ASSESS THE CURRENT STATE OF THE ENVIRONMENT IN BRACKISH-WATER SHRIMP-FARMING AREAS IN NAM DINH PROVINCE AND PROPOSING MEASURES TO IMPROVE EFFICIENCY
| Meeting | VIWC2026 |
| Topic | OS4: Water quality and Aquaculture |
| Author | Nguyen Thao Truong PHAM | Toan Duc VU |
| Organization | Institute of Ecology and Works protection No. 267, Chua Boc, Dong Da, Hanoi, Vietnam | Research of Organic Matter (ROOM), Environmental and Life Science Research Laboratory, Thuyloi University, Vietnam No. 179 Tay Son, Trung Liet, Dong Da, Ha Noi, Vietnam |
| ID | 2023.1676263385 |
Content
1. Introduction
According to the report of the Directorate of Fisheries, in 2021 the brackish water shrimp farming area is estimated to reach 740 thousand hectares (equivalent to 100.5% compared to 2020); in which, the farming area of black tiger shrimp is 630 thousand ha, the area of white leg shrimp farming is 110 thousand ha. However, besides the achievements in production, there are also many difficulties faced by shrimp farmers, including problems of disease and environmental control. According to the Department of Animal Health\'s report, in the first eight months of 2021, the total damaged brackish water shrimp farming area was 15,698 hectares, accounting for about 2.2% of the country\'s total shrimp farming area and 96.6% of total aquaculture area suffered damage, mainly white spot disease, acute hepatopancreatic necrosis, and microsporidian diseases.<br>
Nam Dinh is one of the three major shrimp farming provinces of the North, with 72km of coastline, farming here was established in 2000 with the form of extensive farming of sea crabs and tiger shrimp. Breeding form and species are gradually changed over time to suit the needs of economic development and market. Like other shrimp farming areas, farmers here often face difficulties in diseases, environmental degradation and fluctuations. Therefore, the purpose of this study is to assess the environmental status of brackish water shrimp farming in Nam Dinh province and propose solutions to improve efficiency.
2. Methodology and Data
The data is collected from the environmental monitoring task of shrimp farming in Hai Chinh commune, Hai Hau district and Quat Lam town, Giao Thuy district, Nam Dinh province in 2021.
Fig. 1 Sampling sites for water supply in Hai Chinh and Quat Lam
Monitoring parameters and frequency: Temperature, pH, Salinity, Alkalinity, N-NO2, N-NH4, total Sulfide, COD, TSS, Toxic Algae, total Vibrio, Coliforms, Vp AHPND monitoring frequency is 2 times/month and 03 seasons change in April, August and September.
Method of collecting and analyzing samples: Water samples were collected into plastic bottles and kept cold and transferred to the laboratory for analysis of the following parameters: Alkalinity (SMEWW 2320 B: 2011), N-NH4 (SMEWW 4500-NH3 F: 2017), N-NO2 (SMEWW 4500-NO2 B: 2017), COD (SMEWW 5220 C: 2017), TSS (TCVN 6625: 2000), total Sulfide (SMEWW 4500-S2- D: 2017), total Vibrio (Buller., (2004). Shrimp samples were collected and fixed in alcohol 90o and transferred to the laboratory for analysis of acute hepatopancreatic necrosis disease (AHPND)
3. Results and discussion
3.1. Monitoring results of some indicators of water supply
Table 3.1: Percentage of sample is out of allowable limit
| Location | Temperature (oC) | pH | Salinity (%) | Alkalinity (mg/l) | N-NO2 (mg/l) | N-NH4 (mg/l) | H2S | COD (mg/l) | TSS (mg/l) | Total Vibrio | Coliforms (CFU/100ml) | VpAHPND |
| QCVN 02-19:2014/BNNPTNT | 18-33 | 7-9 | 5-35 | 60-180 | ≤0.05 | ≤0.3 | ≤0.05 | ≤10 | ≤50 | ≤1000 | ≤1000 | positive |
| Number of times beyond the allowable limit | 2 | 0 | 1 | 3 | 21 | 27 | 0 | 0 | 8 | 3 | 11 | 1 |
| Number of monitoring | 46 | 46 | 46 | 46 | 46 | 46 | 46 | 46 | 46 | 46 | 46 | 46 |
| Percentage | 4.35 | 0.0 | 2.17 | 6.52 | 45.65 | 39.13 | 0.0 | 0.0 | 17.39 | 6.52 | 23.91 | 2.17 |
Temperature: During the monitoring period, the measured temperature is within the allowable range according to industry standards (TCN:18-33oC) [1]. Particularly in January, the average temperature is lower than the limit value suitable for shrimp farming (>18 oC).
pH: The monitoring results show that pH is an indicator with a stable average value in the monthly monitoring periods, ranging 7.8 - 8.5.
Salinity: Suitable salinity for farmed shrimp is recommended to be from 15-25‰ and no sudden change in salinity [2]. The monitoring point of the supply source is regulated by the sluice that takes saline water from the coast to the canal of the farming area, so the salinity is relatively high, but the monitoring times are priced within the allowable range.
COD: The COD concentration at the monitoring point is in the range suitable for aquaculture. COD in aquaculture pond water is usually in the range of 40-80 mg/l, COD value from 0-50 mg/l is considered good water quality for aquaculture. (Boyd et al., 1998).
