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217 p., Over the past 10 years, Species Distribution Models have become commonplace in the studies of biogeography, conservation biology, ecology, and climate change. However, most studies applying SDMs mainly quantify species-environment relationships and usually omit functional roles of species, biotic interactions and resource-consumer dynamics. Within this context, this thesis aimed to advance in the understanding of how biotic and abiotic factors shape species distribution and abundance by using the community of top predators of the Bay of Biscay as case study. To address this overall objective, we carried out three different studies that aimed to answer the following specific research questions:- To identify the main environmental and biotic drivers of species co-occurrences within the top predators-prey community of the Bay of Biscay. - To understand how co-occurring top predators share the environmental and trophic niche.- To define the role that prey, climatic and oceanographic variables in driving the spatio-temporal patterns of a highly mobile top predator.- To determine the relative importance of biotic and environmental drivers explaining the abundance and distribution of top predators.By this means, this thesis intended to obtain a more comprehensive understanding of the drivers governing the assemblage of top predators and a better knowledge of ecosystem functioning of the BoB.

217 p., Over the past 10 years, Species Distribution Models have become commonplace in the studies of biogeography, conservation biology, ecology, and climate change. However, most studies applying SDMs mainly quantify species-environment relationships and usually omit functional roles of species, biotic interactions and resource-consumer dynamics. Within this context, this thesis aimed to advance in the understanding of how biotic and abiotic factors shape species distribution and abundance by using the community of top predators of the Bay of Biscay as case study. To address this overall objective, we carried out three different studies that aimed to answer the following specific research questions:- To identify the main environmental and biotic drivers of species co-occurrences within the top predators-prey community of the Bay of Biscay. - To understand how co-occurring top predators share the environmental and trophic niche.- To define the role that prey, climatic and oceanographic variables in driving the spatio-temporal patterns of a highly mobile top predator.- To determine the relative importance of biotic and environmental drivers explaining the abundance and distribution of top predators.By this means, this thesis intended to obtain a more comprehensive understanding of the drivers governing the assemblage of top predators and a better knowledge of ecosystem functioning of the BoB.

In habitat modelling, environmental variables are assumed to be proxies of lower trophic levels distribution and by extension, of marine top predator distributions. More proximal variables, such as potential prey fields, could refine relationships between top predator distributions and their environment. In situ data on prey distributions are not available over large spatial scales but, a numerical model, the Spatial Ecosystem And POpulation DYnamics Model (SEAPODYM), provides simulations of the biomass and production of zooplankton and six functional groups of micronekton at the global scale. Here, we explored whether generalised additive models fitted to simulated prey distribution data better predicted deepdiver densities (here beaked whales Ziphiidae and sperm whales Physeter macrocephalus) than models fitted to environmental variables. We assessed whether the combination of environmental and prey distribution data would further improve model fit by comparing their explanatory power. For both taxa, results were suggestive of a preference for habitats associated with topographic features and thermal fronts but also for habitats with an extended euphotic zone and with large prey of the lower mesopelagic layer. For beaked whales, no SEAPODYM variable was selected in the best model that combined the two types of variables, possibly because SEAPODYM does not accurately simulate the organisms on which beaked whales feed on. For sperm whales, the increase model performance was only marginal. SEAPODYM outputs were at best weakly correlated with sightings of deep-diving cetaceans, suggesting SEAPODYM may not accurately predict the prey fields of these taxa. This study was a first investigation and mostly highlighted the importance of the physiographic variables to understand mechanisms that influence the distribution of deep-diving cetaceans. A more systematic use of SEAPODYM could allow to better define the limits of its use and a development of the model that would sim

