Study on growth and development of larva,juvenile and young fish of Mystus sp.

At the water temperature of 22～24 ℃ and pH around 7.0,the growth and development of larva,juvenile and young fish of Mystus sp.were observed.The results showed that development of this species could be divided into four phases,including pre-larva(from hatching to the 5th day),post-larva(the 6th day to the 10th day),juvenile(the 11th to the 20th day) and young fish(after the 20th day) respectively.The first hatching larvae were only 5.12 mm long with a yolk-sac of 1.63 mm3.The larvae began to eat on the 3rd day and yolk-sacs were fully assimilated on the 5th day after hatching.The exterior organs developed mainly in the stage of late-stage larva and the largest inital feeding rate of larvae was 84.0% which appeared on the 6th day and the point-of-no-return was on the 8th day after hatching.From then,the unfed larvae entered into the stage of PNR and most died on the 11th day.