Biologia de la conservació d'un ocell críticament amenaçat: la baldritja Puffinus mauretanicus

Biologia de la conservació d’un ocell críticament amenaçat: la baldritja Puffinus mauretanicus. Una de les aus marines més amenaçades de la Mediterrània és la baldritja Puffinus mauretanicus. El present article resumeix l’estudi de la seva problemàtica de conservació al dos hàbitats que ocupen: les colònies de cria a terra i les zones d’alimentació a la mar. Una anàlisi demogràfic detallat va permetre determinar que la mortalitat adulta és la principal causa del declivi poblacional. La baixa supervivència adulta (0.78, SE = 0.02) en colònies lliures de depredadors suggeria que, a part de la depredació, devia haver altres fonts de mortalitat (arts de pesca, per exemple). L’anàlisi de viabilitat de la població va mostrar que les probabilitats d’extinció de la baldritja són extremadament altes, classificant a l’espècie en Perill Crític, segons criteris de la IUCN. En relació a la seva distribució a la mar, a rel d’una anàlisi de l’hàbitat oceanogràfic d’aquesta espècie durant l’època reproductora es va proposar la delimitació d’una àrea marina protegida. Així, les àrees d’alta densitat (principalment zones d’alimentació) definirien el nucli, d’especial interès per a la seva conservació, on s’implementarien mesures de protecció rigoroses: l’àrea d’influència del riu Ebre i l’entorn del cap de la Nau. Dins l’àrea de distribució (aigües costaneres de la plataforma continental Ibèrica caracteritzades per sistemes frontals en àrees properes a les colònies de cria), s’implementarien altres mesures de protecció més difuses.Conservation biology of a critically threatened bird: the Balearic shearwater Puffinus mauretanicus. The Balearic shearwater Puffinus mauretanicus is one of the most threatened seabirds in the Mediterranean. This article summarises the conservation problems in the two habitats they occupy: the breeding colonies on land and the feeding areas at sea. A detailed demographic analysis indicates that adult mortality is the principal cause of population decline. The low adult survival rate (0.78, SE = 0.02) in colonies free of predators suggests that, in addition to predation, there must be other sources of mortality (fishing gears, for example). The analysis of population viability shows that the probability of extinction for the Balearic shearwater is extremely high, classifying the species as Critically Endangered according to the criteria of the IUCN. With regard to its distribution at sea, by means of an analysis of the oceanographic habitat of this species during the breeding season, a marine protected area can be proposed. The areas of high density (mainly feeding zones) would determine the core, of special conservation interest for the species, where strict protection measures would be implemented: the area of influence of the Ebro river and the sea around the cap de la Nao. Elsewhere within the foraging range of the species (coastal waters of the Iberian continental platform characterised by frontal systems in areas close to breeding colonies), more diffuse protection measures could be applied

Spatial and temporal patterns of sea surface chlorophyll concentration and environmental forcing in the southern European Atlantic

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 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 of fisheries catches

Resultados preliminares sobre el hábitat de alimentación de la Pardela balear en el Levante ibérico peninsular

Resultados preliminares sobre el hábitat de alimentación de la Pardela Balear en el Levante Ibérico Peninsular. Las aves marinas son susceptibles a una variedad de impactos antropogénicos, incluyendo la ingestión de plásticos, vertidos de petróleo, competencia con la pesca y la captura incidental. Conocer su distribución en el mar puede ayudar a los gestores a evaluar la susceptibilidad de diferentes especies y poblaciones a amenazas específicas. Se caracterizó la distribución en el mar de la pardela balear Puffinus mauretanicus, una especie críticamente amenazada endémica de las Islas Baleares, a lo largo de la costa mediterránea de la península Ibérica durante tres años coincidiendo con el período de crecimiento del pollo (mayo-junio). La especie habitó principalmente la plataforma continental asociándose a frentes, en los que puede llegar a concentrarse una gran abundancia de presas, en torno a las aguas delta del Ebro.Preliminary results of the foraging habitat of the Balearic Shearwater off the eastern Iberian peninsula. Seabirds are susceptible to a variety of anthropogenic impacts, including plastic ingestion, oil spills, competition with fisheries, and bycatch. Understanding their distribution at sea can help managers to assess the susceptibility of different species and populations to specific threats. We characterized the at-sea distribution of the Balearic Shearwater, Puffinus mauretanicus, a critically endangered species endemic to the Balearic Islands, along the Mediterranean coast of the Iberian Peninsula during three years coinciding with the chick-rearing period (May-June). The species mostly inhabited the productive continental shelf and associated with fronts where high prey concentrations could occur around the Ebro Delta area

Essential ocean variables and high value biodiversity areas: Targets for the conservation of marine megafauna

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.En prens

Identifying main interactions in marine predator-prey networks of the Bay of Biscay

