Over the past few years WG-EMM has been developing a management procedure for the krill fishery in Statistical Area 48. This procedure will involve, inter alia, subdivision of the precautionary catch limit among a set of small-scale management units. So far the Working Group has identified six candidate methods for subdividing the catch limit and rejected one of them as unsuitable (Option 1 - subdivision based on the distribution of historical catches). In recognising the need for a “staged development” of the management procedure, the Working Group has agreed to defer the development and evaluation of two further options (Option 5 - adjustable catch limits within SSMUs and Option 6 - structured fishing) until a future date. The remaining three options propose subdividing the catch limit according to the distribution of predator demand (Option 2), krill standing stock (Option 3), or the difference between these two (Option 4). In this paper we review the uncertainties relating to the spatial distribution of predator demand and krill standing stock and assess their potential implications. We consider that a strong case can be made against Option 4, which is likely to increase ecosystem risk when the underlying estimates of consumption and/or standing stock are uncertain, especially when they are biased. We suggest that the data documenting the distribution of krill standing stock are likely to be more reliable than those documenting the distribution of predator demand, leading us to favour the use of Option 3. However, we note that though Option 3 appears to be the most favourable, there is little documentary information about temporal variability in the spatial distribution of krill biomass, emphasising the need for monitoring and model-based risk assessments. Finally, we conclude that WG-EMM cannot delay the subdivision of the precautionary catch limit without incurring some risk.
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