Collaboration for Agriculture & Rural Development:" Development of clam culture for improvement and diversification of livelihoods of the poor coastal communities in Central Vietnam - MS04 " potx

1

Ministry of Agriculture & Rural Development

Collaboration for Agriculture & Rural Development
(CARD)









027/05VIE

Development of clam culture for improvement
and diversification of livelihoods of the poor
coastal communities in Central Vietnam

MS04: 2
nd
Six-Monthly Report





Oct, 2006 – Mar, 2007

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Table of Contents

1. Institute Information ___________________________________________________ 2
2. Project Abstract _______________________________________________________ 3
3. Executive Summary ____________________________________________________ 4
4. Introduction & Background _____________________________________________ 5
5. Progress to Date_______________________________________________________ 6
5.1 Implementation Highlights ________________________________________________ 6
5.1.1 Clam production (Grow-out trials) ________________________________________________6
5.1.2 Hatchery production __________________________________________________________22

5.2 Smallholder Benefits 22

5.2.1 Opportunity to utilize the brackish water ponds for clam production _____________________22
5.2.2 Increasing of production and benefit from clam culture in the intertidal areas ______________22
5.2.3 Easily Applicable Farming Knowledge____________________________________________22
5.2.4 Low Investment Risk__________________________________________________________22
5.2.5 Maximizing Commercial Potential through Knowledge_______________________________23
5.3 Capacity Building ______________________________________________________ 24
5.3.1 ARSINC ___________________________________________________________________24
5.3.2 End-users___________________________________________________________________24
5.3.3 Enhanced reputation and relation ship with other institutions and collaborators ____________24
5.3 Publicity ______________________________________________________________ 24
5.4 Project Management ____________________________________________________ 24
6. Report on Cross-Cutting Issues__________________________________________ 25
6.1 Environment Environment_______________________________________________ 25

6.2 Gender and Social Issues ________________________________________________ 25
7. Implementation & Sustainability Issues ___________________________________ 25
7.1 Issues and Constraints___________________________________________________ 25
7.2 Options _______________________________________________________________ 25
7.3 Sustainability __________________________________________________________ 25
8. Next Critical Steps ____________________________________________________ 25
9. Conclusion __________________________________________________________ 26
10. Statuatory Declaration_______________________________________________ 26

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1. Institute Information
Project Name
Development of clam culture for improvement
and diversification of livelihoods of the poor
coastal communities in Central Vietnam.
(Project No: 027/05VIE)
Vietnamese Institution
Aquaculture Research Sub-Institution for North
Central (ARSINC)
Vietnamese Project Team Leader
Mr. Nhu Van Can (Project Director)
Mr. Chu Chi Thiet (Project Manager)
Australian Organisation
South Australian Research and Development
Institution (SARDI)
Australian Personnel
Dr Martin S Kumar (Team Leader)
Dr Bennan Chen (Senior Scientist)
Date commenced
February 2006

Completion date (original)
February 2009
Completion date (revised)

Reporting period
November 2006, April 2007

Contact Officer(s)
In Australia: Team Leader
Name:
Dr Martin Kumar
Telephone:
08 82075 400
Position:
Principal Scientist, and Program
Leader,
Integrated Biosystems
Integrated Resource Management
and Biotechnology
Fax:
08 82075481
Organisation
South Australian Research and
Development Institution (SARDI)
Email:
kumar.martin@saug
ov.sa.gov.au

In Australia: Administrative contact
Name:

Telephone:

Position:

Fax:

Organisation

Email:


In Vietnam
Name:
Nhu Van Can
Telephone:
+84.383829884
Position:
Director
Fax:
+84.383829378
Organisation
Aquaculture Research Institute for
North-Central
Email:



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2. Project Abstract

3. Executive Summary
The.
The main objective of the project is to develop and extend the clam culture technology
(hatchery and husbandry) to sustain livelihoods of poor coastal farmers in the North
Central provinces and to develop a strategy which contributes to sustainable aquatic
environment management using clam aquaculture to improve prawn farm effluent
utilisation. Significant progress has been made in this section. Key findings are listed
below.
 Clam production can be successfully undertaken in ponds. Currently clam culture is
practiced in inter-tidal area.
 The preferred substrate for clam culture is clay-sandy
 The clam cultured at lower density (90 ind./m

2
) showed faster growth rate.
The size of clam determines the market price. Price of the clam greatly influences the
economics of the clam culture. Therefore, it is important consider the growth rate and the
culture duration available for each type of culture practice before deciding appropriate
stocking density and size of the clam for initial stocking. In relation to hatchery spat
production, a major upgrading of hatchery facility has been undertaken at ARSINC which
improved production of live feed clam larval rearing. Presently the facility provides stable
output of at least 4 marine algal species: Nanochloropsis, Isocrysis, Tetraselmis and
Chaetoceros and ready for next breeding season.

