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71 pages, 33 figures, 18 tables, 4 appendixes.-- Acceso al código y a los datos: El repositorio de GitHub SDM-GSA06-MEDITS-VMS (Julià et al. 2023) contiene el script de R utilizado en el análisis espacial de este informe y los mapas con las predicciones obtenidas, Los pequeños peces pelágicos del Mediterráneo noroccidental constituyen unos elementos clave de los ecosistemas marinos, representan una fracción mayoritaria de las capturas pesqueras, y sirven como principal fuente de alimento de un elevado número de especies, entre las que destacan las aves marinas (Coll et al. 2015, Coll & Bellido 2020, Ouled-Cheikh et al. 2022). Debido a la influencia de diferentes ríos, entre los que destaca el río Ebro, esta zona es también una de las más importantes de todo el Mar Mediterráneo en términos de productividad y biomasa de pequeños peces pelágicos. Entre las especies de peces pelágicos más abundantes destacan la anchoa (Engraulis encrasicolus), la sardina (Sardina pilchardus) y la alacha (Sardinella aurita) (Coll & Bellido 2020). [...], With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Fisheries provide an abundant and predictable food source for many pelagic seabirds through discards, but also pose a major threat to them through bycatch, threatening their populations worldwide. The reform of the European Common Fisheries Policy (CFP), which intends to ban discards through the landing obligation of all catches, may force seabirds to seek alternative food sources, such as baited hooks from longlines, increasing bycatch rates. To test this hypothesis we performed a combined analysis of seabird-fishery interactions using as a model Scopoli's shearwaters Calonectris diomedea in the Mediterranean. Tracking data showed that the probability of shearwaters attending longliners increased exponentially with a decreasing density of trawlers. On-board observations and mortality events corroborated this result: the probability of birds attending longliners increased 4% per each trawler leaving the longliner proximity and bird mortality increased tenfold when trawlers were not operating. Therefore, the implementation of the landing obligation in EU waters will likely cause a substantial increase in bycatch rates in longliners, at least in the short-term, due to birds switching from trawlers to longliners. Thus the implementation of the landing obligation must be carefully monitored and counterbalanced with an urgent implementation of bycatch mitigation measures in the longline fleet.

Some seabird species have learnt to efficiently exploit fishing discards from trawling activities. However, a discard ban has been proposed as necessary in Europe to ensure the sustainability of the seas. It is of crucial importance for the management and conservation purposes to study the potential consequences of a discard ban on the foraging ecology of threatened seabirds. We assessed the influence of fishing activities on the feeding habits of 22 male and 15 female Audouin's gulls ( Larus audouinii ) from the Ebro Delta (Mediterranean Sea) during the breeding period using GPS loggers together with Stable Isotope Analysis (SIA), which provided new insights into their foraging behavior and trophic ecology, respectively. GPS data revealed different sex-specific foraging patterns between workdays and weekends. Females were highly consistent in that they foraged at sea throughout the week even though discarding stops at weekends. In contrast, males switched from foraging at sea during the week (when discards are produced) to an increased use of rice field habitats at week- ends (when fishermen do not work). This sex-specific foraging behavior could be related to specific nutritional requirements associated with previous egg pro- duction, an energetically demanding period for females. However, on a broader time scale integrated by the SIA, both sexes showed a high degree of individual specialization in their trophic ecology. The need to obtain detailed information on the dependence and response of seabirds to fishing activities is crucial in conservation sciences. In this regard, sex-specific foraging behavior in relation to fisheries has been overlooked, despite the ecological and conservation impli- cations. For instance, this situation may lead to sex differentiation in bycatch mortality in longlines when trawlers do not operate. Moreover, any new fisher- ies policy will need to be implemented gradually to facilitate the adaptation of a specialized species to a discard ban scenario.

Comunicación presentada en el 13th Medmaravis Pan-Mediterranean Symposium, celebrado del 13 al 17 de octubre de 2011 en Alguer, Cerdeña (Italia), Comunicación publicada en: Yésou, Pierre; Baccetti, Nicola; Sultana, Joe (eds.). Ecology and Conservation of Mediterranean Seabirds and other bird speciesunder the Barcelona Convention : update & progress : Proceedings of the 13th Medmaravis Pan-Mediterranean Symposium. Alghero: Medmaravis, 2012, p.84-94. ISBN 978-99957-0-344-8, The boat-based counts were conducted by SEO/BirdLife within the frame of Project LIFE04NAT/ES/000049 (Marine IBAs in Spain; 2004-2009), and also received support from the BirdLife Preventing Extinctions Programme-Species Guardians (Balearic Shearwater)

