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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.

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.

Survival during the settlement window is a limiting variable for recruitment. The survival is believed to be strongly determined by biological interactions and sea conditions, however it has been poorly investigated. We examined the settlement patterns related to relevant biotic and abiotic factors (i.e. Density-dependence, wind stress, wave height and coastal current velocity) potentially determining post-settler survival rates of a coastal necto-benthic fish of wide distribution in the Mediterranean and eastern Atlantic, the white seabream (Diplodus sargus). An observational study of the demography of juveniles of this species was carried out at six coves in Menorca Island (Balearic Islands, western Mediterranean). Three of the coves were located in the northern and wind exposed coast, at the Northeast (NE) side; while the other three were found along the southern and sheltered coast, at the Southwest (SW) side of the island. The settlement period extended from early May to late June and maximum juvenile densities at the sampling sites varied between 5 and 11 ind. m-1 with maximum values observed in late May simultaneously occurring in the two coasts. Our analysis of juvenile survival, based on the interpretation of the observed patters using an individual based model (IBM), revealed two stages in the size-mortality relationships. An initial density-dependent stage was observed for juveniles up to 20 mm TL, followed by a density independent stage when other factors dominated the survival at sizes > 20 mm TL. No significant environmental effects were observed for the small size class (30mm TL) size class. In the NE, the wind stress consistently affected the density of fish of 20–30 mm and >30 mm TL with a dome-shape effect with higher densities at intermediate values of wind stress and negative effect at the extremes. The best models applied in the SW coves showed a significant non-linear negative effect on fish density that was also consistent for both groups 20–30 mm and >30 mm TL. Higher densities were observed at low values of wave height in the two groups. Because of these variations, the number of juveniles present at the end of the period was unrelated to their initial density and average survival varied among locations. In consequence, recruitment was (1) primarily limited by denso-dependient procedures at settlement stage, and (2) by sea conditions at post-settlement, where extreme wave conditions depleted juveniles. Accordingly, regional hydrodynamic conditions during the settlement season produced significant impacts on the juvenile densities depending on their size and with contrasted effects in respect to cove orientation. The similar strength in larval supply between coves, in addition to the similar mean phenology for settlers in the north and south of the Island, suggests that all fish may come from the same parental reproductive pool. These factors should be taken into account when assessing relationships between settlers, recruits and adults of white seabream, SI

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

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.

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 (

Young-of-the-year European hake (Merluccius merluccius) were sampled during four seasonal cruises between November 1998 and September 1999. The greatest numbers and biomass were found in spring 1999. Some 73% of juvenile fish in terms of number, and 81% in terms of biomass, were caught at depths between 60 and 160 m on the outer western Mediterranean shelf, where the water temperature ranged between 13.5 and 14°C. The length composition of samples showed there to be small hake all year around, with modes between 7 and 11 cm total length depending on the season. Otolith analysis was used to establish age at settlement (62.7 days) and to determine seasonal growth. The monthly growth rates ranged from 1.2 cm month-1 for juvenile hake captured on February 1999 to 2.5 cm month-1 for ones captured in June. The growth rates are related to survival, as was shown by the calculated hatch dates and relative abundances of recruits. This work provides information on the first year of life, recruitment and growth processes in an important species of the Mediterranean demersal ecosystem which is heavily exploited by a recruitment fishery.

The regular presence of the white shark, Carcharodon carcharias, off the Balearic Islands (western Mediterranean) is shown from 27 captures carried out with trap nets between the 1920s and 1970s and from eight attacks on cetaceans and marine turtles from the 1990s to the present. The geographic distribution, seasonality and population structure of the species in the area are analysed and discussed in relation to environmental conditions and to the proposed distribution of this species in the Mediterranean Sea.

The analysis of 131 hauls from four bottom trawl fishing surveys carried out between depths of 46 and 1713 m in two different areas off the Balearic Islands yielded a total of 23 elasmobranch species belonging to eight families. Cluster analysis and multidimensional scaling (MDS) ordination were applied to detect zonation patterns and some ecological parameters (e.g. species richness, abundance and biomass, mean weight, diversity and evenness) were calculated for each assemblage. For each area, analysis of similitude (ANOSIM) and similarity percentage analysis (SIMPER) were also applied to detect differences between seasons and depths. For the most important species (Galeus melastomus, Scyliorhinus canicula, Centroscymnus coelolepis, Etmopterus spinax, Squalus blainvillei, Raja naevus, Raja asterias, Raja clavata, Raja miraletus and Raja oxyrhinchus), abundance and size distributions were analysed by depth.

Fishes and invertebrates were collected from the continental slope southwest of the Balearic Islands, Mediterranean, in October 1996 and May 1998 from 3 faunally-distinct depth zones: 200 to 800 m (upper slope), 800 to 1425 m (middle slope) and 1425 to 1800 m (lower slope). Differ- ences in δ 15 N and δ 13 C between October 1996 and May 1998 were observed only in the crustaceans Aristeus antennatus and Nematocarcinus exilis. There were few differences among depths in δ 15 N or δ 13 C of benthic fishes or crustaceans: the shrimps A. antennatus and Acanthephyra eximia showed higher δ 15 N values at greater depth, and δ 13 C values of the fishes Alepocephalus rostratus (Ale- pocephalidae) and Coelorhynchus coelorhynchus (Macrouridae) also tended to increase with in- creasing depth. Differences in plankton and suprabenthos were also observed among zones (at depth, greater δ 15 N values of gelatinous plankton, calanoid copepods and peracarids were recorded, along with smaller δ 13 C values of gelatinous plankton and peracarids). These are attributed to a microbially-mediated increase in δ 15 N and a reduction in δ 13 C of the particulate material remaining after preferential utilization of labile organic matter in the stable and relatively high (13°C) tem- perature of the Mediterranean water column. Strong positive correlations between δ 15 N and δ 13 C data for plankton, fishes and crustaceans indicated a single primary source material for these com- munities, which is attributed to marine snow.

