Aquatic fauna survey of the terminal section of Washpen Creek, Euston NSW

"July 2007".

Project Number: Lake Caringay Rehabilitation Project - M/BUS/213.

MDFRC item.

37 pages.

The NSW Murray Wetlands Working Group Inc. (NSW MWWG) is investigating opportunities for the rehabilitation of Lake Caringay through the return of natural flood flows to the wetland. A short-term option of pumping water to the lakebed from a permanently inundated section of Washpen Creek is also being considered. This management option will involve the repair of water leakage from an earthen block bank and a steel regulator that will allow the terminal 1.1km reach of Washpen Creek to receive an intermittent water regime rather than a permanent one. The NSW MWWG commissioned the MDFRC to undertake an aquatic survey of fish, frogs and water quality at the terminal section of Washpen Creek in Spring 2006 and Autumn 2007 to determine if there are any species of ecological significance that may be impacted by the proposed management activity. Four sites were sampled in the 1.1km Survey Area 1 (SA1) downstream of the block bank. Four sites were also sampled in Survey Area 2 (SA2), a 1.1km ‘reference’ section of Washpen Creek immediately upstream of the block bank. A total of 7,303 individual fish representing nine species were sampled with large and small fyke nets. The six native fish species consisted of freshwater catfish Tandanus tandanus, carp gudgeon Hypseleotris spp., flathead gudgeon Philypnodon grandiceps, Australian smelt Retropinna semoni, dwarf flathead gudgeon Philypnodon sp. and flyspecked hardyhead Craterocephalus stercusmuscarum fulvus, with the exotic fish being common carp Cyprinus carpio, goldfish Crassius auratus and eastern gambusia Gambusia holbrooki. The most abundant large bodied fish was freshwater catfish (n=31, 48%) followed by common carp (37%) and goldfish (15%). Freshwater catfish and flyspecked hardyhead were present only in SA2.

Five species of frog were sampled at Washpen Creek by listening for male calls and spotlighting. The surveyed species included Peron’s tree frog Litoria peroni, spotted marsh frog Limnodynastes tasmaniensis, barking marsh frog Limnodynastes fletcheri, eastern banjo frog Limnodynastes dumerili and eastern sign-bearing froglet Crinia parinsignifera. None of the species are considered threatened under state or commonwealth legislation. The threatened southern bell frog Litoria raniformis known to occur in the region was not sampled. Most of the frogs sampled in November 2006 were recorded as male calls, and no frogs were heard calling during the recording periods in April 2007. Higher numbers of frogs were observed with spotlighting in April 2007 than November 2006. The Washpen Creek water quality variables of electrical conductivity, turbidity, ammonia nitrogen, oxides of nitrogen and filterable reactive phosphorus were at levels considered “low risk” for creating adverse biological effects. Total phosphorus and pH levels were mostly below the guideline trigger values for slightly disturbed lowland rivers and are typical of other lowland river wetlands of the region. Total nitrogen concentrations exceeded guidelines for lowland rivers but were not considered a risk for wetland systems as they are typical of the Euston Lakes system and other local wetlands. Dissolved oxygen concentrations were low, particularly in SA1, and may be limiting the habitat for some biota including some species of fish. The following recommendations are made based on the findings of this study, and take into account the recent proposal for isolating all of the Euston Lakes systems as part of drought water recovery measures: An ephemeral water regime is returned to the 1.1km terminal section of Washpen Creek downstream of the block bank (Survey Area 1) pending hydrogeological advice; Assess and monitor the freshwater catfish population within the Euston Lakes system; Investigate the ecology of the section of Washpen Creek downstream of the block bank following any change in water regime; Undertake a sulfidic sediment assessment at Washpen Creek.