Testing methods and ecological consequences of large-scale removal of common carp Dean Gilligan, Peter Gehrke and Craig Schiller NSW Department of Primary Industries Narrandera Fisheries Centre Buckingbong Road, Narrandera, NSW 2700 Australia Water Management Fund Programs MFW6 and MUR5 August 2005 NSW Department of Primary Industries - Fisheries Final Report Series No. 77 ISSN 1449-9967 Testing methods and ecological consequences of large-scale removal of common carp. August 2005 Authors: Gilligan, D.M., Gehrke, P.C. and Schiller, C. Published By: NSW Department of Primary Industries (now incorporating NSW Fisheries) Postal Address: Cronulla Fisheries Centre, PO Box 21, NSW, 2230 Internet: www.fisheries.nsw.gov.au NSW Department of Primary Industries This work is copyright. Except as permitted under the Copyright Act, no part of this reproduction may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owners. Neither may information be stored electronically in any form whatsoever without such permission. DISCLAIMER The publishers do not warrant that the information in this report is free from errors or omissions. The publishers do not accept any form of liability, be it contractual, tortuous or otherwise, for the contents of this report for any consequences arising from its use or any reliance placed on it. The information, opinions and advice contained in this report may not relate to, or be relevant to, a reader’s particular circumstance. ISSN 1449-9967 (Note: Prior to July 2004, this report series was published as the ‘NSW Fisheries Final Report Series’ with ISSN number 1440-3544) Contents i TABLE OF CONTENTS TABLE OF CONTENTS.................................................................................................................................I LIST OF TABLES.........................................................................................................................................III LIST OF FIGURES ......................................................................................................................................III ACKNOWLEDGEMENTS..........................................................................................................................IV NON-TECHNICAL SUMMARY ................................................................................................................. V 1. INTRODUCTION .................................................................................................................................. 8 1.1. CARP IN AUSTRALIA ....................................................................................................................... 8 1.2. CARP CONTROL OPTIONS................................................................................................................. 8 1.2.1. Biological control ................................................................................................................. 9 1.2.2. Habitat manipulation ............................................................................................................9 1.2.3. Chemical control................................................................................................................. 10 1.2.4. Physical control .................................................................................................................. 10 1.3. OBJECTIVES .................................................................................................................................. 11 2. ASSESSMENT OF ORAL ROTENONE BAITS FOR CARP CONTROL IN NSW. ................... 12 2.1. INTRODUCTION ............................................................................................................................. 12 2.2. METHODS ..................................................................................................................................... 13 2.2.1. Billabong experiment .......................................................................................................... 13 2.2.2. Aquarium experiment.......................................................................................................... 14 2.2.3. Pond experiment .................................................................................................................15 2.2.4. Palatability and bait toxicity for carp................................................................................. 15 2.3. RESULTS ....................................................................................................................................... 16 2.3.1. Billabong experiment .......................................................................................................... 16 2.3.2. Aquarium experiment.......................................................................................................... 18 2.3.3. Pond experiment .................................................................................................................19 2.3.4. Palatability and management bait toxicity for carp............................................................ 20 2.4. DISCUSSION .................................................................................................................................. 21 2.5. CONCLUSIONS............................................................................................................................... 23 3. EFFECTIVENESS OF LARGE-SCALE FISHING METHODS FOR THE REMOVAL OF CARP ............................................................................................................................................. 24 3.1. INTRODUCTION ............................................................................................................................. 24 3.2. METHODS ..................................................................................................................................... 24 3.2.1. Sites ..................................................................................................................................... 24 3.2.2. Sampling methods ............................................................................................................... 24 3.2.2.1. Electro-seining.................................................................................................................................. 24 3.2.2.2. Fyke nets........................................................................................................................................... 25 3.2.2.3. Pound nets......................................................................................................................................... 26 3.3. RESULTS ....................................................................................................................................... 27 3.3.1. Carp capture efficiency....................................................................................................... 27 3.3.2. Proportion of native fish caught by different gear types..................................................... 28 3.3.3. Risk to native fish ................................................................................................................ 28 3.3.4. Cost ..................................................................................................................................... 30 3.4. DISCUSSION .................................................................................................................................. 30 3.4.1. Electro-seine ....................................................................................................................... 30 3.4.2. Pound nets........................................................................................................................... 31 3.4.3. Fyke nets ............................................................................................................................. 32 3.5. CONCLUSIONS............................................................................................................................... 32 4. THE ECOLOGICAL IMPACT OF ADULT AND JUVENILE CARP AT HIGH AND LOW DENSITIES ........................................................................................................................................... 33 4.1. INTRODUCTION ............................................................................................................................. 33 4.2. METHODS ..................................................................................................................................... 33 Methods for carp control, Gilligan, Gehrke and Schiller ii Contents 4.2.1. Site selection ........................................................................................................................33 4.2.2. Sites......................................................................................................................................34 4.2.3. Study design.........................................................................................................................34 4.3. RESULTS AND DISCUSSION ............................................................................................................35 4.3.1. Problems with enclosures ....................................................................................................35 4.3.2. Future experiments using separating barriers ....................................................................35