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Saddled Galaxias (Galaxias tanycephalus)

The saddled galaxias is a small, threatened freshwater fish found only in Arthurs Lake, Woods Lake and nearby sections of the Lake River in Tasmania's Central Highlands. Its lake margins and connected waters may be affected by construction, access works, water extraction, sediment runoff and changes to fish passage, so downstream and in-water effects need to be assessed as well as direct clearing.

Conservation status

Commonwealth, EPBC Act 1999: Vulnerable.

Tasmania, Threatened Species Protection Act 1995: Vulnerable.

Breeding season

The species is non migratory within freshwater as far as the general Tasmanian galaxiid guidance indicates. The seasonal pattern below combines the species specific reports of autumn and spring spawning with the reported summer peak of small fish.

Survey guidance states that time of year is generally not important for sampling Tasmanian galaxiids because they are not known to migrate within freshwater and live for several years in the same habitat. Project surveys should still account for autumn and spring breeding and the summer peak of small fish.

  • Breeding, autumn spawning: Autumn spawning is reported for saddled galaxias.
  • Young and recruitment: Small fish are reported in Woods Lake throughout the year, with a peak in summer. The documents do not define a narrower dependent young period.
  • Breeding, spring spawning: Spring spawning is reported, and breeding may peak in late spring.
  • Lake and river use: The species is almost exclusively lake dwelling. Fish in nearby Lake River sections are thought to be vagrants swept out by outflow releases, not a seasonal migration.
  • Highest clearing risk: Risk is highest during the reported autumn and spring breeding periods, including late spring, when disturbance to lake margins, water quality or hydrology may affect spawning or recruitment. Aquatic habitat remains sensitive throughout the year.

Identification

The saddled galaxias is a small native galaxiid with a distinctive saddle-like pattern over the back and sides. Adults are usually associated with rocky lake margins, while larvae and juveniles can occur in open lake water.

Adults reach about 150 mm. Smaller fish are dark olive on the back, yellow green around the markings and silver underneath. In larger fish, the back and sides may become black with a purple sheen, with a greyish belly. The fins may have black edges, although this is not usual.

The markings may form a series of saddles or become large oval spots along the back. This pattern is the main field character described in the supplied sources.

Adult body form: Small freshwater fish with a saddle or oval spot pattern across the back and sides.

Maximum size: About 150 mm, with a FishBase record of 14.5 cm standard length.

Common size: About 8.0 cm standard length.

Identification: Colour and life stages

Smaller fish are dark olive above, yellow green around the markings and silver below. Larger fish may be much darker, with a purple sheen and greyish belly.

Larvae and juveniles use open lake water. Adults are generally bottom dwelling and are associated with rocky margins and aquatic plant meadows near shore.

Identification: Similar species and survey confirmation

The supplied documents do not provide a formal comparison table with other Tasmanian galaxiids. Do not identify a small galaxiid from colour alone where several native or introduced fish may occur.

Use the saddle or large oval spot pattern together with the known range and lake margin habitat. Record photographs and retain voucher or genetic material only under the required permits and animal ethics approvals. Threatened galaxiid surveys commonly use electrofishing, small scoop nets, fine mesh fyke nets, night snorkelling and larval nets, selected to suit the habitat and minimise harm.

  • Treat any galaxiid captured in or near Arthurs Lake, Woods Lake or the nearby Lake River as a potential saddled galaxias until confirmed.
  • Use experienced fish ecologists for identification where the pattern is unclear or where other galaxiids and introduced fish are present.
  • Include connected downstream and upstream waters in the assessment because project effects may extend beyond the work footprint.

Distribution: National range

The saddled galaxias has an extremely restricted distribution in Tasmania. No occurrence outside Tasmania is given in the supplied documents.

The species is known only from Arthurs Lake and Woods Lake on the high central plateau of Tasmania, with nearby sections of the Lake River also recorded. The state and national range is therefore confined to Tasmania's Central Highlands.

The two lakes are natural lakes that were raised by dams constructed by the Hydro Electric Corporation. Fish found in parts of the Lake River are thought to be vagrants swept from the normal lake habitat by outflow releases.

States recorded: Tasmania only.

Bioregional setting: Tasmania's Central Highlands and high central plateau.

Known waters: Arthurs Lake, Woods Lake and nearby sections of the Lake River.

