Artificial breeding techniques for American anchovies
_ Shi Yonghai, etc
American anchovy (Alosa sapidissima) commonly known as the American anchovy, belongs to the herring family, herring subfamily, herring genus, American anchovy and Chinese anchovy have many similarities, for the river-going migratory fish, similar in size and delicious flesh. At present, the cultivation area of American anchovy in the mainland is expanding day by day, and the number of seed inputs every year is 3 million to 3.5 million, and the breeding prospects are promising. Shanghai Fisheries Research Institute in 1998 took the lead in introducing American anchovy fertilized eggs, began artificial breeding and breeding technology research, after years of optimization of relevant key technical parameters, formed a set of American anchovy artificial breeding and breeding process and technical solutions, to achieve large-scale production.
1. Parental cultivation and selection
1. Parent source and selection
The breeding parents of the American anchovy are artificially raised adult fish and then bred. In the Yangtze River Delta region, in November to December of each year, individuals with pure body color, healthy and no trauma, good fat fullness, and more than 1.5 years of age are selected as reserve parents for breeding in the following year of american anchovies, and moved into the parent pool for wintering and intensive cultivation. The hermaphroditic ratio of the reserve parents is 1:1.
2. Parental cultivation
There are two main ways to cultivate American anchovy parents: one is deep well water + indoor factory breeding parents, which is increasingly questioned due to the use of well water, and this method of breeding American anchovy parents is similar to adult fish farming; The other is the pond greenhouse overwintering cultivation + cement pond adaptive intensive cultivation, the author has found after years of practice, using this method to cultivate American anchovy parents can obtain good results.
(1) Wintering cultivation in parent pond greenhouses. In the Yangtze River Delta region, the parenting of american anchovies overwinters from November to mid-to-late March, and a flexible wire rope plastic film greenhouse is built above the open pond. When the water temperature of the open pond drops to 13 °C, the American anchovy parents are transported through a drag net into the pond greenhouse, and the density of the overwintering parents is controlled at 12,000 to 18,000 /ha, and the puffed feed is fed twice a day (44% crude protein level, grain size 5.0 to 5.5 mm). Wintering water is the local estuary, where conditions permit, the method of first raising salt and then lowering salt can be used to carry out imitation migration regulation, and the salinity control range is 0 to 15. The temperature of the pool water < 12 °C, stop changing the water; The temperature of the pond water is 12~15 °C, and the water is changed once every 2 weeks, and the water transfer is less than 30% of the total pool water; The temperature of the pool water > 15°C, and the water change is changed every 2 weeks, and the amount of water exchange can be increased to 50% of the total pool water. Throughout the overwintering period, the water temperature in the shed is maintained above 10 ° C.
(2) Parental adaptability strengthened cultivation. Generally, from mid-March to mid-April, intensive parental adaptation cultivation begins. Place the parent pullnet into a simple plastic film greenhouse cement pool. The area of the cement pool is 100~200 meters2, the water depth is 1.4~1.6 meters, and the top of the cement pool is arched, and it is covered with a transparent film and a sunshade film to adjust the temperature of the pool water (16~18°C) and the light intensity (300~500 lux during the day). The density of parental intensive cultivation is converted into 0.7 to 2.0 tails/m2, and aeration is 24 hours. The feed feeding method is the same as that of wintering cultivation. Replace the water once every 5 to 6 days, and the amount of water exchanged is 2/3 of the total pool water; every 14 days, the original pond is turned over once, and the water is filtered by pond sedimentation and 60 mesh sieve silk net. Conditional units, especially those with more and larger parental spawning ponds, can move the parents of american anchovy directly from the pond greenhouse to the spawning pond for adaptive intensive cultivation in early April, and then promote production, which can eliminate the need for simple greenhouse cultivation in cement ponds.
Second, parental induction of fertilization
American anchovies reproduce by injecting hormones by artificial insemination and natural mating and fertilization by artificial environment regulation. At present, the breeding of American anchovies rarely uses drug induction methods, and most of them use ecological regulation methods, which can obtain good results.
1. Construction of a circulatory system for inducing labour
The spawning pond is a cement pond with a cone shape in the upper or nearly circular upper part (Figure 1), with an area of 50 to 100 meters2, a depth of 1.2 to 1.3 meters, and a cone bottom depth controlled at 20 to 30 centimeters. The drainage outlet is set at the lowest point of the center of the tapered bottom, which is connected with PVC pipes and the trachea is laid around the bottom of the pool. On the side of the spawning pond, a narrow and long cement tank with a water depth of 1.4 to 1.5 meters is set up, and an air carrying pipe is provided at one end of the pool to carry the water to the spawning pond, and another water pump is set up in the egg collection pond to accelerate the water flow. The egg collection pond is equipped with an egg collection cage with a mesh of 20 to 30 mesh, and the drain pipe is connected to the center of the bottom of the cage. The eggs enter with the water through the circulation pipe and remain in the cage of the eggs. Ring sheds are installed above the procrastination system, which is covered with sunshade film.
