The Austral Ocean abounds in considerable and yet-unexploited stocks of pelagic fish. In terms of biomass and specific diversity, the said resources are particularly outstanding in the waters around the French Austral and Antarctic. They make up the basic diet of very large predator populations (birds, pinnipedae).

Recent studies show that the Austral Ocean is subject to inter-annual variability in its physical properties, ascribable to ENSO (El Niño Southern Oscillation) and the Antarctic Circumpolar Wave. While the disastrous consequences of ENSO on tropical marine resources are well-documented, its impact on the Austral Ocean’s resources and food chains is far less-known. In the long term, the impact of climate variability remains a major unknown. These difficulties are due in part to the hugeness of the ocean zones involved and the size of the stocks at stake (200 to 400 million tonnes where myctophidae pelagic fish are concerned).

The project herein, of multidisciplinary nature, proposes to assess the impact of climate changes in the short and long terms, on the abundance, distribution and biodiversity of pelagic fish resources, using an original approach, based on the use of the main predators (marine fish, pinnipedae) as oceanographic auxiliaries. The research zone will be the Indian portion of the Austral Ocean, in particular the French Austral and Antarctic Lands (overseas departments and territories, the Kerguelen and Crozet Islands, primarily), where several fisheries are currently developing.

Three research avenues will be explored: I) a simulation of the abundance and spatio-temporal distribution of marine resources (at the secondary trophic level); II) a comparison between simulated series of prey abundance with the bio-indicator parameters of marine predators, found at the top of the trophic networks; III) a predictive approach to the effect of climate change, based on an integrated model operating at different levels of forcing on the ocean-climate system. The specific regional habitats of the resources will be forced using predictions over 200 years, on a coupled Austral ocean/atmosphere model, including anthropic CO2 scenarios, in order to explore the potential responses of pelagic fish stocks in the Indian Ocean, and including the TAAF Economic Zone.

The bio-indicative information on predators will be derived from specific study of their food activity in the deep sea, through the use of miniaturised sensors and emitters (CEPE-CNRS and CEBC-CNRS data). Analysis of this monitoring data (seasonal and inter-annual) will make it possible to study i) the spatial breakdown of myctophidae fish resources, at different scales, ii) estimate the relative abundance and density of the said fish, by measuring the predators’ fishing efforts (catch-per-unit effort data, for instance).

The climate variability in the relevant ocean zones will be analysed using data from spatial remote detection and reference hydrological stations, incorporated into the CLIVAR programme and by spatial remote detection. The distribution of prey to the fish under consideration will be established using models developed by the LODyC laboratory (“drilling trophic transfer model”).

This integrated project, based on multidisciplinary research and cutting-edge methods, is the first enabling a predictive approach to the potential impact of climate change (in the short and long term) on very significant Austral Ocean resources, in particular in the economic zone of overseas France involved.