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Automated carp removal from fishways

Ivor Stuart and John McKenzie

Arthur Rylah Institute for Environmental Research, PO Box 137, Heidelberg, Victoria 3084

Construction of fishways along the Murray River from Hume Dam to the sea, to improve fish passage, will also facilitate movement of non-native fish species, particularly common carp (Cyprinus carpio). The present project aimed to develop low cost drafting cages, exploiting the jumping behaviour of carp, with generic application in the Murray-Darling Basin (MDB). A carp separation cage was tested at Torrumbarry Weir fishway between November 2002 and February 2003. Due to drought conditions relatively few carp (16 individuals) naturally entered the fishway, but 100% of these jumped into the confinement area. A larger sample of adult carp (66 individuals) was electrofished below Torrumbarry Weir and 82% also jumped. Adult carp (335-570 mm long FL) appeared be similarly successful at jumping the four heights tested (0.1, 0.12, 0.15 & 0.2 m). None of the silver perch (Bidyanus bidyanus) (582 individuals) or Murray cod (Maccullochella peelii peelii) (12 individuals) naturally entering the fishway jumped. One golden perch (Macquaria ambigua), of 129 tested, and three bony herring (Nematalosa erebi), of 24 tested, did jump into the confinement area but only at lower jumping heights (0.1-0.15 m). These results strongly indicate that the carp separation technology is efficient at stopping carp passage in fishways and is likely to have application in the MDB. We suggest that more testing is needed when larger numbers of adult and juvenile carp are moving (ie during flooding). Additionally, the impact or removing carp from fishways should be ecologically evaluated as a ‘pressure point’ control technique within their life-history.

Room 1 Thursday 3.20 pm

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