Studies On Techniques Of Verasper Moseri Artificial Breeding

Verasper moseri is an ideal species for intensive culture, but its artificial breeding techniques are still not well-developed. Especially the egg-collecting and parent fish cultivation techniques are immature, and the artificial breeding techniques need be studied in further details.Under artificial hatchery conditions, parent fish of 3-4 years old were selected and reinforced cultivation were conducted to promote maturation under certain water and temperature condition. Fertilized eggs were obtained by artificial insemination. Embryo, larva and juvenile development were observed continuously. The results show: The fertilized eggs of Verasper moseri are global, which have transparent yolk and homogeneous but with no oil ball. The average diameter of eggs is 1.77±0.02mm. Juvenile pigments appear when olfactory plates begin to form. Under water temperature of 8.5℃, the embryos hatch after 187h. The newly hatched larvae with average total length of 4.69±0.15mm are transparent, floating on the water surface. During the 5th day after hatching, when water temperature rises from 9℃to 14.5℃, the body surface of larvae appear more melanophores, which makes the larvae look gray;pectoral fins begin to develop, which enable larvae to swim horizontally. During the 8th-9th day, digestive duct forms, and yolk-sac is absorbed on the 12th day. On the 25th day, the larvae's notochord bends upwards, the fin rays of odd fins differentiate, some pigment cells on the fin rays of dorsal fin and anal fin concentrate, and mastoid teeth on mandible appear. On the 30th day, left eye of larvae begin to move upwards. On the 38th day, some larvae begin to depigmentize and become sand-brown, and most larvae begin to land on the bottom of tank. On the 51st day, the left eye moves to the right and larva metamorphosis is accomplished.In addition, the feeding habits and growth performance of V. moseri larvae and juveniles during the first 50 days after hatching were studied. The results show that at water temperature of (14±0.5)℃, the larvae begin to feed about 8d after hatching. Based upon the observation of 183 individuals, the percentage of stomach with food is 84.2% and the plump coefficient of stomach is 1.86%-8.20% under the experimental conditions. The diet feeding amount is about 8.67%-27.17% of larvae and juvenile fish. Rhythm of feeding intensity is obviously different during the day and at night, and the highest feeding intensity is between 16:00 and 20:00. During larva and juvenile stages, usually fish don't eat anything at night. The relationship between the feeding amount and body weight can be expressed as y = 0.0418x + 0.1122, and the relationship between the total length and age can be expressed as L= 4.9522 e 0. 0264D. The relationship between body weight and age can be expressed as W = 0.7424 e 0. 1016D, and the relationship between total length and body weight can be expressed as W= 0.0019 L3 .7504. There are differences in growth between the individuals of larva and juvenile fish.During the development period of larva and juvenile stages, the morphological characters of abnormal individuals were observed. The results show that the abnormal morphological characters of V. moseri larvae and juveniles appear firstly on the 5th day after hatching and exhibit clearly on 7th-8th day after hatching. The morphological characters have three types: 1.Abnormal type A: Larvae don't have well-developed operculum and mandible bone so that mouth could not shut freely, abdomens swell, pectoral fins have not developed, so that larvae could only float on the water surface; 2.Abnormal type B: Larvae have abnormal operculum and mandible bone, so mouth could not shut fully, and pectoral fins do not develop well, so that larvae could only float on water surface and swim horizontally occasionally ; 3. Normal type C: Larvae have normal operculum and mandible bone, so mouth could shut freely, and pectoral fins become bigger, so larvae could swim horizontally by swing of caudal fins and quick rowing of pectoral fins. Most larvae of abnormal type A and B die on 15th-20th day after hatching. Some larvae of type B can feed a little and grow up, but they grow slowly, could not accomplish metamorphosis development, and die on the 30th～50th day after hatching. For normal larvae,their left eyes begin to move upwards on the 30th day after hatching, and the eyes move to right side completely on the 50th day. At this time, the larvae depigmentize and land on the bottom of tank. After depigmentizing, about 10 percents of abnormal larvae could not form adult melanophores and show albinism.