A Detailed Guide to Artificial Breeding Methods and Precautions for Loach
Loach (Misgurnus anguillicaudatus) belongs to the family Cobitidae. Loach is known as “ginseng of the water” and is distributed throughout southern China; it is uncommon in the north but is also found in various places there. It can be harvested year-round, most abundantly in summer. After capture, loach can be used fresh or dried. Loach lives in lakes and ponds, and its body is small, only three or four cun long. Its body is round and short, with small scales beneath the skin, and its color is blue-black. Its whole body is covered with its own mucus, making it slippery and impossible to grip. It is a fish with very high nutritional value. It differs from other fish in appearance, body shape and living habits, and is a special kind of loach. The body is slender, with the anterior portion slightly cylindrical. The posterior part is laterally compressed, the abdomen is round, the head is small, the mouth is small and inferior, and horseshoe-shaped. The eyes are small, with no subocular spine. There are 5 pairs of barbels. The scales are extremely small, round, and buried beneath the skin. The back and both sides of the body are grayish-black, and the whole body has many small black spots. There are also many black spots on the head and each fin. The spots on the membranes of the dorsal fin and caudal fin are arranged in rows, and there is an obvious black spot at the base of the caudal peduncle. The other fins are grayish-white. Loach is widely distributed in China, Japan, Korea, Russia and India along the coast of Asia, and can be eaten and used as medicine.
Artificial breeding of loach is very important for loach farming, so farmers need to pay close attention to it. So how is artificial breeding of loach carried out? What needs attention?
Artificial breeding
Selection and cultivation of parent loach: Parent loach comes from fishing in rivers and ditches. 7-10 days before use of the cultivation pond, spread 20cm of fertile mud on the bottom of the pond, sprinkle 150-200g of quicklime per square meter over the whole pond for disinfection, and fill with water to 40-50cm. The water used for filling should be filtered through 40-mesh silk gauze to prevent harmful organisms from entering the pond, and iron wire should be used at the inlet and outlet to set up escape-prevention nets. After the water temperature stabilizes at around 18°C in early May, select loach with a body length of 15-20cm, a body weight of 30-50g, a strong constitution, no disease or injury, and good gonadal development as parent fish. The pectoral fins of female loach are relatively short, with the front end rather round and blunt, fan-shaped, and when at rest the fin rays spread out on one plane. The pectoral fins of male loach are relatively long, with the tip of the front edge turning upward. Put the captured parent loach into the cultivation pond at a female-to-male ratio of 1:2 for intensive cultivation, with a stocking density of 8-10 fish per sq m. During the cultivation period, mainly feed animal-based feeds such as minced animal meat, minced internal organs and fish meal, with a daily feeding amount of 5-8% of the body weight of the parent loach, supplemented with a small amount of plant-based feeds such as rice bran, wheat bran and fresh tender aquatic plants. Since loach likes to forage at night, feeding should mainly be done in the evening. Flush and replace with new water once every 2-3 days, each time replacing 1/4-1/3 of the pond water.
Artificial induced spawning
Around May 20, after the water temperature on sunny days reaches above 20°C, select parent loach with mature gonadal development from the cultivation pond. The abdomen of female loach is round and large, and when the abdomen is gently pressed, colorless transparent eggs flow out. Male loach has abundant semen, and when the abdomen is pressed, milky-white semen flows out. Artificial induced spawning all uses intramuscular injection. Each female loach is injected with 800-1000 international units of chorionic gonadotropin, and the dose for male loach is halved. A 1 ml syringe and a No. 4 needle are used for injection. Intramuscular injection is made on both sides below the front of the dorsal fin, with the needle pointing toward the head at a 45° angle to the parent loach, and the insertion depth is about 0.4cm. Female loach is injected with 0.2 ml, and male loach with half that amount. After injection, to facilitate artificial insemination, female and male parent loach are placed separately into two net cages (1m×1m×0.5m, mesh 0.3-0.5cm) in the cultivation pond, and estrus and spawning are observed so that artificial insemination can be carried out at the right time.
