Daphnia dauricus juvenile culture technique

Daphnia is a fierce carnivorous fish, with large individuals, fast growth, strong resistance to disease, etc. The market prospect is good, and it has increasingly become an ideal breeding target. However, seedling breeding techniques are not mature, and the survival rate of seedlings is not high, especially in the larval stage. In this paper, we studied the culture of juvenile red pecker, and achieved 94% survival rate. The experimental report is now as follows for farmers' reference.
I. Materials and methods 1. Experimental seedlings: 30,000 waterflies of Daphnia magna.
2. Breeding ponds: round glass steel basins, 10 in number, arranged in a row, basin diameter 2m, depth 45cm, flute water supply, central drainage.
3, feed: from larvae to the end of the experiment using artificial feed, the feed particle size range of 02 ~ 1mm, of which 0 ~ 06mm for the imitation material, the first floating after the sink, micro-particle type, 06 ~ 1mm for the sink pellet feed.
4, oxygenation facilities: an air compressor, the power is 160w. Place two inflatable stones per pot.
5. Breeding methods: The fry can be divided into four stages: water spray, larvae, late larvae and juveniles. At the end of each stage, the fish should be re-screened and sub-potted, with the same specifications for each pot. The average water temperature during the experiment was 18°C.
1 The first stage: water conservation. From the spray to the opening stage, the water level is maintained at 25cm, the water flow rate is 20L/min, and the stocking density is 200 fish/m2. During this stage, the growth of the fish depends on the yolk, which is endogenous nutrition without feeding. The water temperature during this stage is 14~ 16°C.
2 The second stage: larval opening stage. That is, from 175cm to 2cm. When the length of the spray is 175cm, some larvae open up to 2cm in length and all open. This stage is a mixed nutrition period, the water level is maintained at 30cm, the water flow rate is still 20L/min, the feed grain size is 02~04mm, and feeding is performed 12 times per day. Each feeding time is 30 minutes. When feeding, the water supply is stopped. Oxygen supply, the fish absorbs the pollution in time after eating, so as not to pollute the water quality. The water temperature at this stage is 16 to 175°C. This stage is also a crucial stage for seedling cultivation.
3 Stage 3: Feeding stage of larvae. The total length of the fish is 2~3cm, the water level is 35cm, the water flow rate is increased to 25L/min, the feed particle size is 04~06mm, feeding 8 times a day, each feeding time is 40 minutes, the water temperature is 175~195°C, The density is 150 tails/m2.
4 The fourth stage: juvenile fish cultivation stage, the fish length 3 ~ 5cm, the water level maintains 40cm, the water flow is 30L/min, the feed particle size is 06~1mm, feeds 8 times everyday, each feeds the time to be 30 minutes , density 1000 tail/ma2
6, fish disease prevention 1 water mildew: Before the fish grow to 3cm, the water temperature below 18 °C, with malachite green Quanchiposa, even splash two days, the concentration of 03ppm. Select the operation of the screen fish should be light, so as not to scratch the fish body, to prevent the breeding of aquatic mold.
2 Bacterial diseases: When the fish is 3 to 4cm in length, it is diluted with norfloxacin for 2 days. The concentration is 2ppm. Each soaking time is 3 hours, and the baits are taken internally. 15g of oxytetracycline per 100kg of fish is used. Feed every other day.
Second, the results of the experimental period from mid-June 1999 to mid-July, a total of 32 days, of which the feeding period of 20 days, a total length of 5cm, weight 072g, the survival rate was 94? 27%, the opening rate was 98? 86 %, the bait coefficient is 0?91, and the bait rate is 8% to 12%.
III. Discussion 1. During the cultivation of the seedlings, the growth rate of the Daphnia magna is faster, which is almost 15 times that of the aphid. In addition to genetic factors, it is also in the nutrient balance of the feed. The animal protein required by the fish is greater than that of A. cerevisiae.
2. The frequency of feeding and the timing of each feeding are different at all stages of the fry, which is related to the biological learning of the fish and the development of the digestive system. Freshly hatched larvae are in a mixed-nutrition period and consume less food, so feeding time is short. According to the growth situation, the opening time is inconsistent, so it should be voted frequently, up to 12 times a day, so as not to eat feed when the fish is open. The fish is 2cm in length and has been fully opened. At this stage, the fish have to eat. As the fish body grows, the digestive system gradually develops and the gastric emptying time prolongs. There should be corresponding changes in feeding time, feeding frequency and feeding amount. The number of feedings per day was reduced to eight, but each feeding amount increased and feeding time was extended.
3, the preparation of feed to meet the habits of fish activities. Early larvae float more, especially at night, so they use imitation material. The feed first floats and then gradually sinks. As the feed sinks, the larvae are gradually domesticated to the bottom of the pool to feed on the fish so that the upper fish and the lower fish can eat the bait, and the latter can be used as a sink feed.
4. Maintaining proper water levels is conducive to the activities of fish while increasing dissolved oxygen in the pool. The proper flow of water allows the fish to exercise countercurrently and enhance the fish's constitution.

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