Viene illustrata in questa nota l\u2019attuale condizione in cui si trova lo stato dell\u2019ambi... more Viene illustrata in questa nota l\u2019attuale condizione in cui si trova lo stato dell\u2019ambiente marino nell\u2019area del Canale di Sicilia immediatamente a ridosso della costa merdionale delle Sicilia dal Golfo di Gela alla costa iblea. Lo stato dell\u2019ambiente in oggetto viene valutato in base alla distribuzione di alcuni metalli in tracce normalmente ritenuti fra i pi\uf9 significativi per gli scopi prefissati, esaminati lungo la colonna d\u2019acqua e nei sedimenti superficiali di fondale. I risultati ottenuti, illustrati anche attraverso un\u2019indagine statistica multivariata, indicano un arricchimento superficiale della colonna d\u2019acqua in lantanio che pu\uf2 essere ascritto tanto ad un\u2019origine litogenica, quanto ad input antropico. Nei sedimenti al naturale raggruppamento fra elementi in tracce in tracce basato su analogie comportamentali di carattere geochimica sfugge il Ni che mostra di provenire da una fonte differente per la quale non si pu\uf2 esclude...
La conoscenza dei flussi energetici scambiati fra oceano e bassa atmosfera \ue8 un requisito util... more La conoscenza dei flussi energetici scambiati fra oceano e bassa atmosfera \ue8 un requisito utile per modellare e comprendere il sistema climatico e la dinamica degli oceani. L\u2019elevata difficolt\ue0 di effettuare misure in situ ed in continuo in ambiente marino induce spesso all\u2019utilizzo ausiliario di strumentazione satellitare. Nel presente lavoro \ue8 stato effettuato un confronto tra la stima dei flussi energetici superficiali valutati con dati provenienti da satellite e quelli ottenuti da misure in situ. In particolare, per il confronto, sono stati utilizzati i dati SST acquisiti dal satellite NOAA e i dati raccolti in situ dai sensori istallati a bordo della Nave Oceanografica Urania nel corso della Campagna Oceanografica effettuata nel periodo 3 Luglio \u2013 9 Agosto 2005 nel Mediterraneo Centrale. \uc8 stata utilizzata la Bulk Formula per stimare i flussi di calore sensibile e latente nelle medesime stazioni di campionamento. Nonostante la risoluzione spaziale dei...
Benthic foraminifera are very sensitive to oceanographic parameter variations, to which they rapi... more Benthic foraminifera are very sensitive to oceanographic parameter variations, to which they rapidly response through changes in the abundance and/or richness of their associations and in morphological variations of their shell. Many studies have used benthic foraminifera as bioindicators. We investigated recent benthic foraminiferal assemblages in the Gulf of Gela (Sicilian Channel, Mediterranean Sea), examining their relative abundance, specific richness and morphological abnormalities, to highlight a possible correlation with oceanographic features and the concentration of heavy metals in sediments. Sediment was sampled in summer 2006 using box corers in four stations at increasing distances from a point-source of industrial pollution. We performed hydrological characterization of the study area, grain size analysis and heavy metal determinations in sediments, and quantitative and qualitative analyses of benthic foraminifera. Heavy metal analyses highlighted very high mercury and cadmium concentrations in the station nearest the pollution source, in which the Dominance index showed the minimum of population density. In conclusion, a positive correlation seems to exist between the abundance of foraminifera and the concentration of cadmium and mercury in the sedimen
The spatial stock complexity of marine fish species requires that population structure is taken i... more The spatial stock complexity of marine fish species requires that population structure is taken into account in fisheries management. The aim of this study was to determine whether the amino acid composition (AAC) of the adult fish allows the identification of subpopulations within the stock. During a cruise in November 2003 along the entire Mediterranean coast of Spain, individuals were collected of the following pelagic species: Sardina pilchardus, Sardinella aurita, Engraulis encrasicolus, Trachurus trachurus, Trachurus mediterraneus, Scomber scombrus and Scomber colias. Individuals of S. pilchardus and E. encrasicolus were also collected from the waters of the Strait of Sicily in 2002 and 2003. The AAC of the fish eyes was seen to be species specific, and therefore, the differences in AAC among species may be based on inherited characters. Moreover, a clear differentiation was seen between the Spanish and Sicilian populations of S. pilchardus and E. encrasicolus. Furthermore, in the Spanish waters of the Mediterranean Sea, discriminant analysis revealed a substantial separation between the northern and southern subpopulations of S. pilchardus, S. aurita and E. encrasicolus. Temporal variations in AAC within species in each area were lower than the spatial variations observed among areas for each species, probably reflecting the influence on the AAC of the contrasting environmental characteristics of each area. Our results indicate that the ACC of the eyes in adult fish is a good tool for discriminating among subpopulations in pelagic marine fish species.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different... more Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.
