Dimitris Vafidis

University of Thessaly, Iolcus, Thessaly, Greece

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Publications (54)29.02 Total impact

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    Georgios Kazanidis, Alexios Lolas, Dimitris Vafidis
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    ABSTRACT: The reproductive cycle of the traditionally exploited sea cucumber Holothuria tubulosa was investigated in the Pagasitikos Gulf (39°18′457″N, 23°05′869″E) from June 2007 to July 2008. The study examined the microscopic characteristics of the gonads and was based on maturity index (MI) and oocytes’ size-frequency distribution. The reproductive cycle was found to be synchronous between sexes, following an annual pattern. The minimum MI values were recorded in December and January, marking the onset of the reproductive cycle. During the spring, MI increased due to gamete development and proliferation. Mature specimens were prominent in summer while spawning occurred between July and September. The maximum MI values were recorded in mid-autumn, when most specimens were at the postspawning stage. The oocytes’ size-frequency distribution showed analogous seasonal variability. The present findings are crucial for establishing an efficient management strategy for this commercial and ecosystem-engineering species, since its exploitation in Greek waters has not been under official control for more than a century. The authors propose a seasonal ban on the exploitation of the species from July to September and a minimum individual drained weight limit of 250 g.
    Turkish Journal of Zoology 04/2014; 38:306-315. · 0.41 Impact Factor
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    Georgios Kazanidis, Alexios Lolas, Dimitris Vafidis
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    ABSTRACT: The reproductive cycle of the traditionally exploited sea cucumber Holothuria tubulosa was investigated in the Pagasitikos Gulf (39°18′457″N, 23°05′869″E) from June 2007 to July 2008. The study examined the microscopic characteristics of the gonads and was based on maturity index (MI) and oocytes’ size-frequency distribution. The reproductive cycle was found to be synchronous between sexes, following an annual pattern. The minimum MI values were recorded in December and January, marking the onset of the reproductive cycle. During the spring, MI increased due to gamete development and proliferation. Mature specimens were prominent in summer while spawning occurred between July and September. The maximum MI values were recorded in mid-autumn, when most specimens were at the postspawning stage. The oocytes’ size-frequency distribution showed analogous seasonal variability. The present findings are crucial for establishing an efficient management strategy for this commercial and ecosystem-engineering species, since its exploitation in Greek waters has not been under official control for more than a century. The authors propose a seasonal ban on the exploitation of the species from July to September and a minimum individual drained weight limit of 250 g.
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    1st Pan-Hellenic Scientific Conference on Natural Resources Environmental Economics: Climate Change, Volos, Hellas, Abstract; 03/2014
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    ABSTRACT: Despite their scientific interest and high conservation value, marine caves of the eastern Mediterranean are poorly explored. Herein, a submerged cave from the Aegean Sea was surveyed through SCUBA diving and photoquadrats. A rich fauna of 65 taxa and 4 distinct benthic assemblages were identified. The biotic spatial heterogeneity observed was associated with the unique topography of the different cave sectors.
    40th CIESM Congress, Marseille, France; 11/2013
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    The Mediterranean Science Commission, 40th CIESM Congress, Marseille, France, Rapp. Comm. Int. Mer. Médit. 40, p809; 10/2013
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    ABSTRACT: The impact of shellfish farming on the water column nutrient concentration and the benthic community structure was investigated seasonally at a mussel farm (Mytilus galloprovincialis L.) of Maliakos Gulf (Eastern Mediterranean). In most cases concentration of nutrients and chl a at the farm site was lower than those observed at the control sites. Statistical analysis in concentration of all nutrients and chl a indicated significant interactions between sites and seasons, which in all cases were temporal. Furthermore, no significant interactions were found between sites and seasons for all sediment and benthic community parameters, except for Shannon–Wiener diversity index and species richness. The significant interactions detected in the biotic data were temporal. Analysis of similarity and similarity percentages analysis revealed a certain fluctuation of benthic macrofaunal community during the overall sampling year mainly due to temporal rather than spatial effects. Cluster analysis and multidimensional scaling ordination plot indicated the clearly separation of the farm site and the control sites in most of the seasons. K-dominance curves showed small difference in elevation and overlap indicating minimal difference in biological stress between the farm site and the control sites. All the above indicates that probably the farming of mussels was beneficial for the trophic status of Maliakos Gulf and that there was a minimal environmental stress caused by the shellfish farming for the surrounding benthic environment.
