- Name of species:
This group includes common carp (Cyprinus carpio), Chinese carps (silver carp, bighead and grass carp, mud carp, etc.), Indian carps (rohu, catla and mrigal, etc.), barbels (such as Thai silver barb) and some other species of cyprinids. The carp species for aquaculture are generally low in the food chain in an aquatic ecosystem. Being low in the food chain is desirable in the sense that they can be grown with less costly feeds, while in the case of silver carp and bighead they can be grown by fertilising the water to proliferate the plankton as their food. · By mode of feeding, there are foraging carps (common carp and grass carp, etc.) and filter feeders (silver carp and bighead). Foraging carps may be herbivorous (grass carp) or omnivorous (common carp). Foraging carps readily accept artificial pellet feeds in culture conditions. · Among filter feeders, silver carp feed mainly on phytoplankton and bighead mainly on zooplankton. In water bodies with high organic matter content, such as fish ponds, organic particles colonised with bacteria may contribute up to one-third of the growth of the filter feeders in addition to planktons.
- Primary potential:
The primary potential is for low input, low cost aquaculture production of protein food for domestic consumption and cash income. It is possible to integrate carp culture with crop farming and/or animal husbandry, as widely practised in some Asian countries, leading to reduced production cost, efficient use of land and water and less disposal/discharge of waste materials into the environmental. Filter feeding silver carp and bighead stocked or cultured in cages in reservoirs that supply water for domestic or urban use help the removal of nutrients from water, resulting in better water quality. In reservoirs that supply water for domestic or urban use but with high nutrient content or algal bloom problems, stocking or culture in cages of filter feeding silver carp and bighead helps the removal of nutrients from water and hence resulting in better water quality. Minor benefit is the production of some food fish without feed input.
- Attributes for aquaculture/stock enhancement :
· Carp farming for consumption dates back to more than 2,000 years ago in China. Nowadays, carp culture is widely practised in East Asia, Southeast Asia, South Asia, Israel, Central Asia and some Eastern European countries.
· The world carp production from aquaculture in 1999 was 14.9 million tonnes, which was 44.7% of the world total aquaculture production in the same year. Top ten single species fin-fish production from aquaculture are all carps except tilapia and Atlantic salmon
· Though in many industrialised countries, like Australia, carps are regarded as pests, they are the strategic species for securing rural livelihood and national food security through freshwater aquaculture for food fish production in many populous counties in Asia.
· Hatchery technology for carp species found in South Asia and Southeast Asia and the common carp are relatively simple and have been well established. Apart from mass scale hatchery operation, these species are also suitable for small-scale hatchery operators.
· Chinese carps do not spawn naturally in captivity and require hormonal treatment. Hatchery technology for seed production of Chinese carps is well developed and established. Chinese carps are more suitable for mass-scale hatchery operation because of their reproductive characteristics, i.e. relatively larger maturation size and age
· Nurseries for carps are mostly earthen pond-based and preparing the natural food organisms (zooplanktons) through balanced fertilisation and proper water management requires some skills. Supplementary feeds are used. Carp nursery techniques are well established in Asian countries like China and India
· Carp are less demanding of animal protein for food. For grow-out, compound feeds with mainly plant ingredients with 30-40% crude protein are commonly used. A commercial carp-feed industry that supplies both ordinary hard pellets and floating pellets is well established in major carp-producing countries
· Diseases are not a major problem in extensive to semi-intensive culture systems. Additional input is required for disease control in intensive farming· Grow-out period is 6 months to 1 year in tropical conditions. In cold water, it takes 1-2 years
- Culture methods :
Most carp farming are pond-based with several species stocked in the same pond (polyculture). Tilapia and sometime catfish are stocked together with carp. Single-species culture, or monoculture, is rare, except in flow-through system and cage culture of common carp in streams or canals
· There are different stocking models for polyculture, depending on the availability of the main source of feed. If grasses (aquatic or terrestrial) are abundant, grass carp can be stocked as the major species. The leftover feed and grass carp excreta would sufficiently fertilise the pond water for the growth of filter feeders
· Pond-based carp culture has been traditionally integrated with crop-farming (mulberry, fruit, vegetables, etc.) and animal husbandry (ducks, swine, chicken, etc.) in China. The practice has been widely introduced to many other parts of the world with some modifications to fit into local conditions. (The NACA Secretariat and the Freshwater Fisheries Research Centre in Wuxi, China offers a 3-month training course on Integrated Fish Farming each year for overseas trainees with fund to cover all expenses in China. South Pacific countries could participate for the cost of the airfare.)