Abstract The Common Fisheries Policy of the European Union aims to exploit fish stocks at a level... more Abstract The Common Fisheries Policy of the European Union aims to exploit fish stocks at a level of Maximum Sustainable Yield by 2020 at the latest. At the Mediterranean level, the General Fisheries Commission for the Mediterranean (GFCM) has highlighted the importance of reversing the observed declining trend of fish stocks. In this complex context, it is important to obtain reliable biomass estimates to support scientifically sound advice for sustainable management of marine resources. This paper presents a machine learning methodology for the classification of pelagic species schools from acoustic and environmental data. In particular, the methodology was tuned for the recognition of anchovy, sardine and horse mackerel. These species have a central role in the fishing industry of Mediterranean countries and they are also of considerable importance in the trophic web because they occupy the so-called middle trophic level. The proposed methodology consists of a classifier based on an optimized two layer feed-forward neural network. Morphological, bathymetric, energetic and positional features, extracted from acoustic data, are used as input, together with other environmental data features. The classifier uses an optimal number of neurons in the hidden layer, and a feature selection strategy based on a genetic algorithm. Working on a dataset of 2565 fish schools, the proposed methodology permitted us to identify the these three fish species with an accuracy of around 95%.
ABSTRACT Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at ... more ABSTRACT Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.
The complex interactions between surface circulation and coastal and continental shelf morphology... more The complex interactions between surface circulation and coastal and continental shelf morphology, as well as the presence of temperature and salinity gradients, make the Central Mediterranean an area characterized by high degree of ecosystem patchiness. The well-known effect of the physical environment in shaping community structure leads us to hypothesize the presence of differences in the pelagic fish community organization. Based on the analysis of specific environmental factors, nine sectors were identified and possible differences in the relative proportions of some key pelagic species were assessed by analysing the acoustic data collected during two surveys carried out in the summer period. The obtained results evidenced a clear separation between the northern (Strait of Sicily) and southern parts (Tunisian waters) of the study area, highlighting the strong effect of temperature on the proportions of some species. Furthermore, even if most of the variability in fish assemblag...
The combined use of field data on anchovy (Engraulis encrasicolus, Linnaeus, 1758) egg distributi... more The combined use of field data on anchovy (Engraulis encrasicolus, Linnaeus, 1758) egg distribution in the Central Mediterranean Sea on both sides of the Strait of Sicily (Sicilian–Maltese and Tunisian waters) and Lagrangian simulations were used to assess the pattern of connectivity between these two sub-areas as a result of spawning activity. The field data were collected during ichthyoplankton surveys carried out in summer 2008 and 2010. The simulation runs showed considerable (up to 20%) rates of particle exchange in both directions (from Tunisian to Sicilian–Maltese waters and vice versa). However, considering the typical high mortality rates of anchovy early stages, the actual larval exchange rates across the Sicily Strait are supposed to be significantly lower (<1%), supporting the hypothesis that the anchovy population sub-units in the Strait of Sicily can be considered as separate fish stocks for the evaluation of their optimum exploitation rates.
