cover where these features were removed or damaged.
  • Use clean local rock and hard substrate in suitable areas because the species deposits adhesive eggs on hard surfaces and males guard the eggs until hatching.
  • Re-establish native rushes, reeds, sedges and other locally appropriate aquatic and fringing vegetation around pool margins.
  • Reconnect retained pools and drainage channels where the pre works hydrology supported surface water movement, while avoiding erosion and uncontrolled high velocity flows.
  • Do not use terrestrial nest boxes or hollow replacement structures as a substitute for restoring aquatic habitat.

Rehabilitation actions: Manage threats during recovery

  • Control sediment runoff, accelerated erosion, siltation, chemical pollution and contaminated discharge throughout the rehabilitation period.
  • Exclude feral horses, livestock and vehicles from recovering pool margins where grazing or trampling could remove aquatic vegetation.
  • Prevent the release or transfer of gambusia and other introduced fish, and clean equipment before it is moved between waterbodies.
  • Manage weeds and fire in accordance with the site plan so that native fringing vegetation and water quality are protected.
  • Retain drought refuge pools and avoid altering their inflow, evaporation, shade or bank stability without an approved ecological assessment.

Rehabilitation actions: Monitoring and success measures

Biology relevant to rehabilitation: Oviparous benthic spawner; adhesive eggs are deposited on hard substrate and guarded by the male

Key recovery indicator: Continued use of retained or rehabilitated permanent freshwater habitat by Desert Mogurnda

  • Inspect rehabilitated habitat after flow events and during dry periods to confirm that pools remain stable, connected where intended and free of excessive sediment.
  • Measure recovery using site specific targets for water permanence, pool depth, rocky cover, native rush, reed and sedge cover, bank stability and water quality.
  • Undertake repeat fish surveys using consistent approved methods and record Desert Mogurnda presence, relative detection, size classes and evidence of breeding where permitted.
  • Investigate failure if native vegetation does not recover, a refuge pool is lost, introduced fish are detected, or repeated surveys no longer detect the species.
  • Continue monitoring until the approval holder and relevant wildlife authority accept that the habitat and fauna controls are functioning.

Sources