Atatürk Dam Lake is an important ecosystem located in south-eastern Anatolia in Turkey. In this study, concentration of Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined in kidney, liver, gill and muscle of Tor grypus which has great economic value in Atatürk Dam Lake. Heavy metal levels in fish samples were analyzed by inductively coupled plasma spectroscopy (ICP). The metal accumulation in the liver, kidney and gill of Tor grypus was found to be quite high in comparison to the muscle. All metal levels detected in tissues were the limits for fish proposed by FAO/ WHO, EU and Turkish Food Codes and safe within the limits for human consumption in the edible parts of fish species in the region.

Age at length, growth and reproduction of 220 Mastacembelus mastacembelus specimens from the Atatu¨rk Dam Lake were studied from July 2005 to July 2006. Total lengths and weights ranged from 7.0 to 85.0 cm and from 6 to 1100 g, respectively. Maximum age was 13 years. The regression model fitted to length and weight data was W = 0.0228 L 2.43 for males and W = 0.0029 L 2.95 for females. The von Bertalaffy growth equations for males and females were L t = 99.2 [1)e )0.11 (t)0.12) ] and L t = 69.2 [1)e )0.26 (t)0.35) ], respectively. Males dominated especially at an older age; the overall sex ratio was 1 : 0.63 (M:F). The breeding period was from May to July. Fecundity ranged from 2540 to 24 000 eggs per female.

In this study, the age, growth and reproduction characteristics of Aspius vorax, which were caught from Atatürk Dam Lake (Euphrates River) between September 2007 and August 2008 were determined. The age composition of the specimens ranged between II and IX age groups. The observed sex ratio was 1:1.75 (females/males). The fork length and weight of the individuals that were examined ranged from 184 to 863 mm and from 54 g to 4,317 g, respectively. The relationship of fork length (L F ) and scale radius (S) was estimated as: =0.9549) for males. Mean somatic condition of females and males were estimated as 1.069 and 1.062, respectively. The highest values of the somatic condition were determined in the November for females (K=1.23) and in the September and October (K=1.13) for males. Males matured during their third year of life in the studied samples, but due to lacking of young female specimens, the first maturity age for female was not determined. However, all those females examined at age 4 and over were seen to reach mature. erkeklerde ise 1.062 olarak hesaplanmıştır. En yüksek değer ise dişilerde kasım (K=1,23), erkeklerde ise eylül ve ekim (K=1,13) aylarında görülmüştür. İncelenen örneklerde erkeklerin 3. yıldan itibaren eşeysel olgunluğa ulaştıkları belirlenmiştir. Bununla birlikte daha genç yaşlara ait dişi birey elde edilmediği için dişilerde ilk eşeysel olgunluk yaşı tam olarak belirlenememiştir. Ancak incelenen 4 yaş ve üstündeki bütün dişi bireylerin eşeysel olgunluğa ulaştıkları görülmüştür.Anahtar Kelimeler: Aspius vorax, büyüme parametreleri, kondisyon faktörü, yumurta sayısı, gonadosomatik indeks.

Maturity, growth and reproductive characteristics of the mossul bleak Alburnus mossulensis, from Ataturk Dam Lake (Euphrates) were assessed. Maturity composition of the analysed samples varied between age groups I and VII. The ratio of females to males was 1.047:1. Fork length of the samples varied between 40-198 mm and weights were in the range of 0.45-68 g. The regression equations derived for the length-weight relationship was Log W = -5.5531+3.2958 Log FL (r2=0.9593) for females and Log W=-5.3695+3.2112 Log FL (r2=0.9487) for males. Mean condition factor was determined as 1.069 for females and 1.062 for males. Absolute fecundity was established to be between 288 and 3380. The age of sexual maturity was 3 years in females and 2 years in males.

In this study, sex composition, spawning period, fecundity and sexual maturity of the gibel carp, Carassius gibelio (Bloch, 1782), an invasive species in the Atatürk Dam Lake, on Euphrates River,Turkey were studied. C. gibelio specimens were analysed from Ataturk Dam Lake and the percentage of the males and females was 45.55% and 55.45% respectively out of the 110 specimens studied, ranging between age groups I -VI. The age at first maturity was three years for both females and males. The diameter of the egg was smallest in September, with a mean of 0.62 mm, while the mean egg diameter in June was greatest, at 1.54 mm. The absolute fecundity ranged from 1054 to 22548. Reproduction of gibel carp in Atatürk Dam Lake in Turkey was characterised by a young age at first maturity and high spawning capacity that would facilitate population expansion in aquatic environments.