Reproductive biology of the endemic spined loach Cobitis faridpaki in a tributary of the Gorganroud River, Golestan province, northern Iran

Cobitis faridpaki is a small endemic loach from the southern Caspian basin. Reproductive parameters are key components for enlightening the life history of an endemic species. The reproduction parameters of C. faridpaki including sex ratio, spawning season, fecundity, and oocyte diameters were studied in a tributary of Gorganroud River – northern Iran, the area where no information on the Cobitis spawning is available, from February to July 2018. A total of 403 specimens including 47.8% males and 52.2% females were collected using electrofishing. Even though the sex ratio was not significantly different from parity, a perceptible dominance of females in the pre-spawning and spawning periods could be observed in the population. Based on the monthly variation in GSI, the spawning period is from late March to early May. The absolute fecundity of females ranged from 57 to 1287, with a mean of 404 (±250) oocytes per ovary, and relative fecundity was estimated to be 47–386, with a mean of 136 (±73) oocytes per gram of total weight. Absolute fecundity established statistically significant linear relationships with total length and weight. Oocyte diameters varied from 0.26 to 1.30 mm, being of multi-modal distribution throughout the spawning period, which suggests that the species is a multispawner. The oocyte size correlated positively with the length, weight, and age of mature females. This study provides fundamental information to aid in future conservation programs that intend to reduce the ongoing depletion of habitats and populations of endemic species.