Construction of a trophically complex near-shore Antarctic food web model using the Conservative Normal framework with structural coexistence (original) (raw)
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2007
Expansion of the krill fi shery in the Scotia Sea-Antarctic Peninsula region beyond the current operational catch limit requires the development and assessment of methods for subdividing the precautionary catch limit amongst smaller spatial units. This paper compiles parameters for use in the ecosystem dynamic models that are needed to assess these methods. These parameters include life history and krill consumption parameters for the fi sh, whale, penguin and seal species that feed on krill in this region. Maximum krill transport rates are also derived from the OCCAM global ocean circulation model. This parameter set, like most others, is associated with considerable uncertainty, which must be taken into account when it is used. The sources, assumptions and calculations at every stage of the compilation process are therefore detailed, and plausible limits for parameter values are provided where possible. The results suggest that fi sh are the major krill consumers in all SSMUs, with perciform fi sh taking as much krill as whales, penguins and fur seals combined and myctophid fi sh taking double that amount. However, estimates of krill consumption per unit predator biomass suggest that this is an order of magnitude higher in penguins and seals than in whales and fi sh.
2016
A development process for ecosystem modelling for species in Area IV, which is a part of the research area of JARPA and JARPAII, is introduced. Two types of modelling approaches were employed; one is a multi-species production model, and the other is the EwE, a comprehensive (whole-of-ecosystem) model. There are differences in the component species between them, but the baleen whales and krill play key roles in both. For statistical estimation in the multi-species production model, a functional response function was proposed to link the dynamics of predators (four baleen whales and crabeater seals) and prey (Antarctic krill) with between-species competitions to the prey as well as internal population competitions. The model was applied to the data on time series of the four baleen whales, crabeater seals and krill, and then a likelihood function was defined based on the data with some additional assumptions on inestimable parameters. However, the estimated population trends for the ...
2013
A development process for ecosystem modelling for species in Area IV, which is a part of the research area of JARPA and JARPAII, is introduced. Two types of modelling approaches were employed; one is a multi-species production model, and the other is the EwE, a comprehensive (whole-of-ecosystem) model. There are differences in the component species between them, but the baleen whales and krill play key roles in both. For statistical estimation in the multi-species production model, a functional response function was proposed to link the dynamics of predators (four baleen whales and crabeater seals) and prey (Antarctic krill) with between-species competitions to the prey as well as internal population competitions. The model was applied to the data on time series of the four baleen whales, crabeater seals and krill, and then a likelihood function was defined based on the data with some additional assumptions on inestimable parameters. However, the estimated population trends for the ...
2012
Developments of future scenarios of Antarctic ecosystems are still in their infancy, whilst predictions of the physical environment are recognized as being of global relevance and corresponding models are under continuous development. However, in the context of environmental change simulations of the future of the Antarctic biosphere are increasingly demanded by decision makers and the public, and are of fundamental scientific interest. This paper briefly reviews existing predictive models applied to Antarctic ecosystems before providing a conceptual framework for the further development of spatially and temporally explicit ecosystem models. The concept suggests how to improve approaches to relating species' habitat description to the physical environment, for which a case study on sea urchins is presented. In addition, the concept integrates existing and new ideas to consider dynamic components, particularly information on the natural history of key species, from physiological experiments and biomolecular analyses. Thereby, we identify and critically discuss gaps in knowledge and methodological limitations. These refer to process understanding of biological complexity, the need for high spatial resolution oceanographic data from the entire water column, and the use of data from biomolecular analyses in support of such ecological approaches. Our goal is to motivate the research community to contribute data and knowledge to a holistic, Antarctic-specific, macroecological framework. Such a framework will facilitate the integration of theoretical and empirical work in Antarctica, improving our mechanistic understanding of this globally influential ecoregion, and supporting actions to secure this biodiversity hotspot and its ecosystem services.
2014
To explore the potential effects of the toothfish fishery on the population dynamics of Antarctic toothfish and its main prey, grenadiers (Macrouridae) and icefish (Channichthyidae), we develop a spatially explicit model using a predator-prey suitability model for the Ross Sea Region. We model the age-based population dynamics of toothfish, grenadier, and icefish, and include natural mortality (M1) and predation mortality (M2), in addition to fishing mortality (F) on all three species. The model suggests that the predation release caused by the fishery effect on toothfish abundance is greater than the direct fishing mortality on both prey species and that icefish is expected to show a larger increase in biomass through time than grenadiers. It also suggests that a prey-suitability function is more likely than a Holling type II function to describe the predatory relationships in the model. We use the model to compare the predicted population changes with available abundance data for ...
Analytical solution of a model for complex food webs
Physical Review E, 2002
We investigate numerically and analytically a recently proposed model for food webs [Nature 404, 180 (2000)] in the limit of large web sizes and sparse interaction matrices. We obtain analytical expressions for several quantities with ecological interest, in particular the probability distributions for the number of prey and the number of predators. We find that these distributions have fastdecaying exponential and Gaussian tails, respectively. We also find that our analytical expressions are robust to changes in the details of the model.