Anti-seasonal breeding of sweet fish

I. facilities and methods

(I) facilities

1. Nursery room. Transformed from a plastic shed, 500m3 of water, black shading net to adjust the light intensity, control the light intensity below 5000 lux.

two。 Parent fish culture pond. Cement pool, rectangular (3 meters × 2.65 meters), pool depth 1 meters, as well as bait pond and breeding pond.

3. Water supply facilities. The groundwater is used and the water is supplied by pump through the main and branch pipes.

4. Inflatable equipment. There are 2 sets of ordinary air pumps, and one loose air stone is put in the seedling pond every 1 to 2 square meters.

5. Heating and power supply. The heating adopts a 0.2-ton small heating furnace with its own small generator.

(2) method

1. Off-season cultivation of parent fish

To take technical measures to make fragrant fish reproduce from early September in natural water to late May in spring, the key lies in how to shorten the gonadal maturation time. In this experiment, under the premise of ensuring sufficient nutrition for fragrant fish to eat in cement ponds in plastic greenhouse, the gonads of fragrant fish reached Ⅳ stage at the end of April, transition to Ⅴ stage in May, spawning and fertilization in late May, and breeding from autumn to spring.

Since October 2003, this study has been carried out and four models have been used for comparison. Mode one only increases the temperature without increasing the light. Mode 2 does not increase the temperature or light. Mode 3 does not increase the temperature, but only increases the light. Mode 4 increases the temperature and light.

two。 Out-of-season cultivation of fish fry

The main results are as follows: (1) the open bait was propagated in anti-season at the end of 2004, and the substitute feed was used as the opening bait for culturing the seedlings, mainly yeast and micro-compound bait. Rotifer was used as the main opening bait during off-season reproduction in 2005. Rotifers are fortified with Chlorella, photosynthetic bacteria and spirulina.

(2) the food series adopted in 2005 is rotifer-fish-worm-synthetic diet.

The rotifers in each pool were 1011 / ml, 8 / ml, 1 / ml and 5 / ml, respectively.

Fish and insects are harvested from rivers and lakes, mainly cladocera, copepod and chironomid larvae, water @ 254fish, and so on. The main nutritional contents of the synthetic diet are as follows: protein 45%, crude ash 12%, calcium 0.5%, crude fat 10%. Take the way of uniform casting, bait 5 times 6 times a day, when the body weight is more than 5 grams, reduced to 3 times. The initial feeding amount is 7%-8% of the body weight. When the weight of the fry reaches about 20 grams, the feeding amount is 5%-7% of the body weight, and when the body weight is more than 60 grams, the feeding amount is 3%-5% of the body weight.

(3) the salinity was adjusted by sea crystal and table salin. when the fry reached more than 1 cm, the salinity increased gradually, increasing by 0.3 ‰ ~ 0.5 ‰ every day, and stabilized for a week when the salinity reached 8 ‰. Then it decreased gradually and adjusted to zero with a daily decrease of 0.3 ‰ ~ 0.5 ‰.

(4) Water quality management changes water once a day, and the amount of water change each time depends on the water quality, which is generally 1, 3, 2 and 3 of the total amount of water in the pool, and the residual bait and dirt from the bottom of the pool are often sucked out.

(5) the water temperature is controlled to keep the water temperature stable at 20-22 ℃.

II. Results

1. Parent fish cultivation

In the fourth mode, under the condition of increasing both light and temperature, more than 90% of the parent fish matured by mid-May 2005. On May 23, the group spawned and reproduced. In the 234 group, 2.82 million eggs were obtained, including 1.549 million fertilized eggs, with a fertilization rate of 55%. 1.1 million seedlings were hatched and the hatching rate was 54.9%. It shows that under the condition of meeting the nutritional needs, increasing the light and increasing the water temperature can promote the parent fish to mature ahead of time and achieve the purpose of off-season reproduction.

two。 Fish fry cultivation

Using rotifer as opening bait is the key to success, and the quantity and quality of rotifer are the key factors affecting seedling emergence. When the number of rotifers is 10: 11 / ml, the emergence rate is the highest (81%), and the lowest at 1: 3 / ml (40%).

