Modelled mid‐trophic pelagic prey fields improve understanding of marine predator foraging behaviour

Biophysical interactions are influential in determining the scale of key ecological processes within marine ecosystems. For oceanic predators, this means foraging behaviour is influenced by processes shaping the distribution of prey. However, oceanic prey is difficult to observe and its abundance and distribution is regionally generalised. We use a spatiotemporally resolved simulation model to describe mid-trophic prey distribution within the Southern Ocean and demonstrate insights that this modelled prey field provides into the foraging behaviour of a widely distributed marine predator, the southern elephant seal. From a five-year simulation of prey biomass, we computed climatologies of mean prey biomass (average prey conditions) and prey biomass variability (meso-scale variability). We also compiled spatially gridded metrics of seal density and diving behaviour from 13 years of tracking data. We statistically modelled these metrics as non-linear functions of prey biomass (both mean an..., Basin- and meso-scale metrics of prey distribution

Our study domain was the region south of 40 degrees (corresponding roughly to south of the Subtropical Front (STF)), where most elephant seal at-sea activity occurs. Within the Indian sector, female elephant seals dive to depths of, on average, 540 ± 178 m during the day and 402 ± 182 m at night (McMahon et al. 2019), which falls within the upper and lower mesopelagic depth bands (Fig. 1) (Proud et al. 2017, Trebilco et al. 2019). Therefore, we regarded the available prey field as including all those functional groups that are resident in or migrate through the both mesopelagic depth zones (Fig. 1): i.e. both migrant (2.2) and non-migrant upper mesopelagic (2.1) as well as the highly migrant (3.1) and migrant (3.2) and non-migrant (3.3) lower mesopelagic layers. Daily biomass of available prey (hereafter referred to as the available prey field) was then calculated by summing across these groups, and used to build spatial climatologie..., Uploaded Datasets

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Full Datasets

Full datasets of the SEAPODYM-MTL model are available from the European COPERNICUS Marine Environment Monitoring Service (<http://marine.copernicus.eu/services-portfolio/access-to-products/>) and are not stored here.

The full Southern Elephant Seal tracking dataset from which our density and behavioural datasets are derived are available through the Integrated Marine Observing System (IMOS) portal (<https://catalogue-imos.aodn.org.au/geonetwork/srv/eng/metadata.show>)