23 pages, 10 figures, 5 tables, In the present work, possible long-term changes in the planktonic cnidarian community were investigated by analyzing (1) species and community spatial distribution patterns, (2) variations in abundance and (3) changes in species richness during three mesoscale surveys representative of the climatic and anthropogenic changes that have occurred during the last three decades (years: 1983, 2004 and 2011) in the NW Mediterranean. These surveys were conducted during the summer (June) along the Catalan coast. All surveys covered the same area, used the same sampling methodology, and taxonomic identification was conducted by the same team of experts. An increase in the abundance of total cnidaria was found from 1983 to 2011. The siphonophore Muggiaea atlantica and the hydromedusa Aglaura hemistoma were the most abundant species, while Muggiaea kochii presented the largest abundance increment over time. Temperature was the main environmental parameter driving significant differences in the cnidarian community composition, abundance and spatial distribution patterns among the surveys. Our results suggest that in the current climate change scenario, warm-water species abundances will be positively favored, and the community will suffer changes in their latitudinal distribution patterns. We consider it extremely important to study and monitor gelatinous zooplankton in mesoscale spatial areas to understand not only long-term changes in abundances but also changes in their spatial distributions since spatial changes are sensitive indicators of climate change, This study was partially supported by the EU Project VECTORS, FP7 OCEAN-2010-266445 (http://www.marine-vectors.eu, Vectors of Change in Oceans and Seas Marine Life, Impact on Economic Sectors, grant no. 266445) and the Spanish projects CTM2010-18874/MAR and CTM2015-68543-R, funded by the Spanish Ministry of Economy and Competitiveness, Peer Reviewed

14 pages, 7 figures, 4 tables, Fish–jellyfish associations were studied close to Barcelona (NW Mediterranean) during the summer period from 2008 to 2014. Jellyfish and their associate juvenile fish were collected, identified, counted, and measured. Fish behaviour was described by visual field observations and laboratory experiments were performed to determine the survival of the associated fish after being in contact with the jellyfish. In addition, the possible contribution of jellyfish to the dietary composition of the fish was assessed using a combination of biomarkers. Trachurus mediterraneus, Trachurus trachurus, and Caranx rhonchus were associated with the jellyfish Rhizostoma pulmo and Cotylorhiza tuberculata. Trachurus mediterraneus was the most frequent species and their size during the association ranged between 8.4 and 66 mm standard length. The size and number of T. mediterraneus were slightly correlated with the size of R. pulmo, but not with that of C. tuberculata, although more numerous fish were found swimming with C. tuberculata. Behaviour studies showed that juvenile fish swam around jellyfish and into their oral arms seeking shelter without suffering any pain. This survival capability was corroborated by experimental work in which all the specimens of T. mediterraneus survived after being in contact with both jellyfish species. Stable isotopes and fatty acids also revealed an important contribution of R. pulmo and C. tuberculata to T. mediterraneus diet. Defining better the associations between jellyfish and juvenile fish will help to understand the effects of the association on the survival and recruitment of fish species potentially ecologically and economically relevant, This work was supported by the projects CTM2010-18874 and CTM2015-68543-R (Spanish Ministry of Economy and Competitiveness). UT was supported by a predoctoral fellowship of the FPI program (Spanish Ministry of Economy and Competitiveness), Peer Reviewed

10 pages, 7 figures, 2 tables, This study investigates the possible pathways for Pelagia noctiluca intrusions over the shelf to understand the interactions between jellyfish and fish larvae. To assess how the presence of P. noctiluca may influence populations of Engraulis encrasicolus and Trachurus trachurus, we analyzed the effect of environmental conditions on the abundance and spatial distribution of P. noctiluca, medusae and ephyrae, and early life stages of these two fish species along the Catalan coast. The highest concentrations of P. noctiluca were found offshore, all along the Northern Current path. Their occurrence over the shelf was associated with intrusions of open sea waters that contoured anticyclonic eddies generated by the oscillatory behaviour of the current. Anchovy larvae were found widely over the shelf, but were especially abundant in the north and in waters influenced by the Ebro river. Spatial patterns of anchovy larvae were defined better by physical environmental factors than by the presence of P. noctiluca, whose distribution clearly was determined by the circulation. The differences in environmental conditions controlling the populations of P. noctiluca and E. encrasicolus larvae prevent their general coexistence over the shelf and prey-predator interactions remained limited to the areas affected by offshore intrusions. It is remarkable that the occurrence of T. trachurus larvae and juveniles was limited to locations over the shelf where jellyfish were observed and never offshore. This suggests that the association between fish and jellyfish occur once jellyfish have been advected from offshore towards the shelf, favouring the survival of larvae and juveniles of T. trachurus, This research was funded by projects CTM2010-18874/MAR and CTM2015-68543-R, and U.T. was supported by a predoctoral fellowship of the FPI program (Spanish Ministry of Economy and Competitiveness), Peer Reviewed

