Survey of environmental parameters on reproductive migration of Caspian lamprey (Caspiomyzon wagneri Kessler, 1870) in the Shiroud River, Mazandaran Province

In this study, some environmental parameters including temperature, pH, electrical conductivity, mean water velocity, water transparency and weather as environmental influencing factors on migration of Caspiomyzon wagneri into Shirud River was investigated in spring and fall 2011. The estimated number of migratory fishes in the river through observation of the fishway. Results showed that in spring, the migration period started in 9 February untill 1 May, and in fall, 26 September untill 23 October. Migration peak occurred on 28 February and 16 October on spring and fall seasons, respectively. The maximum rate of migration occurred at night in semi-cloudy weather but the minimum amount of it, was in the morning. pH range changed 8.2-8.5 and decrease to 7.5 when it was snowy. In spring, the temperature range changed from 7.8 to 21°C and migrate peak was conducted at 10.8°C but in fall, this range was between 19.8-24°C and the peak migration was observed at 21.3°C. The migration time and cloudy weather were known as significantly effective parameters in the reproductive migration of Caspian Lamprey.