Fish Reproduction In Water Bodies Of The Equatorial Latitudes (the Case Of The Genus Rutilus)
M. M. Shihshabekov, N. I. Rabazanov, E. V. Fedonenko, N. M. Abdullayeva, O. N. Marenkov
The analysis of the current state of roach populations in reservoirs of Zaporizhia, Ukraine and Terek systems, Dagestan was done. We showed the structure and age pattern of the spawning stocks of fish, size and weight indices, calculated the individual absolute fecundity for different age groups and gonadosomatic index of sex glands for all periods of the year. A histological analysis of the gonads of European and Caspian roach at different stages of gonads genesis was performed. We also set the asynchronous development of oocytes in summer. Individuals of local fish populations, caught from environmentally unfriendly waters, were significantly behind in growth and have low reproductive rates compared with fish that inhabit clear waters. These differences are the result of physiological and environmental changes in fish under the influence of factors of anthropogenic pollution. In the process of gonad maturation in female European and Caspian roach the ovocyte development occurs asynchronously, which is likely due to the influence of hydro-ecological conditions (temperature and water level regime) in summer. The development of ovocytes was normalized in autumn and spring period before the spawning. The appearance of the dwarf form of roach in reservoirs of aquatic Terek system could be explained by environmental degradation caused by the reconstruction works.