9 pages, 6 figures, 2 tables, This study analyses the trophic ecology of the horse mackerel (Trachurus mediterraneus) juveniles associated with two jellyfish species, Rhizostoma pulmo and Cotylorhiza tuberculata, in the NW Mediterranean. The aim was to know whether the natural diet composition of the hosted fish could be influenced by the jellyfish species and to explore if the fish could feed on the host jellyfish. Samplings were carried out off the coast of Barcelona in summer 2011 at depths of up to 10 m. Juveniles associated with C. tuberculata showed a higher feeding incidence and number of ingested prey than those associated with R. pulmo. The relative importance of the different prey varied depending on the jellyfish species with which fish were associated. In juveniles associated with C. tuberculata, the diet was similar to the composition of the ambient zooplankton, with the cladocera Evadne spp. and Calanoida copepods as the most important prey. However, juveniles associated with R. pulmo fed mainly on Calanoida and Harpacticoida copepods. These differences could be related to the depth-associated behaviour of each jellyfish species, with R. pulmo particularly making deeper living plankton accessible to the horse mackerel juveniles. The presence of nematocyst cells in the juvenile gut contents suggests that they fed on the host jellyfish, either directly on the jellyfish tissue or accidentally when they remove the prey captured by the jellyfish oral arms. Our results provide a better understanding of the associations between jellyfish and juvenile fish which can have important effects on fish population dynamics, This work was supported by the Spanish Ministry of Economy and Competitiveness (CTM2010-18874 and CTM2015-68543-R). JM was supported by a predoctoral FI-AGAUR fellowship of the University and Research Grants Management Agency (AGAUR) of the Government of Catalonia (Generalitat de Catalunya) (FI_B_00412), Peer Reviewed

13 pages, 3 figures, 3 tables, supporting Information https://dx.doi.org/10.1111/fog.12464, We investigated the effects of three sea surface oceanographic variables (temperature, salinity and chlorophyll a) on the abundance of eggs and larvae of two summer-spawning species in the NW Mediterranean sea, the anchovy Engraulis encrasicolus and the round sardinella Sardinella aurita, based on data from ichthyoplankton surveys carried out in the 1980s, 2000s and 2010s. The environmental data showed an increase in sea water temperature and salinity along time, coupled with a decrease in chlorophyll a (proxy for primary production). These long-term directional changes in environmental conditions helped explain the important reduction observed in the abundance of eggs and larvae of anchovy, as well as shrinking of spawning habitat in this species. At the same time, the probability of occurrence of round sardinella has increased from practically zero in the 1980s to probabilities near 1 along the coastal area of the study region in the two decades of the 21st century. Given that the trends observed in the environmental variables along the three decades of study are expected to continue during the 21st century, as a consequence of climate change, the spawning habitat of anchovy is expected to continue decreasing, while round sardinella habitat can expand. Considering that anchovy is of high commercial importance in NW Mediterranean fisheries, while round sardinella has very low commercial interest, our results show that the viability of small pelagic fisheries in the area may be compromised, This research is partially supported by the CERES project (H2020, EU 678193) and by the Spanish Ministry of Economy and Competitiveness (CTM2010-18874 and CTM2015-68543-R), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI), Peer reviewed

Este artículo contiene 11 páginas, 10 figuras, 4 tablas., Life-history traits as growth, age at first maturity, reproduction and condition as well as the size distribution of the commercial and the discarded catch, have been studied for the blue whiting, Micromesistius poutassou, from the NW Mediterranean. This is a species of commercial interest in the area. In the last decade its landings remained at very low levels and the stock has not shown signs of recovery. Samplings were conducted monthly in the northern Catalan coast on board a commercial bottom trawler, from October 2016 to October 2018. The results showed a high variability in the size at age. The size at first maturity was around 18 cm for both sexes that is achieved when the species completes its first year of life, that is, the spawning season following its birth. Females and males showed different growth curves, with females reaching higher sizes than males. From 25 cm TL females became dominant in the population. The readings of lapilli otoliths of very young individuals (from 42–87 days old) allowed an accurate estimate of the growth parameters. The diameter of the first annual ring in the sagitta otoliths was defined for the NW Mediterranean (9.8 ± 0.74 mm). The diameter of the observed two false annual rings were also provided. This study has also shown a close relationship between reproduction, condition and stomach fullness trends, which, in turn, have been observed to be related with the changes in the species growth during the year. Finally, the study allowed knowing the very high amount of blue whiting discards. The main component of catches (in numbers) corresponded to discarded individuals, and, in addition, the minimum landing size implemented in the study area is smaller than the size at first maturity., This work was supported by the project CTM2015-68543-R (Spanish
Ministry of Economy and Competitiveness); J.M-A. was supported by a
predoctoral fellowship of the FI program (2019FI_B2 00183) of the
Secretaria d’Universitats i Recerca de la Generalitat de Catalunya and
Fons Social Europeu (FSE)., With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)., Peer reviewed

