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Nursery areas are essential fish habitats due to their relevance in the survival of early stages of fish populations. They are also considered as of high priority in marine conservation strategies. Here, we investigated the diet of white seabream [Diplodussargus (Linnaeus, 1758)] settlers in six nursery areas located in the shallow waters of coves in Minorca Island (Balearic Islands, Spain). Our aim was to characterize the food sources at different stages of juvenile development and their site-related variability in order to discern the importance of trophic links in cove selection during settling. The gut contents of 101 juveniles captured at different coves, three to the north of the island (N), and three in the southern coast (S), revealed a marked preference for feeding on crustaceans and, in particular, on harpacticoid copepods (>90% of gut contents). Copepods represented the main food source (80 ±4.4%; mean ±S.E.) in younger seabream individuals (10 - 15 mm length). A higher diversity in prey items was observed in the larger size-classes (s2: 16 - 23 and S3: 24 - 30 mm, respectively), which incorporated other prey items such as amphipods, isopods, foraminiferans or ostracods. Diet composition did not vary between the two surveyed locations (North vs. South of the island), but it did show significant differences among the six coves (p

The diversity of benthic communities on continental shelves is tightly linked to the diversity of habitats. Therefore, considering seascape habitat composition can help to gain insights into the spatial variability of benthic communities and move away from single-habitats approaches. This perspective needs different analytical methods, such as network analysis that enable the study of complex ecological interactions. This work explores the relationships between habitat and benthic species diversity in the Menorca Channel (the Balearic Islands, western Mediterranean). The seascape in the study area is a mosaic of alternating biogenic and sandy habitats that increases the total benthic species richness. Of the 442 benthic species included in the analyses, 286 species are shared by the six habitats identified, contributing to ecological connectivity across the seascape; 73 generalist species inhabit all six habitats simultaneously, however, 156 species are specialists and are linked to a single habitat, particularly to biogenic habitats, which increases specialization and the vulnerability of the species to habitat fragmentation. The network approach shows a tight link between epibenthic species diversity and the distribution of habitats over the continental shelf, providing essential information for optimal conservation strategies that move from a focus on protecting the most sensitive habitats to marine conservation schemes that encompass a diversity of habitats. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work was funded by EU H2020 MaCoBioS (Grant Number 869710) and the original data was produced under LIFE + INDEMARES project: ‘‘Inventario y designación de la Red Natura 2000 en área marinas del Estado español’’. SdJ is supported by a Ramon y Cajal postdoctoral grant funded by the Ministry of Science and Innovation (Plan Estatal I + D + I, 2017- 2020; grant no. RyC2020-029062-I). AO was funded by the General Directorate for University Policy and Research of the Government of the Balearic Islands with a “Vicenç Mut” award Grant PD/002/2020. JM was the INDEMARES project coordinator in the Menorca Channel for the period 2009–2014.

Here, we assess whether fishery exploitation affects the trophic structure of carnivorous fish. We censused fish and analysed the stable isotope ratios of C and N of species targeted by fishermen in areas open to fishing and marine protected areas (MPAs) in the Mediterranean Sea and the north-eastern Atlantic Ocean. Results demonstrated a major impact of fishing on the biomass and size structure of nektobenthic carnivorous fish. However, those changes did not modify the diversity of the trophic resources used by the assemblage, the pattern of resource partitioning between species, or the degree of trophic redundancy. These results add to recent evidence suggesting that MPAs implemented in fished seascapes may fail to restore the original structure of the food webs that once existed in pre-fished ecosystems because regional decimation and extinction of highly mobile predators prevent recovering the original diversity of predators at local scales, even in no-take areas. If so, more strict local fishing regulations are unlikely to restore the original diversity of high trophic level carnivores and restoration goals should be reframed in terms of an objective that is less unrealistic than restoring the pre-fished condition while still recovering aspects of the historical trophic structure.

The unlimited economic growth that fuels capitalism's metabolism has profoundly transformed a large portion of Earth. The resulting environmental destruction has led to an unprecedented rate of biodiversity loss. Following large-scale losses of habitats and species, it was recognized that biodiversity is crucial to maintaining functional ecosystems. We sought to continue the debate on the contradictions between economic growth and biodiversity in the conservation science literature and thus invite scholars to engage in reversing the biodiversity crisis through acknowledging the impacts of economic growth. In the 1970s, a global agenda was set to develop different milestones related to sustainable development, including green-blue economic growth, which despite not specifically addressing biodiversity reinforced the idea that economic development based on profit is compatible with the planet's ecology. Only after biodiversity loss captured the attention of environmental sciences researchers in the early 2000s was a global biodiversity agenda implemented. The agenda highlights biodiversity conservation as a major international challenge and recognizes that the main drivers of biodiversity loss derive from economic activities. The post-2000 biodiversity agendas, including the 2030 Agenda for Sustainable Development and the post-2020 Convention on Biological Diversity Global Strategy Framework, do not consider the negative impacts of growth-oriented strategies on biodiversity. As a result, global biodiversity conservation priorities are governed by the economic value of biodiversity and its assumed contribution to people's welfare. A large body of empirical evidence shows that unlimited economic growth is the main driver of biodiversity loss in the Anthropocene; thus, we strongly argue for sustainable degrowth and a fundamental shift in societal values. An equitable downscaling of the physical economy can improve ecological conditions, thus reducing biodiversity loss and consequently enhancing human well-being., I.M. carried out the research under the framework of the RTI2018-094844-B-C31 research project.

