technical and financial comparison of giant freshwater prawn (macrobrachium rosenbergii) farming systems in the flooding areas of the mekong delta

CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES TRUONG THANH LAM TECHNICAL AND FINANCIAL COMPARISON OF GIANT FRESHWATER PRAWN Macrobrachium rosenbergii FARMING SYSTEMS IN THE

CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES

TRUONG THANH LAM

TECHNICAL AND FINANCIAL COMPARISON OF

GIANT FRESHWATER PRAWN

(Macrobrachium rosenbergii) FARMING SYSTEMS IN

THE FLOODING AREAS OF THE MEKONG DELTA

GRADUATION THESIS FOR BACHELOR DEGREE IN AQUACULTURE

2012

CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES

TRUONG THANH LAM

TECHNICAL AND FINANCIAL COMPARISON OF

GIANT FRESHWATER PRAWN

(Macrobrachium rosenbergii) FARMING SYSTEMS IN

THE FLOODING AREAS OF THE MEKONG DELTA

GRADUATION THESIS FOR BACHELOR DEGREE IN AQUACULTURE

INSTRUCTED BY ASSOCIATE PROFESSOR: LE XUAN SINH

2012

CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES

-

THESIS APPROVAL

The Degree of Bachelor of Science in Aquaculture

DEPARTMENT: Fisheries Management and Economics

TITLE: Technical and financial comparison of giant

freshwater prawn (Macrobrachium rosenbergii) farming

systems in the flooding areas of the Mekong Delta.

NAME: Mr Truong Thanh Lam

THIS THESIS HAS BEEN ACCEPTED BY

ACKNOWLEDGEMENT

My special thanks are given to Associate Professor Le Xuan Sinh for his supervision comments that helped me to conduct and to complete this dissertation

Thanks to the teaching staff of College of Aquaculture and Fisheries – Can

Tho University and students of Advance Aquaculture Program Class

Course 1 st , Fisheries Economics Class Course 35 th and friends for zealous help during the period of collecting and analyzing the data for this dissertation Thanks to the officers at Deparment of Fisheries of An Giang and Dong Thap provinces and Can Tho city for helping me in collecting data in the fields Finally, I would like to thank to my family and friends for encouraged and made the best conditions for me during my study of bachelor program in aquaculture

Truong Thanh Lam

ABSTRACT

In the Mekong Delta, giant freshwater prawn (Macrobrachium

Rosenbergii) is primarily and commonly cultured in flooding areas such as An

Giang, Dong Thap and Can Tho provinces, mainly in the rainy or flooding season This study was carried from May to December 2012 through the surveys of 146 prawn farmers focusing on the technical and financial aspects

of four farming systems in the rice file: (1) rotation of prawn – rice in closing dykes; (2) rotation of prawn – rice in opening dykes; (3) mono – prawn culture

in closing dykes; and (4) mono – prawn culture in opening dykes Beside, 146 rice farmers in the same area also interviewed about their perceptions on farming prawn Data were collected and analyzed by descriptive statistic and cross – tabulation to compare technical – financial aspects of these prawn farming systems

The farm size was large with the average cultured area of 2.83 ha (±2.92) Farmers stocked PL stage 8 – 12 (PL8 – 12) of giant freshwater prawns in a wide range of time, from March to September (2nd to 8th month in lunar calendar) with an average stocking density of 13.14 PLs/m2 (±3.96); Prawns were fed by artificial feed and home – made feed Female prawns were gradually harvested after stocking 3 months and all prawns were harvested after stocking about 213.8 days (±30.6) equaling to an average yield of 1.51 tons/ha (±0.52) Average total production cost for prawn culture was VND 134.3 mil./ha/crop (±32.6), and then brought about an average net income of VND 169.1 mil./ha/crop (±92.8) B:C ratio of 4 farming systems was 2.2 times/crop and rate of NI/TC was 1.2 times/crop The biggest constraints faced

by prawn farmers consisted of: (1) Threats from pesticides, herbicides and chemicals used for rice cultivation following the public water ways; and (2) Uncertain quality and sources of post larvae which caused high rate of mortality

Average yield of rice of farmers both rice farmers and rice in prawn cultured areas was 7.8 tons/ha/crop Total cost for rice of prawn farmers was higher than rice farmers and average net income from rice of two group of farmers was VND 26.2 mil./ha/crop Farming prawn effects on farming rice strongly on amount of fertilizers used and cost for chemicals, pesticides or herbicides

