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Cephalopods and elasmobranchs are important components of marine ecosystems, whereby knowing the ecological role they play in the structure and dynamics of trophic networks is paramount. With this aim, stomach contents and stable isotopes of the most abundant elasmobranch and cephalopod species (5 and 18 species, respectively) inhabiting deep-sea ecosystems from the western Mediterranean were analyzed. The predators investigated encompassed different taxonomic groups, such as rays and sharks within elasmobranchs, and squids, octopuses and cuttlefishes within cephalopods. Specifically, we investigated ontogenetic shifts in diet, feeding strategies and prey consumption, trophic structure and potential dietary overlap between and within both taxonomical groups. Stable isotope analysis revealed ontogenetic shifts in diet in three elasmobranch (rays and sharks) and two cephalopod (octopuses and squids) species. Isotopic data showed a contrasting food source gradient (δ13C), from pelagic (squids and cuttlefishes) to benthic (octopuses and elasmobranchs). Stomach data highlighted a great variety of trophic guilds which could be further aggregated into three broad categories: benthic, benthopelagic and pelagic feeders. The combination of both stomach content and stable isotope analyses revealed a clear food partitioning among species. Mesopelagic prey were found to be an important food resource for deep-sea elasmobranchs and cephalopods, which could be related to the strong oligotrophic conditions in the area. The observed differences in feeding strategies within cephalopods and elasmobranchs should be taken into account when defining functional groups in trophodynamic models from the western Mediterranean. Our results also revealed that cephalopods play a key role for the benthopelagic coupling, whereas demersal elasmobranchs contribute primarily to a one-way flux accumulating energy resources into deep-sea ecosystems., SI

According to their main life history traits, organisms can be arranged in a continuum from fast (species with small body size, short lifespan and high fecundity) to slow (species with opposite characteristics). Life history determines the responses of organisms to natural and anthropogenic factors, as slow species are expected to be more sensitive than fast species to perturbations. Owing to their contrasting traits, cephalopods and elasmobranchs are typical examples of fast and slow strategies, respectively. We investigated the responses of these two contrasting strategies to fishing exploitation and environmental conditions (temperature, productivity and depth) using generalized additive models. Our results confirmed the foreseen contrasting responses of cephalopods and elasmobranchs to natural (environment) and anthropogenic (harvesting) influences. Even though a priori foreseen, we did expect neither the clear-cut differential responses between groups nor the homogeneous sensitivity to the same factors within the two taxonomic groups. Apart from depth, which affected both groups equally, cephalopods and elasmobranchs were exclusively affected by environmental conditions and fishing exploitation, respectively. Owing to its short, annual cycle, cephalopods do not have overlapping generations and consequently lack the buffering effects conferred by different age classes observed in multi-aged species such as elasmobranchs. We suggest that cephalopods are sensitive to short-term perturbations, such as seasonal environmental changes, because they lack this buffering effect but they are in turn not influenced by continuous, long-term moderate disturbances such as fishing because of its high population growth and turnover. The contrary would apply to elasmobranchs, whose multi-aged population structure would buffer the seasonal environmental effects, but they would display strong responses to uninterrupted harvesting due to its low population resilience. Besides providing empirical evidence to the theoretically predicted contrasting responses of cephalopods and elasmobranchs to disturbances, our results are useful for the sustainable exploitation of these resources, SI

