Biological properties of the wels catfish (Silurus glanis L., 1758) from Siddikli Kucukbogaz dam lake

This study was carried out with the aim of determining the age, growth, feeding and reproduction characteristics of the wels catfish (Silurus glanis L., 1758) inhabiting Sıddıklı Küçükboğaz Dam Lake. A total of 203 wels catfish was provided from September 2015 to August 2016. Vertebra, lapillus, lapillus section, asteriscus and pectoral fin ray section were evaluated for age determination. Lapillus sections were found as the most reliable bony structure. The age distribution of the population was determined as 1-11 years. The total length of the samples ranged from 20.1 to 100.0 cm and weights from 40.40 to 7465.10 g. The growth parameters were calculated from the obtained age data. Asymptotic length and weight values for this population were determined as 174.58 cm and 35211.11 g, respectively. The values of a and b in the length-weight relationship of this population were calculated as 0.0034 and 3.129, respectively. The food composition of wels catfish was composed of 18 prey types belonging to 6 groups including fish, mammal, amphibian, crustacean, mollusk and benthic invertebrates. The seasonal variations were observed in the food composition. Ontogenetic feeding changes were observed, and negative and positive selectivity was determined in different length groups. In the sampling, the sex ratio was calculated as 0.88: 1.00 (Female: Male). According to Gonadosomatic index values, the reproductive period was determined to be between April and June. The average number of eggs was 46342.5 eggs/individual and mean egg diameter was 1.758 mm.