The Migjorn artificial reef (MAR) was deployed in the summer of 1990 and is made by 48 concrete blocks set 30 m deep on a sea bed of sand with a small proportion of Posidonia oceanica (L.) Delile meadow. Visual censuses of blocks on both substrata were carried out during the months of February, May and September in 1992 and 1993. The MAR fish assemblages were influenced by the surronding substrate. Thus, a group of ubiquitous species, frequent on both substrata and typical of natural rocky habitats (mostly Sparidae) and a group associated with the samples recorded on the Posidonia meadow (mostly Labridae) could be distinguished. Season had only a secondary and slight effect on fish assemblages. The MAR was colonized by 74% of the species in the first two years after deployment. Positive and lineal relationships between species richness, diversity, abundance of necto-benthic species and time since deployment on sandy substrata were found. On Posidonia oceanica deployment time has only increased very sedentary and cryptic species. Although some ways in which the MAR would have a productive function are not rejected, the most obvious MAR working pattern is that of fish aggregation.

Age, growth, mortality, maturity and diet were analysed for 210 common dentex from 17 to 83 cm TL collected off the island of Mallorca from 1993 to 1995. The length composition by sex showed no differences between females and males. The length-weight relationship was identical for both sexes: W = 0.011 TL 3.06 . Age at 50% maturity was reached between 2 and 4 years old. The reproductive period was centred in the second quarter of the year. Ages were estimated from whole sagittal otoliths. Marginal-increment analysis showed that a single annuli formed each year during autumn-winter. Common dentex ages ranged from 0 to 28 years. The von Bertalanffy growth equation for males was TL = 844 (1 − e( −0.1(t + 2.854) ) and for females was TL = 856 (1 − e( −0.1(t + 2.874) ). The estimate of the instantaneous rate of total mortality ( Z ) was 0.24. Empirically derived estimates of natural mortality were similar to total mortality estimates suggesting that fishing mortality is low.

14 pages, 8 figures, 6 tables, Pandalidae is one of the most diverse families of marine shrimps. Most studies on pandalid shrimps focus on their vertical zonation, and there are few studies on their horizontal distribution and their relation to environmental factors. The aim of this paper was to study the small-scale spatial and temporal patterns of pandalid shrimps in two nearby areas off the Balearic Islands that have different environmental regimes, and determine the relationship between these patterns and the environmental conditions. Information was obtained from seasonal and annual experimental surveys. The abundance and biomass of all the pandalid shrimps caught as well as the length, weight, sex and maturity stage of the most abundant species were recorded. Environmental parameters were obtained from seasonal experimental surveys and included data on hydrography, trophic resources and sediment characteristics. Information about the trawl fleet was obtained through onboard sampling, and daily landings data were obtained from sales records. Eight pandalid species were found during the annual and seasonal experimental bottom trawl surveys carried out around the Balearic Islands. These species showed clear spatial differences in their population dynamics at the two study sites, the Algerian sub-basin (AsB) and the Balearic subbasin (BsB), which could be related to the different environmental conditions of the two sub-basins. The relative importance of pandalid shrimps of the genus Plesionika in the slope crustacean communities was higher in the Algerian sub-basin. The abundances of Plesionika martia, Plesionika acanthonotus, Plesionika giglioli and Plesionika antigai were higher in the Algerian sub-basin, and only Plesionika heterocarpus, the most benthic species among those analysed, was more abundant in the Balearic sub-basin, where trophic webs are supported largely by suprabenthos rather than zooplankton biomass. The influence of water masses depends on the specific bathymetric distribution, and the shallowest species (P. antigai) was related to the Western Mediterranean Intermediate Waters, while the deepest species (P. martia and P. acanthonotus) were related to the warmer and more saline Levantine Intermediate Waters and Western Mediterranean Deep Waters. The two species found in intermediate waters (P. heterocarpus and P. giglioli) had a deeper distribution in the Algerian sub-basin, where the layer of Levantine Intermediate Waters is wider. The mean length of P. heterocarpus was higher in the Balearic sub-basin, and that of P. martia was higher in the Algerian sub-basin. The condition index was higher in the BsB than in the AsB for both P. heterocarpus and P. martia. This could be because the BsB is influenced to a greater extent by slope fronts that increase the primary production in the area, and thus enrich the trophic chain. The condition index also showed seasonal differences, which could be related to the reproductive cycle and to the availability of potential food resources. The strong relations found between the geographical distribution of the pandalid shrimps in the Balearic Islands and the environmental variables imply that there are important differences between populations of nearby areas when the environmental conditions in which they live differ, The authors thank all the participants of the IDEA, BALAR and MEDITS surveys, as well as the captain and crew of the F/V Moralti Nou, O/V Francisco de Paula Navarro and O/V Cornide de Saavedra for their help during these surveys. We also thank the skippers and crews of the F/V Arnau i Marc, Es Llevant, Antonia Munar Segunda, Villa de Sóller II, Josep del Paraguay, Marruza and Es Morras for their help while monitoring the trawl fleet. Special thanks to Manuel Hidalgo for his collaboration during both the surveys and the monitoring of the trawl fleet, Francesc Ordines for his assistance in the laboratory and Catherine Stonehouse for the language correction. The IDEA Project was funded by the Spanish Ministry of Education and Science (Plan Nacional I+D+I 2000–2003, REN2002-04535- C02-02/MAR), while the MEDER, DEMO, EVADEM and EVADEMED projects were funded by the Spanish Institute of Oceanography. The MEDITS surveys were also funded by the European Union Data Collection Framework for the Common Fisheries Policy