Artificial insemination
Before spawning, the female loach swims in front, and the male loach closely follows behind. During estrus, loach are mostly active at the water surface. Parent loach injected with spawning-inducing agents at a water temperature of about 20°C can become sexually excited and spawn after 20 hours. When female fish are found spawning, immediately take out the parent fish for dry fertilization. Wipe the surface water off the body with a clean towel, squeeze the eggs of the female loach into a porcelain bowl, porcelain basin or plastic basin, and immediately squeeze the semen of the male loach. The eggs of one female loach are matched with the semen of 2 male loach. Stir with a feather for about 3 minutes to mix the semen and eggs evenly. After full fertilization, scatter them on the fish nest and place them in the hatching pond for still-water hatching. The fish nest is made of washed willow roots and small grasses tied into small bundles and disinfected with a 20ppm potassium permanganate solution. The entire fertilization process should avoid strong light.
Artificial hatching
10 days before hatching, thoroughly disinfect the hatching pond with quicklime. After the effect of the medicine disappears, fill with water to 30cm, tie the fish nest covered with eggs to a bamboo frame, and sink it below the water surface with stones. Use 20,000-30,000 eggs per square meter, and cover the top of the pond with canvas to avoid strong light exposure. At a water temperature of about 20°C, fry can hatch in 3-4 days. Newly hatched loach fry have a body length of 2.5-3.6cm and cannot move freely. They attach to the fish nest and pond walls with the adhesive organ on their heads. After 3 days they begin to swim, and the fish nest is taken out and feeding begins.
Cultivation of loach fry
Newly hatched loach fry cannot move freely and attach to the fish nest or other objects with their heads, using yolk as nutrition. Fry hatched in the pond are generally left in the original pond for cultivation, with the water depth kept at 20-30cm, and 500-1,500 fry per square meter is suitable. When the density is too high, some fry should be taken out and cultivated in another pond. Loach fry begin to feed 3 days after hatching. At this time, feed cooked and crushed egg yolk or fish meal suspension several times a day, with the feeding amount limited to what is eaten within 1 hour. After 2-3 days, switch to feeding water fleas, rotifers, mashed tubifex or silkworm pupae, etc. After about 10 days of cultivation, when the fry grow to 1cm, they can be transferred to a fingerling pond for rearing; if the density is low, they can remain in the pond for cultivation. After about 1 month, when the fry grow to around 3cm, they can then be transferred to a fingerling pond, or they can be directly put into rice fields, ponds or pits for adult fish rearing. Fingerling cultivation: The area of the fingerling pond should preferably be 30-50 square meters. Before stocking, the pond must be cleared and disinfected, and base fertilizer applied to cultivate food organisms. The stocking amount is about 30 grams per square meter (800-1,000 fish). Within half a month after the fingerlings are put into the pond, feed powdered compound feed twice a day, with the feeding amount at 3%-5% of the fingerling weight. In summer, always pay attention to changes in water quality and frequently replace with new water. When the fingerlings grow to about 10cm, they enter the adult fish rearing stage.
Precautions:
During hatching, to prevent deterioration of water quality and death of embryos from lack of oxygen during development, new water should be regularly added to the pond to keep the water fresh and the dissolved oxygen sufficient. At the same time, to prevent saprolegniasis on the eggs, regularly soak the fish nest covered with eggs in a 0.5ppm malachite green solution. After all the larvae emerge from the membrane, quickly remove the dead eggs to avoid deterioration of water quality caused by decaying eggs.
Satisfying the first feed of loach fry is the key to increasing their survival rate. Newly hatched loach fry absorb nutrition from the yolk. Within two months after the yolk disappears, they mainly feed on rotifers and water fleas in the water. It is best to cultivate rotifers, water fleas and other zooplankton in a dedicated pond to feed the loach fry. Manure and chemical fertilizers are both good fertilizers for raising loach. Fertilizer must be continuously added to the cultivation pond so that the loach fry and fingerlings have enough natural biological feed.
Loach has the habits of being a picky eater and foraging at night. If changing its special habits, artificial domestication must be carried out, feeding once every evening, increasing the amount of feed from small to large, and gradually advancing the feeding time until it can feed at around 10 a.m. and 5 p.m. and can eat artificial feed.