Modelling nearshore intertidal habitat use of young-of-the-year Pacific sand lance (Ammodytes hexapterus) in Barkley Sound, British Columbia, Canada |
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Authors: | Trevor B Haynes Clifford K L Robinson Philip Dearden |
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Institution: | (1) Marine Protected Areas Research Group, Geography Department, University of Victoria, Victoria, BC, Canada;(2) Parks Canada Agency, Western and Northern Service Centre, Vancouver, BC, Canada |
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Abstract: | The Pacific sand lance (Ammodytes hexapterus) is an ecologically important prey species for many vertebrate marine predators in the Pacific Northwest. In this study,
we examined the use of intertidal habitat by young of the year (YOY) sand lance in Barkley Sound, British Columbia. We selected
14 of the original 29 independent environmental variables for modelling based on univariate analysis for variable selection.
These were then used to model sand lance presence-absence using a classification tree approach. Based on our models we found
that sand lance avoided mud and intertidal eelgrass. For sites that had very little mud and no intertidal eelgrass, sand lance
preferred sediment size mean ≥1,918 μm or sites with sediment size mean ≤1,918 μm but with relatively well sorted sediment
(sorting values ≤2.56 SDs, used as a heterogeneity index of the substrate grain size). Adjacent subtidal characteristics were
not found to be important at this scale of study. This suggests intertidal substrate characteristics and presence-absence
of intertidal eelgrass are the main influences on occurrence of YOY in the intertidal. Our results support the hypothesis
that sand lance are associated with particular sediment types, however intertidal sediment types used by sand lance in our
study differ from known preferences of sand lance for subtidal sediment types. This difference may be due to unique habitat
constraints for intertidal versus subtidal regions. Although it is unknown if the results of this study are widely applicable,
the results begin to identify intertidal habitat features that are important for Pacific sand lance. |
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Keywords: | Classification tree Habitat model |
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