The synergistic effects of fishing, climate and internal dynamics on population fluctuations are poorly understood due to the complexity of these interac- tions. In this paper, we combine time series analysis and simulations to investigate the long-term dynamics of an overexploited population in the Mediterranean Sea, and its link with both fishing-induced demographic changes and hydroclimatic variability. We show that the cyclicity of the catch per unit of effort (CPUE) of Euro- pean hake Merluccius merluccius (EH) vanished in the 1980s, while the correlation between the CPUE and a local environmental index increased. Using simulations, we then show that the cyclicity observed in the EH bio- mass before the 1980s can have an internal origin, while that its disappearance could be due to the fishing- induced erosion of the age structure. Our results suggest that fishing can trigger a switch from internally gen- erated to externally forced population fluctuations, the latter being characterised by an increasing dependency of the population on recruitment and ultimately on envi- ronmental variability. Hydroclimatic modifications oc- curring in the Mediterranean in the early 1980s could have enhanced these changes by leading to a mismatch between early life stages of EH and favorable environ- mental conditions. Our conclusions underline the key effect of the interaction between exploitation and climate on the dynamics of EH and its important consequences for management and conservation.

In this paper we compare the elasmobranch composition, depth-related trends of species and community descriptors (abundance, biomass, mean fish weight, species richness and diversity) of the Balearic Islands Archipelago and Algeria (north- and southwestern Mediterranean, respectively). The samples used in this study were collected in bottom trawl surveys between 36 and 779 m depth. Generalized linear models, linear regression, cluster and similarity percentage analyses, and generalized additive models were used to compare the two areas. Twenty-nine elasmobranch species were caught, 12 of them common to both areas, 7 appearing only in the Balearic Islands, and 10 only in Algeria. The bathymetric distributions of species were, in most cases, best fitted to uni-modal response curves. The models for species common to both areas showed similar bathymetric trends, except for Etmopterus spinax, which in Algeria showed a maximum abundance lo¬cated 154 m shallower than in the Balearic Islands. Four bathymetric assemblages were identified in both areas with similar depth ranges but with different species composition. The mean values of the community descriptors were higher on the shelf in the Balearic Islands, whereas higher values were detected on the slope in Algeria. Different between-area bathymetric trends for all the descriptors were detected, with the exception of mean fish weight. The distinct environmental scenarios and fishing histories of the areas studied are discussed as underlying traits influencing the elasmobranch populations, Sí

Linking the abiotic and biotic traits of ecosystems is a critical step towards understanding their structure and functioning. Here we attempt to determine the connections between the hydrodynamics, benthic landscape and the associated fish communities on the coastal continental shelf off the Balearic Islands (western Mediterranean). Specifically we investigate the role the hydrodynamics play in shaping the benthic landscape, and whether the hydrodynamics affect the composition and structure of demersal fish communities. A realistic numerical model was used to establish the hydrodynamic characteristics of the area. The study area showed high hydrodynamic variability on a medium spatial scale (tens of km) in terms of mean water velocity (Ū). Principal component analysis was used to determine the main gradients of macro-epibenthic variability. Redundancy analysis (RDA) was used to model the effect of the hydrodynamics on macro-epibenthic species. RDA was also used to model the effect of the hydrodynamics and macro-epibenthos on the abundance of the associated fish fauna, and on its biomass at a community level using biomass spectra classes. The results showed that the hydrodynamics had a significant influence on the distribution of both macro-epibenthic species and the associated fish species. The latter was also influenced by the macro-epibenthos. Fish size appeared to be a key attribute for the distribution of species across gradients of Ū and macro-epibenthic change. Our findings can be applied in ecosystem-based fisheries management, as they show that it is necessary to take into account both the biotic and abiotic traits of the habitats when the habitat use and requirements of the associated species are defined. © 2011 Elsevier Ltd., This paper is a result of the MIGJORN project co-financed by the Conselleria d'Agricultura i Pesca of the Govern de les Illes Balears and the Spanish Institute of Oceanography; and the INDEMARES project (EU Life project) and Fundación Biodiversidad.

