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Modelling habitat use suggests static spatial exclusion zones are a non-optimal management tool for a highly mobile marine mammal

Abstract

Understanding how animals use the space in which they are distributed is important for guiding management decisions in conservation, especially where human disturbance can be spatially managed. Here we applied distribution modelling to examine common dolphin (Delphinus sp.) habitat use in the Hauraki Gulf (36°S, 175°E), New Zealand. Given the known importance of the area for foraging and nursing, we assessed which variables affect Delphinus occurrence based on generalised additive models (GAMs), and modelled probability of encounter. Behavioural information was included to assess habitat use by feeding and nursing groups and determine whether persistent hotspots for such activities could be identified and meaningfully used as a spatial management tool. Using data collected from dedicated boat surveys during 2010–2012, depth and sea surface temperature (SST) were frequently identified as important variables. Overall, seasonal predictive occurrence maps for the larger population resembled predictive maps of feeding groups more than nursery groups, suggesting prey availability has important implications for the distribution of Delphinus in this region. In this case, static spatial exclusions would not be the best management option as the core areas of use identified for these activities were large and shifted temporally. It appears that at the scale examined, most of the Hauraki Gulf is important for feeding and nursing rather than specific smaller regions being used for these functions. In cases where static management is not the optimal tool, as suggested here for a highly mobile species, a dynamic approach requires more than a boundary line on a map.

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The datasets analysed during the current study are available from the corresponding author on reasonable request.

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Acknowledgements

Funding for this work was provided by the Department of Conservation (Auckland), Massey University, Auckland Council and Golden Contracting Whangaparaoa. SLD was the recipient of a Massey University Institute of Natural and Mathematical Sciences doctoral scholarship. Data logging software was freely available from CyberTracker Conservation (https://www.cybertracker.org). We thank Weimin Jiang for assistance in obtaining SST data. SLD thanks the Great Barrier Island local community, in particular, the Motu Kaikoura Trust and Great Barrier Island Marine Radio, for support in the field. Special thanks go to all volunteers who assisted with boat surveys.

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Correspondence to Sarah L. Dwyer.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

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S. L. Dwyer and M. D. M. Pawley contributed equally to the manuscript

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Dwyer, S.L., Pawley, M.D.M., Clement, D.M. et al. Modelling habitat use suggests static spatial exclusion zones are a non-optimal management tool for a highly mobile marine mammal. Mar Biol 167, 62 (2020). https://doi.org/10.1007/s00227-020-3664-4

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  • DOI: https://doi.org/10.1007/s00227-020-3664-4

Keywords

  • Common dolphin
  • Delphinus
  • Predictive mapping
  • Species distribution modelling
  • Spatial management