Ahmet Alp

Age and growth of the European catfish (Silurus glanis) in a Turkish Reservoir and comparison with introduced populations

The European catfish, Silurus glanis, is native to eastern Europe and western Asia and is among the largest freshwater fish in the world. Despite its increasing economic importance and its frequent introductions, the ecology and life-history of this species is poorly known due to the difficulty of sampling such a large species in large rivers and standing waters. Our study provides the first data on age and growth of this species in Turkish waters, where it is native. We report the length-weight relationships and age and size structure of this population, which were significantly different between females and males. A marginal increment analysis indicated that annulus formation occurred between May and June. The estimates of three growth functions (von Bertalanffy, logistic and Gompertz) are reported, with the von Bertalanffy growth providing a better fit and more realistic parameter estimates. Growth rates were significantly higher in males than in females and were overall higher compared to other native populations but similar to introduced populations of similar latitude.

Uzunçayır Baraj Gölü’ndeki Capoeta trutta (Heckel, 1843)’nın Üreme Biyolojisi

Calismada, surdurulebilir avcilik stratejilerinin belirlenebilmesi amaciyla, Uzuncayir Baraj Golu’ndeki Capoeta trutta ’nin ureme ozellikleri arastirilmistir. Balik ornekleri 2013 yilinin Ocak-Aralik aylari arasinda farkli ag goz acikliklarina (36-100 mm) sahip sade uzatma aglariyla aylik olarak yakalanmistir. Arastirma suresince Uzuncayir Baraj Golu’nden yakalanan 385 adet C. trutta bireyinin 218 adedini (%57.00) erkek, 167 adedini (%43.00) ise disi bireylerin olusturdugu ve populasyonun I-XII yas gruplari arasinda dagilim gosterdigi saptanmistir. GSI degerlerinin mayis ayinda maksimuma ulastigi, sperm ve yumurtalarini mayis-temmuz aylari arasinda biraktiklari tespit edilmistir. Yumurta caplari 0.30-1.07 mm arasinda degismistir. Fekondite-total boy ve fekondite-agirlik arasindaki iliskileri aciklayan denklemler sirasiyla; F= 29.708*TL-593.36 (N= 35, r= 0.27), F= 9.6448*W+5488.3 (N= 35, r= 0.38) olarak hesaplanmistir. C. trutta bireylerinin yas gruplarina gore yumurta veriminin 1362-15428 arasinda degistigi belirlenmistir. Eseysel olgunluk boyu disi bireylerde 20.77 cm, erkek bireylerde 19.35 cm olarak tespit edilmistir