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| Identifier |
000419590 |
| Title |
Διακυμάνσεις αναπαραγωγικών παραμέτρων του γαύρου (Engraulis encrasicolus, Linnaeus 1758) στο Βόρειο Αιγαίο |
| Alternative Title |
Variations in reproductive parameters of the anchovy (Engraulis encrasicolus, Linnaeus 1758) in the North Aegean |
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Author
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Μαρκάκης, Κωνσταντίνος Ε.
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Thesis advisor
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Κουμουνδούρος, Γεώργιος
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Reviewer
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Σωμαράκης, Στυλιανός
Γιαννουλάκη, Μαριάννα
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| Abstract |
European anchovy, (Engraulis encrasicolus [Linnaeus 1758]) is an important fisheries resource in the Mediterranean and the Hellenic Seas. The study of its reproductive biology will help to understand the fluctuations of its stocks and will improve their assessment and management. The aim of the present study was to investigate certain reproductive parameters of the species and their variability in the North Aegean Sea. Samples of adult fish were collected during the peak of the spawning period in June and July 2014 and 2016. Relative batch fecundity was measured with the hydrated oocytes method and the relative numbers of oocytes per oocyte stage in Day-1 females (females that had spawned ~ 24 hours before capture) was estimated by a method that combined the oocyte packing density theory with stereology. For the same individuals, the number of oocytes >300μm and the mean diameter of each oocyte were measured with the autodiametric method. Frequency distributions of oocyte diameters were constructed and the mean diameters of the largest 20 oocytes (L20) were calculated. The two independent methods (stereological and autodiametric) resulted in strongly and positively correlated estimates of the number of vitellogenic oocytes. In spite of the significant differences in environmental conditions (temperature, salinity, fluorescence) between years and/or regions and the marked difference in the spawning stock biomass of anchovy between 2014 (14000 t) and 2016 (40000 t), relative batch fecundity (eggs g-1), by the hydrated oocytes method, did not exhibit any significant difference between years and regions. Similarly, the relative number of oocytes >300μm, by the autodiametric method, and the relative oocyte numbers, total and by stage, by the stereological method, did not differ significantly between years and regions. The size of the most advanced group of oocytes (L20) decreased with temperature and increased with female size and food availability.
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| Language |
Greek |
| Subject |
Autodiametric method |
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Fecundity |
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Oocyte packing density |
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Stereology |
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Αυτοδιαμετρική μέθοδος |
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Γονιμότητα |
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Πυκνότητα πακεταρίσματος ωοκυττάρων |
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Στερεολογία |
| Issue date |
2018-11-23 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
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Type of Work--Post-graduate theses
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| Views |
302 |
Διακυμάνσεις αναπαραγωγικών παραμέτρων του γαύρου (Engraulis encrasicolus, Linnaeus 1758) στο Βόρειο Αιγαίο