Alkalinity: The results of monitoring ponds showed that the alkalinity fluctuated slightly but within the allowable range. Because the supply channel has a sluice that regulates salt water from the sea, the salinity and alkalinity are always maintained at a high level and suitable to natural conditions.
N-NO2: The average N-NO2 concentration in the feed water at the monitoring points is almost too high to exceed the allowable limit. In Hai Chinh there are 8/10 months (except March and September), in Quat Lam 2/10 months (January and February).
N-NH4: According to Boyd et al. (1998) and Chanratchakool P et al. (2003) suitable N-NH4 content for shrimp ponds from 0.2 - 2.0 mg/l. The concentration of N-NH4 in the source water supplied to monitoring points in Nam Dinh is 1.2 times higher than the allowable limit.
Total Sulfide: All monitoring points have the presence of total sulfide but with low concentrations within the allowable limits according to QCVN 02-19:2014/BNNPTNT (<0.05 mg/l).
TSS: In Hai Chinh in January, March and July, Quat Lam in January was higher than the threshold of 50mg/l. These are the beginning of the agricultural season of the year, so the water supply is also affected. When the water is cloudy, the TSS value is usually high.<br>
Toxic Algae: In April, Hai Chinh observed that the concentration of toxic algae Pseudo-nitzschia seriata was 2.6 times higher than the warning limit. Toxic algae in feed water were mainly detected at the beginning of the year, no toxic algae were detected in May-July and October.
Total Vibrio: At the time of January in Hai Chinh, the value exceeded the allowable limit by 1.3 times.
Coliforms: The supply water at the monitoring point generally has coliform fluctuating about 2 times higher than the allowable limit.
Vp AHPND: The water supply in Hai Chinh has an infection rate of 4.35%. The time to record the occurrence of AHPND in the water samples collected from the water supply monitoring points in brackish water shrimp farming areas is in July and August.
3.2. Results of monitoring brackish water shrimp ponds:
In ponds where the water temperature is quite stable because the ponds are over 1.5 m, the salinity is within the allowable limit. The pH value is suitable for the growth and development of shrimp. Alkalinity, COD, TSS, N-NO2 and N-NH4 in ponds are high and affect shrimp culture. Total sulfide in water is low, suitable for shrimp farming. The total concentration of Vibrio bacteria in the water with a low frequency of occurrence in ponds was 6.3% of the samples. However, due to good care, total Vibrio has little adverse effect on farmed shrimp. The pathogen VpAHPND was detected in the water, but all cultured shrimp samples were negative for this pathogen. Farmed shrimp samples were all negative for VpAHPND throughout the growing season.
3.3. Proposing measures
Management measures: Strengthen the management of wastewater treatment and sanctions for violations at farming facilities. Proposing to invest in modern technology applications throughout the farming process.
Proposing management agencies to issue new regulations and standards with a full set of parameters to provide a basis for recommendations to farmers.
Technical measures: Change 20-30% of the water in the pond with a frequency of 3 times/month to reduce alkalinity and TSS. Using probiotics containing strains of Nitrobacter, Nitrosomonas, Bacillus to decompose N-NH4, N-NO2, P-PO4 and organic matter, cleaning ponds. Limit running water fans during the day, treat algae with microbial products, after 2 days of microbiology to treat pond bottoms to decompose dead algae that accumulate on the pond bottom. In the hot season, it is necessary to keep the water level in the pond from 1.3-1.8m to stabilize the temperature of the pond, to reduce the phenomenon of shrimp suffering from heat shock.
4. Conclusion
The monitoring points have 10 parameters with observed samples exceeding the permissible limit, in which the parameters with the sample rate exceeding the permissible limit greater than 10% include: N-NO2 (45.65%), N-NH4 (39.13%) ), coliform (23.91%) and TSS (17.39%). Detection of AHPND in feed water samples at Hai Chinh in July and August. The pathogen of acute hepatopancreatic necrosis disease (AHPND) was detected in the water but all cultured shrimp samples were negative for this pathogen.
5. Acknowledgement
The authors would like to thank the strong research group (Research of Organic Matter, ROOM), Environmental and Life Science Research Laboratory, Thuyloi University for their support during the research.
6. Reference
Domestic documents
- QCVN 02-19:2014/BNNPTNT : Quy chuẩn Kỹ thuật Quốc gia về cơ sở nuôi tôm nước lợ
- Chanratchakool, 1995. White patch disease of black tiger shrimp (Penaeus monodon). AAHRI Newsletter 4.
- Chanratchakool P, Turnbull, J.F., Funge-Smith, S.J., Macrae, I.H., Limsuwan, C., Quản lý sức khỏe tôm trong ao nuôi. Tái bản lần thứ 4. Nguời dịch: Nguyễn Anh Tuấn, Nguyễn Thanh Phuong, Ðặng Thị Hoàng Oanh, Trần Ngọc Hải. Danida-Bộ Thủy sản 2003. 153 p.
- Boyd, C.E., Aquaculture, A.U.I.C.f., Environments, A., 1998. Water Quality for Pond Aquaculture. International Center for Aquaculture and Aquatic Environments, Alabama Agricultural Experiment Station, Auburn University.
