Peter Miller & Kylie Scales 2015 Fronts Foraging Gannets Basking Sharks
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Ocean front metrics for understanding foraging locations of gannets and basking sharks Peter Miller Kylie Scales, Simon Ingram, David Sims & Steve Votier
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Ocean front metrics for understanding foraging locations of gannets and basking sharksPeter I. Miller1, Kylie L. Scales1,2, Simon N. Ingram3, David. W. Sims4, Stephen C. Votier51. Plymouth Marine Laboratory, Prospect Place, Plymouth, UK2. Environmental Research Division, National Oceanic and Atmospheric Administration, Monterey, USA3. Marine Biology and Ecology Research Centre, Plymouth University, Plymouth, UK4. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth, UK5. Environment and Sustainability Institute, University of Exeter, Cornwall Campus, Penryn, UKUnderstanding the mechanisms linking oceanographic processes and marine vertebrate space use is critical to our knowledge of marine ecosystem functioning, and for effective management of populations of conservation concern. We have studied the influence of thermal and chlorophyll fronts on basking shark and northern gannet habitat use in the UK southwest approaches, using satellite Earth observation (EO) data. We have confirmed that surface frontal activity is a predictor of basking shark presence, over both seasonal timescales and contemporaneously, and revealed the scale and variability of these associations. (Miller, Scales et al., in press; Archival Global Location Sensing (GLS) tags, random walk simulations, Generalised Linear Mixed Modelling (GLMM)). After tracking 66 breeding gannets from a Celtic Sea colony over two years, we found no evidence that they adjust their behaviour in response to contemporaneous fronts. However, foraging was more likely to occur within spatially predictable, seasonally persistent frontal zones; this suggests that gannets rely on learnt strategies for their broad scale foraging. (Scales et al., 2014; GPS tags, Area Restricted Search (ARS), Generalised Additive Models with Generalised Estimating Equations (GEE-GAM)). Our results demonstrate that composite front mapping is a useful tool for studying the influence of oceanographic features on animal movements, and highlight frontal persistence as a crucial element of the formation of pelagic foraging hotspots for mobile marine vertebrates. These studies increase the evidence base for applying EO front frequency maps as a tool to assist the designation of marine protected areas (Miller and Christodoulou, 2014).Miller, P.I., Scales, K.L., Ingram, S.N., Southall, E.J. & Sims, D.W. (in press) Basking sharks and oceanographic fronts: quantifying associations in the north-east Atlantic. Functional Ecology. doi: 10.1111/1365-2435.12423Miller, P.I. & Christodoulou, S. (2014) Frequent locations of ocean fronts as an indicator of pelagic diversity: application to marine protected areas and renewables. Marine Policy. 45, 318–329. doi: 10.1016/j.marpol.2013.09.009 Scales, K.L., Miller, P.I., Embling, C.B., Ingram, S.N., Pirotta, E. & Votier, S.C. (2014) Mesoscale fronts as foraging habitats: composite front mapping reveals oceanographic drivers of habitat use for a pelagic seabird. Journal of the Royal Society Interface, 11(100), 20140679. doi: 10.1098/rsif.2014.0679 Satellite data (e.g. SST, Chl-a, fronts) available from NEODAAS: www.neodaas.ac.uk
Transcript of Peter Miller & Kylie Scales 2015 Fronts Foraging Gannets Basking Sharks
Ocean front metrics for understanding foraging locations of gannets and basking sharks
Peter MillerKylie Scales, Simon Ingram,
David Sims & Steve Votier
Oceanic fronts
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Miller, P.I. (2009) J. Mar. Sys. 78,
327-366.
Composite front mapping
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Key Questions - gannets
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Key Questions - gannets
• Do gannets respond to contemporaneous thermal or chl-a fronts as foraging cues?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Key Questions - gannets
• Do gannets respond to contemporaneous thermal or chl-a fronts as foraging cues?
