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Figures courtesy of Matt Oliver 10 years of data

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Sea floor

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Krill Biomass Estimate of weight (grams) of krill through water column at a single point Averaged over survey grid for each day = mean daily krill biomass

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Krill Aggregations For each aggregation we calculate: Mean depth, dimensions (L, H), nearest neighbor distance Volumetric abundance and biomass (ind. m -3 and g m -3 ) Aggregation-specific integrated biomass (g m -2 ) Biomass encounter rate (kg m -1 )

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Error bars are 2 standard errors

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Central place foraging – Minimize foraging time – Maximize energy intake Krill aggregation structure impacts foraging efficiency Depth, size, densities and distance to next aggregation are important

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Diurnal Tide Shallow Large Closer together More dense Highest biomass encounter rate Semi-Diurnal Tide Deep Small Further apart More dense Low biomass encounter rate Shallow Large Further apart Less dense Low biomass encounter rate Palmer Deep

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Summary…and more questions Nearshore Antarctic krill distribution patterns are highly variable Tide plays a role - but how? Aggregation structure seems to be affected by tide and has an impact on penguin foraging, but to what degree? What types of aggregations are penguins going after?

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Pilot Field Season Palmer Two acoustic grids within the Palmer Station boating limits: – East Grid (~13 nm, 23 km) – West Grid (~12 nm, 22 km) – Traveling at ~3-4 knots = 6-8 hours Sampling as frequently as possible Predator observations from the water – species identification, behavior

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Acoustic Grids

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