Potential feeding and spawning habitats of Atlantic bluefin tuna in the Mediterranean Sea

Abstract

Atlantic bluefin tuna Thunnus thynnus (ABFT) is a fish of high market value which\nhas recently become strongly overexploited, notably in the Mediterranean Sea. This area is an\nessential habitat for ABFT reproduction and growth. We present here an approach for deriving the\ndaily mapping of potential ABFT feeding and spawning habitats based on satellite-derived sea\nsurface temperature (SST) and chl a concentration. The feeding habitat was mainly derived from\nthe simultaneous occurrence of oceanic fronts of temperature and chl a content while the spawning\nhabitat was mostly inferred from the heating of surface waters. Generally, higher chl a contents\nwere found to be preferred for the feeding habitat and a minimum SST value was found for\nthe spawning habitat. Both habitats were defined by the presence of relevant oceanographic features\nand are therefore potential and functionally-linked habitats. This approach provides, for the\nfirst time, a synoptic view of the potential ABFT habitats in the Mediterranean Sea. The model\nperforms well in areas where both satellite data and ABFT observations are available, as 80% of\npresence data are in the vicinity of potential habitats. The computed monthly, seasonal and annual\nmaps of potential feeding and spawning habitat of ABFT from 2003 to 2009 are in good agreement\nwith current knowledge on ABFT. Overall, the habitat size of ABFT is about 6% of the Medi -\nterranean Sea surface. The results displayed a strong seasonality in habitat size and locations as\nwell as high year-to-year variations (30 to 60%), particularly for the potential spawning habitat,\nwhich is key information for evaluating the utility of ABFT Marine Protected Areas in the Medi -\nterranean Sea.