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    A feedback management strategy for the krill fishery in Subarea 48.1

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    Número de documento:
    WG-EMM-16/48
    Autor(es):
    G.M. Watters, J.T. Hinke and C.S. Reiss
    Presentado por:
    Dr George Watters (Estados Unidos de América)
    Aprobado por:
    Dr George Watters (Estados Unidos de América)
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    Resumen

    We present a Stage-2 strategy for in-season feedback management (FBM) of the krill fishery in Subarea 48.1.  This strategy is a combination of two strategies that were separately proposed to the WG-EMM in 2015 and is based on a broad foundation of work undertaken to address a suite of action items specified by the WG-EMM.  A decision rule to adjust catches in groups of SSMUs (gSSMUs) is central to the strategy proposed here.  In “plain English” that decision rule has four components.  1) If penguin recruitment is expected to be sufficient for population maintenance, CEMP monitoring indicates acceptable predator performance during the current breeding season, and krill biomass has increased during the present summer, the local catch limit will be increased.  2). If penguin recruitment is expected to be sufficient for population maintenance but CEMP monitoring indicates a poor breeding season or krill biomass has not increased during the summer, the local catch limit will not be adjusted.  3) If penguin recruitment is expected to be so poor that the population will decline even if adult survival through the forthcoming winter is very high, the local catch limit will be decreased.  4) If penguin recruitment is expected to be so poor that the population will decline even if almost all adults survive through the forthcoming winter, the local catch limit will be set to zero.  Implementation of the FBM strategy proposed here includes defining a base catch limit for each gSSMU (there are various options for this), collecting data on predators and krill, delaying the start of the fishing season until this data-collection effort is underway, submitting the data to the Secretariat, increasing the frequency of catch and effort reporting by the fishery, having the Secretariat compute various state variables from the submitted data and applying the decision rule with the state variables relevant to each gSSMU, providing advance notice to fishing vessels about the outcomes of applying the decision rule, and adjusting the catch limit in each gSSMU.  A time line for this implementation process is proposed.  Adjusted catch limits would only apply for a single fishing season and the implementation process would restart every year.  We used historical data to conduct retrospective analyses of our FBM strategy for two gSSMUs.  These analyses demonstrate that local catch limits would have been decreased about half the time, particularly when penguin populations were known to have been in decline.  Local catch limits would not have been adjusted or might have been increased when penguin populations were stable or increasing.  The retrospective analyses also suggest that delaying the start of the fishing season but permitting some fishing to occur prior to the “adjustment date” can be a reasonable compromise between minimizing risks to krill-dependent predators and minimizing impacts on the fishery.  The FBM strategy proposed here is fully consistent with the agreed definition of a Stage-2 strategy, and we advocate that it be trialed in real life.