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 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:

freshwater

Technical and financial comparison of giant
prawn

(Macrobrachium

rosenbergii)

farming

systems in the flooding areas of the Mekong Delta.
NAME: Mr. Truong Thanh Lam
THIS THESIS HAS BEEN ACCEPTED BY
SUPERVISOR: ……………………………….

Ass. Prof. Dr. Le Xuan Sinh
COMITEE MEMBER: ………………………

Dr. Truong Hoang Minh
COMITEE MEMBER: ………………………

Dr. Tran Dac Dinh
APPROVED BY CAN THO UNIVERSITY ON: 16th January, 2013

DEAN: …………………………
Ass. Prof. Dr. Truong Quoc Phu

i


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 1st, Fisheries Economics Class Course 35th 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

ii

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 (2 nd 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

iii


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
iv


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

v


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

vi


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

vii

LIST OF ABBREVIATIONS
B/C:
DARD:
DOF:
Exp.:
GFWP :
Info.:
NI:
PL:
TC:
Tech.:
TR:
USD:
VND:

Benefit/cost
Department of Agriculture and Rural Development
Department of Fisheries
Experience
Giant freshwater prawn (Macrobrachium rosenbergii)
Information
Net income
Post larvae
Total cost
Technical
Total revenue
US Dollar
Vietnam Dong

viii


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


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.
Specific objectives
1. To describe the farming systems of prawn in the rice field in the
study areas;
2. To analyze technical and financial aspects of the farming systems
and farmers‟ perceptions on the farming of prawn; and
3. To propose a set of suggestion for better development of prawn in
both production and management to bring more benefit for farmers.

2


Chapter 2
LITERATURE REVIEW
2.1. Biological characteristics of Giant freshwater prawn
2.1.1 Classification

Figure 2.1: Apperance of Giant feshwater prawn

(Source: FAO, 2012)
Phylum:
Arthropoda
Class:
Crustacea
Order:
Decapoda
Family:
Palaemonidae
Genus:
Macrobrachium
Species:
Macrobrachium Rosenbergii
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;

3


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.

Distribution
Indo – West Pacific: India to Viet Nam, the Philippines, New Guinea
and Northern Australia.
2.1.2 Life cycle

Figure 2.2: Life cycle of giant freshwater prawn
(Source: Nandlal and Pickering, 2005)
GFWP regularly cast off their exoskeleton in order to grow, a process
known as molting. There are four distinct phases in their life cycle: egg, larva,
post larvae and adult. Adult prawn lives mostly in freshwater. Female prawn
that mated, migrate to estuary area (6 - 18‰) for hatching eggs. Larvae
hatched have to growth through 11 stages to become post larvae, that has

4


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
Characteristics
Size & head
2nd walking leg
Genital pores

Male

Female

Bigger
Big, spines
Between the base of the 5th
walking legs

Small, flat
Between the base of the 3rd
walking legs

(Source: Phuong et al., 2003)
2.1.4 Growth characteristics
Growth do not appear continuously in prawn, the animal have to
molting many to casts off the hard old shell, leaving the soft skin and allow the
prawn grow up. The frequency of molting depends on many factors: size (or
age) of prawn, food consumption and biological condition.
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
Protein
Lipid
Carbohyrate
Trace mineral
Calcium

Percentage in quantity of food (%)
27 – 35
< 10
40
2 – 19.5
3 – 5.3
(Source: Phuong et al., 2003)

5


2.1.6 Environmental condition
a. Temperature
The optimum temperature for almost stage of giant freshwater prawn is in
range of 26 – 310C. The best range is 28 – 300C. When temperature below
130C or higher than 380C, it can make prawn to die. Beside, high temperature
can make prawn mature sooner and smaller size in comparison with prawn
living in optimum temperature (Phuong et al., 2003).
b. Salinity
GFWP lives mostly in freshwater, however, larva stage requires the
salinity in range 6 -16‰ to growth and optimum is 10 - 12‰. In older stages,
giant freshwater prawn need salinity below 6‰. Juveniles and adult have the
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).
6


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
7


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.

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

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
8


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
9


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.

10


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
3.2. Material
Questionnaires, notebooks, pens, computer, phone, camera, books,
journals and reports were used during survey.
3.3. Data collection
3.3.1 Secondary data
Secondary data were collected from websites, reports or annual
publications of local office and reference which related to species and
researching area.
Secondary data include:
-

Total area culture
Yield
Productivity
Advantage and problem of culturing prawn
Development plans

3.3.2 Primary data

Primary data in 2011 were collected by interview farmers directly using
prepared questionnaires.
Beside with the interviewed prawn farmers, farmers farming rice in the
same areas were interviewed with the same number of sample about their
perceptions about farming prawn.
Connect with secondary data the number of samples have to be
satisfied:

11


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

System 1
System 2

System 3

System 4

Rotation of prawn –
rice in closing dykes
Rotation of prawn –
rice in opening
dykes
Mono – prawn
culture in closing
dykes
Mono – prawn

culture in opening
dykes
Total

Sample size
(farmers)

Total prawn
farmers in
survey areas

Ratio
sample/total
(%)

31

122

25

72

277

26

21

76

28

22

74

30

146

549

26

Therefore, total farmers interviewed (both prawn farmers and rice
farmers) was 292 farmers.
Technical and financial aspects were collected by questionnaires and
farmers‟ perceptions were asked by open questions or multiple choice
questions.
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:
-

Culture area (m2)
Renovating method (draining, liming or fertilizing, lime/fertilizers
quantity used, price,…)
Water source and water management (water source, farming water

level, exchange frequency,…)
Juveniles and stocking problems (number of juveniles, size, price,
time to stocking,…)
Feed and feeding methods (commercial feed quantity, live food
quantity, feeding times, feed maintenance,…)
Prawn health care management (common diseases, causes,
preventing and treating methods, efficiency,…)

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-

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,…)
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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.
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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.

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