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Early life stages of marine fish populations may be strongly affected by environmental factors. Changes in the physical environment or the availability of food resources could lead to stress-related physiological responses affecting larval fitness, growth and survival. In the present study, we determined, for the first time, amino acid composition (AAC), lipid, and carbohydrate content, as well as alkaline phosphatase and peroxidase activities in larvae from the European anchovy Engraulis encrasicolus. Fishes were caught in two different spawning areas of the Strait of Sicily, characterized by different environmental conditions, including a coastal upwelling with a lower temperature (Adventure Bank; 20.22±0.38°C) and a thermohaline front with a higher temperature (Maltese Bank 23.10±0.25°C). The results showed that the two groups of larvae, in their early life, had similar nutritional status. However, compared with the samples from the Maltese Bank, the specimens collected in the Adventure Bank area exhibited higher alkaline phosphatase activity, lower concentrations of aspartate plus asparagine, threonine, and arginine but a higher concentration of leucine, highlighting different patterns of amino acid metabolism. Collectively, these results indicated that AAC analysis could represent an additional valid tool to evaluate the link between physiological responses and environmental conditions at early life stages.

Understanding drivers of fish maturity are essential to predict the productivity, stability, and resiliency of exploited populations. In terms of horse mackerel (Trachurus trachurus), in the eastern Atlantic Ocean and the Mediterranean Sea, size at maturity estimates date back to the 1940s and throughout its range. However, many older estimates may not reflect current maturity rates. This is because past methods were imprecise, or environmental or fishing effects may change maturity rates, and some stock areas have been overlooked. To address this data gap for the Central Mediterranean Sea, female horse mackerel size at maturity was estimated for two areas: the Strait of Sicily and the Tyrrhenian Sea. All ovaries were assigned a reproductive phase based on macroscopic methods, and the reliability of this method (94%) was validated with a microscopic method (i.e., gonad histology). Although the collected females exhibited similar condition, in terms of total body weight at a given length, as well as similar gonad-somatic indices, the size at median maturity in the Strait of Sicily was smaller (161 mm total length [TL]) than in the Tyrrhenian Sea (176 mm TL). Future sampling in a series of years with contrasting levels of productivity may help identify whether this is a broad latitudinal trend, or due to specific oceanographic drivers, such as estuarine outflow into the Tyrrhenian Sea or upwelling in the Strait of Sicily. Meanwhile, resource assessments should consider that these two areas represent two phenotypic stocks.

Understanding drivers of fish maturity is essential to predict the productivity, stability, and resiliency of exploited populations. Size at maturity for European sardine (Sardina pilchardus) in the Central Mediterranean Sea has never been published within rigorous peer review process. In the past, stock assessment working groups in the Mediterranean requested such information; however, the size at which 50% of the fish population reaches the sexual maturity (L50) often received weak estimates based on a single or few years of observation, which do not necessarily reflect the whole stock. To address this data gap for the Central Mediterranean Sea, the present research estimated size at maturity of European sardine in the Strait of Sicily. In the study period (2009–2017), sampled individuals exhibited significant differences in size range as well as in body condition and reproductive effort. Data also permitted a clear identification of the spawning season, starting in September–October and ending in March–April the following year. Along the analyzed period, the size at first maturity ranged from 108 to 124 mm (total length) for females and from 102 to 122 mm for males. Significant differences were recorded among genders and years. Moreover, a goodness-of-fit measure was proposed to assess the robustness and reliability of L50 estimates, and thus selecting those that minimize the fitting-associated errors. Finally, results suggested that the low proportion of immature individuals in the samples represents the main source of bias in L50 estimation and possible solution was also proposed.

