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Rueda L.,Spanish Institute of Oceanography | Assuti E.M.,Spanish Institute of Oceanography | Alvarez-Berastegu D.,Balearic Islands Coastal Observing and Forecasting System | Hidalgo M.,Spanish Institute of Oceanography
Ecosphere | Year: 2015

Fish condition indices can be used as biological indicators of the health of individuals and are influenced by numerous external and internal drivers. Like most essential biological traits, they are very sensitive to the spatial heterogeneity occurring in marine ecosystems, which appears at many observational scales. This brings out different ecological processes that can only be revealed either regionally or locally. The scale-dependent spatial variability concerns not only environmental factors, but also anthropogenic activities such as fishing. Understanding these relationships is crucial for improving the spatial management of marine resources, because fish condition considerably affects the sustainability of populations. We explore the influence of density-dependent (intra-specific competition) and densityindependent variables (surface chlorophyll a concentration and fishing impact) on fish condition of three species of harvested gadoids (Merluccius merluccius, Phycis blennoides and Micromesistius poutassou) of the benthopelagic communities off the Balearic Islands (western Mediterranean). This area is characterized by high spatial heterogeneity in the environmental processes and fishing impact. Results show contrasting responses in body condition to the investigated covariates, with species-specific and ontogenetic differences sensitive to the spatial scale of analysis. Some of these responses occur at regional level, while others are more sensitive to local variation. Intra-specific competition shows a very clear effect, which depends on the ontogeny, identifying aggregation areas for recruits and limitation of resources for older individuals. Surface chlorophyll a has always a species-specific regional effect, despite gadoids have a more benthic behavior. Fishing effort displays a heterogeneous impact on fish condition. While spatially contrasting effects are observed at local scale, non-linear regional patterns occur, with positive effects of fishing pressure at intermediate levels. Models analyzing the influence of external drivers in essential fish biological traits such as body condition should consider the spatial variation in responses, especially in highly heterogeneous areas where anthropogenic activities occur. Failing to do so may hide local ecological processes that can be crucial for the persistence of fish populations, which is of paramount relevance for the regional assessment and spatial management of marine exploited resources. Copyright: © 2015 Rueda et al. Source


Muhling B.A.,University of Miami | Reglero P.,Spanish Institute of Oceanography | Ciannelli L.,Oregon State University | Alvarez-Berastegui D.,Balearic Islands Coastal Observing and Forecasting System | And 3 more authors.
Marine Ecology Progress Series | Year: 2013

Despite being well adapted for feeding in cold water on their North Atlantic feeding grounds, Atlantic bluefin tuna undertake long migrations to reach warm, low productivity spawning grounds in the Gulf of Mexico and Mediterranean Sea. Environmental conditions within spawning areas have been presumed to benefit larval survival, through appropriate feeding conditions, and enhanced larval retention and growth rates. However, field collections and studies to explore the potential mechanisms are rare. In this study, a comparison of the environmental characteristics of both spawning sites was completed using standardized environmental data and modeling methods. Predictive models of larval occurrence were constructed using historical larval collections, and environmental variables from both in situ and remotely sensed sources. Results showed that larvae on both spawning grounds were most likely to be found in warm (23 to 28°C), low chlorophyll areas with moderate current velocities and favorable regional retention conditions. In the Gulf of Mexico, larvae were located in offshore waters outside of the Loop Current and warm eddies, while in the western Mediterranean, larval occurrences were associated with the confluence of inflowing Atlantic waters and saltier resident surface waters. Although our results suggested common themes within preferred spawning grounds on both sides of the Atlantic Ocean, the ecological processes governing larval survival and eventual recruitment are yet to be fully understood. © Inter-Research 2013. Source


Alvarez A.,Center for Maritime Research and Experimentation | Mourre B.,Balearic Islands Coastal Observing and Forecasting System
Journal of Atmospheric and Oceanic Technology | Year: 2014

