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Abstract:

The control of environment and growth rate of phytoplankton are important factors in the success of intensive shrimp farming. Study on composition and population density of algae in the monoculture and polyculture of black tiger shrimp (Penaeus monodon) with milkfish (Chanos chanos) was conducted in Tra Vinh Province  on four earthen ponds (2800-3000 m²). The results showed that there were 04 phyla was found in monoculture and polyculture of ponds. A number species and the percentage of Bacillariophyta was found 14 species (63.6%), Pyrrophyta 04 species (18.2%), Cyanobacteria 02 species (9.1%) and Chlorophyta was found 02 species (9.1%).The dominant algae in density was different between monoculture and polyculture ponds.In monoculture ponsthe Bacillariophyta (Chatoceros sp., Coscinodiscus sp.) and Cyanobacteria (Oscillatoria sp., Microcystis sp.) were dominant species, fluctuations density of Bacillariophyta 4,2 x 10³- 3.1 x 10⁵ ind/L, Cyanobacteria was the highest algae density 3,8 x 10⁶ ind/L. A number species of Bacillariophyta (Coscinodiscus sp.) and Chlorophyta(Oocystis sp.) were dominantin polyculture pons, fluctuations density of Bacillariophyta and Chlorophyta were 4,2 x 10³- 3.1 x 10⁵ ind/L, 1 x 10³ - 2.2 x 10⁶ ind/L respectively.In this study shows that in the polyculture ponds of black tiger shrimp with milkfish, will be stabilize the density algae, cyanobacteria limited in the pond, improves water quality and survival of shrimp.

Key word: black tiger shrimp, algae, milkfish, polyculture, water quality, phytoplankton