Simple Summary Wide fluctuations in abundance arising from variations in reproductive success are characteristic of many marine fish populations, including several pelagic fish species. The European anchovy is an economically and ecologically important resource, representing one of the most abundant species of the total Mediterranean fishery production. According to recommendations by the European Union, management plans should improve estimates of model parameters or biomass evaluation to provide a sustainable stock exploitation. The proportion of females spawning per day is one of the main parameters, including ichthyoplankton methods, for spawning biomass evaluation and is usually assessed by the postovulatory follicle (POF) method. Because of POF resorption rate is species-specific and influenced by residence temperature, the application of this method needs validation for species and area. This manuscript aimed to evaluate the resorption rate of postovulatory follicles in European anchovy in the central Mediterranean Sea, describing each degeneration stage based upon its histological features and estimating the duration of each POF stage in relation to water temperature experienced by the target species during the spawning peak. The provided results should allow for methodological advances in estimating the spawning biomass and in studying of reproductive output fluctuations, particularly for sustainable exploitation purposes. Abstract Accurate stock assessment estimates of fish resources are essential in fishery management. Wide fluctuations in abundance arising from variations in reproductive success are characteristic of many marine fish populations, including multiple spawner species. The proportion of females spawning per day is crucial in the application of egg production methods for spawning biomass evaluation and, usually, is assessed by postovulatory follicle (POF) method. Describing each degeneration stage of POF based upon its histological features allows for obtaining an aging key for postovulatory follicles. The commercially valuable European anchovy (Engraulis encrasicolus) was selected as a case study, which breeds during the summer in temperate waters (24 °C–25 °C). A collection of ovary slides, sampled in the central Mediterranean Sea during the spawning peak, provided a 24 h cycle coverage. These observations allowed us to evaluate the duration of each POF stage at water temperature experienced by anchovy in the study area. Present results demonstrated the POF degeneration progress at a faster rate than reported by previous investigations, carried out in cooler oceanic waters. Furthermore, the present study displayed the presence of two anchovy spawning cohorts sampled along a 24-h cycle. Therefore, this study not only provides useful insight for more accurate POF degeneration evaluation in temperate waters, but also suggests that current estimates should be complemented with validation studies according to different temperature regimes.

In this study we consider the applicability of Bergmann’s rule to the populations of small pelagic fish species in the Mediterranean Sea. Under Bergmann’s rule, body size increases with decreasing temperature and increasing latitude. Although this macroecological pattern in body sizes is well established for many taxa of endotherms and ectotherms, it does not remain universal, and the proposed mechanisms underlying it are multiple and still lack consensus. Here we explored the occurrence of geographical body size clines using measurements of average body sizes of 10 species collected in pelagic trawl hauls carried out during acoustic surveys in the Mediterranean Sea. Bergmann’s rule was evaluated by correlating body sizes with latitude and temperature for each species while accounting for potential confounding variables and sampling bias. For 5 species, namely anchovy, sardine, Atlantic chub mackerel, bogue and blue jack mackerel, we demonstrate that they follow Bergmann’s rule, with a decline in average body size by about 3.01, 3.43, 3.67, 3.82 and 3.76 % per 1°C of warming, respectively, although this did not translate with an increase in size with latitude. The adherence of these 5 pelagic fish to Bergmann’s rules strongly suggest that temperature is a major determinant of their body sizes and enables them to act as sentinel species for identifying the drivers and consequences of warming in the Mediterranean ecosystems

Size at first sexual maturity (L50) represents an important life-history trait that needs to be considered in the development of management measures as it provides fundamental information for avoiding the exploitation of younger individuals. L50 is known to display variability due to fishing pressure, geographical gradients, and environmental features. In this study, to investigate L50 variability among areas in the Mediterranean and Black Seas, maturity ogives of anchovies (Engraulis encrasicolus) were estimated by considering samples collected during the anchovy spawning period in the framework of the MEDiterranean International Acoustic Survey (MEDIAS) program. Anchovy size and sexual maturity data from several geographical subareas (GSAs), i.e., northern Spain, Gulf of Lion, Tyrrhenian Sea, Strait of Sicily, Adriatic Sea and Black Sea, were gathered according to a standard methodological protocol. Maturity ogives were estimated by a logistic regression considering total length, condition factor, sex and GSA. The obtained results showed a significant effect of the condition factor, in that fish in better condition reached maturity earlier, and the results also indicated differences in L50 values among the areas and between the sexes, with males reaching maturity at lower lengths than females. Even though the obtained L50 estimates are relative to the spawning period only, the variability observed at the Mediterranean basin scale highlights the importance of explicitly considering specific habitat characteristics when providing management advice based on an ecosystem approach for fisheries.