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3.1 Project Implementation Progress
3. 1.1 Key Highlights
Project progressed well during the first year and achieved specified milestones related
technology development in clam husbandry (production) and hatchery areas.
Following milestone reports submitted were reviewed and accepted.
 Socio-economic evaluation report
 First six monthly report
In accordance with the proposal the first year work was focussed on technology development
through adaptive research in hatchery and husbandry technology. The key highlights include:
 clam culture in ponds (production) experiments involving prawn farm effluent and
influent have been completed;
 clam and prawn polyculture experiments were completed;
 trial on clam culture in the inter-tidal has been just concluded and data analysis being
carried out; and
 experiments on clam cultured as alternative crop is also just concluded and data
analysis being carried out.
 hatchery infrastructure upgraded (including live feed production) for spat production
trials and trials are progressing well.

 training course including study tour in SARDI, Australia for key staff of ARSINC
and representatives of local government satff has been conducted.
In the second year, the work will be concentrated on farm trials, which fine tune the
technology and facilitate formulation of extension manuals. A Farmer selection criterion was
developed in consultation with lead farmers, village representatives and provincial
authorities. The details will be reported in the next report. In the third year, work will focus
on extension of technology including expanded farmer participated trials. Project impact will
also be assessed during the third year
3.1.2 Key outcome
a) Production experiments made excellent progress
Significant progress has been made in this component of the project. Results from production
experiment indicated that clam can be successfully cultured in ponds. The results also
provide suggestions for appropriate stocking density and substrata to maximize growth and
production of clam culture in ponds. Key findings are listed below.
 Clam production can be successfully undertaken in ponds. Currently clam culture is
practiced in inter-tidal area. Our experiments proved that clam culture could be expanded
and pond system could be utilised for successful operation.
 Clam can be cultured in three kind of substrate including clay, sandy and clay-sandy
substrate. However, the preferred substrate is clay-sandy especially in effluent pond
system.
 The clam cultured at lower density (90 ind./m
2
) showed faster growth rate compared to
higher density (120 ind./m
2
) in influent system. However, the growth of clam likely to be
same when cultured at the rate of 90 and 120 ind./m
2
.

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 The size of clam determines the market price. Price of the clam greatly influences the
economics of the clam culture. Therefore, it is important consider the growth rate and the
culture duration available for each type of culture practice before deciding appropriate
stocking density and size of the clam for initial stocking.
b) Upgrading facility and improve live feed production for hatchery production experiments.
Based on the previous results from hatchery experiments last year, and recommendation from
the first report, food and feeding ( algae) were regarded as major factor that might influence
the spat production (please refer to the 1
st
six monthly report). Effort on production of algae
resulted in stable output for at least 4 marine algal species: Nanochloropsis, Isocrysis,
Tetraselmis and Chaetoceros. Further more, the infrastructure for the spat production have
been improved and ready for the next breeding season.
Overall the project is progressing well as per the proposal.
4. Introduction & Background
A summary of the project objective, outputs expected and approach and methodology

The main objective is to develop and extend the clam culture technology (hatchery and
husbandry) to sustain livelihoods of poor coastal farmers in the North Central provinces; and
to develop a strategy which contributes to sustainable aquatic environment management
using clam aquaculture to improve prawn farm effluent utilisation. The aims of the proposed
project are:
a) to provide poor fisher community an alternative income, food security;
b) to improve technological and extension capacity for the stakeholders; and
c) to reduce negative impacts of shrimp culture through implementation of a strategy for
environmental management and waste utilisation of existing resources.
4.1. Specific objectives:
The objectives of this project (027/05VIE) include the following:
 to develop and extend the clam culture technology (hatchery and husbandry);

 to sustain livelihoods of poor coastal farmers in the North Central provinces; and
 to develop a strategy which contributes to sustainable aquatic environment management
using clam aquaculture to improve prawn farm effluent utilization.
4.2. Outputs Expected
In accordance with expected output proposed, the last six months were focused on following
aspects related to achieving the development of clam production technology. The log frame
reference is provided in the appendix A.
 Complete experiments of clam culture in the influent, effluent system and polyculture of
clam with shrimp in ponds
 Establish and operate the experiment on clam culture as alternative crop of shrimp culture
in ponds
 Establish and operate the experiment on clam culture in the inter-tidal areas
 Improve algae production for the next breeding season.
 Above mentioned activities were completed as per the proposed log frame.

