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VIII International Symposium on Marine Sciences, 6-8 July 2022, Las Palmas de Gran Canaria, España, Increasing impacts of both fisheries and climate change have resulted in changes in the structure, functioning and related ecological metrics of marine communities. A recurrent observation is the rise of cephalopods as fish communities recede. The reason behind this phenomenon is most likely linked with the removal of main predators and competitors by fishing. However, the consequences of climate change (variations in primary production, changes in stratification, and sea warming, among others) may also have an influence due to the high environmental sensitivity and plasticity of cephalopods. Here we aim to unveil the effects of different drivers in the cephalopod community of the Western Mediterranean Sea as well as its differential role in space. We combine several ecological indicators offering a wide range of information about biodiversity, production, trophic structure and relative contribution of prey and predators and relate them with environmental and fisheries drivers of change. The ecological indicators are calculated using data from the MEDITS trawling survey in the region (from the Alboran Sea to the Gulf of Lion) from 2013 to 2019. Our results highlight the response of ecological indicators to several drivers of change and the spatial differences in cephalopod communities with, for instance, higher richness and proportion of predator cephalopods in areas associated to higher SST and fishing effort. Overall, the effect of the environment is greater than the effect of other variables; such results may highlight that under foreseeing scenarios of climate change cephalopods could continue to increase due to increases in sea warming, This study was partially funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 817578 (TRIATLAS) and No 869300 (FutureMARES). C. Veloy’s contribution was supported by a PhD fellowship from the Spanish Ministry of Education (FPU18/05594) and the University of Barcelona. This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019- 000928-S). MH and MC also acknowledge support from the COCOCHA project (PID2019- 110282RA-I00, Spanish Ministry of Science and Innovation)

VII International Symposium on Marine Sciences (ISMS 2020), 1-3 July 2020 (Barcelona).-- 2 pages, The Mediterranean Sea is a marine ecosystem with high heterogeneity in its physical, chemical, biological and ecological characteristics, with clear north-south and east-west gradients. It is also an important area in terms of biodiversity and conservation of vulnerable species, as it suffers several human impacts, like fishing and climate change. Previous studies have characterized spatial and temporal patterns of species distribution and biodiversity indicators. However, a community-based analysis combining specific indicators sensitive to fishing impact and climate variability that help to identify which areas and taxa are most sensitive to specific drivers is still missing. In this study, we examined spatio-temporal changes of marine communities along a latitudinal gradient off Spain’s mainland in the Western Mediterranean Sea using data from the MEDITS surveys from 1994 to 2017. Several ecological indicators measuring α (richness, Shannon index and Pielou's evenness index) and β diversity (assessing both turnover and nestedness) were selected, as well as indicators linked with changes in communities due to fishing impact or climate change, like community biomass and functional groups, relative predator weight and trophic level metrics. We used correlation analyses between these indicators and other variables (among them year, location and subarea) and spatial-temporal statistical models to assess variations in the indicators and spatial-temporal gradients. Our results clearly show a heterogeneous response between taxa and area, with a remarkable increase in several indicators when focusing on cephalopods. Our study shows a contrasting response between taxonomic groups suggesting a change in the ecosystem functioning over time in the Western Mediterranean Sea. This in depth analysis of the ecosystem serves as a case study for the use of selected indicators that combine the capacity to detect changes both at regional and local scales, This study has beenfunded by the European project TRIATLAS (BG-08-2018-2019-RIA-SEP-210482854), predoctorals cholarships of the Spanish Ministry of Science and Universities (FPU18/05594) and the European Maritime and Fisheries Fund (EMFF) within the National Program of collection, management and use of data in the fisheries sector and support for scientific advice regarding the Common Fisheries Policy, that support the MEDITS program

