Evaluation of sperm characteristics and plasma testosterone in the goldfish (Carassius auratus) during four consecutive seasons

The overall objective of the study was to investigate changes in quantitative parameters of goldfish (Carassius auratus) semen, testosterone (T), and gonadosomatic index (GSI) during the four seasons of the year (spring, summer, autumn, and winter). Simple environmental and hormonal treatments were used to induce out-of-season spawning in goldfish. The semen was taken from goldfish in different periods during the four seasons, and the characteristics of sperm and pH were analyzed. Plasma levels of T, GSI, and histological studies of the testes, as well as a range of indices of ovarian development, were measured. No significant differences were observed between volumes of semen which can be extracted per fish, in the four seasons (P?>?0.05). Significant differences were found between sperm motility at different seasons (P??1) and winter (65.09?±?80.40 spz ml^?1) than values that were obtained from spring (48.00?±?7.08 spz ml^?1) and autumn (40.42?±?16.54?×?10⁹ spz ml^?1) (P?P?T and GSI during spermiation in spring (T, 21.08 ng/ml, and GSI?=?5.21 %) and in summer (T, 23.32 ng/ml, and GSI?=?6.10 %), when most gonadal development took place, were statistically significantly higher than the levels observed during autumn (T, 15.08 ng/ml, and GSI?=?3.21 %) and winter (T, 22.18 ng/ml, and GSI?=?2.78 %) (P?T and GSI, for goldfish. These findings may be used to: (1) optimize semen collection for hatchery production and (2) characterize the potential impact of seasons on sperm quality and plasma androgen levels.