22 pages, 10 figures, 3 tables, Short spatio–temporal variations in the feeding intensity and the diet of the European hake, Merluccius merluccius, together with the abundance of their potential prey were studied between August 2003 and June 2004 at two locations, northwest (Sóller) and south (Cabrera), off the island of Mallorca (Balearic Islands, Western Mediterranean) at depths between 150 and 750 m. The two areas present different oceanographic conditions. Hake was mainly distributed along the shelf-slope break and the upper slope (between 166 and 350 m) where recruits (TL, M. Hidalgo work was supported by a FPI Grant no. BES-2003-2588 from the Spanish Ministry of Education and Science, and by the Project REN2002-04535-C02-01/02

Seasonal pattern of fish recruitment can vary over years, and the coupling of such pattern with favourable trophic-environmental conditions may trigger non-stationary and non-linear effects on the yearly recruitment variability. The relative contribution of intra-annual discrete recruitment events (REs) to recruitment is often the basis of the inter-annual fluctuations in abundance and biomass of exploited fish populations which are based on a small number of age classes. In this study, REs of European hake (Merluccius merluccius L.) were identified in the north and south of the Balearic Islands (NW Mediterranean) during the 2004 recruitment season and investigated for growth and physiological and morphological condition. Five REs were identified with different contributions in abundance to the annual recruitment in each area coming from different intra-annual spawning batches. Growth rates were similar between the REs with the exception of the last event of the season. Conversely, large differences in morphological and physiological condition were observed between REs and were due to: different environmental-trophic scenarios encountered, and ontogenetic changes related to the recruitment to the shelf-break grounds (ca. 11 cm, 5-6 months of life) which triggered a trade-off in the energy allocation strategy. The spatial-temporal variability in the physiological condition among REs at the beginning of the recruitment season might be explained in the basis on a 'condition expanded match-mismatch hypothesis'. We advance that individuals recruiting in the north, which were in better condition and temporally and spatially differenced from the south, have most probably hatched in separated locations with different food availability for larvae and early life stages. We propose that hake recruiting to the north and south of the island are from different origins, mainland and the islands respectively, and have benefited from different environmental conditions. This results in a different condition but not in different growth rates. © 2009 Elsevier Ltd. All rights reserved.

Scorpaena notata is a small, sedentary scorpaenid species widely distributed in the Mediterranean and adjacent waters of the Atlantic. In the western Mediterranean it inhabits coastal continental shelf bottoms. In the Balearic Islands, these bottoms are characterised by the presence of the facies with red algae, including both Peyssonnelia and mäerl beds. These beds enhance the structural complexity, biodiversity and secondary production of the soft bottoms. Due to the oceanographic conditions of the Islands, the facies with red algae are especially rich in terms of biomass and algal coverage, and are widespread distributed between 40 and 90 m depth, where trawlers exploiting the continental shelf operate. The present work studies the biology of S. notata and its relationship with habitat characteristics. Special attention is focused on the aspects related to fish condition and growth as a tool to assess the importance of the facies with red algae for fish. The reproduction period of S. notata in the Balearic Islands occurs in summer and is accompanied by a decrease in hepatic condition, as it happens in the adjacent area off the Iberian Peninsula; however, in contrast with this adjacent area, this period is accompanied by a decrease in somatic condition and an increase in feeding potential, which suggests that these could be adaptations to the higher oligotrophy of the Archipelago. The standardised algal biomass (mostly Rhodophyceae) present in the bottoms positively affected the abundance, somatic condition and feeding potential of S. notata. Individuals inhabiting bottoms with the highest algal biomass showed faster growth than the entire population analysed together. Both, the structural complexity and the availability of preys in the facies with red algae are revealed as advantageous traits for the life history of fish. Taking into account the importance of individual health for the overall success of the population, the indexes studied here could be a useful tool for identifying high quality or essential fish habitats. Our results highlight the importance of the facies with red algae as oasis of high productivity where benthic fish can circumvent the general oligotrophic conditions of the Mediterranean, and the necessity of urgent management measures in order to protect them from human impacts., Sí

In 1980 and 1995, the European hake (Merluccius merluccius) population off the Balearic Islands (northwestern Mediterranean) underwent changes at both the individual level and the population level. There was a sharp decrease in abundance that coincided with a change in the seasonal catch-per-unit-effort pattern in 1980. A new population scenario emerged after 1980 characterized by an increase in the intrinsic growth rate and a decrease in carrying capacity; however, catchability remained the same. An age-structure truncation could have caused these changes, making the population more dependent on year-to-year recruitment. A change in size structure also occurred in 1995, which was evidenced by a sudden decrease in the mean length-at-age (L) and abundance of recruits and a change in the density-dependent effect on recruits. As the Mediterranean trawl fishery mainly harvests recruits and juveniles and fishery harvesting induces adaptive changes in life history traits, the sharp decrease in L of recruits could be explained as a growth reduction due to the selective pres- sure to stay under mesh size for longer and thus maximize survival until reproduction. These individual and population transitions explain the changes in the response to the environmental forcing observed in the European hake off the Balearic Islands, Sí

18 pages, 8 figures, 5 tables.-- Available online Nov 9, 2007.-- Issue title: "The Wrapping Up of the IDEA Project: - International workshop on environment, demersal resources and fisheries"., This study evaluates the link between the recruitment process of European hake (Merluccius merluccius L.) of the Balearic Islands (western Mediterranean) and the environmental and physiological conditions. Spatio-temporal variation of abundance and condition of fish were evaluated at two locations each with different oceanographic conditions, one in the north (Sóller, SO) and another in the south (Cabrera, CA) of Mallorca Island. Environmental variables explored were hydrography, sediment characteristics, phytoplankton pigment concentration (ppc) and the trophic resources of hake. Individuals were divided in three life stages: recruits, post-recruits and young adults. Hepatosomatic index (HSI), relative condition index (Kn), gonadosomatic index (GSI) and fullness index (FI) were analysed for the three life stages. Recruitment starts in February with the incorporation of smaller hakes, and it can be followed through spring and early summer with a peak in April. However, some spatial heterogeneity in the recruitment process has been found between north and south of the Island. The main pulse of recruitment occurred at a different time in the two areas. Spatial heterogeneity was also consistent with the condition of hake recruits, with higher values of Kn and HSI at SO than at CA. Maximum values of Kn were found in February at SO and in April at CA, coinciding with the start of the different recruitment pulses to the fishing grounds. Post-recruits and young adults also showed higher condition at SO than at CA. The arrival in spring of the Western Winter Intermediate Waters (WIW) drives the spatial-temporal variation in abundance and condition of hake. Ppc was highly correlated with recruit abundance with a time lag of two months, while for post-recruits the time lag was three months. The observed differences in the condition of hake between areas could be a consequence of the fact that the waters to the north of Mallorca are comparatively more under the seasonal influence of WIW which is formed in more productive areas. Thus, this study characterises the short temporal and spatial variability in the hake recruitment process off the Balearic Islands, both in terms of abundance and fish condition. This pattern is explained on the basis of the mesoscale environmental variability observed between north and south of Mallorca and the ecological adaptive strategy of recruiting in the optimal environmental season., This work was supported by a FPI grant N° BES-2003-2588 from the Spanish Ministry of Education and Science granted to M.H., and by the project REN2002-04535-C01/02.

