The CFRA: A Joint Assessment of South China Sea Skipjack Tuna Stocks

Perface

On the basis of our studies, we conclude that of itself the fishing pressure targeted at the adult portion of the stock at the current time in most regions of the SCS, is probably sustainable. Our major concern is the unquantified (and probably heavy) fishing pressure on juvenile SKJ, with fishing gears that target SKJ and increasingly with gears that fish for multi-species assemblages of post-larval and early juvenile pelagic species. Un-managed, these fishing pressures are inevitably causing growth overfishing, and over some time period will cause recruitment overfishing, that may already be driving the serial depletion of component populations of a SCS SKJ meta-population. The sustainability of biomass fishing to supply the feedstock for aquaculture will ultimately depend on managing fishing pressure on both juveniles and adultsat levels which provide for the maintenance of recruitment to all parts of the SCS SKJ meta population.

Conclusion 

On the basis of our studies, we conclude that of itself the fishing pressure targeted at the adult portion of the stock at the current time in most regions of the SCS, is probably sustainable. Our major concern is the unquantified (and probably heavy) fishing pressure on juvenile SKJ, with fishing gears that target SKJ and increasingly with gears that fish for multi-species assemblages of post-larval and early juvenile pelagic species. Un-managed, these fishing pressures are inevitably causing growth overfishing, and over some time period will cause recruitment overfishing, that may already be driving the serial depletion of component populations of a SCS SKJ meta-population. The sustainability of biomass fishing to supply the feedstock for aquaculture will ultimately depend on managing fishing pressure on both juveniles and adultsat levels which provide for the maintenance of recruitment to all parts of the SCS SKJ meta population.

Recommendation

• Building on the CFRA of SKJ to regularise cooperation between government and non

  government fisheries scientists among SCS coastal states. This cooperation would build 

  a shared evidence base for cooperatively managing shared fish stocks.

• Updating domestic policy to address fishing pressure on juvenile and adult SKJ 

  throughout the SCS to prevent further depletion.

• Intensifying international collaboration to identfiy cooperative measures to reduce 

  fishing pressure on juvenile size classes.

Content

Abstract

Introduction

    South China Sea Fisheries

    Cooperative South China Sea Fisheries Management Initiative

       Data-poor Fisheries Assessment 

       Skipjack Tuna

Methods

    Length-based spawning potential ratio assessment 

    Weight of Evidence Evaluation of Data-poor Fisheries

        Input Parameters

            Life History Ratios

        Size of Maturity

        Size selectivity

Results

    Vietnam 

        Purse Seine Catch

        Gillnet Fishery Catch

        Fishery Independent Surveys

     Philippines

        Region 1 

            Floating Hook & Line

            Troll Line

        Region 3 All gears

      Indonesia

      Malaysia 

      China

Discussion

      Catch Size Compositions

      Definitions of Overfishing

      Simulated Purse Seine and Gillnet Fisheries

      Symptoms of Overfishing

           The Race for Fish and Fishing Down Food Web

      Serial Depletion or Nursery Grounds

           The Need for Effective Multi-National Fisheries Management

Conclusions

Tables & Figures

References

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