REPRODUCTIVE BIOLOGY OF SILURUS MERIDIONALIS: TIME,ENVIRONMENTAL CONDITIONS AND BEHAVIOUR OF SPAWNING

Three or four years in famale and 2 or 3 years old in male Silurus meridionalls reached their first sexual maturity. At such ages the average body length, weight, condition factor and maturatlon coefficient of adults are higher than those of the un-mature juvenile of same age for both sexes.The breeding season in the Jialing River lasts from middle March to middle May,when the water temperature ranges from 15℃ to 24℃. From June to August the gonad of stage Ⅳ in the spawned female degenerates into stage Ⅱ.From September to November the gonad develops into stage Ⅲ,and gradually into stage Ⅳ.The gonad remains at stage Ⅳ during winter(from December to February). Only one peak value occurs in the annual cycle of the maturotion coefficient in both sexes, suggesting that this fish spawns only once a year. The spawning sites are located in pebble shoals with a water depth of 0.4-1.5m and a current volocity of about 0.7m/s. During courtship the parental fish display vigorous chasing and snapping behaviours.