The aim of the present paper is to study the relationships between some climatic indices and parental stock, recruitment and accessibility to trawl fishery of hake (Merluccius merluccius) and red shrimp (Aristeus antennatus) off Balearic Islands (western Mediterranean). Available annual catch per unit effort, recruitment and spawning stock biomass have been used as biological data. As environmental data, the meso-scale IDEA index and the large-scale North Atlantic Oscillation (NAO) and Mediterranean Oscillation (MO) indices have been used. To analyze possible links between these indices with the population dynamics of demersal resources, two non-linear approaches have been applied: (i) stock-recruitment relationships from Ricker and Beverton-Holt models, by sequentially incorporating environment factors; (ii) generalized additive modelling, both classical general and threshold non-additive models were considered. The latter simulate an abrupt change in explicative variables across different phases (time periods or climatic index values). The results have shown that two oceanographic scenarios around the Balearic Islands, associated with macro and meso-scale climate regimes, can influence the population dynamics of hake and red shrimp. This is especially true for recruitment, which seems to be enhanced during low NAO and IDEA indices periods. During these periods, colder-than-normal winters generate high amounts of cold Western Mediterranean Intermediate Waters (WIW) in the Gulf of Lions, which flow southwards and reach the Balearic Islands channels in spring, increasing the productivity in the area. This oceanographic scenario could also be favourable to the distribution of hake on the fishing grounds where the trawl fleet targets this species, increasing its accessibility to the fishery. Both spawning stock and abundance of red shrimp seems to be also enhanced by high MO index periods, which could reflect the increased presence of the saline and warm Levantine Intermediate Waters (LIW) in the study area, extending over the fishing grounds of this species. The proposed interactions can be useful to assess and manage these important demersal resources. © 2007 Elsevier B.V. All rights reserved., The IDEA project has been funded by the Spanish Ministry of Education and Science (Plan Nacional I+D+i 2000-2003, REN2002-04535-C01-02/MAR)

The spatial and temporal variations of deep-sea megafaunal assemblages from the western Mediterranean are analysed in the present paper. The assemblages from two locations of the Balearic Islands situated 120 km apart were compared using data collected seasonally on a bathymetric stratum covering the 150–750 m depth range during six bottom-trawl surveys. The assemblage structure, in terms of species composition, species dominance and population sizes, was differentially affected by the spatio-temporal variables analysed (depth, location and fishing period). Although depth was the main factor determining the assemblage composition, the differences obtained between the two locations were also relevant. On the upper slope these between-location differences in the dynamics of megafaunal assemblages were found to be related to the effect of fishing exploitation. Population size-based metrics and biomass spectra were good predictors of meso-scale fishing effects, and were mainly reflected by elasmobranchs and demersal teleosts. Nevertheless, the effects of fishing depended on the species considered. Two dominant large-sized fish species found on the upper slope in both localities, Galeus melastomus and Phycis blennoides , had higher biomass values associated with lower fishing effort. Although the mean body weight (MBW) of both species and also the mean maximum body weight (MMBW) of G. melastomus agreed with this pattern, the P. blennoides MMBW did not. This last case could be indicative of natural size-trends such as the bigger–deeper phenomenon which refers to the displacement of large individuals towards the deeper limit of their bathymetric distribution, beyond the maximum depth sampled in this study for this species. By contrast, the target species of the upper slope fishery, the red shrimp Aristeus antennatus, was not negatively affected by the direct impact of fishing activity and other environmental factors, such as the presence of specific water masses could also be important.

