BIOLOGGING DEVICES AS THE 2.0 VERSION OF NATURALIST BIONOCULARS
Studying pinniped foraging strategies and energetics with DTAGs
Pinnipeds play a top predators key role in top-down processes and are considered bio-indicators of the health of marine ecosystem. Therefore, quantifying their foraging activity and energy expenditure in relation to rapidly changing marine environments is crucial for assessing these roles. However, gathering concurrent information on the movements, prey acquisition and environment of these cryptic species is a real challenge. As a Marie Skłodowska-Curie fellow at the Marine Bioacoustics lab at Aarhus University, I study the fine scale foraging strategies of seals in relation with their biotic and abiotic environment. We combine the use of acceleration and acoustic data to quantify the links between pinnipeds foraging decisions and energetics with 3-D prey distribution, environmental features and anthropogenic activities. This multi-disciplinary project lies at the intersection of bioacoustics, cutting edge engineering tools, signal processing, ecology and physiology to determine foraging optimization in free-ranging, wild marine animals.
Collaborators - P.T. Madsen, M. Johnson & J. Teilmann
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Foraging ecology of Weddell seals
Weddell seals are the Southernmost pinnipeds. They have adopted extraordinary physiological and behavioural strategies to inhabit all year long and reproduce in one of Earth's most extreme environment. They can dive up to a thousand meters deep and hold their breath for more than one hour while looking for prey under thick sea-ice. During my PhD and beyond, we have studied the displacements, diving behaviour and fine-scale foraging strategies of these seals in relation to their environment (light, sea-ice, water masses etc.). We have developed several method to infer when and where they forage both in the vertical and horizontal dimensions. We have also recently used novel bio-logging devices to remotely access data that are usually archived thereby solving the issue of challenging device retrieval. Furthermore, we are testing other hypotheses using active acoustic.
Collaborators - J.B. Charrassin, M. Hindell, M. Johnson
Conservation sites for seabirds of the Southern Ocean
Seabirds are key consumers in marine food webs and serve a critical role as bioindicators of the state of oceanic ecosystems. However, they are among the most threatened group of birds worldwide. Species such as albatrosses and penguins (Spheniscidae) are particularly at risk, and in both families>50% of the species are threatened with extinction. Using movements data for four threatened seabird species acquired over several breeding seasons from Amsterdam Island we aimed at (1) characterise their at-sea distributions and delineate the marine Important Bird and Biodiversity Areas (mIBAs) triggered by them; (2) assess the potential threat at-sea by quantifying the overlap between seabird distribution and longline fishing efforts; (3) evaluate the coverage of identified mIBAs by marine protected areas and suggest complementary conservation actions.
Collaborators - C.A. Bost, M.P. Dias, S. Oppel
European sea bass vertical behaviours and drivers
European sea bass are widely spread in the North East Atlantic and highly targeted by both recreational and professional fisheries. However, in 2015, the European Comission has declared the Northern Stock as over-exploited. While virtually nothing is known about the ecology of wild sea bass, this raised an urgent need to fill this gap of knowledge in future perspective of better resource management. Using temperature, time, depth recorders we study the behavioural switches and periodicities of European sea bass in link with environmental factors. First, we have developped an approach coupling spectral analyses and hidden Markov models (HMM) to classify behavioural states along 1-D European seabass depth time series according to activity levels and cyclic patterns. Secondly, we aim at identifying the drivers of individuals behavioural switches by testing the influence of a set of variables directly implemented in the HMMs.
Collaborators - M. Woillez, H. de Pontual, R. Fablet