Due to the natural features of bighead carp, the systems used for its culture are rather limited. Extensive culture in open-waters and pond-based polyculture are the major systems used. The most important factor involved in the production of bighead is to ensure a sufficient supply of quality seed. Comparatively, it is more difficult to breed bighead than other fish, due to their slow gonadal development. It is also more difficult to produce large-size fingerlings, due to their slow growth in the early developmental stage.
Seed supply
Artificial propagation is the major supply of seed for the culture of bighead carp, although natural seeds are still available in some Chinese rivers. Seed collected from natural waters is mainly used for maintaining the quality of broodstock. The broodstock used for artificial propagation is usually raised in captivity with seed from the wild or from breeding stations, where good natural stock are maintained.
Hatchery production
Induced breeding is applied for bighead. Well-matured breeders are released into a spawning tank (round cement tank 6-10 m diameter; water depth ~ 2 m) after being injected with inducing hormone (normally HCG and PG). Water circulation is maintained throughout the spawning period.
The eggs are transferred to a hatching raceway or hatching jar, either manually or by gravity. Hatching raceways, which are round or ellipse-shaped cement structures, are commonly used for large scale production. Their width is normally 0.8 m and their depth 0.8-1.0 m. The inlets are mounted on the bottom of each raceway, and open in the same direction and at an angle of around 15° to the bottom surface. Screens are mounted on the inner wall for the regular discharge of water. Eventually, water can be totally drained through the outlet on the bottom. A current is maintained during the hatching period to keep the eggs and larvae suspended in the water column.
Nursery
Earthen ponds are used for the nursing of bighead carp. Ponds are usually 0.1-0.2 ha in area and 1.5-2.0 m deep. Ponds are chemically cleared, normally with quicklime, to eliminate all harmful organisms after totally drying. The usual dose is 900-1125 kg/ha.
Organic fertilizer - animal manure and/or plant wastes ('green manure') is commonly applied to increase the natural biomass of zooplankton 5-10 days before the stocking, according to the water temperature. The quantity of organic fertilizer used is usually 3000 kg/ha for animal manure or 4500 kg/ha for green manure. Green and animal manures can be used simultaneously but the quantity of each should be reduced accordingly.
Monoculture is practiced in the nursery stage, with a stocking density normally ranging between 1.2-1.8 million/ha, depending on the length of rearing and targeted size. The nursery operation usually takes 2-3 weeks in China. Organic fertilization is carried out at frequencies and rates sufficient to maintain high pond fertility and therefore a good supply of natural food organisms (especially zooplankton) for the fish. The quantity ranges from 1500-3000 kg/ha once every 4-5 days for animal manure or green manure, depending on existing water fertility. Soybean milk can also be used as both direct feed and fertilizer to replace organic fertilizer in the nursery stage. The normal quantity is 3-5 kg (dry soybean)/100 000 fish daily. This usually means production costs are high. Using a paste-form of soybean cake or other by-products from grain processing may be needed if poor growth of fish is observed in the later part of the rearing period. The quantity is usually 1.5-2.5 kg/100 000 fish daily. Normal survival rates in nursery ponds are 70-80 percent, although it may reach over 90 percent under good management.
The fish usually reach the size of about 30 mm in length after 2-3 weeks of rearing. These are called summer-fingerlings in China and are ready for the fingerling rearing stage. Conditioning, through careful netting and holding the fish at high density for a while (several hours) is required before the transfer of summer-fingerlings to the fingerling pond. This practice is designed to increase fish tolerance to stress before they are transported.
Rearing fingerlings
Summer-fingerlings are not suitable for direct stocking in grow-out ponds; they need to be reared to the fingerling stage (13-15 cm in length) first. The technique for fingerling rearing is rather similar to the nursery operation, including the feeding and fertilization regime. The major differences include the following:
- Relatively larger (0.2-0.3 ha) and deeper earthen ponds are used for fingerling rearing.
- Contrary to the nursery stage, polyculture is commonly adopted for the production of bighead carp fingerlings. Bighead carp can be polycultured with other carp species but not silver carp. Monoculture is rarely practiced in production of bighead carp fingerling.
- The stocking density is around 120 000/ha when it is the major species in the pond or 30 000-60 000/ha when it is the secondary species.
- Fingerling rearing normally takes 4-6 months for above mentioned size and stocking density in China. The period can be considerably shortened in warmer climates or if lower stocking densities are used.
- The normal survival rate through the whole fingerling rearing period should be above 95 percent.
In Viet Nam, the rearing of bighead carp before the grow-out stage is divided into two periods. Fry are first raised to 2.5-3 cm, with a stocking density in the nursery pond that is slightly higher than grass carp (c/f grass carp fact sheet). Then the fish are further raised to the size of 6-12 cm at a much lower density. Here, the rearing of bighead carp seed usually takes 45-50 days. The fish is usually fed with soybean powder, maize powder and rice bran.
Ongrowing techniques
The most commonly adopted techniques for ongrowing (grow-out) bighead carp are polyculture in pond and pens and extensive culture in lakes and reservoirs.
Polyculture in ponds and pens
In China, bighead carps are usually cultured as secondary species together with other carp species. The grow-out stocking density is 750-1500/ha of 13-15 cm fingerlings. If selective harvesting is to be practiced, a certain proportion of larger sized fish (up to 250 g) is also stocked. There is no special feeding/fertilization required for bighead when herbivorous and omnivorous fish are cultured as the main species. However, organic fertilizer is usually applied to raise natural food if bighead and silver carp are cultured as major species. The fish can reach marketable size (750-1500 g) within 8-10 months in China. The culture period may be much shorter in tropical and subtropical areas. The yield of bighead carp is usually 500-1000 kg/ha, which accounts for 10-15 percent of the total production.
