Research Interests: Zoology, Biomass, Ecology, Fish Biology, Sex ratio, and 7 moreFemale, Animals, Male, Body Size, Fisheries Sciences, Sea Bream, and Oceans and Seas
The present work examines the size specific distribution of anchovy and sardine in the Aegean Sea (Eastern Mediterranean basin) during early summer. Data from pelagic trawl hauls, multivariate methods, certain satellite environmental data... more
The present work examines the size specific distribution of anchovy and sardine in the Aegean Sea (Eastern Mediterranean basin) during early summer. Data from pelagic trawl hauls, multivariate methods, certain satellite environmental data and area topographic characteristics were used in order to identify the parameters that could discriminate the spatial distribution of the juveniles and the adults, of both species.
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The biomass of Aegean Sea anchovy stock was estimated in June 2003 and June 2004 with the concurrent application of the Daily Egg Production (DEPM) and the Acoustic methods. Spawning stock biomass (SSB) based on the DEPM was 40042 t in... more
The biomass of Aegean Sea anchovy stock was estimated in June 2003 and June 2004 with the concurrent application of the Daily Egg Production (DEPM) and the Acoustic methods. Spawning stock biomass (SSB) based on the DEPM was 40042 t in 2003 and 22799 t in 2004. Stock biomass based on acoustics was 47838 t in 2003 and 46508 t
Research Interests: Zoology, Biomass, Ecology, Fish Biology, Sex ratio, and 7 moreFemale, Animals, Male, Body Size, Fisheries Sciences, Sea Bream, and Oceans and Seas
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ABSTRACT Acoustic survey data were combined with environmental features from satellite imagery to investigate the relationship between the spatial distribution of European sardine (i.e. acoustic data from June 2004 and 2005), of the Greek... more
ABSTRACT Acoustic survey data were combined with environmental features from satellite imagery to investigate the relationship between the spatial distribution of European sardine (i.e. acoustic data from June 2004 and 2005), of the Greek seas (Eastern Mediterranean basin). Generalized Additive Models were then applied in order to identify the link of sardine's presence with environmental variables. GIS techniques were applied to identify the geographical areas where this set of environmental parameters is met, implying the existence of potential sardine habitat in all Greek Seas and the Mediterranean basin. Keywords: acoustics, Aegean sea, mapping
... hcmr. gr; pap@ ath. hcmr. gr; amachias@ ath. hcmr. gr ARGYRIS KALLIANIOTIS Fisheries Research Institute, Nea Peramos, Kavala, Greece; akallian@ inale. ... Anchovy and sardine were described as multi-stanza groups, ie, split into... more
... hcmr. gr; pap@ ath. hcmr. gr; amachias@ ath. hcmr. gr ARGYRIS KALLIANIOTIS Fisheries Research Institute, Nea Peramos, Kavala, Greece; akallian@ inale. ... Anchovy and sardine were described as multi-stanza groups, ie, split into juveniles and adults. ...
Fisheries provide critical provisioning services,especially given increasing human population.Understanding where marine communities are declining provides an indication of ecosystems of concern and highlights potential conflicts between... more
Fisheries provide critical provisioning services,especially given increasing human population.Understanding where marine communities are declining provides an indication of ecosystems of concern and highlights potential conflicts between seafood provisioning from wild fisheries and other ecosystem services. Here we use the nonparametric statistic, Kendall's tau, to assess trends in biomass of exploited marine species across a range of ecosystems.The proportion of ‘Non-Declining Exploited Species’ (NDES) is compared among ecosystems and to three community-level indicators that provide a gauge of the ability of a marine ecosystem to function both in provisioning and as a regulating service: survey-based mean trophic level, proportion of predatory fish, and mean life span.In some ecosystems, NDES corresponds to states and temporal trajectories of the community indicators, indicating deteriorating conditions in both the exploited community and in the overall community.However differences illustrate the necessity of using multiple ecological indicators to reflect the state of the ecosystem.For each ecosystem,wed iscuss patterns in NDES with respect to the community-level indicators and present results in the context of ecosystem-specific drivers.We conclude that using NDES requires context-specific supporting information in order to provide guidance within a management framework.
