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Eel breeding
(1) Artificial seedlings are best reared and fed for artificial seedlings with an optimal salinity of 32 to 35, a temperature of 19 to 24°C, a dissolved oxygen of 0.0005%, and a stocking density of 50 to 250 tails/liter. Slightly larger aquaculture waters can increase survival rate at a small density, but the amount of feeding is large. Cement tanks and non-reflective black polyethylene clusters are generally used to prevent light reflection and direct sunlight. The rearing tank is pre-prepared a few days before the hatching of the fish, and the stored water fills each of the rearing tanks. Seawater needs to be sterilized and filtered. The seawater must maintain a salinity of 32 to 35 和 and a water temperature of 20 22 22 C before putting it into the fry. The rearing tank must be inoculated with green algae or other phytoplankton species prior to putting in the fishery to provide food for the rotifers. The inoculated phytoplankton is better in the species of green algae. After 60 hours, the eggs are fully hatched and the hatched fish are transferred to the culture pool with a siphon tube. Before the siphoning, the circulating water stops flowing. At this time, the fry appears on the upper layer of the water, and the egg membrane and the unhatched egg sink. Care should be taken Operate so that the egg membranes and unhatched eggs do not transfer with the larvae. The newly hatched fry was about 2.2-3.5 mm in length. The oil globules were present in the posterior part of the yolk sac and had 24 sarcomere. The anterior part of the body was bent over the yolk sac and started feeding 3 to 5 days after hatching. The bait for the larval larvae includes oyster eggs, diatoms, green algae, copepods, and diets, Artemia, etc. It is necessary to feed different diets at different stages of larval development (see the table below for details). Number of days after hatching Type of bait 3 to 13 Oyster eggs Fertilized eggs 5 to 18 Rotifers 10 to 14 Defective feet 16 to 40 Artemia nauplii 29 to 41 Artificial protein such as cooking protein, rice bran, flour, etc. The temperature is maintained at 20-22°C, and the salinity is 32‰-35‰. The supply water is provided by a water tower and is sterilized by filtration and UV lamps. On the fourth day after hatching, the water in the rearing tank must be diluted with fresh water, and the salinity should be reduced by 0.5‰ per day. On the seventh day, the salinity should be reduced to 30‰. After that, the pool water gradually fades to 20第 on the 30th day. , and keep until hatching, record daily water temperature, salinity, dissolved oxygen, pH, daily determination of nitrate, ammonia nitrogen, sulfide and phosphate. The water quality factors that the fry can tolerate are: 3.00 micrograms of nitrite, 90 micrograms of nitrate, 30 micrograms of ammonia, 9 micrograms of phosphate, and 5 micrograms of hydrogen sulfide. On the first day of dissolved oxygen must be maintained above 0.0007%, pH 7,9 ~ 8.3. The rearing tank must be cleaned daily with a small siphon and the dead seedlings and uneaten feed must be sucked out. Recirculating aquaculture ponds have the advantage of self-purification, while debris concentrated in the center can be discharged by siphoning, or discharged at the outlet of the middle, and the latter is more effective when the water exchange rate is large. Between 30 days and 50 days, the fry grows rapidly and can be fed with wet synthetic feeds and older Artemia and large copepods. For 40 days or less, don't move or catch the eel fry. Therefore, the move will cause all deaths. The move should be carried out more than 50 days after hatching. (b) Fish seedlings Cultured carp seedlings are captured from the sea and domesticated through temporary conservation, or artificial seedlings can be transferred into the fingerling ponds for cultivation after more than 50 days of cultivation. The area of ​​carp fingerling ponds should be 0.07 to 0.15 hectares. The water depth should be 1.5 to 2 meters. The silt in the bottom of the pond should not be too much. The pool water should maintain a certain degree of salinity. In the soil, the fish should be cleaned before the lower pond. Each hectare can be put 3 cm fry 45000 to 60,000, after the fish fry pond, every day before and after the afternoon cast a mixture of barley and bean cake, voted to dry powder as well, is conducive to the feeding of carp seedlings. After the fry are all in the pond, fertilization is started to cultivate zooplankton, and then the amount of fertilizer can be gradually increased. After feeding for about 1 month, the eel fry can grow to 5-7 cm, and then it can be transferred to the culture of adult ponds.
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