Key words: giant freshwater prawn, flooding season, Mekong Delta, rice,

mono-culture, rotation systems

TABLE OF CONTENT

ACKNOWLEDGEMENT ii

ABSTRACT iii

LIST OF TABLES viii

LIST OF FIGURES viii

LIST OF ABBREVIATIONS viii

Chapter 1 INTRODUCTION 1

1.1 Background 1

1.2 Objectives 2

General objective: 2

Specific objectives 2

Chapter 2 LITERATURE REVIEW 3

2.1 Biological characteristics of Giant freshwater prawn 3

2.1.1 Classification 3

2.1.2 Life cycle 4

2.1.3 Sexual differences 5

2.1.4 Growth characteristics 5

2.1.5 Demand for nutrition 5

2.1.6 Environmental condition 6

2.2 Production of giant freshwater prawn in the world 6

2.3 Production of gi ant freshwater prawn in Viet Nam 7

2.4 Production of GFWP in the Mekong Delta 7

2.5 Technical – financial aspects of farming giant freshwater prawn 9

Chapter 3 RESEARCH METHODOLOGY 11

3.1 Scope of the research 11

3.2 Material 11

3.3 Data collection 11

3.3 Data analysis 14

Chapter 4 RESULTS AND DISCUSSIONS 16

4.1 General information 16

4.2 Technical aspects: 17

4.2.1 Design farming systems 17

4.2.2 Total land areas, prawn farming areas and construction 19

4.2.3 Farming area preparation 21

4.2.4 Seed and stocking 21

4.2.5 Feed and feeding management 23

4.2.6 Water management 24

4.2.7 Health management 25

4.2.8 Harvest 26

4.3 Technical & financial results of GFWP farming systems 27

4.3.1 Survival rate, harvest size and sexual rate 27

4.3.2 Productivity 28

4.3.3 Production cost 29

4.3.4 Net income 30

4.3.5 Economics effectiveness of the systems 31

4.4.1 Comparison yield, cost, revenue and net income of rice between rice in the systems and rice of rice farmers in the same location 32

4.4.2 Total cost, revenue and net income of prawn household and contribution of prawn farming 33

4.4.3 Effects of farming prawn on rice in the same areas 34

4.4.4 Cost for living activities and accumulate ability of farm household 34

4.5 Farmers‟ perceptions 35

4.5.1 Reasons for the rice farmers did not cultured prawn and conditions to apply prawn farming 35

4.5.2 Reasons for the farmers currently applied prawn farming systems 35

4.5.3 Perceptions of using home-made feed 36

4.5.4 Aquatic species which are encouraged to develop 36

Chapter 5 CONCLUSIONS AND SUGGESTIONS 37

5.1 Conclusions 37

5.1.1 Prawn farming systems 37

5.1.2 The farming of rice in and out prawn culture areas 37

5.2 Suggestions 38

APPENDIX: DATA ANALYSIS 43

APPENDIX: QUESTIONAIRES 57

LIST OF TABLES

Table 2.1: Characteristics to distinguish between male and female GFWP 5

Table 2.2: Demand for nutrition of GFWP 5

Table 3.1: Sample size in study areas (prawn farmers) 12

Table 4.1: Farming areas of prawn farmers 20

Table 4.2: Design of prawn farming areas 20

Table 4.3: Time and methods of field preparation 21

Table 4.4: Prawn seed 22

Table 4.5: Feed and feeding methods 24

Table 4.6: Water management in farming period of GFWP 25

Table 4.7: Common diseases and effectiveness of treatment 25

Table 4.8: Harvest time 26

Table 4.9: Survival rate, harvest size and sexual rate 27

Table 4.10: Production and revenue of prawns 28

Table 4.11: Cost structure of farming prawn 29

Table 4.12: Net income of farming prawn systems 30

Table 4.13: Economics effective of systems 31

Table 4.14: Yield, cost, revenue and net income of rice 32

Table 4.15: Cost structure of systems 33

Table 4.16: Total cost, revenue and net income for prawn household and contribution of prawn farming 33

Table 4.17: Monthly activities expenditure and accumulate ability from prawn of farmers 34

LIST OF FIGURES

Figure 2.1: Apperance of Giant feshwater prawn 3

Figure 2.2: Life cycle of giant freshwater prawn 4

Figure 2.3: Map of the Mekong delta with the study sites 8

Figure 4.1: Rotation of prawn–rice in closing dykes (S1) 17

Figure 4.2: Rotation of prawn–rice in opening dykes (S2) 18

Figure 4.3: Mono-prawn culture in closing dykes (S3) 18

Figure 4.4: Mono-prawn culture in opening dykes (S4) 19

Chapter 1 INTRODUCTION

1.1 Background

Giant freshwater prawn (Macrobrachium rosenbergii, de Man, 1879) is

the biggest size among freshwater prawn species It is the significant object in aquaculture and fisheries In nature, this species mostly distribute in large area from Australia to New Guinea, China and India In the year 2010, global aquaculture production for this species was about 215,000 tons, attained the value USD 1.159 billion (FAO, 2010)