In Viet Nam, bighead grow-out is conducted through polyculture with other species, such as grass carp, silver carp, rohu, mrigala, common carp and tilapia. Bighead carp is stocked as a minor species in the ponds, usually accounting for 3-5 percent of the total. However, bighead carp usually account for 5-7 percent of the total production. No special feeding for bighead carp is practised. The market size of bighead carp is 2.5-3 kg.
Extensive culture in small lakes and reservoirs
In this system, bighead carp are usually stocked as the major species, with a stocking density of 150-750/ha, depending on the size and fertility of the water body. This level represents about 40-50 percent of the total number of fish stocked. The stocking size is usually 13-15 cm. A small percentage of large fingerlings (up to 250 g) is also stocked for selective harvesting to fully utilize the water and the available natural food. Neither feed nor fertilizer is used in this form of rearing. The production of bighead can reach 150-400 kg/ha, which accounts for 40-60 percent of total production.
Harvesting techniques
Selective harvests are taken in the later part of the culture period and are normally conducted in the early morning (when temperatures are relatively low, and for morning marketing). Individuals of marketable size are selected after netting (one netting per harvest). Several partial harvests are usually carried out before total draining of the pond for the final harvest. At this final harvest the fish are either marketed or used for restocking (individuals below marketable size) for the next production cycle.
Handling and processing
Bighead are usually consumed fresh, with the exception of some reservoir fisheries, where it is difficult to market them all fresh due to their remote location. Some of the production is canned.
Production costs
Being produced through natural food, there is no supplementary feed input for grow-out. The major inputs are seed and management, and sometimes fertilizers. Thus total rearing costs are very low. The seed cost usually comprises more than 50 percent of the total production cost, which is normally less than USD 0.20/kg.
The major diseases of bighead carp and the methods of control are listed in the table below.
In some cases antibiotics and other pharmaceuticals have been used in treatment but their inclusion in this table does not imply an FAO recommendation.
Bacterial Septicemia |
Aeromonas sobria; Aeromonas hydrophila; Yersinia ruckerri; Vibrio sp. |
Bacteria |
Hyperaemia at different positions of body, such as jaws, mouth cavity, operculum, fin-base and whole body when serious; protruded eyeball; swollen anus; expanded belly; erected scales; gill rotten and reduced feeding; high mortality of infected fish |
Disinfecting the fish and culture environment with quicklime and potassium permanganate; 'Yu Tai III' (commercial drug of multi herb ingredients) through medicated feed |
Stigmatosis |
Aeromonas punctata sub. punctata |
Bacterium |
Round red spot on skin and muscle near anus of fish; loose scale; rotten skin and muscle even reaching the bone; physically weak and slow movement; much reduced feeding; die of exhaustion |
Spraying of bleaching powder or furazolidone solution in pond; dipping infected fish in potassium permanganate or furazolidone solution; antibiotics |
White head-mouth disease |
Myxococcus sp. |
Bacteria |
Whitish colour in mouth and front part of head; swollen lips; difficulty in breathing because of losing control in mouth movement; ulceration of skin around the month |
Dipping the fish in 2-2.5% saline water or 1% rhubarb Rheum officinale solution before stocking; spraying of rhubarb Rheum officinale solution over the pond at a concentration of 2.5-3.7 ppm or a solution of furazolidone at a concentration of 0.1-0.2 ppm |
Myxosporidiasis |
Myxobolus drigini |
Protozoan |
Spore of parasite visible on body or inside body; swimming frantically; may finally die of exhaustion |
Clearing pond with quicklime or nitrolime (CaN2) before stocking; dipping the fish in the solution of dipterex and spraying the solution over the pond; difficult to treat due to very resistant cover of the parasite |
Trichodiniasis |
Trichodina sp. |
Protozoan |
Dark body colour; obvious macilency (loss of weight); slow in movement; high mortality of juvenile fish |
Clearing pond with quicklime and dipping fish in 0.3% saline water or 0.5 ppm dipterex solution before stocking; spraying dipterex solution over the pond at concentration of 0.2 ppm |
Lernaeosis (anchor worm) |
Lernaea sp. |
Copepod |
Parasitizes into the muscles; swims abnormally; feeds little and gradually dies |
Thorough clearing of pond with quicklime before stocking; spraying solution of 90% dipterex in pond at the concentration of 0.3-0.5 ppm; dipping the infected fish in potassium permanganate solution at 10-20 ppm for 1-2 hours |
Saprolegniasis: Dermatomycosis (Water-mould disease) |
Saprolegnia spp.; Achlya spp. |
Fungus |
Whitish fungus mycelia visible on the body; cotton-like; weakened body or even die of exhaustion |
Careful handling of fish and disinfection of pond with quicklime; immersing infected fish in potassium chloride solution or malachite green solution |
Suppliers of pathology expertise
The following can provide expertise in this topic:
- Research Institute of Hydrobiology, CAS, Wuhan City, Hubei Province, China.
- Shanghai Fisheries University, Shanghai, China.
- Pearl River Fisheries Research Institute, CAFS, Guangzhou City, China.
- Freshwater Fisheries Research Centre, CAFS, Wuxi, Jiangsu Province, China.
- Zhejiang Provincial Freshwater Fisheries Research Institute, Huzhou City, Zhejiang Province, China.