23 Jun 2017 New habitats recorded for the western swamp crayfish in the Southern Grampians

Back in May, Lachie and I headed out for some field work to conduct some snap shot fish surveys in two recently restored wetlands near Dunkeld – Green Swamp and Brady Swamp. Brady swamp is part of a wider wetland complex along the Wannon River, while Green Swamp is a more isolated wetland, nearby to the east. Following our recent restoration works at both sites and last year’s high rainfall, these two important swamps have retained water over the summer.

Brady Swamp (top) and Green Swamp (bottom).

Brady Swamp (top) and Green Swamp (bottom).

At Brady Swamp, small numbers of southern pygmy perch (Nannoperca australis) and mountain galaxias (Galaxias olidus) were caught, along with a couple of common yabbies (Cherax destructor). It appears likely that most natives utilised the wetland habitat for spawning late last year and subsequently moved further downstream along the Wannon River, capitalising on the extended connectivity. After hauling the nets we decided to survey a nearby dam along the northern edge of Brady Swamp that still contained water. Despite the lack of habitat, we were pretty excited to find almost 40 western swamp crayfish (Gramastacus insolitus) in the seine net. The unassuming dam is clearly a significant refuge site for Gramastacus, probably owing to the low salinity.

Western swamp crayfish

Western swamp crayfish

Key refuge site for Western swamp crayfish (left) along the northern edge of Brady Swamp. Males are easily distinguished by the presence of large, uncalcified genital papilla. (right)

Key refuge site for Western swamp crayfish (left) along the northern edge of Brady Swamp. Males are easily distinguished by the presence of large, uncalcified genital papilla. (right)

At Green Swamp, small numbers of carp gudgeon (Hypseleotris klunzingeri) were caught in the fyke nets, along with some large common yabbyies (Cherax destructor). As we sorted the catch from the last net, our Friday suddenly got a whole lot better when we found a single male Gramastacus. This significant finding further increases our growing knowledge of the ecological value of Green Swamp, which we now know supports two threatened species, the growling grass frog (Litoria raniformis) and the western swamp crayfish (Gramastacus insolitus). A great end to the week!

Lauren Veale
Lauren Veale
lauren.veale@natureglenelg.org.au