Resource partitioning in polymorphic fish species is expected to be altered by human exploitation, as individual specialization is density dependent in many vertebrates. We tested this hypothesis using the ballan wrasseLabrus bergyltaas a model species. We compared the isotope niches of the plain and spotted morphs of the species in a marine protected area (MPA) and in adjoining areas open to fishing, both off Galicia (NW Spain). Underwater visual census confirmed a 3-fold increase in the biomass of ballan wrasse off the Cíes Islands compared to areas open to recreational fishing, thus demonstrating that populations outside MPAs are well below carrying capacity. The stable isotope ratio of C revealed differences in the resource use patterns of plain and spotted ballan wrasses both in areas open and closed to fishing, as plain wrasses were always depleted in13C compared to sympatric spotted ones. The stable isotope ratio of N showed that plain ballan wrasses foraged consistently at a higher trophic level than spotted ones in areas of high population density closed to recreational fishing, whereas differences did not exist or were reversed in areas open to fishing. These results demonstrate that the pattern of trophic resource partitioning between 2 morphs of the ballan wrasse is density dependent and that plain and spotted ballan wrasses likely had different ecological niches in pristine ecosystems.

Trabajo presentado al 9th International Symposium Monitoring of Mediterranean Coastal Areas: "Problems and Measurement Techniques", celebrado en Livorno (Italia) entre el 14 y el 16 de junio de 2022., Temperate coastal ecosystems dominated by macrophytes are diverse, ranging from macroalgal forests to seagrass meadows. They provide numerous ecosystem services and are highly valuable as nursery areas for fish. However, these habitats are under increasing pressure due to anthropogenic actions. In the last decades, the use of Diver Operated Stereo-Video (stereo-DOV) systems has become popular for making accurate, precise, and repeatable measurements of fish lengths. The objective of our study is to develop an efficient video-based methodology for studying the patterns of recruitment of temperate littoral fishes at various temporal and spatial scales. We aim to evaluate our methodology compared to other non-invasive techniques used for the study of juvenile fish assemblages. In this paper, we propose a combination of habitat mapping and stereo-DOV transect methodologies and test them in two case studies to investigate the link between juvenile fish and macrophytes, considering various scales of heterogeneity of littoral habitats. Data on species composition, abundance, and mean total length of the juvenile assemblages and canopy height from each habitat can be obtained and geo-referenced in the sampling sites, mapping their distribution in space and time to understand recruitment patterns. Some benefits of using stereo-DOV transects and habitat mapping for monitoring fish assemblages in comparison with traditional non-invasive methods used for fish counts, are a) videos are permanent, they can be reanalyzed; b) divers do not have to be experts in fish and macrophyte identification; c) inter-observer variability can be controlled through quality checks; d) high accuracy and precision in fish count and length measurements; and e) image data can be used for developments of artificial intelligence (AI). However, there are also some disadvantages: a) cameras have a limited field of view; b) video processing is time-consuming; and c) experts are needed for fish identification during image processing. In conclusion, the combination of stereo-DOV and habitat mapping is an effective methodology for monitoring fish recruitment patterns and habitats at different scales. It can be also advantageous for evaluating temporal changes in the habitat structure, and therefore, in the ecosystem functions provided for the fish community.

Explaining the mechanisms driving niche partitioning among species is of great importance in ecology. Unlike the fundamental niche, a species' realised niche can only be measured in situ, as a result of biotic and abiotic interactions defining its size. Following current methodology, the realised niche of a species is often influenced by the rare and divergent individuals of the community sampled. In this study, using fish on coral and temperate reefs as an example, behavioural empirical data were collected to estimate realised niche sizes and niche overlaps. Niche measurements were made using the total area of the convex hull (TA), but as an alternative, a metric not as strongly influenced by sample size, standard ellipse area (SEA), was also used. A comprehensive description is given, and contextdependent pros and cons of using both metrics are discussed. Additionally, an alternative sample size correction was presented for both metrics. The analyses re vealed large differences in the sizes of realised niches and their overlaps between species depending on the measurement metric used. Regardless of the species, niche size and overlap were always larger for TA than SEA. Increasing sample size re - duced niche size variability for both TA and SEA, but the variation was always smaller for SEA than TA. We successfully adapted the SEA metric for analysis of behavioural niche components and demonstrated that measuring niche sizes using the 2 metrics, each with their own strengths and weaknesses, can produce contradictory results, the ecological consequences of which are likely to be important.

In recent years, overtourism and tourism gentrification have been a central feature of public debate in the Balearic Islands, one of the most touristified regions on the planet. In this con...

