Ministry of Agriculture and Rural Development COLLABORATION FOR AGRICULTURE AND RURAL DEVELOPMENT (CARD) 002/05 VIE Technical and economic feasibility of applying the Better Management Practices (BMP) to household aquaculture in Vietnam MS 6: BMP training manual ENVIRONMENT MANAGEMENT IN AQUACULTURE Mai Van Ha Nguyen Duc Binh Research Institute for Aquaculture No.1 Bac Ninh, 2007 INTRODUCTION 4  ENVIRONEMNT MANAGEMENT IN POND AQUACULTURE 4  1.1 Why environment management 4  1.1.  What influences water quality 4  1.2.  Environment management of culture area and ponds 5  2.  ENVIRONMENT PARAMETERS 5  2.1.  Culture area and water depth 5  2.2.  Water temperature 5  2.3.  Water transparency 6  2.4.  Water color 6  2.5.  pH 6  2.6.  Dissolved Oxygen (DO) 7  2.7.  Salinity 7  2.8.  Alkalinity 7  2.9.  Biologically decomposable matter (measured as COD and BOD) 8  2.10.  Ammonium (NH4+) 8  2.11.  Phosphorus PO43- 8  2.12.  Amonia (NH3) 9  2.13.  Nitrite (NO2) and Nitrate (NO3) 9  2.14.  Hydrosunfure (H2S) 9  2.15.  Iron ( Fe2+, Fe3+ ) 10  3.  MEDTHODS AND ENVIRONMENTAL STANDARDS 11  3.1.  Methods of water quality analysis and measurement 11  3.2.  Environmental standard/norm in aquaculture 11  4.  SAMPLING STRATEGY AND PRESERVATION METHOD 12  4.1.  Critical rules of sampling method 12  4.2.  Sampling procedure 12  5.  EFFECTS OF ENVIRONMENTAL FACTORS TO SHRIMP HEALTH 13  5.1.  Weather and climate condition 13  5.2.  Pond characteristic 14  5.3.  Effects of weather condition on environment of shrimp ponds 14  6.  ATTENTIONS ON SHRIMP CULTURE MANAGEMENT 14  6.1.  Geographical location and environment 14  6.2.  Culture management 15  7.  POND PREPARATION 15  7.1.  Lime utilization 15  7.2.  Use of algicide 16  7.3.  Treatment of in-pond produced substances 16  7.4.  Disinfection 17  7.5.  Removal of Plankton and benthic organism 17  7.6.  Water color induction fertilization 18  8.  REFERENCES 19  INTRODUCTION Aquaculture in Vietnam, particularly shrimp culture has been developing rapidly with reagrds to both acre and production However, shrimp productivity is unstable, product quality and sanitation requirement is getting worse It is uncontroversal that unplanned development and limited technical know-how are the disadvantegs Under CARD- funded project “Technical and Economic Feasibility of Applying Better Management Practices to household aquaculture in Vietnam” environment management activities was a critical component that support a succesful application of BMP protocal among aquafarmer community The decoment represents water quality management princible, practical aspects, real coming up issues and its remediation acordingly ENVIRONMENT MANAGEMENT IN POND AQUACULTURE 1.1 Why environment management Host Pathogens Water Figure 1: Relationship environemnt- related component in water + Water environment is habitat of aquatic animals including aquaculture species + Good environment ensures higher growth rate of culture and less disease causedagents + Poor water quality results in poor growth of culture and more disease germs Water quality management is to minimize risk of water pollution (limited toxic subtances and disease germ) 1.1 What influences water quality + Weather condition (rainy, sunny, stormy) + Bottom soil property: sand/dy, mud/dy + Human- origined influences 1.2 Environment management of culture area and ponds * What water parameters needs monitoring + Pond area, water deapth + Transpearency (by algae density) + pH, alkalinity, salinity + Dissolved oxygen (DO) + Toxic gases: NH3, NO2, H2S, CH4 + Organic sediments: assessed via content of COD and BOD + Nutritional form: NH4, PO4 * Where to monitor within culture area Water course, dishcarged water and inside ponds 2.1 ENVIRONMENT PARAMETERS Culture area and water depth + Suggested culture area of more than 3000m2 + Suitable water depth of 1.2m – 1.6m (1,5m - 2,0m) Appropreate culture and less changeable water depth will experience less fluctuation of water temperature due to suddenly change of wheather condition like heavy rain, sunny, monsoon, Water depth measurement is normally checked using depth gause fixed in the pond during culture duration 2.2 Water temperature + Culture species like shrimp and crab are cold- blooded, body temperature change following ambient environment Sun energy plays an crucial role in feed ingestion and nutrient