青龙斑仔、稚、幼鱼形态发育及饵料转变的观察

Studies on morphological development and feed changeover of the larvae, juveniles and young fish of Epinephelus coioides♀×E. lanceolatus♂

从青龙斑受精卵孵化开始到仔、稚、幼鱼形成的1个月内，进行形态发育与饵料转变观察研究。青龙斑受精卵在水温30～33℃、盐度30．0、pH值8．1、DO≥5．0mg/L的条件下经18～20h孵化出仔鱼，初孵仔鱼经约65—67h开口摄食。刚开口的仔鱼游泳能力弱．口裂小。以小球藻、轮虫等小型浮游生物为食。孵化后第7—8d开始长出第2背鳍棘和腹鳍棘，鳍棘长度与全长比在第14～18d达到最大值，接近0．5；第20d时，其他鳍条已长出，第2背鳍棘和腹鳍棘与全长比值降低；第29d之后，大部分鱼的背部或全身覆盖鳞片，个体差异显著。试验中，仔鱼前13d主要摄食轮虫及其他原生动物，第10d开始摄食部分挠足类幼体，第14d起主要饵料转变为挠足类和枝角类。

Morphological development and feed changeover of the larvae, juveniles and young fish of Epinephelus coioides ♀ × E.lanceolatus ♂ were observed and studied within a month since hatching. The fertilized eggs were hatched in water with temperature 30- 33℃, salinity 30.0, pH8.1 and DO≥5.0 mg/L, and the larvae were hatched after 18-20 hours and started to eat protozoa after 65-67 hours when they were hatched. In the beginning, the larvae with weak swimming ability and micro-mouth only feeding small plankton such as ball algae and rotifers. The second dorsal and ventral spines appearing when the larvae were 7-8 days old, and the ratio of these spines to total-length reached the maximum （close to 0.5） when the fish were 14-18 days old. At the 20th day, the ratio decreased obviously with elongation of other spines. After 29 days of hatching, most fish＇s back or whole body were covered with scale,and the individual differences of fish larvae was significant. In this study, the larvae main were fed with rotifers and other protozoa in the first 13 days after the larvae hatched, yet a small part of copepods larvae began feeding at the 10th day, their main feed changed into the eopepods and cladoeerans after 13 days.