The sublittoral forests formed by the fucoid algae Cystoseira spp. are important juvenile habitats for many Mediterranean fish species. However, the spatial variability of juvenile fish assemblages within the forests and the potential environmental drivers, such as depth and habitat complexity, remain poorly understood. We estimated densities, sizes and behaviours of juvenile fish assemblages in subtidal (0-15 meters) Cystoseira brachycarpa var. balearica forests in north Minorca Island (North-western Mediterranean Sea) over two consecutive autumns (2012 and 2013). Depth and forest complexity, here measured as canopy volume, had both a significant and independent effect on the juvenile fish assemblages in terms of species abundance composition and body size. Assemblages found in the shallowest depth range (3-4m) were characterized by greater densities of the ornate wrasse Thalassoma pavo, while those deeper (10-12m) had higher densities of the rainbow wrasse Coris julis , independently of its size composition. Juveniles of both species were more abundant in less complex forests; conversely juveniles of wrasses of the genus Symphodus were more abundant in more complex forests. The smallest sizes of T. pavo occurred in the most complex forests. On the other hand, our results demonstrated that juvenile fish behaviours were unrelated to the complexity of the Cystoseira forests but mainly related to the body length. The effects of body length on behaviour were however species dependent. Cryptic and transitory behaviours were mostly observed in the smallest and largest juveniles of T. pavo and C. julis , respectively, while the behaviour of Symphodus spp. was unrelated to their body length. Our study emphasises the importance of preserving healthy Cystoseira forests and their intrinsic patchy nature, as this habitat, with its mosaic of different complexity degrees and bathymetrical variability, enable the presence of different fish species at various life stages.

The nursery function of coastal habitats is one of the most frequently mentioned and recognized ecosystem services in the valuation of coastal ecosystems. Despite its importance our understanding of the precise habitat parameters and mechanisms that make a habitat important as a nursery area is still limited for many species. The study aimed to establish the importance of different algae morphotypes in providing shelter and food for juvenile coastal fish during the main settlement peaks in early spring and late summer in littoral rocky reef systems in the Northwestern Mediterranean. The results of our study showed strong seasonal differences in algae cover, composition and height between the two sampling periods. Overall, during spring the algae were well developed, while in late summer, both density and height, of most algae decreased considerably. Equally, prey biomass, in form of suitable sized invertebrate fauna associated to the algae, decreased. Accordingly, the shelter and food for the fish settling in this habitat during late summer were less abundant, indicating a mismatch between the observed presence of juvenile fish and optimal habitat conditions. Differences in prey densities were detected between algae morphotypes, with structurally more complex algae, such as Cystoseira spp. and Halopteris spp consistently contain more prey independent of season compared to simpler structured morphotypes such as many Dictoytales. The study furthermore related juvenile fish density to habitats dominated by different algae morphotypes. Out of the three-study species (Diplodus vulgaris, Symphodus ocellatus, Coris julis) only S. ocellatus showed a significant association with an algae habitat. S. ocellatus related positively to habitats dominated by Dictoytales which provided the highest cover during late summer but had the lowest prey densities. A strong association of this species with Cystoseira as reported by other studies could not be confirmed. Cystoseira was abundant within the study area but in a state of dieback showing loss and reduced height of foliage, typical for the time of year within the study area. It is therefore likely that algae-fish associations are context dependent and that several algae species may fulfil similar functions. We also discovered that prey biomass did not appear to have an important effect on juvenile abundances. Nevertheless, the availability of prey may influence juvenile fish condition, growth performance and ultimately long-term survival. We therefore suggest that future studies on habitat quality should also include, besides abundance, indicators related to the condition and growth of juveniles.

Two-current choice flumes are used to measure preference and avoidance behaviour in response to chemical cues in aquatic animals. If used correctly, they produce two parallel, non-overlapping, laminar water currents in which the animal can move freely and choose between the two currents. As climate change is affecting water temperature, and altered precipitation patterns are changing water salinity, two-current choice flumes are increasingly being used to test the choice between water currents of different temperatures and salinities. This inevitably means that water currents of different densities are being used simultaneously in the flume. Here, we investigated the tolerance range for density differences due to temperature and salinity in five common flume designs. Through dye tests and stepwise modifications of temperatures and salinities we determined the limits for laminar and non-overlapping flows. We also developed an automated method for quantifying the overlap precisely and objectively. The tolerance for density differences between the water currents where laminar and non-overlapping flows were maintained was surprisingly low, withstanding ± 0.5 °C temperature differences, and ± 0.1 PSU salinity differences, i.e. a maximum density difference of 0.28 gL. Above these very narrow limits we found a range where the flumes showed partly overlapping, stratified water currents that preclude easy determination of cue preference. We conclude that two-current choice flumes are not suitable for testing the behavioural choices of aquatic animals using water currents of anything other than minor differences in temperature and/or salinity., This work was funded by the Swedish Research Council Formas (JS: 2013-947, FJ: 2009-596) and The Research Council of Norway (FJ: 262942).

Using rainbow wrasse as a model species, we evaluate the impact of protection on the relationship between body size and: i) trophic position (TP), based on δ15N; and ii) body condition (BC), based on weight-at-length. We found that the biomass of the rainbow wrasse, their predators and their competitors was higher inside the no-take marine protected area (NTA) than in the area open to fishing. The TP of rainbow wrasse was higher inside the NTA but the BC was lower. A domed relationship between TP and size was observed in both areas: the TP increased with size up to 12.6 cm total length, when all individuals shifted to terminal males, and then decreased. Although other confounding environmental variables may exist, the indirect effects of fishing on competition and predation risk are the most likely explanation for the changes in TP, BC and the ontogenetic dietary shift of the rainbow wrasse.

