Since the technologies for artificial breeding and large-scale production of fish seed, especially for freshwater Asian carps, were discovered some 3 - 4 decades ago in China and India, progress in fish culture has been dramatic. Development of polyculture and integrated culture systems in China and composite carp culture in Indian sub-continent made carp culture a highly profitable venture. Other countries in the region such as Thailand, Indonesia, Philippines, Nepal, Vietnam, etc. have followed suits and have achieved very successful results in culturing many indigenous and exotic species. Rapid expansion of small-scale, semi-intensive polyculture/integrated culture of carps were made possible by successful public sector interventions through the production and supply of fish seed and other basic inputs needed by the producers and the transfer of appropriate culture technologies through effective extension services.
Looking back at the evolution of freshwater carp culture in Asia, one cannot fail to acknowledge the tremendous contributions made by the dedicated extension services in the countries where aquaculture has established itself as a viable and important economic activity, making substantial contribution to household food security, employment and income. Like agriculture, each aquacultural country in the region has developed its own aquaculture extension services delivery system with its own methods and approaches. In this publication, an extension method called Trickle-Down-System (TDS) of extension, which was applied through FAO field projects in Bangladesh and Vietnam with great success has been reviewed. In the project areas in both countries, unit production (kg/ha/yr) had increased by over 200%. This dramatic increase in production was attributed to the effective extension services provided by the projects through the implementation of the Trickle-Down-System of aquaculture extension. The amount of increase in production has been called “Extension-Gap” which the author believes can be bridged through the implementation of appropriate extension services in many countries.