WOS:000744169400002; International audience; Acoustic surveys represent the standard fishery-independent method worldwide for evaluating the biomass and spatial distribution of small pelagic fish populations. Considering the peculiarities of the spatial behaviour of pelagic fishes, the efficiency of the survey design in determining their biomass and spatial distribution is related to the ability to capture the portion of the patches accounting for a larger part of the total biomass. However, the spatial structure of the patches could be strongly influenced by ecosystem characteristics as well as by changes in total biomass related to a density-dependent mechanism. This is of particular interest for anchovies and sardines, which are known for their wide fluctuations and high sensitivity to the environment. In this study, we analysed the efficiency of acoustic surveys targeting European anchovies (Engraulis encrasicolus) and European sardines (Sardina pilchardus) in 10 different areas of the Mediterranean Sea spanning three years of different biomass levels. Using the geostatistical coefficient of variation (CVgeo) of the average occurrence probability of high/medium density values, we showed different patterns in terms of survey design efficiency among areas and species. Anchovies usually showed a lower CVgeo than sardines in the Alboran Sea. In 4 out of 20 cases, CVgeo values showed a consistent decrease with increasing biomass, while in the remaining cases, the CVgeo did not follow any clear pattern, suggesting the presence of important environmental effects. Higher survey design efficiency was found in highly productive sectors influenced by river run-off, allowing us to hypothesize that higher productivity along with the presence of well-localized enrichment mechanisms could favour a spatially consistent distribution and coherent organization of fish populations, leading to higher precision estimates with a given transect design. While most surveys displayed CVgeo close to 10% or less even at low biomass, indicating generally good performances of the survey design, a few areas exhibited higher CVgeo, yielding a potential need to decrease the intertransect distance, always keeping in mind that any survey should be as synoptic as possible.

The bluefin tuna, Thunnus thynnus, is a highly migratory and long-living fish at the top of the pelagic food web. As top predator, it plays a key role in the stability of marine food webs by exerting top-down control on its prey. The diet composition of bluefin tuna varies in relation to its growth, seasons and migratory patterns, making it difficult to evaluate spatial and temporal effects. This latter aspect is further complicated to be determined during the first months of life, when T. thynnus specimens have a rapid growth rate leading to changes in the trophic status. In this study, the potential collagen-related effects on δ15N and δ13C values were evaluated on the whole spine of adult tuna specimens collected in the central Mediterranean Sea. Obtained results showed non-significant differences between extracted and non-extracted collagen samples for δ15N in whole spine, allowing adopting the isotopic analysis both for annuli in the spine section of adults and for younger specimens, whose spine size does not permit the collagen extraction. Specifically, isotopic analysis of whole spine of the young of the year specimens, showed a rapid change in δ15N values with length, following an exponential model. For older specimens, δ15N values were higher and varied around a plateau, likely due to a higher specificity in the choice of prey and/or to change in the geographical location. Such variability was also mirrored in annuli of spines sections of adult tunas. As far as δ13C values are concerned, a strong collagen-related effect was evidenced, likely highlighting the influence of lipids. Consequently, δ13C analysis may be used only on adult specimens where collagen extraction is possible. This research also showed how isotopic analysis of both whole sample and sequence of annuli in the cross-section of dorsal spine might produce isotopic profiles useful to detect specific trophic dynamics along the bluefin tuna growth.

