Detailed Explanation of Key Points for Loach Farming Techniques in Taiwan, China
Taxonomically, the Taiwan loach belongs to the order Cypriniformes, suborder Cyprinoidei, family Cobitidae, and genus Misgurnus; it is an omnivorous small freshwater fish commonly found in rivers, ditches, paddy fields, ponds, lakes and reservoirs throughout our country except the Qinghai-Tibet Plateau. To increase effective supply, developing large-scale farming of the Taiwan loach is particularly important. Here is a brief introduction to the artificial breeding and large-scale pond farming techniques for the Taiwan loach.
Artificial Breeding of the Taiwan Loach
1. Selection of Parent Loaches and Identification of Male and Female Parent loaches used for artificial breeding generally should not be kept for long periods; it is best to collect natural Taiwan loaches near the spawning season and use them for artificial breeding after intensive conditioning. When collecting parent loaches, mature Taiwan loaches must be selected that are over 2 years old, well-shaped, robust, with plenty of mucus, healthy and uninjured. Female loaches should be at least 18 cm in body length and 30 g in weight, with a distended, soft and elastic abdomen; male loaches should be at least 12 cm in body length and 15 g in weight, with obvious nuptial tubercles on the pectoral fins. When distinguishing males from females, mature female loaches are noticeably larger than males; the female's pectoral fins are broad and short, with blunt rounded tips, fan-shaped, the abdomen is noticeably protruding, the body is cylindrical, and the genital pore is everted and red; the male is smaller in build, with narrow and long pectoral fins whose tips are pointed and upturned, a bony lamella at the base of the second fin ray, and nuptial tubercles on the fin rays.
2. Artificial Induced Spawning Before induced spawning, commonly used equipment must be fully prepared, including: 2 mortars 6 cm in diameter, for grinding pituitary glands and testes; several medical syringes with a capacity of 1 mL to 2 mL, and several No. 4 injection needles, for injecting the spawning inducer into parent loaches; 2 each of dissecting scissors, knives and tweezers, for removing testes; several basins or buckets, for temporary holding of parent loaches before spawning; several towels, several hard feathers from poultry wings, 1 narrow-mouth bottle of 1000 mL, 2 pipettes of 20 mL or 50 mL, and several white enamel bowls. The artificial induced spawning time for the Taiwan loach should be somewhat later than natural spawning, requiring water temperature to remain stable above 20°C. The inducing drugs are generally human chorionic gonadotropin (HCG), pituitary gland, and luteinizing hormone-releasing hormone analogue (LRH-A); each female loach is injected with about 300 international units to 400 international units of HCG, or 1 carp pituitary, or about 5 μg to 10 μg of LRH-A, with the dose for male loaches halved; the injection site is intramuscular injection in the back, though coelomic injection may also be used; the injection dose for female loaches is 0.2 mL, and for male loaches 0.1 mL, with an injection depth of 2 mm; the injection time should be set so that the Taiwan loaches reach peak estrus in the early hours of the next day. After injection, the parent loaches are placed in cages measuring 2 m × 1 m × 0.5 m, with 50 groups of parent loaches per cage, at a female-to-male ratio of 1:1.2 to 1.5, and several fish nests are placed inside the cage at the same time.
3. Artificial Insemination When approaching the effective time, if the parent loaches are seen chasing more and more frequently, with male loaches curling their bodies around the females and the females breathing rapidly, this indicates that peak estrus has arrived; at this point, squeezing the female's abdomen produces golden-yellow eggs that flow out freely, indicating that artificial insemination can proceed. Artificial insemination should preferably be carried out indoors: one person wraps the mature female loach in a towel, exposing the belly, and gently squeezes the abdomen to squeeze the mature eggs into a dry white enamel dish; another person pours the prepared semen over the eggs; a third person gently shakes the dish by hand and stirs gently with a feather for several seconds, then adds a small amount of clean water to enhance sperm vitality and increase the fertilization rate, after which the fertilized eggs are rinsed several times and placed in an incubation jar to hatch.
