First, rotifers as the main bait for pod-like larvae
The traditional method of cultivation in the cocoon stage is based on feeding, fertilizing and inoculating unicellular algae in the nursery room, and is mainly fed with spirulina powder, egg yolk, yeast and other baits. The authors fed the above-mentioned baits on the evening of the larvae hatching in the cocooning period this year, and began to feed live rotifers or refrigerated rotifers with better quality in the daytime during the day and the results were good. Mainly have the following characteristics:
1. When the metamorphosis-rapid rhizomes are fed with substitute feeds such as spirulina powder during the whole period of the cockroach, the cockroach-like period is about 3-4 days or longer when the cocoon stage is metamorphosis, and 2.5-3.5 days when it is predominantly rotifer.
2, metamorphosis in the completion phase of the main substitute bait, because of its longer metamorphosis, abnormal metamorphosis, the cumulative difference in each phase to the later, the larvae of all metamorphosis to big eye larvae often need 2-3d At the time, due to serious fratricide at this stage, the yield of crab seedlings was greatly reduced, while rotifers mainly solved this problem.
3, juvenile Zhuang rotifer-based cultivation of zoea larvae not only large individual, but also good vigor, strong resistance to disease. For example, there was a serious filamentous bacterial disease in the nursery pool this year. However, after careful treatment and cultivation, it was miraculously metamorphosis to the burrow-shaped larvae, the metamorphosis rate was as high as 90%, and the single water body emerged to more than 500 g.
Second, micro-quantification of residual bait amount in nursery pond
In the process of crab breeding, proper feeding of bait is one of the key technologies. It is usually handled flexibly according to the larval stage, the number of larvae, the feeding conditions of the larvae, the type of bait, and the condition of the bait. The amount of residual bait is the main basis for judging whether the amount of bait is appropriate or not. Live baits, dead baits, feces and larvae are mixed together in actual breeding waters, and it is very difficult to observe directly with the naked eye. The method I used was to use a porcelain bowl to draw water from the seedling pool. After a few minutes of stillness, a dropper was used to collect sediment from the bottom of the bowl. The observation was performed under a low magnification microscope to clearly distinguish the residual bait situation and combine the previous shot. The bait time and quantity can accurately determine whether the feeding amount is appropriate or not, and provide an important basis for timely adjustment of the type and quantity of feeding.
III. Cultivation of water under higher densities of the braided v larvae
The crab bigeye larvae have the habit of slaughter and killing of the wartous v larvae. During the metamorphosis of the zoea v larvae and big eye larvae, if the larval density is too large and the feed is insufficient, the killing phenomenon will occur easily, and the crab seedlings will be greatly reduced. Yield. The author of this year, for the pool with a higher density in the braided stage v larvae, change the amount of water before the metamorphosis, and use the water flow method to change the water in the metamorphosis process. That is, one end of the nursery pond is siphoned and drained with a cage, and the other end is filled with water to keep the seedling pond water level basically stable. Each inflow of water is 1/3-1/2 of the water holding capacity of the nursery pond, which avoids the change of water levels during routine water changes. The decrease in the larval density increases the size of the larval larvae. At the same time, the amount of diets such as large Artemias and freshwater turtles has increased. Therefore, this year's cockroach v phase - bigeye larvae metamorphosis stage lighter, crab production significantly increased.
Fourth, live rotifer ice preservation
In the production of crab breeding, the time and number of rotifers are often unstable. Sometimes the number of rotifers acquired is too large to be fed in a short period of time. If no measures are taken, the remaining rotifers will die after a few hours, which not only causes great waste, but also seriously affects the normal bait feeding of crab breeding.
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