A Detailed Explanation of Fry Breeding Methods and Key Technical Points

Fry are also called “fish flowers”. They are young fish not long after hatching, generally 6-9 mm in body length. There are artificially bred fry and natural fry from rivers. So, how do fry reproduce?

1. How do fry reproduce?

Scoop out mature male and female brood fish and place them in a basin, grasp the male and female brood fish with both hands, with their anal vents facing each other, gently squeeze the abdomen, and when the eggs of the female fish and the milt of the male fish are seen being expelled, gently stir the water surface with your hand to distribute the eggs evenly over the mesh net. Place the mesh net in a foam box with green moss, expose it to sunlight, and a temperature of 22-26°C is suitable. Remove the unfertilized eggs every other day, and after the eggs are fertilized, wait for the fry to hatch. Once the fry have hatched, you can prepare the first feed.

2. What first feeds are there for fry?

1. Rotifers

Rotifers have good palatability, the highest crude protein content, crude fat content second only to egg yolk, and they contain large amounts of the unsaturated fatty acids essential to fry, giving them high nutritional value. Their swimming speed is below 0.02 cm/s, and they are distributed fairly evenly in the water layer. Rotifers can grow and reproduce in the nursery water body, which not only keeps their nutrients stable but also causes almost no pollution to the nursery water quality. In addition, research on rotifer cultivation methods is very extensive and the cultivation technology is relatively mature, which can ensure a sufficient source of rotifers. Therefore, rotifers are an effective way to solve the problem of first feed for fry, reduce production costs, and increase the survival rate and quality of fry.

2. Algae

Algae are smaller than rotifers and are suitable for use as first feed in the early stage of fry feeding. As the fry grow and their mouth gape widens, rotifers become their most suitable feed. The two can complement each other.

3. Egg yolk

Egg yolk is a commonly used first feed for fry. In production, the egg yolk can be filtered through an 80-mesh silk sieve to make the egg yolk particles smaller, so that they are distributed evenly in the water in a mist-like form, and the suspension time can be kept at about 1 h. If the feeding amount is controlled within an appropriate range, the egg yolk can be fairly well consumed by the fry. However, it should be noted that this kind of feed settles and disperses easily, and after entering the water it easily causes water quality deterioration, resulting in slow growth and a low survival rate of the fry.

4. Soy milk

Soy milk is rich in protein and can meet the nutritional needs of fry, but soy milk has low nutritional value, is not easy to digest, has a low absorption rate, easily forms suspended matter in water, affects dissolved oxygen, and ferments easily. Therefore, most soy milk mainly plays a role in fertilizing the water, prompting the rapid reproduction and growth of plankton in the water body and indirectly providing feed for the fry.

5. Aquatic preparations

Aquatic microecological preparations are small in size, have no toxic side effects, no pollution and no residues, can effectively improve the breeding ecological environment, enhance immunity, inhibit pathogenic microorganisms, and can greatly increase the growth speed and survival rate of fry.

The success or failure of fry cultivation directly affects economic benefits, so everyone must be even more careful during the nursery breeding process.