Parent cultivation and propagation techniques of cultured tilapia

The reproduction of tilapia does not need artificial aphrodisiac and running water stimulation, as long as the water temperature is more than 20 ℃, mature male and female parent fish can reproduce naturally in the same breeding pond. When the water temperature is stable at 25-29 ℃, fish fry can be reproduced every 30-50 days. In southern China, tilapia can generally produce seedlings five to six times a year, and can reproduce all the year round under temperature control.

1. Breeding pond conditions 1. The location of the breeding pond should be close to the water source, where the injection and drainage is convenient, the environment is quiet, and the transportation is convenient. It is best to choose the pond near the parent fish that overwinters in winter, so as to reduce the damage caused by the parent fish passing through the pond. 2. The area and water level of the breeding pond is generally 2-6 mu, too large is not conducive to the collection of fish fry, the area is too small, the water quality is difficult to control, and the change of water temperature is more obvious. when the parent fish just entered the pond, the water level was controlled between 1.4 and 1.5 meters. When parent fish breed, the water level should be reduced to 0.8-1.2 meters, and can be properly deepened to 1.2-1.4 meters during high temperature in summer. 3. The shape of the pool and the bottom material should be a rectangular pool with east-west length and north-south width, there should be a shallow beach beside the pool to facilitate parent fish to dig nests to produce seedlings, the bottom of the pool should be flat or slightly pot-shaped, and the bottom should be loam or sandy loam. There should be no weeds in the shallows near the pond, otherwise it is not conducive to the collection of fish fry. 2. Before cleaning and disinfecting parent fish in the breeding pond, the breeding pond must be cleaned and disinfected. During cleaning, the pond water should be pumped dry to catch miscellaneous fish and remove bottom weeds and debris, especially the weeds within 1.6 meters from the bottom of the pond to the edge of the pond. Strictly check the edge of the pond, ridge, injection drainage filter is solid, it is best to let the bottom of the pond exposed to cracking. 10-15 days before the parent fish enters the pond, the backwater is 10-20 cm, and then drugs are used to poison the pond. The commonly used drugs are tea meal, bleaching powder and quicklime, among which quicklime and tea meal have the best effect. The dosage of tea meal is 40-50 kg / mu, quicklime is 150-200 kg / mu, bleaching powder is 15-20 kg / mu (available chlorine is 30%). After cultivating the water quality for a few days, draw the net with a close-eye net to check whether the pond has been disinfected and clean, and after confirming that there are no other miscellaneous fish and sundries in the breeding pond, you can return the water (the water inlet must be filtered with a dense net when entering the water, and always check and clean the net), apply base fertilizer, 300-600 kg of fermented manure per mu or 500-800 kg of green manure per mu, it is appropriate to control the water quality as tea green or yellowish green (such as green manure). It should be turned frequently. After all the grass residue is rotted, the grass residue will be picked up and disinfected for 7-10 days, then the fish can be released in the water. Three-parent fish stocking 1, parent fish selection as parents of tilapia, must be purebred, in the same population should choose fast-growing, larger individuals, generally overwintering fish species should be more than 250g, male fish slightly larger, stay big to small. When selecting, the selected parents are required to have high back, thick flesh, complete scales and fins, bright color, clear markings, disease-free and injury-free, neat body shape, and external morphology in line with taxonomic standards. 2. When the parent fish is put into the breeding pond, the water temperature should be more than 20 ℃. In Guangdong, pairing can be carried out in the middle and last ten days of March. Because of the superior natural climate in Hainan, pairing and breeding can be carried out all year, and the stocking of parent fish should be carried out on a sunny day and in full quantity at a time. The parent fish should be disinfected before entering the pond. The parent fish should be soaked in salt water of 3 ‰-3.5 ‰ for 5-10 minutes before being put into the breeding pond. The operation of transporting the parent fish should be light, reduce the damage to the fish body as far as possible, shorten the recovery time of the parent fish, and produce seedlings earlier. After all parent fish entered the pond, chlorine dioxide with 0.3ppm concentration was used for disinfection to prevent wound infection and water mildew of parent fish. 3. The stocking density and male and female ratio of parent fish should be determined according to the dissolved oxygen capacity of pond water, pond conditions and production quantity. In the normal temperature pond, a 1.5-2.2 kilowatt aerator should be equipped with 2000 cubic meters (about 3 mu) of water. The stocking density can reach 1500-2000 pieces per mu, with specifications of 250,300g. The static water thermal insulation and aeration tank covered with plastic film sooner or later, the stocking density of parent fish is 1000-1200, and the specification is 250,300g. The male-to-female ratio must be properly controlled when stocking. According to the