10 pages, 3 figures, 2 tables, Accurate information on commercial marine species larvae is key to fisheries science, as their correct identification is the first step towards studying the species’ connectivity patterns. In this study, we provide a complete morphological description of the first protozoeal stage of the valued deep-sea blue and red shrimp Aristeus antennatus and of the small mesopelagic shrimp Gennadas elegans. These two larval morphologies previously posed a risk of misidentification, thus hindering the study of A. antennatus larval ecology and dynamics in the context of fisheries science. Using specimens caught in the plankton at various locations in the Northwestern Mediterranean Sea and identification confirmed by molecular methods, the larvae of A. antennatus and G. elegans are distinguished from each other by the ornamentation of the antennula. A possible confusion in previous descriptions of Aristeidae larvae is addressed and a new key for the identification of Dendrobranchiata larvae provided, This research was carried out within project CONECTA (CTM2014-54648-C2) funded by the Spanish Ministerio de Economía y Competitividad (MINECO).The authors would like to thank Dr. A. Sabatés for providing the winter zooplankton samples from project WINFISH (CTM2015-68543-R). M. Carreton benefited from a FPU2015 grant from the Spanish Ministerio de Educación y Formación Profesional. L. Faria de Sousa was supported by the grant PLANTROF Dinâmica do plâncton e transferência trófica: Biodiversidade e ecologia do zooplâncton de Portugal: Mar 2020-Programa Operacional Mar 2020 Portaria N. 118/2016, and this research was partly supported by the project “Towards an integrated approach to enhance predictive accuracy of jellyfish impact on coastal marine ecosystems- Jellyfisheries” 2015-2018 FEDER 16772, FCT, IP - PTDC/MAR-BIO/0440/2014, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

23 pages, 8 figures, 1 table, supplementary material https://doi.org/10.1007/s10584-020-02723-4, We studied the effect of climate change on the potential spawning habitats of two marine small pelagic fishes. We examined the projected changes in the potential spawning habitat of the summer-spawning anchovy (Engraulis encrasicolus) and round sardinella (Sardinella aurita) in the northwestern Mediterranean by combining the regionalized projections of RCP scenarios with an existing species distribution model (SDM). The SDM was based on a separate generalized additive model for the eggs and larvae of the two species computed from ichthyoplankton sampling that was conducted with simultaneous readings of surface temperature, salinity and chlorophyll-a values as predictor variables. The SDM was projected for the 2010 decade, which represented the present-day conditions, with these environmental variables obtained from the regionalized POLCOMS-ERSEM biogeochemical model forced by the RCP 4.5 and RCP 8.5 scenarios. The comparison of the present-day projection results with the projections for the middle and final decades of the twenty-first century showed that the suitability of the spawning habitat as defined by the anchovy eggs model was likely to increase over time under RCP4.5 or decrease slightly under RCP8.5, but the habitat for anchovy larvae was likely to decrease in all cases. Loss of habitat was projected to be particularly important in the south of the study area on the Ebre River delta continental shelf. Conversely, the probability of round sardinella occurrence will significantly increase under both scenarios. The potential habitat of this species, which is of subtropical origin, is likely to shift northwards. The limitations of the existing models to extrapolate the current results to future scenarios are discussed regarding (i) the uncertainty in the projections of driving environmental variables (e.g., chlorophyll-a), (ii) the simplified nature of the projection models, which did not capture the dynamics of the early life stages of the fish at a small scale, and (iii) insufficient consideration of important drivers, such as larval transport or retention by mesoscale hydrographic phenomena, This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Grant Agreement “CERES” No. 678193 and from the Spanish Ministry of Economy and Competitiveness (CTM2010-18874 and CTM2015-68543-R). Eduardo Ramirez-Romero received funding from “Govern de les Illes Balears—Conselleria d’Innovació, Recerca i Turisme, Programa Vicenç Mut.”, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