Accurate stock assessment estimates of fish resources are essential in fishery management. Wide f... more 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 b...
The bluefin tuna, Thunnus thynnus, is a highly migratory and long-living fish at the top of the p... more 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 δ 15 n and δ 13 c 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 δ 15 n 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 δ 15 n values with length, following an exponential model. for older specimens, δ 15 N 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 δ 13 c values are concerned, a strong collagen-related effect was evidenced, likely highlighting the influence of lipids. Consequently, δ 13 c 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 age determination in fast-growing short-living species, such as European anchovy (Engraulis e... more The age determination in fast-growing short-living species, such as European anchovy (Engraulis encrasicolus), has been widely recognized as a difficult task and bias introduced by readers leads to bias in reconstructing the population age structure. In this context, it is worth to note that age structure of fish population represents key information in fishery ecology and for stock assessment models. The uncertainty in estimating the age of the European anchovy by otolith reading is linked to the number of false-growth increments (checks) laid down before the annulus formation. While direct validation methods (e.g. mark-recapture, rearing, radiochemical dating) are difficult to implement specially for this short living species, the use of different indirect methods, supported by a coherent statistical approach, represents a robust and easier validation tool. A statistical modeling approach has been here adopted to assess the coherence of two well-known methods, namely Edge Analysis...
Natural gradients of pH in the ocean are useful analogues for studying the projected impacts of O... more Natural gradients of pH in the ocean are useful analogues for studying the projected impacts of Ocean Acidification (OA) on marine ecosystems. Here we document the in situ impact of submarine CO 2 volcanic emissions (CO 2 vents) on live shelled-pteropods (planktonic gastropods) species Creseis conica in the Gulf of Naples (Tyrrhenian Sea, Mediterranean). Since the currents inside the Gulf will likely drive those pelagic calcifying organisms into and out of the CO 2 vent zones, we assume that pteropods will be occasionally exposed to the vents during their life cycle. Shell degradation and biomass were investigated in the stations located within and nearby the CO 2 vent emission in relation to the variability of sea water carbonate chemistry. A relative decrease in shell biomass (22%), increase in incidence of shell fractures (38%) and extent of dissolution were observed in Creseis conica collected in the Gulf of Naples compared to those from the Northern Tyrrhenian Sea (control stations). These results suggest that discontinuous but recurrent exposure to highly variable carbonate chemistry could consistently affect the characteristic of the pteropod shells.
The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated w... more The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated with shared fisheries management. In an effort to resolve the species' stock dynamics, a genome-wide search for spatially informative single nucleotide polymorphisms (SNPs) was undertaken, by way of sequencing reduced representation libraries. An allele frequency approach to SNP discovery was used, combining the data of 555 larvae and young-of-the-year (LYOY) into pools representing major geographical areas and mapping against a newly assembled genomic reference. From a set of 184,895 candidate loci, 384 were selected for validation using 167 LYOY. A highly discriminatory genotyping panel of 95 SNPs was ultimately developed by selecting loci with the most pronounced differences between western Atlantic and Mediterranean Sea LYOY. The panel was evaluated by genotyping a different set of LYOY (n= 326) and from these 77.8% and 82.1% were correctly assigned to western Atlantic and Mediter...
Viene illustrata in questa nota l\u2019attuale condizione in cui si trova lo stato dell\u2019ambi... more Viene illustrata in questa nota l\u2019attuale condizione in cui si trova lo stato dell\u2019ambiente marino nell\u2019area del Canale di Sicilia immediatamente a ridosso della costa merdionale delle Sicilia dal Golfo di Gela alla costa iblea. Lo stato dell\u2019ambiente in oggetto viene valutato in base alla distribuzione di alcuni metalli in tracce normalmente ritenuti fra i pi\uf9 significativi per gli scopi prefissati, esaminati lungo la colonna d\u2019acqua e nei sedimenti superficiali di fondale. I risultati ottenuti, illustrati anche attraverso un\u2019indagine statistica multivariata, indicano un arricchimento superficiale della colonna d\u2019acqua in lantanio che pu\uf2 essere ascritto tanto ad un\u2019origine litogenica, quanto ad input antropico. Nei sedimenti al naturale raggruppamento fra elementi in tracce in tracce basato su analogie comportamentali di carattere geochimica sfugge il Ni che mostra di provenire da una fonte differente per la quale non si pu\uf2 esclude...