Effective conservation and management measures are needed to face the unprecedented changes that marine ecosystems, and particularly marine megafauna, are suffering. These measures require the identification of highvalue biodiversity areas (HVBAs) which in turn require the identification of the essential ocean variables (EOVs) that shape the environmental envelope of communities (i.e. space defined by a set of environmental variables). The aim of this study was to delineate and characterise the HVBAs for the north and northwestern Spanish seabird and cetacean community taking advantage of the sightings collected during the annual PELACUS oceanographic survey (2007–2016). We used distance sampling methodology to analyse the species detectability based on environmental conditions. Then, we delimitated the HVBAs and identified the EOVs defining the environmental envelope of the community based on a spatio-temporal modelling approach using Generalized Additive Models. Overall, the main environmental variables driving species abundance were the sea surface temperature (SST), the distance to the shelf-break and the chlorophyll-a concentration (Chl-a). The SST and Chla were identified as dynamic EOVs due to their highest relative predictor importance, driving the environmental envelope and shaping areas of higher density. HVBAs were located mainly over the northwestern Spanish waters and decreased towards the inner Bay of Biscay remaining spatially stable over the study period. By identifying community-level HVBAs, we can understand the underlying ecological and oceanographic processes driving the spatio-temporal patterns of biological communities, such as those composed by seabirds and cetaceans. This information would identify conservation targets to assist the allocation of management resources. In addition, the location of HVBAs can help to fulfil the emergent need for sound spatial information to support the implementation of marine spatial planning.

305 p., Los ecosistemas marinos están amenazados por actividades humanas que afectan su sostenibilidad y capacidad de recuperación, disminuyendo la biodiversidad marina y afectando a su funcionamiento. El objetivo de esta tesis fue evaluar los impactos de las actividades antropogénicas sobre la megafauna marina mediante la integración de su ecología espacial en el enfoque ecosistémico. Centrada en las aves marinas y los cetáceos que habitan en el Golfo de Vizcaya (GdV), esta tesis desarrolla un marco ecológico integrador basado en enfoques multidisciplinares para identificar amenazas, desarrollar indicadores ambientales, establecer valores de referencia, obtener estimas de abundancia espacio-temporal, evaluar la coherencia de la red de Áreas Marinas Protegidas (AMPs) y examinar el valor de las series temporales de datos para la designación robusta de AMPs. Así, el Cap. 1 evalúa el impacto de las amenazas sobre la megafauna del GdV; el Cap. 2 desarrolla un enfoque metodológico integrador para avanzar en el monitoreo a nivel ecosistémico; el Cap. 3 identifica variables esenciales oceánicas y áreas de alto valor de biodiversidad para la comunidad de megafauna de la costa norte y noroeste peninsular; el Cap. 4 aborda la dificultad de proteger especies altamente moviles localizando sus áreas críticas y la protección que ofrece para éstas la actual red de AMPs del GdV; y el Cap. 5 evalúa el valor de las series temporales de datos explorando si las áreas prioritarias para la conservación de la megafauna son consistentes, independientemente del período de tiempo considerado en el proceso de priorización.

Aim During their migration, highly mobile species cross multiple jurisdictional boundaries and multiple not‐specic marine protected areas (MPAs). When identifying the critical habitats where individuals aggregate, these areas can be ideal candidates for MPAs. This study was focused on the endangered n whale (Balaenoptera physalus) for which there is little knowledge on its distribution and abundance in non‐breeding temperate latitudes. Location Bay of Biscay (BoB). Methods Firstly, we modelled the relative abundance of n whales by means of generalized additive models (GAMs) using data collected on the PELACUS (2007–2008) and JUVENA (2013–2016) oceanographic surveys during late summer. Secondly, we evaluated the reliability of the predictions by distinguishing environmental extrapolations and interpolations. Finally, we identied critical areas of highest predicted abundance and we assessed whether existing MPAs comprised within the Natura 2000 network and designated for other species oer protection to n whales in the BoB Results Fin whales were especially abundant in deep o‐shore waters, mainly associated with intermediate temperature water values in the inner part of the BoB. The years with the highest relative predicted abundances (an average of 1,500 whales) matched with years when warmer sea surface temperature extended into larger areas. In colder years, the average predicted abundance dropped to 400 whales. The main critical area for n whales (dened by the highest 40% of abundance) was common for both surveys, and it was located in the south‐eastern part of the BoB. Main conclusions Our study contributes to the identication of important concentration areas of n whales during late summer, based on reliable spatial predictions. The assessment of the current Natura 2000 network highlights the fact that only three MPAs marginally covered the critical area we have identied for n whales. We propose a transboundary potential MPA to aid the conservation of the species