    Aquaculture International 10/2013; · 1.04 Impact Factor
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    ABSTRACT: 350 «έγκυρα» ερωτηματολόγια. Για την εξαγωγή των παραγόντων που επηρέασαν τους ερωτώμενους, ώστε να αποδώσουν χρησιμότητα στην υδρόβια γενετική ποικιλότητα εφαρμόστηκε Ανάλυση Κυρίων Συνιστωσών (PCA), με τη βοήθεια μιας πολυθεματική ερώτησης με 20 θέματα. Οι ερωτώμενοι κλήθηκαν να απαντήσουν σε πεντάβαθμη κλίμακα Likert για κάθε θέμα. Η ανάλυση σε κύριες συνιστώσες έδωσε 5 παράγοντες, που εξηγούν το 62,615 % της συνολικής μεταβλητότητας. Ο έλεγχος σφαιρικότητας του Bartlett ήταν ίσος με 1376,441 (β.ε=190, ρ=0,000). Ο δείκτης των Kaiser – Mayer – Olkin έχει τιμή 0,821. Η συνολική αξιοπιστία της κλίμακας είναι 0,873. Τα αποτελέσματα της PCA δείχνουν ότι οι πολίτες αντιλαμβάνονται και ιεραρχούν υψηλά τη συμβολή της υδρόβιας γενετικής ποικιλότητας στην προσαρμοστικότητα των ειδών στις διάφορες μεταβολές (κλιματολογικές αλλαγές κ.λπ.). Στη συνέχεια, με τη βοήθεια των κριτηρίων Mann-Whitney και Krustal-Wallis, εξετάστηκε αν τα κοινωνικοοικονομικά χαρακτηριστικά και οι απόψεις των ερωτώμενων σχετικά με την υδρόβια γενετική ποικιλότητα, έχουν στατιστικά σημαντική διαφορά ως προς τους παράγοντες που προέκυψαν από την PCA. Σύμφωνα με τα αποτελέσματα, τα κοινωνικοοικονομικά χαρακτηριστικά των ατόμων (επίπεδο μόρφωσης, επαγγελματική δραστηριότητα κ.λπ.) επιδρούν στον τρόπο που αντιλαμβάνονται οι πολίτες τη χρησιμότητα της υδρόβιας γενετικής ποικιλότητας και αποδίδουν αξία σε αυτή. Χαρακτηριστικά, τα άτομα που διαθέτουν μεταπτυχιακές σπουδές αντιλαμβάνονται καλύτερα τη χρησιμότητα της υδρόβιας γενετικής ποικιλότητας, ως προς τον πρώτο παράγοντα της PCA (προσαρμοστικότητα ειδών). 112 Πρακτικά 35ου Επιστημονικού Συνεδρίου της Ελληνικής Εταιρείας Βιολογικών Επιστημών Ναύπλιο, 23-25 Μαΐου 2013 In the present study attempted to identify factors that influence people to identify utility (and economic value) of aquatic genetic resources beyond that is associated with real use and their value in real markets. For this reason a face-to-face survey of 350 respondents randomly selected residents of Volos city was carried out. Principal Components Analysis was used as a tool for measuring different public perceptions and preferences with regard to importance of aquatic genetic resources. Specifically, for this reason respondents were asked to indicate on a five-point Likert scale (Not at all, Not Much, Fairly, Much, Very Much) for each topic their opinion for the importance of 20 reasons -utility of aquatic genetic resources. Reliability analysis of the question revealed that Cronbach-a was 0.873. The Kaiser-Meyer-Olkin (KMO) criterion for sampling adequacy was equal to 0.821 and the Bartlett's test of sphericity was equal to 1376.44 (with a P-value of 0.000). 0.873 The results of PCA indicate that the populations' ability to resistance, tolerance of climatic change and population productivity and fitness is the most important service provided by aquatic genetic diversity.Mann-Whitney and Krustal-Wallis criteria were used to compare differences between socioeconomic characteristic of respondents (education level, occupation etc) and their opinion about utility of aquatic genetic resources. For examples, the results of Mann-Whitney test indicate that the highly educated people are more able to distinguish impacts of aquatic genetic resources to population ability of resistance, tolerance in climatic change and its productivity. 113
    35th Scientific Conference of Hellenic Association for Biological Sciences, Nafplio, May 23-25, 2013; 05/2013
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    35th Scientific Conference of the Hellenic Society of Biological Sciences, Nauplium, Hellas, Poster; 05/2013
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    ABSTRACT: The population structure of marine fishes is often cryptic, due to limited knowledge about life history and ecological habitats. Understanding environmental stability is a challenge to retrieve possible structuring patterns responsible for dispersal and demographic habits. In the present study, a combination of genetic and phenotypic assessments was applied in order to investigate population structure of the saddled seabream, Oblada melanura in the Aegean Sea, eastern Mediterranean basin. Analyses of 6 microsatellite loci and 15 morphometric characters revealed that saddled seabream individuals differ among northern, southern and central Aegean populations. These observed boundaries may be related to the differentiated seascape of the Aegean Sea, suggesting that oceanographic factors are a significant stressor for population subdivision of the saddled seabream. Individual-based landscape genetic approaches and multivariate analysis of the morphometric characters suggest the presence of habitat-related limitations of saddled seabream dispersal potential. Molecular genetics and phenotypic analyses along with life history traits provide useful informative data for the management and conservation schemes applied for this species in the Aegean Sea. KEYWORDS: Oblada melanura • Microsatellite • Morphometrics • Aegean Sea • Population structure
    Aquatic Biology 03/2013; 18:69-80. · 1.45 Impact Factor