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4.3. Methodology
The visits by Australian Project Leader and scientists (August 2006, December 2006 and
April 2007) enabled to undertake major review of the project methodology, implementation
strategy and resource and progress evaluation. Scientific approach has been refined for
implementing appropriate methodology for the experiments related to both clam husbandry
and hatchery. As a result of these steps (ref:1
st
six monthly report) , it was possible to
incorporate information from preliminary research results into the following experimental
design; clear scientific comparisons are possible; avoiding duplication of activities; and
efficient usage of resources.

5. Progress to Date
5.1 Implementation Highlights

Note: Detailed implementation progress is recorded in attached Progress Report Logframe.
This format is provided as a guide. The main purpose of progress reports is to report against
the achievement of the activities detailed in the project proposal logframe.
5.1.1

Clam production (Grow-out trials)
The research in pond culture type will be focused on suitability of substrate, optimum
stocking density, and stocking size. All experiments were conducted in triplicate. The
outcome of the experiments (culture types) will be used for the development of technical
guidelines for on farm trials in the second year. The clam production involved the following
5 types culture trials.
a) Clam culture using prawn farm influent water (reservoir): Clam culture will be
carried out as a pre- treatment for water intake in prawn farm- completed.
b) Clam culture using prawn farm effluent (effluent treatment pond). Clam farm will be
utilised as effluent treatment pond. The expected outcome is a good strategy on
management practices for shrimp ponds and clam culture- completed.
c) Shrimp and clam polyculture: Simultaneous culture of prawn and clams will be
undertaken with a view to improve farm water quality as well as generate additional
income- completed
d) Alternative/rotation crop: Clam culture will be under taken after the pawn harvest as
rotational – progressing well.
e) Clam culture in intertidal area: Inter tidal area will be divided into three zones based
on the tidal influence for clam culture- progressing well.
Trials related to a, b, and c are completed. Clam culture on inter-tidal area and prawn pond
(rotational/alternative crop) are progressing well.


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5.1.1.1 Experiment on clam culture in prawn farm influent and effluent
The main aim of this experiment is develop a method of clam culture in ponds using prawn

influent and effluent. The objectives of the trial are to:
 To determine suitable substrate for optimising the clam biomass( production)
 To determine optimum density for optimising the clam biomass (production)
Clam culture has been mainly carried out in the inter-tidal area. In order to develop and
expand clam culture as a viable farming industry it is necessary to develop pond culture
technology. There is also a need to transform the existing prawn farming to more
environmentally sustainable by utilising the effluent which causes aquatic pollution.




Materials and method
A pond culture system using effluent from prawn farm has been established for this
experiment for two treatments – bottom (substrate) and stocking density. The trial conducted
at Thanh Hoa Province included 18 ponds of 9 m
2
. 9 plots were used for bottom treatment:
sand bottom, clay-sand bottom and clay bottom with stocking density of 90 pieces/ m
2
in the
replication of 3. Other 9 sandy-bed ponds for treatment of density in the same replication
including: 90 clams/m
2
, 120 clams/m
2
and 150 clams/ m
2
.
A similar experimental design was used for influent water. Environment parameters such as
DO, water temperature, pH, N-NH

3
, turbidity as well as zoobenthod were periodically
monitored and registered. Clams were randomly sampled (30 individuals for each pond) for
growth evaluation. The experiments were terminated after 120 day rearing. All data of the
treatments were tested for significant differences (P<0.05) using One-way ANOVA followed
by Turkey test for multiple comparisons of means. The data are expressed as Mean ± SD and
statistical analysed was performed using Graphpad Prism version 4.0 and Microsoft Office
EXCEL. Specific growth rated were calculated using following formula, SGR=100*Ln(W)-
Ln(Wo)/t where W is the final weight, Wo is the stocking weight and t is the experimental
duration (day). It is similar calculation to the case of length.

