The spawning habitats of many large marine pelagic predators are poorly known. This lack of knowledge hampers conservation efforts that are aimed at identifying critical habitats for the spawning of these species. We hypothesized that phylogenetically related species show different adaptations and respond differently to environmental and geographical cues for when and where to spawn. We tested this hypothesis on a 5 yr data set (2001 to 2005) from the Balearic Islands region (Mediterranean Sea), targeting the early larval stage of 3 abundant species of tuna: bluefin tuna Thunnus thynnus, a large migratory oceanic species; albacore T. alalunga, a smaller species; and bullet tuna Auxis rochei, often found closer to coastal areas. The spatial distribution of spawning locations at the regional scale differed for the 3 tuna species. Bluefin tuna relied heavily on environmental signals, and therefore their spawning habitats can vary depending on the environment. In contrast, the spawning habitat of albacore and bullet tuna was driven mostly by geography and was less variable over contrasting environmental conditions. These regional adaptations for spawning habitats among the 3 tuna species may play a critical role in offspring survival and species interactions, and should be taken into account when establishing conservation practices.KEY WORDS: Spawning strategy · Spawning habitat · Regional scale · Spatial distribution · Large predators · Migratory strategy · Mediterranean · Tuna Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 463: [273][274][275][276][277][278][279][280][281][282][283][284] 2012 ted dispersal abilities and complete their life cycle in relatively closed spatial areas. It is possible that within similar geographical ranges, species with different life history traits can reproduce and thrive, but also show adaptations to local spawning habitats at smaller spatial scales.The cues and clues that fish respond to in their decisions regarding when and where to spawn can be geographically and environmentally based (Bailey et al. 2004, Ciannelli et al. 2007). Some species may adapt to spawn in geographic areas where the environment tends to be more stable, and where habitat characteristics are optimal for the survival of later larval and juvenile stages. Other species may adapt toward a more opportunistic strategy and spawn within specific environmental ranges of a larger geographic area. Depending on the physical tolerances of the species, the 2 strategies can show any degree of mixing. At a regional spatial scale (e.g. around the Balearic Islands), the prevalence of one or the other spawning strategy can be correlated with specific life history traits. The important question then is how species' life history traits and spawning strategies are linked. Providing an answer to this question would allow us to generate hypotheses on how spawning strategies are regulated across a wide range of species, and thus to determine their importance in fisheries...
New monitoring technologies are being progressively implemented in open-ocean and coastal observatories. The Mediterranean Sea is a well-known, reduced-scale ocean, an ideal natural laboratory to study global ocean processes, in particular those associated with meso- and submesoscale variability, interactions with mean flows and associated ecosystem response. SOCIB, the Balearic Islands Coastal Ocean Observing and Forecasting System, is one of such observatories, a multiplatform distributed and integrated system, a facility of facilities that extends from the nearshore to the open sea. SOCIB profits from the strategic position of the Balearic Islands at the Atlantic/Mediterranean transition area, one of the “hot spots” of biodiversity in the world’s oceans, and also of societal needs in islands where preservation of the environment is essential to assure both residents’ welfare and the competitiveness of the tourist sector. SOCIB is unique in that, from peer-reviewed excellence, its mission and objectives are science-, technology-, and society-driven. These types of new marine infrastructures, because of their critical mass and sustained funding, are presently establishing new ways of international cooperation, leading to major science breakthroughs, innovations in oceanographic instrumentation, and new ways of more efficient and science-based coastal and ocean management. We describe the major elements and structure of SOCIB and present some recent scientific, technological, and society-related results that are of relevance at a global ocean scale.
An ecological niche modelling (ENM) approach was used to predict the potential feeding and spawning habitats of small (5-25 kg, only feeding) and large (>25 kg) Atlantic bluefin tuna (ABFT), Thunnus thynnus, in the Mediterranean Sea, the North Atlantic and the Gulf of Mexico. The ENM was built bridging knowledge on ecological traits of ABFT (e.g. temperature tolerance, mobility, feeding and spawning strategy) with patterns of selected environmental variables (chlorophyll-a fronts and concentration, sea surface current and temperature, sea surface height anomaly) that were identified using an extensive set of precisely geo-located presence data. The results highlight a wider temperature tolerance for larger fish allowing them to feed in the northern - high chlorophyll levels - latitudes up to the Norwegian Sea in the eastern Atlantic and to the Gulf of Saint Lawrence in the western basin. Permanent suitable feeding habitat for small ABFT was predicted to be mostly located in temperate latitudes in the North Atlantic and in the Mediterranean Sea, as well as in subtropical waters off north-west Africa, while summer potential habitat in the Gulf of Mexico was found to be unsuitable for both small and large ABFTs. Potential spawning grounds were found to occur in the Gulf of Mexico from March-April in the south-east to April-May in the north, while favourable conditions evolve in the Mediterranean Sea from mid-May in the eastern to mid-July in the western basin. Other secondary potential spawning grounds not supported by observations were predicted in the Azores area and off Morocco to Senegal during July and August when extrapolating the model settings from the Gulf of Mexico into the North Atlantic. The presence of large ABFT off Florida and the Bahamas in spring was not explained by the model as is, however the environmental variables other than the sea surface height anomaly appeared to be favourable for spawning in part of this area. Defining key spatial and temporal habitats should further help in building spatially-explicit stock assessment models, thus improving the spatial management of bluefin tuna fisheries
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