Life history traits of Capoeta trutta (Heckel, 1843) from Seymareh River, western Iran (Teleostei: Cyprinidae)

In the present study, some biological aspects of Capoeta trutta (Heckel, 1843) have been examined for the aim of future stock assessment, exploitation and conservational managements. A total of 103 fish specimens were collected seasonally from Seymareh River, Tigris basin, Iran, in four seasons during 2011- 2012. Observed maximum age was 4+ in both sexes and sex ratio obtained as 1M:1.9F. Analyses showed a highly significant length-weight relationship of 0.98 for C. trutta with a b parameter of 3.09. Generally, females were larger than males with the maximum length of 28.0cm and minimum of 9.8cm. Mean Relative Length of Gut (RLG), weight (W) and total length (TL) were calculated according to size classes and ages. The most frequent size belonged to 20-24cm length group with the percentages of 52.9 and 48.6 for females and males, respectively. Based on the results of main reproductive indices; Gonado-Somatic Index (GSI), Modified Gonado-Somatic Index (MGSI) and Dobriyal Index (DI), C. trutta spawns once a year in spring. Condition factor (K) value also revealed the peak in the spring which is in accordance with the highest gonadal maturity of this species. The mean value for RLG was obtained as 4.6 and Zihler’s index (ZI) was calculated as 2.11. Based on RLG and Zihler indices, C. trutta might be considered an herbivore species.