16 pages, 6 figures, 4 tables, supplementary data https://doi.org/10.1016/j.dsr.2020.103404, We investigated the feeding ecology of blue whiting (Micromesistius poutassou) in the NW Mediterranean living in two habitats, the shelf break and the continental slope, throughout the year, by combining two methodological approaches, stomach content characterization and stable isotope analyses. Stomach content indicated that blue whiting mainly fed on Myctophidae fish, decapods and euphausids. Differences in diet were observed between areas and throughout the year, with a higher proportion of Myctophidae in individuals living over the shelf break (attaining values ~ 70% weight) than over the slope (attaining values ~ 50% weight). In both habitats Myctophidae, a highly energetic prey, were mainly consumed in spring and summer, which might allow the species to recover energy reserves after the reproductive period and supply the energetic demands of the fast growth season. MixSIAR models, which provide estimates of the relative contribution of each prey to the diet of the consumer by combining stable isotope values of the consumer with those of their potential prey, also indicated that Myctophidae were the main prey in the assimilated diet over the entire year, in both areas. The trophic niche, measured by isotope analyses, suggested segregation between individuals of the shelf break (mainly immatures) and the slope (mainly adults), which would reduce the intraspecific competition. The seasonal and spatial differences observed in the feeding ecology of the Mediterranean blue whiting are related to the energetic requirements of the species throughout the year and with changes in the spatial distribution of the different ontogenetic phases, J.M-A. was supported by a predoctoral fellowship of the FI program of the Secretaria d’Universitats i Recerca de la Generalitat de Catalunya, Spain, and Fons Social Europeu (FSE) [2019FI_B2 00183]. JN was funded by the Spanish National Program Ramón y Cajal (RYC-2015-17809), Ministry of Science and Innovation, Spain. This work was supported by the Spanish Ministry of Economy and Competitiveness [CTM2015-68543-R], Spain, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Contribution to the Theme Section Latest advances in research on fish early life stages.-- 20 pages, 9 figures, 4 tables, 1 appendix, This work develops a new method, the box-balance model (BBM), to assess the role of hydrodynamic structures in the survival of fish larvae. The BBM was applied in the northwest Mediterranean to field data, on 2 small pelagic fish species whose larvae coexist in summer: Engraulis encrasicolus, a dominant species, and Sardinella aurita, which is expanding northwards in relation to sea warming. The BBM allows one to quantify the contribution of circulation, with significant mesoscale activity, to the survival of fish larvae, clearly separating the effect of transport from biological factors. It is based on comparing the larval abundances at age found in local target areas, associated with the mesoscale structures (boxes), to those predicted by the overall mortality rate of the population in the region. The application of the BBM reveals that dispersion/retention by hydrodynamic structures favours the survival of E. encrasicolus larvae. In addition, since larval growth and mortality rates of the species are required parameters for application of the BBM, we present their estimates for S. aurita in the region for the first time. Although growth and mortality rates found for S. aurita are both higher than for E. encrasicolus, their combined effect confers a lower survival to S. aurita larvae. Thus, although the warming trend in the region would contribute to the expansion of the fast-growing species S. aurita, we can confirm that E. encrasicolus is well established, with a better adapted survival strategy, This research was supported by the project CTM2015-68543-R (Spanish Ministry of Economyand Competitiveness), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI), Peer reviewed

17 pages, 9 figures, 4 tables, supplementary material https://doi.org/10.3354/meps13748, We assessed the trophic ecology of blue whiting larvae in the NW Mediterranean by means of stomach content analyses in relation to their planktonic trophic environment. The trophic position of blue whiting larvae and that of the main taxa of the planktonic community was estimated by means of stable isotope analyses. Larvae and zooplankton were sampled in 2 oceanographic cruises conducted in the winters of 2017 and 2018. Blue whiting larvae showed a marked diel feeding pattern and high feeding incidence (~90%). Throughout ontogeny, dietary changes were observed in the taxonomic composition, size and number of ingested prey. The smallest larvae fed on small prey, Tintinnina and nauplii, shifting to larger more energetic prey, Calanoida copepods, as development progressed. From the flexion stage onwards, larvae showed a positive selection for Calanoida, and no major switch in prey size or type was observed due to the scarcity of larger prey in the field. This limitation forced the larger larvae to increase the number of ingested prey (reaching >300 prey larva-1) to meet their energetic demands. In line with the observed shifts in diet, larvae showed an increase in δ13C and δ15N values throughout development. The trophic position estimates of the planktonic taxa shed light on the trophic structure of the planktonic community, identifying blue whiting larvae as a primary carnivore. Overall, the results suggest that blue whiting larvae feed efficiently in the Mediterranean trophic environment, This research was funded by project CTM2015-68543-R. J.M.-A.was supported by a predoctoral fellowship of the FI program of the Secretaria d’Universitats i Recerca de la Generalitat de Catalunya, Spain, and Fons Social Europeu (FSE) [2019FI_B2 00183]. J.N. was funded by the Spanish National Program Ramón y Cajal (RYC-2015-17809), Ministry of Science and Innovation, Spain. [...] This work acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S), Peer reviewed

