The "Direct Matching" and "Adaptive Matching" methods (referred to as indirect matching) were used to perform a single pair of spawning for a male and female of the winter months, and hatching comparisons between "fishing eggs" and "family brooding eggs" were conducted at the same time. Observation of water sports seedlings, combined with domestic fish breeding techniques, discusses the characteristics of crescent moon breeding and fry growth.
Key words Moonslip, pairing, breeding, Channa asiatica is a scorpion-headed fish. It is a freshwater wild fish, commonly known as the seven-star fish and the star fish. Because of its delicate meat, good taste, and blood, muscle and nourishing functions, it has attracted attention in the fresh aquatic products market in South China, Hong Kong, Macao and Southeast Asia. However, because of resource and breeding technology constraints, it is difficult to form a large-scale breeding, the price remains high for a long time, and the supply of food fish is in short supply. How to develop the Yueshao into the domestic industrialization and make it meet the market demand has become a major issue for fishery workers. Lin Gang, Tang Yong, and Chen Yijun have conducted research on the biological characteristics and culture of Yueshao. Based on this, this article makes a systematic exploration of the breeding and fry cultivation techniques of the first-instar moontail.
1 Materials and methods
1.1 The source of broodstock and the cultivation of broodstock were unselected food fish purchased from a farmer's cement pond in Binyang County, Guangxi Province on December 20, 1997 (each pond was originally hatched in April 1997), and each body weight 56— 102 grams, weight 93 grams. On the same day, two 6.551.2m3 cement pools were placed in Guangxi Fisheries Station for pre-natal cultivation, and 21 fish were released per square meter. Keep water depth 0.6-0.8m during cultivation. The cocoon, prawns and adult clams were fed with compound feed and fed according to changes in water temperature. From December 1997 to January 1998, the cocoon was mainly used, and the daily feed was 1-2% of the total weight of the fish. In February-April, the additive feed was mixed with adult shrimp to make a slug. The daily dosage is 2-5% of body weight, twice daily (9:00 and 17:00). Regularly use 0.3-0.4ppm strong chlorine to disinfect pool water and change water regularly. Each change of water volume is 1/2 of the original pool water.
1.2 Pairing of broodstock spawning On April 1, 1998, mature individuals with antenatal intensive cultivating for 3 months and weighing more than 60 g were selected (examination of the gonadal at 12 tails before pairing), according to the ratio of male to female ratio of 1:1. Pairing spawning; a 50cm diameter, 45cm high tile cylinder for the spawning pool, the water depth 30-35cm. Cage mouth plus cover to prevent escape; and bovine liver feeding paired broodstock, feed twice a day, each feeding amount of 1-2% of broodstock. Change the water every 1-2 days (exchanging about 2/3 of the original pool water) to keep the water fresh and odor-free.
1.3 Incubation and nursery are hatched using egg-laying and broodstock egg-protection methods. The former will remove the eggs that have been produced and floated on the surface of the water and move them into a special pool (a simple pool or plastic tray with a diameter of 40-60 cm) to hatch. Keep the depth of the pool 10-15cm. 1300-4000 eggs per square meter, pay attention to changing the water; the latter will leave the original egg spawning pool for spawning. When the same batch of fertilized eggs hatched and emerged, the yolk gradually disappeared, and some of the small seedlings that started feeding were moved into a nursery pond with an area of ​​0.76 m2 (a brick was placed on the concrete floor to form the corresponding “plaid†and covered with a thin film). 2620 seedlings per square meter. The fry grows to a total length of about 20mm, and the seedlings of 1.3m2 are transferred into the secondary pool for cultivation, and 1284 flies per square meter (see Table 1). Take overfeeding (the amount of the daily dose is the same as the day after the day of feeding), feed it with zooplankton or leeches, and change the water depending on the water quality.
2 Results and Analysis
2.1 The development of gonadal of 1st-month lunar mandibular larvae was purchased in December of 1997. Eight months old lunar cramps were purchased and cultivated until February 8, 1998 (10 months old). The gonads generally reached stage III. The average maturity is 2.16%. By April 1998 (12 months of age), the gonads reached stage IV with an average maturity of 4.44%. See Table 2.
In Table 2, samples 3 and 8 are in the same gonadal development stage, with a maturity of 20.7, but a 0.7-fold difference in body weight. It is suggested that the gonad maturation degree of a winter monk depends on the age, not the size of the individual.
2.2 Identifying and mating moons, especially males and females of the first month of the month, do not have different "star-chasing" characteristics like those of the family fish, nor do they have distinct features such as tilapia, squid, and black hole. It is difficult to distinguish between male and female. In addition, there is severe fighting disability in the mating process of the 1st-month lunar new year. Therefore, whether or not the male-male is properly selected and paired is critical to successful reproduction. This test is based on abdomen enlargement, light pale color, elastic, pale anal fin color, scattered silver-gray spots at the base, a little garden blunt and other characteristics of the choice of female; according to the deep abdominal color, anal fin base and genital hole around There are dense silver-gray spots, head slightly pointed and other characteristics of the selection of male fish, male and female accuracy of 98%. According to the requirements of the grouping, the identified male and female fish are respectively collected in the "preparation pool", and then the male and female individuals of equal individual size are selected to pair each other. From April 1st to May 4th, there were 100 pairs of matched pairs, of which 55 pairs were directly paired (male and female were directly paired into spawning pools after selection). Indirect pairing of 45 groups (each group of broodstocks were adapted to a “pool†with an area of ​​1.2m2), followed by continuous observation, and found that one of the tails of the brooding fish was removed immediately, and then the same sex was added to the broodstock until one to two days later. No fighting party moves into the spawning pool.) Comparing the two different pairing methods, if no fighting occurs within two days after entering the egg pool, the success rate of direct matching is 3.64%. The average success rate of indirect pairing was 54.56% (see Table 3). Among them, the success rate of one-to-one matching period was 27.7%, the success rate of one to two days was 50%, and the success rate of two days or more was 86.62%. It can be seen that the success rate of indirect pairing is much higher than that of direct pairing success rate in the breeding and mating groups of 1st instar larvae, and 48 hours or more is an ideal pairing adaptation period.