Distribution: Strongholds and subpopulations

Woods Lake supports an abundant population relative to Arthurs Lake. The Arthurs Lake population is uncommon and is thought to be limited at least partly by high trout predation, high water clarity and relatively low planktonic productivity.

Both lakes are considered essential to the long term survival of the species. The Lake River records do not necessarily represent a separate self sustaining population.

Woods Lake: Abundant population reported.

Arthurs Lake: Uncommon population reported.

Population size: No total population estimate is provided.

Population trend: No quantified trend is provided. Routine monitoring was recommended because rapid declines have occurred in other Tasmanian galaxiids.

Habitat

Saddled galaxias are almost exclusively lake dwelling fish. The habitat used by adults is concentrated around rocky lake margins, with aquatic vegetation and connected waters providing additional habitat for younger fish.

Adults occupy rocky lake margins and are also found among aquatic plant meadows near shore. The species is benthopelagic, using both the lake bottom and the water column.

Larvae and juveniles inhabit open water in lakes. Small numbers in nearby sections of the Lake River are considered likely to be fish displaced through outflow releases rather than evidence of a broad riverine habitat preference.

Main habitat: Natural lakes, especially rocky margins and near shore aquatic plant meadows.

Juvenile habitat: Open water in lakes.

River habitat: Nearby Lake River sections, where fish may be vagrants carried by outflow releases.

Climate: Temperate freshwater conditions. FishBase gives a reported range of 10 to 26 degrees Celsius.

Elevation: The supplied documents describe the species as occurring on Tasmania's high central plateau but do not provide an elevation range.

  • Protect rocky shorelines, shallow bays and aquatic plant meadows around the full supply levels of both lakes.
  • Assess work in connected inflows, outflows and the Lake River for changes to sediment, water quality, flow and fish movement.
  • Include habitat within 100 m of the full supply level of Arthurs Lake and Woods Lake in site planning, consistent with the Tasmanian listing statement.

Habitat: Site assessment implications

For a clearing or construction project, map the project area and all waters that could be affected indirectly, including downstream areas. The fish survey guidance recommends recording lakes, rivers, wetlands and other important aquatic habitat features before selecting survey methods.

The species has a small number of known populations. Disturbance to either lake, its shore, connected waters or water quality therefore warrants a species specific assessment rather than being treated as a routine aquatic impact.

  • Map rocky margins, shallow bays, aquatic vegetation, inflows, outflows and areas subject to water level change.
  • Assess sediment and nutrient pathways from roads, pads, stockpiles, drains, excavations and cleared ground.
  • Include water extraction and temporary drawdown in the impact assessment, even where no direct bed or bank works are proposed.

Foraging habitat

Adults feed near the bottom and around lake margins. The diet changes with life stage, with adults taking aquatic invertebrates and younger fish relying more on planktonic food.

Adults feed mainly on crustaceans and aquatic insects. FishBase describes adults as feeding on insects and crustaceans, with pelagic juveniles probably feeding on zooplankton.

Adults forage around rocky lake shores and aquatic plant meadows near the margin. Younger fish use open lake water, where plankton is available.

Adult diet: Crustaceans, aquatic insects and other insects.

Juvenile diet: Probably zooplankton and other planktonic food.

Foraging location: Rocky lake margins, near shore aquatic plant meadows and open lake water for pelagic juveniles.

Foraging range: No home range or movement distance is provided.

  • Retain rocky margins and near shore aquatic vegetation that provide feeding areas for adults.
  • Prevent avoidable turbidity, nutrient enrichment and algal blooms, which can alter feeding habitat and water quality.
  • Consider both shallow margins and open water when designing surveys, because different life stages use different parts of the lake.

Breeding habitat: Breeding biology

The species breeds in its lake habitat, but the supplied documents do not describe the exact spawning substrate, egg attachment site or nest form. Breeding appears to occur in more than one season.

The Tasmanian listing statement reports spawning at about one year of age, with both autumn and spring spawning periods. A separate account describes breeding as opportunistic, potentially occurring at any time of year, with a possible peak in late spring.

Small fish are present in Woods Lake throughout the year, with a peak in summer. The documents do not provide a clutch size, egg incubation period, gestation period, lifespan or a confirmed sex difference.