12 pages, 5 figures, 2 tables, [EN] This study characterized the fishery dynamics of blue whiting, a bycatch species of the bottom trawl Norway lobster fishery, in the NW Mediterranean. Landings and effort data over the last two decades were combined with current information on the spatial distribution of effort and catch, and with the size and age structure of blue whiting over the year. Recruitment to the demersal habitat occurred from 5 cm total length (TL) over the shelf break in spring (April-May), when discards showed the highest values (>95% of the catch). Adults were located over the upper slope, and large individuals (≥26 cm TL) were abundant during the reproductive period (January-March). A decline in landings has been observed in the last decade, probably related to the absence of intense deep convection processes in winter since 2013, which favour recruitment of the species. The effect of exploitation on the decrease in landings cannot be disregarded considering that the bulk of the catch is made up of immature (age 0) individuals, and the presence of old individuals is very low, [ES] Para un enfoque ecosistémico en la gestión de las pesquerías, se requiere información actualizada sobre el estado de explotación de las especies acompañantes. El presente estudio caracteriza la dinámica de la pesquería de la bacaladilla en el Mediterráneo noroccidental, una especie acompañante de la pesquería de arrastre de la cigala. Los datos sobre la captura desembarcada y el esfuerzo pesquero de las últimas dos décadas se combinaron con información actual sobre la distribución espacial del esfuerzo pesquero y de la captura, y con la estructura de tallas y edades de la población de bacaladilla a lo largo del año El reclutamiento al hábitat demersal tuvo lugar a partir de los 5 cm TL en el margen de la plataforma continental en primavera (abril-mayo), cuando se detectaron los mayores valores de captura descartada (>95% de la captura). Los adultos se localizaron en el talud-superior y los individuos más grandes (>26 cm TL) fueron abundantes durante el periodo reproductivo (enero–marzo). Se observó un descenso en las capturas durante la última década, probablemente relacionada con la ausencia de episodios intensos de convección profunda en invierno desde el 2013, que favorecen el reclutamiento de la especie. Sin embargo, no se puede obviar el efecto de la explotación ya que la mayor parte de la captura se basa en individuos inmaduros (edad 0), This research was funded by project CTM2015-68543-R, Spain. J.M-A. was supported by a predoctoral fellowship of the FI programme of the Secretaria d’Universitats i Recerca de la Generalitat de Catalunya, Spain, and the European Social Fund (2019FI_B2 00183). Thanks are due to the Fisheries Service of the Generalitat de Catalunya for access to the fishing statistics. This work acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S), Peer reviewed

Este artículo contiene 13 páginas, 9 figuras, 4 tablas.-- Data availability: MUR data may be downloaded from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) at https://podaac.jpl.nasa.gov. MODIS data is available at NASA’s Ocean Color website at https://oceancolor.gsfc.nasa.gov/l3/. The data set on landings and effort (fishing days) over the period 2017–2019 were obtained from the fishing statistics of the Generalitat de Catalunya. Other data underlying this article were generated by the authors and will be shared on reasonable request to the corresponding authors., Fish recruitment variability results from a complex mix of biological and physical processes, and their interactions,
acting in the early life stages. In this study, we aim to investigate the environmental factors driving
the recruitment success of blue whiting (Micromesistius poutassou) in the NW Mediterranean through reconstruction
of early life history traits derived from otoliths microstructure analysis. To this purpose, the study
characterizes the oceanographic conditions in winter-spring of two contrasted years, 2017 and 2018, and relates
them to the onset and duration of the spawning, growth performance and condition of blue whiting recruits.
Winter 2017 was mild, with a short period of cold temperatures and limited winter vertical mixing. In winter
2018, temperatures reached lower values and extended for a longer period with intense vertical mixing and
dense water cascading down the continental slope at the end of February. These different conditions were
mirrored in the subsequent phytoplanktonic bloom, which in 2018 occurred later and was more intense than in
2017, extending over a longer period and occupying a wider area. The reproductive period of blue whiting was
linked to the duration of low winter temperatures (~13 ◦C), shorter in 2017 than in 2018 (~40 and ~ 60 days
respectively). While in 2017 all individuals were born in a relatively short period of time, and under similar
environmental conditions, in 2018 the hatching period presented two differentiated peaks, separated by a period
of relatively low hatchings at the end of February. This gap corresponded to dense water cascading and intense
vertical mixing events, suggesting that these phenomena limited the survival of eggs and larvae. The few individuals
hatched in this period showed the lowest growth rates (maximum values ~ 1.5 mm TL day􀀀 1), which
would be related with the poor trophic environment during these events of intense mixing. Conversely, in both
years, higher growth rates corresponded to the individuals born just before the phytoplankton bloom (attaining
~ 2 mm TL day􀀀 1). Recruits of 2018 showed better condition than those born the previous year which would be
associated with the higher primary production detected in spring 2018. The recruitment strength in 2018,
estimated from landings, was also much higher indicating that severe winter conditions translate into improved
recruitment of a temperate water fish in the NW Mediterranean Sea., This research was
funded by project [CTM2015-68543-R], Spain. We thank 3 anonymous
reviewers for their accurate and constructive comments. J.M-A. was
supported by a predoctoral fellowship of the FI program of the Secretaria
d’Universitats i Recerca de la Generalitat de Catalunya, Spain, and Fons
Social Europeu (FSE) [2019FI_B2 00183]., With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)., Peer reviewed

