Ramazan Yazıcı

Feeding ecology and prey selection of European perch, Perca fluviatilis inhabiting a eutrophic lake in northern Turkey

ABSTRACT Feeding habits and prey selection of European perch (Perca fluviatilis) were examined in Lake Ladik between November 2009 and October 2010. Stomach contents of 308 individuals ranging in size from 73 to 275 mm total length were analyzed and 55.2% were empty. The fullness index indicated that feeding intensity of this species was the highest in summer and the lowest in winter. European perch feeds on prey fish and macroinvertebrates. The most important food items were Scardinius erythrophthalmus and Perca fluviatilis, followed by chironomidae larvae. Diet composition and feeding habits varied seasonally and ontogenetically. Macroinvertebrates were only consumed by small individuals, while prey fishes were only eaten by large individuals. S. erythrophthalmus, P. fluviatilis, and Blicca bjoerkna were positively selected but their selection indexes were not statistically significant (p > 0.05). This prey selection is important for combating eutrophication. Abramis brama constitute 24.03% of all fish species in this lake; however, it was a negatively selected prey item (Va = −0.198, χ2 = 7.86, p < 0.05). Esox lucius, Squalius cephalus, Chondrostoma regium, and Carassius gibelio inhabiting this lake were not preferred by European perch. Cannibalism rate was 12.3%.

Reproduction Properties of Wels Catfish (Silurus glanis, L., 1758) Inhabiting Sıddıklı Reservoir

Bu calismada Siddikli Baraji’nda yasayan Yayin Baligi, Silurus glanis ’ nin bazi ureme ozellikleri (esey orani, ureme peryodu, yumurta capi ve fekondite) arastirilmistir. Eylul 2015- Agustos 2016 tarihleri arasinda Siddikli Baraji’nin farkli bolgelerinden toplamda 200 ornek yakalanmistir. Esey orani 0,88:1,00 (Disi: Erkek) olarak hesaplanmistir. Disi:Erkek orani beklenen 1,00:1,00 degerinden istatistiksel olarak farkli cikmamistir (χ2= 0,841, P>0,05). Gonadosomatik indeks degerlerine gore, Siddikli Baraji’ndaki Yayin baliklarinin ureme sezonunun Nisan-Haziran aylari arasinda oldugu belirlenmistir. Ortalama total fekondite ve yumurta capi sirasiyla 46343 yumurta/birey ve 1,758 mm olarak hesaplanmistir. Nisbi fekondite her bir kilogram balik agirligina karsi 13000 yumurta olarak belirlenmistir. Fekondite-boy ve Fekondite-agirlik arasinda kuvvetli iliskiler tespit edilmistir (r 2 >0,80).

Ladik Gölü (Samsun, Türkiye)’ndeki kızılkanat balığı (Scardinius erythrophthalmus L., 1758) populasyonunda en güvenilir yaş tayini yönteminin belirlenmesi

Ages estimated from scales, vertebrae, opercles, utricular (lapillus) and lagenar (asteriscus) otoliths of 260 rudd (Scardinius erythrophthalmus L., 1758) specimens captured from Lake Ladik in February and March 2010 were compared to determine the most reliable ageing method. Three readings were made for each bony structure by one reader. Mean ages were determined for all bony structures and precision of ages obtained from multiple readings was evaluated calculating percent agreement (PA), average percent error (APE) and coefficient of variation (CV). Due to the highest PA (71.71 %) and the lowest APE (2.71 %) and CV (3.56 %) values, it was concluded that lapillus is the most reliable bony structure for age determination in Lake Ladik population of this species. When lapillus ages were compared with other bony structures, the highest precision was found between lapillus and asteriscus age readings.

The determination of the most reliable ageing method for the rudd (Scardinius erythrophthalmus L., 1758) population in Lake Ladik, Samsun, Turkey

Ages estimated from scales, vertebrae, opercles, utricular (lapillus) and lagenar (asteriscus) otoliths of 260 rudd (Scardinius erythrophthalmus L., 1758) specimens captured from Lake Ladik in February and March 2010 were compared to determine the most reliable ageing method. Three readings were made for each bony structure by one reader. Mean ages were determined for all bony structures and precision of ages obtained from multiple readings was evaluated calculating percent agreement (PA), average percent error (APE) and coefficient of variation (CV). Due to the highest PA (71.71 %) and the lowest APE (2.71 %) and CV (3.56 %) values, it was concluded that lapillus is the most reliable bony structure for age determination in Lake Ladik population of this species. When lapillus ages were compared with other bony structures, the highest precision was found between lapillus and asteriscus age readings.

population in Lake Ladik, Samsun, Turkey.

Ages estimated from scales, vertebrae, opercles, utricular (lapillus) and lagenar (asteriscus) otoliths of 260 rudd (Scardinius erythrophthalmus L., 1758) specimens captured from Lake Ladik in February and March 2010 were compared to determine the most reliable ageing method. Three readings were made for each bony structure by one reader. Mean ages were determined for all bony structures and precision of ages obtained from multiple readings was evaluated calculating percent agreement (PA), average percent error (APE) and coefficient of variation (CV). Due to the highest PA (71.71 %) and the lowest APE (2.71 %) and CV (3.56 %) values, it was concluded that lapillus is the most reliable bony structure for age determination in Lake Ladik population of this species. When lapillus ages were compared with other bony structures, the highest precision was found between lapillus and asteriscus age readings.