uptak Suitable water temperature for black tiger shrimp is 25 - 33oC + Water temperature change with the change in diunal and seasonal weather condition It is normally higher during daytime and summer time + It is an advantage of water that heat holding capacity is quite high leading to more stable water temperature than embient temperature Familiar tool to check water temperature is themometer 2.3 Water transparency Water transparency is an indication of: + Algal community + Light panitration In shrimp ponds suitable algal density of more than mil cells/l, equavilant to transparency of 10 - 40 cm In natural water body, less algal community obsered, normally less than mil cells/l, if no alluvium and colloid Secchi disc present water clearness up to 100 cm Suitable transparency in aquaculture is of 25-40 cm Secchi dics is used to measure water transparency 2.4 Water color Water colour experienced from: + Sand, alluvivum, colloid, + Plankton organism: mainly algae - Cyannophyta causes water greeny, - Euglenophyta cause brownish yellow, - Dinophyta/ Pyrophyta causes brown or blackish brown colour - Chrophyta, bacillariophyta experience blue colour - Organic ditritus: blackish and stenchy What water colour influences water quality + It really depends on what is the constitution of warter colour Water with greater alluvium, organic sediment, phytoplankton has higher nutrient level + If scum of any form and colour appears on the water surface there shoule be a need to remove or water exchanged Giving a frequent observation on water color as it is an indication of positive or negative message resulting to a further right remediation and treatment 2.5 pH pH of of any water falls into 1- 14 + Acidic water: pH < 6,5 + Neutral water: pH from 6,5 – 8,5 + Alkaline water: pH > 8,5 What causes the chagne in pH + Acid rain resulting pH reduction + Water exchange leading pH fluctuation + Algal community (high algal density experiences greater gradient of pH) + Liming during pond preparartion and treatment/disinfection What influences caused by pH changing + Low pH cause more PO4 absorption by bottom sediment leading to poor algal community + Low pH induces more heavy mental resuspention from pond bottom + Great fluctuation of pH causes stress for culture species, more susceptible to disease infection as a result 2.6 Dissolved Oxygen (DO) DO comes either from: + Disfusion from atmosphere + Photosynthesis by phytoplankton community: CO2 + H2O > living biomass + O2 + Oxygenation devices/aeration Lossing DO due to: + Respiration of aquatic animals + Baterial decomposition of organic matter: uneatent fish, dead animals Pond fertilisation regime and feeding startegy should be well planed, regular checking DO to avoid anoxic condition The role of DO to aquatic animals + Consumed in all organic oxidation and toxic gases degeneration + DO should maintained at more than 5,0 mg/l + A suggested algal density of – mil./l could balance DO at a right level in water + Phytonsynthesis by aquatic plant and alage causes significant diual fluctuation of DO, minimum level of pH falls at – AM while highest value can be recorded at 1-2 PM 2.7 Salinity Salinity, mainly known as NaCl, gives suitable concentration for many aquaculture species at 15-25‰ 2.8 Alkalinity What constitutes alkalinity + Alkalinity measured as mg CaCO3/l indicates concentration of ions HCO3, CO32-, OHpresent in water + Hardness as mg CaCO3/l is measured by ion level of Ca2+ Mg2+ What is the role of alkalinity + The concentration of Cacbonate (CO32-) and bicacbonat (HCO3-) compounds is propotional to primary productivity by phytoplankton, that’s why pond of higher alkalinity level will give higher yeild of culture species + Liming (use of CaCO3) is a enevitable key to encrease alkalinity to suggested concentration of 80-120 mg/l 2.9 Biologically decomposable matter (measured as COD and BOD) In natural waters and culture ponds, besides respiration process of aquatic animals that consume oxygen, a careful consideration needs to pay on intertrasformation of organic maters (quantified as mg DO/l as COD and BOD) that also realy use a great amount of DO Where BOD and COD comes Due to the accumulation of detritus, uneaten feed, excreate of culture species, dead oganisms Possible impacts COD >30mg/l ; BOD >10mg/l ( an indication of water pollution COD from 