Marine litter is one of the main sources of anthropogenic pollution in the marine ecosystem, with plastic representing a global threat. This paper aims to assess the spatial distribution of plastic macro-litter on the seafloor, identifying accumulation hotspots at a northern Mediterranean scale. Density indices (items km–2) from the MEDITS trawl surveys (years 2013-2015) were modelled by generalized additive models using a Delta-type approach and several covariates: latitude, longitude, depth, seafloor slope, surface oceanographic currents and distances from main ports. To set thresholds for the identification of accumulation areas, the percentiles (85th, 90th and 95th) of the plastic spatial density distribution were computed on the raster data. In the northern Mediterranean marine macro-litter was widespread (90.13% of the 1279 surveyed stations), with plastic by far the most recurrent category. The prediction map of the plastic density highlighted accumulation areas (85th, 90th and 95th percentiles of the distribution, respectively, corresponding to 147, 196 and 316 items km–2) in the Gulf of Lions, eastern Corsica, the eastern Adriatic Sea, the Argo-Saronic region and waters around southern Cyprus. Maximum densities were predicted in correspondence to the shallower depths and in proximity to populated areas (distance from the ports). Surface currents and local water circulation with cyclonic and anticyclonic eddies were identified as drivers likely facilitating the sinking to the bottoms of floating debris., La basura marina es una de las principales fuentes de contaminación antropogénica en el ecosistema marino representando el plástico una amenaza global. El objetivo de este trabajo es evaluar la distribución espacial de las macro-basuras plásticas en el fondo marino, identificando los hotspots de acumulación en el Mediterráneo norte. Los índices de densidad (ítems km–2), procedentes de las campañas de arrastre MEDITS (años: 2013-2015), fueron modelados mediante Modelos Aditivos Generalizados, utilizando un enfoque de tipo delta y varias covariables: latitud, longitud, profundidad, pendiente del fondo marino, corrientes marinas y distancias desde los principales puertos. Para establecer los umbrales para la identificación de áreas de acumulación, se calcularon los percentiles (85-90-95) de la distribución espacial de densidad de plásticos en los datos ráster. En el Mediterráneo norte, la macro-basura marina estaba muy extendida (90.13% de las 1279 estaciones muestreadas), siendo el plástico, con diferencia, la categoría más recurrente. El mapa de predicción de la densidad de plásticos resaltó las áreas de acumulación (percentiles 85, 90 y 95 de la distribución, respectivamente, correspondientes a: 147, 196 y 316 ítems km–2), localizadas en el Golfo de León, Córcega oriental, Mar Adriático oriental, región Argo-Saronic y aguas que rodean el sur de Chipre. Se predijeron las densidades máximas a menor profundidad y cercanas a zonas pobladas (distancia desde los puertos). Las corrientes superficiales y la circulación local del agua, con giros ciclónicos y anticiclónicos, se identificaron como factores que favorecen el hundimiento de las basuras flotantes.

Most studies on European hake focus on the recruitment process and nursery areas, whereas the information is comparatively limited on the ecology of the juvenile stage (ca. second year of life)—the one most exploited by the Mediterranean trawl fisheries. Using information of the MEDITS programme, we provide a spatial and temporal assessment of the influence of body size and growth on hake survival from recruits (age 0) to juveniles (age 1), along with the impact of surface temperature and chlorophyll variability. At a biogeographic scale, size-dependent survival is supported, with areas with higher mean length of recruits and juveniles yielding higher survival. A similar pattern was observed at interannual level in some western Mediterranean areas, also mediated by a density-dependent effect on growth. However, the most recurrent inter-annual pattern was a negative effect of size on survival, which could be attributed to potential ontogenetic changes in catchability and underrepresentation of intra-annual recruitment pulses that are seasonally inaccessible to the MEDITS survey. Results also evidence that survival in the Alboran and Adriatic seas is dependent on the primary production variability, and that Corsica and Sardinia could be potential feeding grounds receiving juveniles from neighbouring areas. The present study reveals the importance of size- and growth-dependent survival in the juvenile stage of European hake in the Mediterranean Sea., La mayoría de estudios de merluza europea se han centrado en el proceso de reclutamiento y sus hábitats preferentes, mientras que la información es mucho más escasa sobre los procesos ecológicos asociados a la fase juvenil (i.e. segundo año de vida aproximadamente), la cual se considera la más impactada por la pesca de arrastre en el Mediterráneo. En este estudio usamos la información del programa MEDITS para investigar, temporal y espacialmente, la posible influencia del tamaño corporal y el crecimiento sobre la supervivencia desde la fase de reclutas (edad 0) a la de juveniles (edad 1). También se ha evaluado la posible influencia de la temperatura y la clorofila superficial. A una escala biogeográfica, los resultados corroboran la influencia de la talla sobre la supervivencia, con mayor supervivencia asociada a áreas de mayor talla media de reclutas y juveniles. El mismo patrón se observó a escala interanual en algunas zonas del oeste el Mediterráneo, en las cuales se detectó también un efecto de denso-dependencia en el reclutamiento. Sin embargo, el patrón interanual más recurrente fue un efecto negativo de la talla sobre la supervivencia, que podría ser atribuido tanto a cambios ontogenéticos en la capturabilidad de los peces como a la posible infraestimación de los pulsos interanuales de reclutamiento que pueden resultar estacionalmente inaccesibles a las campañas MEDITS. Los resultados también evidencian que la supervivencia en Alborán y el Adriático depende de la variabilidad de la producción primaria, y que Córcega y Cerdeña podrían ser potencialmente áreas de alimentación que reciben juveniles de áreas adyacentes. El presente estudio evidencia la importancia de la influencia de la talla corporal y el crecimiento sobre la supervivencia juvenil de la merluza europea en el mar Mediterráneo.

