Use of micronekton data and models to improve ecology of top predators

Typically, studies that focus on mid-to-high trophic-level species, such as fish and marine mammals, analyse data collected using instruments designed specifically to observe only a partial aspect of a single or small group or related species. For instance, mid-trophic level mesopelagic (200 to 1,000 m) organisms, which form deep scattering layers (DSLs), can be observed using echosounders, but these instruments do not enable elucidation of food web structure. Recent developments in data collection, storage and accessibility (via online data centres and project portals), have enabled observations collected by a wide range of instruments to be integrated and analysed concurrently. The Pelagic Ecology Research Group (PERG) at the University of St Andrews has collated a global dataset of 38 kHz echosounder observations. The Southern Ocean component of this collated data were obtained primarily from the Integrated Marine Observing System (IMOS, ww.imos.org.au) and the MESOPP data portal (www.mesopp.eu), which include observations made from both fisheries and research vessels. In parallel to these developments, a database of Southern elephant seal diving data has been established, providing both CTD and time-depth data collected via bio-logging. In this study, we link together a decade’s worth (between 2004 and 2017) of Southern elephant seal dive data and echosounder observations of sound scattering layers (SSLs) to investigate fine-scale (10’s m) vertical predator-prey interactions in the Indian ocean sector of the Southern Ocean