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The effects of feeding frequency on growth performance, feed efficiency and size variation of juvenile Black Sea turbot, Psetta maxima were investigated. A factorial design of two feeding rates (ad libitum, n=240, weight=23.8 ±0.70 g and total length=11.0 ±0.09 cm; and 1% of bodyweight of fish per meal, n=240, weight=38.6 ±0.45 g and total length=13.0 ±0.03 cm) and three feeding frequencies (one meal in 2 days, one meal a day, two meals a day) with two replicates of each treatment combination were applied in this experiment. Feeding frequencies did not affect fish survival rates (P>0.05). The final body weight and specific growth rate (SGR) were higher in group one meal a day at both feeding rates. There were no significant differences the final body weight and SGR values among the groups (P>0.05). Similar responses were observed for condition factor, feed conversion ratio (FCR) and body weight increase (BWI), and the best FCR and BWI were obtained in the same group. The coefficient of variations (CV) in fish weight increased between initial and final weightings in all replicate groups. However, the CV of fish weight was not significantly affected by feeding frequency (P>0.05).In conclusion, growth performance, SGR and FCR were better in once-daily feeding, and it appears that under the conditions of this experiment, feeding once a day to satiation was sufficient for maximal growth. Journal of FisheriesSciences.comAydın et al., 5(1): 35-42 (2011) Journal abbreviation: J FisheriesSciences.com 36 Özet: Yemleme Sıklığının ve Yemleme Oranının Yavru Karadeniz Kalkan Balığının (Psetta maxima, Linneaus, 1758) Büyüme Performansına EtkilesiKaradeniz kalkanı, Psetta maxima yavrularında yemleme sıklığının, büyüme, yem değerlemdirme ve boy varyasyonuna etkileri araştırılmıştır. İki yemleme oranı (Doyana kadar, n=240, ağırlık=23.8 ±0.70 g ve boy = 11.0 ±0.09 cm; balık ağırlığının %1 kadar yem n=240, ağırlık = 38.6 ±0.45 g ve boy = 13.0 ±0.03 cm) ve üç yemleme sıklığı (iki günde bir yemleme, günde bir yemleme, günde iki kez yemleme) içeren iki tekerrürlü faktöriyel deneme oluşturulmuştur. Yemleme sıklığı yaşam oranını etkilememiştir (P>0.05). Deneme sonunda her iki yemleme seviyesinde günde bir kez yemlenen balıkların ağırlığı ve oransal büyümesi fazladır. En iyi yem dönüşüm oranı (YDO) ve ağırlık artışı aynı grupta gözlenmiştir. Deneme sonunda balık ağırlığı ve oransal büyüme (OB) acısında gruplar arasında önemli fark bulunmamıştır (P>0.05). Kondisyon faktörü, YDO ve ağırlık artışı yönünden de benzer durum söz konusudur. Balık ağırlıkları acısından görülen varyasyon katsayısı (VK) deneme sonunda başlangıca göre artmıştır. Bununla birlikte yemleme sıklığı VK yi önemli bir şekilde etkilememiştir (P>0.05). Sonuç olarak günde bir kez yemlenen balıkların büyüme performansı, OB ve YDO daha iyidir. Bu şartlarda günde bir kez doyana kadar yemlemek en iyi büyüme için uygundur.

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Turbot, Scophthalmus maximus, is a commercially important demersal flatfish species distributed throughout the Black Sea. Several studies performed locally with a limited number of specimens using both mitochondrial DNA (mtDNA) and microsatellite markers evidenced notable genetic variation among populations. However, comprehensive population genetic studies are required to help management of the species in the Black Sea. In the present study eight microsatellite loci were used to resolve the population structure of 414 turbot samples collected from 12 sites across the Black Sea. Moreover, two mtDNA genes, COI and Cyt-b, were used for taxonomic identification. Microsatellite markers of Smax-04 and B12-I GT14 were excluded from analysis due to scoring issues. Data analysis was performed with the remaining six loci. Loci were highly polymorphic (average of 17.8 alleles per locus), indicating high genetic variability. Locus 3/20CA17, with high null allele frequency (>30%), significantly deviated from HW equilibrium. Pairwise comparison of the F ST index showed significant differences between most of the surveyed sampling sites (P < 0.01). Cluster analysis evidenced the presence of three genetic groups among sampling sites. Significant genetic differentiation between Northern (Sea of Azov and Crimea) and Southern (Turkish Black Sea Coast) Black Sea sampling sites were detected. The Mantel test supported an isolation by distance model of population structure. These findings are vital for long-term sustainable management of the species and development of conservation programs. Moreover, generated mtDNA sequences would be useful for the establishment of a database for S. maximus.

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