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ANNEX 14 STOCK ASSESSMENT of PACIFIC BLUEFIN TUNA (Thunnus

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ANNEX 14 STOCK ASSESSMENT of PACIFIC BLUEFIN TUNA (Thunnus FINAL ISC/18/ANNEX/14 ANNEX 14 18th Meeting of the International Scientific Committee for Tuna and Tuna-Like Species in the North Pacific Ocean Yeosu, Republic of Korea July 11-16, 2018 STOCK ASSESSMENT OF PACIFIC BLUEFIN TUNA (Thunnus orientalis) IN THE PACIFIC OCEAN IN 2018 REPORT OF THE PACIFIC BLUEFIN TUNA WORKING GROUP July 2018 1 FINAL Left Blank for Printing FINAL Table of Contents 2018 Pacific Bluefin Tuna Stock Assessment ...........................................................................5 ISC PBFWG ...............................................................................................................................5 EXECUTIVE SUMMARY MAY 2018 ....................................................................................5 1.0 INTRODUCTION .............................................................................................................24 2.0 BACKGROUND ON BIOLOGY AND FISHERIES .......................................................25 2.1 Biology ...................................................................................................... 25 2.1.1 Stock Structure .............................................................................................. 25 2.1.2 Reproduction .................................................................................................. 25 2.1.3 Distribution and Movements ........................................................................ 25 2.1.4 Growth ........................................................................................................... 26 2.1.5 Natural Mortality .......................................................................................... 27 2.2 Review of Fishery ..................................................................................... 28 3.0 STOCK ASSESSMENT INPUT DATA ...........................................................................31 3.1 Spatial Stratification ............................................................................... 31 3.2 Temporal Stratification ........................................................................... 31 3.3 Fishery Definitions .................................................................................. 31 3.4 Catch ........................................................................................................ 33 3.5 Abundance Indices ................................................................................... 33 3.5.1 Overview ........................................................................................................ 33 3.5.2 CV for the CPUE Series ................................................................................ 34 3.5.3 Japanese Longline CPUE (S1, S2 & S3) ....................................................... 34 3.5.4 Japanese Troll CPUE (S5) ............................................................................ 34 3.5.5 Taiwanese Longline CPUE in Southern area (S9) ....................................... 35 3.6 Size Composition Data ............................................................................. 35 1 FINAL 3.6.1 Overview and Input Sample Size .................................................................. 35 3.6.2 Japanese Longline (Fleet 1) .......................................................................... 36 3.6.3 Japanese Purse Seines in the East China Sea (Fleet 2 and 18) and Korean Purse Seine (Fleet 3)......................................................................................................... 37 3.6.4 Japanese Purse Seine in the Sea of Japan (Fleet 4) ..................................... 37 3.6.5 Japanese Purse Seine off the Pacific Coast of Japan (Fleet 5) ..................... 37 3.6.6 Japanese Troll and Pole-and-Line (Fleet 6, 7, and 19) ................................. 38 3.6.7 Japanese Set Net fishery except for Hokkaido and Aomori Prefectures (Fleets 8 and 9) ............................................................................................................................. 38 3.6.8 Japanese Set Net fishery for Hokkaido and Aomori Prefectures (Fleets 10) and Other Fisheries (Fleet 11) ...................................................................................... 38 3.6.9 Taiwanese Longline (Fleets 12 and 17) ........................................................ 39 3.6.10 EPO Commercial Purse Seine of US Dominant Period & Transition Period (Fleet 13) and Mexico Dominant Period (Fleet 14) .......................................................... 39 3.6.11 US Recreational Fishery (Fleet 15) ............................................................. 39 3.6.12 Japanese Troll Fishery for Farming (Fleet 16) ........................................... 40 4.0 MODEL DESCRIPTION ..................................................................................................41 4.1 Stock Synthesis ........................................................................................ 41 4.2 Biological and Demographic Assumptions ............................................... 41 4.2.1 Growth ........................................................................................................... 41 4.2.2 Ages Modeled ................................................................................................. 42 4.2.3 Weight-Length Relationship ......................................................................... 42 4.2.4 Sex Ratio ........................................................................................................ 43 4.2.5 Natural Mortality .......................................................................................... 43 4.2.6 Recruitment and Reproduction ..................................................................... 43 4.2.7 Stock Structure .............................................................................................. 44 4.2.8 Movement ...................................................................................................... 44 4.3 Model Structure ....................................................................................... 45 2 FINAL 4.3.1 Initial Conditions .......................................................................................... 45 4.3.2 Selectivity ...................................................................................................... 45 4.3.3 Catchability ................................................................................................... 47 4.4 Likelihood Components ............................................................................ 47 4.4.1 Observation error structure ................................................................................. 47 4.4.2 Weighting of the Data ................................................................................... 48 4.5 Model Diagnostics .................................................................................... 48 4.5.1 Adequacy of fit ................................................................................................... 48 4.5.2 Retrospective and R0 profiling analyses ................................................................ 48 4.5.3 Convergence Criteria ......................................................................................... 49 4.5.4 Sensitivity analysis ............................................................................................. 49 4.6 Projections and Biological Reference Points ........................................... 49 4.6.1 Projections ........................................................................................................ 49 4.6.2 Biological Reference Points ................................................................................. 50 5.0 STOCK ASSESSMENT MODELLING RESULTS .........................................................52 5.1 Model Convergence ..................................................................................... 52 5.2 Model Diagnostics ....................................................................................... 52 5.2.1 Likelihood Profiles on fixed log-scale Unfished Recruitment (log R0) ........................ 52 5.2.2 Goodness-of-fit to Abundance Indices ................................................................... 53 5.2.3 Goodness-of-fit to Size Compositions .................................................................... 53 5.2.4 Retrospective Analysis ........................................................................................ 54 5.3 Model Parameter Estimates ........................................................................... 54 5.3.1 Recruitment Deviations ....................................................................................... 54 5.3.2 Selectivity .......................................................................................................... 54 5.4 Stock Assessment Results ............................................................................. 55 5.4.1 Total and Spawning Stock Biomass ...................................................................... 55 5.4.2 Recruitment ....................................................................................................... 56 5.4.3 Catch at Age ...................................................................................................... 56 3 FINAL 5.4.4 Fishing Mortality at Age ..................................................................................... 57 5.5 Sensitivity Analysis .....................................................................................
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