Identifying the role that environmental factors and biotic interactions play in species distribution can be essential to better understand and predict how ecosystems will respond to changing environmental conditions. This study aimed at disentangling the assemblage of the pelagic predator–prey community by identifying interspecific associations and their main drivers. For this purpose, we applied the joint species distribution modelling approach, JSDM, to the co-occurrence patterns of both prey and top predator communities obtained from JUVENA surveys during 2013–2016 in the Bay of Biscay. Results showed that the co-occurrence patterns of top predators and prey were driven by a combination of environmental and biotic factors, which highlighted the importance of considering both components to fully understand the community structure. In addition, results also revealed that many biotic interactions, such as schooling in prey (e.g. anchovy–sardine), local enhancement/facilitation in predators (e.g. Cory’s shearwater–fin whale), and predation between predator–prey species (e.g. northern gannet–horse mackerel), were led by positive associations, although predator avoidance behaviour was also suggested between negatively associated species (e.g. striped dolphin–blue whiting). The identification of interspecific associations can therefore provide insights on the functioning of predators–prey network and help advance towards an ecosystem-based managementThis research was funded by the Basque Government (Department of Agriculture, Fishing, and Food Policy) and the Spanish Ministry of Economy, Industry, and Competitiveness through the CHALLENGES project (CTM2013-47032-R). A. Astarloa has benefited from a Basque Government scholarship (PRE_2016_1_0134) and M. Louzao was funded by the Ramo´n y Cajal (RYC-2012-09897) researcher programme of the Spanish Ministry of Economy, Industry, and Competitiveness. JUVENA survey series was sponsored since 2003 by the “Viceconsejerı´a de Agricultura, Pesca y Polı´ticas Alimentarias—Departamento de Desarrollo Econo´mico y Competitividad” of the Basque Government and the “Secretarı´a General de Pesca, Ministerio de Agricultura, Alimentacio´ n y Medio Ambiente” of the Spanish Government

Assessing the Environmental Status of the short-beaked common dolphin (Delphinus delphis) in North-western Spanish waters using abundance trends and safe removal limits

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 study area is higher than the maximum limit allowable under the OSPAR criteria for population mortality adopted as an indicator for the MSFD.Versión del editor3,26

Influence of seasonal variability on the trophic structure of pelagic communities

Seasonal variations in hydrodynamic conditions play a critical role in prey availability at the base of the food web and thus have implications for trophic interactions at higher trophic levels. Here we use the combination of stomach content analysis (SCA) and stable isotope analysis (SIA) to investigate predator-prey interactions and trophic structure of the pelagic fish community of the Bay of Biscay (BoB) in spring and late summer of 2020 and 2021. We found that trophic guilds were more influenced by intra-specific affinities rather than seasonal variability. Main prey for the pelagic fish comprised a set of species belonging to different trophic positions (TPs), from low TP class Thaliacea (salps) to mid TP Engraulis encrasicolus. Vertically migrating meso- and macrozooplankton (mainly copepods and krill) also played an important role as food source for the pelagic fish community showing high trophic overlap among most of species. No differences were detected between the trophic structure in spring and late summer with fish, squids and chaetognaths at the top TPs, whereas krill, meso-zooplankton and salps had the lowest values. However, the TPs estimated using both SCA and SIA approaches were consistently lower in spring, likely due to higher densities and, thus, low TP prey availability in spring. When analyzing ontogenic changes in TPs with predator’s size, significant and positive relationships were found when TP was estimated using SIA but not when using SCA. Overall, our results reveal new insights into the seasonal trophic dynamics of the pelagic fish community of the BoB

Abundance and distribution of the common dolphin (Delphinus delphis) in the north of the Iberian Peninsula

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

Deep ocean drivers better explain habitat preferences of sperm whales Physeter macrocephalus than beaked whales in the Bay of Biscay

Species Distribution Models are commonly used with surface dynamic environmental variables as proxies for prey distribution to characterise marine top predator habitats. For oceanic species that spend lot of time at depth, surface variables might not be relevant to predict deep-dwelling prey distributions. We hypothesised that descriptors of deep-water layers would better predict the deep-diving cetacean distributions than surface variables. We combined static variables and dynamic variables integrated over different depth classes of the water column into Generalised Additive Models to predict the distribution of sperm whales Physeter macrocephalus and beaked whales Ziphiidae in the Bay of Biscay, eastern North Atlantic. We identified which variables best predicted their distribution. Although the highest densities of both taxa were predicted near the continental slope and canyons, the most important variables for beaked whales appeared to be static variables and surface to subsurface dynamic variables, while for sperm whales only surface and deep-water variables were selected. This could suggest differences in foraging strategies and in the prey targeted between the two taxa. Increasing the use of variables describing the deep-water layers would provide a better understanding of the oceanic species distribution and better assist in the planning of human activities in these habitats.Versión del edito