Animal communities and species

The area still supports a diverse range of native aquatic, semi-aquatic and terrestrial fauna although there has been a substantial decline in native fish populations. Alien fish species now make up some 96% numerically of the total abundance (ACT Government unpublished data).

The Gigerline Gorge is the present upper distribution limit of the lowland fish species. Murray cod (Maccullochella peelii peelii) Golden perch (Macquaria ambigua) and Silver perch (Bidyanus bidyanus) do not occur naturally above Gigerline gorge. The reach also contains Western carp gudgeon (Hypseleotris klunzingeri) and Australian smelt (Retropinna semoni).

Upland species are the Trout cod (Maccullochella macquariensis), Macquarie perch (Macquaria australasica), and Mountain galaxias (Galaxias olidus).

Other animals found in and around the water include the Murray river crayfish (Euastacus armatus), Platypus (Ornythorhychus anatinus), Water rat (Hydromys chrysogaster), Eastern long-necked turtle (Chelodina longicollis), Eastern water dragon (Physignathus lesueurii) and several frog species. A range of other aquatic macro-invertebrates including Shield shrimp (Triops australiensis australiensis) are also found along the reach, as well as various common terrrestrial mammals, woodland birds and reptiles.

Threatened animal species

Only remnant populations of large native fish (Murray cod, Trout cod, Macquarie perch and Golden perch) remain. Silver perch are now rare or absent. Populations of Mountain galaxias, Western carp gudgeon and Australian smelt are restricted. A species of Hardyhead (probably Unpsecked hardyhead) was recorded prior to 1917 (Lintermans 2007).

The Pink-tailed worm lizard (Aprasia parapulchella), which is found on rocky grassland slopes, is listed as vulnerable, as is the Murray river crayfish found in the faster flowing main channel where it uses the spaces between boulders and cobbles on the river bed for shelter.

Other listed threatened species that may occur include Rosenburg’s goanna (Varanus rosengergi), Quolls and Honeyeaters.

Threats to animals

Threats to animals are from loss of natural flow regime, loss of complexity of in-stream and riparian habitat, increased sediment input from upland tributaries, competition, predation and disease from alien fish (e.g. Carp, Eastern Gambusia and Redfin perch), poor water quality, barriers to fish passage, loss of aquatic vegetation and overfishing.