The marine environment faces an increasing number of threats, mainly driven by anthropogenic activities, that are causing growing impacts on marine species and processes. In Europe, the EU Marine Strategy Framework Directive (MSFD) aims to achieve or maintain Good Environmental Status (GES) of the European waters by 2020. The Directive specifically refers to biodiversity with the first of the eleven qualitative descriptors (proposed to help describe what GES should look like) being Biodiversity is maintained. For this descriptor, the status of several functional groups, including marine megafauna species, need to be assessed using criteria such as population size and condition, and mortality due to bycatch in fishing gear, that compare current values against agreed thresholds. To contribute to this process, we performed an assessment of the threats affecting the marine megafauna community (i.e. seabirds and cetaceans) in the Bay of Biscay synthesizing the available evidences and identifying the main threats affecting the marine megafauna to help prioritise the required management and conservation actions. We analysed 4,023 admissions of seabirds recorded during 2004–2016 from four Wildlife Rehabilitation Centres to obtain an initial quantitative assessment of the pressures exerted on seabirds. The main marine threats identified in the Spanish North Atlantic sub-region were cachexia (52.3%), exposure to crude oil (10%) and interaction with fishing gears (5.3%). When considering all threats together, the common guillemot, the yellow-legged gull, the northern gannet, the great cormorant and the razorbill were the main affected species. In addition, we summarised the available information to perform an updated qualitative assessment of the severity of the threats faced by seabirds and cetaceans. The qualitative assessment showed that cetaceans are especially vulnerable to bycatch, vessel collision, and pollution-related threats, whilst seabirds are particularly sensitiv

In the last few decades, there has been a remarkable development of niche models to help understand the ecological response of species to current rapid environmental changes. In the present study, we applied niche modelling to the megafauna community of shelf waters of the northwestern (NW) and northern Iberian Peninsula in order to analyse the coexistence of different species taking into consideration their niche preferences. The Spanish Institute of Oceanography conducts the PELACUS multidisciplinary survey annually to assess pelagic fish stocks and collect information on the status of other ecosystem components, such as oceanographic conditions, phytoplankton, zooplankton and marine megafauna. Using data collected from these surveys, we developed niche models for 14 marine megafauna taxa (3 cetaceans, 10 seabirds and 1 fish) incorporating multi-trophic ecological descriptors collected simultaneously during the surveys alongside the more commonly used oceanographic variables (e.g. chlorophyll a and sea surface temperature). Megafauna niche models were developed by pooling observations from 2007 to 2013 and were found to be driven by mean fish biomass and its variability, in addition to sea surface temperature. Hierarchical clustering identified four distinct megafauna assemblages, the first comprising wide-ranging species and the other three associated with shelf-slope waters in Galicia, coastal/shelf waters in Galicia, and the eastern Cantabrian Sea, respectively. Community-level hotspot areas were found in shelf and shelf-break sectors of Galicia, along with small diversity spots scattered throughout the Cantabrian coastal area. Our results showed that synoptically collected survey-based ecological descriptors, especially acoustic-based preyscapes, were among the most important variables explaining megafauna niche preference. These findings highlight the advantage of using integrated ecosystem surveys to collect simultaneous information on a suite of ecosystem c

1. Distribution maps of cetaceans and seabirds at basin and monthly scales are needed for conservation and marine management. These are usually created from standardized and systematic aerial and vessel surveys, with recorded animal den- sities interpolated across study areas. However, distribution maps at basin and monthly scales have previously not been possible because individual surveys have restricted spatial and temporal coverage. 2. This study develops an alternative approach consisting of: (a) collating diverse survey data to maximize spatial and temporal coverage, (b) using detection func- tions to estimate variation in the surface area covered (km2) among these surveys, standardizing measurements of effort and animal densities, and (c) developing species distribution models (SDM) that overcome issues with heterogeneous and uneven coverage. 3. 2.68 million km of survey data in the North-East Atlantic between 1980 and 2018 were collated and standardized. SDM using Generalized Linear Models and General Estimating Equations in a hurdle approach were developed. Distribution maps were then created for 12 cetacean and 12 seabird species at 10 km and monthly resolution. Qualitative and quantitative assessment indicated good model performance. 4. Synthesis and applications. This study provides the largest ever collation and standardization of diverse survey data for cetaceans and seabirds, and the most comprehensive distribution maps of these taxa in the North-East Atlantic. These distribution maps have numerous applications including the identification of im- portant areas needing protection, and the quantification of overlap between vul- nerable species and anthropogenic activities. This study demonstrates how the analysis of existing and diverse survey data can meet conservation and marine management needs.

