title: Mesoscale fronts as foraging habitats: composite front mapping reveals oceanographic drivers of habitat use for a pelagic seabird.
abstract: The oceanographic drivers of marine vertebrate habitat use are poorly understood yet fundamental to our knowledge of marine ecosystem functioning. Here, we use composite front mapping and high-resolution GPS tracking to determine the significance of mesoscale oceanographic fronts as physical drivers of foraging habitat selection in northern gannets Morus bassanus. We tracked 66 breeding gannets from a Celtic Sea colony over 2 years and used residence time to identify area-restricted search (ARS) behaviour. Composite front maps identified thermal and chlorophyll-a mesoscale fronts at two different temporal scales-(i) contemporaneous fronts and (ii) seasonally persistent frontal zones. Using generalized additive models (GAMs), with generalized estimating equations (GEE-GAMs) to account for serial autocorrelation in tracking data, we found that gannets do not adjust their behaviour in response to contemporaneous fronts. However, ARS was more likely to occur within spatially predictable, seasonally persistent frontal zones (GAMs). Our results provide proof of concept that composite front mapping is a useful tool for studying the influence of oceanographic features on animal movements. Moreover, we highlight that frontal persistence is a crucial element of the formation of pelagic foraging hotspots for mobile marine vertebrates.
authors.affiliation: Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK kysc@pml.ac.uk.
authors.forename: Kylie L
authors.initials: KL
authors.lastname: Scales
authors.affiliation: Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, UK.
authors.forename: Peter I
authors.initials: PI
authors.lastname: Miller
authors.affiliation: Marine Biology and Ecology Research Centre, Plymouth University, Plymouth PL4 8AA, UK.
authors.forename: Clare B
authors.initials: CB
authors.lastname: Embling
authors.affiliation: Marine Biology and Ecology Research Centre, Plymouth University, Plymouth PL4 8AA, UK.
authors.forename: Simon N
authors.initials: SN
authors.lastname: Ingram
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Enrico
authors.initials: E
authors.lastname: Pirotta
authors.affiliation: Environment and Sustainability Institute, University of Exeter, Penryn TR10 9EZ, UK s.c.votier@exeter.ac.uk.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Votier
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001717:Birds / Q000502:physiology*; D017753:Ecosystem; D008954:Models, Biological; D009792:Oceans and Seas
keywords: foraging; habitat use; marine vertebrate; oceanographic front; remote sensing; seabird