4. Incubation A single incubation jar should contain relatively concentrated fertilized eggs obtained at the same time. The incubation water must be fresh, free of pollution, with a dissolved oxygen content of 6 mg/L to 7 mg/L and a pH between 7 and 8, with 2 to 3 fertilized eggs per 1 mL of water. The water flow in the incubation jar should be controlled so that the fertilized eggs are lifted to the middle of the water surface, gradually disperse to the sides as they approach the surface, and then gradually sink. The suitable water temperature for incubation is 20°C to 28°C, with the optimum at 25°C; at a water temperature of 24°C to 25°C, larvae can hatch in about 30 to 35 hours. Newly hatched larvae should continue to be held in the original jar under gentle water flow; after most larvae have basically absorbed their yolk sacs, cooked egg yolk is fed into the incubation jar, with 1 egg yolk per 200,000 larvae, fed continuously for 2 to 3 days, after which they can be transferred to ponds for fry-stage rearing.
Large-Scale Pond Farming
So-called large-scale farming refers to carrying out Taiwan loach farming production in concentrated, contiguous areas at the same site (one hundred mu, several hundred mu, or even over a thousand mu), requiring an average yield of over 500 kg/mu, and integrating fry rearing, commercial loach production, feed supply and centralized sales of commercial fish into a "one-stop" production system, providing the market with large quantities of ample commercial Taiwan loaches.
1. Site Selection The site selection for a Taiwan loach farm should, as far as possible, achieve an adequate and reliable water source, fresh and pollution-free water quality, convenient pond water intake and drainage (capable of self-irrigation and self-drainage), neutral or slightly acidic clay soil, abundant sunlight, convenient transportation, and guaranteed electricity.
2. Construction of Adult Loach Ponds The pond area is 100 sq m to 300 sq m; during construction, full consideration must be given to the Taiwan loach's distinctive habits of burrowing into mud and escaping. The pond perimeter must be 40 cm above the water surface, and can be built with cement boards, bricks, hard plastic boards, or compacted lime-sand mixture, or surrounded with screen mesh along the pond perimeter, with the lower end of the screen mesh buried in hard soil and the upper end 15 cm to 20 cm above the water surface; the pond depth is 80 cm to 100 cm, with bottom silt 20 cm to 30 cm thick, and the water depth maintained at 30 cm to 50 cm; the pond inlet is 20 cm above the water surface, the drainage outlet is set at the normal water level of the pond, and the bottom drainage opening is set at the bottom of the fish collection pit at the pond bottom, with both the inlet and drainage outlet wrapped in fine mesh cloth to prevent the Taiwan loach from escaping. To facilitate harvesting, a fish collection pit connected to the bottom drainage opening should be provided in the pond, with an area of about 5% of the total pond bottom area and 30 cm to 35 cm deeper than the pond bottom; the fish collection pit is enclosed with wooden boards or built with cement and bricks.
3. Preparation Before Stocking Ten days before stocking loach fingerlings, clean and level the loach pond, plug leaks, clear the intake and drainage pipes, plow the bottom silt, and then disinfect the pond with quicklime, that is, apply 100 g/sq m of quicklime at a water depth of 10 cm, and after slaking the quicklime in water to form a slurry, immediately splash it evenly over the whole pond. Three days after pond disinfection, add water to the pond to 30 cm, and apply base fertilizer; the base fertilizer can be 300 g/sq m of fermented chicken manure, or 500 g/sq m of fermented human manure, pig manure, cow manure, etc., to cultivate plankton in the pond water so that the loach fingerlings can feed on suitable basic food organisms right after being stocked.
4. Stocking of Loach Fingerlings Before stocking, disinfect loach fingerlings with an 8 ppm to 10 ppm bleaching powder solution, soaking for 20 to 30 minutes at a water temperature of 10°C to 15°C. For fingerlings 3 cm to 4 cm in body length, the stocking density is 50 to 60 fish/sq m; when water source conditions and technical expertise are good, the stocking quantity can be appropriately increased. In Taiwan loach farming ponds, some fish that live in the upper and middle water layers, such as summer fry of grass carp, silver carp and bighead carp, may also be appropriately stocked in combination, but species such as tilapia, common carp and crucian carp should not be stocked in combination.