10-20mg/l ; BOD from – 10mg/l (suitabe level for aquaculture COD < 10mg/l ; BOD < 5mg/l (poor potential nutrient loading) 2.10 Ammonium (NH4+) Nitrogen nutrient can be of: NH4, NO2, NO3+ NO2 can be easily transformed to NH4 or NO3 depending on DO level and microoganism + NH4 and NO3- can be directly uptaken by phytoplankton community, especially by microalgae Where they comes from: Nitrogen fixation bacteria (symbiosis to phytoplankton or water hyacinth) Biological decomposition of organic mater including detritus and dead aquatic organisms to produce inorganic nitrogen as following: Organic nitrogen- > NH4 NO2 NO3Additional pond fertilisation It is noted that frequent application of Urea will results in loower water and bottom soil pH 2.11 Phosphorus PO43- Where it comes from + Resuspension from bottom soild/mud in certain condition: Availability of phosphorus in bottom soil, pH of water (greater rate of phosphorus resolution at high pH) + Decomposition of organic matter + Additional fertilisation (use of phospate fertilizers) What form of phosphorus found in water + Phosphate compounds: PO4, HPO4, H2PO48 + Soluble reactive phosphorus: PO4 Phosphorus is a controlling element of water’s productivity based on algal yield The concentration of PO4 at 0.3-0.5 mg/l is recognized suitable for pond aquaculture 2.12 Amonia (NH3) + NH3 is generated during decomposition of rich nitrogen compound + In alkaline water, all NH4 will be converted into NH3 NH3 + H2O NH4+ + OHPossible impacts by NH3 + NH3 is really toxic to aquatic organisms, while NH4+ is of harmless + Organic polluted water normally has NH3 concentration of more than 1,0 mg/l How to eliminate NH3 + Good feeding strategy (amount and frequency) + Water exchange and addition + Control pH of not over 8,0 and water temperature less than 32oC + Maintaining right level of alkalinity and hardness 2.13 Nitrite (NO2) and Nitrate (NO3) Where it comes + Nitrite is an intermediate product of organic nitrogen deomposition process In oxic water, ammonium (NH4+) will be biologically oxidized to nitrite (NO2-) and then nitrate (NO3-) + While in anoxic environemnt, NO3- will be reduced to NO2- + Pond of well- management and aeration, NO3- level is normally high and low NO2; and viversa What influences + NO2- level is an indicates of pond condition: poor water quality Low DO and pollution + NO2- can even be toxic to culture species at quite low concentration of 0,1 mg/l + NO3- is harmfulless to aquatic anaimals 2.14 Hydrosunfure (H2S) Where it comes + Mainly from decomposition of dead aquatic organisms + Anoxic organic decomposition + Acummulation of organic sediment What influences to environment and culture species + H2S is a gas of rotten- egg stench and toxic + High solvency capacity in water experiencing low acidic water acordingly + H2S will combine blood oxygen leading to anoxia symtom, and stain nervous system aas a result + Concentration of H2S in water ranges more os less 1,0 mg/l How to eliminate H2S + Oxygenation + Removing bottom mud layer + Replacing with clean water 2.15 Iron ( Fe2+, Fe3+ ) Where they come + Soil (high land and stone) with high level of FeO, Fe2O3 + Coastal soil and tidal zone of high FeSO4 Influence in water environment + Water dissolved ferrous compounds to release ion Fe2+, Fe3+ + Solvency of iron compound is higher in acidic environemnt (low pH) + In alkaline environment iron ions will form precipitated hydroxyte Remediation to discard iron + Water aeration for precipitation forming on bottom that required to remove in the and of production cycle + Liming will lead to precipitation down to pond bottom 10 3.1 METHODS AND ENVIRONMENTAL STANDARDS Methods of water quality analysis and measurement Or Method Water parameter Sensor Test Kit Chemical Others Water depth Fixed ruler Water temperature Transparency Secchi disc Water colour Naked eyes pH + + + DO + + + Alkalinity + + Salinity COD and BOD + Themometer + + 10 NH4 and PO4 11 + Hydrometer + 3- + + NH3 ,NO2 NO3 + + 12 H2S + + 13 Fe total + + 3.2 Environmental standard/norm in aquaculture Or Water parameter Unit Norm Water temperature o C 25 – 33 Transparency cm 25 – 40 Water depth m 1,2 - 2,0 Water colour pH DO mg/l > 5,0 Alkalinity mg/l 80 – 120 Satlinity ‰ 15 – 25 COD mg/l 10 – 20 10 BOD mg/l – 10 11 NH4+ mg/l 0,5 - 1,0 12 PO4 3- mg/l 0,3 - 0,8 13 NH3 mg/l < 0,10 14 NO2 mg/l