La conoscenza dei flussi energetici scambiati fra oceano e bassa atmosfera \ue8 un requisito util... more La conoscenza dei flussi energetici scambiati fra oceano e bassa atmosfera \ue8 un requisito utile per modellare e comprendere il sistema climatico e la dinamica degli oceani. L\u2019elevata difficolt\ue0 di effettuare misure in situ ed in continuo in ambiente marino induce spesso all\u2019utilizzo ausiliario di strumentazione satellitare. Nel presente lavoro \ue8 stato effettuato un confronto tra la stima dei flussi energetici superficiali valutati con dati provenienti da satellite e quelli ottenuti da misure in situ. In particolare, per il confronto, sono stati utilizzati i dati SST acquisiti dal satellite NOAA e i dati raccolti in situ dai sensori istallati a bordo della Nave Oceanografica Urania nel corso della Campagna Oceanografica effettuata nel periodo 3 Luglio \u2013 9 Agosto 2005 nel Mediterraneo Centrale. \uc8 stata utilizzata la Bulk Formula per stimare i flussi di calore sensibile e latente nelle medesime stazioni di campionamento. Nonostante la risoluzione spaziale dei...
Benthic foraminifera are very sensitive to oceanographic parameter variations, to which they rapi... more Benthic foraminifera are very sensitive to oceanographic parameter variations, to which they rapidly response through changes in the abundance and/or richness of their associations and in morphological variations of their shell. Many studies have used benthic foraminifera as bioindicators. We investigated recent benthic foraminiferal assemblages in the Gulf of Gela (Sicilian Channel, Mediterranean Sea), examining their relative abundance, specific richness and morphological abnormalities, to highlight a possible correlation with oceanographic features and the concentration of heavy metals in sediments. Sediment was sampled in summer 2006 using box corers in four stations at increasing distances from a point-source of industrial pollution. We performed hydrological characterization of the study area, grain size analysis and heavy metal determinations in sediments, and quantitative and qualitative analyses of benthic foraminifera. Heavy metal analyses highlighted very high mercury and cadmium concentrations in the station nearest the pollution source, in which the Dominance index showed the minimum of population density. In conclusion, a positive correlation seems to exist between the abundance of foraminifera and the concentration of cadmium and mercury in the sedimen
The spatial stock complexity of marine fish species requires that population structure is taken i... more The spatial stock complexity of marine fish species requires that population structure is taken into account in fisheries management. The aim of this study was to determine whether the amino acid composition (AAC) of the adult fish allows the identification of subpopulations within the stock. During a cruise in November 2003 along the entire Mediterranean coast of Spain, individuals were collected of the following pelagic species: Sardina pilchardus, Sardinella aurita, Engraulis encrasicolus, Trachurus trachurus, Trachurus mediterraneus, Scomber scombrus and Scomber colias. Individuals of S. pilchardus and E. encrasicolus were also collected from the waters of the Strait of Sicily in 2002 and 2003. The AAC of the fish eyes was seen to be species specific, and therefore, the differences in AAC among species may be based on inherited characters. Moreover, a clear differentiation was seen between the Spanish and Sicilian populations of S. pilchardus and E. encrasicolus. Furthermore, in the Spanish waters of the Mediterranean Sea, discriminant analysis revealed a substantial separation between the northern and southern subpopulations of S. pilchardus, S. aurita and E. encrasicolus. Temporal variations in AAC within species in each area were lower than the spatial variations observed among areas for each species, probably reflecting the influence on the AAC of the contrasting environmental characteristics of each area. Our results indicate that the ACC of the eyes in adult fish is a good tool for discriminating among subpopulations in pelagic marine fish species.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different... more Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.