Bottom trawling can change food availability for benthivorous demersal species by (i) changing benthic prey composition through physical seabed impacts and (ii) by removing overall benthic consumer biomass increasing the net availability of benthic prey for remaining individuals. Thus trawling may both negatively and positively influence the quantity and quality of food available. Using δ13C and δ15N we investigated potential diet changes of three commercially exploited species across trawling gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and the Irish Sea (Nephrops). In the Kattegat, trawling affected primarily the biomass of benthic consumers, lowering competition. Nephrops showed significant positive relationships for δ13C and a domed relationship for δ15N with trawling. In the Irish Sea, intense trawling had a negative effect on benthic prey. δ13C and δ15N thus showed the inverse relationships to those observed in the Kattegat. Plaice from the Kattegat, showed a significant relationship with trawling intensity for δ13C, but not for δ15N. No relationship was found for dab. Changes of δ13C and δ15N correlated with changes in condition of species. The results show that the removal of demersal competitors and benthos by trawling can change the diets of commercial species, ultimately affecting their body condition, SI

The role of the meadows of the Mediterranean seagrass Cymodocea nodosa as nursery habitats for fish remains largely unknown and there are only few studies investigating the influence of their structure on juvenile assemblages. Here, we monitored juvenile fish assemblages among shallow Cymodocea nodosa meadows (0–1 m) in Minorca Island (north-western Mediterranean Sea) in both July and September 2013. To assess the influence of structural components on juvenile fish assemblages, we selected two different meadow structure types: heterogeneous with intermingled boulders and homogeneous meadows, i.e. without boulders. Juvenile fish assemblages varied significantly among these two meadow structures. Heterogeneous meadows had higher total juvenile density and species richness, where some species were only found in these portions, such as Coris julis and Serranus spp. Other species, such as Symphodus spp. and Sarpa salpa, were also more abundant within heterogeneous meadows. However, densities of some species were not increased in heterogeneous meadows demonstrating a specific response to habitat structure. For instance, Diplodus annularis displayed similar abundances in both heterogeneous and homogeneous portions of the meadow. Our study reveals that the intrinsic structural variability of seagrass meadows plays a key role for the assemblage of several fish species that are characterized by different early life history strategies, SI

In order to recruit into adult populations juvenile fish must be able to find food, successfully compete with other organisms and avoid predation within a habitat, in other words they must be able to locate favourable and avoid detrimental conditions. Bio-chemical research into fish detection and discrimination between chemical cues is extensive, however whether olfactory mechanisms are critical in habitat selection and avoidance of detrimental conditions within the marine environment remains under-researched. Despite being one of the scientifically most explored seas, studies on the use of olfactory system in the selection of water masses of the Mediterranean fish species are absent. Using a chemical choice flume, the chemically mediated behaviour choices to distinct chemical cues (algae, seagrass, predator and conspecifics) of Symphodus ocellatus, a common Mediterranean fish, were investigated. In addition to the conventional analysis, which relies on the amount of the time spent in the specific water mass as the main indicator of preference, the behavioural response triggered by the detection of a particular cue was also examined, by analysing the mean and variance of speed of the individual fish movements, a complimentary approach previously not considered in the flume experiments. Bayesian statistical method was used to calculate both, proportion of time spent in the specific water mass, as well as to analyse the behavioural response of each individual within the specific water mass. In terms of the time spent, the flume trials conducted resulted in no significant fish selection preference or avoidance for any of the water masses tested, however varied speeds and number of burst speed movements were observed in a number of trials. When no olfactory stimulus was present, no change in behaviour was triggered. Thus, juvenile S. ocellatus undoubtedly has a capacity of change in behaviour to a complex array of olfactory stimuli, nevertheless the response in the flume experiment was more complex than just the differences in time of the occupancy between the water masses. As a result, the analyses of speed could in future prove to be an important complementary tool for studying behavioural responses of fish using this methodology. The findings are coupled with the development of the rigorous novel protocol for behavioural analyses using exclusively publicly available apparatus and software, all described within the manuscript, SI

Concern has increased in recent decades regarding processes influencing fish juvenile density distributions; indeed, juveniles determine the replenishment of populations and their habitats are often found in shallow coastal areas, where human impacts are concentrated. We aimed to measure the relative importance of seascape attributes at various spatial scales (from seascape to microhabitat) in fish settlement and post-settlement processes. Along the coast of Minorca Island (NW Mediterranean), Diplodus sargus settlement variability was higher among the southern coast compared to the variability in the northern one. Independently of coast location, sheltered nurseries presented lower settlement intensity and recruitment levels compared to exposed ones. Such patterns suggested differential larval supply according to exposure level. Furthermore, subsequent density-dependent post-settlement mortality reduced the cove-specific variability of initial settlement. In addition, inside each cove, juveniles displayed ontogenetic changes of microhabitat use: smaller juveniles were more abundant in the most heterogeneous microhabitat. Consequently, juvenile density distributions responded to seascape attributes at different spatial scales; this suggests that both lager scale attributes and microhabitat influence both settlement and post-settlement processes, and may be limiting for recruitment. Our study demonstrated the importance of a diversified seascape to promote fish population replenishment, SI

