Trends in cyprinid polyculture

Billard R., Berni P.

Published date: June 2004
Volume: 28
Number: 3
Pagination: 255-261
Publisher: Société Française d’Ichtyologie

Polyculture is the association of fish species, mostly cyprinids, feeding at different levels of the aquatic pond ecosystem. It is an efficient food production system, which typically produces five tonnes of fish/ha/year without distribution of formulated artificial feeds but with intense organic fertilisation as well as grass and agricultural by-products. The exact figures of polyculture production in the world are not known precisely. A part of the production of cyprinids is due to monoculture of the grass carp and the common carp, both of which accepting artificial feeds. An estimate of the trends is given by the production of cyprinids specifically produced by the polyculture of Chinese carps in China (especially the silver carp and the bighead) and the major Indian carps on the Indian subcontinent. The total production of all carp species has increased over the last decade but the rate of increase has slowed down after 1997 in China for the silver carp and the bighead. In general, the commercial value of cyprinids is low, about $1 per kg. To compensate for this low price the fish farmers are looking for intensification of production and for species of higher commercial value. In polyculture systems the availability of natural food is the main limiting factor. It is not possible to increase the productivity above 10 t/fish/ ha/year, as adding more external poor quality feeds results in degradation of water quality and dysfunction of the ecosystem. A new form of polyculture in China is to intensify the production by feeding the fish with good quality manufactured feeds to avoid degradation of the water quality and to use silver carp and bighead to control the development of planktonic blooms. There is then a tendency towards replacement of polyculture by intensive monoculture of cyprinids and by new and more valuable species (tilapia, sturgeon, American and African catfish). If polyculture systems were converted to monoculture or less efficient polyculture (using new species) this would result in a decrease of the world production of fish in culture and of the global efficiency of aquaculture. In general, research programmes carried out to develop polyculture are more focused on the fish (genetics, artificial feeding, disease) in China and on pond productivity (artificial substrates, use of periphyton) in India. These technical improvements should increase the profitability of polyculture and assure its future as an efficient food production system.

Keywords: Carps - China - Cyprinidae - India - Polyculture
PDF available for everyone