Cephalopod populations show wide temporal fluctuations in abundance, which have usually been investigated at inter-annual scales related to environmental variability. However, cephalopods are also strongly linked to seasonal environmental fluctuations owing to their short life cycles and single seasonal breeding. Therefore, population abundance critically depends on the success of breeding and recruitment from the previous year and the optimization of resources in a narrow period of favorable conditions. This adaptation of population dynamics is paramount in marked oligotrophic systems, such as the western Mediterranean Sea. We used monthly landings per unit effort (LPUE) to explore the spatio-temporal variability in seasonal patterns of three cephalopod species (Illex coindetii, Eledone cirrhosa and Octopus vulgaris). Common trends across the study area were characterized for each species. In all cases, seasonal patterns were geographically aggregated in relation to differences in local environment (i.e., primary production and surface hydro-climatology). Variability in the mean seasonal pattern over time was also investigated under contrasting environmental or population regimes. The mean seasonal trend was more pronounced in regimes of high-population densities, suggesting a density-dependent control that can modify the strength of the environmental forcing in the seasonal patterns. Our study also evidences a spatial synchrony in the seasonal fluctuations of LPUEs. Scales of synchrony ranged from 70 to 200 km, indicating a patchy-aggregated spatial pattern as a part of complex population structures in the western Mediterranean. Improving our understanding of seasonal dynamics of cephalopods across temporal and spatial scales may lead to improved forecasts and management strategies., SI

The cuttlefish Sepia officinalis constitutes an important fishery resource in the Mediterranean, where it is exploited by both the bottom trawl and small-scale fleet. However, there is currently scarce information on the Mediterranean stocks, since most studies on the population dynamics of this species have been undertaken in the northeast Atlantic. In this work we first analysed different aspects of the cuttlefish life-history from the western Mediterranean such as population structure, reproduction and the trade-offs between somatic condition and reproduction investments. Secondly, we investigated the effects of different environmental parameters (e.g. climate indices, sea surface temperature (SST), rainfall, chlorophyll-a concentration (Chla) and moon phase) on these populations, analysing several landing time series spanning the last 45 years. Our results revealed that Mediterranean cuttlefish populations exhibit strong seasonal variations owing to a reproductive migration towards coastal waters. The positive relationships between somatic and reproductive condition pointed to an income breeder strategy; this was reinforced by the percentage of empty stomachs, which was lowest just before the reproductive period peak. Despite the putative high sensitivity of cephalopod populations to external abiotic factors, our results showed that Mediterranean cuttlefish populations were not affected by most of the environmental parameters investigated. Significant effects were found for SST and a local climatic index, but no or very weak influences were evident for other parameters such as large-scale climatic phenomena (e.g. North Atlantic Oscillation, Mediterranean Oscillation) or other locally-related variables (e.g. rainfall, Chla). Our results revealed a shift in the cuttlefish population dynamics in the early 1980s, which could be related to important changes in the local hydroclimatology reported by previous authors.

We assessed the elasmobranch communities exploited by the bottom trawl fishery off the Balearic Islands (northwestern Mediterranean) by analysing two time series containing information with different levels of detail: 1) a long-term series containing the abundance indices of the whole elasmobranch community landed from 1965 to 2009; and 2) a shorter time series from 2000 to 2009 from two different data sources (daily sales records: 2000-2009; bottom trawl surveys: 2001-2009), with information that allowed the shelf and slope to be analysed separately and different community parameters and abundance indices to be studied. Temporal trends of all these variables were used as ecological status indicators and tested with generalized additive models and analysis of variance. They were finally summarised using the Traffic Light methodology. The long-term series showed two marked trends, an inter-annual decreasing trend that would be a consequence of the large increase in fishing effort, and an intra-annual trend with a clear peak in May in accordance with the seasonal biological cycle of these species. However, data from the last ten years revealed differences between the shelf and slope, as some parameters increased significantly over time on the shelf but did not follow any trend on the slope. The Traffic Light methodology captured these differences well, demonstrating its usefulness for interpreting ecological transitions at a glance. Se han evaluado las poblaciones de elasmobranquios explotadas por la pesca de arrastre de las Islas Baleares (Mediterráneo noroccidental) analizando dos series temporales con información a distinto nivel de detalle: 1) una serie larga que contiene únicamente el índice de abundancia de toda la población de elasmobranquios desembarcada entre 1965 y 2009 y 2) una serie corta a lo largo de la primera década del siglo XXI proveniente de dos fuentes de datos diferentes (hojas de venta diarias: 2000-2009; campañas de arrastre de fondo: 2001-2009), que permitieron el análisis, para la plataforma y el talud por separado, de diferentes parámetros de la comunidad además de índices de abundancia. Las tendencias temporales de todas estas variables se usaron como indicadores ecológicos de estado y se testaron aplicando modelos generales aditivos y análisis de la varianza y finalmente se han resumido usando la metodología de los Semáforos. La serie larga mostró dos señales claras, un decrecimiento interanual que podría ser consecuencia del importante incremento del esfuerzo pesquero, y una tendencia intra-anual con un claro pico en mayo, relacionado con el ciclo biológico estacional de estas especies. Así y todo, los datos del primer decenio del siglo XXI revelaron diferencias entre la plataforma y el talud, porque algunos parámetros aumentaron significativamente con el tiempo en el primer caso, pero no siguieron ninguna tendencia en el segundo. Estas diferencias quedaron bien reflejadas en los Semáforos, demostrando su utilidad en reflejar las transiciones ecológicas.

