Modelling the circumpolar distribution of Antarctic toothfish habitat suitability – exploring methods for resolving issues in model fitting, testing and evaluating forward projections

Lucy Robinson (1), Keith Reid (2)

1 Commission for the Conservation of Antarctic Marine Living Resources, 181 Macquarie St, Hobart, Tasmania, 7000, lucy.robinson@ccamlr.org

2 Commission for the Conservation of Antarctic Marine Living Resources, 181 Macquarie St, Hobart, Tasmania, 7000, keith.reid@ccamlr.org

Understanding and predicting the potential distribution of Antarctic toothfish at different spatial and temporal scales can make an important contribution to CCAMLR’s management of this species. The use of habitat suitability models to predict the current circumpolar distribution of Antarctic toothfish has been largely unexplored. In this paper we explore the use of Maxent models with fishery catch data and environmental data to provide a current and future circumpolar prediction of habitat suitability. Maxent is highly sensitive to biased sampling effort and the selection of background data. Hence, we tested the influence of background selection on Maxent model predictions using two approaches: (1) a random-background sampling approach across the CAMLR Convention Area and; (2) a target-group background sampling approach that aims to correct biased sampling effort. The predictions from the target-group background approach resulted in the most accurate predictions, but predictions needed to be constrained within an appropriate bathymetric range via post-processing. This resulted in an accurate and more realistic prediction of the distribution of Antarctic toothfish habitat suitability. Evidence of temporal changes in habitat suitability is explored by using different temporal partitions of the catch and environment data to fit and test the underlying models.

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