Spawning season: Autumn and spring are reported. Breeding may be opportunistic at other times, with a possible late spring peak.

Age at maturity: Generally reported as spawning at one year of age.

Clutch or litter size: Not provided.

Incubation period: Not provided.

Gestation: Not applicable to this egg laying fish and not provided.

Lifespan: Not provided. The species is described as living for several years in the general Tasmanian galaxiid survey guidance.

Sex differences: No reliable field difference between males and females is provided.

Breeding habitat: Breeding habitat features

Adults use lake margins, particularly rocky margins, while larvae and juveniles use open lake water. Protecting the connection between shallow margins and open water is therefore important during works.

The exact spawning microhabitat is not described in the supplied documents. Avoid disturbing shallow margins, rocky shorelines, aquatic vegetation and water levels during the reported autumn and spring breeding periods.

  • Do not assume that fish are absent from a work area because only adults are detected, as larvae and juveniles may be in open water.
  • Maintain water quality and avoid sudden drawdown, sediment release or nutrient inputs during breeding and juvenile recruitment periods.
  • Obtain appropriate permits before capture, handling, collection or translocation.

Sheltering habitat

The species does not use terrestrial dens, hollows, burrows or nests. Shelter and cover are provided by aquatic habitat, especially rocky margins, shallow bays and emergent or submerged vegetation.

Adults are generally bottom dwelling and occupy rocky lake margins. Where trout are abundant, saddled galaxias have been observed to be more confined to lake margins, rocky shorelines and shallow bays dominated by emergent reeds.

Aquatic plant meadows near shore provide habitat for fish, but the supplied documents do not give a required vegetation density, rock size, water depth or refuge dimensions.

Terrestrial shelter: None described. The species is fully aquatic.

Adult cover: Rocky lake margins, shallow bays and areas with emergent reeds.

Other cover: Near shore aquatic plant meadows and open water used by larvae and juveniles.

Shelter dimensions: Not provided.

  • Retain rocky margins, shallow bays, emergent reeds and aquatic plant meadows.
  • Avoid removing or burying cover at the water edge during bank works, access construction or dam infrastructure works.
  • Control sediment so that rocky substrate and aquatic vegetation are not smothered.

Threats: Introduced fish

The main documented risks are introduced predatory fish, water quality decline and hydrology change. Because the species is confined to two main lakes and nearby river sections, local impacts can affect a large part of its known range.

Brown trout have been introduced into Arthurs Lake and Woods Lake and have probably preyed heavily on saddled galaxias in both lakes. Predation is considered a major source of mortality in Woods Lake and may partly explain the smaller Arthurs Lake population.

European carp are present in Lake Sorell and Lake Crescent, about 8 km east of Woods Lake. Redfin perch are present in the Lagoon of Islands, about 2 km south west of Woods Lake. Their arrival in the saddled galaxias catchments is identified as an ongoing threat.

  • Prevent the movement or release of live fish, bait and contaminated water between catchments.
  • Include fish passage and water transfer pathways in construction planning.
  • Report any redfin perch or carp detection from Arthurs Lake, Woods Lake or connected waters to the relevant Tasmanian authorities.

Threats: Water quality and hydrology

Water quality has been a concern at Woods Lake. A diversion canal directs nutrient rich water into the lake for much of the year, and these nutrients are linked with periodic algal blooms.

Water removal for irrigation has been associated with water quality deterioration and dewatering of saddled galaxias habitat. Project drawdown, altered inflows, changed outflows and dewatering of margins should therefore be treated as direct species risks.

  • Prevent sediment, nutrient rich runoff, concrete washout, fuels and other contaminants from entering the lakes or connected streams.
  • Maintain fish habitat at the full supply level and assess impacts within 100 m of that level.
  • Assess temporary and permanent changes to lake level, inflow, outflow and connected river habitat.
  • Use erosion and sediment controls that remain effective during rainfall and high flow.

Threats: Clearing, fire and other project risks

Direct terrestrial clearing is most relevant where it removes or destabilises lake shore vegetation, increases sediment delivery or changes drainage into occupied waters. The fish survey guidance states that project areas should include places affected indirectly and downstream.

Post fire ash and sediment can enter freshwater systems. The supplied ash and sediment report treats the saddled galaxias as a threatened freshwater study species, but the described physiological experiments were not species specific, so the level of effect for this species is not quantified.