Aim Deep-diving cetaceans are oceanic species exposed to multiple anthropogenic pressures including high intensity underwater noise, and knowledge of their distribution is crucial to manage their conservation. Due to intrinsic low densities, wide distribution ranges and limited presence at the sea surface, these species are rarely sighted. Pooling data from multiple visual surveys sharing a common line-transect methodology can increase sightings but requires accounting for heterogeneity in protocols and platforms. Location North Atlantic Ocean and Mediterranean Sea. Time period 1998 to 2015. Major taxa Ziphiidae; Physeteriidae; Kogiidae. Methods About 1,240,000 km of pooled effort provided 630 sightings of ziphiids, 836 of physeteriids and 106 of kogiids. For each taxon, we built a hierarchical model to estimate the effective strip width depending on observation conditions and survey types. We then modelled relative densities in a generalized additive modelling framework. Geographical predictions were limited to interpolations identified with a gap analysis of environmental space coverage. Results Deeper areas of the North Atlantic gyre were mostly environmental extrapolation in the predictions, thereby highlighting gaps in sampling across the different surveys. For the three species groups, the highest relative densities were predicted along continental slopes, particularly in the western North Atlantic Ocean where the Gulf Stream creates dynamic frontal zones and eddies. Main conclusions Pooling a large number of surveys provided the first basin-wide models of distribution for deep-diving cetaceans, including several data-deficient taxa, across the North Atlantic Ocean and the Mediterranean Sea. These models can help the conservation of elusive and poorly known marine megafauna.

Monitoring and assessment of the status of marine mammal populations is a requirement of the European Marine Strategy Framework Directive (MSFD). Due to the difficulty of collecting data in the marine environment and because many populations of these highly mobile species inhabit waters of several Member States, monitoring of marine mammals is particularly challenging. In the present work we have used a 10- year time-series of data collected from multidisciplinary research surveys to estimate common dolphin (Delphinus delphis) abundance and trends in continental shelf waters of the northwest Spanish sub-region. We argue that this approach provides a valuable addition to large-scale dedicated surveys, offering a shorter interval between surveys and hence offering the possibility to track abundance changes at a regional scale. Trends in the number of dolphins present in the study area over the last 10 years show a mean increase of about 9.6% per year, which results in an evaluation of Good Environmental Status for the species in the area using the abundance indicator adopted in the framework of the MSFD. Data obtained from dedicated dual-platform surveys have been used to correct the detection bias in our data collected using single-platforms (attraction toward the observation platform and animals missed on the track-line), to obtain absolute abundance estimates for calculating bycatch limits. The average abundance over the study period was 12831 dolphins [CI 95%; 9025, 18242] calculated with the conventional distance sampling methodology, 4747 [3307, 6816] corrected for attraction and missed animals on the track-line, and 22510 [15776, 32120] corrected only for missed animals on the track-line. The estimated safe bycatch limit for this area calculated from these abundance values were 218 [153, 310], 81 [56, 115] and 383 [268, 546] per year, respectively. Comparing these figures with estimates based on different sources, the percentage of dolphins that die in this stu

Con el fin de identificar áreas ecológicamente significativas, necesitamos relacionar la distribución de especies con descriptores ecológicos que nos ayuden a comprender su distribución. En el medio marino, los modelos de distribución de especies (MDE) han sido tradicionalmente desarrollado en base a descriptores ecológicos indirectos (como clorofila y temperatura superficial del mar) recogidos a través de imágenes de satélite. Aunque las especies marinas pueden utilizar estas señales ambientales para localizar sus presas, el uso de información sobre la distribución de las mismas sería más informativo que el uso de estos descriptores indirectos. Gracias a las campañas oceanográficas multidisciplinares se puede recoger información simultánea de varios niveles tróficos, desde el plancton a los depredadores marinos, incluyendo sus principales presas pelágicas: los pequeños peces pelágicos. Por lo tanto, la inclusión de esta información en los MDE debería ser más relevante que las variables oceanográficas indirectas. Para testar esta hipótesis, desarrollamos MDE para las tres especies más abundantes de cetáceos que se registran en el norte de la Península Ibérica durante las campañas de primavera del Instituto Español de Oceanografía, PELACUS (2007-2013). Estas especies fueron el delfín común Delphinus delphis, el delfín mular Tursiops truncatus y el calderón común Globicephala melas. Dependiendo de las especies consideradas, se identificaron diferentes variables ambientales como importantes a la hora de explicar los patrones de distribución; pero las cifras globales ponen de manifiesto la principal contribución de la batimetría, seguido de la temperatura superficial del mar y la variabilidad espacial en la distribución de los pequeños peces pelágicos. Estos resultados tienen importantes implicaciones en reconocer la importancia de los estudios oceanográficos multidisciplinares para la obtención de descriptores ecológicos directos para mejorar los modelos de distribució

