So far, I have been extremely lucky to collaborate with enthusiastic and talented people. The main projects I was involved in are briefly described below:
- 2008-2011: IPSOS-SEAL project : « Investigating the vulnerability of Southern productivity to climate change in using Southern elephant seals as bioindicators and oceanographic vectors »
Principal collaborators: C. Guinet (PI) , P. Monestiez, S. Blain, P. Gaspar, M. Authier
Polar marine ecosystems are amongst the most vulnerable to climate change, with conflicting evidence on how the biological productivity of the Southern Ocean will respond to global warming. The IPSOS-SEAL project aimed at assessing the spatio-temporal vulnerability of productivity of the SO with direct consequences on the amount of CO2 ‘fixed’ by the biological pump, and on the biology of top marine predators.
The studied geographic region was the Indian Sector of the Southern Ocean. Southern Elephant Seal are one of the main top-predators of the Southern ocean. Females from the Kerguelen Islands were fitted with a new generation of satellite-relayed data loggers: over a 4-full year period (2007-2010), main oceanographic parameters (temperature, salinity and fluorescence) were acquired throughout the upper 1000 m of the water column. Most data was acquired in two productive subsystems: the Frontal Zone, located between the Subtropical and Polar Fronts, and the Marginal Ice Zone.
As part of IPSOS-SEAL, my PhD project investigated the changes in fine scale movement and diving behaviour of female elephant seals equipped with satellite-relayed data loggers. Various statistical methods were used to estimate the foraging effort and success along tracks and dives of the seals. The most favourable foraging zones were significantly related to the presence of both cyclonic and anti-cyclonic eddies. Elephant seals were shown to use the centre and edges of cyclonic eddies but only the edges of the anti-cyclonic ones and adjusted their diving behaviour accordingly.
The project was funded by the French national research agency (ANR). It is part of the “Vulnerabilité: Milieu et Climat” (VMC) program 2007.
- 2012 – 2015 : MyctO-3D-MAP « Myctophid assessment in relation to Oceanographic conditions : a 3 Dimension Density Distribution approach combing Modelling-, Acoustic- and Predators’ data. »
Principal collaborators: Y. Cherel (PI), C. Guinet, G. Duhamel, P. Monestiez, C. Cotté, F. d’Ovidio, P. Lehodey, A. Conchon
The project proposes an innovative way of investigating myctophid biomass distribution and the potential impact of environmental changes on a major component of the mesopelagic ichthyofauna. An inter-disciplinary and inter-organizations program has been implemented by using a combination of approaches :
1) the use of air-breathing marine predators (penguins and seals) as myctophid indicators
2) gathering information on myctophids in situ independently from the animals, using more conventional means, such as the collection and quantification at sea of the resource using acoustic methods completed by net hauls to confirm species identification
3) 3D characterisation of myctophid habitats using oceanographic parameters collected by predators, by in situ conventional oceanographic means and by satellites
4) this data driven approach has been completed by modelling aiming at i) reconstructing the 3D distribution of myctophid biomass, and ii) assessing how environmental variability (global change) should affect the myctophid habitats and thus top marine predators.
As part of MyctO-3D-MAP, I have focused on the 4th approach by using a Spatial Ecosystem And Population Dynamic Model (SEAPODYM) that describes spatio-temporal dynamics of mid- and top-trophic level populations (here myctophids and southern elephant seals) under the influence of environment (and fishing if need be) in an Eulerian framework. The simulations are driven by the bio-physical environment predicted from coupled physical-biogeochemical ocean models (here GLORYS2). The maximum likelihood estimation methodology allows robust parameter estimation, hence enables the use of the model as a predictive and management application tool.
The project was funded by the French national research agency (ANR).
- 2011 – 2014: EURO-BASIN « European Basin-scale Analysis, Synthesis and INtegration »
Principal collaborators : M. St John (PI), P. Lehodey, I. Senina, H. Arrizabalaga
In a multidisciplinary international effort, EURO-BASIN focuses on the variability, potential impacts, and feedbacks of global change and anthropogenic forcing on the structure, function and dynamics of the North Atlantic as well as various key species influencing carbon sequestering and ecosystem functioning. The ultimate goal of the programme is to manage North Atlantic systems in a sustainable manner following the ecosystem approach.