In Viet Nam, giant freshwater prawn was found mostly in the Mekong Delta Its reproduction researches were begun in the period 1977 – 1979 and got satisfactory results Follow that, culture models were discovered and applied in large area such as: culture in the rice field, semi-intensive culture system in pond, culture in irrigation canal,… With these developments, productivity of giant freshwater prawn is increasing year by year to strive for achieving at 22,800 tons in the year 2015 (Directorate of Fisheries, 2012) The Mekong delta has advantages of water area, which has potential development for aquaculture In which, GFWP is the significant species In 2006, total area

in Mekong Delta for culturing GFWP was 9,077 ha with yield total production

of 9,514 tons (Sinh, 2008)

An Giang, Dong Thap and Can Tho provinces have a long history of aquaculture With traditional rice farming and advantage of water area, local farmers combined rice and prawn together They cultured prawn in rice field

in flooding season This successful model because of better environmental

conditions when compare with dry season Topic “Technical and financial

comparison of giant freshwater prawn (Macrobrachium rosenbergii) farming systems in the flooding areas of the Mekong Delta” is important to

help indentifying which systems are suitable for farming giant freshwater prawn and understand the problems or advantages for development of this species in the study areas and the Mekong Delta

1.2 Objectives

General objective:

To describe the farming practices and to analyze the major technical and financial indicators as well as to suggest that helps to contribute to further development of prawn culture in the study areas and the Mekong Delta

Chapter 2 LITERATURE REVIEW 2.1 Biological characteristics of Giant freshwater prawn

Physical characteristics (FAO, 2002)

It has a very long rostrum, with 11 – 14 dorsal teeth and 8 – 10 ventral teeth (the ventral characteristics are especially important);

The tip of its telson reaches distinctly beyond the posterior spines of the telson;

The adult male has very long second chelipeds in which all segments are elongate and have blunt spines;

The movable finger of the second chelipeds of the adult male is covered

by a dense velvet-like fur (except the extreme tip) but this fur is absent from the fixed finger and the rest of the cheliped; and

It is the largest known of all Macrobrachium species, adult males having been reported with a total body length of up to 33 cm, and adult females of up to 29 cm

movement tendency to freshwater area: river, field, pond,…to living and growth to adult

2.1.3 Sexual differences

In same age, the male prawn grows faster and has bigger size than the female Male and female prawn can be distinguished by below characteristics:

Table 2.1: Characteristics to distinguish between male and female GFWP

Size & head Bigger

Genital pores Between the base of the 5th

2.1.5 Demand for nutrition

Giant freshwater prawn is an omnivorous species However, their food

is mostly animal such as: aquatic worms, insects, small mollusk, crustacean, flesh and offal of fish and other animals They can be feed on gains, nuts, seeds, fruits, algae, tender leaves and stems of aquatic plans (Nandlal and Pickering, 2005) Nevertheless, the optimal food has to content:

Table 2.2: Demand for nutrition of GFWP

Component Percentage in quantity of food (%)

best development in freshwater (Phuong et al., 2003)

c pH

In prawn, optimum pH range for growing is 7.0 – 8.5 pH below 6.5 or higher than 9.0 in a long period can effect on development of all stage of

prawn (Phuong et al., 2003)

Besides, toxic gases and chemical in living area can effect on development and survival rate of prawn

2.2 Production of giant freshwater prawn in the world

In the year 1962, history of culturing GFWP was begun by Ling, with the success of nursed larva and description of different phases at larva stage Four years later, Fujimura was successful in hatchery prawn used green water system at Hawaii with broodstock from Malaysia Open system was researched and completed in the year 1977 by AQUACOP Nowadays, many culture models are using in the world: culture in the rice field, culture in irrigation canal, single culture in cage, pen,…These systems are classified into extensive, se-mi intensive and intensive system which have different culture area, stocking density and health care In the year 1984, production of prawn

in the world was 5,246 tons It increased to 17,608 tons in the year 1989 and over 119,000 tons in the year 2000 Asian is the continent that produces the majority of giant freshwater prawn in the world with essential countries: China, India, Viet Nam, Thailand,…They contributed 94% production of the world (FAO, 2002)

2.3 Production of gi ant freshwater prawn in Viet Nam

In Viet Nam, GFWP culture has long history with traditional extensive culture system based on natural juveniles and food After the year 1980, the farming of prawn started to develop both in north and south of Viet Nam with the development of culture systems and production researches However, because of deficiency of natural juveniles, the development was not remarkable Till the year 2000, prawn culture has continuous increased when problems about hatchery were solved Artificial juvenile was the significant point in development of culturing prawn Before the year 1998, yearly total production of giant freshwater prawn was approximately 5,000 – 8,000 tons