Results and discussions
The result clearly indicated that the clay-sandy substrata produced higher survival rate and
total biomass compared to sandy or clay substrate (P<0.05). Clay –sandy is the preferred
substrate for clam(P<0.05). A detailed profile of the actual percentage of sand and clay and
physical characters are being gathered and will be provided in the next report. A mixture of
conditions prevailing in sand and clay may allow optimum moisture, air and produce unique
ecological condition provides optimum environmental conditions for clam survival and
growth ( Table 1 and Figure 3: a, b,c&d).

Fig 1 Effluent pond system
Fig 2 Influent pond system

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Table1. Survival and biomass of clam cultured in different substrata

Substrata
Water system
Sand
Clay

Clay-sand
Effluent
Survival (%)
63.00±2.64
54.33±5.50
71.00±6.56
Biomas (kg/m
2
)
0.75±0.07
0.79±0.02
1.25±0.14
Influent
Survival (%)
56.50±3.54
51.67±4.72
71.33±4.93
Biomas (kg/m
2
)
0.69±0.04
0.64±0.02
0.81±0.05

Fig 3 ( a,b,c &d) : Showing Survival and biomass of clam cultured in different substrata



It is interesting to note that the survival rate in the effluent used pond was not affected by the
rearing density. However, in the case of influent used ponds the survival rate of clam was
significantly higher. A comparative account of clam survival rate and total biomass related
to above treatment are given in table 2 and fig 4:a-d.
Sand
Clay
Clay-sand
0

10
20
30
40
50
60
70
80
a,b
a
b
Survival rate of clam cultured in effluent system
in different substrata
Survival (%)

Sand
Clay
Clay-sand
0
10
20
30
40
50
60
70
80
a
a
b

Survival rate of clam cultured in influent system
in different substrata
survival (%)

Sand
Clay
Clay-sand
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
a
a
b
Biomass of clam cultured in influent system
Biomass (kg/m
2
)

Sand
Clay
Clay-sand
0.0
0.1
0.2

0.3
0.4
0.5
0.6
a,b
a
b
Biomass of clam cultured in effluent system
Biomass (kg/m
2
)

Fig 3:a
Fig 3:b
Fig 3:d
Fig 3:c

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Table 2. Survival and biomass of clam cultured in different densities

Density
(Ind./
m
2
)
Water system
90
120
150
Effluent

Survival (%)
75.00 ±2.64
63.67±5.51
75.67±4.51
Biomas (kg/m
2
)
0.75±0.07
0.79±0.02
1.25±0.14
Influent
Survival (%)
65.33±3.40
49.33±3.05
50.00±1.73
Biomas (kg/m
2
)
0.69±0.04
0.64±0.02
0.81±0.05

Fig 4: (a,b,c &d) showing survival and biomass of clam cultured in different densities



It was clear from the trials that effluent used pond systems produced higher survival rate and
biomass (P<0.05). A comprson of the results obtained from influent and effluent system is
presented in fig 5(a-f). Based on previous studies the total nitrogen level was maintained 1.5
ppm ± 0.5 ppm using normal seas water to prevent any toxic ( unionised ammonia level) in
the pond. This allowed more algal production 10 to 15% in effluent pond. Therefore
comparatively better environmental conditions plus more food resulted in higher survival rate
and total biomass.
90
120

150
0.0
0.5
1.0
1.5
ind./m
2
a
a
b
Biomass of clam cultured in effluent system
Biomass (kg/m
2
)

90
120
150
0.0
0.3
0.6
0.9
ind./m
2
a
a
b
Biomass of clam cultured in influent system
Biomass (kg/m
2

)

90
120
150
0
20
40
60
80
a
a
b
Ind./m
2
Survival rate of clam cultured in effluent system
Survival (%)

90
120
150
0
10
20
30
40
50
60
70
Ind./m

2
a
b
b
Survival rate of clam cultured in influent system
Survival (%)

Fig.4:a
Fig.4:b
Fig.4:d
Fig.4:c

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Fig.5 (a-f) showing the comparison of survival rates and biomass of clam cultured in effluent
and influent system
The environmental conditions of influent and effluent systems in particular, salinity,
temperature and turbidity did not way significantly. During experimental period of time, the
salinity and turbidity were widely fluctuated. The salinity fluctuated from 9%o (min) and
20%o (max) and the turbidity varied between 27 cm (min) & 57 cm (max). A detailed
environmental data analysis along with chlorophyll levels will be reported in the next report.

