Reproductive Regulation And Fry Breeding Technology Of Thamnaconus Septentrionalis Günther

Thamnaconus septentrionalis Günther are mainly distributed in the western Pacific Ocean,which belong to warm-temperate demersal fish in the open sea. In foreign coutry , Thamnaconus septentrionalis Günther are distributed in the coastal of Japan and Korean peninsula,but in China ,they are mainly distributed in the East Sea and Yellow Sea and Bohai Sea and the coastal of Taiwan, the yield is larger in the East Sea that of them. Since the 1990s, the natural resources of Thamnaconus septentrionalis Günther are declining because of overfishing and other reasons ,and the catches are extremely few ,which cannot form certain catching . Thamnaconus septentrionalis Günther belong to valuable marine fish , which have broad market prospects. Due to the fishery protection and proliferation , high market price and complete conditions of propagation,the artificial propagation of Thamnaconus septentrionalis Günther is feasible .In this paper, the reproductive regulation and fry breeding on Thamnaconus septentrionalis Günther are studied, which could provide the reference and scientific basis for the artificial propagation and large-scale production of Thamnaconus septentrionalis Günther .1. The traditional method of paraffin section and H.E staining is used to study the histology of the gonad in female Thamnaconus septentrionalis Günther . The characters of the ovary at different stages were described. The results indicated: the ovarian developments of the fish were divided into 6 stages, the development of oocytes from phase 1 to phase 5 was nonsynchronous ;The spawning is asynchronous and batch-wise .the testis comprise the spermatogenic testis and the seminal vesicle , the spermatogenic testis has a typical structure of lobulas. The production practice shows that the spawning period of the fish in the Bohai Sea is one month later than that in the East sea because of the water temperature and the spawning time is from mid May to mid June .2. The gonad was promoted mature by controlling the water temperature and light condition in the culture apart stage of 2a～4a adult fish. Zygote was obtained by artificial insemination with collected mature eggs and sperms. The embryonic development was observed by Olympus SZ-61 microscope, the total development time of every development stage was noted and calculated and the characteristic images were taken using a charge-coupled device(CCD). The fertilized eggs are globular, stickiness, thick egg membrane and the egg diameter is 0.59～0.63mm(n=37). Along with embryonic development, the all oil balls(there were 18～83 oil balls per egg at the early stage, n=37) consolidated to only one. Embryos were incubated in sea water (salinity 32～33) at 21.0±0.5℃. The time-table of major embryonic development stages was as follows: blastodisc forming stage at 0h50m post fertilization(pf); 4-cell stage at 1h55m pf; morula at 5h30m pf; low blastula stage at 7h20m pf; early gastrula stage at 10h pf; late gastrula at 15h30m pf; blastopore closing stage at 17h pf; 6-somite stage at 18h30m pf; tail bud stage at 25h30m pf; embryo movement at 40h pf; 50% hatching stage at 50h pf. The biological zero for embryonic development was calculated to be 11.736℃, and the effective accumulated temperature to be 463.2℃·h.3. The filefish, Thamnaconus septentrionalis Günther is a commercial marine fish species which distributes in the northwest Pacific, including the costal areas of China, Japan and Korea peninsula. It is a warm temperature, middle/low water course type fish species inhabiting in the depth of about 50 m to 120 m. As for over-fishing and environmental pollution in the past decades, the natural population of Thamnaconus septentrionalis Günther declined sharply. In order to maintain the natural resources and meet high consumption demand, the study on artificial breeding is necessary. The parent fish of Thamnaconus septentrionalis Günther were composed of acclimated wild adults which were caught in the Yellow sea of China in April, 2010. Photothermal regulation was adopted to mature the brooders and natural spawning occurred. The larvae were cultured in indoor concrete tanks with sand filtered natural seawater (salinity 32~33) with the environmental factors as follow: water-temperature ranged from 21～25℃, light strength was 1000～2000lx with consecutive aeration. The food regime for larvae culture: Chlorella (0～24 days past hatching, dph for short) â†'Crassostrea gigas larvae (3～10dph)â†'Rotifer(8～24dph)â†'Brine shrimp nauplius(19～36dph)â†'commerical feed (32dph～)â†'fresh shellfish/ cuttlefish meat(60dph～). The early history development of Thamnaconus septentrionalis Günther was observed by Olympus SZ-61 microscope. Every development stage was noted and calculated, the characteristic images were taken using charge-coupled device(CCD) and SONY H-50 camera. The early life history of Thamnaconus septentrionalis Günther is: the larvae rely on their yolk for nourishment before 3dph(0～2dph,yolk-sac larvae), after this the larval mouth opened at 3dph(3～18dph, pre-flexion larvae).The tail end of notochord upwarped at 19dph(19～24dph, flexion larvae), the tail fin developed perfectly at 25dph(25～39dph, post flexion larvae). All fin rays and scales were formed at 40dph, the fish turned into juvenile stage, which having the same appearance as adults. The morphological development and changes of pigment pattern were observed. The development of mouth, dorsal spine, girdles + pelvic fin and caudal peduncle were described with 4 plates. The growth characters, feeding habits, high mortality stage in larval rearing, the development and devolution of pelvic fin were discussed. The paper proposed some method of ascend the larval survival rate of Thamnaconus septentrionalis Günther in artificial reproduction.