The Mediterranean distributions of two species of anglerfish, the blackbellied anglerfish (Lophius budegassa) and the white anglerfish (Lophius piscatorius), were analysed from trawl survey data (MEDITS project – Spain, France, Italy and Greece) from 2006 to 2015 implementing a Delta model approach with residuals autocovariate boosted regression trees. Sea bottom temperature (SBT), sea bottom salinity (SBS), bathymetry, slope of the seabed and distance to the coast were considered possible predictors. The results show that the locations with a higher presence, abundance and biomass of L. budegassa are those with a depth range between 150 to 300 m, with an SBT range between 17.5 and 18.5°C, and SBS of 37-38 PSU. Similarly, L. piscatorius shows a higher probability of presence, abundance and biomass in location with a bathymetry range of 200-400 m, an SBT of 17.5°C to 18.5°C and an SBS of 36.5 to 37.5. Our results identify preference habitats for the anglerfishes in the Mediterranean Sea such as the Aegean Sea, the Gulf of Lions, south and southeast Spain and the northwestern Ionian Sea. In general terms, these findings enhance our understanding of the differences in the spatio-temporal distribution of these two species, providing useful information that can help their fisheries management and conservation., En este trabajo se ha analizado la distribución de las dos especies de rape (Lophius budegassa y Lophius piscatorius) presentes en el Mediterráneo a partir de los datos de campaña del Proyecto MEDITs de España, Francia, Italia y Grecia desde el año 2006 al 2015, aplicando una aproximación del modelo Delta con árboles de regresión aumentada con autocovarianza en los residuos. Se consideraron como posibles predictores la temperatura y salinidad del agua del fondo, la batimetría, la pendiente del fondo y la distancia a la costa. Los resultados muestran que localidades con mayores presencias, abundancias y biomasas del rape negro (Lophius budegassa) son aquéllas con un rango de profundidad entre 150 y 300 mm, con un rango de temperaturas del agua en el fondo (SBT) entre 17.5 y 18.5°C, y una salinidad del agua del fondo (SBS) entre 37-38 PSU. De igual manera el rape blanco (Lophius piscatorius) muestra la probabilidad más alta de presencia, abundancia y biomasa en localidades con profundidades comprendidas entre 200-400 m, una SBT entre 17.5-18.5°C y 36.5-37.5 PSU de SBS. Nuetros resultados identifican como hábitats preferenciales de los rapes el mar Egeo, el Golfo de Lion, el sur y sureste de España y el noroeste del mar Jónico. En términos generales estos hallazgos proporcionan una información que mejora nuestra comprensión sobre las diferencias espacio-temporales de la distribución de las dos especies de rape, proporcionando una información muy útil que puede ayudar en la gestión de su pesquería y conservación.

The high species richness, coupled with high proportion of endemism, makes the Mediterranean one of the world’s ‘biodiversity hotspots’. However, the continuous increase in fisheries in the last few decades has led to the overexploitation of their main commercial stocks. Using fishery-independent data collected under the framework of the MEDITS trawl surveys carried out over the last 20 years, we study the demersal fish diversity pattern in the Mediterranean at a large spatial and temporal scale to determine whether it is being affected by the general fishing overexploitation of the demersal resources. The detected diversity trends are compared with the spatio-temporal variation in bottom trawl fishing effort in the Mediterranean. Our results show a stability and even recovery of demersal fish diversity in the Mediterranean together with higher diversity values on the continental shelves of the Balearic Islands, Sardinia, Sicily and the Aegean Sea. At large temporal and spatial scales, the high diversity of demersal assemblages in the Mediterranean is associated with a reduction in bottom trawl fishing effort. The inclusion of species other than target ones through diversity indices is important in the implementation of an ecosystem-based fisheries management., Debido a su alta riqueza específica y su gran proporción de organismos endémicos, el Mediterráneo es considerado un punto caliente de biodiversidad. No obstante el continuo crecimiento de las pesquerías en las últimas décadas ha desembocado en una sobrexplotación de sus principales stocks comerciales. A través de datos independientes de las pesquerías recogidos en el marco de las campañas MEDITS desarrolladas durante las dos últimas décadas se ha estudiado el patrón de diversidad de peces demersales en el Mediterráneo a través de largas escalas temporales y espaciales para evaluar si este patrón se ve afectado por el estado general de sobrexplotación de sus recursos demersales. A continuación las tendencias detectadas en la diversidad han sido comparadas a la variación espacio-temporal del esfuerzo de la pesca de arrastre a través del Mediterráneo. Nuestros resultados muestran una estabilidad e incluso recuperación de la diversidad de peces demersales en el Mediterráneo junto a valores altos de diversidad en las plataformas continentales de las Islas Baleares, Cerdeña, Sicília y el mar Egeo. La alta diversidad de las asociaciones de peces demersales a escala tanto espacial como temporal está asociada a una reducción del esfuerzo pesquero. La inclusión de especies distintas a las objetivo a través de índices de diversidad es relevante en la implementación de la aproximación ecosistémica a la gestión de las pesquerías.