A partir de censos estandarditzats i no estandarditzats, es van obtenir una sèrie d’evidències de reproducció que han permès elaborar un atles de distribució de l’espècie a Catalunya a una resolució de 1x1 km. A més, a partir de les observacions estandarditzades i de diverses variables ambientals i poblacionals, s’han pogut desenvolupar models d’adequació de l’hàbitat a una resolució de 20 m mitjançant el software MAXENT. En total s’han obtingut quaranta-tres quadrats amb alguna evidència de reproducció, dels quals trenta-set es troben en el principal nucli reproductor de l’espècie a Catalunya (Secà d’Alfés-Castelldans). Aquí es troben els dotze quadrats amb evidències de reproducció segura identificades, les quals mostren una marcada continuïtat espacial. Els models d’adequació de l’hàbitat mostren un gran solapament amb els quadrats amb major concentració d’evidències de cria i mostren com l’espècie utilitza de manera exclusiva mosaics extensius de secà, bàsicament zones planes, amb baix índex de verdor (NDVI), i amb temperatures mitjanes i màximes més altes que les dominants en la resta de la zona. El contagi espacial entre les dades de presència apareix com una variable molt important. L’àrea ocupada actualment per la Ganga coincideix en gran mesura amb la disponibilitat d’hàbitat potencial que han mostrat els models, tenint en compte el contagi espacial com a variable. Aquestes consideracions suggereixen que les mesures de gestió haurien de concentrar-se de manera efectiva a les zones ocupades en l’actualitat. Cal destacar que la sensibilitat observada a les variables relacionades amb l’estat i estructura de la vegetació i la seva preferència per zones amb valors baixos de NDVI indiquen que les mesures de gestió tals com la creació i manteniment de guarets i erms s’haurien de portar a terme per incrementar la qualitat del microhàbitat disponible per a l’espècie.

Although the breeding ecology of Audouin’s gull has been widely studied, its spatial distribution patterns have received little attention. We assessed the foraging movements of 36 GPS-tracked adult Audouin’s gulls breeding at the Ebro Delta (NW Mediterranean), coinciding with the incubation period (May 2011). This also coincided with a trawling moratorium northwards from the colony. We modelled the distribution of the gulls by combining these tracking data with environmental variables (including fishing activities from Vessel Monitoring System, VMS), using Maxent. The modelling range included both marine and terrestrial areas. Models were produced separately for every 2h time interval across the day, and for 2 fishing activity scenarios (workdays vs. weekends), allowing to assess the spatio-temporal distribution patterns of the gulls and the degree of association with fisheries. During workdays, gull distribution at sea fully matched with fishing activities, both trawling (daylight) and purse-seining (nightime). Gulls tended to avoid the area under trawling moratorium, confirming the high influence of fisheries on the distribution patterns of this species. On weekends, gulls made lesser use of the sea and tended to increase the use of rice fields. Overall, Audouin’s gull activity was more intense during dailight hours, although birds also showed nocturnal activity, on both workdays and weekends. Nocturnal patterns at sea were more disperse during the latter, probably because these gulls are able to capture small pelagic fish at night in natural conditions, but tend to congregate around purse-seiners (which would enhance their foraging efficiency) in workdays. These results provide important insight for the management of this species. This is of particular relevance under the current scenario of European fisheries policies, since new regulations are aimed at eliminating discards, and this would likely influence Audouin’s gull populations. This research was funded under the LIFE+ INDEMARES, LIFE 07 NAT/E/00732 (JB JMA) and MCyI project CGL2008-05448-C02/BOS (MG CS LJ). We also thank the financial support from the University of Barcelona to cover publication costs.

Spatial modelling is an important research tool to improve our knowledge about the distribution of wildlife in the ocean. Using different modelling techniques (MaxEnt and a generalized linear mixed model), a predictive habitat suitability model was developed for one of the most threatened seabirds in the world: the Balearic shearwater, Puffinus mauretanicus. Models were developed using a 10-year dataset from the Gulf of Cádiz (on the south-western Iberian Peninsula), a key foraging area for Balearic shearwaters during migration and the non-breeding season. Predictive habitat maps strongly matched the observed distribution patterns, pointing to bathymetric features as the main modelling drivers. The species was concentrated on shallow areas (up to approximately 100 m in depth) of the continental shelf, very close to the mouth of the Guadalquivir River. In contrast with previous studies, Balearic shearwater distribution in the highly dynamic Gulf of Cádiz was not correlated with areas of high chlorophyll a concentration. This lack of spatial correlation probably arises from the delay between the phytoplankton bloom and the response of the zooplankton and small fish that are preyed upon by Balearic shearwaters, which may result in important displacements of this trophic chain across the Gulf of Cádiz. The analysis presented contributes to a better understanding of the spatial distribution and ecology of the critically endangered top predator in the Gulf of Cádiz and offers important information to improve management plans., This research was partially supported by the Ministry of Science, Innovation and Universities through the MEGAN project (ref. CTM2013-49048-C2-1-R). The publication of this research has been partially funded by the ECOFISH project, with the collaboration of the Biodiversity Foundation from the Ministry for Ecological Transition, through the Pleamar Program, co-financed by the FEMP.

Aves - Orden Procellariiformes - Familia Procellariidae en la Enciclopedia Virtual de Vertebrados Españoles, http://www.vertebradosibericos.org/., A comprehensive review of the natural history of the Cory's Shearwater Calonectris borealis in Spain.