A study on some biological indices of migratory Caspian lamprey, Caspiomyzon wagneri, in the Shirood River in the fall and spring

This study was investigated reproductive differences in fall and spring migrants of Caspian lamprey (Caspiomyzon wagneri) in the Shirud River (Southern Caspian Sea)in 2008. 89 and 15 specimens were sampled in in spring and fall, respectively. Generally, fall migratory fish had a significantly lower condition factor (CF) compared to the spring migrants. There was significant relationship between fecundity-length and fecundity-weight in both spring and fall seasons. No significant differences was found in fecundity, oocyte diameter as well as hepatosomatic index (HSI) between fall and spring migrants. However, fall migratory females had a significantly higher HSI compared to the spring migratory females. Nodifferences were also found in gonadosomatic index (GSI) between fall and spring migratory males, and fall and spring migratory females. Sex ratio of spring and fall migrants was 1:1.