Effluent
Influent
0.0
0.3
0.6
0.9
a
a
Biomass of clam cultured at 90 ind./m
2
in different culture system
Biomass (kg/m
2
)

Effluent
Influent
0
10
20
30
40
50
60
70
80
a
b
Survival rate of clam cultured at 90 Ind./m
2

Survival (%)

Effluent
Influent
0
10
20
30
40
50
60
70
a
b
Survival rate of clam cultured at 120 Ind./m
2
Survival (%)

Effluent
Influent
0.0
0.3
0.6
0.9
a
b
Biomass of clam cultured at 120 ind./m
2
in different culture system
Biomass (kg/m

2
)

Effluent
Influent
0
10
20
30
40
50
60
70
80
90
a
b
Survival rate of clam cultured at 150 Ind./m
2
Survival (%)

Effluent
Influent
0.0
0.5
1.0
1.5
a
b
Biomass of clam cultured at 150 ind./m

2
in different culture system
Biomass (kg/m
2
)

Fig.5:a
Fig.5:b
Fig.5:c
Fig.5:e
Fig.5:d
Fig.5:f

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Average and specific growth performance of clam in the different treatments
This analysis has been done to understand average and specific growth performance under
different treatments. It may be noted that, in the case of the density of animal stocked and the
density finally harvested drastically changed due to mortality. In clam culture it is difficult to
determine actual mortality until final harvest. Therefore replacing died clams were
impossible. As explained in the comparative section, the survival rate in the effluent was
higher than influent system. Therefore, more number of clams were present compared to
same density in the influent. On an average 15% fewer animals survived in influent system.
This was certainly reflected in the growth performance of the clam. In general influent
system recorded marginally higher growth rate compared to effluent. However, effluent
system yielded more total biomass compared to influent system (P<0.05). In general high
growth rate was recorded at lower stocking density. The maximum growth rate was obtained
at a stocking density of 90 ind/m
2
.(table 3 and fig 6)

Table 3. Growth of clam cultured at different stocking densities in effluent and influent
system:

Treatment
Length

Weight
Effluent
Influent
Effluent
Influent
90 ind/m
2

25.21±1.43
25.74±1.28
11.05±1.22
12.03±1.32
120 ind/m
2

24.47±1.27
24.89±1.90
10.38±1.05
11.18±1.69
150 ind/m
2

24.87±1.38
24.32±1.54
11.00±1.27
10.48±1.31

Table 4. Specific growth rate of clam at different stocking density in effluent and influent
system:

Treatment
SGRL
SGRW
Effluent
Influent
Effluent
Influent
90 ind/m
2

0.38±0.04
0.39±0.03
1.77±0.04
1.15±0.03
120 ind/m
2

0.36±0.03
0.37±0.01
1.75±0.03
1.09±0.02
150 ind/m

2

0.37±0.04
0.35±0.02
1.76±0.04
1.04±0.03













A key outcome of this analysis indicated that the effluent used pond the stocking densiy of
90
120
150
8
9
10
11
12
13
14

a
a
a
indiv./m
2
Figure 1. Weight of clam cultured in effluent water at different density
Gram

90
120
150
0
1
2
a
a
a
indiv./m
2
Figure 2. SGRW of clam cultured in effluent
at different stocking density
%/day

Fig.6 a
Fig.6 b

13
150 ind/m
2
was still not be the upper barrier for growth performance among the three

different densities and it seem more beneficial for farmers to stock at such high density as
they can get higher production with comparative same price of land lease and other operation
cost except the cost of seed stock. That means a properly managed effluent pond could be
used for high density clam production. However, there is further work needed
 to determine the upper limit in terms of higher stocking density
 to determine the suitable nutrient load ( total nitrogen) in the effluent pond for optimising
the production also require further studies.
Present investigation relied on nutrient levels on aquaculture on the information from the
studies conducted in freshwater polyculture ( ACIAR project) and integrated wastewater
treatment and aquaculture production information.

