Comparison of various bony structures for the age determination of Chondrostoma regium (Heckel, 1843) in Tishreen lake (Euphrates River)

The goal of this study is to compare three bony structures in order to choose the best method for the age determination of Chondrostoma regium inhabiting the Tishreen Reservior (Euphrates River). So, 214 individuals were collected between 15/7/2011 and 15/5/2012 using appropriate gill nets. Scales, vertebrae and operculum were independently used by two readers to estimate the age. Mean ages were estimated for each bony structure-reader combination and the precision of age estimated from multiple readings was evaluated. Furthermore, the error of ageing was calculated. The results showed that the fish ages were varied between (2-6), (3-6) and (2-5) years- judged by scales, vertebrae and operculum respectively. Results also showed that vertebrae were the most reliable bony structure for estimating the ages of Chondrostoma regium as they had the highest agreement and the lowest ageing error.

Determination of Better Methods to Evaluate the age of Acanthobrama Marmid (Heckel, 1843) in Tishreen Fish Reservoir(Ephrate river)

The purpose of this study was to determine the best method for age estimation by comparing scales, vertebrae and operculum of Acanthobrama marmid inhabiting the Tishreen Reservoir (Euphrates River). An overall of 194 specimens of Acanthobrama marmid were collected between 15/7/2011 and 15/5/2012 using appropriate gill nets. Each bony structure was examined independently by two readers without referring to any information except for the date of capture. The precision of the readers was estimated and ageing error was determined by analysis of variation. Our results showed that vertebrae were determined to be the best reliable bony structure for ageing Acanthobrama marmid because of them having the highest precision and the lowest ageing error.