5. Fertilization The Taiwan loach is an omnivorous fish that likes to eat organic debris, plankton and benthic animals; therefore, during the adult loach farming stage, fertilization measures should be taken to cultivate basic food organisms in the pond water. In addition to applying base fertilizer, additional fertilizer should be applied in a timely manner according to water color; the additional fertilizer is commonly fermented farmyard manure such as pig manure, cow manure, chicken manure and human manure, and chemical fertilizers such as superphosphate, urea and ammonium bicarbonate may also be applied; the amount of additional fertilizer depends on the water color, at 30% to 50% of the base fertilizer, controlling the pond water transparency at 15 cm to 20 cm, with a yellow-green water color being preferable.
6. Feeding The Taiwan loach has a broad diet; in farming, in addition to fertilizing the water, compound feed should also be provided. The appetite of the Taiwan loach is related to water temperature: when the water temperature is below 20°C, it mainly feeds on plant-based feed, accounting for about 60% to 70%; when the water temperature is 21°C to 23°C, the proportions of animal and plant feed are each 50%; when the water temperature exceeds 24°C, the proportion of plant-based feed should be reduced to 30% to 40%. Animal-based feeds for the Taiwan loach include fish meal, animal offal, earthworms, small trash fish and blood meal, while plant-based feeds include soybean meal, rapeseed meal, wheat middlings, wheat bran and grains; artificial compound feed may also be given, fed twice a day, with a daily feeding amount of 4% to 10% of the total body weight of the Taiwan loaches, and the feeding amount should be flexibly controlled according to water quality, weather and the feeding situation of the Taiwan loaches. When the water temperature is above 15°C, the appetite of the Taiwan loach gradually increases, and at 25°C to 27°C its appetite is especially strong; when the water temperature exceeds 30°C or falls below 12°C, feeding should be reduced or even stopped. Feed should be given according to the requirements of "fixed time, fixed location, fixed quality and fixed quantity."
7. Daily Management Take care to keep the pond water fertile, lively, tender and refreshing, with a yellow-green water color being best, and change the water 1 to 2 times a week; insist on patrolling the pond 3 times a day, paying attention to changes in the pond water color and the activity of the Taiwan loaches; regularly feed medicated bait to prevent fish diseases; frequently clean the feeding platform and disinfect it regularly; when diseases are found, treat them promptly; frequently inspect the water inlet, drainage outlet and pond embankments, and repair any leaks promptly; when the climate and environment change abruptly, such as in muggy weather, low air pressure, thunderstorms or continuous rainy days, watch whether the adult loaches surface for air, and if surfacing is severe, promptly add fresh water; keep good farming records.
Prevention and Treatment of Common Diseases
1. Saprolegniasis Caused by infection with fungi such as Saprolegnia and Pythium, mostly due to injury to the loach body leading to fungal spores reproducing at the wound and invading body tissues; white or grayish-white cotton-like growth can be seen with the naked eye at the affected site. The prevention and treatment method is to splash the whole pond with a mixed solution made from 400 ppm baking soda and table salt.
2. Red fin disease Caused by Brevibacterium infection; the diseased loach has congestion and ulceration at the fins, abdomen, skin and around the anus, and the caudal and pectoral fins turn white and rot. The prevention and treatment method is to splash the whole pond with 1 ppm bleaching powder.
3. Print disease Caused by parasitism by Aeromonas, the lesions on the diseased loach are swollen and red, oval or round in shape, mainly concentrated on both sides of the caudal peduncle, resembling a stamped seal. The prevention and treatment method is to splash the whole pond with 0.5 ppm dibromohydantoin.
4. Parasitic diseases Mainly caused by parasitism by Trichodina, Epistylis and Gyrodactylus, etc.; the diseased loach is thin and weak, often floating at the water surface, restless, or spinning at the surface, with increased mucus on the body surface. The prevention and treatment method is to splash the whole pond with 0.7 ppm of a copper sulfate and ferrous sulfate mixture (5:2) to prevent and treat trichodiniasis and epistylidiasis, and to splash the whole pond with 0.5 ppm of 90% crystallized trichlorfon to prevent and treat gyrodactylosis.
Harvesting, Temporary Holding and Transportation of the Taiwan Loach
1. Harvesting Stretch a net outside the bottom drainage outlet of the pond; as the water flows out from the drainage outlet, the Taiwan loaches gradually gather in the fish collection pit, and some flow with the water into the stretched net; then flush the fish collection pit with water so that the Taiwan loaches concentrate in the stretched net.