This short-term study on commercial discards was carried out in fishing grounds around Gökçeada Island in the northeastern Aegean Sea, a geographic area where fisheries information is rather limited. A total of 28 bottom trawls were performed between 70 and 410 m depth from December 2009 to February 2010. All the samples were collected on board a commercial trawler under commercial fishing conditions. A total of 3143 kg of biomass was caught in 28 valid hauls. Landings accounted for about 67% of the total catch while the remaining 33% was discarded. Fish species comprised 85% of the total catch and their composition could be divided into four main groups related to depth: shallow shelf (70 to 88 m), deep shelf (155 to 180 m), shelf break (196 to 276 m), and upper slope (307 to 410 m). Fish dominated the abundance and biomass of both landings and discards in all bathymetric strata. Echinoderms also accounted for a large proportion of the discards. Mean total catches varied between 78.4 kg/h on the shallow shelf and 38.1 kg/h on the shelf break with no differences in the landing biomass between groups, but with slightly higher discards over the shallow shelf. Taking into account the preliminary nature of the findings, based on a short-term analysis, the minimum mesh size and minimum landing size currently applied in the Turkish bottom trawl fishery are not sufficient to reduce discards and to protect juveniles of commercially important species in the northeastern Aegean Sea. Este estudio a corto plazo sobre los descartes de la flota comercial de arrastre se llevó a cabo en las zonas de pesca alrededor de la isla Gökçeada en el noreste del mar Egeo, una zona geográfica en la que la información sobre las pesquerías es bastante limitada. Se realizaron un total de 28 pescas de arrastre de fondo entre 70 y 410 m de profundidad de diciembre 2009 a febrero de 2010. Todas las muestras se recogieron a bordo de un embarcación de pesca de arrastre siguiendo las mismas condiciones de pesca comercial. Se capturaron un total de 3143 kg de biomasa en 28 lances válidos. Los desembarques comerciales representaron alrededor del 67% de la captura total, mientras que el resto (33%) se descartó. El 85% de la captura total estuvo compuesta por especies de peces. La composición específica se pudo separar en cuatro grupos principales relacionados con la profundidad : la plataforma poco profunda (70 a 88 m), la plataforma profunda (155-180 m), el borde inferior de la plataforma (196 a 276 m) y el talud superior (307-410 m). Los peces dominaron la abundancia y biomasa tanto de los desembarques comerciales como de los descartes en todos los estratos batimétricos. Además los equinodermos también fueron un grupo importante de los descartes. La media de las capturas totales varió entre 78.4 kg/h en la plataforma poco profunda y 38.1 kg/h en el borde de la plataforma, sin diferencias en la biomasa desembarcada entre los dos grupos, pero siendo los descartes ligeramente superiores en la plataforma poco profunda. Teniendo en cuenta el carácter preliminar de los resultados, obtenidos sobre la base de un análisis a corto plazo, el tamaño mínimo de malla de la red y la talla mínima de las especies comerciales aplicada hoy en día en la pesquería de arrastre de fondo de Turquía no son suficientes para reducir los descartes y proteger a los juveniles de las especies de importancia comercial en el Mar Egeo nororiental.

Coral reefs are threatened by numerous global and local stressors. In the face of predicted large-scale coral degradation over the coming decades, the importance of long-term monitoring of stress-induced ecosystem changes has been widely recognised. In areas where sustained funding is unavailable, citizen science monitoring has the potential to be a powerful alternative to conventional monitoring programmes. In this study we used data collected by volunteers in Southeast Sulawesi (Indonesia), to demonstrate the potential of marine citizen science programmes to provide scientifically sound information necessary for detecting ecosystem changes in areas where no alternative data are available. Data were collected annually between 2002 and 2012 and consisted of percent benthic biotic and abiotic cover and fish counts. Analyses revealed long-term coral reef ecosystem change. We observed a continuous decline of hard coral, which in turn had a significant effect on the associated fishes, at community, family and species levels. We provide evidence of the importance of marine citizen science programmes in detecting long-term ecosystem change as an effective way of delivering conservation data to local government and national agencies. This is particularly true for areas where funding for monitoring is unavailable, resulting in an absence of ecological data. For citizen science data to contribute to ecological monitoring and local decision-making, the data collection protocols need to adhere to sound scientific standards, and protocols for data evaluation need to be available to local stakeholders. Here, we describe the monitoring design, data treatment and statistical analyses to be used as potential guidelines in future marine citizen science projects.

A variety of sedimentary bedforms have been identified on the continental shelf between Mallorca and Menorca (Menorca Channel). The bedforms consist of different grain sizes, ranging from very fine to coarse, predominantly bioclastic sands, and include rippled scour depressions in association with fine sand patches, sand waves, sand ridges, ribbons and furrows. The morphology and acoustic appearance of these bedforms are documented in a number of maps generated on the basis of detailed multibeam bathymetric datasets, side-scan sonar images and high-resolution reflection seismic profiles (TOPAS)., Instituto Geológico y Minero de España, España, Instituto Español de Oceanografía, España, TRAGSA, España, Centre Oceanogràfic de les Balears, Instituto Español de Oceanografía, España, TECMARIN 1990, España