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Spatial distribution and life history aspects of Pagellus bogaraveo in the eastern Ionian Sea were investigated using the data from 13 different studies carried out in the area from 1983 to 2010. The spatial patterns of the abundance,... more
Spatial distribution and life history aspects of Pagellus bogaraveo in the eastern Ionian Sea were investigated using the data from 13 different studies carried out in the area from 1983 to 2010. The spatial patterns of the abundance, biomass and mean size showed that the species inhabits the shallow waters of the shelf (<170 m depth) as juveniles up to a certain size (<180 mm total length, LT), moving to deeper waters of the slope (mainly 400–500 m depth) as adults. The spatial pattern of abundance indicated a continuous distribution of the species in deep waters, with hot-spot areas of high values, whereas in shallow waters distribution was more discontinuous, with higher concentrations of juveniles in estuaries and brackish waters. The study of biological aspects of the species revealed (1) a difference in the increase in mass between males and females, (2) protandrous hermaphroditism, accompanied by the presence of primary females and males that do not change sex, (3) a sex ratio in favour of females >250 mm LT, (4) the presence of hermaphrodites between 200 and 370 mm, (5) a long reproduction period from June to March, (6) a size at first maturity around 300 mm and (7) a diet composition of adults based mainly on fishes, and also on opportunistic behaviour in the food scarce environment of deep waters. The results suggest that the species' distribution and feeding strategies are the most appropriate for the oligotrophic eastern Ionian waters and that these conditions result in smaller sizes of the species in the east Mediterranean Sea compared to the west basin and the east Atlantic Ocean, with implications for the growth and reproductive biology of the species.
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Data from the MEDITS bottom trawl surveys in the Eastern Ionian Sea, covering a depth range of 28 to 845 m were analysed for the period 1998–2008. For each trawling location, environmental and geographical parameters were recorded, while... more
Data from the MEDITS bottom trawl surveys in the Eastern Ionian Sea, covering a depth range of 28 to 845 m were analysed for the period 1998–2008. For each trawling location, environmental and geographical parameters were recorded, while biomass, abundance, biodiversity and size-based metrics were estimated for the total megafaunal community, as well as for four taxonomic sub-communities (Osteichthyes, Chondrichthyes, Crustacea and Cephalopoda) which were expected to respond differently to environmental changes and fishing. In addition, biomass and abundance of ten species selected based on commercial interest, depth range and life history traits were explored, with particular emphasis on deep-sea species. Fishing effort data collected during the study period were analysed and showed a decreasing trend, mainly due to a decrease in the activity of static nets. The relation between the estimated parameters and environmental and spatial factors, as well as temporal (interannual) effects and the effect of fishing effort were explored using generalized additive models (GAMs). Results of GAMs showed that depth and location explained much of the variation in community metrics, probably reflecting mesoscale spatial features and species/communities requirements. Even though the different communities and species exhibited variant patterns in bathymetric and spatial distribution, some common aggregation patterns in productive areas were identified. Despite the relatively short time series, GAMs were effective in detecting increasing trends for several metrics; taking into account spatial factors further contributed to attributing the remaining deviance to temporal effects. These trends were partly explained by the observed decline of fishing effort, which is further supported by the fact that negative relations between several metrics and fishing effort were identified, for some of the selected communities and populations. Abundance, species richness and maximum length proved the most informative metrics concerning the effect of fishing. The current decline in fishing effort in the area seems to be a move in the right direction and should be complemented by additional measures aiming to prevent allocation of effort towards the deep sea. (Online publication December 19 2013)
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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... 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.
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Intraspecific variability in the characteristics of fish schools is often affected by the size of individuals. In this study, juvenile and adult sardine schools detected in five hydroacoustic surveys (2004–2008) in the North Aegean Sea... more
Intraspecific variability in the characteristics of fish schools is often affected by the size of individuals. In this study, juvenile and adult sardine schools detected in five hydroacoustic surveys (2004–2008) in the North Aegean Sea (eastern Mediterranean) were analysed in an effort to identify differences in a suite of school descriptors (i.e. positional, energetic, morphometric) and define the size at which schooling behaviour changed from juvenile to adult. Juveniles exhibited discrete schooling characteristics and microhabitat preferences compared to adult fish. Specifically, schools of juvenile sardines were smaller, more elongated and irregular than those of adults, they backscattered less energy and were located higher in the water column. Based on the length frequency distributions of experimental pelagic trawl catches, the length at which 50% of sardines shifted behaviour from juvenile school structure to the more typical adult school form was estimated at 10.7 cm. This length almost coincides with several ontogenetic changes in biology (i.e. first maturity, allometric change in the length–weight relationship and onset of phytoplankton consumption). Several size-dependent school features observed in this study are partly attributed to the higher feeding demands of juvenile fish and the need to avoid intraspecific competition and predation.