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Long-Term Variations in Bycatch Reduction Device (BRD) Effectiveness and Trawl Catch Rates in a Tropical Fish Assemblage

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Long-Term Variations in Bycatch Reduction Device (BRD) Effectiveness and Trawl Catch Rates in a Tropical Fish Assemblage ResearchOnline@JCU This file is part of the following reference: Fingerlos, Franz Martin (2012) Long-term variations in bycatch reduction device (BRD) effectiveness and trawl catch rates in a tropical fish assemblage. PhD thesis, James Cook University. Access to this file is available from: http://researchonline.jcu.edu.au/40319/ The author has certified to JCU that they have made a reasonable effort to gain permission and acknowledge the owner of any third party copyright material included in this document. If you believe that this is not the case, please contact [email protected] and quote http://researchonline.jcu.edu.au/40319/ Long-term variations in bycatch reduction device (BRD) effectiveness and trawl catch rates in a tropical fish assemblage Franz Martin Fingerlos For the research Degree of Master of Science in the Department of Marine and Tropical Biology at James Cook University of North Queensland i Acknowledgements There have been many people that have provided assistance, guidance, support and encouragement throughout the duration of this study. In particular I would like to thank my supervisor, Prof. Garry Russ, for the opportunity to learn from him, for the countless hours of correcting drafts, his humour, positive energy, honesty and integrity. Thank you for everything. For statistical advice I would like to thank Dr. Marcus Sheaves, Dr. Richard Rowe and Mr. Collin Storlie. For the receipt of commercial trawl catch data from Grid J21 I would like to thank the Department of Agriculture, Fisheries and Forestry, Queensland. To crew of the James Kirby, particularly Don Battersby, Ralph Botting and Gerard, thank you for the expert assistance and wise advice. To all students and Tutors that took the MB3150 Fisheries class in the last 15 years for data collection, sampling and species identification. To my family, in particular my parents, for their love and support throughout the entire duration of my degree. Thank you. Last but not least to all my fellow students and friends for many fun hours, various undisclosed activities and fun times in this beautiful place called Townsville. ii Table of Contents Acknowledgements ........................................................................................................................... ii Table of Contents ............................................................................................................................. iii List of Figures ................................................................................................................................... vi List of Tables: ....................................................................................................................................ix List of Appendices: ............................................................................................................................ x Abstract .......................................................................................................................................... xiii General Introduction: ........................................................................................................................ 1 The effectiveness of the Jones-Davis bycatch reduction device (BRD) in a tropical fish assemblage, in Cleveland Bay, Townsville, Australia. ................................................................................................. 8 Introduction ...................................................................................................................................... 8 Materials and Methods: .................................................................................................................. 13 Site Description: .......................................................................................................................... 13 Sampling Design: ......................................................................................................................... 15 The Jones-Davis By-Catch Reduction Device................................................................................. 18 Laboratory Analysis: .................................................................................................................... 19 Effectiveness of the Jones-Davis BRD ........................................................................................... 19 Data transformations................................................................................................................... 20 Results ............................................................................................................................................ 21 BRD effectiveness ........................................................................................................................ 21 Catch of Prawns ........................................................................................................................... 21 Total fish catch ............................................................................................................................ 23 Catch of Carangidae ..................................................................................................................... 25 Catch of Sciaenidae ..................................................................................................................... 26 Catch of Saurida spp. ................................................................................................................... 28 Catch of Leiognathidae ................................................................................................................ 29 Catch of Other fish ....................................................................................................................... 31 The Interaction between the BRD and Year Factors ..................................................................... 32 Discussion: ...................................................................................................................................... 34 Interannual Variations in Trawl Catches in Cleveland Bay and Environmental Correlates of the Variations. ....................................................................................................................................... 42 Introduction .................................................................................................................................... 42 Materials and Methods: .................................................................................................................. 47 iii Statistical Procedures .................................................................................................................. 47 Interannual Variations in catch rates of major target and bycatch groups in the trawl fishery. ..... 47 Environmental effects on catch rates of target and bycatch groups in the trawl fishery ............... 48 Rainfall effects on catch rates of target and bycatch groups in the trawl fishery. ......................... 49 Lunar effects on catch rates of major groups caught in trawls: ..................................................... 49 Results: ........................................................................................................................................... 50 Prawns ........................................................................................................................................ 50 Catch Rate of Total Fish ............................................................................................................... 51 Catch Rate of Carangidae ............................................................................................................. 52 Catch Rate of Sciaenidae: ............................................................................................................ 53 Catch Rates of Saurida spp.: ........................................................................................................ 54 Catch Rates of Leiognathidae: ...................................................................................................... 55 Catch Rates of Other Fish:............................................................................................................ 56 Moonphase: ................................................................................................................................ 60 Discussion ....................................................................................................................................... 62 The Value of Long-term Scientific Monitoring .............................................................................. 62 Interannual Variations in Catch Rates in the Trawl Fishery of Cleveland Bay................................. 63 General ....................................................................................................................................... 63 Catch Rates of the Target of the Fishery, Banana Prawns ............................................................. 64 Catch Rates of Total Fish .............................................................................................................. 67 Catch Rates of Carangidae: .......................................................................................................... 70 Catch Rates of Sciaenidae ............................................................................................................ 70 Catch Rates of Saurida spp.
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