Research of improved fish nutrition and fish health in upland aquaculture systems in Yen Chau, Son La Province, Vietnam

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Aquaculture importantly contributes to protein supply and cash income of Black Thai farmers in Yen Chau, Son La province, Northern Vietnam. The productivity of the current aquaculture system, the polyculture of the macroherbivorous grass carp together with 3-5 other (nonherbivorous) fish species and the use of green leaves, manure and crop residues as fish feeds, is limited mainly by two factors: A so far unknown disease of grass carp and the lack of a suitable feed base for the other species. The goals of this project are the development of the scientific base for adapted feeds for the non-herbivorous fish species and the diagnosis of the grass carp disease and possible prevention or cure. Currently, most ponds are operated as flow-through-systems, which is advantageous for the culture of grass carp, but limits the development of natural food for the other species and thereby also their production by continuous loss of nutrients and high turbidity. The combination of a modified water regime reducing flows in order to enhance primary production and a modified feeding regime using diets suitable for supplementation is expected to significantly improve the growth and production of common carp, tilapia and other species and increase the farmers’ income and revenue from aquaculture as well as home consumption of fish. The information currently available on grass carp disease does not match with any known viral, bacterial or parasitic disease of this species. Therefore, any strategies for prevention or treatment of this disease can only be developed on the basis of a solid diagnosis.