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CoastGIS’03 - Genova – Oct. 16-18, 2003
GISin support to data analysis for enhanced sustainability of
shrimp farming in the Mekong Delta, VietnamThe Gambas project
Jacques Populus*, Raweewan Nutpramoon**, Jean-Louis Martin***, Pascal Raux****, Yves Auda*****, Hoang
Son******
* Ifremer, DEL/AO, Centre de Brest, 29280 Plouzané, France
** GISTDA, Bangkok, Thailand,*** Crema, France****CEDEM-UBO, Brest,**** CESBIO, Toulouse, France***** Institute of Oceanography, Nha Trang, Vietnam
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasExtensive Mekong delta aquaculture
Mekong delta
• 450 000 ha ponds
• 90 000 households
• 120 000 tons
• 60 000 ha mangrove left
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasHow about sustainability?
Technical sustainability Economical sustainability Social equity
Efficiency : Average yield in Ca Mau province
Year Average yield (kg. ha-1)
1990 408
1991 476
1992 387
1993 305
1994 234
1995 219
1996 262
2001 329
2002 282
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasFactors contributing to sustainability
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasLocation of study sites
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasStations in Tra Vinh site
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasData collected
• Land use : soils, vegetation, biodiversity
(31 stations)
• Hydrobiology: water and sediment
(22 variables)
• Hydraulic: tide, water levels
(Camau only)
• Practise and socio-economics
(Survey of 160 farms)
CoastGIS’03 - Genova – Oct. 16-18, 2003
GambasProcessing Spot imagery for land use mapping
Five ecological zones are identified
I : paddy, orchards, householdsII : mixture of shrimp ponds andmangroveIII : dominant mangroveIV : natural shoreline mangroveV : shoreline sandy ridges
Spot 4 image January 22nd,
2001
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Processing Spot imagery for land use mapping
Spot 4 image January 22nd,
2001
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 1: yield versus mangrove
Percentage of mangrove within 2 km around stations
Total yield per ha per year
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 1: yield versus mangrove
the general value of « natural » mangrove is universally recognised
however the value of mangrove replanted in ponds is questioned (shadows, sudden salinity drops, tannins)
Therefore, the « separate » sytem should gradually replace
the mixed system
Clough, 2002
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 2: PCA on water quality
Two clusters: particulate (TSS) and primary production
Salinity : inversely correlated to TSS group (dominance of rainy season)
Stations clustered in seven groups according to PCA
Definition of “key variables “ (indicators)
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 2:
hydrobiological zonation
Each zone qualified by its most striking features TSS Bacteria Organic matter
(OM)
Detritic organic matter rules the system
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 2: organic matter in sediment
Higher TSS in Camau, even in dry season, leading to accumulation
of detritic OM
CoastGIS’03 - Genova – Oct. 16-18, 2003
Aver.Yield per crop
Profit rate
Gambas Analysis 3: farm classification (global)
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 3: farm classification per ecological zone
PostulatePostulate- The hydrobiological zones are homogeneous- The hydrobiological zones are homogeneous
- Discrepancies in yields are explained by “management”- Discrepancies in yields are explained by “management”• Either farm structure parametersEither farm structure parameters• Or Crop practice parametersOr Crop practice parameters
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 3: farm classification per ecological zone
Zone 6, Tra VinhLow TSS Level
• environment is the key factor for successful cropsenvironment is the key factor for successful crops• yet, most thorough pond preparation and monitoring arefound hereyet, most thorough pond preparation and monitoring arefound here• farmers ought to remain at reasonable intensification levelfarmers ought to remain at reasonable intensification level
(4 to 6 PL/ (i.e. 10 PL/m²)(4 to 6 PL/ (i.e. 10 PL/m²)• water "top up" seems to be the most efficient techniquewater "top up" seems to be the most efficient technique
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 3: farm classification per ecological zone
Zone 4, Ca MauHigh DON
"Good" farms without wild species
"Bad" farms without wild species
"Bad" farms with wild species
Stocking Density (PL/m²) 1.7 3.6 1.7
Yield Monodon (Kg/ha) 185 63.8 63
Yield Wild (Kg/ha) - 9
Technical efficiency (Kg/1,000 PL) 3.7 0.3 1
Profit Rate 71% -93% -17%
Profit/Kg (1,000 VND/Kg) 75 -73.5 -16.5
Nb of crops 2 to 3 3-4 to 5-6 5 to 6 mainly
Shrimp/Paddy systems mainly
Recommendations in Ca Mau High DON:Recommendations in Ca Mau High DON:
• Reduce crop numberReduce crop number• Stoking Density < 2 PL/m² Stoking Density < 2 PL/m² • Avoid chemical and artificial feedAvoid chemical and artificial feed• Target null energy cost (feeding) by relying on Target null energy cost (feeding) by relying on
environmental capacityenvironmental capacity
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 3: farm classification per ecological zone
Zone 3, Ca Maucore
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Analysis 3: farm classification per ecological zone
• distribution of practises similar among worst and best farmsdistribution of practises similar among worst and best farms• from a technical point view, all semi-extensive farms belong to from a technical point view, all semi-extensive farms belong to
the worst farmsthe worst farms
• Remain at low intensification level (2PL/m²)Remain at low intensification level (2PL/m²)• No feed supplyNo feed supply• Further look at post-larvae qualityFurther look at post-larvae quality
H3 BestH3
IntermediateH3 Worst
Farms number 20 6 19Pond Area (ha) 1.8 2.65 1.4Stocking Density (PL/m²) 2.8 5.5 2.9Yield Monodon (Kg/ha) 116.8 170.1 140.7Yield Wild (Kg/ha) 121.5 61.4 41.7Profit Rate 45% -13% but mixed -50%Technical efficiency (Kg/1,000 PL) 1.6 1.4 2.1Survival Rate 9% 4% 4%Nb of crops 3.6 3.3 4
Zone 3, Ca Maucore
Precautionary approach:Precautionary approach:
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Conclusions 1
The environment is adverse, due to high organic load, reduced primary production and reduced trophic chain development
Intensification is NOT sustainable: collapses appear rapidely, unless stocking densities are kept low
the key question is how, NOT how much to produce (low risk to households)
Re-design of farm layout necessary,with regard to mangrove, tending to “organic” farming
Some sub-areas may allow “semi-intensive” conditions (SD<6), but costs are to be kept low
The study allowed the creation of a corpus of data on Mekong aquaculture
Key eclogical indicators for monitoring/selecting sites can be proposed
CoastGIS’03 - Genova – Oct. 16-18, 2003
Gambas Conclusions 2
The study allowed the creation of a corpus of data onMekong aquaculture and environment
Key eclogical indicators for monitoring/selecting sitescan be proposed
Salinity/pH TSS Total OM DBO Vibrio