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Sex steroid hormones play important roles in many physiological processes, particularly in the reproduction of teleostei. Therefore, study of steroid hormones in fish is one of the important indicators of reproductive biology. In the present research, serum steroid hormones such as testosterone (T), 17β-estradiol (E2) and progesterone (P) in Esox lucius brood stocks, during one year, from autumn 2010 to summer 2011, in five periods (autumn, first half of winter, second half of winter, spring and summer) with three longitudinal classes: 300-360, 360-420 and 420-480 millimeters were studied. The results showed significant difference between levels of steroid hormones in three longitudinal classes and showed an increasing trend by increased length (P<0.05). In addition, there was significant different between levels of gonadal steroid hormones and different seasons (P<0.05). The highest level of 17-β estradiol was observed in autumn season. In the case of testosterone and progesterone hormones, higher levels were recorded in first and second half of winter, respectively.
 

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In order to investigate the differences in the shape of the big-head and two morphotypes of Phytophagous fish by geometric morphometric technique, 30 samples of each group, with a mean standard length of 25 ± 3 cm, were prepared. After fish were anesthetized by 1% Clove powder extract and stabilized in formalin buffer 4%, 6-megapixel digital images of the left profile of the specimens were prepared. A total of 17 morphological landmarks were digitized by tpsDig2 software and the tps files were prepared. All non-shaped data were removed from landmark coordinates by generalized procrustes analysis. After the approval of regression between shape space and tangent space, data were analyzed using Principal Component (PCA), Canonical Variation (CVA) and Cluster Analyzes (CA) methods in PAST and TPS series. According to the results, the head length and height, the size of dorsal fin, the length of pre ventral distance, the height of caudal peduncle and the degree of posterior position of the pectoral fin in bighead carp, are some of the distinctive morphological features among species, mainly related to their ecological niche (specially feeding strategies). In the case of silver carp variants, the posterior position of pectoral fin base in silver carp-R that is close to bighead carp, may be due to hybridization between bighead carp and silver carps.