CoastGIS03 - Genova – Oct. 16-18, 2003 GIS in support to data analysis for enhanced sustainability of shrimp farming in the Mekong Delta, Vietnam The Gambas.

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