The study of small pelagic fish by hydroacoustic methods in the Mediterranean Sea began in the Adriatic in the 1950’s. Since 2009, internationally coordinated, extensive, regular surveys have been conducted in the framework of the MEDIAS - Mediterranean International Acoustic Surveys – action, under the EU Data Collection Framework, to provide inputs for the management of small pelagics, particularly European anchovy (Engraulis encrasicolus) and European sardine (Sardina pilchardus). The surveys cover EU Mediterranean waters and monitor the distribution and abundance of small pelagic species using a common protocol. The hydroacoustic surveys, historically conducted by each Country separately, have since been standardized and harmonized. This is a review of the evolution of the surveys from the beginning up to the present and discusses the future prospects. It reports the historical time series of anchovy, sardine and other small pelagics in different areas and describes the spatial and temporal distribution of small pelagic species in decadal maps of the major areas of their distribution in the European Mediterranean Sea. Furthermore, it discusses the use of MEDIAS data for stock assessment purposes, the collection of auxiliary information for an ecosystem-based management approach, the need for further standardization and future challenges.

Most of the studies carried out in the past on economically important fish species rely on single species approach. Ecosystem dynamics are characterized by complex interaction among species, sharing common habitat needs and thus forming characteristic assemblages. The analysis of spatio-temporal variability of fish community, coupled to the analysis of spatial indices, provides a synthetic view of the fish community status evidencing, if any, the way a community changes. Such considerations drive also to the development of ecosystem-based fishery management paradigm. In the present study changes in pelagic fish community structure in an upwelling ecosystem of the central Mediterranean Sea during the last 10 years was analysed, by focusing the attention on the five most abundant small pelagic species: Engraulis encrasicolus, Sardina pilchardus, Sardinella aurita, Trachurus trachurus and Boops boops. Our results evidenced a quite stable community structure, characterized by spatial occupation strongly driven by ecosystem characteristics and modulated according to specie-specific behaviour. Obtained results lead us to hypothesize that the observed stability of community could be linked to the presence of different environments leading to efficient space partitioning and resources utilization among species.

The study of the relationships among environmental factors, primary production, zooplankton community, and feeding behavior of fish species represents a key aspect to obtain a deeper knowledge of biological processes acting at ecosystem level. In this context, oceanographic data and biological samples were collected in two different surveys, carried out during late June 2011 and early July 2015 in the Strait of Sicily (Central Mediterranean Sea). Differences in abundance, biomass, and assemblage structure of zooplankton and anchovy (Engraulis encrasicolus Linnaeus, 1758) population were observed between the two surveys. Still, zooplankton biomass was significantly correlated to longitude, chlorophyll a recorded during the surveys (as a proxy of primary production), and oxygen concentrations. Such differences affected the isotopic composition of anchovy, which showed changes in δ15N and δ13C values between the two surveys. Mixing models identified different contributions of food sources in the two sampling periods, i.e., major consumption on large copepods and euphausiids in 2015 with respect to 2011, which was consistent with a greater availability of these preys in the environment in 2015. The obtained results evidenced that E. encrasicolus may be affected by any environmental change that influences the plankton community, which is the basis of the diet of these fishes. Such findings highlighted the importance to further investigate the trophic relationships among different compartments of the food web, as well as the possible environmental influences, in order to obtain a more complete picture of ecosystem functioning and also in the light of an ecosystem-based approach to fisheries management.

The study presents the biomass and spatial distribution of Sardinella aurita in the Libyan, Maltese and southern Sicily waters, estimated during four acoustic surveys in summer 2008 and 2010. Strong differences in terms of both spatial distribution and total biomass between years and areas were found, with higher total biomass in 2010 than in 2008 in both southern and northern areas of the central Mediterranean. Habitat suitability and changes in the spatial dynamics of round sardinella among areas and years are then explored in relation to total biomass variation and environmental factors. The area of presence of S. aurita increased in the Maltese and Sicilian waters in 2010 with respect to 2008, while most of the total biomass observed in the two years occupied the same proportion of the continental shelf in Libyan waters. The link between environmental conditions and S. aurita area of presence and aggregation was investigated by means of generalized additive models (GAM). The application of GAM singled out the key role of depth and temperature in driving higher round sardinella aggregations, as they were able to explain in both years about the 48% of total deviance in the case of strictly positive values. Favourable habitat for round sardinella was found in waters shallower than 60 m depths, with a clear peak around 40 m depth. Favourable temperature values were above 22°C for presence/absence case and above 24°C when GAM was applied on strictly positive values. Overall S. aurita biomass and distribution were discussed in the light of the classical models proposed to describe the fish spatial dynamics in relation to an increase in total biomass.

