Native and invasive fish dispersal, spawning and trophic dynamics during a managed river-floodplain connection

Keller Kopf, Skye Wassens, Luke McPhan, James Dyer, James Maguire, Jennifer Spencer, Carmen Amos, Stacey Kopf, Nick S. Whiterod

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The Commonwealth Environmental Water Office, in conjunction with the NSW Department of Planning, Industry and Environment (DPIE; formerly NSW Office of Environment and Heritage), estimate that 109.8 GL (40.5 GL CEWO and 69.3 GL of NSW DPIE) of environmental water was delivered through Yanga National Park onto the Murrumbidgee floodplain. This event started in September 2018 and ended on 1/2/2019 at the 1AS regulator and 25/1/2019 from Nimmie-Caira.
Environmental flows were aimed at supporting native fish populations and waterbirds, and helping to prevent Yanga Lake from drying-out, including the protection of resident golden perch.
The environmental flow reached eight species of native fish and four invasive species across larval, juvenile and adult stages in Yanga and Tala floodplain environments. Successful floodplain spawning and recruitment of golden perch was detected in Tala Creek and the hatch-dates of recruits over-lapped with environmental water delivery. Neither spawning nor recruitment of
golden perch was detected in the main channel of the Murrumbidgee River or in Yanga Lake in 2018/19. Larval and juvenile Murray cod were collected drifting from the Murrumbidgee River into the Yanga floodplain system via the environmental flow in November and December 2018.
Following blue-green algae blooms and extreme variation in air temperature, fish-kills of common carp, golden perch, Murray cod and other species occurred upstream of Redbank Weir on the Murrumbidgee River during January and February 2019 (A. Conallin; NSW DPIE; personal communication). The fish-kill did not extend to the connected floodplain system where adult fish and juvenile recruits remained present as of March 2019 monitoring activities. Results from stable isotopes analyses and catch data indicate that spawning and recruitment of golden perch most likely occurred from within the floodplain system, rather than movement from the river channel. However, monitoring also detected widespread recruitment of invasive common carp, and their diet overlapped with recruit stages of golden perch, suggesting that the two species are in competition for food resources provided by floodplain inundation.
Original languageEnglish
Place of PublicationAlbury-Wodonga
PublisherInstitute of Land Water and Society
Commissioning bodyCommonwealth Environmental Water Office
Number of pages49
Publication statusPublished - 31 Oct 2019


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