Optimising exclusion screens to control exotic carp in an Australian lowland river
Karl A. Hillyard A C , Benjamin B. Smith B , Anthony J. Conallin A B and Bronwyn M. Gillanders AA Southern Seas Ecology Laboratories, School of Earth and Environmental Sciences, Darling Building, DX 650 418, University of Adelaide, SA 5005, Australia.
B Inland Waters and Catchment Ecology Program, SARDI Aquatic Sciences, PO Box 120, Henley Beach, SA 5022, Australia.
C Corresponding author. Email: karl.hillyard@adelaide.edu.au
Marine and Freshwater Research 61(4) 418-429 https://doi.org/10.1071/MF09017
Submitted: 28 January 2009 Accepted: 6 September 2009 Published: 27 April 2010
Abstract
Carp exclusion screens (CES) are used to restrict adult common carp from entering wetlands, thereby minimising their ecological impacts and spawning and recruitment potential, but there is marked variation in current CES design and management. We quantified current CES designs, dimensions and locations within the Murray–Darling Basin, Australia. Directional fyke nets at inlets of six permanently inundated wetlands were used to identify fish using wetlands and therefore potentially vulnerable to CES. Morphometric data from captured fish were then used to design CES that excluded sexually mature carp. The ability of optimised and existing CES designs to exclude large-bodied fishes that used wetlands was then assessed. Fifty-four CES with eight mesh designs and varied dimensions were identified. We recorded 18 species comprising 212 927 fish in the wetland inlets. Two optimised meshes to exclude sexually mature carp were developed: a 44-mm square grid mesh and a ‘jail bar’ mesh with 31.4-mm gaps. Modelling revealed that up to 92% of carp could be excluded by either optimised mesh design, although few young-of-year carp were caught. Optimised and existing CES designs would also exclude 2–65% of large-bodied native fishes. Optimised CES may allow localised carp control without restricting passage of some key native fishes.
Additional keywords: control, Cyprinus carpio, introduced species, management, Murray–Darling Basin, physical barrier, rehabilitation.
Acknowledgements
We greatly appreciate the help of Bess Hillyard and David Wilson in the preparation of this manuscript, Michael Decelis and Leigh Thwaites for assistance in the field, Mike Copeland, Kathryn Stanislawski and Paul Stribley for help with accessing sites and many landholders who allowed access to the sites on their property. Adrienne Frears, Michael Harper, Anne Jensen, Deb Nias, Ken Smith and Tracey Steggles provided the location and details of many screens throughout the Basin. We also thank Andrew Boulton and three anonymous reviewers whose constructive comments significantly improved the manuscript. This research was funded by the Murray–Darling Basin Commission (MDBC Project MD746) and University of Adelaide Divisional Scholarships (to K.A.H. and A.J.C.) and was undertaken under the University of Adelaide Animal Ethics permit number S-063–2006.
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