Studies On Biology In The Early Life Stages And Artificial Breeding Technique Of Kelp Bass (epinephelus Moara)

Kelp bass Epinephelus moara, a fast growing and commercially valuablemarine fish species, is considered as one of the most potential species for marine fishcage culture in the temperate seas along the coast of Northeast Asia. It has beeninvestigated intensively for aquaculture during the past several decades in the severalcountries. This article briefly summarizes the biological characteristics of Kelp bass,further research priorities in this domain are also suggested. The progress onbroodstock reproduction, larval rearing, and the nursery of juveniles of artificialbreeding, which has been mainly achieved recently years. This paper also providesnecessary referential information for the research on the mass seed productiontechnique of Kelp bass in China. The main contents are the following:1. Ultrastructure of egg, spermatozoon and fertilization process of Epinephelus.moara was observed by scanning electron microscope(SEM). The results showthat there is only one micropyle appeare in the animal pole, it consists of adepressed vestibule and a canal. A lot of small holes are found on the vestibuleand the outer chorionic surface.The cross-section of egg shell membranesthickness is3.4~3.5μm, with parallel layered structure, and closelyarranged.Spermatozoa of E. moara has the typical osteichthyes characteristics,consists of an acrosome-less head, a short midpiece containing severalmitochondria and a long tail. The spherical head of diameter is1.9~2.0μm,mainly consists of the nearly circular cel1nucleus, and the tail is about16~17μm.The process of fertilization which happened90seconds could divide into fourphases: egg membrane attracting sperm; sperm anchoring on egg membrane;sperm karyon penetrating into egg membrane and holes on the surface closing.The polyspermy phenomenon has not been found in the whole process.2. The morphological features and the developmental time were described in greatdetail from fertilization to young fish. The results shown that the time for theembryonic development is38h17min in the water with temperature (22±0.2)℃,salinity30, DO7.8mg\L, pH8.25. Based on the obtained data, six periods including28stages of Epinephelus moara embryo are established, which arecleavage period, blastula period, gastrula period, neurula period, organogenesisperiod and hatching period. After5days rearing in the sea water of temperature(23±1)℃, salinity30±3, DO≥5mg／L, pH8.0±0.5, the yolk-sac of larvae woulddisappear and changed into late larva; after27days, the fast growing larvaeamong the others developed into juveniles; after65days, the fast growingjuveniles among the others completed metamorphosis and changed into youngfish. The post embryonic development of Epinephelus moara was divided intolarval stage, juvenile stage as well as young fish stage, based on the features ofthe yolk-sac, finfold, pelvic fin spine, second dorsal fin spine, scale and bodycolor. Accordingly, the larval stage was further classified into early larva and latelarva, with or without yolk-sac, respectively.3. In this study, the impact of embryonic development and the survival activityindex (SAI) of the larvae of Kelp bass was investigated under salinities of5,10,15,20,25,30,35,40and45, and pH values of5.5,6.0,6.5,7.0,7.5,8.0,8.5,9.0,9.5, with water temperature at22±0.2℃. The results indicated that the minimumand maximum salinities for the embryonic development of Kelp bass were10and45, the minimum and maximum pH were6.0and9.5, repecitively. The suitableranges were15~40for salinity, and6.5~9.0for pH, and the optimal ranges were30~35for salinity, and7.5~8.0for pH, respectively, based on the developmenttime, hatching rate (HR,%) and deformity rate (DR,%). Salinity from20to35,and pH from6.0to9.0were suitable for larval survival, and the optimums werefrom25to30for salinity, and from7.5to8.0for pH, respectively.4. Survival, growth and feeding rate of Epinephelus awoara, E. akaara, E. brunneus,E. moara and E. septemfasciatus were studied in two different temperaturechange modes (DS: temperature Decreased Sharply; DG: temperature DecreasedGradually). The results showed that:1) Under sharply changing temperatureconditions, the young fish of groupers are survived (the survival rate were100%)and growth (energy) at temperature17~23℃, which DS-23℃,20℃, DS groupfeeding is normal. Larval survival rate in DS-14℃group began to decrease,vigor is poorer, to stop feeding and death, after48h survival rate was86.65%,96.65%,100%,95%and78.35%. DS-11℃group survival rate was0%, grouperjuvenile fish plunged by maximum temperature difference should not exceed10℃.2) Under gradually changing temperature conditions, the survival rate of the young fish of groupers were100%, the activity and feeding is normal. Under17℃temperature to stop feeding, lethal temperature respectively10,7,9,8and9℃, temperature tolerance limit9,6,8,7and8℃, respectively. Low temperatureresistant capability from weak to strong were E.awoara <E.septemfasciatus <E.brunneus <E.moara <E.akaara.5. Seven-band grouper (Epinephelus septemfasciatus) and Kelp bass (E.moara), fastgrowing and commercially valuable marine fish species, were cultured inrecirculating aquaculture system (RAS). In this study, the model summary andparameter estimates in E.septemfasciatus and E.moara were analyzed by curveestimation. Growth characteristics were studied, based on weight, total length andbody length. The results are as follows: after122days’ culture, the averageweight of E.septemfasciatus increased from114.836±25.343g to213.861±38.604g, and E.moara from79.620±13.007g to238.086±46.307g. For growth at acubic rate, the total length (TL) of E.septemfasciatus and E.moara at culture time(t) could be calculated as: TL=0.006t3+1.622t+13.954andTL=0.013t2+2.008t+11.540, respectively. The relationships between weight (W)and body length (BL) were represented as: for E. septemfasciatus,W=0.436BL2.055, and for E. moara, W=0.018BL3.083. Relative growth rates (RGR)were0.707%for E.septemfasciatus and1.631%for E.moara. In addition, thedifferent from E.septemfasciatus to E.moara did not differ significantly (P>0.05)about the relative fatness, maintained at2.2~3.4.