Abstract The Common Fisheries Policy of the European Union aims to exploit fish stocks at a level... more Abstract The Common Fisheries Policy of the European Union aims to exploit fish stocks at a level of Maximum Sustainable Yield by 2020 at the latest. At the Mediterranean level, the General Fisheries Commission for the Mediterranean (GFCM) has highlighted the importance of reversing the observed declining trend of fish stocks. In this complex context, it is important to obtain reliable biomass estimates to support scientifically sound advice for sustainable management of marine resources. This paper presents a machine learning methodology for the classification of pelagic species schools from acoustic and environmental data. In particular, the methodology was tuned for the recognition of anchovy, sardine and horse mackerel. These species have a central role in the fishing industry of Mediterranean countries and they are also of considerable importance in the trophic web because they occupy the so-called middle trophic level. The proposed methodology consists of a classifier based on an optimized two layer feed-forward neural network. Morphological, bathymetric, energetic and positional features, extracted from acoustic data, are used as input, together with other environmental data features. The classifier uses an optimal number of neurons in the hidden layer, and a feature selection strategy based on a genetic algorithm. Working on a dataset of 2565 fish schools, the proposed methodology permitted us to identify the these three fish species with an accuracy of around 95%.
ABSTRACT Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at ... more ABSTRACT Identification of the potential habitat of European anchovy (Engraulis encrasicolus) at different life stages in relation to environmental conditions is an interesting subject from both ecological and management points of view. For this purpose, acoustic data from different seasons and different parts of the Mediterranean Sea along with satellite environmental and bathymetry data were modelled using generalized additive models. Similarly, egg distribution data from summer ichthyoplankton surveys were used to model potential spawning habitat. Selected models were used to produce maps presenting the probability of anchovy presence (adults, juveniles and eggs) in the entire Mediterranean basin, as a measure of habitat adequacy. Bottom depth and sea surface chlorophyll concentration were the variables found important in all models. Potential anchovy habitats were located over the continental shelf for all life stages examined. An expansion of the potential habitat from the peak spawning (early summer) to the late spawning season (early autumn) was observed. However, the most suitable areas for the presence of anchovy spawners seem to maintain the same size between seasons. Potential juvenile habitats were associated with highly productive inshore waters, being less extended and closer to coast during winter than late autumn. Potential spawning habitat in June and July based on ichthyoplankton surveys overlapped but were wider in extent compared with adult potential habitat from acoustics in the same season. Similarities and dissimilarities between the anchovy habitats as well as comparisons with sardine habitats in the oligotrophic Mediterranean Sea and other ecosystems with higher productivity are discussed.
The complex interactions between surface circulation and coastal and continental shelf morphology... more The complex interactions between surface circulation and coastal and continental shelf morphology, as well as the presence of temperature and salinity gradients, make the Central Mediterranean an area characterized by high degree of ecosystem patchiness. The well-known effect of the physical environment in shaping community structure leads us to hypothesize the presence of differences in the pelagic fish community organization. Based on the analysis of specific environmental factors, nine sectors were identified and possible differences in the relative proportions of some key pelagic species were assessed by analysing the acoustic data collected during two surveys carried out in the summer period. The obtained results evidenced a clear separation between the northern (Strait of Sicily) and southern parts (Tunisian waters) of the study area, highlighting the strong effect of temperature on the proportions of some species. Furthermore, even if most of the variability in fish assemblag...