(Hien et al., 1998) Up to the year 2010, total production of whole the nation

achieved 6,526 tons with total area was 8,189 hectare (Directorate of Fisheries, 2012), mostly from provinces in the Mekong Delta: An Giang, Can Tho, Dong Thap, with culture systems: culture in pond, orchard canal, culture

in the rice field and in pen

2.4 Production of GFWP in the Mekong Delta

The Mekong delta has long history in the farming of GFWP When the artificial juveniles became popular, farming prawn was begun development in whole the country, especially in the Mekong delta In the year 1999, from a few hatcheries in the area, it was increased to 91 hatcheries with yield at 76 million post larvae per year in the year 2003 (Phuong, 2004) along with the increasing of juveniles demand for farming The Mekong delta had 6,000 ha cultured prawn in the year 2005 with the productivity at 1,400 tons/year with many culture systems: extensive, semi – intensive, intensive combined with some models such as: prawn culture in the rice field, culture in irrigation canal, single culture in cage,… In the year 2006, total area in the Mekong delta for culturing giant freshwater prawn was 9,077 ha with yield at 9,514 tons (Sinh, 2008) mostly from provinces: Dong Thap, An Giang, Can Tho, Ben Tre with the advantages of water area and propitious environment from flooding season In which, Dong Thap and An Giang provinces are mostly known with rice – prawn farming model This model is the combination of traditional rice farming crop (Winter – Spring crop) and prawn farming in flooding period

Dong Thap is the province where has potential for aquaculture with 70,000 ha of rivers, canals, ponds, channels and rice fields In many years, aquaculture played an important role in development of province by exported aquacultural products and provided jobs Beside Tra catfish, GFWP is the

significant object that is heeded and has wide potential In the year 2008, prawn cultured area was 1,072 ha and production was 1,723 tons, compare with 745 ha and 1,120 tons in the year 2007 (DARD of Dong Thap, 2008, 2009) Also according to DARD (2011), in the year 2011, the province had 1,500 ha cultured prawn in rice field, mostly distributed at Lap Vo, Tam Nong and Cao Lanh districts with productivity approximately 1.2 – 1.5 tons/ha, some places achieved 1.8 tons/ha In the year 2012, expectedly, total area for culturing prawn will expand to 2,200 ha with production about 3,500 tons

Figure 2.3: Map of the Mekong delta with the study sites

(Source: START, 2009)

An Giang province also has long history of culture giant freshwater prawn along with other province in the Mekong delta According to Extension Center of An Giang, in the year 2001, farmers cultured prawn with stocking density 5 – 7 ind./m2 Production time was 7 months with yield of 800 – 1,500kg/ha in area of 209 ha and the total area was increased to 400 ha up to year 2011 (DARD of An Giang, 2012)

Although be a city, Can Tho used to have long time in develop aquaculture and GFWP is one of the important object However, prawn cultured area in Can Tho decreased in the past few years and cultured area

Study areas: An Giang, Dong Thap provicnes and Can Tho city

now is 57 hecter (2011) Farmers in Can Tho city was design farming prawn systems which its yield achieved at 0.8 – 1.2 tons/ha/crop and net income more 5 – 10 times than farming rice (DARD of Can Tho city, 2012)

2.5 Technical – financial aspects of farming giant freshwater prawn

The research of Khanh and Phuong (2006) presented that average harvest size of prawn was 43.5 g/inds after stocked 5 months from juveniles and 36.4 g/inds after stocked 6 months from post larvae Survival rate of prawn was 47.5% when stocked from juvenile and 55.5% when stocked from post larvae Yield of prawn was 686 kg/ha when cultured from juvenile and 1,169 kg/ha when cultured from post larvae Farming giant freshwater prawn

in orchard canal brought net income VND 14.3 mil./ha when cultured from juvenile and VND 41.4 mil./ha when cultured from post larvae

Long et al (2006) indicated that average harvest size of prawn was

35.5 g/inds., biggest size was 95 g/inds and smallest was 25 g/inds Survival rate of prawn cultured in ponds was in range of 16.8 – 26.3% Yield of prawn was in range of 1,600 – 3,364 kg/ha Net income from prawn cultured in ponds fluctuate from VND 32.6 – 82.8 mil./ha Rate of net income on total cost was in range of 28 – 62%

Viet et al (2006) presented the result that showed the size of ponds for

farming prawn was in range of 450 – 3,000 m2, farming period from April to October and the main juvenile source was artificial sources, contributed 63.3% number of farmers interviewed Survival rate of prawn was 23% (in range of 5 – 48%) and average yield was 592 kg/ha/crop (in range of 167 – 1,120 kg/ha/crop) Net income of farmers was VND 8.3 mil./ha/crop and B:C ratio (TR/TC) was 1.24 Only 77% number of farmers successful (net income from VND 1.4 – 49.8 mil./ha/crop) and 23% number of farmers lost (farmers lost VND 6.1 – 31.2 mil./ha/crop)