16 pages, 9 figures, 3 tables, supplementary data https://doi.org/10.1093/plankt/fbac056, This study investigates the role of winter oceanographic conditions on the horizontal and vertical spatial structure of Pyrosoma atlanticum at different ontogenetic stages. Data were obtained on two oceanographic cruises (February 2017 and 2018) in the NW Mediterranean. Small colonies were exceptionally abundant in 2017, linked to an earlier development of spring conditions and the subsequent seasonal phytoplankton bloom. The mesoscale distribution of P. atlanticum differed depending on the colony size. Large colonies (≥7 mm) were found on the slope all along the density front, whereas small (<4 mm) and medium colonies (4–6.9 mm) extended their distribution over the shelf because of instabilities of the front, and were mostly absent in the cold, low-salinity coastal waters. The analysis of their vertical distribution showed that at night colonies of all sizes remained close to the surface, where chlorophyll-a levels were high, whereas during the day they migrated to deeper layers, reaching greater depths as the colony size increased. The migratory behaviour started when colonies were 4–6.9 mm long. The relative importance of the species in the downward carbon transport is discussed. Our results highlight the need to further study the ecology of this efficient filter feeder in the Mediterranean, WINFISH project (CTM2015-68543-R) of the Spanish Ministry of Economy and Competitiveness and by a predoctoral fellowship from the Spanish Ministry of Education, Culture and Sport (FPU16/06794 to M.P.-P.). [...] This work acknowledges the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S), Peer reviewed

19 pages, 9 figures, 2 tables, supporting information https://doi.org/10.1111/fog.12661.-- Data Availability Statement: The data that support the findings of this study are available from the corresponding author upon reasonable request, Winter conditions in the NW Mediterranean cause instability of the water column and non-geostrophic dynamics, such as vertical mixing and convection are significant. These events involve nutrient supply to the photic zone that can sustain high productivity. In this study, we aim to investigate the role of winter hydrodynamics on the spawning strategies of Sardina pilchardus and Micromesistius poutassou. Data were obtained on two oceanographic cruises (February 2017 and 2018) off the Catalan coast. The occurrence of S. pilchardus eggs very close to the coast indicated a clear preference of the species for spawning in coastal areas. Preflexion and postflexion larvae exhibited a slightly wider distribution showing a clear association with the cold, less saline and more productive coastal waters. Preflexion larvae of M. poutassou were found on the upper slope and over the shelf, being offshore limited by the shelf/slope front present all along the slope. The front would act as a barrier preventing their dispersion towards the open sea. M. poutassou larvae in advanced developmental stages were located close to the coast in the productive shelf waters, with instabilities of the front contributing to larval transport from offshore waters to the coast. The vertical distribution of both species showed high variability, not only related with the daily cycle or developmental stage, but also with the vertical structure of the water column. Overall, the results provide some clues on how the spawning strategies of both species may evolve under future scenarios of higher winter-stratification, because of the global warming, This research was funded by the Spanish Ministry of Economy and Competitiveness (CTM2015-68543-R) and by the Spanish Ministry of Science and Innovation (PID2021-123457OB-C21). J.M-A. was supported by a predoctoral fellowship of the FI program of the Secretaria d'Universitats i Recerca de la Generalitat de Catalunya, Spain, and Fons Social Europeu (FSE) [2019FI_B2 00183]. [...] This work acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S), Peer reviewed

