2013

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  • PAW13_DOCX Recommended reading Tooltip


    Reading list for 2013 Pre-assessment Workshop.

  • PAW13_DOCX Draft schedule Tooltip


    The draft schedule for the 2013 Preparatory Stock Assessment Workshop.

  • PAW13_DOCX Preparatory Stock Assessment Workshop Notice 1 Tooltip


    Preparatory Workshop for 2013 WCPFC Stock Assessments, SPC Headquarters, Noumea, New Caledonia, 8-12 April 2013

    In 2013 the Oceanic Fisheries Programme (OFP) of SPC is contracted by WCPFC to complete stock assessments for: silky shark, blue shark, and southwest Pacific swordfish, as well as progress work on reference points and in response to the independent review of the 2011 bigeye tuna stock assessment. This work will be presented at the Scientific Committee in August 2013. In preparation, OFP is hosting a technical workshop to discuss key issues related to these tasks.

    The meeting is scheduled for 8-12 April 2013 and will be held at SPC Headquarters in Noumea.

  • PAW13_PDF Independent Review of 2011 WCPO Bigeye Tuna Assessment Tooltip


    Independent Review of 2011 WCPO Bigeye Tuna Assessment, James Ianelli, Mark Maunder and André E. Punt

    The Panel (see Appendix A for panel biographies) conducted a review of the 2011 assessment of bigeye tuna (BET) for the western and central Pacific, including the data inputs, the settings for the reference model and the settings for the sensitivity tests, based on the final Terms of Reference (Appendix B). Prior to the meeting Dr Shelton Harley provided an annotated version of key questions related to each ToR (included as second part of Appendix B). The Panel was provided with a set of background documents (Appendix C) prior to the meeting of the Panel, as well as MULTIFAN-CL (MFCL) input and output files, and code to view these files.

  • PAW13_PDF SPC-OFP Response to the Independent Review of the 2011 Bigeye Tuna Assessment Tooltip


    SPC-OFP Response to the Independent Review of the 2011 Bigeye Tuna Assessment, SPC-OFP, Secretariat of the Pacific Community, Noumea, New Caledonia

    This is the second formal independent review undertaken of a stock assessment conducted by SPC?OFP in the past two years. The earlier review was a desk review coordinated by the Center for Independent Experts based at the University of Miami. The current review was an on?site panel review that involved extensive interaction between assessment staff and the review team. In our view, this was a much better review process, and has provided sound advice for the further development of the bigeye and other assessments.

  • PAW13_PDF Management Framework Tooltip


    Management Framework, SPC-OFP

    This paper describes a generic management framework, explains the key role of Management Objectives in driving this framework, issues of uncertainty, and the roles and responsibilities involved with developing each of the framework elements.

  • PAW13_PDF Guiding Principles: Development of Reference Points for WCPO Fisheries Tooltip


    Guiding Principles: Development of Reference Points for WCPO Fisheries, SPC-OFP

    This paper describes the utility of setting reference points to guide rational fisheries management and notes the current state of development for the Western and Central Pacific Ocean (WCPO) fisheries.

  • PAW13_PDF Evaluating Options: Rules to Guide Harvest Management Decisions Tooltip


    Evaluating Options: Rules to Guide Harvest Management Decisions, SPC-OFP

    This paper describes a process for evaluating alternative management strategies (e.g., managing allowable catch levels to ensure selected targets are reached and maintained) and describes progress towards the development of harvest control rules (HCRs) for Western and Central Pacific Ocean (WCPO) fisheries.

    This process requires input from managers and stakeholders to identify management objectives, candidate target reference points, options for harvest control rules, and the criteria against which their performance should be evaluated. The Scientific Committee has identified potential appropriate biological limits to exploitation (limit reference points), and scientific evaluations can compare and contrast the potential consequences of alternative harvest management strategies to allow stakeholders to select the strategy that best meets agreed objectives.

  • PAW13_PDF Progress on the Updated Silky Shark Stock Assessment in the WCPO Tooltip


    Progress on the Updated Silky Shark Stock Assessment in the WCPO, Oceanic Fisheries Programme, Secretariat for the Pacific Community

    The purpose of this paper is to provide an update on progress since SC8 towards an updated assessment for silky shark in the WCPO. This paper does not include detailed data or analysis descriptions – these will be provided in the working paper(s) for the full assessment provided to SC9. In this paper were compare the original and updated Kobe plot describing the stock status (Figure 1). Note that for the shark assessments for WCPFC, we have preferred to describe stock status with a large number of model runs (that include different assumptions and data sets) to capture uncertainty.