International audience; In Mediterranean subtidal rocky reefs, Cystoseira spp. (Phaeophyceae) form dense canopies up to 1 m high. Such habitats, called ‘Cystoseira forests’, are regressing across the entire Mediterranean Sea due to multiple anthropogenic stressors, as are other large brown algae forests worldwide. Cystoseira forests are being replaced by structurally less complex habitats, but little information is available regarding the potential difference in the structure and composition of fish assemblages between these habitats. To fill this void, we compared necto-benthic (NB) and crypto-benthic (CB) fish assemblage structures between Cystoseira forests and two habitats usually replacing the forests (turf and barren), in two sampling regions (Corsica and Menorca). We sampled NB fish using Underwater Visual Census (UVC) and CB fish using Enclosed Anaesthetic Station Vacuuming (EASV), since UVC is known to underestimate the diversity and density of the ‘hard to spot’ CB fish. We found that both taxonomic diversity and total density of NB and CB fish were highest in Cystoseira forests and lowest in barrens, while turfs, that could be sampled only at Menorca, showed intermediate values. Conversely, total biomass of NB and CB fish did not differ between habitats because the larger average size of fish in barrens (and turfs) compensated for their lower densities. The NB families Labridae and Serranidae, and the CB families Blenniidae, Cliniidae, Gobiidae, Trypterigiidae and Scorpaenidae, were more abundant in forests. The NB taxa Diplodus spp. and Thalassoma pavo were more abundant in barrens. Our study highlights the importance of using EASV for sampling CB fish, and shows that Cystoseira forests support rich and diversified fish assemblages. This evidence suggests that the ongoing loss of Cystoseira forests may impair coastal fish assemblages and related goods and services to humans, and stresses the need to implement strategies for the successful conservation and/or recovery of marine forests.

Accumulating evidence shows that fishing exploitation and environmental variables can synergistically affect the population dynamics of exploited populations. Here, we document an interaction between fishing impact and climate variability that triggered a synchronic response in the population fluctuations of six exploited species in the Mediterranean from 1965–2008. Throughout this period, the fishing activity experienced a sharp increase in fishing effort, which caused all stocks to shift from an early period of underexploitation to a later period of overexploitation. This change altered the population resilience of the stocks and brought about an increase in the sensitivity of its dynamics to climate variability. Landings increased exponentially when underexploited but displayed an oscillatory behaviour once overexploited. Climatic indices, related to the Mediterranean mesoscale hydrography and large-scale north Atlantic climatic variability, seemed to affect the species with broader age structure and longer lifespan, while the global-scale El Niño Southern Oscillation index (ENSO) positively influenced the population abundances of species with a narrow age structure and short lifespan. The species affected by ENSO preferentially inhabit the continental shelf, suggesting that Mediterranean shelf ecosystems are sensitive to the hydroclimatic variability linked to global climate. (Oxford University Press)

28 pages, 6 figures, 6 tables, supplementary material in https://doi.org/10.1007/s10531-011-0210-1, Menorca Channel (Balearic Islands, western Mediterranean) comprises 98,700 Ha of continental shelf. It has been proposed to include this area in the Natura 2000 network due to the wide range of species and habitats of high conservation value found here, such as Posidonia oceanica meadows and maërl and coralligenous beds. This study aimed to establish a scientific basis for managing and protecting the continental shelf bottoms in Menorca Channel. Sampling was carried out with side-scan sonar, beam trawls, box corers, a remote-operated vehicle and an underwater drop camera. The information collected was used to map the habitat distribution between 50 and 100 m depth, as well as make an inventory and describe the spatial patterns of both the specific and functional diversity. A total of 636 species was recorded in a mosaic of habitats in which Corallinacea calcareous algae and other soft red algae (Osmundaria volubilis and Peyssonnelia spp.) were the most abundant groups. Hotspots of specific and functional diversity were located in areas with high habitat heterogeneity and complexity. Protection of Menorca Channel should not only include the habitats and species in the European directives, but also the habitats that are not currently protected, such as O. volubilis and Peyssonnelia beds, due to their biogeographical and ecological interest and their contribution to the biodiversity of shelf bottoms in the Mediterranean Sea. © 2012 Springer Science+Business Media B.V., The study was financed by the Conselleria d’Agricultura i Pesca of the Government of the Balearic Islands within the Canal Project and in the framework of LIFE+ INDEMARES project: ‘‘Inventario y designación de la Red Natura 2000 en áreas marinas del Estado español’’. Sonography was carried out by Tecmarin 1990 SL and financed by the MarViva Foundation

Many demersal fish species rely on benthic prey as food sources for part of, or in some cases, all of their life his- tory. We investigated the relationships between prey and predator abundance and prey size and predator mouth gape size for nine demersal fish species. Of the species analysed, four showed a significant positive increase in abundance with increasing prey abundance. Prey size is thought to be an important parameter for demersal fish that are limited in their feeding poten- tial by their mouth gape size, as it influences consumption rate and energy expenditure while foraging. The relationship be- tween prey size and mouth gape was investigated using both stomach content data and prey availability data. Stomach content analysis revealed positive relationships between maximum prey size and predator mouth gape size for six of the spe- cies. Indications of prey size selectivity were only seen in the environment for European hake (Merluccius merluccius), high- lighting the potential importance of prey size over prey abundance for this species. The results demonstrate that prey abundance and size are of significance for some demersal fish species feeding primarily on benthos and will help in defining habitat requirements of demersal fish species. Resume : Plusieurs poissons demersaux comptent sur les proies benthiques comme sources de nourriture durant une partie et, en certains cas, l'ensemble de leur cycle biologique. Nous etudions la relation entre l'abondance des proies et des preda- teurs, ainsi qu'entre la taille des proies et l'ouverture de la bouche des predateurs, chez neuf especes de poissons demersaux. Parmi les especes analysees, quatre montrent une augmentation positive d'abondance en fonction de l'augmentation de l'a- bondance des proies. On croit que la taille des proies est une variable importante chez les poissons demersaux dont le po- tentiel alimentaire est limite par la taille de l'ouverture de leur bouche, puisqu'elle va influencer le taux de consommation et la depense d'energie durant la recherche de nourriture. Nous examinons la relation entre la taille des proies et l'ouverture de la bouche en utilisant a la fois des donnees sur les contenus stomacaux et des donnees de disponibilite des proies. L'analyse des contenus stomacaux montre une relation positive entre la taille maximale des proies et l'ouverture de la bouche chez six des especes. Nous n'observons d'indications de selection des proies en fonction de la taille dans le milieu que chez le merlu (Merluccius merluccius), ce qui souligne le role plus grand de la taille que de l'abondance des proies chez cette espece. Nos resultats demontrent que l'abondance et la taille des proies sont d'importance pour certains poissons demersaux qui se nour- rissent principalement de benthos et qu'elles pourront servir a definir les besoins d'habitat des especes de poissons demer- saux. (Traduit par la Redaction)