2. Temporary Holding After the Taiwan loaches are caught, whether for domestic sale or external shipment, they must be placed for several days in fish baskets, cages, water vats or cement ponds with clean water (without feeding) for temporary holding. The purposes are: to expel feces from the fish body and increase transportation survival rate; to remove the muddy odor from the flesh of the Taiwan loach and improve the eating taste; and to gather the Taiwan loaches in one place for convenient batch shipping.
3. Transportation Adult loaches have a strong skin respiratory function and are relatively convenient to transport. For short-distance transport, dry transport can be used, that is, putting the Taiwan loaches in a container and keeping the skin moist for short-distance transport; for medium-distance transport, wooden barrels or fish transport baskets can be used. Generally, 1 kg of water can transport 1 kg to 1.5 kg of Taiwan loaches, and at an air temperature of 15°C, transport time can last 5 to 8 hours; for long-distance transport, cooling measures should be adopted, that is, placing fresh live Taiwan loaches in a refrigerated truck at about 5°C for temperature-controlled transport.
Pond Management Techniques for Farming the Taiwan Loach
1. Pond construction: The pond should be close to a water source, with an area of 200-400 sq m and a water depth of 0.7-1 m; the pond walls should be built of brick and stone, or compacted with lime-sand mixture, and the pond bottom tamped solid; it should be sturdy, durable and leak-free; the inlet and outlet should be blocked with iron wire or plastic mesh; the pond bottom should slope toward the drainage outlet to facilitate drainage and harvesting. Leave 10 cm of water, and use 50 kg of quicklime plus 15 kg of bleaching powder per mu for pond clearing and disinfection.
2. Loach fingerling stocking: It is best to choose the Taiwan loach (also known as the true Taiwan loach) or the large-scale loach (Paramisgurnus dabryanus) for farming. Seven days after pond clearing and disinfection, fill with water to a depth of 20-30 cm. Apply sufficient base fertilizer on the sunny side of the pond, and deepen the pond water to 40-50 cm. Three days later, stock loach fingerlings, with 100-150 fingerlings of 3-5 cm body length per sq m of water surface, or 60-70 fingerlings of over 6 cm body length.
3. Feed feeding: Set up feeding platforms for fixed-point feeding, generally once in the morning and once in the afternoon each day, with a daily feeding amount of 5-10% of the body weight of the Taiwan loaches in the pond. The specific feeding amount should be flexibly controlled according to water quality, weather and the feeding situation of the Taiwan loaches. Feeding may be omitted when the water temperature is too high or on thunderstorm days.
4. Water quality regulation: Fertilize reasonably according to the fertility of the pond water, controlling pond water transparency at 15-20 cm, with a yellow-green water color being best. When the water temperature exceeds 30°C, the Taiwan loach will burrow into the mud to escape the heat, which can easily cause death from hypoxia and suffocation; at this time, frequently add fresh water to regulate water temperature and increase the dissolved oxygen content of the water body, and also take shading measures, using aquatic plants such as water hyacinth and duckweed for shade. When the Taiwan loaches swim to the water surface to surface and "gulp air," it indicates oxygen deficiency in the water; fertilization should be stopped and fresh water added promptly. In winter, deepen the water level to raise the water temperature and ensure the Taiwan loaches overwinter safely.
5. Disease and pest prevention: Disinfect frequently and do a good job of the "three disinfections," namely disinfection of the loach body, disinfection of the pond, and disinfection of the feeding platforms. When dead or diseased Taiwan loaches are found, remove them immediately to prevent infecting other Taiwan loaches, and treat them promptly. Clear weeds around the pond, keep the farming environment hygienic, strictly prevent frogs from entering, catch frogs promptly when found, and remove frog eggs; block the water inlet with screen mesh to prevent wild trash fish from entering the pond with the water; drive away birds promptly when found.
I think everyone is very familiar with loaches, but there are many kinds of loaches, and perhaps many people are not particularly familiar with the Taiwan loach. In fact, no matter which variety of loach it is, as long as you understand its living habits, it is very helpful for farming it.