Study on biological characteristics of Snow trout Schizothorax zarudnyi (Nikolskii, 1897) in Chah nimeh reservoirs, Sistan and Baluchestan Province

Snow trout (S. zarudnyi) is a commercial, ecological and biological valuable species which is native to the southeastern Iran (Sistan). In this study, 41 samples of Snow trout were caught by gill net from Chah nimeh reservoirs, Sistan and Baluchestan Province, and their biological characteristic were investigated. The results showed that the average weight and length of fish were 121.70±57.07g and 22.35± 3.49cm, respectively. The sexual ratio in Snow trout was 1:1.16 (male: female), and the gonadosomatic Index (GSI) of female was 1.08±0.74%. Moreover, the maximum and minimum percentage of GSI was reported in March (1.75%) and May (0.84%), respectively. The changes in the percentage of GSI indicated that the sexual maturity and breeding season of this fish happened in March. The average relative and absolute fecundity recorded was 33140 ± 1905.65 egg/kg and 26964±1001/97 eggs, respectively. The condition factor (CF) was 1.01±0.12 %, and the maximum and minimum amount of CF was reported in March and May, 1.30% and 0.76%, respectively. The relative gut length (RLG), as the ratio of intestine length to body length was 1.73±0.30. Consequently, considering the amount of RLG which was more than one, Snow trout categorized as omnivorous with herbivorous tendency. The average of feeding intensity (IF) was 180.64±108.99%, and the maximum and minimum of IF was found in May and February, 480.54 and 43.02%, respectively. Finally, the relationship between the length and weight for the species was recorded as W=0.0058L3.177 with r=0.98. The b-value as coefficient of WLR indicates that the growth of Snow trout is isometric.