The present study provides updated information on the occurrence, abundance and biomass distribution patterns and length frequencies of Merluccius merluccius in the Mediterranean Sea, by analysing a time series of data from the Mediterranean International Trawl Surveys (MEDITS) from 1994 to 2015. The highest values of abundance and biomass were observed in the Sardinian Seas. The use of a generalized additive model, in which standardized biomass indices (kg km–2) were analysed as a function of environmental variables, explained how ecological factors could affect the spatio-temporal distribution of European hake biomass in the basin. High biomass levels predicted by the model were observed especially at 200 m depth and between 14°C and 18°C, highlighting the preference of the species for colder waters. A strong reduction of biomass was observed since the year 2009, probably due to the strengthening of the seasonal thermocline that had greatly reduced the availability of food. The general decrease in biomass of several stocks of anchovy and sardine, preys of European hake, might be indirectly connected to the decreasing biomass detected in the present study. The length analysis shows median values lower than 200 mm total length of most of the investigated areas., El presente estudio proporciona información sobre los patrones de ocurrencia, abundancia y distribución de biomasa, y las longitudes de Merluccius merluccius en el mar Mediterráneo, considerando el análisis de una serie temporal proveniente de las campañas internacionales de pesca de arrastre en el Mediterráneo (MEDITS) de 1994 a 2015. Los valores más altos de abundancia y biomasa se observaron en los mares de Cerdeña. El uso del modelo GAM, en el que se analizaron los índices estandarizados de biomasa (BI, kg km–2) en función de las variables ambientales, permitió explicar cómo los factores ecológicos podrían afectar la distribución espacio-temporal de la biomasa de merluza europea en la cuenca. Los niveles altos de biomasa pronosticados por el modelo se observaron especialmente a 200 m de profundidad y entre 14 y 18°C, destacando la preferencia de la especie por aguas más frías. Se observó una fuerte reducción de la biomasa desde el año 2009, probablemente debido al fortalecimiento de la termoclina estacional que había reducido en gran medida la disponibilidad de alimentos. Otros procesos como la disminución general de la biomasa de varias poblaciones de anchoa y sardina, las presas de merluza europea, podrían estar indirectamente relacionadas con la disminución de la biomasa detectada en el presente estudio. El análisis de longitud muestra valores medios inferiores a 200 mm TL de la mayoría de las áreas investigadas.

