Temperature, dissolved Oxygen and Predator-Prey interactions - Prey distribution Assessment Through Characterization of feeding Habitats of Elephant Seals – TOPP-PATCHES

1 Observations in situ using the biologging technology
2 Development of Individual based models

- Demonstration of a significant relationship between the foraging behavior of elephant seals and events of bioluminescence in depth.
- Development of three individual -based models to address a predictive dimension and better understand the impact of environmental change on marine predators. One is dedicated to the migration of a cetacean in the Arctic and is based on the aggregation of food resources in summer. The model proves to be useful to better understand the potential rules of displacement of a marine predator and to simulate animal movements virtually and also to create different fields of theoretical resources that can be associated with different environmental scenarios. Another model is also developed to try to better understand the responses of individuals with different characteristics against various environmental conditions. We were looking for the individuals the most able to respond to change in distance and/or aggregation of food resources. This model is set for Antarctic fur seals but also presents a generic character and allows us to relate the life history (survival, fitness) , the characteristics of individuals and their marine environment. Finally we are working on a third model which aims to address the vertical dimension of diving predators (the 2 previous models only include the horizontal dimension). This model is developed for elephant seals and aims to determine the impact of a deepening food resources on individuals based on their inherent physiological diving capabilities.

- Several analyses to characterize foraging habitats of diving predators are currently ongoing.
- Individual based models are being developed

- Vacquié-Garcia, J., Royer, F., Dragon, A-C., Viviant, M., Bailleul, F. and C., Guinet. Foraging in the darkness of the Southern Ocean: influence of bioluminescence on a deep diving predator. PlosOne (In press)

- Vacquié-Garcia, J., Guinet, C., Bost, C-A., Handrich, Y., Royer, F. and F., Bailleul. BioPIC : a comprehensive method for detecting and characterizing biological pulses recorded by bio-logging. (En préparation)

- Bailleul, F., Grimm, V., Chion, C. and M.O. Hammill. Modeling implications of food resource aggregation on animal migration phenology. (En préparation).

- Bailleul, F., Morinay, J., Viviant, M., Hanuise, N., Coquillard, P., Massardier, L., Wajnberg, E. and C. Guinet. Dealing with directional environmental changes: Which individuals will fare better? (En préparation).

Global warming impacts the accessibility and the catch ability of fish prey in marine ecosystems. Predictive models indicate that the temperature of oceans will continue to increase in the next decades. This warming will result in the deepening of the thermocline, and increase of ocean stratification which is expected to reduce mixing processes. In addition, coupled to increasing concentration of CO2, dissolved oxygen at depth should decrease over the next decades. All these changes are expected to have substantial biological and economical consequences. Particularly, they will impact the horizontal and vertical distribution of marine resources and consequently the foraging efficiency of their natural predators and the yield of fisheries. However, the assessment of biological consequences related to climate change on marine ecosystems is clearly lacking and not easily predictable due to major uncertainties concerning the nature of the link and the mechanisms between physical and biological processes.
Much research has been conducted over the last decades to address the subject of foraging efficiency of top marine predators in relation to oceanographic conditions. However, these studies were constrained by the limitations of existing techniques mainly providing a qualitative index of foraging success, but rarely a quantitative index. Recently, new technologies have resulted in the obtaining of extensive and high resolution oceanographic data sets and the development of new analyses methods. These technologies allows while studying the at sea behaviour of top predators, the collection of invaluable oceanographic parameters over large spatial scales. Whether this approach provide an unprecedented dataset to physically and biologically characterize the marine habitat of marine predators, the lack of in situ observations of the feeding events and the absence of information on prey distribution and abundance prevented to assess properly how the spatial change in oceanographic condition impacts the accessibility, the catch ability and consequently the foraging efficiency of the top marine predators. Understanding such processes is critical to build up predictions and model to properly assess the impact of oceanographic change on top air-breathing marine predators.
The general aims of this project, is to implement accelerometers allowing to assess at high spatio-temporal resolution prey intake coupled with a new generation of loggers allowing for the fist time the recording of dissolved oxygen concentration. Using this approach we intend to assess spatio-temporal change in foraging success of elephant seals according to the heterogeneity of the oceanographic conditions encountered along the track and while diving. This task dedicated to observation represents a scientific and a technical challenge in a three dimensional environment still inaccessible. Moreover, predicting by modelling the response of individuals to environmental changes is of a crucial importance to better understand the effects on the whole population and represents currently an international concern. Therefore, the collected observations will be used in a second task dedicated to predictions as a natural experiment to better assess the likely consequences of a deepening thermocline and reduced oxygen concentration on the foraging efficiency of this deep diving predator. This post-doc will allow me to implement in France, new methods learnt while in post-doc in Canada and will provide an excellent opportunity to complete my training and to compete for research-teaching positions in France and Europe.