Irregular sea urchins such as the spatangoid Spatangus purpureus are important bioturbators that contribute to natural biogenic disturbance and the functioning of biogeochemical cycles in soft sediments. In the coastal waters of the Balearic Islands S. purpureus occurs in soft red algal beds, and can reach high densities. The diet of S. purpureus is unknown and it is particularly difficult to analyze the stomach contents of this group; therefore, we analyzed the fatty acid (FA) composition of the gonads and potential food resources in order to assess the trophic relationships of this species. The FA profiles of the gonads of S. purpureus agree well with the FA composition of the potential trophic resources (algae and sediment) and reveals changes between localities with different available resources. Three polyunsaturated FAs mainly contributes in the composition in the S. purpureus gonads: eicosapentaenoic acid (C20:5n-3) and arachidonic acid (C20:4n-6), both abundant in the macroalgal material, and palmitoleic acid (C16:1n-7), which is characteristic of sediment samples. Trophic markers of bacterial input and carnivorous feeding were significantly more abundant in sea urchins caught on bottoms with less vegetation. The current study demonstrates that the FA content of S. purpureus gonads is a useful marker of diet, as differences in the profiles reflected the variations in detritus composition. The results of this study show that this species has omnivorous feeding behavior; however, viewed in conjunction with available abundance data the results suggest that phytodetritus found within algal beds is an important carbon source for this species.

The bottom trawl fishery developed on the slope off Balearic Islands (western Mediterranean) has been analysed from different sources of information: (i) data obtained during experimental bottom trawl surveys developed annually since 2001; (ii) daily sale bills from the bottom trawl fleet, available since 2000. Considering both hydrographical and geomorphologic conditions, the study area was divided in four geographical sectors. Multivariate techniques were applied to identify assemblages and their main species, and to investigate the influence of environmental variables in the slope communities. Fishery-independent and fishery-dependent indicators were calculated, both at specific and community level, for the assemblages identified. In all cases, they were summarised using the Traffic Light approach. Three assemblages have been identified in the slope trawl fishing grounds off the Balearic Islands: (1) the almost unexploited shelf break, where teleosts predominate; (2) the upper slope, where teleosts still predominate but crustaceans are also very important (with Nephrops norvegicus as target species); (3) and the middle slope, where crustaceans predominate (with Aristeus antennatus as target species). Depth was the main factor affecting the species composition of the assemblages, although other factors such as area, year and effort level also affect. Indicators estimated from both sets of data suggested an improvement in the state of N. norvegicus, although the results suggest the influence of other factors than fishing impact in the state of this resource. For A. antennatus, marked differences have been found depending on the data source. In the upper slope, indicators suggested an improvement in the state of this assemblage, which can be related to a decreasing trend found in the fishing effort exerted in this depth range. Indicators from the middle slope showed differences for both sets of data. The characteristics of both data sources and of the species analysed are discussed as responsible of these differences, Sí

Short-term temporal variability in deep-sea demersal fish assemblages is described for two slope areas characterised by different oceanographic conditions, which are situated north (Balearic sub-basin, BsB) and south (Algerian sub-basin, AsB) of the Balearic Islands (western Mediterranean). A total of 75 hauls were analysed from six bottom trawl surveys carried out in the two sub-basins. At BsB, surveys were designed for sampling different slope habitats during April 1991, December 1991, March 1992 and July 1992: (i) a submarine canyon at a depth of around 450 m, (ii) the upper slope at a depth of 600-650 m, and (iii) the middle slope at a depth of around 1200 m. At AsB, surveys were carried out during October 1996 and May 1998, along a continuous transect on the upper, middle and lower slope. The taxonomic composition, ecological parameters (number of species, abundance and biomass) and biomass spectra of the assemblages, as well as the length frequency distribution of the main species, were compared for different seasons and bathymetric ranges. Forty-four demersal species were captured in BsB and 38 in AsB. Helicolenus dactylopterus and Trachyrinchus scabrus were more abundant in BsB, and Hoplostethus mediterraneus, Galeus melastomus and Centroscymnus coelolepis in AsB. Depth was the determinant factor in all the analyses. Species-specific densities (abundance and biomass) showed significant differences between surveys, depth strata and their interaction in BsB. However, survey and its interaction with depth, were not significant in AsB. We also found significant differences in relation to depth and season for the three ecological parameters tested in BsB, but only significant differences in relation to depth in AsB. Biomass spectra showed large differences in relation to depth but only slight between-survey differences, which mainly occurred in the upper slope. The length frequency distributions of single species presented short-term temporal variations, mainly due to the varying presence of a larger proportion of small or large individuals. Depth, geographic area and sampling time were the main factors determining the species composition and structure of deep-sea slope demersal fish assemblages. The effects of short-term temporal variations were observed in both the replacement and the size structure of some dominant and subdominant species throughout the year. The different temporal variation effects observed between the two sub-basins might be related to differences in productivity and its transport to the benthos. © 2008 Elsevier Ltd. All rights reserved.