The Spanish acoustic-trawl times PELACUS 0314 was carried out on board R/V Miguel Oliver from 9th March to 8th April, covering the north Spanish waters (Atlantic and Bay of Biscay) from the coast to the 1000 m isobath on a systematic grid with tracks 8 nmi apart and equally spaced. Acoustic , fishing stations, fish egg counting, microplastic, and apical predators observations were done during daytime whilst the oceanographic characterisation was done during night time. A total of 1903 nautical miles were steamed, 1075 corresponding to the survey track. Besides 52 fishing stations were performed (Figure 2). PELCACUS 0314 was characterised by relative stable weather conditions along the surveyed area. Besides, there was an important increase in backscattering energy as compared with the previous year. This resulted in an increase of the biomass estimated for the majority of the fish species, but still sardine is at lowest productivity ever recorded. Good recruitment would be observed in horse mackerel, but for the rest of the fish species, no strong signals for age group 1 have been detected. The reasons for this increase would be related to the weather stability which could have increased the fish availability either for a change in the behaviour (i.e. spatial pattern distribution) or for an increase in the food availability. This is relevant accounting the increase of the occurrence of mackerel subsurface layers observed this year. As PELACUS is a multidisciplinary survey series (we collect environmental and biological ancillary information, stomach contents, including CTD cats, plankton tows or continuous records of plankton, eggs, S, T and flourometry), we will try to explain this change of behaviour. Our main hypothesis is that these species could follow mackerel when is undertaking vertical migration, probably related with the spawning activity, just for feeding eggs and, therefore, changing the expected schooling behaviour by the dispersed one, used during the

El objetivo de las Estrategias Marinas es permitir el uso sostenible del medio marino mediante la gestión de las actividades y presiones humanas siguiendo un enfoque ecosistémico. La evaluación del estado de conservación de las especies marinas y su monitorización para determinar si alcanza el Buen Estado Ambiental (BEA) son sus pilares básicos. Para establecer medidas de gestión que permitan a una población alcanzar el BEA, se debe estudiar el estado de la misma y el efecto que diferentes niveles de amenazas antropogénicas pueden tener sobre ella. La creación de modelos dinámicos permite estudiar las posibles trayectorias de una población ante diferentes escenarios. La fuente de información biológica más importante que poseemos es aquella proveniente de los varamientos, que también proporcionan información sobre la causa de la muerte. El análisis de las muestras de individuos varados nos permite calcular tasas de natalidad, mortalidad, estructura de edad poblacional y el impacto directo o indirecto de las presiones antropogénicas (captura accidental, colisiones con embarcaciones, contaminación, etc.). Asimismo, los patrones observados en los varamientos nos dan información sobre la tendencia en la abundancia de una especie y sobre posibles desplazamientos. La abundancia de una población puede ser obtenida mediante campañas de avistamiento y, dependiendo de la metodología empleada, pueden obtenerse estimas relativas o absolutas. Además, la dieta de los cetáceos nos permite estudiar sus preferencias alimentarias y el papel que pueden estar jugando en el ecosistema. Los modelos multiespecíficos (p.ej. Gadget) posibilitan estudiar su interacción con los stocks pesqueros e informar una gestión ecosistémica. En este trabajo se presentan datos preliminares sobre abundancia del delfín común en el N y NW peninsular, tendencias en la abundancia, parámetros biológicos y su estructura poblacional, mortalidad natural, pesquera y ejemplos de puntos de referencia que permitan det