  • PAW13_PDF Preliminary Analysis of the Potential Impacts of Wire Traces on Shark Catches in WCPO Tuna Tooltip


    Preliminary Analysis of the Potential Impacts of Wire Traces on Shark Catches in WCPO Tuna Longline Fisheries, Oceanic Fisheries Programme, Secretariat for the Pacific Community

    In reviewing the stock assessments conducted in 2012 for silky and oceanic whitetip sharks, SC8 noted both the a) concerns over the status of the stocks, and b) the large impact that non-target longline fisheries are estimated to have. For these reasons, SC8 recommended consideration of mitigation measures as providing the best opportunity to improve stock statu

  • PAW13_PDF Update of Progress Towards a Stock Assessment for Swordfish in the Southern WCPO Tooltip


    Update of Progress Towards a Stock Assessment for Swordfish in the Southern WCPO, Oceanic Fisheries Programme, Secretariat for the Pacific Community

    The purpose of this paper is to provide an update on progress towards an assessment for swordfish in the South Pacific Ocean region of the WCPF-Convention area. This paper summarizes the progress reached at SC8 (documented in SC8-SA-WP-08) and more recent progress since August. This paper does not include detailed data or analysis descriptions – these will be provided in the working paper(s) for the full assessment provided to SC9.

  • PAW13_PDF Spatial Size Data Stratification for Length-based Stock Assessments Tooltip


    Spatial Size Data Stratification for Length-based Stock Assessments, Simon D. Hoyle and Adam D. Langley

    Length data from the Japanese distant-water and offshore longline fleets are available aggregated in spatial strata of 10 degrees of latitude by 20 degrees of longitude, and more recently 5 degrees by 10 degrees (Figure 1). In previous yellowfin assessments, quarterly length frequency distributions were derived for the principal longline fisheries weighted by the spatial distribution of the quarterly catch from the individual fishery. However, there is considerable spatial variation in the sizes of longline-caught yellowfin and bigeye tuna within individual regions of WCPO stock assessments. There have also been large shifts through time in the spatial distribution of both longline catch and size sampling. These changes have influenced the composite regional-specific length compositions. Length sample locations aggregated by decade for yellowfin tuna are illustrated in Figure 1. Locations are even more variable at the year-quarter scale used in stock assessments, but it is the long-term shifts in sample locations that have the greatest effects on stock assessment outcomes (Harley et al. 2010).

  • PAW13_PDF Analyses of Japanese Longline Operational Catch and Effort for Bigeye and Yellowfin Tuna Tooltip


    Analyses of Japanese Longline Operational Catch and Effort for Bigeye and Yellowfin Tuna in the WCPO, Simon D. Hoyle and Hiroaki Okamoto

    Japanese longline (JPLL) operational catch and effort data for bigeye and yellowfin tuna were analyzed, in a collaboration between the Secretariat of the Pacific community (SPC) and the National Research Institute of Far Seas Fisheries (NRIFSF). The objectives were to a) improve understanding of the factors affecting catch rates, b) to develop, test and apply new methods for estimating indices of abundance, and c) to estimate abundance indices for bigeye and yellowfin tuna, for use in 2011 stock assessments for bigeye and yellowfin tuna stocks in WCPO. Data were analyzed separately for offshore and distant water vessels in each region. Figures are presented showing changes in many aspects of JPLL fisheries and tuna catches through time. A new method was developed to identify swordfish targeted effort before HBF data become available in 1976. Through time, effort has concentrated into some areas and reduced in others, and this has affected past abundance indices. A method for addressing this effort concentration was tested and applied. The effects of progressive changes since 1976 in the vessel composition of the fleet were estimated for both bigeye and yellowfin tuna. These effects have increased average catchability for yellowfin tuna in all regions, and for bigeye tuna in regions 1, 3, and 4, during the period 1976-2010. They have reduced average catchability for bigeye tuna in regions 2 and 5. Abundance indices were developed for the stock assessments of yellowfin and bigeye tuna in the WCPO for regions 1 to 6, based on data for the offshore fleet (region 1 and 3) and the distant water fleet (regions 2, 4, 5, and 6).

  • PAW13_PDF Spatial Distribution Measures for the Analysis of Longline Catch and Effort Data Tooltip


    Spatial Distribution Measures for the Analysis of Longline Catch and Effort Data, S. J. Harley

    Several spatial indices were applied to raised aggregate 5x5 degree square and month longline catch and effort data for bigeye, yellowfin, and albacore tunas from the three main distant-water longline fleets: Japan, Korea, and Taiwan, for the period 1950-2007. Indices considered included Gulland’s index, which measures the extent to which effort occurs in the regions where highest CPUE was encountered for a species. Interesting patterns were found between regions and fleets that might provide insights into targeting behaviour and the potential for hyperstability (i.e. increasing catchability as abundance declines). Other indices were considered, but not included in the paper due to space limitations and should be considered in future work.