14 pages, 9 figures, 2 tables, supplementary material https://doi.org/10.1016/j.jmarsys.2024.103987.-- Data availability: Data will be made available on request, In the present study, we addressed the spatial characterization and species assemblages of the planktonic cnidarian community (Siphonophorae, Hydromedusae, and Scyphomedusae) in winter, a period that has been the subject of few studies in the NW Mediterranean. Data were obtained on two oceanographic cruises, in February 2017 and 2018. In 2017, the early onset of spring conditions and the subsequent phytoplankton bloom favored a mixture of winter and spring species, resulting in a higher species richness but a lower abundance of cnidarians. However, the typical winter oceanographic conditions in 2018 allowed winter species populations to develop, leading to a higher abundance of cnidarians that year. The most abundant species in both winters were Lensia subtilis, Muggiaea kochii, Chelophyes appendiculata, Abylopsis tetragona (eudoxid), Aglaura hemistoma, and Velella velella rataria larvae, while Obelia spp. was particularly numerous in 2017. In both years, the cluster and redundancy analyses showed a coastal-offshore ordination in species assemblages resulting from the effect of environmental variables (particularly bathymetry) and oceanographic structures (water masses and the shelf-slope density front). The presence of submarine canyons, in which great depths are reached close to the coast, modified the circulation patterns, resulting in a mixture of coastal and offshore species in these areas. In the current scenario of global warming, our results will help to provide a baseline for identifying future changes in the structure of the planktonic cnidarian community, This research was funded by the project WINFISH (CTM2015-68543-R), MP-P was supported by a predoctoral fellowship (FPU16/06794) from the Spanish Ministry of Education, Culture and Sport, and JM-A by a predoctoral fellowship of the FI program of the Secretaria d'Universitats i Recerca de la Generalitat de Catalunya (Spain) and Fons Social Europeu (FSE) (2019FI_B2 00183). This work acknowledges the “Severo Ochoa Centre of Excellence” accreditation (CEX2019-000928-S) and the support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI), Peer reviewed

18 pages, 12 figures, 4 tables.-- Data availability: Digital.CSIC https://doi.org/10.20350/digitalCSIC/17863, This study analyses the influence of the winter environmental conditions on the structure of larval fish assemblages off the Catalan coast (NW Mediterranean). Data were obtained during two oceanographic surveys (February 2017 and 2018) with contrasting environmental conditions. Winter 2017 was mild, the coastal zone was occupied by cold, low salinity and productive surface waters, and the water column was slightly stratified. Winter 2018 was more severe, temperatures were lower, with intense vertical mixing and deep-water formation and cascading events down the slope that enhanced shelf-slope water exchanges. Larvae of 52 fish taxa, both shelf and oceanic, were identified, with Sardina pilchardus being numerically dominant. Larvae of shelf fish species were more abundant in 2017 associated with the productive coastal waters. Larvae of oceanic species were more abundant in 2018, with a wide distribution all over the area that would be related to the vertical mixing and the shelf-slope exchange processes that year. Accordingly, the distribution of fish larvae in the water column was wider and deeper in 2018 than in 2017. The assemblages identified by the cluster analysis were determined by bottom depth, sea surface temperature and sea surface chlorophyll-a, with dynamic height being the main factor explaining the differences in assemblages between years. These differences highlighted the role of the shelf-slope water exchange processes in 2018, mainly in the submarine canyons. The results shed light on how changes in larval fish assemblages are indicators of shifts in environmental conditions. Under a climate change scenario, it is likely that the decrease in the fertilisation processes, such as deep-water formation (by convection or cascading) and vertical mixing, would have adverse effects on larval fish populations, This work was supported by the Spanish Ministry of Economy and Competitiveness (CTM2015-68543-R) and by the grant (PID2021-123457OB-C21) funded by MICIU/AEI/10.13039/501100011033 and ERDF/EU. J. M-A. was supported by a predoctoral fellowship of the FI program of the Secretaria d'Universitats i Recerca de la Generalitat de Catalunya, Spain, and Fons Social Europeu (FSE) [2019FI_B2 00183]. This work acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S), Peer reviewed

13 pages, 11 figures, 3 tables, supplementary data https://doi.org/10.1016/j.marenvres.2025.107396.-- Data availability: Data will be made available on request, Sardina pilchardus population in the NW Mediterranean Sea has experienced an important decline in biomass in the last decades. In the Gulf of Lions, a shift in growth performance in 2008 led to the collapse of the sardine fishery that persists today. While several hypotheses have been proposed, their basis remain unclear. This study investigates the influence of key environmental factors (sea surface temperature and primary production) along with biological traits (size and age at first maturity, spawning period and body condition) on sardine growth.
Firstly, we analyse the growth performance of sardines collected monthly during 2017 and 2018 in two close areas (90 km apart), with distinct temperature conditions. Growth differences were observed that would be linked to temperature. The higher temperature in the South would favour faster juvenile growth, resulting in larger sizes-at-age 1 and older classes. Biological traits were similar between areas, therefore, would not explain the observed differences in growth performance.
Secondly, this study examines temperature and chlorophyll-a trends (2002–2022) to provide insight into the ongoing NW Mediterranean sardine crisis. A temperature shift identified in 2007 would explain the reported changes in growth in 2008. Additionally, differences in the phenology of the phytoplankton growing period between areas were identified. The North area is experiencing an earlier onset of oligotrophic conditions, which would result in a reduction of food availability for sardine juveniles in the spring-summer growing period, which would be an additional stressor for sardines in the North area, This research was funded by project [CTM2015-68543-R], Spain. Thanks are due to the Fisheries Service of the Generalitat de Catalunya for providing access to the fishing statistics. This work acknowledges the Severo Ochoa Centre of Excellence Accreditation [CEX2024-001494-S funded by AEI 10.13039/501100011033], Peer reviewed

