Elwood Canal biodiversity

Rehabilitating Elwood Canal and Elster Creek, Victoria:

An Assessment of Impacts on Native Freshwater Fishes

Continued

Discussion

Biodiversity Of Freshwater Fish

A total of 763 fish representing six species was recorded during this survey (Table 2). Four freshwater species were collected, two of which were migratory species and require free passage between freshwater and estuarine or marine habitats to complete their life cycles. One exotic species, namely gambusia (Gambusia holbrooki) was collected. Two additional species were collected from the estuarine reach of the catchment, namely, blue spot goby (Pseudogobius sp. 9) and yelloweyed mullet (Aldrichetta forsteri).

It is important to recognise that the composition of fish assemblages may vary temporally in response to natural variations in stream discharge, water quality, habitat structure and food availability. Consequently, the conclusions of this study are limited by the characterisation of the fish assemblage from only two survey events. Whilst this limitation is important to realise the freshwater fish assemblage recorded in this study is depauperate compared with the diversity of freshwater fish expected to occur within the catchment under natural conditions (Table 3.). The expected natural fish assemblage comprises eight native migratory species and five native non migratory species. These species display a diversity of life-hisotry strategies and ecological requirements. These are discussed below.

Table 3. Freshwater fish species expected to occur in Elster Creek and Elwood Canal and their conservation status1

Scientific Name	Common Name	Status
Native Migratory
Anguilla australis	Short-finned eel	C
Galaxias brevipinnis	Climbing galaxias
Galaxias truttaceus	Spotted galaxias
Galaxias maculatus	Common galaxias	C
Geotria australis	Pouched lamprey	C
Mordacia mordax	Short-headed lamprey	C
Prototroctes maraena	Australian grayling	V,L,v
Pseudaphritis urvilli	Tupong	C
Native Non-Migratory
Nannoperca obscura	Yarra pygmy perch	LN,L,v
Galaxiella pusilla	Dwarf galaxias	LN,L,v
Nannoperca australis	Southern pygmy perch	C
Philypnodon grandiceps	Flat-headed gudgeon	C
Retropinna semoni	Australian smelt	C

1Abbreviations denote conservation status as; LN, lower risk-near threatened; C, common; V, vulnerable (DNRE 2000b); L, listed; (Flora and Fauna Guarantee Act); v, vulnerable (ANZECC 2000)

Dwarf galaxias are classified as lower risk-near threatened (DNRE 2000b) and vulnerable (ANZECC 2000), and protected through their listing on the Victorian Flora and Fauna Guarantee Act 1988. Dwarf galaxias typically inhabit swamps and billabongs and occasionally streams (Humphries 1986, Koster 1997, McDowall 1996b). When found in streams, they inhabit bank-side vegetation out of fast current (Humphries 1983, Koehn and O'Connor 1990). The species is considered prone to threats including habitat degradation caused by swamp drainage (SAC 1991b). Dwarf galaxias lay their eggs on submerged vegetation, leaves and rocks in late winter and early spring (Koehn and O'Connor, 1990).

Yarra pygmy perch typically inhabits flowing water and well-vegetated streams (Koehn 1990, Kuiter 1996). Yarra pygmy perch are classified as lower risk-near threatened (DNRE 2000b) and vulnerable (ANZECC 2000), and protected through their listing on the Victorian Flora and Fauna Guarantee Act 1988. The species is considered prone to threats including habitat modification, in particular the removal of riparian and instream vegetation (SAC 1991a). Yarra Pygmy Perch prefer abundant cover in the form of aquatic vegetation (Allen et al. 2002) and mud substrates (Jackson and Davies 1983). Spawning occurs in mid September/October. The life history is largely unknown, but is believed to be similar to Southern Pygmy Perch with eggs laid on aquatic vegetation (Koehn and O'Connor 1990).

Southern pygmy perch typically inhabit small slow flowing streams and wetlands with abundant aquatic vegetation (Kuiter 1996) and mud substrates predominant (Jackson and Davies 1983). Southern Pygmy Perch spawn in late winter/early spring. Spawning sites are in still waters and vary from eggs randomly scattered over bottom (Llewellyn 1980) to eggs attached to plants (Koehn and O'Connor 1990).