The present study is a mesoscale analysis of latitude and depth related trends in abundance, biomass and body size of the four grenadier species Caelorinchus caelorhincus, Hymenocephalus italicus, Nezumia aequalis and Trachyrinchus scabrus inhabiting the deep western Mediterranean. We have analysed data from seven annual bottom trawl surveys, carried out down to 800 m depth along the Iberian Mediterranean coast covering a distance of approximately 1200 km. The objectives were to establish general patterns in the mesoscale distribution of abundance, biomass and body size of deep-water grenadier fishes and also analyse the consistency of the bathymetric distribution of these parameters along a large latitudinal gradient. Five complementary series of analyses have been completed. The first focussed on describing the general patterns of abundance and size by correspondence canonical analysis, CCA, in the area. The second and third series focussed on the existence of temporal, geographical and bathymetric trends of abundance, weight and mean size by analysis of covariance, ANCOVA and multiple regression analysis. The fourth series compared the frequency distributions of body length. Finally, the last series focussed on the patterns of abundance versus size. The total number of individuals of all four grenadier species captured in 260 bottom trawls amounted to 27,435 and their weight was 1404 kg. No general trends for the four species have been observed between years. All four species showed a general pattern of increasing size with depth, which, except in the case of C. caelorhincus, was consistent along a large latitudinal gradient. Nezumia aequalis was unique in showing the same noticeable trend of increasing abundance with depth along the entire latitudinal range, but with clear differences in the intercepts. The abundance of N. aequalis and C. caelorhincus decreased significantly northwards. Hymenocephalus italicus was the least abundant species and had a homogeneous distribution without any specific trend along the entire latitudinal range analysed. The distribution of T. scabrus in the Mediterranean seemed to be more localised. Higher abundances were found to the north and south of the latitudinal gradient with lower values between. The grenadiers studied also showed a general trend of decreasing mean size northwards, except in the case of the smallest species, H. italicus. The relation between abundance and body size differed between sectors for the whole grenadier population and species-specific variations were also observed. The relationship between individual body mass and population density fit well to a second-order polynomial function rather than to a linear regression, showing a significant trend for density to increase with increasing size until some mid-point, then to decline with increasing size thereafter. The observed latitudinal gradient in the distribution patterns of grenadiers along the upper slope of the western Mediterranean can be discussed in relation to direct and indirect factors of biogeographic, environmental and anthropogenic origin. © 2006 Elsevier Ltd. All rights reserved., This paper is a result of the Spanish MEDITS project (DGXIV/IEO/054)

Fishing grounds off the northern coast of Mallorca Island (western Mediterranean Sea) are subject to very different fishing efforts as a result of both commercial and recreational activities. We analysed the variability at different spatial scales of the fishable community associated with shallow littoral rocky bottoms. Underwater visual censuses (UVC) were carried out in 3 localities that have different fishing pressure. Three sites were sampled within each locality, and nine 50 m long UVC transects were completed within each site. Multivariate correlograms showed that the transects were completely independent statistical units even when located less than 75 m apart. The spatial variability of the fish assemblage is remarkable. A redundancy analysis (RDA) revealed highly significant differences between the species relative abundance of the different localities. The bottom structure and rugosity were not detected to have any effect on the fish assemblage. The variability of the bottom structure at the below-locality level shows that these tests were powerful enough and that the effects of bottom structure were not confused with the effects of fishing pressure. Localities with lower fishing pressure showed significantly higher species richness (8.4 ± 0.3 and 8.9 ± 0.3 species 250 m-2) and abundance (54.6 ± 4.4 and 65.9 ± 4.1 ind. 250 m-2) than localities with higher fishing pressure (6.7 ± 0.3 species 250 m-2 and 41.1 ± 4.5 ind. 250 m -2). Serranus cabrilla and Symphodus tinca were significantly less abundant in the localities with higher fishing pressure. These results suggest that differences in fishing pressure may generate strong gradients of faunistic change even at relatively small spatial scales (5 to 10 km), and that the observed pattern emulates what would normally be expected to happen after protection measures are established in marine protected areas. © Inter-Research 2005.

17 pages, 5 figures, 3 tables, We have compared the distribution of mesopelagic, benthopelagic and benthic fauna between two areas: one on the continental side of the Catalan Sea (cCS: northwestern Mediterranean) and one to the SW of the Balearic Islands (SWB: southwestern Mediterranean) at depths between 147 and 2266 m. Based on 88 bathyal fish and crustaceans (Decapoda and Peracarida) dominant in these communities, we compared the maximum depth of occurrence (MDO) of (upper) middle-slope species and the minimum depth of occurrence (mDO) of lower-slope dwelling species. Mid-slope fish, decapods, peracarids and, within the latter, amphipods and cumaceans had a deeper MDO in the cCS than in the SWB. Depth differences between MDO of species were significant for all taxa, except isopods. In the same way, lower slope fish and decapods had a shallower mDO in the SWB than in the cCS. Within peracarids, the dominant taxon (amphipods) also followed this trend. Depth differences in mDO of species between the areas were significant for decapods and for amphipods (not for fish, nor all peracarids nor cumaceans). In summary, most taxa showed a deeper depth distribution of middle-slope species in the cCS, and a shallower depth distribution of lower-slope dwelling species in the SWB. This suggests that the whole community, from small detritus-feeders (peracarids) to top predators (fish) have a similar response to a common signal. Much basic information on the biology and possible environmental factors affecting deep-sea species distribution is not available, so causes of the trends demonstrated here cannot be fully evaluated. In spite of these obvious limitations, we have shown that (1) mesopelagic decapods (e.g., Gennadas elegans and Sergia robusta), with a higher dependence upon primary sources of food close to the surface primary production, showed greater differences in their mDO between the areas than benthopelagic (e.g., Acanthephyra eximia, Nematocarcinus exilis) and benthic (e.g., Stereomastis sculpta, Munida tenuimana, Geryon longipes) species, and (2) fish at lower trophic levels, deduced from fractional trophic levels, showed higher differences in the MDO than fish at higher trophic levels. Trophic position of species in food webs seems the most important factor affecting the distributional differences between contrasting areas, First two authors benefited from two contracts from the Ramón y Cajal Programme (Calls 2001 and 2002, MCYT: Spanish Government)