According to Trung et al (2008), average harvest size of prawn which

had stocked in rotation prawn – rice system from juveniles (case 1) was 62.4 g/inds and prawn stocked from post larvae (case 2) was 53.6 g/inds Survival rate and yield of prawn was 44.1% and 946 kg/ha in case 1 and 42.8% and 679 kg/ha in case 2, respectively Net income of farmers was VND 15.6 mil./ha in case 1 and VND 36.5 mil./ha in case 2

Phuong et al (2008) presented that average harvest size of prawn

cultured in rotation prawn – rice farming system was in range of 38.6 – 70.5 g/inds Survival rate of prawn in different stocking density was fluctuate from

29.4% – 50.9% and yield was in range of 534 – 1,519 kg/ha Highest yield achieved when stocked at the density of 10 inds./m2 and lowest at density 3 inds./m2 Net income increased along with increasing of stocking density and

in range of VND 17.4 – 49.9 mil./ha Rate of net income on total cost was from 0.69 to 1.03 time Stocking density at 6 inds./m2 brought better rate of NI/TC and need to be encouraged

The research of Sinh (2008) presented that there were 4 farming prawn systems in Mekong delta: rotation of prawn – rice in rice field which had ditches, rotation of prawn – rice in rice field which had not ditches, mono – prawn cultured in rice field and mono – prawn cultured in orchard canal Prawn was stocked directly at the size of PL13 – 15 in February – March and harvest after 6 months stocked Survival rate of farming prawn systems was 41.7% with yield 1.3 tons/ha/crop Net income from prawn was VND 58.2 mil./ha/crop and there were 72.8% number of farmers successful Rotation of praw – rice in rice field which had ditches farming system had lowest investment cost, yield and net income at medium and less risk, therefore, it was suitable for famers in the area

The research of Lan et al (2008) showed that stocked post larvae

prawn brought better technical – financial effective than juvenile Using snail

as home – made feed decreased feed cost for farming prawn

According to Long et al (2010), average harvest size of prawn after 6

months stocked was in range of 56.4 – 67.1 g/inds and survival rate at 32 – 35% Yield of farming prawn was in range from 2,056 – 2,906 kg/ha and net income fluctuated in range of VND 49.12 – 87.12 mil./ha/crop Rate of NI/TC was lowest at densiy 15 inds./m2 (31%) and different from density at 9 inds/.m2 (52%) and 12 inds./m2 (43%) Rotation of prawn – rice farming system with stocking density of prawn at 9 inds./m2 brought better survival rate, yield and rate of NI/TC than stocking at 12 and 15 inds./m2

Chapter 3 RESEARCH METHODOLOGY 3.1 Scope of the research

Location: research is conducted in An Giang, Dong Thap provinces

and Can Tho city

Time: from May to December 2012

Secondary data include:

- Total area culture

Connect with secondary data the number of samples have to be satisfied:

Table 3.1: Sample size in study areas (prawn farmers)

Prawn systems Sample size

(farmers)

Total prawn farmers in survey areas

Ratio sample/total (%)

System 1 Rotation of prawn –

Important variables for primary data collection are listed below:

a General information of farmers (name, age, sex, education level, information sources for farming)

b Technical aspect for prawn culture:

- Harvest and consumption market (harvesting methods, harvesting time, survival rate, size classification and prices,…)

- Awareness of farmers ( about using low price aquaculture product

as live food, reasons for farming prawn, factors effect on farming prawn in rice field, advantages and disadvantages when farming prawn)

c Technical aspects for rice farming:

- Crops in year (Winter – Spring, Summer – Autum,….)

- Seed used

- Cost per crop

- Yield

- Price at each crop

- Awareness of farmers (effects of farming prawn on farming rice about renovation, seed quantity, fuel quantity, chemical quantity,…)

d Financial aspects:

Fixed costs:

- Rent/taxes cost (for field, for production)

- Construction cost (digging and sewers)

- Depreciation (depend on using time of each farmer)

o Tools cost (net, stakes, vehicles, boats)

o Storages cost (for guarding fields, tools maintenance)

o Machines cost (pump) Variable cost:

- Renovating cost (for liming, fertilizing, digging)

- Juvenile cost

- Feed cost (commercial and live food)

- Drug and chemical cost (drug and chemical using during farming prawn period to preventing or treating diseases)

- Miscellaneous

Total revenue (from farming prawn, rice and other activities)

Profit (from farming prawn, rice and other activities)

Monthly activities cost for farmer‟s family (for education, food, clothes, electricity, water,…)

Other perceptions:

- Aquaculture species suitable for farming in the area (technical application, product consuming, employment, effect on environment)

- Reason for not farming prawn

- Conditions for apply farming prawn

3.3 Data analysis

Primary data collected had been checked, added and coded before entered into computer

For specific objective (1), to describe the farming systems of giant

freshwater prawn in the rice field, descriptive statistics, multiple choice analysis and cross – tabulation analysis were used