Common dolphin s ( Delphinus delphis ) are one of the most abundant species of small cetacean in Northeast Atlantic Ocean and the most abundant in Atlantic shelf waters of the Iberian Peninsula. However, the abundance , distribution and population trends in the recen t years of this species are poorly known , but such information is needed to develop population dynamic models . Thus far, the only absolute abundance estimate in the shelf Atlantic waters of the Iberian Peninsula was obtained in 2005 during the SCANS - II survey. Along the north and northwest coast s of the Iberian Peninsula , t he Spanish Institute of Oceanography has carried out annual acoustic survey s to estimate pelagic fish biomass for the last two decades. Since 2007 , an observer program for top predators has been integrated in to these survey s , collecting sightings on cetaceans, seabirds and other species using line - transect method ology . Common d olphin sightings from 2007 to 201 4 were analyzed with Distance software to estimate relative population size . Because attraction to the vessel could inflate population estimates, c ommon dolphin a bundance was estimated using a detection function only from sightings where no attraction were recorded and also using Bayesian methods to combine previou s data on attraction collected during SCANS - II with data collected from the acoustic fish surveys. D olphin density estimated with both methods w as < 0.3 dolphin s/ Km 2 , which is similar to the density estimated by SCANS - II . T he Bayesian framework allows us to work with the scarcity and uncertainty of the data , particularly when obtaining annual estimates. Because c etacean sightings were collected during fish acoustic surveys , pelagic fish abundance ( e.g. S ardine and Blue whiting ) , obtained concurrently to the sightings, can be used , along with other environmental variables , to model dolphin habitat and to predict dolphin abundance and distribution.

The European Union has adopted the Marine Strategy Framework Directive (MSFD, Directive 2008/56/EC) with the objective of achieving or maintaining Good Environmental Status (GES) of European waters by 2020. The MSFD constitutes the legislative instrument devised to protect the marine environment across European waters from the human-­‐related environmental changes that had already negatively affected marine ecosystem functioning and the dynamics of many populations of marine organisms. To achieve GES, Member States will need to address all human activities that have an impact on the marine environment, through an integrated ecosystem-­‐based approach that is spatially explicit. Multidisciplinay surveys are an ideal platform that can provide a synoptic view of the status of marine habitats. PELACUS surveys are conducted annually for acoustic assessment and mapping of the oceanographic and biological conditions of the northern and northwestern shelf of the Iberian Peninsula. The main objective is to monitor the pelagic ecosystem collecting concurrent information on several trophic levels. Since 2007, marine mammal and seabirds sightings have been recorded by dedicated observers, who also collect information on the type and abundance of different types of human pressures (e.g. fishing, marine debris). Using distance sampling methodology, we were able to estimate relative abundance of marine predator species in the region in addition to mapping the areas where they could be more at risk from anthropogenic pressures such as fishing and marine litter. Our objective is to highlight the importance of observer programmes not only in providing (1) baseline information on distribution and abundance of top predators, but (2) also additional information on human pressures. Both types of data are needed to inform any conservation and management plans such as the MSFD.

Phytoplankton biomass dynamic integrates information about the characteristics of the pelagic ecosystem. Temporal and spatial patterns respond to physical processes. Also, phytoplankton abundance and its temporal dynamic largely determine the structure and dynamics of the food web. The southern European Atlantic (48 ºN – 36 ºS) presents differences in continental margin orientation, upwelling intensity, river runoff, a semi-enclosed oceanic domain (Bay of Biscay), and open oceanic waters to the west. Sea surface chlorophyll concentration (SSChl) monthly averages (from satellites) from 1998 to 2012 were analysed at 4x4 km resolution by Empirical Orthogonal Functions. The study area was regionalized according to rotated EOFs and temporal modes were used to resume the SSChl temporal variability in each region. The environmental forcing of temporal modes was analysed against environmental variables by means of Canonical Correspondence Analysis. More than 50% of the variability in oceanic regions was captured by the seasonal signal, with differences in the timing of the spring bloom and with the shape of the seasonal signal related with the latitudinal gradient and the ‘stagnation effect’ of the Bay of Biscay. In French and western Iberian shelves seasonality represented < 20% variability, whereas the Cantabrian shelf presented an intermediate level. Considering spatial patterns, the % of explained variability increased <5% in oceanic waters, whereas in the Western Iberian and French shelves it accounted >50%. The difference between shelf and oceanic regions was due to mesoscale processes in shelf areas; i.e. river runoff in the French shelf and coastal upwelling in the western Iberian shelf. Shelf mesoscale processes impose short frequency variability on to the seasonal cycle and increase SSChl levels. The influence that these patterns of spatial and temporal dynamics have on the structure and dynamics of the rest of the food web can be perceived on the spatial patterns