Coccolithophore were collected and analyzed at 10 stations during summer 2010, from coastal and offshore areas off the eastern Libyan coast (southern Mediterranean Sea). The results were compared with oceanographic data. Total coccosphere concentrations, associated with nutrient-depleted stratified waters, show good correlation with the summer data from the central and eastern Mediterranean sites. K-strategist taxa dominate the surface/intermediate water, while F. profunda is more abundant in the deep photic zone. The Canonical Correlation Analysis reveals that the distribution of coccolithophore taxa is influenced by environmental parameters: K-strategist taxa are related to nutrient-depleted surface/intermediate waters, whereas lower photic zone taxa are influenced by the development of a Deep Chlorophyll Maximum and high salinity values, well below the thermocline. Finally, the occurrence of 3 clusters above 50m, between 50 and 100m, and below 100m depth can be detected. These results confirm that a vertical species zonation, as a typical feature of low-middle latitude, characterizes the eastern Libyan coast, where the holococcolithophores represent one of the most important features of coccolithophore production during summer. The distribution of F. profunda matches the depth of the Deep Chlorophyll Maximum layer, once again confirming its use as a proxy of Deep Chlorophyll Maximum development and paleoproductivity estimates.

The Atlantic horse mackerel ( Trachurus trachurus ) is a semi-pelagic fish species with a wide geographical distribution and commonly found on the continental shelf. In recent years, the species has received some attention due to its ecological role in pelagic food webs. Stable isotope of nitrogen and carbon (δ 15 N and δ 13 C) and Stomach Content Analysis (SCA) of T. trachurus were adopted as tools to provide necessary knowledge on its feeding habits in the Strait of Sicily. The strong correlation found between δ 15 N and δ 13 C values with body length, together with significant ontogenetic shift evidenced by SCA, could be associated to changes in food availability, which in turn is triggered by environmental conditions. Spatial distribution of T. trachurus in the study area, mainly for small and medium size specimens, is linked to lower temperature, salinity and Photosynthetically Active Radiation (PAR sat ) values with higher aggregations on the Adventure Bank (i.e., an area characterized by periodic upwelling events). Larger size specimens mostly inhabited shallower waters characterized by higher temperature, salinity and PAR values, typical of the central-eastern part of the study area. Our results support the hypothesis that feeding behavior of T. trachurus is strictly linked to environmental factors (i.e. chiefly oceanographic conditions of the water column and day duration) that in turn influences the distribution of its prey. Findings can supply knowledge needed for improving fish stock management and promoting plans able to take into account also local ecosystem analysis.

The flux (Φ) of mercury (Hg) at the sediment-seawater interface was investigated in Augusta Bay (southern Italy) where uncontrolled industrial discharge from one of the most important chlor-alkali plant in Europe has caused significant negative effects on the environment. Hg fluxes were measured by the deployment of in-situ benthic chamber. The obtained value of 1.3 kmol y −1 clearly emphasizes the role of the sediments as source of Hg for the overlying water column. Moreover, Hg concentrations in the outflowing bottom waters were measured to estimate the export of this pollutant from Augusta Bay to the open sea. The calculated value of 0.54 kmol y −1 , corresponding to ∼4% of the anthropogenic input of Hg from coastal point/diffuse sources to the Mediterranean Sea (12.5 kmol y −1 ; Rajar et al., 2007; UNEP-MAP, 2001), assigns this area a crucial role in the Hg inventory of the entire Mediterranean basin. Finally, a consistent and robust mass balance for Hg in Augusta Bay was provided by combining the obtained data with Hg fluxes at seawater-atmosphere interface.