- Descriptive statistics: mean, standard deviation, variance, range, min, max, median, count and standard error were calculated with important variables collected from such as: stocking density, water level, juveniles size, feed quantity, feed , harvest size, productivity, culture period, and survival rate

- Multiple choice analysis: for questions renovation methods, water source and preventing/treating diseases methods, each answer was coded and added point or counted for the frequency to calculate and represent farmers‟ ideal

- Cross – tabulation analysis: for the comparison of variables by different systems

For specific objective (2), to analyse economic aspects of the farming

systems and farmers‟ perceptions on farming giant freshwater prawn, data from open questions were entered into computer and also were analyzed by descriptive statistics method, cross – tabulation analysis with the same formulas above but different variable and matching method to measuring farmers‟ perceptions

- Descriptive statistics: fixed and variable costs, revenue and profit

- Cross – tabulation analysis: price and revenue, profit and revenue,…

For specific objective (3), to compare technical-economic efficiency

between these farming systems and farmers‟ perceptions, analyses for

objective (1) and (2) were used to get the objective

The software of Microsoft Excel was used for data entry, cacultate, check and match the answers Multiple choice analysis, descriptive statistic and cross – tabulation analysis were performed by SPSS for Windows Microsoft Word was used for preparing the questionnaires and writing the thesis

Chapter 4 RESULTS AND DISCUSSIONS 4.1 General information

Prawn farmers were different in ages ranging from 25 to 76 years old with the average age was 46.3±10.4 years Because of characteristics of farming, through 146 farmers interviewed, nearly all economics director of farms were male (99.3%), only one situation was female (0.7%)

Education level of prawn farmers was quite low with 48.6% the number

of farmers stopped at primary school while no farmers got education level higher than high school Among 4 systems, the farmers operating system 1 and

4 had higher rate of farmers got secondary school level, but system 1 and 2 got high school level at higher rate than the others

Only 8.9% of interviewed prawn farmers got technical training on rice farming, the remaining (91.1%) did not get any technical trainning It presents that farmers cultivate rice mostly based on their experience However, in the case of farming prawn, 86.3% of prawn farmers got training and 13.7% did not Beside, technical farming level of each system was not the same, especially for system 1, only 41.9% of farmers applied that system often got training while almost farmers applied others systems (97.2% of farmers applied system 2, 100% of farmers applied system 3 and 4) attended training

It means that the farmers applied system 1 farming more based on their experience than got training course while the farmers applied system 2, 3 and

4 more based on technical information from training courses It could be explained by the experience of prawn farming below

Average experience of farming rice of prawn farmers was 24.2±9.4 years because farming rice was a traditional farming However, the average experience of prawn farming was 6.1 year, presenting that the farmers have started to culture prawn recently and longest time was of system 1 with 7.5±2.7 years That was the reason why farmers in system 1 had lowest rate taking training than the others, their farming based on their experience

Prawn farmers abtained information for farming from different sources: experiment (100%), trainings (95.9%), others farmers (63.7%), books or journals (53.4%) and TV or radio (10.3%) Although only 41.9% of the farmers in system 1 often enjoyed trainings, 93.6% of farmers applied this system told that information from trainings helped their farming very much,

because they shared the information and experience with others farmers Therefore, with rate of using information sources from others farmers of 96.8%, the reason farmers told above was acceptable In addition, with highest education level, farmers applied system 1 had highest rate of using books or journals as farming information sources (96.8%) than the others (Appendix A.1)

4.2 Technical aspects:

4.2.1 Design farming systems

Flooding season in Mekong delta occur from May, June to November

or December and strongly effect on An Giang, Dong Thap, Long An and Can Tho province However, An Giang, Dong Thap and Can Tho province are the most giant freshwater prawn producers in the Mekong Delta There are 4 farming prawn systems there:

(1) Rotation of prawn – rice in closing dykes (system 1): this system

has one prawn crop in flooding season from March to October in Lunar calendar and one Winter – Spring crop in high dykes area Closing dykes means farmers design high dykes (about 2 m from the bottom) around the fields to limiting affect of flooding water on the fields

Figure 4.1: Rotation of prawn–rice in closing dykes (S1)

Thoai Son – An Giang province

(2) Rotation of prawn – rice in opening dykes (system 2): this

system has one prawn crop in flooding season from February to November in Lunar calendar and one Winter – Spring crop in low dykes area Opening

dykes means farmers did not design high dykes around the fields and flooding water could has strongly effect on farming areas Farmers use nets and pales to avoid prawns escape through flooding water

Figure 4.2: Rotation of prawn–rice in opening dykes (S2)

Tam Nong – Dong Thap province

(3) Mono prawn culture in closing dykes (system 3): this system has

only one prawn crop culture in closing dykes areas in flooding season from June to February in Lunar calendar in high dykes area

