Age, sex ratio, spawning season, reproduction, and fecundity of Channa gachua (Actinopterygii, Channidae) from Makran basin, Southeastern Iran

Channa gachua is native to the majority of streams in southeastern Iran, but reproductive parameters of the fish are barely known. Reproductive conditions are key parameters of fish populations and their assessment is very important for several reasons. To investigate reproductive biology of the native dwarf snakehead, sampling was done at monthly intervals throughout the year and 404 individuals were caught from Kajou River in Makran basin. Age, sex ratio, fecundity, oocytes diameter, gonado-somatic, modified gonado-somatic and Dobriyal indices were estimated. Regression analyses were used to find relations between fecundity and fish size (length and weight), gonad weight, and age. Sex ratio differed from unity and biased to females. The mature females and males were longer than 75 and 61 mm in total length (+2 and +1 in age, respectively). The average egg diameter was 0.50 mm, maximum 0.73 mm in April. The spawning took place from beginning of April to late June. Average GSI value at the beginning of the reproduction period was 2.89% and ranged between 0.3% and 4.4% in ripe, mature females. The average of absolute and relative fecundity was calculated 3471 and 248, respectively. The absolute fecundity was significantly related to body length and gonad weight. Based on the pattern of gonad indices, it was concluded that this fish has a prolonged active reproductive period, which is a type of adaptation by short-lived small fishes to environmental conditions.