[IIOE2-EP39] MAhe Plateau ecosystem Survey (MAPS)

Lead Investigator :

1. Francis Marsac, Institut de Recherche pour le Developpement (IRD), MARBEC, France
    francis.marsac@ird.fr

Other Key participants (s):

1. Pascal Bach,Institut de Recherche pour le Developpement (IRD), MARBEC, France
     Pascal.bach@ird.fr
2. Vincent Lucas, Seychelles Fishing Authority, Victoria, Mahe , Seychelles
    vlucas@sfa.sc
3. Laure Corbari, Museum National d'Histoire Naturelle (MNHN), Paris, France
     corbari@mnhn.fr

Period of Project: 1 ^st October 2021 - 30 ^th November 2021

Brief description of the Project:

The Seychelles is currently developing the National Blue Economy Roadmap to diversify the economy, create high value jobs, ensure food security, and sustainably manage and protect the marine environment. Fishing is the second most important sector in the Seychelles economy after tourism. The artisanal fishery, with 1500 fishers and an annual production of 4000 tons (valued as 12.5 million USD) is of paramount socio-economic importance to the Seychellois. There are signs of overfishing for several demersal fish stocks and a rebuilding programme is underway. A Marine Spatial Planning is also being developed to allocate activities minimizing impact on ecosystems. These aimsrequire a consolidated scientific background. The MAPS cruise will perform novel multidisciplinary observations on the Mahe Plateau. It will assess trends in the abundance of demersal fish stocks by using the results of research cruises undertaken in 1979 and 1980 as a baseline, evaluate changes in carbonate system parameters from historical data and contemporary pCO2/pH and total alkalinity measurements (SDG 14.3), and finally will investigate a possible jellification of the area by comparison with previous work. MAPS will deliver through 7 specific objectives : 1) to update of the seabed topography of the Mahe Plateau; 2) to describe the circulation, physical, chemical and biological properties of the Mahe Plateau during the inter-monsoon season; 3) to investigate the spatial distribution of the demersal fish species by acoustic methods; 4) to provide abundance indicators of demersal fish stocks of major importance for the artisanal fishery by fisheries-independent methods; 5) to describe the movements of demersal fish and connectivity across the Mahe Plateau; 6) to explore hotspots of marine benthic biodiversity in selected sites; 7) to assess the degree of contamination by microplastics of the most consumed demersal fish. The measurements will include temperature, salinity, dissolved oxygen, fluorescence profiles, pH, total alkalinity, currents (S-ADCP and L-ADCP), chlorophyll pigments and macro-zooplankton abundance. Demersal fish will be tagged to investigate movements and connectivity over the Plateau. Microplastic particles will be searched by filtering water collected at various depths and in the stomach contents of the fish. MAPS will be conducted with the French R/V ANTEA, a 35 m catamaran, that can accommodate a crew of 10 scientists. The 2-month cruise will be composed of 3 consecutive legs of 18 days each. Scientists from France (IRD, National Museum of Natural History, University of La Reunion) and Seychelles (Seychelles Fishing Authority, University of Seychelles) will work together on the vessel

Region of study:

MAPS will take place on the Mahe Plateau (area: 42000 km²), also known as the Seychelles Bank, where the granite islands of the archipelago are located. The average depth of the plateau is 65 m, ranging from 25 m along the edges to 75m in the deepest area inside the plateau.