Studies On Fry Breeding Technology Of Epinephelus Septemfasciatus

Epinephelus septemfasciatus, belongs to Perciformes, Serranidae, Epinephelus.Distributed in northwest Pacific Ocean including Chinese, South Korea and Japancoast. E.septemfasciatus is the only varieties of Epinephelus distributed in the yellowsea. It becomes one of the ideal cage-cultured variety in Northeast Asia temperateseas and has the features of high economic and ornamental values, fast growth speedand strong cold tolerance. In china, Japan and Korea, it becomes a hot issue in marinefish breeding research. It will change the status that lacking of variety suitable forcage culture in north of East China Sea as well as Huanghai and Bohai seas ifE.septemfasciatus is successfully bred. Meanwhile it will greatly widen the productionspace of groupers in our country. This paper is based on the E.septemfasciatus broodfishes. Technology of artificial breeding was studied. Now the results are reported asfollows:In a condition that artificial control light and light illumination time, the gonads ofE.septemfasciatus brood fishes developed to IV period after nutritional enhancementbreeding. The average coefficient of maturity of ovary was14%. Oxytocic drugs wereinjected into back muscles of the brood fishes whose gonads had matured. The resultsof artificial propagation and insemination indicate that the total amount of fertilizedeggs is2201387. The fertilization rate of eggs is71.3%.The diameter of fertilized eggis0.854±0.021mm.The time for the embryonic development is35h35min in the condition that watertemperature (21±0.5)℃, salinity30~31, pH7.9~8.2, DO6mg/L~8mg/L, lightintensity500~800lx. The morphological characteristics of every early developmentalstage and fry rearing were described in detail. The embryonic development ofE.septemfasciatus can be divided into five stages, namely cleavage stage, blastulastage, gastrula stage, neurula stage and organogenesis stage. The post embryonicdevelopment of E.septemfasciatus was divided into larval stage, juvenile stage as well as young fish stage, based on the features of the yolk-sac,pelvic fin spine,seconddorsal fin spine,scale and body color. Six different gradient sets of temperature weredistributed into the experiment groups to study the relationship between embryonicdevelopment and incubation temperature of E.septemfasciatus. The results showedthat19℃~23℃was the optimum temperature. Among all the temperature groups,group of21℃had the largest incubation rate which was61.9%.This was followed bythe group of19℃with hatching rate19.8%. However, concerning lowestmalformation rate, group of21℃and23℃ranked the top two, and figures were5.3%and6.5%.In the condition that water temperature22~24℃, pH7.9~8.2, salinity28~29, lightintensity500~800lx, DO6mg/L~8mg/L, the pre-larvae stage develops from hatchingto2dph. Feeding and changing water were not to be needed in this stage. Theembryon developed3days to the post-larvae stage. The fertilized eggs and larvae ofOyster were first feeds of larva fishes. S-rotifers were fed in6dph. Larva fishes beganingesting L-rotifers in10dph. Artemia nauplii were fed in17dph. The second spine ofdorsal fin and the first spine of ventral fin extended in9dph.The extension andshrinkage of long fin spines were the most obvious changes during early developmentof E.septemfasciatus. The ratio of the second spine of dorsal fin to total lengthattained its maximum (about0.81) when the larvae were28~30dph. The juvenilestage developed from31to57dph. The long fin spines began shrinking. Eubranchipusvernalis was fed in40dph. Granular compound feed was fed in55dph. The foodconsumption could be increased or decreased based the book on the food intake inseed production. Mortality of juvenile fish increased because of eating their own kind.Four different sets of aeration rate were distributed into the experiment groups tostudy the relationship between aeration rate and the survival rate of juvenile fish. Theresults show that increasing aeration rate timely during the cultivating of the larvalwith the juvenile’s growth is one of effective measures to improve the survival rate ofoffspring seed. The fish developed into the early young fish period in58dph. Themorphological character and life habit of young were similar to adult fish except thenot fully gonad. This study main starts from the aritificial rearing and breeding of parent fish. Thetechnology of artificial breeding of E.septemfasciatus was studied, and a set offeasible brood stock culture, artificial oxytocin induction, insemination, artificialincubation, artificial breeding techniques were mastered. The study accumulatedbiological data and fry rearing experience of E.septemfasciatus. It provided thescientific basis for extensive factory seed production of E.septemfasciatus.