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Biological characteristics of the improved extensive shrimp system in the Mekong delta of Vietnam
Author(s) -
Tho Nguyen,
Merckx Roel,
Ut Vu Ngoc
Publication year - 2012
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.2011.02858.x
Subject(s) - shrimp , biology , cyanobacteria , fishery , oscillatoria , phytoplankton , shrimp farming , mekong delta , zooplankton , ecology , aquaculture , fish <actinopterygii> , bacteria , nutrient , environmental science , genetics , water resource management
Low and unstable shrimp yields of the improved extensive shrimp system has been a tremendous obstacle for economic development in the coastal areas of Southern Vietnam. To investigate the biological characteristics of this system, ponds in the coastal Cai Nuoc district, Mekong delta of Vietnam, were monitored. Results showed that the system was not optimal for shrimp. While chlorophyll a (chl a ) (1.51–37.2 μg L −1 ), phytoplankton density (6333–974 444 cells L −1 ) and zooplankton density (7.1–517.2 ind L −1 ) were abundant and comparable to shrimp farms elsewhere, zoobenthic community was very poor (7–1971 ind m −2 ). Toxin‐producing cyanobacteria ( Oscillatoria limosa , Oscillatoria formosa , Anabaena sp. and Phormidium tenue ) were found. Total bacteria and Vibrios were present in large numbers (respectively 1.04 × 10 5 and 6.64 × 10 2 CFU mL −1 in pond water, 6.33 × 10 5 and 9.47 × 10 3 CFU g −1 in sediment). Presence of toxin‐producing organisms, poor zoobenthic community and abundance of Vibrios all can enhance shrimp susceptibility to diseases. The following measures are recommended to improve the situation: (1) complete testing of seeds for pathogens, (2) not to incorporate fish into shrimp ponds and (3) applying no‐culture breaks and pathogen‐killing chemicals.