production experience of our institute over the past few years, the female-to-male ratio of 2.5 to 4:1 is better, because when the male fish are mixed in more, if there is not enough feed, the fry will be swallowed in large quantities, seriously affecting the seedling yield. After a long period of overwintering, the cultivation and management of parent fish have weak physique and poor gonadal development, so it is necessary to strengthen the cultivation. The feeding method of adult fish should be strengthened according to the combination of fertilization and feeding, and feeding and fertilization should depend on the weather and the feeding of parent fish. The daily feeding amount is generally 3% of the weight of parent fish in the pond. In order to promote the gonad of parent fish to develop and mature as soon as possible, feeding requires the combination of concentrate and green feed, diversification, and comprehensive nutrition. The protein content of the concentrate feed for parent fish should be more than 35%. The commonly used feeds are soybean meal, fish meal, corn meal, peanut meal, and yellow meal as the feed for parent fish, and it is best to make pellets after purchasing raw materials. After parent fish enter the pond, they should persist in patrolling the pond in the morning, in the middle and in the evening, timely remove frog eggs from the pond and kill enemy pests, especially strengthen the management of water quality. when the water color is too thick or dark brown, effective measures should be taken in time to change part of the new water or sprinkle lime to prevent the loss caused by anoxic floating head and flooding pond caused by the deterioration of water quality. Adhere to regular disinfection of breeding ponds and regulation of water quality, generally apply quicklime once a month, the dosage is controlled at 10-15 kg per mu. Some microbial preparations are applied regularly to change the microbial community in the pond and improve the aquatic environment. 4-parent fish fry 1. After the parent fish is released, when the water temperature rises to 22 ℃, the mature parent fish begins to oestrus and spawn. The hatching of fertilized eggs and the feeding of fry are carried out in the female's mouth, hatching in 5-6 days at 25 ℃ and hatching in 4-5 days at 28-30 ℃. The whole process is about 10-15 days from oestrus and spawning to fry living independently from the mother. Therefore, it is necessary to observe carefully whether there are fry activities around the pond every day after parent fish stocking for 10 days, so as to catch fry in time so as to improve the rate of getting fry. 2. Seedling fishing is generally carried out in the morning or evening, and a better method is to operate the net by hand, small trawl, fishing around the pond, once every 3-4 meters, and the seedlings are temporarily raised in the cage, so repeatedly, they should be fished 4-5 times a day. Try to clean the seedlings as much as possible every day. When fishing for seedlings, the action should be light and fast, and after a certain number is obtained, the seedlings can be transferred to the culture pond and transferred to the stage of fish fry cultivation. Because tilapia have the habit of cannibalizing each other at the seedling stage, the fry with a body length of 1.5 cm can already swallow the seedlings that have just left the mother body. In production, the fry can be combined with the fry, and the sinker on the bottom class should not be overweight, so that the parent fish can escape from the bottom of the net. Several problems that must be paid attention to: 1. Water temperature parent fish should cool the overwintering pond before moving to the breeding pond, wait for the water temperature to be the same as the outside world, stop feeding and flush fresh water 3 days before leaving the pool, and be careful when crossing the pond to reduce fish injuries. because the water temperature in this period is generally not high, parent fish wounds are extremely prone to water mildew, except for sunny weather when moving the pond. It must be sterilized before it is put into the breeding pond. 2. Water quality is a key link in the production of parent fish seedlings. The water quality can not be too fat or too thin, too fat parent fish is very easy to lack oxygen floating head; too thin is not conducive to the cultivation of open bait for parents and seedlings. Adjust the water quality, use quicklime regularly, often change part of the old water and inject new water in the high temperature season. It is recommended to use some microbial preparations to improve the water quality and increase the dissolved oxygen. 3. Another key link in the seedling production of parent fish is bait. As the bait of parent fish, the quality of strengthening cultivation must be achieved, and the various components contained in the feed must be very clear. Only when parent fish absorb enough protein energy, can the interval of seedling production be shortened, the times of seedling production be increased and the seedling emergence rate be increased. 4. Separation of male and female tilapia has the phenomenon of stopping or reducing seedling production during the period of high temperature in summer, and the seedlings are extremely difficult to collect. At this time, the parent fish can be separated, separated and cultivated in ponds, and then paired to produce seedlings when the water temperature is below 30 ℃. The purpose of this is to collect a group of concentrated seedlings, which is beneficial to seedling cultivation and overwintering.