The life history of the non-native cyprinid fish Carassius gibelio (Bloch, 1782) from Demirkopru Reservoir in the Aegean Region in Turkey

Age, growth, reproduction, mortality, and length-weight relationships of 733 specimens of Carassius gibelio caught monthly using fishing nets of different mesh sizes (9 to 90 mm) in June 2015 - November 2016 from Demirkopru Reservoir, Aegean Region, were studied. Of the 689 fish specimens whose sex was determined, 475 were female and 214 were male. The total length and weight were determined to range between 10.7-39.6 cm and 12- 928 g, respectively. The length-weight relationships of females, males, and the entire population were described by the equations W=0.010xL(3.10), W=0.010xL(3.18), and W=0.010xL(3.12), respectively. The condition factor (CF) of the population did not vary by month and was generally in a similar value range. Gonadosomatic index (GSI) values reached the highest value in female individuals in March, while male individuals in February. The spawning period was determined to be from April to August when GSI values decreased, and the spent maturity stage female individuals were seen. According to the age identification using vertebrae, the population was in the age range of I - XIII. With 17%, the III age group had the highest ratio in all individuals. Growth parameters of the population were: L-infinity = 44.49 cm, K = 0.20 year(-1) and t(0) = -1.92 years for females; L-infinity = 38.32 cm, K = 0.25 year(-1) and t(0) = -2.14 years for males and L-infinity = 44.84 cm, K = 0.20 year(-1) and t(0) = -1.83 years for all population. The growth performance index (Phi') was calculated as 2.60, 2.56, and 2.60, for females, males, and all individuals, respectively. The natural mortality (M) rate was calculated to be 0.17 year(-1) for females and males. Total mortality (Z), fishing mortality, and (F) exploitation (E) rates were calculated to be 0.34, 0.17 year(-1), and 50% for females; 0.31, 0.14 year- 1, and 45% for males, respectively. As a result, the invasive Carassius gibelio was found to be best adapted to the environment in Demirkopru Reservoir, where it was first recorded in the 2011 fishing reports.