As part of EURO-BASIN, I have focused on the underlying spatial dynamics and habitat utilisation of Atlantic exploited fish populations. Key questions remain to discriminate between the impact of fishing and the influence of climate variability on the population biology and to improve spatio-temporal stock assessments and subsequent management. In this study, I have applied an improved version of SEAPODYM (Spatial Ecosystem And Population Dynamic Model) to the North Atlantic albacore tuna population (Thunnus alalunga) and international fisheries to investigate the past, present and future dynamics of one of the main North Atlantic resources. In order to estimate the fishing impact, a first optimised parameterisation was achieved using historical catch data for the last 50 years and environmental fields predicted from a coupled bio-physical model (NEMO-PISCES) forced by the atmospheric reanalysis NCEP. A second configuration has then been used to forecast the future of albacore tuna populations under an IPCC scenario for the 21th century.
The project was funded by the European FP7 scheme (Collaborative project; Large Scale Integrated Project, ENV.2010.2.2.1-1 North Atlantic Ocean and associated shelf-seas protection and management options).
- 2012 – 2014 : Hydrography and Jack Mackerel stock in the South Pacific
Principal collaborators : N. Hintzen (PI), P. Lehodey, I. Senina, A. Bertrand, A. Corten
For the last 50 years, the Chilean Jack Mackerel (CJM, Trachurus murphyi) stock has been heavily exploited in the entire South Pacific. In addition to a likely multi-national overexploitation, the current precipitous decline of CJM population could be explained by climate-driven decadal fluctuations as observed for other small pelagic species (anchovies, sardines etc.). Furthermore, previous studies on the stock structure of CJM showed a mismatch between an assumed one-stock-population and the biological reality. Since ignoring population structure and dynamics may negatively impact stock assessments and hence management effectiveness, this study has focused for the first time on the dramatic changes in CJM population under the influence of both environment and fishing.
I have used the Spatial Ecosystem And Population Dynamic Model (SEAPODYM) to test the one-stock-population hypothesis and then investigate interannual to decadal variability in CJM population in relation with Pacific climatic modes (ENSO, PDO). Two model configurations of the South Pacific basin were used, one at coarse resolution (2°) for a long historical time series and another at high resolution (0.25°) including mesoscale activity. A unique multi-national dataset, combining effort-catch data and associated size frequencies, was used to optimize the model parameters. The model successfully predicted known spatio-temporal dynamics of the species with a good fit to historical fishing data. Our results disclose the CJM population structure and highlight the sensibility of CJM recruitment to the documented decay of ENSO intensity since 1999. These first results enable the use of Seapodym as a predictive and management application tool to test, in future work, various CJM spatial management strategies.
- 2013 – 2015 : Coca-Loca « Connectivity of Loggerhead turtle (Caretta caretta) in Western Indian Ocean : Implementation of local and regional management »
Principal collaborators : S. Ciccione (PI), J. Bourgea, P. Gaspar, M. Dalleau, M. Lalire
With habitats largely scattered in the Western Indian Ocean region, the loggerhead marine turtle (Caretta caretta) is very susceptible to bycatch in fisheries, ingestion of plastic debris and boat strikes. At island Reunion, first mitigation measures have recently been implemented to reduce the impact of these anthropogenic threats on marine turtles. The objective of the Coca-Loca project has been to improve our knowledge on this sea turtle species in order to further develop, amplify and extent efficient local and regional conservation measures to Mayotte and the whole West Indian region.
As part of COCA-LOCA, I have focused on studying the oceanic migration pathways and the connectivity between populations of the main known breeding sites of the western Indian Ocean. I used Individual-based models to simulate dispersion of hatchlings from the main nesting sites of the Indian Ocean. Collaborations in working with individual satellite tracking, genetic and isotopic data helped to study the oceanic movements of loggerhead turtles present in the territorial waters of Reunion and Mayotte.
The project was funded by the French development agency (AFD).
- 2015 – 2016 : Effects of offshore pile driving on marine mammals abundance in the German Bight
Principal collaborators : J. Tougaard, M. Brandt, A. Diedrichs
European governments aim to further the expansion of offshore wind energy in environmentally sustainable ways. In German waters, noise-intensive construction and operation of offshore wind farms is subject to special legal requirements for nature conservation, e.g. reduced marine species disturbances and injuries. Between 2009 and 2014, eight offshore wind farms with over 400 foundations were built in the German part of the North Sea. Comprehensive data has been collected with passive acoustic monitoring and visual aerial surveys to estimate the abundance and distribution of marine mammals in the study area. In addition, the dataset includes the detailed deterrence and noise protection measures during the foundations piling.
This study is the first to combine all commercial windfarm datasets in the German North Sea EEZ. In collaboration with wind farm developers and consultancy agencies, we have estimated the avoidance behaviour of harbour porpoises in relation to piling sound levels, duration and cumulative effects (when piling occurs simultaneously in different wind farms). Focusing on large spatio-temporal scales, we have helped determining the direct impacts of piling on porpoise abundance and seasonal trans-regional migrations. The final report is available here.