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The objective of this study was to determine growth parameters, such as age–length and length–weight relationships, as well as condition factors and sex ratio, of the Carassius gibelio (Bloch, 1782) population in Lake Marmara (western region of Turkey), which is one of the most important fishing areas. Fish were caught on a monthly basis by gillnets and trammel nets (mesh size 10–50 mm) between March 2012 and February 2013. A total of 1058 specimens (809 females and 249 males) were examined. The female–male ratio was 1:0.31. The maximum age was determined as VI and V for females and males, respectively. The total length of females and males ranged from 10.0 to 27.5 cm and from 10.2 to 24.0 cm, respectively. Their weight varied from 17.1 to 378.4 g and from 17.7 to 244.9 g, respectively. Length–weight relationship parameters were a = 0.014 and b = 3.040 for females and a = 0.015 and b = 3.039 for males. Von Bertalanffy growth parameters of the C. gibelio population were as follows: L∞ = 35.86 cm, k = 0.189 year−1, t0 = −1.238 years. Minimum and maximum condition factors were 1.56 for females in October and 1.82 in May and 1.67 for males in September and 1.94 in January.

Bu çalışmada, dünyanın en istilacı 100 canlı türünden birisi olduğu ifade edilen ve özellikle endemik balık türlerinin varlığı açısından risk oluşturan sivrisinek balığı, Gambusia holbrooki türünün Türkiye'deki dağılımına katkılar sağlanması amaçlanmıştır. Çalışma süresince Türkiye'nin 6 farklı coğrafik bölgesinde bulunan su kaynakları arasından toplam 130 lokalitede çalışılmıştır. Çalışma sonucunda 39'u lotik, 28'i lentik su kaynağı olmak üzere toplam 67 lokalitede G. holbrooki türünün varlığı tespit edilmiştir.