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Home    Εξέλιξη της αναλογίας φύλου και της παραγωγής αυγών στην τσιπούρα (Sparus aurata) κατά την διάρκεια πέντε αναπαραγωγικών περιόδων  

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Identifier 000411488
Title Εξέλιξη της αναλογίας φύλου και της παραγωγής αυγών στην τσιπούρα (Sparus aurata) κατά την διάρκεια πέντε αναπαραγωγικών περιόδων
Alternative Title Evolution of sex ratio and egg production in a population of gilthead seabream (Sparus aurata) over the course of five reproductive seasons
Author Καραμανλίδης, Δημήτριος Π.
Thesis advisor Κεντούρη, Μαρουδιώ
Reviewer Παυλίδης, Μιχαήλ
Μυλωνάς, Κωνσταντίνος
Abstract The aim of the present study was to examine the rate of sex reversal and the effect on egg production and quality parameters over 5 consecutive reproductive seasons. A hundred and seventeen fish of an initial average weight of about 50g produced at HCMR in 2009 were used. Temperature ranged between 18.2 and 20.8°C and natural photoperiod was used. In the years 2012-2016, the quality of the eggs was evaluated, recording daily fecundity and fertilization rates. Histological examination of fish gonads occurred in 5-10 individuals per tank in the years 2010, 2011 and 2012. The spawning period of gilthead seabream begun in December and ended from mid-June to late July in all the years studied with temperatures ranging not much above the natural spawning temperatures (16-18°C) until the summer. Mean daily relative fecundity ranged around 9,900-17,500eggs kg-1 female body weight, during the years studied, resulting in mean annual relative fecundity values of 1,700,000-3,100,000 eggs kg-1. The average fertilization rate ranged between 82 and 92% in the years 2012-2015 and decreased significantly in 2016 compared to 2013 and 2014. The average annual spawning days were consistently high and ranged from 131 to 191 days per spawning year. The sex ratio (M:F) of the studied broodstocks at the 2nd reproductive year (2012) was already heavily skewed towards females (0.55±0.08) with 64% of the males from the 1st reproductive year already having converted to females then the sex ratio stabilized in the stocks, being 1:5 M:F. A year after the ratio was brought back to 1:1 by the addition of males and removal of females, the male:female ratio again became heavily skewed toward females, being again ~1:5 M:F. The sex ratio of gilthead seabream changed significantly during the 2nd reproductive year, but remained stable thereafter. Egg quality remained high for 5 consecutive years and there was no influence of the observed sex ratio changes on the duration of the spawning season and the total annual fecundity of the broodstocks.
Language Greek
Subject Reproduction
Αναλογία φύλλου
Αναπαραγωγή
Issue date 2017-11-22
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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