Trophic ecology of adults of European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) was examined and compared among various regions of central Mediterranean Sea. Carbon and nitrogen stable isotope analyses (delta C-13 and delta N-15) were adopted as a tool to determine changes in feeding behaviour of adults of sardines and anchovies. In the study period (summer) a clear geographical pattern was recognized in the isotopic composition of both species, with an increasing trend northward. The highest variations in isotopic signal were linked to the geographical positions of the samples and, especially, between pairs of areas: South Sicily/South Campania and Gulf of Gaeta/South Elba. Higher isotope values were found in the anchovies and sardines caught in northern Tyrrhenian Sea, while lower values were mostly estimated in the southern region. Higher carbon and nitrogen isotopes may reflect a more coastal behaviour of both species, being C-13-enriched source from benthic primary producers in addition to phytoplankton. Variations in the nitrogen isotope ratio may reflect not only differences in the trophic level of prey species, but also variations in the baseline level of food webs. Our results support the hypothesis that feeding behaviour of both species is directly or indirectly influenced by local factors, or by resource partitioning based on zooplankton size. Findings can supply knowledge needed for improving fish stock management and promoting plans able to take into account also local ecosystem analysis. (C) 2016 Elsevier Ltd. All rights reserved.

Fishery production is highly dependent on fish growth and environmental factors; primary production and temperature are the two most important variables affecting almost all biological rates, especially individual growth or population production rate. The growth of European anchovy, Engraulis encrasicolus, was compared between two populations inhabiting different ecosystems: the Tyrrhenian Sea, characterized by riverine inputs and the Strait of Sicily, an oligotrophic area. The effects of habitat conditions on growth was also evaluated using literature data on other of European anchovy populations. Water temperature was confirmed to be a determinant factor for anchovy growth at the species level positively affecting the length at age-1. On the contrary, a negative relationship was found between chlorophyll-a and the length at age-1. These findings suggested that size at age-1 is strongly dependent on habitat conditions. The age structure differed significantly between the two populations, with the Tyrrhenian stock dominated by age-1 fish.

Concentrations of Hg were determined in tissues (muscle, heart, kidney, lung and liver) of two cetacean species (Stenella coeruleoalba and Tursiops truncatus) stranded along the Italian coasts during the period 2000–2009 and compared with those previously reported by other authors from different areas of the Mediterranean basin. The highest concentrations of Hg were found in liver samples of both species (8.4-1752 mg·kg−1 dry weight for S. coeruleoalba and 9.6-1404 mg·kg−1 d.w. for T. truncatus). Statistically significant dissimilarities of Hg concentrations were recorded in muscle and liver tissues of S. coeruleoalba stranded in different geographical areas of the Mediterranean Sea as apparent direct response to uneven impacts of Hg pollution in the basin. A noteworthy outcome was that cetaceans stranded on the French coasts showed significantly higher levels of Hg contamination than those from other Mediterranean areas while the eastern part of the basin evidences the lowest Hg concentrations i...

Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea: the Strait of Sicily (upwelling area) and the North Aegean Sea (continental shelf area, influenced by freshwater). Although the biomass of anchovy and sardine presented high interannual variability in both areas, the location of the centres of gravity and the main spatial patches of their populations were very similar between years. The size of the patches representing the dominant part of the abundance (80%) was mostly ecosystem- and species-specific. Occupation (area of presence) appears to be shaped by the extent of suitable habitats in each ecosystem whereas aggregation patterns (how the populations are distributed within the area of presence) were species-specific and related to levels of population biomass. In the upwelling area, both species showed consistently higher occupation values compared to the continental shelf area. Certain characteristics of the spatial distribution of sardine (e.g. spreading area, overlapping with anchovy) differed substantially between the two ecosystems. Principal component analysis of geostatistical and spatial indicators revealed that biomass was significantly related to a suite of, rather than single, spatial indicators. At the spatial scale of our study, strong correlations emerged between biomass and the first principal component axis with highly positive loadings for occupation, aggregation and patchiness, independently of species and ecosystem. Overlapping between anchovy and sardine increased with the increase of sardine biomass but decreased with the increase of anchovy. This contrasting pattern was attributed to the location of the respective major patches combined with the specific occupation patterns of the two species. The potential use of spatial indices as auxiliary stock monitoring indicators is discussed.

