Department of Fisheries, Faculty of Natural Resources and Environment, Ferdowsi University of Mashhad, Mashhad-Iran
Department of Fisheries, Faculty of Natural Resources, Gonbad Kavous University, Golestan- Iran
Department of Fisheries, Faculty of Natural Resources, University of Tehran, Karaj-Iran
BACKGROUND: Snow trout (Schizothorax pelzami) is an economically important species endemic in the north east of Iran. OBJECTIVES: The purpose of the present study was to investigate the reproduction cycle, time and temperature range of spawning. METHODS: The biometry of 243 fishes was measured and the ovarian development stages and plasma sex steroid hormones (testosterone, 17b- estradiol, progesterone and 17a-OH-progesterone) were measured during 12-months sampling. RESULTS: The (p<0.05) maximum significant gonadosomatic index (10.3 %) and ova diameter (1605.6 mm) were observed during April. The results showed that the concentration of sex hormones testosterone and 17b- estradiol began to increase significantly (p<0.05) during cortical alveoli stage (in September) and reached the maximum level (6.99 and 143.4 ng/mL, respectively) in February with the mean water temperature 13 oC at the end of vitelogenesis stage. The progesterone concentration began to increase at the end of vitellogenesis stage and reached (p<0.05) maximum significant level (3.49 ng/mL) in March. The concentration of 17a-OH-progesterone increased significantly (p<0.05) with a lag phase compared to progesterone in February. CONCLUSIONS: The results of present study showed that snow trout had a single-spawning strategy and sex steroid hormones testosterone and 17b- estradiol involved in the vitellogenesis stage and progesterone and 17a-OH-progesterone involved in the final ova maturation. The best spawning time was within March to April with temperature range 15.7-17.3 oC.