The combined use of field data on anchovy (Engraulis encrasicolus, Linnaeus, 1758) egg distributi... more The combined use of field data on anchovy (Engraulis encrasicolus, Linnaeus, 1758) egg distribution in the Central Mediterranean Sea on both sides of the Strait of Sicily (Sicilian–Maltese and Tunisian waters) and Lagrangian simulations were used to assess the pattern of connectivity between these two sub-areas as a result of spawning activity. The field data were collected during ichthyoplankton surveys carried out in summer 2008 and 2010. The simulation runs showed considerable (up to 20%) rates of particle exchange in both directions (from Tunisian to Sicilian–Maltese waters and vice versa). However, considering the typical high mortality rates of anchovy early stages, the actual larval exchange rates across the Sicily Strait are supposed to be significantly lower (<1%), supporting the hypothesis that the anchovy population sub-units in the Strait of Sicily can be considered as separate fish stocks for the evaluation of their optimum exploitation rates.
Accurate stock assessment estimates of fish resources are essential in fishery management. Wide f... more 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 b...
The bluefin tuna, Thunnus thynnus, is a highly migratory and long-living fish at the top of the p... more 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 δ 15 n and δ 13 c 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 δ 15 n 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 δ 15 n values with length, following an exponential model. for older specimens, δ 15 N 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 δ 13 c values are concerned, a strong collagen-related effect was evidenced, likely highlighting the influence of lipids. Consequently, δ 13 c 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 age determination in fast-growing short-living species, such as European anchovy (Engraulis e... more The age determination in fast-growing short-living species, such as European anchovy (Engraulis encrasicolus), has been widely recognized as a difficult task and bias introduced by readers leads to bias in reconstructing the population age structure. In this context, it is worth to note that age structure of fish population represents key information in fishery ecology and for stock assessment models. The uncertainty in estimating the age of the European anchovy by otolith reading is linked to the number of false-growth increments (checks) laid down before the annulus formation. While direct validation methods (e.g. mark-recapture, rearing, radiochemical dating) are difficult to implement specially for this short living species, the use of different indirect methods, supported by a coherent statistical approach, represents a robust and easier validation tool. A statistical modeling approach has been here adopted to assess the coherence of two well-known methods, namely Edge Analysis...
Natural gradients of pH in the ocean are useful analogues for studying the projected impacts of O... more Natural gradients of pH in the ocean are useful analogues for studying the projected impacts of Ocean Acidification (OA) on marine ecosystems. Here we document the in situ impact of submarine CO 2 volcanic emissions (CO 2 vents) on live shelled-pteropods (planktonic gastropods) species Creseis conica in the Gulf of Naples (Tyrrhenian Sea, Mediterranean). Since the currents inside the Gulf will likely drive those pelagic calcifying organisms into and out of the CO 2 vent zones, we assume that pteropods will be occasionally exposed to the vents during their life cycle. Shell degradation and biomass were investigated in the stations located within and nearby the CO 2 vent emission in relation to the variability of sea water carbonate chemistry. A relative decrease in shell biomass (22%), increase in incidence of shell fractures (38%) and extent of dissolution were observed in Creseis conica collected in the Gulf of Naples compared to those from the Northern Tyrrhenian Sea (control stations). These results suggest that discontinuous but recurrent exposure to highly variable carbonate chemistry could consistently affect the characteristic of the pteropod shells.
The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated w... more The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated with shared fisheries management. In an effort to resolve the species' stock dynamics, a genome-wide search for spatially informative single nucleotide polymorphisms (SNPs) was undertaken, by way of sequencing reduced representation libraries. An allele frequency approach to SNP discovery was used, combining the data of 555 larvae and young-of-the-year (LYOY) into pools representing major geographical areas and mapping against a newly assembled genomic reference. From a set of 184,895 candidate loci, 384 were selected for validation using 167 LYOY. A highly discriminatory genotyping panel of 95 SNPs was ultimately developed by selecting loci with the most pronounced differences between western Atlantic and Mediterranean Sea LYOY. The panel was evaluated by genotyping a different set of LYOY (n= 326) and from these 77.8% and 82.1% were correctly assigned to western Atlantic and Mediter...
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Papers by G. Basilone