Figure 4.3: Mono-prawn culture in closing dykes (S3)

Cao Lanh – Dong Thap province

(4) Mono prawn culture in opening dykes (system 4): this system has

only one prawn crop culture in opening dykes areas in flooding season from March to November in Lunar calendar and one Winter – Spring crop in low dykes area

Figure 4.4: Mono-prawn culture in opening dykes (S4)

Tam Nong – Dong Thap province

4.2.2 Total land areas, prawn farming areas and construction

Total land areas of prawn culture households were quite large, around 2.8±2.9 hectare per farm with the largest area was system 4 and the smallest was system 3 It was also the case when compared about cultured prawn areas Only one farmer applied system 2 had area for culturing other aquatic species with more than 4 hectare Prawn farmers mainly used their land for farming prawn (2.71±2.87 ha) and rice (1.49±1.07 ha)

Because prawn farming activities are conducted in rainy season in flooding areas, almost prawn farmers used nets and poles to hold prawn in the fields (95.2%) Approximate 4.8% of the farmers (mainly in system 1 with 19.4%) did not use nets and poles because they cultured prawns in high dykes area In this case, they just prepared a few of nets and poles in order to prevent the bad cases of floods

Table 4.1: Farming areas of prawn farmers

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes

Table 4.2: Design of prawn farming areas

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes

Most of farmers designed culture areas with different input and output sewers (98.6%) and mostly made from ciment (64.4%) because it was the easy way to control water came in and out the fields Some farmers used plastic sewer (32.9%) because of longer using time, usually from 5 to 10 years Beside, 2.7% of prawn farmers used coconut tree bodies which were carved out the core as sewers because it were designed for farming rice in long time ago

4.2.3 Farming area preparation

Prawn farmers usually renovated the fields before getting water for stocking juvenile at the average was 18.1±8.5 days and in large range from 5

to 30 days and System 4 had longest renovation period with 20.9±7.1 days Renovation time at system 1 and system 2 were shorter than the others because their renovation time based on harvest period of rice Primary renovation methods were liming (100%), draining (100%) and dredging mud (63.7%) while few farmers used fertilizing methods (3.4%) In general, it presents that renovation for farming prawn was easy and did not have specific technical methods However, in system 1 and 2 with one rice crop of Winter – Spring, farmers used fertilizers (3.2% at system 1 and 5.6% at system 2) to create good environmental conditions for prawns because almost aquatic organisms in the fields were killed by chemical, pesticides or herbicides during the rice crop Despite of a low rate of application, this shows the awareness of farmers about environmental conditions of prawns

Table 4.3: Time and methods of field preparation

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes

4.2.4 Seed and stocking

100% number of prawn farmers used artificial PL in the last crop, mostly from local hatcheries (60.3%) and from hatcheries in other province in the delta (25.3%) It presented that technical level of hatcheries of survey areas was high and trusted by farmers Foreign seed sources such as the PL imported from Chines (11.0%) and Thailand (4.8%) were used by some farmers who had problems about PL in the previous crops (almost PL were dead after stocked 1 or 2 weeks and some cases got white muscle disease after 3 or 4 weeks) They believed that some hatcheries used broodstock for many

reproduction cycles causing a low quality of post larvae, therefore, they changed their PL sources

Post larvae were stocked at the average size of 84,287±9,926 inds./kg (PL8 – PL12) The average price of PL was VND 176.7±29.1 per inds., did not different too much between the systems System 3 with 100% of farmers used local sources which had lowest price (164.3±29.6 VND/inds.) Sytem 4 had highest average price at 195.5±30.5 VND/inds because highest ratio of farmers used more imported seed than others systems (22.7% farmers used the

PL from China and 18.2% farmers used the PL from Thailand) Lan et al

(2008) showed that using the PL brough more technical and financial effective than using juvenile (PL15) It presents that survey result of the research is reasonable

Table 4.4: Prawn seed

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes Means in the same line with the same characters are homogeneous with confidence level at 95%, used Duncan test

Prawn seed were stocked at the average stocking density was 13.1±4.0 inds./m2, ranging from 3 to 25 inds./m2 and System 3 and 4 had high stocking density at 14.2±4.6 inds./m2 and 14.4±2.7 inds./m2, respectively Through Duncan test with confidence level at 95% to compare stocking density of system 2, 3 and 4, it presented that the different was homogenous Only stocking density of system 1 (10.6±2.8 inds./m2) did not homogenous with the

others The research of Phuong et al (2008) showed that the stocking density

at 6 inds./m2 in rotation prawn – rice system brought best rate of net income

on total cost (NI/TC) and stocking density at 10 inds./m2 caused best yield In

addition, follow the research of Long et al (2010), stocking density at 9

inds./m2 in rotation prawn – rice systems brought best survival rate, yield and rate of NI/TC for farmers Therefore, it shows that the prawn farmers now stocking prawn at higher density than the recommendation because they have more condition to invest in technique than before with the expectation to get more profit

