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    A simple approach for calculating the potential yield of krill from biomass survey results

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    D.S. Butterworth (South Africa) and M. Basson (United Kingdom)
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    Estimates are calculated for the parameter λ in the yield equation Y = λ M B0 for a kri11 fishery in which both the fishery and kri11 growth are seasonal. The criterion used for the calculations is that the probability that the kri11 spawning biomass drops below 20% of its average pre-exploitation level over a 20 year period of harvesting should not exceed l0%. The value of λ depends strongly on the value of M (natural mortality) and σR (recruitment variability), and also on the relative values of the ages at maturity and first-capture. Seasonal effects seem to be of lesser importance.