III. Discussion

1. On the off-season cultivation of parent fish

Temperature and light are two important factors to promote the gonadal development of fragrant fish, and they restrict and complement each other. When only increasing the temperature without increasing the light time, the fish is 18 centimeters long and weighs 90 centimeters and 110 grams in May. although the fish grows very fast, the fish will develop physiological disorders, leading to diseases, such as redness and swelling of the liver and ascites. Die soon. If the temperature and light are not increased in winter, the parent fish can also achieve sexual maturity under the condition of artificial cultivation, but the maturation time will be delayed very late, which will be delayed until August to September in the north, which can not achieve the purpose of out-of-season hatching. In the fourth mode, it is best to increase the temperature and light at the same time. Under this condition, although occasionally a small number of parent fish have some physiological discomfort and abdominal stagnant water, as long as some vitamins are added to the diet, the symptoms will be relieved or disappeared.

About the effect of "short day" treatment on parent fish. "short day" treatment can promote gonadal maturation, but it can only show its effect when the gonad of parent fish is well developed, that is to say, "short day" treatment must be carried out on the basis of increasing temperature and light at the same time. In order to get obvious results.

As for whether the temperature and light can be further raised to 22 ℃, or higher, and the light time can be increased to more than 6 hours per day, it needs to be further discussed.

two。 On the off-season cultivation of fish fry

The main results are as follows: (1) the selection of opening bait is an important link in the cultivation of fragrant fish, and the best opening bait of fragrant fish is live rotifer. The fragrant fish fry hatched in September 2004 used substitute bait, resulting in a significant decrease in the survival rate. When the individual reached 1.6 cm, the survival rate was only about 1%, while rotifer was used as the main opening bait in June 2005, and the survival rate was 82%.

(2) the self-nutrition of rotifer will also affect the survival rate of rotifer. Chlorella, photosynthetic bacteria and algae powder are used to strengthen the cultivation of rotifer, and the effect is very good.

(3) the rotifer density is very gluttonous and the food intake is very large. The practice shows that when the rotifer density in the water is more than 6 / ml, the larvae are full, but when the rotifer density is less than 6 / ml, the gastrointestinal satiety of the larvae is insufficient, which directly affects the survival rate of the larvae.

3. On the adaptability of fragrant fish fry to salinity

The fish fry bred by parent fish collected from natural waters have different ability to adapt to salinity. The former adjusts the salinity to 8 ‰ ~ 10 ‰ and the survival rate is higher. The latter can adjust the salinity to 3 ‰ ~ 5 ‰. Up to the time of acceptance of this test, the salinity of fry bred by parent fish was only 2 ‰ ~ 3 ‰, and no abnormal phenomenon occurred.

4. About the disease of fragrant fish

The most common diseases of fragrant fish are parasitic disease, vibrio disease, enteritis and so on. For general diseases, 0.2g / m3 crystal trichlorfon can be used, or 0.3 g / m3 copper sulfate and ferrous sulfate mixture can be sprinkled all over the pool.

IV. Existing problems

1. problem

In the course of this experiment, some parent fish have reached the end of their "physiological cycle" before they reach gonadal maturation, and some healthy fish gonads mature and die for no reason before spawning. The mechanism of this phenomenon is not clear. Whether it means that the "gonadal development cycle" and the "life cycle" of fragrant fish have a synchronous process, perhaps temperature and light, which factor makes the life cycle too fast? Arrived early and died. If this is the case, it is necessary to further adjust the illumination time and the range of temperature increase, which is only an assumption and conjecture, and its mechanism needs to be further studied and discussed.

two。 Conclusion

Temperature and light are two important factors affecting the gonadal development of fragrant fish in out-of-season hatching. it is feasible to increase the temperature and light time by technical measures to promote the reproduction of fragrant fish in spring. The best opening bait for fragrant fish is rotifer. Rotifer should be strengthened to ensure its quality and quantity. It is also necessary to make the rotifer feeding density more than 6 million 7 per milliliter, otherwise it will not be able to meet the feeding needs of fish fry.