  • PAW13_PDF Spatial and Temporal Trends in Yellowfin and Bigeye Longline CPUE for the Japanese Fleet i Tooltip


    Spatial and Temporal Trends in Yellowfin and Bigeye Longline CPUE for the Japanese Fleet in WCPO, Adam D. Langley

    Catch and effort data from the Japanese longline fleet represent a key input into the stock assessments of yellowfin and bigeye for the WCPO (Hampton et al 2005a, 2005b). The assessments encompass separate regions and for the 2005 assessment an equivalent regional structure, comprising six regions, was used for both yellowfin and bigeye tuna (Figure 1). These regions were defined based on the distribution of catch and spatial distributions in CPUE aggregated over time.

  • PAW13_PDF Progress Towards a Stock Assessment for Swordfish in the southern WCPO including Standardi Tooltip


    Progress Towards a Stock Assessment for Swordfish in the southern WCPO including Standardized CPUE for Spanish Swordfish Fleet, Shelton Harley, Pierre Kleiber, and Simon Hoyle

    The purpose of this paper is to summarize progress towards the assessment for swordfish in the southwest and south?central Pacific Ocean for 2012 that was requested by WCPFC8 in March 2012. The aim of this assessment is to both update the southwest Pacific assessment conducted in 2008 and conduct the first assessment for the south central Pacific Ocean after previous attempts failed.

  • PAW13_PDF Terms of Reference SPC for 2013 Pre-assessment Workshop Tooltip


    PAW13_PDF Terms of Reference SPC for 2013 Pre-assessment Workshop

  • PAW13_PDF Review of species and size composition estimation for the western and central Pacific purs Tooltip


    Review of species and size composition estimation for the western and central Pacificpurse seine fishery, P.L. Cordue, Center for Independent Experts

    A review of the methods and procedures used by the Secretariat of the Pacific Community to estimate species and size composition of the three main tuna species (yellowfin, skipjack, and bigeye) in the purse seine fishery in the western and central Pacific Ocean was conducted by two independent CIE appointed reviewers. The review consisted of a pre-meeting review of documents, participation in a review meeting in Noumea, New Caledonia, from 22–25 October 2012, and the preparation of an independent report by each reviewer.

  • PAW13_PDF Review of SPC Estimation of Species and Size Composition of the Western and Central Pacifi Tooltip


    Review of SPC Estimation of Species and Size Composition of the Western and Central PacificPurse Seine Fishery from Observer-based Sampling of the Catch, Joseph E. Powers, Center for Independent Experts

    The current estimation methods for determining purse seine catch by species in the Western Pacific Ocean were reviewed through the review of documents, listening to scientific presentations on the subject, interviewing key personnel, exploring the data and examining raw logsheets. Additionally, a simulation model of set operations was created to make initial evaluations of biased brailing and sampling processes.

  • PAW13_DOCX 2013 ISSF Stock Assessment Workshop: Harvest Control Rules and Reference Points for Tuna Tooltip


    2013 ISSF Stock Assessment Workshop: Harvest Control Rules and Reference Points for Tuna RFMOs

    Management strategies include monitoring, stock assessment, harvest control rules, reference points and management actions. The International Seafood Sustainability Foundation convened a workshop to review the current status of the adoption of these elements into the decision-making process by five the Tuna RFMOs and to make recommendations for harmonizing and facilitating the process among RFMOs. Of the five RFMOs, CCSBT has formally adopted a management strategy (management procedure) for decision-making. The other four RFMOs are making substantial progress to identify and test key elements of management strategies, such as reference points (limit and target) and harvest control rules. This work is being done primarily by the RFMO science bodies, sometimes without a formal Commission mandate. The workshop reports on key issues that should be kept in mind when developing and testing management strategies: Data and models, the treatment of FMSY as a target or a limit, testing of the strategy, and implementation. The workshop concluded that management strategies have worked quite well elsewhere in fisheries, and that there is no technical constraint to advance them in the tuna RFMOs. This could be done in many cases with relatively simple, existing tools. The report contains specific recommendations on limit and target reference points, harvest control rules, and other considerations for management strategy evaluations. A glossary of terms is also included.