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

We investigate the effects of the Columbretes Islands Marine Reserve (CIMR, Western Mediterranean) on the adjacent Palinurus elephas (Fabricius, 1787) fishery. After 9 to 12 yr of no-take protection there was a gradient of lobster density from the interior of the reserve up to a distance of about 4 km from its boundary. Catch and effort data were collected onboard commercial fishing boats in the fishery adjacent to the CIMR, and combined with catch per unit effort (CPUE) data from monitoring surveys conducted annually inside the reserve. Generalized additive (GAM) and linear (GLM) models were employed to examine the relationships of CPUE and catch per unit area (CPUA) as a function of distance to the reserve boundary. CPUE showed a significant non-linear decline with distance from the centre of the reserve, with a depression at the boundary followed by a plateau. This depression was caused by local depletion associated with concentration of fishing effort at the reserve boundary, while the plateau suggests that lobster export from the reserve is sufficient to maintain stable catch rates up to 1500 m from the boundary. Commercial catch and effort data were combined to estimate CPUA, which declined linearly with distance from the reserve. Analysis of recaptures of lobsters tagged and released inside the reserve indicates that the density gradient is caused by lobsters emigrating from the reserve, Sí

Protected lobster populations are expected to contribute to the replenishment of fished populations through increased egg production. We studied the reproductive biology and egg production potential of a population of the spiny lobster Palinurus elephas protected from fishing since 1990 in the Columbretes Islands Marine Reserve (western Mediterranean). An index of spawning potential was derived to compare egg production potential in the Reserve and in western Mediterranean exploited populations. Females' physiological maturity (ability to reproduce) and functional maturity (ability to mate and bear eggs) occurred at a carapace length (CL) of 76–77 mm. Males' physiological maturity occurred at a slightly larger size, 82.5 mm CL. In the Reserve, P. elephas' individual fecundity increases linearly with body size up to the females' maximum size, although maximum reproductive yield (eggs per body gram) was reached at intermediate sizes. Size-specific fecundity in the protected population was similar to that of lightly fished populations off Ireland and greater than that of western Mediterranean exploited populations. The female size class of 105–110 mm CL contributed most to egg production in the protected population and is well above the minimum landing size (MLS) for western Mediterranean fisheries. Newly mature females (below MLS) generate a very small fraction (1%) of the egg production from the Reserve. Given the pattern of exploitation in western Mediterranean fisheries, egg production potential depends more on the quantity than on the mean size and fecundity of the available females. The role of the greater availability of large males for mating in unfished populations is discussed in terms of the females' individual fecundity and mating success.

The fishery and some aspects of the biology of the Nephrops norvegicus populations in the Mallorca area have been studied. Data concerning length distributions and yields were obtained on board commercial trawlers. Modal sizes and their progression throughout the year were similar to those obtained in other areas of the western Mediterranean. Statistics of landings and their economic value, from 1986 to 1995, were also analysed. Important seasonal, as well as interannual, fluctuations were observed in both landings and market prices, Sí