According to the assessment, the central coastal provinces have many advantages to develop aquaculture, especially brackish shrimp farming. Howeverm infrastructure of on sand shrimp farming areas was not fully established. Further more, this area is regularly affected by storms, tropical depressions lead to great impacts on the environment.
In past years, the environmental management has been focused by the localities in the South Central provinces, in which, environmental monitoring has been regularly implemented by localities to timely grasp the changes of weather, water quality to have warnings for aquaculture farmers having solutions.
According to the environmental monitoring results in the provinces of the South Central region, the temperature in this area measured ranges from 26.0 to 32.3oC. This temperature is within the preferred range, suitable for brackish shrimp culture according to QCVN 02-19:2014/BNNPTNT. There is no significant difference between farming areas.
Salinity measured at the water areas for brackish water shrimp farming areas in the South Central region over the years usually ranges from 0 to 36‰. This are suitable for brackish shrimp culture according to QCVN 02-19:2014/ BNNPTNT (5-35‰), except salinity at the monitoring points in Binh Dinh often <5‰ when floodwater returns and salinity at monitoring points in Khanh Hoa tends to be high at hot sunshinetimes.(Salinity: 35-36 ‰).
The pH value are measured results from 6.7-9.4. Most pH values are suitable for brackish shrimp (pH = 7-9), but there are some pH values in inland canals in Quang Nam and Quang Ngai that are outside the allowable limits. However, the trend is not clear, only locally in 2015.
Alkalinity ranges from 5-213 mg/l. In particular, the water supply in brackish shrimp culture areas in Phu Yen, Khanh Hoa has stable alkalinity and in the range suitable for brackish shrimp culture according to QCVN 02-19:2014/ BNNPTNT (Alkalinity: 60- 180 mg/l); The farming areas in Quang Nam, Quang Ngai and Binh Dinh often have lower alkalinity than that prescribed by fresh water; The farming areas in Ninh Thuan have high local alkalinity due to the supply of water from the wells.
The dissolved oxygen content (DO) in most monitoring points is within the allowed limit value in QCVN 02-19: 2014/BNNPTNT (DO> 3.5 mg/l). However, some monitoring points in Quang Nam, Quang Ngai and Binh Dinh have low DO levels locally in 2015.
H2S content ranged from 0.001 to 0.016 mg/l is within the appropriate range for brackish shrimp culture according to QCVN 02-19: 2014 / BNNPTNT. There is no significant difference between farming areas.
The concentration of TSS often increases after the rain, especially in the areas of inland and lagoon areas. Parameters indicate pollution such as ammonia, nitrite, phosphate, COD in most water bodies tend to increase in the end of the crop because people improve ponds to prepare for new crop. The ammonia content has a significant difference among the field observation points, the coastal and downstream river channels.
The content of heavy metals (Pb, Cd, Hg) and residues of Cacbarmate-based pesticides in water samples from undetectable are much lower than the allowed limit values under QCVN 10-MT : 2015/BTNMT. There is no impact on the health of farmed shrimp.
The composition of algae at the monitoring points is relatively rich. However, few cases of detecting toxic algae, the time of detecting toxic algae often in the hot sunshine period, high water temperature, the ability to decompose large organic substances facilitates the development of harmful algae.
Total Vibrio bacteria are found on most monitoring points and months of the year. Vibrio density ranges from <10-8.7x104 cfu/ml, exceeding the permitted level by 33.4% of the total collected samples.
V.parahaemolyticus is capable of causing acute hepatopancreatic necrosis in brackish shrimp recorded positive at some monitoring points in Khanh Hoa and Ninh Thuan in March and April.
Le Mai