First maturation and mass seedling propagation of cultured Eleutheronema tetradactylum in Guangdong Province

We studied the first maturation and spawning of 2-year-old cultured Eleutheronema tetradactylum and seedling mass production from June to September, 2015. The result shows that more than 2 000 broodstocks were maintainced during the experiment with maturation rate of over 93%. There was significant difference in body weight between male and female broodstocks. The gonadosomatic index (GSI) of female was 1.03%~ 6.05%, while that of male was 0.26%~1.76%. The breeding pattern of female was batch maturating and spawning, with laying eggs once a year; and the spawning period of female with the first maturation lasted from June 13, 2015 to the end of September. About 75.0×10⁶ eggs were produced with fertility rate of 72%~95%. The embryonic development finished in 13 h 52 min at 29~31 ℃, salinity of 27~28.8 and pH of 8.1~8.3, with hatching rate of 58%~95%. Newly hatched larvals were reared in indoor tanks for 5~7 d with Chlorella sp.and rotifer as foods, and were transferred to outdoor ponds afterwards, with feeding cladocera and copepods. Nauplius of Artemia sp.was fed since 25^th day after hatching, and then powdery compound feed and granule feed had been fed since 30^th day after hatching. About 15.0×10⁶ fries of second filial generation were harvested from July 23 to September 30, 2015, with an average survival rate of 25%. The keys for complicated artificial propagation of this species are management of qualified broodstock, water quality control and in time feed change.