Reproductive biology of Cobitis keyvani (Cobitidae) from the Talar River in the southern Caspian Sea basin

 Some aspects of the reproductive biology of Cobitis keyvani (Mousavi-Sabet, Yerli, Vatandoust, Ozeren and Moradkhani, 2012), an endemic Loach fish species from the Talar River in the southern Caspian Sea basin, in north of Iran was studied by regular monthly collections throughout a year. Fecundity, condition factor, gonado-somatic, modified gonado-somatic and Dobriyal indices were estimated. Regression analyses tested the dependence of fecundity on fish length, weight, gonad weight and age. Significant differences were observed between the total number of females and males, females being more abundant. The mature females and males were longer than 49 and 45 mm in total length, and +2 and +1 in age, respectively. The average egg’s diameter was 0.56 mm. The spawning of Cobitis keyvani from Talar River took place from May to late July, when the water temperature is between 18.7 to 24.0°C. At the beginning of the reproduction period, the average GSI values were 10.09%, ranging from 6 to 25% in ripe mature females. The absolute and relative fecundity were 2211 and 586 respectively. The absolute fecundity was significantly related to body weight and gonads weight. Based on the gonado-somatic and Dobriyal indices, it was concluded that the fish has a prolonged active reproductive period. Their long reproductive activity and high range of fecundity are types of adaptation by short-lived small fishes to environmental conditions.