The supplied documents do not identify a species specific threat from roads, habitat fragmentation or disease. These issues should still be checked where road crossings, culverts, water transfers or fish handling are proposed.

  • Keep cleared ground, stockpiles and access tracks away from drainage lines and lake margins where practicable.
  • Design crossings to avoid barriers to fish movement and prevent dirty water entering connected habitat.
  • Use clean equipment and water transfer procedures to reduce the risk of moving fish, eggs, pathogens or invasive aquatic species.
  • Arrange specialist survey and approvals before electrofishing, netting, fish relocation or other handling.

Survey methodology: 1. Confirm habitat and survey boundaries

Saddled galaxias is a highly restricted freshwater fish found in Arthurs Lake, Woods Lake and nearby sections of the Lake River in Tasmania. Survey design must cover direct and downstream impacts to lakes, lake margins, outflows and connected streams, not only the construction footprint.

Map all lakes, shorelines, inflows, outflows, wetlands and connected streams within the project area and any area that could receive downstream impacts.

Treat rocky lake margins, aquatic plant meadows near shore and nearby sections of the Lake River as potential habitat.

Record water level, shoreline condition, substrate, aquatic vegetation, turbidity, connectivity and introduced fish presence at each survey site.

Known distribution: Arthurs Lake, Woods Lake and nearby sections of the Lake River, central Tasmania

Adult habitat: Rocky lake margins, including areas around groynes or jetties, and aquatic plant meadows near shore

Species size: Maximum length about 150 mm

Survey methodology: 2. Fyke netting in lakes

Use fine, soft mesh fyke nets in lake margins where access and conditions allow.

Set approximately 10 nets for one or two nights when targeting saddled galaxias in lakes.

Construct and set nets to Inland Fisheries Service requirements, including a screen to exclude platypus and large trout, with cod ends out of the water or buoyed.

Check nets in accordance with the approved method and release non-target animals promptly and safely.

Use this method in shallow margins, rocky shorelines and aquatic plant meadows because adults occupy nearshore habitat and juveniles may use open water.

Typical effort: Approximately 10 fine-mesh fyke nets for one or two nights

Detection notes: Adults are generally bottom dwelling and occur around rocky lake margins; larvae and juveniles may occur in open lake water

Survey methodology: 3. Electrofishing, scoop nets and night observations

Use backpack electrofishing or small scoop nets for connected streams and lake shores, with equipment operated by trained and authorised personnel under the applicable animal ethics and fisheries requirements.

Apply a standardised effort of at least 30 minutes of backpack electrofishing at each stream or lake-shore site where electrofishing is suitable.

Use the lowest effective electrofishing setting and a flat dip net so stunned fish can be slid into a partly filled bucket with minimal handling.

Consider night sampling or night snorkelling with small hand nets where safe, because some galaxiids are more active at night and may occur closer to shore.

Use daylight sampling where reliable identification and release are priorities, and record safety, access and water conditions that limit detection.

Minimum electrofishing effort: At least 30 minutes at each stream or lake-shore site

General Tasmanian galaxiid settings: Generally 60 Hz and 2 or 4 mS, with voltage commonly 200 to 700 V, adjusted to conductivity and used as low as practicable

Handling: Temporary holding in a partly filled bucket; anaesthesia only where required and approved

Survey methodology: 4. Timing, larvae and survey records

Survey during the proposed impact period and repeat when water levels, flows or access conditions could change detection.

Time supplementary surveys around autumn and spring spawning periods where the project may affect breeding or recruitment habitat, while recognising that the species can breed opportunistically at other times.

Use a fine-mesh tow net behind a boat only where approved and appropriate for detecting larvae in lake water, and preserve samples for later microscopic sorting where identification in the field is not possible.

Record the date, start and finish time, weather, water level, turbidity, conductivity, method, net locations, effort, catch, size classes, photographs and release location.

Do not rely on a negative result from one method or one visit to clear lake margins or connected waters.