A number of scientific papers in the last few years singled out the influence of environmental conditions on the spatial distribution of fish species, highlighting the need for the fisheries scientific community to investigate, besides biomass estimates, also the habitat selection of commercially important fish species. The Mediterranean Sea, although generally oligotrophic, is characterized by high habitat variability and represents an ideal study area to investigate the adaptive behavior of small pelagics under different environmental conditions. In this study the habitat selection of European anchovy Engraulis encrasicolus and European sardine Sardina pilchardus is analyzed in two areas of the Mediterranean Sea that largely differentiate in terms of environmental regimes: the Strait of Sicily and the North Aegean Sea. A number of environmental parameters were used to investigate factors influencing anchovy and sardine habitat selection. Acoustic surveys data, collected during the summer period 2002–2010, were used for this purpose. The quotient analysis was used to identify the association between high density values and environmental variables; it was applied to the entire dataset in each area in order to identify similarities or differences in the “mean” spatial behavioral pattern for each species. Principal component analysis was applied to selected environmental variables in order to identify those environmental regimes which drive each of the two ecosystems. The analysis revealed the effect of food availability along with bottom depth selection on the spatial distribution of both species. Furthermore PCA results highlighted that observed selectivity for shallower waters is mainly associated to specific environmental processes that locally increase productivity. The common trends in habitat selection of the two species, as observed in the two regions although they present marked differences in hydrodynamics, seem to be driven by the oligotrophic character of the study areas, highlighting the role of areas where the local environmental regimes meet ‘the ocean triad hypothesis’.

Five sperm whales (Physeter macrocephalus) stranded along the Italian coast between 2007 and 2009 were analysed for concentrations of trace elements in the muscle, liver, kidney, lung, heart and skin. Essential elements (Zn, Cu, Fe, Cr, As, V and Se) show ranges of variability comparable with the limited data reported in the literature on this species and a homeostatic physiological control. Very low concentrations of nonessential elements (Hg, Cd and Pb) were detected in all tissues, suggesting a minor impact of these pollutants on the sperm whale populations of the Mediterranean Sea. This finding possibly reflects the pelagic lifestyle and deep-sea cephalopod diet of this group of giant cetaceans. In addition, this finding contrasts with the high levels of nonessential elements measured in many other species of cetaceans (e.g. Stenella coeruleoalba, Tursiops truncatus) stranded along Mediterranean coasts and which reflects significant coastal anthropogenic effects. The main result of this work is the compiled dataset which provides a preliminary target for conceptual understanding of the potential effects of open marine pollution on the Mediterranean sperm whale population. © 2013 Copyright Taylor and Francis Group, LLC.

The Augusta basin, located in SE Sicily (southern Italy), is a semi-enclosed marine area, labelled as a highly contaminated site. The release of mercury into the harbour seawater and its dispersion to the blue water, make the Augusta basin a potential source of anthropogenic pollution for the Mediterranean Sea. A mass balance was implemented to calculate the HgT budget in the Augusta basin. Results suggest that an average of ∼0.073 kmol of HgT is released, by diffusion, on a yearly basis, from sediments to the seawater, with a consequent output of 0.162 kmol y(-1) to coastal and offshore waters; this makes the Augusta area an important contributor of mercury to the Mediterranean Sea. Owing to the geographical location of the Augusta basin, its outflowing shelf-waters are immediately intercepted by the surface Atlantic Ionian Stream (AIS) and mixed with the main gyres of the eastern Mediterranean Sea, thus representing a risk for the large-scale marine system.