This study demonstrates the utility of trawl data, collected during acoustic surveys of pelagic fish stocks as a way of confirming fish identification, to characterize the pelagic community, as well as allowing description and prediction of fish distribution patterns, based on data from Spanish Atlantic Ocean shelf surveys during spring 2005–2011. The composition of the pelagic community is described, as well as spatial and temporal patterns of variation in both the community composition and the presence and importance of two of the main exploited pelagic species, sardine Sardina pilchardus and anchovy Engraulis encrasicolus. The most important species in terms of both frequency of occurrence and standardized mass in hauls were mackerel Scomber scombrus, hake Merluccius merluccius, horse mackerel Trachurus trachurus, S. pilchardus and bogue Boops boops. Multivariate analysis indicated significant effects of depth, geographical area and year on haul composition. Descriptive generalized additive models (GAM), with latitude, longitude and depth as predictors, identified clear spatial patterns in the occurrence and abundance of both S. pilchardus and E. encrasicolus, with abundance being highest closer to the coast and, in the case of E. encrasicolus, higher near the French and Portuguese borders. Further GAM analysis, using environmental variables to explain spatial patterns, revealed significant effects of depth and sea surface temperature (SST) gradient and depth on S. pilchardus importance, while E. encrasicolus importance was related to SST. The importance of both species in hauls was higher in the years of higher spawning stock biomass (SSB) and E. encrasicolus also appeared to expand its range when SSB was higher.

Shifts in the diet of top predators can be linked to changes in environmental conditions. In this study, we tested relationships between environmental variation and seasonal changes in diet of a top predator, the grey-headed albatross Thalassarche chrysostoma, breeding at Bird Island, South Georgia in an austral summer of 1999/2000. Oceanographic conditions in that year around South Georgia were abnormal (i.e. anomalously high sea surface temperature to a relative 19-year long-term mean). The diet of grey-headed albatrosses showed high seasonal variation, shifting from cephalopods (42.9 % by mass) in late February to Antarctic krill Euphausia superba (58.3 %) in late April, and grey-headed albatrosses breeding performance was low (16.8 %). This study shows these albatrosses did not manage to find sufficient alternative prey and highlight the risk to top predators if there is an increase in the frequency or severity of food shortages in Antarctic waters.

Knowledge about the spatial distribution of seabirds at sea is important for conservation. During marine conservation planning, logistical constraints preclude seabird surveys covering the complete area of interest and spatial distribution of seabirds is frequently inferred from predictive statistical models. Increasingly complex models are available to relate the distribution and abundance of pelagic seabirds to environmental variables, but a comparison of their usefulness for delineating protected areas for seabirds is lacking. Here we compare the performance of five modelling techniques (generalised linear models, generalised additive models, Random Forest, boosted regression trees, and maximum entropy) to predict the distribution of Balearic Shearwaters (Puffinus mauretanicus) along the coast of the western Iberian Peninsula. We used ship transect data from 2004 to 2009 and 13 environmental variables to predict occurrence and density, and evaluated predictive performance of all models using spatially segregated test data. Predicted distribution varied among the different models, although predictive performance varied little. An ensemble prediction that combined results from all five techniques was robust and confirmed the existence of marine important bird areas for Balearic Shearwaters in Portugal and Spain. Our predictions suggested additional areas that would be of high priority for conservation and could be proposed as protected areas. Abundance data were extremely difficult to predict, and none of five modelling techniques provided a reliable prediction of spatial patterns. We advocate the use of ensemble modelling that combines the output of several methods to predict the spatial distribution of seabirds, and use these predictions to target separate surveys assessing the abundance of seabirds in areas of regular use.