Survey methodology: Minimum effort and reporting

EPBC Act status: Vulnerable

Tasmanian status: Vulnerable

National distribution in the Tasmanian temperate rainforests and highland forests zone: 100 percent

Proportion of that zone where it is likely or known to occur: 0.44 percent

  • Survey every lake, lake margin, inflow, outflow and connected stream that could be disturbed or receive downstream impacts.
  • Use approximately 10 fine-mesh fyke nets for one or two nights in suitable lake habitat, plus at least 30 minutes of backpack electrofishing at each suitable stream or lake-shore site.
  • Have all survey, capture, handling and release work completed by people with the required fisheries, animal ethics and threatened-species permissions.
  • Submit confirmed records, including negative survey results where required, to the relevant Tasmanian wildlife or biodiversity database and provide records to the project environmental officer and approving authorities.
  • Report the species under the scientific name Galaxias tanycephalus and retain evidence supporting identification.

Before habitat disturbance: Avoid and minimise habitat loss

Avoid disturbance to the two known lake populations and their connected waters wherever practicable. The species has a very restricted range, and both Arthurs Lake and Woods Lake are identified as essential to its long-term survival.

Redesign the project to avoid Arthurs Lake, Woods Lake, nearby Lake River sections, rocky lake margins, aquatic plant meadows, inflows, outflows and wetlands.

Retain natural lake margins and maintain surface-water and fish passage connections between retained habitat and connected streams.

Use the full supply level and the surrounding 100 metre area as a planning buffer for both Woods Lake and Arthurs Lake unless a site-specific assessment and approval establish a different requirement.

Avoid works that dewater, isolate, fill, shade, scour or increase sediment and nutrient inputs to lake margins and connected waters.

Planning area identified in the Tasmanian listing statement: All waters and lands within the full supply level and all lands and waters within 100 m of the full supply level at Woods Lake and Arthurs Lake

Before habitat disturbance: Approvals and project controls

Check whether the action requires referral under the EPBC Act because saddled galaxias is nationally listed as vulnerable.

Obtain Tasmanian threatened-species, Inland Fisheries Service, animal ethics and collection or handling approvals before surveys, capture, relocation or disturbance.

Prepare a fauna management plan that maps habitat, sets exclusion zones, identifies stop-work triggers and assigns responsibilities to the environmental officer, aquatic ecologist and fauna spotter catcher.

Include downstream pathways, altered water levels, pumping, sediment discharge, access tracks and temporary works in the impact assessment.

Before habitat disturbance: Timing and site preparation

Stage works so that disturbance to lake margins, inflows and outflows is avoided during periods of spawning or high recruitment where the assessment identifies those periods as sensitive.

Complete the pre-clearance aquatic survey before plant, pumping, excavation or dewatering starts.

Mark no-go habitat, the 100 metre planning area, retained aquatic vegetation, rocky margins, inflows, outflows and any approved access points on plans and on the ground.

Install exclusion fencing or other barriers where they can prevent machinery, vehicles, spoil and people entering retained habitat, and inspect them daily.

Brief all operators that a small fish may be present even when it is not detected during a survey.

During habitat disturbance: Daily controls and machinery interface

Keep machinery and sediment, nutrient and water-level controls outside retained aquatic habitat. The fauna spotter catcher must work under the aquatic ecologist's approved method because capture and relocation of this species require appropriate authorisation.

Inspect exclusion fencing, silt controls, pumps, screens, discharge points and water levels before work starts each day.

Keep machinery, fuels, concrete washout, spoil, sediment and stockpiled materials out of lakes, streams, wetlands and the approved buffer.

Use screened and fish-safe pump intakes, maintain downstream flows where required, and stop pumping if fish are at risk or if approval conditions cannot be met.

Require the fauna spotter catcher or aquatic ecologist to inspect the work area before machinery enters a new section.

Use a spotter and operator communication system that allows immediate shutdown of machinery, pumps and excavation when a fish or aquatic habitat is found.

During habitat disturbance: Handling and relocation

Do not allow untrained workers to capture, handle, retain or relocate saddled galaxias.

If a fish is found, stop the relevant work, keep it wet, minimise handling and contact the authorised aquatic ecologist or permit holder.

Relocate a captured fish only where the approval and method statement allow it, and only to nearby retained habitat with suitable water quality, depth, temperature, flow and cover.

Use a partly filled bucket for temporary holding, keep holding time as short as practicable, and avoid crowding, heat and rapid changes in water conditions.

Send injured or stressed fish to the nominated aquatic wildlife veterinarian or authorised wildlife carer where that service is available, and notify the project environmental officer and relevant authority.