2.3 Fertility
(1) Spawning volume On April 1, 1998, 12 females were dissected to examine the gonads before pairing. Ovarian development reached IV in each sample. The amount of eggs was counted by weighing method, and the relative fecundity was 15-32 grains/g body weight. The average relative fecundity was 22.0% grain/g body weight. See Table 2. The “9†and “10†samples of the same weight in the table had relative fecundity of 16 and 29, respectively, which was 1.8 times that of the former. Maturity also has a similar situation. The correlations between body weight and relative fecundity were analyzed, r=0.013<r0.05(10)=0.576, P>0.05, and there was no significant correlation between the two.
(2) The spawning amount has successively counted the statistics for the first time spawning of 11 groups of fish. The absolute fecundity of each female is 1106-3629, with an average of 2348 eggs. The relative fecundity of 27 grains per gram of body weight and relative fecundity were analyzed. r=0.55<r0.05(9)=0.602. P>0.05, similar to the relationship between body weight and fecundity, there was no significant correlation between body weight and fecundity. It shows that the size of the individual has little effect on the amount of eggs, sexual maturity and fecundity of the 1st instar nymphs.
2.4 Comparison of hatching eggs and brood brood eggs hatching: The eggs of quail eggs are buoyant eggs. The hatching of eggs can be done by hatching the other eggs and leaving the original spawning pool to hatch. However, the hatching effect is obviously different. . In this experiment, fertilized eggs of 11 groups (batch) were given two different hatching treatments of “fishing eggs†and “occlusion†(there were only treatments between different groups here). The result was that the former had a hatch rate of 87.8%. The latter hatching rate was 71.7%. With hatching as an indicator, hatching hatching increased by 22.7% over hatching hatching, as shown in Table 5.
2.5 fry breeding a breeding stocking density of 2040-3820 per square meter, water depth 3-5cm. During the fourth day of feeding from the mouth, small zooplankton filtered through a 60 mesh net were fed; from the fifth day to the ninth day, zooplankton and fully minced leeches were filtered through a 40 mesh screen. After 9 days, the average survival rate was 83.9%, an increase of 1.43mm. The secondary stocking density was 946 to 1940 per square meter with an average of 1284 tails/m2 and a water depth of 5-10 cm. The feed is mainly leeches, and beef liver (chopped) is a supplement. After 4 to 5 days, the survival rate was 97.7%, and the average daily growth was 2.16mm. See Table 1. From Table 1, we can see that the water temperature at 24 - 28.5 °C when the seedling period (refers to the disappearance of the yolk from the mouth to the full length of about 30mm) 13-14 days. The whole process was fed by “overfeedingâ€. The “absolute growth†level was slower than the secondary level, and the daily growth rate was faster than the secondary level at the first level and similar to the growth characteristics of the fry. .
3 Summary
(1) 1 Winter months Moons can reach IV stage after artificially cultivated gonadal development, with a maturity of 3-6%, reaching spawning level, and relative fecundity of about 20 grains per gram of body weight. influences. In the case of reasonable matching (male and female individuals, maturity is more synchronous), environmental conditions (water temperature 23 °C above), without the need to inject aphrodisiacs can also produce eggs, the relative amount of eggs for 20-50 / g body weight. However, when paired directly, broodstock fights have serious injuries and the success rate of pairing is low. Indirect pairing methods are used to pair spawns in a ratio of 1:1 male to female. The success rate of pairing is relatively high, which can reduce the fighting and death of the broodstock during the pairing process.
(2) The eggs of the moon have a certain degree of stickiness, and they can be aggregated into masses and float on the water after they are produced. In the breeding season (April-June), the egg can be kept in the original pool for egg hatching, or the eggs can be removed and hatched into a hatching pool. The latter can increase the hatching rate by more than 20% compared with the former. In addition, the hatching and hatching management of eggs is more convenient, and the growth of fry is more synchronous, which is suitable for fry-scale production.
(3) Moons have strong adaptability to the environment The pH value can grow normally between 5 and 8. There is no special requirement for the size of the water body and the structure of the fish pond, and the requirement for oxygen is not high. The stocking density of fry is 1000-2500/m2. In the area of ​​0.76-1.5m2, the water depth of 3-8cm of small water feeding, zooplankton and leeches for feeding (bait) material, after 13-14 days of cultivation can achieve a total length of about 3cm out of the pool specifications, the average daily growth The rate reached 10.14 to 13.18%, and the survival rate was over 90%. However, it was necessary to change the water in a timely manner to ensure that the nursery water had no peculiar smell.
(4) Comparison of fecundity and fecundity A total of 12 females with a body weight ranging from 70 to 112 g were quarantined on April 1, with an average of 22 eggs per gram of body weight. In Table 3, spawning weights of 50-135g, the relative spawning capacity of the initial spawning is 27 grains per gram of body weight, and the amount of eggs laid is greater than the “egg sizeâ€. The amount is much greater than the "feast." This is in addition to the data from different individuals and the detection methods are different (the amount of eggs is the weighing count, the amount of egg-laying is counted by the grain). It also shows that the 1st instar in the reproductive season. The ovaries are visible to the naked eye. In the third and fourth stage of the egg, there are still egg cells in phases I and II. The number of ovary in each phase of its ovary and its development law need to be further studied.
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