Knowledge of deep-sea reproductive biology is slight and interpretations of reproductive strategies in deep-sea fishes are controversial. Since the Mediterranean is a fairly stable and constant sea, we might expect a consistent pattern of reproduction of deep-sea species. Three gadiforms species with a succesive bathymetric and an ecological and economical importance in the Mediterranean fishing industry, Phycis blennoides, Mora moro and Lepidion lepidion, were selected for the present study. These three species of gadiforms are sexually dimorphic and their reproductive population is located at the lower zone of their bathymetric range. Females were always bigger than males. The smallest mature male was observed at 19, 32 and 18 cm TL (total length) and the smallest mature female at 20, 34 and 20 cm TL for P. blennoides, M. moro and L. lepidion respectively. The three species are iteroparous and females could be all-at-once or batch-spawners. An autumn mature season was observed for P. blennoides, whereas M. moro and L. lepidion had mature individuals all year round except in summer. Hence, physical constancy at greater depths is able to lengthen the reproductive season and the deepest species has a quasi-continuous reproductive pattern. Similar reproductive tissues have been found in the three species studied, and they show analogous structure with other deep-sea gadiforms and their shallow-water congeners, This paper is a result of the Spanish CICYT Projects RETRO (MAR90-757), ZONAP (PB90-O166) and BATMAN (AMB93/0283) and the European Commission project EU FAIR (CT 95-0655)

13 pages, 9 figures, 3 tables, During 2 deep-sea oceanographic cruises carried out in October 1996 and May 1998, megafauna (fish and decapod crustaceans), suprabenthos, zooplankton, and environmental variables from the water column (fluorescence and light transmission) were simultaneously collected between 210 and 1752 m depth. Fish were the dominant megafaunal taxon in biomass along the slope; decapod crustaceans were co-dominants at intermediate depths (between 402 and 710 m). Suprabenthos and zooplankton attained their maximal biomass at intermediate depths, with deeper maxima detected for suprabenthos (between 802 and 1322 m) than for zooplankton (between 402 and 802 m). Fish and decapod biomass were weakly correlated with each other, and with the suprabenthos-zooplankton biomass, fluorescence and light transmission. Significant correlations were, however, detected between the suprabenthos and zooplankton and their possible food-sources deduced from fluorometer and light transmission data, with different patterns depending on the distribution of each compartment (trophic level) in the water column and the sediment-water interface. Within a single taxon (crustaceans), size distribution for suprabenthos-zooplankton and megafaunal species followed opposite temporal patterns in our study. Among suprabenthos-zooplankton species, smaller specimens (recruitment) were detected in October 1996, coinciding with the highest fluorometer signals in the water column. The dominant phytoplankton/phytodetritus consumers (the euphausiid Euphausia krohni and the mysid Boreomysis arctica) showed clearer recruitment peaks during October than those species preying upon meiofaunal taxa (the amphipod Rhachotropis caeca, and the isopod Munnopsurus atlanticus). These results suggest that the influence of food input signals progressively decreases with increasing trophic level, and therefore the indirect effect of superficial production on top trophic levels is difficult to establish at least for the short time scales of our oceanographic surveys

The distribution and spatio-temporal variation of Helicolenus dactylopterus (Pisces: Scorpaenidae) population was studied from 816 bottom trawls developed along the Iberian coast. Multifactor analysis of variance was used to test the differences in abundance and biomass and cluster analysis was applied to detect differences in population structure. The results showed a bathymetric and latitudinal gradient in abundance and population structure along three geographic sectors in the surveyed area. In the southern area, the species was more frequent and showed a wider bathymetric distribution range than northwards. The depth range with the maximum frequency of occurrence was also wider in the southern area than northwards. Similar trends were observed in terms of abundance and biomass, with the highest and lowest indices in the southern and northern areas, respectively. The age composition of the catches showed that the population consisted mainly of young-of-the-year and juvenile fish. This fraction of the population is well represented, at a mesoscale, along the whole surveyed area, but adults are well represented only at a local scale, at the deepest strata surveyed in the southern area. In this case, recruits of age 0 and juveniles up to 4-y old were restricted to depths shallower than 500 m, while adult fish older than 6y of age appeared below this depth. In the southern area, seasonal changes in the population structure were also observed, with modes of small fish (3-6 cm) from March to June, as a consequence of the species recruitment to the bottom. Some direct and indirect factors of biogeographic, environmental and anthropogenic origin affecting the observed gradient are discussed., RETRO; ZONAP; MERSEL; MEDITS and DGXIV/IEO

The catch composition of two commercial vessels of the trawl fleet operating from Mallorca (Balearic Islands, western Mediterranean) was analysed. A total of 4959 kg resulting from 144 fishing hours was sampled from October 1996 to December 1997. The fishes represented the major proportion with respect to the total catch. The analysis of the fish discards assembled them in three depth related groups: group A (mean depth 300 m); group B (mean depth 489 m); and group C (mean depth 616 m). Species richness, number of individuals and biomass decreased with depth. The diversity and evenness indices also varied with depth, but no significant differences were found. Fishes, with around 70%, dominated the biomass discarded in the three depth groups. Within the landings, fish biomass also represented the major proportion in groups A and B, but in group C the crustaceans biomass dominated. Our results confirm that an important fraction of the catch of the two deep-sea decapod crustacean fisheries is discarded., This paper is a result of the European Project Developing deep-water fisheries: data for their assessment and for understanding their interaction with and impact on a fragile ecosystem (EU FAIR PORJECT CT 95-0655; European commission DG-XIV, Fisheries).