The quality of PL had checked before stocked mostly by looking external signs (91.8%) Through farmers‟ experience, It is said that good PL have to meet the conditions on same size, actively, from the same broodstock and all had survived after being transported to the fields With that way, 52.1% number of farmers evaluated that their PL were quite good, 46.6% number of farmers got normal quality and only 1.3% got really good quality

4.2.5 Feed and feeding management

Prawn farmers used feeding tray to control amount of feed in the field Through surveys, average amount of commercial feed (pellet feed) used was 2.40±1.01 tons/ha and amount of home – made feed, which mainly was snail uncovered, was 4.48 tons/ha, especially, farmers of system 3 did not use home – made feed The farmers of system 1 had the lowest amount of commercial feed, however, the amount of home – made feed was very high because they believed that the prawns consumed that feed more effective than commercial feed

FCR of the systems were different based on type of feed and the average FCR of 4 prawn farming systems was 3.2±2.1 Farmers of system 1 used the highest amount of home – made feed, caused the total amount of feed used highest That was the reason made the highest FCR in system 1 Through Table 4.6, the decreasing of FCR along with the decreasing amount of home – made feed and system 3 only used commercial feed had lowest FCR at

1.7±0.4 Follow the research of Lan et al (2008), FCR in rotation prawn – rice

system with both commercial feed and home – made feed was in range from 2.36±0.28 to 2.39±0.11 Although some farmers evaluated that home – made feed was better than commercial feed, using the home – made feed had strong effects on FCR for prawn culture

Table 4.5: Feed and feeding methods

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes

4.2.6 Water management

Water was exchanged mainly by both pump and tide (94.5% of farmers) with frequency was 1.26±1.60 times/day and ratio at 21.6±10.4% water level in the fields System 1 had the highest rate with 3.23±1.63 times/day with ratio at 34.5±11.2% water level The reason was system 1 had lowest water level with normal level at 94.2±12.1 cm and the highest water level was 157.1±19.7 cm and water became polluted faster than the others system The others systems had highest water level in range from 191.1±52.6

cm to 222.7±41.5 cm It presents that the exchange frequency based on the water level in fields and did not effected by stocking density

Oxygen is the most important living condition for aquatic species, however, through the farmers‟ experience, they cultured prawn at low density than other aquatic species, therefore, 26.7% of farmers chose this element to follow pH was the most important condition was mentioned by farmers with 95.9% of farmers and they also recognized more on toxic gases than oxygen with the rate was the number of 43.2% Farmers applied system 1 did not care about oxygen and toxic gases, because they exchange water with higher frequency and ratio than others systems Alkalinity (19.2%), temperature (9.6%) and water color (4.1%) also were mentioned as main living conditions have to follow to ensure prawn health

Table 4.6: Water management in farming period of GFWP

Description Unit System 1 System 2 System 3 System 4 Total

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes; used multiple choices question

4.2.7 Health management

Most of prawn farmers checked prawn health both day time along with feeding time and night time by walking around the field If there were any bad cases such as: prawn concentrated at the borders, prawn swam up to water surface (91.1% of farmers)

Table 4.7: Common diseases and effectiveness of treatment

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes; used multiple choices question

Followed that, the most common diseases prawn farmers had to face with was blackenning gills (69.2% of the answers) The next one with lower rate was white muscle disease (56.9%) which diagnosed the cause mostly from low quality post larvae Others diseases such as: fouling disease (18.5%), rising head (17.8%) and missing parts (17.8%) also be listed by farmers Farmers usually exchanged water and mixed Vitamin C into feed to cure while the prawns infected by diseases By these ways, prawn farmers got normal curing effectiveness at 57.5%, good and very good curing effectiveness only contributed 24.0% and 4.5%, respectively It presents that curing methods of prawn farmers were quite effective

4.2.8 Harvest

Female prawns were gradually harvested after stocking 130.3±34.3 days by net to decrease amount of feed and male prawn had space to growth All prawn was harvested after 7 – 8 month stocked in 12.0±5.5 times System

1 and 2 had shorter culture duration (184.2±8.5 days at system 1 and 211.9±25.3 days at system 2) also had less number of harvest time (8.3±4.8 and 12.2±5.6 times) in comparison with systems 3 and 4 (242.4±23.9 days with 15.6±4.3 times and 234.6±32.9 days with 13.3±3.8 times) because farmers had to conduct land preparation for Winter – Spring rice crop

Table 4.8: Harvest time

Note: System 1: rotation of prawn–rice in closing dykes; System 2: rotation of prawn–rice in opening

dykes; System 3: mono-prawn culture in closing dykes; and system 4: mono-prawn culture in opening dykes.