17 pages, 13 figures, 1 table, supplementary material https://www.frontiersin.org/articles/10.3389/fmars.2026.1760679/full#supplementary-material.-- Data availability statement: The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found below: Digital.CSIC repository https://doi.org/10.20350/digitalCSIC/17768, This work investigates the main changes undergone by the summer larval fish community over three decades along the Catalan coast, an area characterized by a wide array of environmental conditions. The study was based on nine ichthyoplankton surveys carried out in June, July and September in three decades, 1980s, 2000s and 2010s, covering the same area and applying the same sampling methodology. Throughout the study period, an increase in sea surface temperature, particularly marked in June, and a decrease in surface chlorophyll-a associated with a decline in runoff from the Ebro and Rhone rivers was observed. Marked changes in the composition and abundance of the larval fish community were detected between June and July in the 1980s and the following decades. These changes were mainly due to the presence for the first time in the area of warm-water species, such as Thalassoma pavo and Caranx rhonchus, or to the increase in their abundance, such as Sardinella aurita and Pomatomus saltatrix, in the 2000s in relation to the northward expansion of the adults‘ range. The presence of larvae of warm-water species in the 2000s and 2010s contributed to an increase in specific richness of the larval fish community compared to values obtained in the 1980s. Other species showed a decline in abundance over time, probably due to a decrease in surface chlorophyll-a, e.g. Engraulis encrasicolus, although overexploitation is also an important factor to consider. Larvae of other species, such as coastal and mesopelagic fishes, did not show changes in abundance over the three decades. In a future scenario of increasing sea water temperature and marine heatwaves events, enhanced stratification, and decreasing surface primary production, the changes that may occur in the fish larvae community will largely depend on the adaptive responses of individual species to the new environmental conditions, This work was supported by the projects REN 2002-01339/MAR, MAR-CTM2010-18874, and CTM2015-68543-R, funded by Spanish Ministry of Economy and Competitiveness. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative (PROA) through its Unit of Information Resources for Research (URICI). This work acknowledges the “Severo Ochoa Centre of Excellence” accreditation (CEX2024-001494-S) funded by AEI 10.13039/501100011033, Peer reviewed

Pelagia noctiluca is the most common jellyfish in the Western Mediterranean Sea, living in
oceanic waters with a holoplanktonic lifecycle. Frequent outbreaks have been well documented in coastal areas, yet little is known about their offshore distribution. In this study we
address the relationship between oceanographic structures and the distribution of P. noctiluca ephyrae along the central continental slope of the Western Mediterranean, covering a
wide latitudinal gradient, during July-August 2016. The region is characterized by a rich and
complex mesoscale surface circulation driven by the inflow of Atlantic Water into the Western Mediterranean through the Strait of Gibraltar. The results revealed a high variability in
the ephyrae spatial paterns related with different water masses and the resulting mesoscale
hydrographic features. Their horizontal distribution showed a clear latitudinal gradient with
high abundances in the south, associated with recent Atlantic Water, and low abundances
or absence in the north, in coincidence with the old Atlantic Water transported by the Northern Current. Ephyrae showed diel vertical migrations of short-extent in the first 50 m, with a
wide distribution above the thermocline and the Deep Chlorophyll Maximum during daytime,
being more concentrated towards the surface at night. The results suggest the population
connectivity of P. noctiluca between the Atlantic and the Mediterranean. In that case, the
abundance variability of the species in the Mediterranean could be modulated by its
entrance associated with the inflow of Atlantic Water through the Strait of Gibraltar., This research was supported by the projects CONECTA (CTM2014-54648-C2-1-R) and WINFISH (CTM2015-68543-R) funded by the Spanish Ministry of Economy and Competitiveness. MP-P and MC were supported by a predoctoral fellowship (FPU16/06794 and FPU2015/04339, respectively) from the Spanish Ministry of Education, Culture and Sport. The publication fee was partially supported by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).