During habitat disturbance: Stop-work triggers and records

Stop work immediately if saddled galaxias is found in the disturbance area, if a threatened fish is injured or killed, if an unapproved capture or relocation is required, or if sediment, nutrient-rich water or contaminated water enters retained habitat.

Stop work if pumps, screens, barriers or exclusion controls fail, or if water levels or flows fall outside the approved limits.

Record the location, date, time, observer, method of detection, photographs, fish measurements where authorised, condition, action taken, release location and names of authorised personnel.

Report any death, injury, unexpected concentration of fish, new occupied habitat or suspected introduction of trout, redfin perch or carp to the environmental officer and relevant authority without delay.

Do not restart the affected activity until the environmental officer confirms that the approval conditions and species protection measures are in place.

After habitat disturbance: Post-work inspection and monitoring

Completion of construction does not remove the risk to a small, isolated population. Confirm that retained waters remain connected and suitable, then monitor the site for delayed water-quality, flow and fish impacts.

Inspect all retained lake margins, inflows, outflows and connected streams after work and after substantial rainfall or pumping events.

Check for sediment deposition, turbidity, algal growth, nutrient inputs, dewatering, bank collapse, damaged aquatic vegetation and barriers to fish movement.

Repeat targeted fyke-net, electrofishing or visual monitoring at the approved sites and effort levels where the project could have changed habitat or water quality.

Compare catch, size classes, habitat condition and water-quality results with pre-work records, and investigate any decline or change in distribution.

After habitat disturbance: Controls, reporting and offsets

Keep exclusion fencing, sediment controls, fish screens, flow controls and access restrictions in place until the environmental officer confirms that the site is stable and no longer poses a risk.

Remove temporary crossings, pumps, spoil and barriers that could obstruct fish movement or degrade the shoreline.

Provide monitoring results, incidents, fish records, photographs, water-quality results and rehabilitation outcomes to the relevant approval agencies and Tasmanian biodiversity database.

Implement any approved offset, conservation measure or corrective action if residual impacts remain after avoidance and rehabilitation.

Rehabilitation actions: Restore lake-edge habitat and water quality

Rehabilitation should restore the shallow lake-edge conditions used by saddled galaxias and protect water quality in the two known lake systems. Do not create a new connection for trout, redfin perch or carp, and do not move fish without approval.

Reinstate stable, natural lake margins with rocky cover and shallow areas suitable for adult saddled galaxias.

Re-establish aquatic plant meadows near the shore where they were present before disturbance, using locally appropriate material and methods approved for the catchment.

Stabilise disturbed banks and drainage lines so they do not deliver sediment or nutrient-rich runoff to the lake.

Prevent dewatering of occupied habitat and maintain approved water levels, inflows, outflows and fish passage.

Do not introduce non-native fish or transfer water, equipment or aquatic material between catchments unless biosecurity controls and approvals are in place.

Rehabilitation actions: Control predators, weeds and fire impacts

Inspect and clean machinery, boats, nets and footwear before entering the catchment to reduce the risk of transferring fish, eggs, weeds, pathogens or contaminated sediment.

Monitor for redfin perch and European carp, which are identified as nearby threats, and notify the relevant fisheries authority if they are detected in or near occupied waters.

Control weeds without herbicide or other treatments entering the lake, stream or wetland.

Plan erosion and sediment controls before planned burns or vegetation works so post-fire runoff does not degrade occupied waters.

Rehabilitation actions: Success measures and follow-up

Measure rehabilitation success using stable banks, functioning inflows and outflows, no new barriers, retained or restored nearshore cover, controlled turbidity and no new nutrient or algal problems.

Repeat fish surveys at the approved effort and locations, including approximately 10 fyke nets for one or two nights in suitable lake habitat where monitoring requires capture.

Compare abundance, size classes, recruitment indicators, habitat condition and water-quality results with the pre-disturbance baseline.

Continue monitoring until the environmental officer and relevant authorities agree that the habitat is stable and the species protection objectives have been met.

Known water-quality concerns: Turbidity, nutrient levels, algal blooms and dewatering of habitat have been identified at Woods Lake

Recovery objective: Secure existing natural populations and assess options for extending the range through approved translocated populations

Sources