Project Report QO99011 Integrated Fish Stock Assessment and Monitoring Program S Hoyle, I Brown, C Dichmont, M Sellin, M Cosgrove and M McLennan Project No. 94/161 June 2000 FISHERIES RESEARCH & DEVELOPMENT CORPORATION 6.1.1.1 Data extraction ................................................................................................. 24 6.1.1.2 Categorising the data for the GLM ................................................................... 25 6.1.2 Catch sampling ..................................................................................................... 26 6 .1.2.1 Commercial fishery .......................................................................................... 27 6.1.2.2 Recreational fishery .......................................................................................... 28 6.1.2.3 Fishery-independent sampling ......................................................................... 28 6.2 Ageing........................................................................................................................... 28 6.2.1 Fish and otolith collection .................................................................................... 28 6.2.2 Otolith preparation ............................................................................................... 28 6.2.3 Otolith reading ...................................................................................................... 29 6.2.4 Ageing experiment ............................................................................................... 29 6.2.5 Validation ............................................................................................................. 29 6.2.6 Statistical procedures ............................................................................................ 30 6. 3 Estimation ofpopulation parameters (modelling) ....................................................... 31 6.3.1 Growth parameters ............................................................................................... 31 6.3 .2 Total mortality ...................................................................................................... 31 6.3.3 Natural mortality .................................................................................................. 31 6.3.4 Population length and age structure ..................................................................... 32 6.3.4.1 Estuarine species .............................................................................................. 32 6.3.4.2 Tailor ................................................................................................................ 32 6.3 .5 Age length keys .................................................................................................... 33 6.3.6 Yield per recruit. ................................................................................................... 33 6.3 .6.1 Model structure ................................................................................................. 34 6.3.6.2 Ageing error ..................................................................................................... 35 6.3.6.3 Mean length at age ........................................................................................... 35 6.3.6.4 Selectivity ......................................................................................................... 35 6.3.6.5 Length weight relationship ............................................................................... 35 6.3.6.6 Natural mortality .............................................................................................. 36 6.3.6.7 Fishing mortality .............................................................................................. 36 6.3.6.8 Optimising minimum legal size ....................................................................... 36 6.3 .7 Bootstrapping confidence intervals on recreational diary data ............................ 37 6.3.7.1 Bootstrapping methods ..................................................................................... 38 6.3.7.2 Data collection .................................................................................................. 39 6.3.7.3 Simulation ........................................................................................................ 39 6.3. 7 .4 Aspects of the analysis ..................................................................................... 40 Integrated Fish Stock Assessment and Monitoring Program ii 6.3.7.5 Data scenarios ................................................................................................... 40 6. 4 Evaluation ofalternative assessment methods - egg production method .................... 41 6.4.1 1997 Annual egg survey cruise ............................................................................ 41 6.4.2 1998 Annual egg survey cruise ............................................................................ 41 6.4.3 Monthly cruises .................................................................................................... 41 6.4.4 Plankton collection ............................................................................................... 42 6.4.5 Identification ........................................................................................................ 42 6.4.6 Analysis ................................................................................................................ 43 7 Results .............................................................................................................................. 44 7.1 Trends in commercial fishery statistics ........................................................................ 44 7 .1.1 Catches, historical and current ............................................................................. 44 7 .1.2 Catch, effort and CPUE ........................................................................................ 46 7.1.2.1 Tailor ................................................................................................................ 46 7 .1.2.2 Whiting ............................................................................................................. 49 7.1.2.3 Bream ............................................................................................................... 53 7.1.2.4 Flathead ............................................................................................................ 55 7.1.3 Standardised catch-per-unit-effort ........................................................................ 58 7.1.3.1 Bream ............................................................................................................... 58 7.1.3.2 Dusky flathead .................................................................................................. 60 7. 2 Assessment ofotolith-based age determination methods .............................................. 64 7 .2.1 Comparison ofring counts between methods and readers .................................... 64 7.2.1.1 Bream ................................................................................................................ 64 7.2.1.2 Sand whiting ...................................................................................................... 64 7.2.1.3 Golden-lined whiting ......................................................................................... 65 7.2.1.4 Dusky flathead ................................................................................................... 66 7.2.1.5 Tailor ................................................................................................................. 67 7 .2.2 Comparison ofreadability estimates between methods and readers ..................... 68 7 .2.2.1 Bream ................................................................................................................ 69 7.2.2.2 Sand whiting ...................................................................................................... 69 7.2.2.3 Golden-lined whiting ......................................................................................... 71 7.2.2.4 Dusky flathead ................................................................................................... 73 7.2.2.5 Tailor ................................................................................................................. 74 7.2.3 Age validation- marginal increment analysis ...................................................... 75 Integrated Fish Stock Assessment and Monitoring Program iii 7 .4.4.3 Dusky flathead .................................................................................................. 99 7.4.4.4 Tailor .............................................................................................................. 100 7.4.5 Catch sampling results: length-weight relationships .......................................... 101 7. 5 Bootstrapping recreational catch confidence intervals - comparison ofmethods .... 103 7.6 DEPM as an alternative assessment method/or tailor .............................................. 104 8 Discussion ....................................................................................................................... 109 8.1 The CFISH commercial fishery database ................................................................... 109 8 .1.1 Data management issues ....................................................................................