Options for allocating the precautionary catch limit of krill among small-scale management units in the Scotia Sea
Following an assessment of Antarctic krill (Euphausia superba) in the Scotia Sea, CCAMLR established a precautionary catch limit of 4 million tonnes and further adopted 15 small-scale management units (SSMUs). The intent was to subdivide the precautionary catch limit for krill among the SSMUs so as to preclude the inadvertent concentration of catches in a small portion of the surveyed area. Five options for allocating the catch limit among the SSMUs in the Scotia Sea are presented in this paper. The first four are static allocations where the allotment of catch to an SSMU is proportional to: (i) the historical catch within the SSMU; (ii) estimated predator demand in the SSMU; (iii) estimated standing stock of krill in the SSMU; and (iv) standing stock less predator demand in the SSMU. The fifth option is a dynamic allocation based on land-based predator monitoring conducted just prior to, or early in, the fishing season. For the purposes of illustration and comparison between the options, parameter estimates are made using available data, although it is recognised that considerable refinement of these estimates is possible. Qualitative conclusions are that: under the first two options a substantial portion (>65%) of the catch limit would be allocated to three or less of the SSMUs adjacent to large concentrations of land-breeding predators; under options (iii) and (iv) a similar portion of the catch limit would be directed to pelagic SSMUs beyond the foraging range of these predators but into areas where krill fishing has not regularly occurred; and under option (v), an example of an adjustable catch limit dependent on the results of ecosystem monitoring, the fishery would be restricted in some of its traditional fishing grounds during years of low krill availability. Under all five options there would be little effect on the existing fishery However, as catches increase, a trade-off may be drawn between options that displace the fishery from its current operating area, but reduce the potential for contravening the terms of the Convention, and options that do not displace the fishery, but are likely to contravene the terms of the CCAMLR Convention.
Authors: Hewitt, R.P., Watters, G., Trathan, P.N., Croxall, J.P., Goebel, M.E., Ramm, D., Reid, K., Trivelpiece, W.Z., Watkins, J.L.