21 pages, 8 figures, 1 table, supporting information https://doi.org/10.1111/mec.16840.-- Data Availability Statement: Raw reads have been deposited to European Nucleotide Archive (ENA) under the accession id PRJEB45992. A VCF file with all filtered and unlinked SNPs used in the analyses of this study is provided as an additional file., By evaluating genetic variation across the entire genome, one can address existing questions in a novel way while raising new ones. The latter includes how different local environments influence adaptive and neutral genomic variation within and among populations, providing insights into local adaptation of natural populations and their responses to global change. Here, under a seascape genomic approach, ddRAD data of 4609 single nucleotide polymorphisms (SNPs) from 398 sardines (Sardina pilchardus) collected in 11 Mediterranean and one Atlantic site were generated. These were used along with oceanographic and ecological information to detect signals of adaptive divergence with gene flow across environmental gradients. The studied sardines constitute two clusters (FST = 0.07), a pattern attributed to outlier loci, highlighting putative local adaptation. The trend in the number of days with sea surface temperature above 19°C, a critical threshold for successful sardine spawning, was crucial at all levels of population structuring with implications on the species' key biological processes. Outliers link candidate SNPs to the region's environmental heterogeneity. Our findings provide evidence for a dynamic equilibrium in which population structure is maintained by physical and ecological factors under the opposing influences of migration and selection. This dynamic in a natural system warrants continuous monitoring under a seascape genomic approach that might benefit from a temporal and more detailed spatial dimension. Our results may contribute to complementary studies aimed at providing deeper insights into the mechanistic processes underlying population structuring. Those are key to understanding and predicting future changes and responses of this highly exploited species in the face of climate change, This study was carried out within the European Research Contract SPELMED (EASME/EMFF/2016/032) funded by the Executive Agency for Small- and Medium-sized Enterprises (EASME) of the European Commission (DGMARE). [...]. MC would like to acknowledge partial funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 869300 (FutureMARES). MC and FR acknowledge the institutional support of the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S). FR was supported by the Ramón y Cajal programme (Spanish Ministerio de Ciencia e Innovación, RYC2020-030078-I). This research was supported in part through computational resources provided by IMBBC (Institute of Marine Biology, Biotechnology and Aquaculture) of the HCMR (Hellenic Centre for Marine Research). Funding for establishing the IMBBC HPC has been received from the MARBIGEN (EU Regpot) project, LifeWatchGreece RI and the CMBR (Centre for the study and sustainable exploitation of Marine Biological Resources) RI, implemented under the Action “Reinforcement of the Research and Innovation Infrastructure,” funded by the Operational Programme “Competitiveness, Entrepreneurship and Innovation” (NSRF 2014-2020) and cofinanced by Greece and the European Union (European Regional Development Fund)

Increasing human pressures and global environmental change may severely affect the diversity of species assemblages and associated ecosystem services. Despite the recent interest in phylogenetic and functional diversity, our knowledge on large spatio-temporal patterns of demersal fish diversity sampled by trawling remains still incomplete, notably in the Mediterranean Sea, one of the most threatened marine regions of the world. We investigated large spatio-temporal diversity patterns by analysing a dataset of 19,886 hauls from 10 to 800 m depth performed annually during the last two decades by standardised scientific bottom trawl field surveys across the Mediterranean Sea, within the MEDITS program. A multicomponent (eight diversity indices) and multi-scale (local assemblages, biogeographic regions to basins) approach indicates that only the two most traditional components (species richness and evenness) were sufficient to reflect patterns in taxonomic, phylogenetic or functional richness and divergence. We also put into question the use of widely computed indices that allow comparing directly taxonomic, phylogenetic and functional diversity within a unique mathematical framework. In addition, demersal fish assemblages sampled by trawl do not follow a continuous decreasing longitudinal/latitudinal diversity gradients (spatial effects explained up to 70.6% of deviance in regression tree and generalised linear models), for any of the indices and spatial scales analysed. Indeed, at both local and regional scales species richness was relatively high in the Iberian region, Malta, the Eastern Ionian and Aegean seas, meanwhile the Adriatic Sea and Cyprus showed a relatively low level. In contrast, evenness as well as taxonomic, phylogenetic and functional divergences did not show regional hotspots. All studied diversity components remained stable over the last two decades. Overall, our results highlight the need to use complementary diversity indices through different spatial scales when developing conservation strategies and defining delimitations for protected areas., SI

Species diversity is widely recognized as an important trait of ecosystems’ functioning and resilience. Understanding the causes of diversity patterns and their interaction with the environmental conditions is essential in order to effectively assess and preserve existing diversity. While diversity patterns of most recurrent groups such as fish are commonly studied, other important taxa such as cephalopods have received less attention. In this work we present spatio-temporal trends of cephalopod diversity across the entire Mediterranean Sea during the last 19 years, analysing data from the annual bottom trawl survey MEDITS conducted by 5 different Mediterranean countries using standardized gears and sampling protocols. The influence of local and regional environmental variability in different Mediterranean regions is analysed applying generalized additive models, using species richness and the Shannon Wiener index as diversity descriptors. While the western basin showed a high diversity, our analyses do not support a steady eastward decrease of diversity as proposed in some previous studies. Instead, high Shannon diversity was also found in the Adriatic and Aegean Seas, and high species richness in the eastern Ionian Sea. Overall diversity did not show any consistent trend over the last two decades. Except in the Adriatic Sea, diversity showed a hump-shaped trend with depth in all regions, being highest between 200–400 m depth. Our results indicate that high Chlorophyll a concentrations and warmer temperatures seem to enhance species diversity, and the influence of these parameters is stronger for richness than for Shannon diversity, SI