• Are broad-scale, seasonally persistent frontal zones preferred foraging habitats?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Foraging: Area-Restricted Search
2010n=17
2011n=49
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Do gannets respond to contemporaneous fronts?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
No population-level signal of ARS in association with contemporaneous thermal or chl-a fronts.
Do gannets respond to contemporaneous fronts?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Are persistent frontal zones preferred foraging habitats?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Are persistent frontal zones preferred foraging habitats?
GAMARS (0/1) per grid cell ~ front frequency + accessibility
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Are persistent frontal zones preferred foraging habitats?
Thermal front frequency Chl-a front frequency
Pro
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AR
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Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Are persistent frontal zones preferred foraging habitats?
Thermal front frequency Chl-a front frequency
Pro
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AR
SARS more likely within seasonally persistent
frontal zones (thermal and chl-a) than in other accessible regions of habitat
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Summary - gannets
Northern gannets in the Celtic Sea forage preferentially within spatially predictable, persistent frontal zones, but responses to contemporaneous fronts vary
learning and memory
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks & fronts: what we know
Sims & Quayle (1998) Nature 393, 460-464Sims et al. (2000) Proc Roy Soc B 267 (1455), 1897-1904Sims, DW et al. (2003) MEPS 248, 187-196
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Sims & Quayle (1998) Nature 393, 460-464Sims et al. (2000) Proc Roy Soc B 267 (1455), 1897-1904Sims, DW et al. (2003) MEPS 248, 187-196
Basking sharks & fronts: what we know
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks & fronts: what we know
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks and satellite fronts
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking shark tracked with GLS tag vs. fronts
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Our favourite shark stays close to the front
Distance from closest front (km)
De
nsi
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Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Do sharks forage near fronts generally?
Distance from closest front (km)
De
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Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Modelling real and random sharks
Resampling real shark presence
10 random shark tracks
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks vs. seasonal front frequency
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks vs. seasonal front frequency
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Basking sharks vs. real time factors
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Summary
•Composite front mapping is useful for investigating mesoscale oceanographic drivers of habitat selection by marine predators
•Basking sharks and northern gannets associate with mesoscale thermal fronts in UK waters
•Regional oceanography important – frontal persistence, spatial scale, gradient – influence use by foraging animals
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Extra slides
SST map
Local window
Histogram bimodality
test and threshold
Cohesion test
Cayula, J.-F., and Cornillon, P., (1992), Edge detection algorithm for SST
images. Journal of Atmospheric and Oceanic Technology, 9, 67-80.
Front detection method
Front map
Contour following
Composite front maps: revealing strong fronts
Fmean Fcomp
X
Fpersist
X
Pfront Fprox
Miller, P.I., (2009) Composite front maps for improved visibility of dynamic oceanic fronts on cloudy AVHRR and SeaWiFS data, Journal of Marine Systems.
Mean gradient
Persistence Advection / proximity
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Polovina, JJ, et al. (2000) Fisheries Oceanography 9:71-82Graham, RT, et al. (2012) PloS ONE 7(5), e363834Biuw, M, et al. (2007) PNAS 104:34,13705-13710Bost, CA, et al. (2009) Journal of Marine Systems 78:3,363-376
Sims, DW, et al. (2000) Proceedings of the Royal Society B 267:1455,1897-1904Sims, DW and Southall, EJ (2002) JMBA 82:927-928Teo, SLH and Block, BA (2010) PLoS ONE 5:5,e10756Weimerskirch, H (2007) Deep Sea Research II 54:3-4,211-223
Marine predators associate with fronts
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Do gannets respond to contemporaneous fronts?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Do gannets respond to contemporaneous fronts?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Do gannets respond to contemporaneous fronts?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Do gannets respond to contemporaneous fronts?
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Predictability
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Predictability
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Predictability
Ocean front metrics for understanding foraging locations of gannets and basking sharks [email protected]
Predictability