Australian smelt typically inhabit slow flowing or still waters (Koehn 1990; McDowall 1996). Australian smelt are an actively schooling species, congregating near the surface or mid water or around the cover of aquatic plants and woody debris (Allen et al. 2002). It is uncertain whether populations of coastal drainages spend part of their life in the sea, but inland populations are entirely freshwater (McDowall 1996).

Flat-headed gudgeon are a benthic fish, typically inhabiting slow flowing or still waters, usually amongst weed or mud bottoms (Larson 1996), and frequently occurs in estuaries (McDowall 1996). Flat-headed gudgeons spawn in the spring and summer with eggs attached in a single cluster to a solid object by means of a sticky basal mass (Llewellyn 1971, Koehn and O'Connor 1990).

Australian grayling are classified as vulnerable (ANZECC 2000, DNRE 2000b) and protected through their listing on the Victorian Flora and Fauna Guarantee Act 1988. The species typically inhabits streams with a moderate flow and gravel substrate (McDowall 1996). Australian grayling has become extinct in a major part of its range attributable to the construction of dams and weirs restricting migration, and the alteration of natural stream flow and temperature regimes (SAC 1991). Its need to migrate to and from the sea to complete its life cycle makes it vulnerable to depletion as a result of barriers restricting it upstream and downstream migration (McDowall 1996). Australian grayling spawn in late summer/early autumn, with larvae drifting downstream to brackish water or estuary (Berra 1979) or see (Bell et al. 1980). Juveniles return to freshwater in October/November (Berra 1982, Koehn and O'Connor 1990).

Spotted galaxias typically inhabits the lower reaches of streams, occupying pool habitats amongst logs, boulders or overhanging banks (McDowall 1996b). Spawning takes place in freshwater amongst aquatic vegetation from autumn to winter (Allen et al. 2002). Larvae drift downstream to sea, with juveniles migrating in shoals to freshwater in the spring (Allen et al. 2002).

Climbing galaxias are most commonly found in clear, flowing water of small rocky streams, with a good forest canopy (Koehn and O'Connor 1990). They have a strong tendency to stay near the bottom, around the cover of rocks or logs (Allen et al. 2002). Populations of climbing galaxias are probably fragmented by habitat deterioration (McDowall 1996). Climbing galaxias spawn in or near the rocks and logs in which they live (McDowall 1996). Larvae drift downstream to the sea and remain there for 6 months, when juveniles then return from the sea upstream to mature (Koehn and O'Connor 1990).

Common galaxias typically inhabits slow flowing or still waters, often found in slow flowing water amongst aquatic vegetation adjacent to faster stream flows (Koehn 1990; McDowall 1996a). Adults migrate downstream on the full or new moon in the autumn or early winter to spawn among grasses and vegetation on river estuary margins, which are inundated at high spring tides (McDowall 1980). Eggs are washed down into the bases of grass clumps and left out of the water between spring tides for about 2 weeks (McDowall 1980). Larvae are washed out to sea and larval and juvenile fish live amongst submerged vegetation in shallow water (Pollard 1971). Whitebait migrate back into freshwater between September and November (Koehn and O'Connor 1990a).

Short-finned eel are common and widespread throughout south-eastern Australia and occupy a variety of habitats including rivers, creeks and wetlands (Beumer 1996), with a preference for slow silty stream habitat. Adults migrate to the sea to spawn with juveniles entering freshwater during spring and summer with mass migrations upstream (McDowall 1996).

Tupong typically inhabit the beds of slow flowing streams amongst leaf litter and debris, and often remain partly buried among rocks, logs or sand (Hortle 1979, Andrews 1996). Females migrate downstream to estuary, which is associated with increased river flow, while males migrate to outer estuary away from freshwater influence (Hortle 1979). Spawning occurs in an estuarine or marine environment. Young fish stay in lower reaches under tidal influence for 9 months, then over next 12 months they gradually migrate upstream (Hortle 1979).

Short-headed lamprey larvae (ammocoetes) burrow into areas of sand and fine silt in shallow water or near the river edge where water current is slow, while adults burrow into substrate at night and are found beneath sand or stones during the day (McDowall 1996).

Pouched lamprey are a cryptic species that are rarely caught throughout their range in Victoria. Ammocoetes burrow into soft deposits in rivers and streams, while adults are found below loose stones in small swiftly flowing rocky streams (McDowall 1996).

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