University of Wollongong Theses Collection University of Wollongong Theses Collection University of Wollongong Year Key biological parameters and commercial fishery for ocean leatherjackets ‘Nelusetta ayraudi’ (Monacanthidae) off the coast of New South Wales, Australia Marcus E. Miller University of Wollongong Miller, Marcus, Key biological parameters and commercial fishery for ocean leather- jackets ’Nelusetta ayraudi’ (Monacanthidae) off the coast of New South Wales, Aus- tralia, MEnvSc thesis, School of Biological Sciences, University of Wollongong, 2007. http://ro.uow.edu.au/theses/26 This paper is posted at Research Online. http://ro.uow.edu.au/theses/26 KEY BIOLOGICAL PARAMETERS AND COMMERCIAL FISHERY FOR OCEAN LEATHERJACKETS Nelusetta ayraudi (MONACANTHIDAE) OFF THE COAST OF NEW SOUTH WALES, AUSTRALIA. Marcus Emmett Miller A thesis submitted in fulfilment of the requirements for the award of the degree of Master of Environmental Science, School of Biological Sciences University of Wollongong, NSW, Australia. September 2007 CERTIFICATION I, Marcus Emmett Miller, declare that this thesis, submitted in fulfilment of the requirements for the award of Masters of Environmental Science, in the Department of Biological Sciences, University of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. Signature: Marcus Emmett Miller Date: TABLE OF CONTENTS LIST OF FIGURES.............................................................................................................................. i LIST OF TABLES ............................................................................................................................. iv ABSTRACT.........................................................................................................................................v ACKNOWLEDGEMENTS .............................................................................................................. vii CHAPTER ONE GENERAL INTRODUCTION...............................................................................1 1.1 Rationale................................................................................................................................6 1.2 Objectives..............................................................................................................................8 1.3 Study Area.............................................................................................................................9 CHAPTER TWO LEATHERJACKET FISHERIES........................................................................10 2.1 Leatherjacket Commercial Fisheries...................................................................................10 World Fisheries ..........................................................................................................................10 Australian Fisheries....................................................................................................................12 State Fisheries other than New South Wales .............................................................................16 2.2 Review of NSW fishery ......................................................................................................21 2.3 Conclusion...........................................................................................................................38 CHAPTER THREE AGE AND GROWTH .....................................................................................39 3.1 Introduction .........................................................................................................................39 3.2 Materials and methods ........................................................................................................42 Validation of an ageing method .................................................................................................47 Age estimation using sagittal otoliths ........................................................................................49 Estimates of growth....................................................................................................................52 3.3 Results .................................................................................................................................54 Development of an ageing technique.........................................................................................54 Validation of ageing method......................................................................................................58 Age estimation using sagittal otoliths ........................................................................................62 Growth estimates........................................................................................................................68 3.4 Discussion ...........................................................................................................................75 3.5 Conclusion...........................................................................................................................86 CHAPTER FOUR REPRODUCTION .............................................................................................87 4.1 Introduction .........................................................................................................................87 4.2 Materials and methods ........................................................................................................90 Study area/sampling design........................................................................................................90 Processing of samples ................................................................................................................90 Seasonality .................................................................................................................................90 Size at maturity...........................................................................................................................92 Observations of reproduction.....................................................................................................92 4.3 Results .................................................................................................................................94 Seasonality of reproduction........................................................................................................94 Size at sexual maturity ...............................................................................................................97 Relationship between total length (mm) and gonad weight (g) .................................................99 Additional Observations...........................................................................................................102 4.4 Discussion .........................................................................................................................106 CHAPTER FIVE GENERAL DISCUSSION..................................................................................114 LITERATURE CITED ....................................................................................................................122 i LIST OF FIGURES Figure 1.1 The ocean leatherjacket (Nelusetta ayraudi) a) Female, b) Male and c) Juvenile.............2 Figure 1.2 Map of study locations along the coast of New South Wales, Australia...........................9 Figure 2.1 Catches of leatherjackets from the Commonwealth Trawl Fishery – formerly called the South East Trawl Fishery (SET), 2001 – 2006 (Source: AFMA 2006).............................................14 Figure 2.2 Catches of leatherjackets from the Great Australian Bight Trawl Fishery 2001 – 2006 (Source: AFMA 2006). ......................................................................................................................15 Figure 2.3 Catches of ocean leatherjackets from the Commonwealth Trawl Fishery and Great Australian Bight Trawl Fishery – by state trawl fleets (Source: AFMA 2006). ................................16 Figure 2.4 a) Total commercial catch of ocean leatherjackets in South Australia. Early years with no data indicate confidential data (< 5 licences), b) Total targeted catch of ocean leatherjackets by trap fishermen licensed to capture fish, c) Total targeted effort and CPUE. Years with no data indicate confidential data (< 5 fishers) (Source: South Australian Research and Development Institute - SARDI). These figures do not contain leatherjacket catches from non-targetted fisheries such as the southern rock lobster fishery..............................................................................................................17 Figure 2.5 Total catch of leatherjackets by fishing method, Western Australia (Source: WA Fish, Government of Western Australia - Department of Fisheries 2007). ................................................21 Figure 2.6 History of ocean leatherjackets caught from fish/prawn trawls and demersal fish/lobster traps in NSW (Source: NSW DPI 2006)............................................................................................23 Figure 2.7 History of ocean leatherjacket catches divided into northern and southern zones of NSW (Source: NSW DPI 2006)...................................................................................................................23 Figure 2.8 Fishing zones: 1)