  • PAW13_PDF Recent developments in the MULTIFAN-CL stock assessment software Tooltip


    WCPFC-SC8-2012/SA-IP-01 Recent developments in the MULTIFAN-CL stock assessment software, Nick Davies, Dave Fournier, John Hampton, Pierre Kleiber, Simon Hoyle, Fabrice Bouyé, and Shelton Harley

    MULTIFAN-CL (MFCL) is a statistical, age-structured, length-based model routinely used for stock assessments of tuna and other pelagic species. The model was originally developed by Dave Fournier of Otter Research Ltd for application to south Pacific albacore tuna (Fournier et al. 1998).

    MFCL is typically fitted to total catch, catch rate, size-frequency and tagging data stratified by fishery, region and time period. Recent tropical tuna assessments (e.g. Davies et al. 2011; Hoyle et al. 2011, and Langley et al. 2011) encompass a time period of 1952 or 1972 to 2011 in quarterly time steps, and model multiple separate fisheries occurring in 3 to 6 spatial regions. The main parameters estimated by the model include initial numbers-at-age in each region (usually constrained by an equilibrium age-structure assumption), the number in age class 1 for each quarter in each region (the recruitment), growth parameters, natural mortality-at-age (if estimated), selectivity-at-age by fishery (constrained by smoothing penalties or splines), catch (unless using the catch-conditioned catch equation), effort deviations (random variations in the effort-fishing mortality relationship) for each fishery, initial catchability and catchability deviations (cumulative changes in catchability with time) for each fishery (if estimated). Parameters are estimated by fitting to a composite likelihood comprised of the fits to the data and penalized likelihood distributions for various parameters.

    Each year the MFCL development team works to improve the model to accommodate changes in understanding of the fishery, to fix software errors, and to improve model features and usability. This document records changes made since August 2011 to the model and other components of the MFCL project both for the current release version (1.1.4.2), and the current unreleased development version, and updates the report for the previous period, 2010-11, (Davies et al. 2011).

  • PAW13_PDF Purse seine catch review [McArdle] Tooltip


    Consultancy Report, Brian McArdle

    Objective: To improve the estimation of species and size composition of the western and central Pacific purse seine fishery from observer based sampling of the catch

  • PAW13_DOCX Progress on F-based limit reference points for WCPO tuna species Tooltip


    Progress on F-based limit reference points for WCPO tuna species

    Introduction

    The Eighth Regular Session of the Scientific Committee (SC8) noted that WCPFC8 adopted a hierarchical approach to identifying the key limit reference points for the key target species as follows, where levels are based upon the biological knowledge available for the stock in question:

    Level LRPs Application
    Level 1 FMSY and BMSY  
    Level 2 FX%SPR0 and 20%SBcurrent,F=0 Bigeye, South Pacific albacore and Yellowfin tuna
    Level 3 20%SBcurrent,F=0 Other key target species

    The hierarchy of biomass-based limit reference points was subsequently adopted at WCPFC9.

    Paragraph 304 of the SC8 Summary Report requested that, using the most recent stock assessment models for south Pacific albacore, bigeye tuna, and yellowfin tuna, analyses be undertaken to identify the appropriate values of 'X' for each species in the Level 2 fishing mortality-based LRP of Fx%SPR0, for consideration at SC9. This document proposes the approach to be used to undertake this work, for discussion at the 2013 SPC Pre-Assessment Workshop.

  • PAW13_DOCX Definition of time periods for calculating reference levels of unfished biomass Tooltip


    Definition of time periods for calculating reference levels of unfished biomass

    This paper describes several alternatives for defining an ‘appropriate’ time period over which to calculate reference levels of unfished spawning biomass.  The implications of using time periods based on environmental or biological characteristics are explored for the main tuna species and striped marlin in the WCPO. Recall that in Busan, South Korea SC8:

    1. 1. recommended that biomass-based limit reference points (LRPs) for BET, YFT, south Pacific ALB, SKJ, and MLS be set at 20%SBrecent,F=0; and
    2. 2. called for the development of an ‘appropriate’ time period over which to calculate a reference level for unfished spawning stock biomass.

    SBrecent,F=0 can be thought of as the average theoretical level of the adult population (spawning stock) present if we had never fished over some ‘recent’ time frame (say from t1 to t2). We say ‘average’ because prevailing environmental conditions can have a large impact on the biomass we see from year to year, so it is likely that even if we weren’t fishing, the level of unfished spawning biomass would also vary over time. The calculation of SBrecent,F=0 is based on a historical average of unfished spawning stock biomass over a time period thought to best represent current and likely future average environmental and stock productivity conditions.  The purpose of this paper is to aid in the selection of such an ‘appropriate’ time period for each species.  Time periods that were investigated included those based on environmental conditions, species generation times, and indicative trends in recruitment and unfished spawning stock biomass.

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