Study on the change of some ion, hormone and biochemical factors in released fingerling of kutum fish (Rutilus frisii kutum Kamensky, 1901) at the estuarine of Tajan river (Sari)

Releasing of Kutum fish (Rutilus frisii kutum Kamenskii 1901) fingerling almost done in the estuarine، where are cumulative site of various pollutant such as chemicals، pesticides and heavy metals. Therefore، investigation of the modality of osmo&ion regulation of kutum fingerlings in the Tajan river (Sari) by means of some osmoregulatory factors، was the aim of this study. Fifty fingerling fishes (0. 5 gram) were released in eight cages that located in transverse manner in the estuarine of mentioned river. Cages were divided to two groups: The first group was stocked at initial time and sampled after 7 days. In order to assessment of osmoregulatory capability of fingerlings in the shorter times، the second group was stocked at the fourth day of the first group stocking and were sampled after 36، 48 and 72 hours. Based on results، significant difference was observed about obtained factors (except of chloride and T4) between experimental cages and control groups (P<0. 05). An amount of measured ions in fingerling fishes of experimental cages was greater than control group and ascending trend was observed in the case of sodium، chloride and potassium from 72 hours to seventh day. The rate of T3 and water body content (%) in the fish of cage group were lower than control group and significant difference was observed in particular times (P<0. 05). The quantity of T4، glucose، total protein and mortality percent in the fingerling fishes of cage group were dominantly bigger than control group. The same trends was observed in the case of cortisol between two groups until 72 hours، but an ascending and descending trend was detected at the seventh day in control and cage groups respectively. Resultant of the obtained results osmoregulatory disorder and failure in salinity adaptation in fingerling of the kutum fish was observed.