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    ABSTRACT: Five colonies of the rare pennatulacean Crassophyllum thessalonicae were recently collected from Thermaikos Gulf (north-east Mediterranean), which allowed a study of their biometry; accordingly, new features are added to the original description of the species. Based on these data the morphological characters that distinguish C. thessalonicae from its congeners are reviewed.
    Marine Biodiversity Records 12/2011; 4.
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    4th International Symposium “Hydrobiology – Fisheries”., Volos, Greece; 06/2011
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    4rd International symposium on hydrobiology and fisheries, Volos Greece; 06/2011
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    4rd International symposium on hydrobiology and fisheries, Volos, Greece; 06/2011
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    4rd International symposium on hydrobiology and fisheries, Volos, Greece; 06/2011
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    ABSTRACT: This study attempts to evaluate the status of the populations of bath sponges (species of the genera Spongia and Hippospongia) in the Aegean, combining historical sources dated before a series of disease outbreaks that occurred from 1986 on, unpublished data obtained during the recovery phase after the first incident, as well as a current survey of the main spongiferous beds in the area. The latter was implemented through an extensive sampling trip assisted by professional sponge fishermen, including 55 stations distributed in 17 Aegean islands. Our analysis of population and morphometric data exhibits regeneration potential for bath sponge stocks, yet highlights the contrast between their present status and that of historical times. Uniformity is not evident, as several populations retain high abundances, while simultaneously areas purportedly rich in bath sponges appear deprived. Small-scale environmental regimes in the Aegean are proposed as the shaping factors of this situation; however, the importance of additional elaborate studies and the implementation of an effective regulation scheme regarding their fisheries are stressed.
    Reviews in Fisheries Science 01/2011; 19(1):34-51. · 2.42 Impact Factor
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    10th Hellenic Symposium on Oceanography and Fisheries, HCMR, Athens, Greece; 01/2011
  • N Neofitou, D Vafidis, S Klaoudatos
    Aquaculture Environment Interactions 10/2010; 1(2):95-105. · 2.22 Impact Factor
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    ABSTRACT: The Atlanto-Mediterranean holothurian Holothuria tubulosa is among the conspicuous benthic invertebrates in the shallow sublittoral zone. It is an edible species, harvested at the Aegean Sea and utilized as fishing bait. Considering the lack of information for the Aegean populations, a one-year survey, based on monthly or semimonthly samples, was carried out focusing on population structure, allometric relationships and reproductive status of H. tubulosa stocks in Pagasitikos Gulf. Population density varied around 9.93 individuals/100 m2. This value was rather low compared with other studied Mediterranean populations of the species, possibly due to the scarcity of seagrass meadows in the area studied. All measured biometric characters showed high plasticity, and all the examined morphometric relationships followed negative allometry indicating a change to the shape of the animal's body as it grows. Holothurians’ length was a moderate predictor of biomass since r values reached 60%; in contrast a very strong relation was observed between drained and gutted weight. Size–frequency distribution analysis was unimodal with the exception of spring where a second mode of larger sized individuals appeared. The gonadosomatic index showed a single spawning season per year, in late summer; accordingly the reproductive cycle of the species showed a clear annual pattern which was highly correlated with the seasonal variations of temperature.
    Journal of the Marine Biological Association of the UK 07/2010; 90(05):895 - 901. · 1.13 Impact Factor
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    14th Hellenic Conference of Ichthyologists, pp 111-114, Piraeus, Hellas; 05/2010
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    ABSTRACT: The effect of shellfish farming on the water column was investigated seasonally at a longline mussel farm (Mytilus galloprovincialis L.) of Maliakos Gulf, between October 2007 and July 2008. Nitrite and phosphate values showed significant differences among sampling stations and seasons (p<0.05 and p<0.001, respectively). Furthermore, in most cases concentrations of all nutrients and chl a at the farm site was lower than those observed at the control site. This indicates that shellfish farming contributes to the reduction of the primary production of Maliakos Gulf and consequently to the risk of eutrophication.
    39 CIESM, Venice, Italy; 05/2010

Publication Stats

160 Citations
29.02 Total Impact Points

Institutions

  • 2007–2013
    • University of Thessaly
      • Department of Icthyology and Aquatic Environment
      Iolcus, Thessaly, Greece
  • 2004–2008
    • Aristotle University of Thessaloniki
      • Department of Zoology
      Thessaloníki, Kentriki Makedonia, Greece
  • 2000–2004
    • Fisheries Research Institute, Kavala
      Neapolis, East Macedonia and Thrace, Greece