The coordinated and cooperative-unaware networking of glider fleets have been proposed to obtain a performance gain in ocean sampling over naïve collective behavior. Whether one of these implementations results in a more efficient sampling of the ocean variability remains an open question. This article aims at a performance evaluation of cooperative-unaware and coordinated networks of gliders to reduce the uncertainty in operational temperature model predictions. The evaluation is based on an observing system simulation experiment (OSSE) implemented in the northern Ligurian Sea (western Mediterranean) from 21 August to 1 September 2010. The OSSE confronts the forecast skills obtained by the Regional Ocean Modeling System (ROMS) when assimilating data gathered from a cooperative and unaware network of three gliders with the prediction skill obtained when data comes from a coordinated configuration. An asynchronous formulation of the ensemble Kalman filter with a 48-h window is used to assimilate simulated temperature observations. Optimum sampling strategies of the glider networks, based on a pattern search optimization algorithm, are computed for each 48-h forecasting period using a covariance integrated in time and in the vertical direction to reduce the dimensionality of the problem and to enable a rapid resolution. Perturbations of the depth-averaged current field in glider motions are neglected. Results indicate a better performance of the coordinated network configuration due to an enhanced capacity to capture an eddy structure that is responsible for the largest forecast error in the experimental domain. © 2014 American Meteorological Society. Source


Mallol S.,Spanish Institute of Oceanography | Mateo-Ramirez A.,University of Malaga | Alemany F.,Spanish Institute of Oceanography | Alvarez-Berastegui D.,Balearic Islands Coastal Observing and Forecasting System | And 3 more authors.
Journal of Crustacean Biology | Year: 2014

The distribution, abundance, and interannual variation of scyllarid phyllosoma larvae were studied in waters of the Balearic Sea (Western Mediterranean) from plankton samples collected between 2001 and 2005. Over the study period, 342 phyllosomas were collected, all belonging to Scyllaridae. Scyllarus arctus (Linnaeus, 1758) was the most abundant (89%), with representation of all developmental stages (I-X), except stage IX, plus two nistos. Scyllarus pygmaeus (Bate, 1888) phyllosoma included middle stages (IV-VII) and two final stages X. Finally, a stage II phyllosoma of Scyllarides latus (Latreille, 1802) was recorded for the first time in the Western Mediterranean. The majority of the phyllosomas were early stage S. arctus found in near shore stations, while advanced stages were common farther away from the coast, especially to the south of the Balearic Sea. That was also the case of S. pygmaeus, most of which stage V, observed to the southwest of the archipelago. Phyllosomas were scarce in low salinity (S < 37.2) water masses of recent Atlantic origin, and interannual differences in distribution reflected the intrusions of low salinity Atlantic water from the South. © Copyright 2014 by The Crustacean Society. Source


Puerta P.,Spanish Institute of Oceanography | Hunsicker M.E.,National Center for Ecological Analysis And Synthesis | Quetglas A.,Spanish Institute of Oceanography | Alvarez-Berastegui D.,Balearic Islands Coastal Observing and Forecasting System | And 3 more authors.
PLoS ONE | Year: 2015

Populations of the same species can experience different responses to the environment throughout their distributional range as a result of spatial and temporal heterogeneity in habitat conditions. This highlights the importance of understanding the processes governing species distribution at local scales. However, research on species distribution often averages environmental covariates across large geographic areas, missing variability in population- environment interactions within geographically distinct regions. We used spatially explicit models to identify interactions between species and environmental, including chlorophyll a (Chla) and sea surface temperature (SST), and trophic (prey density) conditions, along with processes governing the distribution of two cephalopods with contrasting life-histories (octopus and squid) across the western Mediterranean Sea. This approach is relevant for cephalopods, since their population dynamics are especially sensitive to variations in habitat conditions and rarely stable in abundance and location. The regional distributions of the two cephalopod species matched two different trophic pathways present in the western Mediterranean Sea, associated with the Gulf of Lion upwelling and the Ebro river discharges respectively. The effects of the studied environmental and trophic conditions were spatially variant in both species, with usually stronger effects along their distributional boundaries. We identify areas where prey availability limited the abundance of cephalopod populations as well as contrasting effects of temperature in the warmest regions. Despite distributional patterns matching productive areas, a general negative effect of Chla on cephalopod densities suggests that competition pressure is common in the study area. Additionally, results highlight the importance of trophic interactions, beyond other common environmental factors, in shaping the distribution of cephalopod populations. Our study presents a valuable approach for understanding the spatially variant ecology of cephalopod populations, which is important for fisheries and ecosystem management. © 2015 Puerta et al. Source

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