Introducing the Karganrood River as one of the safe routes to release sturgeon

The aim of this study was to introduce the Karganrood River as one of the safe routes for releasing sturgeon fry. Karganrood River is located in the west of Gilan province in Talesh city. In the river, 3 sampling stations were considered. The range of changes in dissolved oxygen was 8.21 to 8.87 mg/l. The pH value ranged from 9 to 9.43. The amount of ammonia in station 3 was highest and in station 1 was the lowest amount. The amount of nitrite and nitrate was reported the highest in station 3. Oxygen and pH at releasing time were 8.46 mg/l and 9.24, respectively. Biomass of chironomidae, Gamarus and insect larvae in station 3 were significantly more than stations 1 and 2 (P<0.005). The amount of organic matter in stations 1 and 3 was significantly more than station 2 (P<0.005). In the 3 stations, sand percent was significantly more than clay and silt (P<0.005). Study on percent of sediment granulation in 3 stations showed that there is no significant differences in clay percent among stations 1, 2 and 3 (P>0.005) and silt was present only in station 1. One thousand juveniles of Stellate sturgeon (Acipenser stellatus) with an average weight of 1.56 ±0.58g and an average length of 8.58±1.23cm were released at the third station. 95 juveniles of Stellate sturgeon were tracked from releasing place up to near the estuary. After 7 hours from the releasing time, 4.1% of total released juveniles were caught by the net located in the estuary.