- There is a varying degree of intensity of pond carp culture from extensive to intensive:
- Extensive: low stocking; more fertiliser than feeding; more filter feeders than foraging species. (Organic fertilisation alone could support fish weight gain of 15kg/ha/day with filter feeders and common carp.)
- Intensive: high stocking density, more commercial feeds than fertilisation or even no fertilisation; foraging species as main species while filter feeders are minor species for cleaning water. (Aeration is required if the targeted production exceeds 10 ton/ha/year.)
- Current production status :
· Small-scale farms operates in ponds of 0.1 to 0.5 ha in size. Large commercial farms operate in ponds of about 1 to 2 ha in size. Deep ponds (2-3 metres) are desirable
· Net cage and pen culture of carp in freshwater lakes, reservoirs, rivers and canals have been well established in some Asian countries. Supplementary feeds or commercial feeds are often used. This requires reliable supply of reasonably large fingerlings from pond-based nursery farms
· Carp culture in paddy field (for nursing or for grow-out) is successful in many Asian countries without use of pesticides. Paddy fields need modification with a deep ditch for fish as shelter. (In China 2.5 million ha of paddy field was utilised for grow-out of fish, mostly carps, and 0.25 million ha for fingerling culture in 2000. National average yield of food fish from paddy fields was 487 kg/ha/year.)
· Carp fingerlings are released into inland open waters for fishery resource enhancement in many Asian countries
- Marketing :
· Almost the entire production of carps are for the domestic markets for local consumption among major producers
· Carp are marketed in live, fresh, chilled and frozen forms, depending on the location, season and local consumer preference. Consumers only buy dead fish in some Buddhist countries in Asia, while live carps are preferred in China and among Chinese communities in Southeast Asia
· In countries where carp consumption is new, it may take some time to educate or train the people on how to eat carps that have a lot of inter-muscular bones. Proper cooking, such as deep frying and fish meat balls, can overcome this. Carp are well suited to Chinese and Indian cuisine
· The head of bighead carp (one-third of the body weight is in the head) is often sold separately in China, and fetches higher prices because it is meaty and good for soup. In the Philippines, on the other hand, the head is removed and the body is sold at a higher price
- Comparative advantages/disadvantages (risks) of producing the species in the Pacific:
· Some carp species have been introduced to South Pacific countries with some degree of acceptance by local farmers and consumers.
· Carp could be integrated with other farm activities in Pacific countries to reduce overall production costs and bring greater economic and environmental benefits.
· Some large Pacific countries with extensive river systems have poor freshwater fish fauna, or only small species, and careful introduction of some carp species could enhance the supply of edible freshwater fish (but see also under Disadvantages below).
· Filter feeding carps, silver carp and bighead are suitable species for low-cost aquaculture production and for culture-based inland fishery resource enhancement. Grass carp, as a voracious feeder, could be introduced to utilise both aquatic and terrestrial grasses.
· In many Pacific countries there are no major rivers. Even if Chinese carps, which require strong turbulences in the spawning ground, spawn naturally in the rivers, the eggs will be flushed into the sea before well they are developed. Hence, the threat to local fish species is considered to be minor.
Carp species might pose a threat to indigenous fish when introduced, primarily through habitat modification/degradation.