Helicolenus dactylopterus was studied from 15 bottom trawl cruises carried out between 1991 and 1997 along the Iberian Mediterranean coast. Age and growth of this species were determined for two different areas, the Alboran Sea and the Balearic Sea, characterised by distinct oceanographic and geomorphological conditions. The length (TL), weight (TW), and sex of 3093 individuals were recorded, and sagittal otoliths were collected in subsamples selected to cover the size distribution of both sexes in each area. Marginal increment analysis of specimens between 1 and 4 years old suggested that a single annulus was formed each year. The location of the first annulus was also validated by means of daily growth increments in the otoliths. The fish length range was between 3 and 36 cm in the Alboran Sea and between 2 and 33 cm in the Balearic Sea, which corresponded to individuals between 0 to 30 years old and 0 to 24 years old, respectively. However, 50 and 70% of the studied population in each area were between 0 and 3 years of age. The growth parameters obtained from the age–length relationships showed higher differences between sexes than between areas. In both areas, the maximum age observed and the predicted lengths of males were greater than those of females. The von Bertalanffy growth equation was TL=27.1(1−exp(−0.12(t+2.65))) for females and TL=32.3(1−exp(−0.09(t+3.31))) for males in the Alboran Sea, and TL=27.0(1−exp(−0.16(t+1.62))) for females and TL=32.5(1−exp(−0.10(t+2.62))) for males in the Balearic Sea

δ15N and δ13C were determined for plants, invertebrates and fishes collected from 3 sites on the southern coast of the Mediterranean island of Mallorca, Spain. The sites were separated by distances of 1250 to 3750 m. The mean δ15N of plants was 1.1 to 4.1‰, benthic invertebrates 5.9 to 6.9‰, planktonic invertebrates 5.5 to 5.8‰ and fishes 84 to 13.8‰. δ15N became enriched with increasing trophic level. The mean δ13C of plants was -11.4 to -16.3‰, benthic invertebrates -14.8 to -16.8‰, planktonic invertebrates -19.3 to -19.8‰ and fishes -16.1 to -19.2‰. There were significant differences in the isotopic composition of individual species within the plant, invertebrate or fish groupings at each site and there were significant differences in the isotopic composition of the same species at different sites. Depleted 13C was associated with benthic food chains and enriched 13C with planktonic chains. The data suggest that benthic food chains are important to the rocky reel associated fishes studied, as might be expected in a nutrient poor system where planktonic production is relatively low. However, the variance in δ13C composition between sites was such that the relative significance of the 2 pathways could not be determined. 15N measurements indicated that some of the fish species studied had adopted different feeding strategies at different sites and, as a result, individuals of the same species could sometimes be assigned to different trophic groups at different sites. The data suggest that these fishes exhibit plasticity in their feeding strategies and this may provide them with greater adaptive flexibility to respond to site-specific changes in food availability. Moreover, the data provide empirical support for current theories of food web dynamics which suggest that trophic 'levels' are dynamic rather than fixed and that 'multichannel omnivory' is an important feature of food webs.

Comparativa de abundancias y biomasa de la ictiofauna profunda (200-1800 metros)de las proximidades de las islas Baleares. Mapas, gráficos y listado de especies, A total of 13 026 fishes belonging to 82 species and 43 famllies were collected in a continuous transect between depths of 200 and 1800 m south of the Baleanc Islands (Algerian basin, western Mediterranean). The analysis of 32 bottom trawls showed the existence of 4 groups associated with the upper slope (groups 1 and 2, from 200 to 400 and 400 to 800 m, respectivelv), middle slope (group 3, from 800 to 1400 m) and lower slope (group 4, below a depth of 1400 m) Thc differcnces in the mean values of the ecological parameters species richness, abundance, biomass and mean fish weight were also indicative of distinctive characteristics between these fish assemblages. Species richness decreased significantly with depth. The highest values of diversity corresponded to the samples from group 2. Biomass did not show any specific trend throughout the whole bathymetric range. Mean fish weight show 2 different trends along the continental slope: a bigger-deeper phenomenon at the upper 1000 to 1200 m depth. and a smaller-deeper phenomenon below this depth. Our results are compared with those obtained in the north Atlantic basin and in the western Mediterranean (Balearic basin), and the main factol-s affecting these deep-sea fish assemblages are discussed, EU FAIR PROJECT CT 95-0655. European Commission DC;-XIV, Fisheries

The growth of three demersal species dominant in biomass and abundance in the Weddell Sea, Chionodraco myersi (channichthyid), Trematomus eulepidotus (nototheniid) and Dolloidraco longedorsalis (artedidraconid), was studied on specimens caught in summer. Ages were determined using ground and polished otolith sections and an image analysis system to measure the otolith radius and distances of each growth increment to the otolith core. Ageing precision and accuracy have been estimated. Indirect validation methods, based on the increment growth pattern, were applied to support the annual periodicity of the increments. Due to the lack of some age classes, back-calculated age-length keys were determined and used to fit the von Bertalanffy growth parameters by sex and species. The determined values showed sexual dimorphism, with females having faster growth rates, except in D. longedorsalis. The growth performance index was between 1 and 2, as in other high-Antarctic fish. For T. eulepidotus, age and growth data were available, but this is the first report for C. myersi and D. longedorsalis. Moreover, this is the first time that accuracy and precision have been estimated for high-Antarctic fish age determination.