The red shrimp Aristeus antennatus is one of the target species of the bottom trawl fishery of the Balearic Islands. The objective of the present paper is to study the short spatial and temporal differences of this important economic resource between two different locations off Mallorca (Cabrera: CA; Soller: SO), where a fleet mobility pattern has been detected, and to study the influence of environmental conditions on this species. Six simultaneous bottom-trawl and oceanographic surveys were carried out at these two locations in order to collect data from the demersal species, hydrography (temperature and salinity), trophic resources and sediment characteristics. The commercial fleet from both locations was monitored by monthly on-board sampling, log-books and daily landings obtained from sales slips. Additional data was obtained from other fishing surveys. Short spatial and temporal differences have been detected between both locations. The population at CA was more demographically homogeneous, while that at SO showed important variations, like high abundance of juveniles recruiting to fishing grounds in autumn–winter and high abundance of large females during summer. Several differences have also been found in the biology of the species between locations, such as males were more abundant in SO than in CA. Also, the reproductive period started sooner in SO than in CA, and the condition of pre-spawning females was better in SO. The percentage of total lipids in the hepatopancreas was minimal during the spawning period, showing their importance as a reserve of energy for the ovary ripening. Water masses could play an important role in these differences, the characteristics of water masses being more stable in CA than in SO. Red shrimp adult females seemed to be more correlated with the warmer and more saline Levantine Intermediate Waters, while juveniles (males and females) and adult males were more correlated with the colder Western Mediterranean Deep Waters, detected only in SO during autumn–winter. Two different hypothesis of mobility patterns for the species are discussed in relation to these observed differences.

Seasonal abundance and biomass of littoral fish at Posidonia oceanica seagrass meadows were characterized throughout an annual cycle in Mediterranean waters. Bimonthly beam trawl hauls were performed between 18 and 38 m depth at 4 sites sampling from 2 locations. Approximately 8230 littoral fish were collected belonging to 25 families and 51 species with Labridae and Sparidae families being predominant in terms of abundance. Mean fish abundance was 92 ± 7.5 individuals · 1000 m− 2 peaking in March, April and September and total abundance showed significant statistical differences between May and October. Densities of Diplodus annularis, Gobius sp., Mullus surmuletus, Parablennius tentacularis, Sarpa salpa, Sciaena umbra, Scorpaena porcus, Serranus cabrilla, Symphodus ocellatus, Symphodus rostratus, Symphodus tinca and Synodus saurus differed significantly between seasons. Total community biomass varied significantly along the year with maximum values observed in July (1500 g · 1000 m− 2) and minimum biomass recorded in October. The number of species ranged between 5 in January and 21 in July while the total number of individuals was 293 in July and 21 in September, and Margalef diversity index differed between 4.11 in July and 1.3 in January. Biomass peaked in summer linked mainly to the increase of S. porcus, Serranus scriba and some Symphodus species. Diversity was maximal in July and the larger mean size for most of the fish species was achieved from May to July corresponding to the recruitment peaks of some of the fish species. The SIMPER analysis showed that there are seasonal differences in the trophic roles of the fish communities at seagrass meadows. The temporal patterns observed highlight the multifunctional role of deep seagrass meadows during the summer months when all the measured parameters are maximal. Those observations point out the need for conservation measures to be intensified in the warm season.

Fish assemblages associated with Posidonia oceanica from three locations of the western Mediterranean (Mallorca, Formentera and Alacant, Spain) were sampled in order to assess their spatial variability at three different scales ranging from 100 km. Sampling was carried out using a beam trawl. Simultaneous sampling at these three spatial scales with the appropriate number of replicates implies a huge effort which is rarely possible to achieve. Consequently, we propose an arrangement of data coming from different sampling programs, after testing and making sure the specificities of each program cannot be confounded with the spatial variability. The two preliminary experimental designs adopted in order to combine the datasets were: (1) differences between two consecutive years were tested by sampling the same meadow (Formentera) in June 2001 and June 2002; and (2) differences attributable to the meadow structure were evaluated by sampling two meadows (Mallorca 2000 and Formentera 2001). The absence of any significant correlation pattern for univariate community descriptors and multivariate species-specific densities (i.e. individuals per hour) related to both between-year and within-location structural differences of the meadows, allow us to combine data from the three locations (Formentera 2001, Mallorca 2000 and Alacant 2000) in a single analysis aimed at determining how much variability is explained by the three spatial scales considered. The between-location scale (>100 km) is the most variable scale for species-specific densities (multivariate approach). Spatial variability at the smallest scale (