Figure 1 Circulatory system of anchovy in the Americas
2. Promote the selection and stocking of parents
From April to May, the selection criteria before parental induction (Fig. 2): females require a large abdomen and a reddish reproductive foramen; Males ask for a reddish foramen and white semen after light pressure. After the parent selection, the male and female are separated into cages with a length of 2.0 meters× a width of 1.2 meters × a height of 0.5 meters, and the temporary rearing density is 10 to 15 females / box, males 20 to 30 fish / box, and the temporary rearing time is not more than 30 minutes.
Fig. 2 Parents of the american anchovy (female on top and male on bottom)
Parental short-distance transport using vehicle-mounted buckets (50 to 100 liters), generally opaque white plastic buckets (Fig. 3), the female fish put 2 per barrel, the male fish put 3 per barrel. After the bucket is put on the car, it is shaded with a double-layer sunshade film with a 75% shading rate, and it is not oxygenated during transportation. The transport time per load shall not exceed 15 minutes. The stocking density of the parents of the induced child is 1.0 to 1.5 fish/m2. The hermaphroditic ratio is 1:(1.1~1.5).
Figure 3 Shipment of the parents of the American anchovy
After the parents are stocked, the circulating water pump is activated from 20:00 to 10:00 the next day for 24 hours. During protopartum period, the light intensity is controlled at 300 to 500 lux and the water temperature is controlled at 18 to 20 °C. Feed once in the morning, subject to 0.5 hours of feeding. Change the water once every 2 to 3 days, 20% to 30% each time, and filter the water through an 80 mesh sieve screen. Where conditions permit, parents can be cleaned up every 10 to 15 days, and new parents can be replenished in time.
3. Fish eggs are collected and washed
Anchovies parents spawn and fertilize in the early morning, choosing to collect their eggs in the morning. Before collecting the eggs, wash the cage pieces and use a 24 mesh soft sieve silk circle to copy the bottom of the cage. The collected fish eggs are mixed with scales and water deposits, which need to be cleaned and separated, and the fish eggs are first rinsed several times with a 24 mesh soft sieve silk circle to remove the water sediments; Another 6 mm mesh is used × 6 mm screen to remove the scales and formed feces; The total volume of eggs is then taken with a beaker volume, counted and moved to the hatchery.
3. Incubation of fertilized eggs
At present, there are two common hatching methods for American anchovies eggs: one is to use the "four big fish" conical hatching bucket micro-flowing water incubation, and the other is the cone bottom cement pool static water inflatable hatching. Now it mainly introduces the hydrostatic incubation method of conical bottom cement tank.
1. Incubation conditions
The hatchery is a cement tank with a circular or square and conical shape in the upper part, the area is 1.0 to 1.2 meters2, the depth of the pool is 1.3 to 1.4 meters, the water depth is 1.2 to 1.3 meters, the drop between the drainage outlet and the bottom of the pool wall is 50 to 60 cm, each pool is provided with 2 aerosol stones, and the top of the hatching pool is provided with a vaulted ring top, and the top is covered with a thermal plastic film and a double layer of austrophe film.
2. Incubation management
Anchovies are slowly settled and transparent. The eggs are moved into the hatchery with water and transported during transport to avoid direct sunlight. The incubation density is 50,000 to 70,000 grains/meter3, the incubation water temperature is 17 to 19 °C, and the pH is controlled at 6.0 to 9.4; the inflatable makes the pool water boil, the eggs tumble up and down without sinking, and the dissolved oxygen of the water body is more than 6 mg/l. Use double-layer awning film to shade the light during the day, turn on the light at night to fill the light, and the light intensity during the day is 800 to 1 000 lux. Change the water once a day, 70% to 80% each time, use a 60 mesh water change frame for drainage, and filter it with a 130 mesh sieve screen when entering the water.
3. Incubation count
Under the condition of incubation temperature of 18.5 ~ 19.5 ° C, the fertilized egg generally after about 30 hours, the naked eye can already see the embryo body in the egg, at this time the number of fertilized eggs is counted, and the fertilization rate is calculated. About 54 hours after fertilization, the embryo begins to rupture the membrane, and then after 24 hours, until more than 98% of the normally developed embryos break the membrane, at this time the number of hatching fish is counted, and the hatching rate is calculated.