Krill Life Histories

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Abstract P.I. Marc Mangel OPP97-14983 Antarctic krill represent the largest harvestable population in the ocean, with annual biomass production about three times the global fish catch. In addition, most organisms in the Southern Ocean are one or two trophic levels from krill. At the broadest level, a fundamental question is: What sustains krill and allows it to be such a phenomenally successful organism? A secondary question is: What is the effect of krill harvesting by humans on krill-dependent predators? Although the maximum krill harvest by humans is small compared to that of other predators, the Convention for the Conservation of Antarctic Marine Living Resources explicitly calls for an ecosystem-based approach in which such indirect effects are considered. Of particular concern is the potential overlap of the foraging ranges of predators with the spatial distribution of harvesting activity. The proposed research has two directions. The first is the continued development of models for krill predator and krill fishery interactions. The fishery models will be of clear significance to the Scientific Committee for the Commission for the Conservation of Antarctic Marine Living Resources, and consequently, to the U.S. Antarctic Program. The model will also examine indirect food web effects at the level of the individual and the population. The second direction is the development of life history models for krill, using the methods of dynamic state variable modeling. These models will address the highly variable developmental patterns of krill, and therefore have the potential for examining the nature of bimodal size distributions and age-size relationships, both of which influence small scale population processes and fishery-predator interactions.