Table 5. Growth of clam cultured at different substrata in effluent and influent water system:

Treatment
Length
Weight
Effluent
Influent
Effluent
Influent
Sand
25.09±1.47
24.88±1.44
7.17±0.56
11.35±1.39
Clay
24.71±1.21
24.81±1.62
6.70±0.55
11.48±1.25

Clay-sand
26.24±0.83
25.70±1.02
7.26±0.44
11.45±1.08

Table 6. Specific growth rate of clam cultured at different substrata in effluent and influent
water system:

Treatment
SGRL
SGRW
Effluent
Influent
Effluent
Influent
Sand
0.38±0.01
0.37±0.01
0.72±0.01
1.10±0.02
Clay
0.36±0.03
0.36±0.05
0.66±0.06
1.11±0.08
Clay-sand
0.41±0.06
0.40±0.02
0.73±0.07

1.11±0.05

Unlike effluent ponds, the influent pond treatment, the results of the substrate impact were
not clear. However, density impact was evident in both influent and effluent treatments as
lower density produced higher growth rate. Therefore stocking density is an important factor
to obtain marketable size at desired time. Size is an important factor which determines the
price. Since there is significantly higher mortality rate recorded in influent treatment,
compared to effluent ponds, the relatively low number of animals impacted the substrate
factor in the influent treatment. The final weight of clam cultured in the influent was
significant higher than that of cultured in the effluent when stocked at 90 & 120 ind./m
2
(P<0.05, fig.7 a-f). However, at high stocking density of 150inds/m
2
, there were no
significant difference between the two treatments (P>0.05).

14

Fig.7 (a-f) showing average and specific growth rate in different substrata.

Sand
Clay
Clay-sand
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
a
a
a
Figure 4. SGRW of clam cultured in effluent
on different substrata
%/day

Sand
Clay
Clay-sand
5.5
6.0
6.5
7.0

7.5
8.0
8.5
a
a
b
Figure 3. Weight of clam cultured in effluent
on different substrata
gram

90
120
150
7.5
10.0
12.5
15.0
a
b
a,b
indiv./m
2
Figure 5. Weight of clam cultured in influent at different density
Gram

90
120
150
0.00
0.25

0.50
0.75
1.00
1.25
indiv./m
2
a
a,b
b
Figure 6. SGRW of clam cultured in influent
at different stocking density
%/day

Sand
Clay
Clay-sand
8
9
10
11
12
13
14
a
a
a
Figure 7. Weight of clam cultured in influent
on different substrata
Gram

Sand
Clay
Clay-sand
0.00
0.25
0.50
0.75
1.00
1.25
a
a
a
Figure 8. SGRW of clam cultured in influent
on different substrata
%/day

Fig.7 a
Fig.7 f
Fig.7 d
Fig.7 a
Fig.7 b
Fig.7 c

15

Fig.8: a-f showing comparison of final weight of clam cultured in effluent and influent
system in different substrate and density

5.1.1.2. Experiment on polyculture of clam and shrimp in brackishwater ponds
The key objective of this trial was to develop clam husbandry technology for poly culture
with prawn. Since a number of other experiments concentrated on optimum size and suitable
substrate, in this experiment the focus was on optimum stocking density without altering
current prawn stocking procedure.

Materials and method
In this experiment, clam was integrated with shrimp in brackishwater at different stocking
density of clam: 60; 90 and 120 clams/m
2
with 3 replication for each density level accounting
a total 9 plots. Water quality parameters such as temp, DO, pH, turbidity, conductivity will
Influent
Efluent
7.5
10.0
12.5
15.0
a
b
Figure 9. Weight of clam cultured
at stocking density of 90 ind./m
2
Gram

Influent

Efluent
7.5
10.0
12.5
15.0
a
b
Figure 10. Weight of clam cultured
at stocking density of 120 ind./m
2
Gram

Influent
Effluent
8
9
10
11
12
13
14
a
a
Figure 11. Weight of clam cultured
at stocking density of 150 ind./m
2
Gram

Influent
Effluent

5
6
7
8
9
10
11
12
13
14
a
b
Figure 12. Weight clam cultured in sandy pond
Gram

Influent
Effluent
5
6
7
8
9
10
11
12
13
14
a
b
Figure 13. Weight of clam cultured in clay substrate

Gram

Influent
Effluent
6
7
8
9
10
11
12
13
14
a
b
Figure 14. Weight of clam cultured in clay-sandy substrate
Gram

Fig.8 f
Fig.8 e
Fig.8 d
Fig.8 c
Fig.8 a
Fig.8 b

16
be monitored daily. The nutrient such as Total N, Ammonia NH
3
, Nitrate NO3, Total
Phosphorous and H

2
S will be monitored weekly. Biological parameters including
Phytoplankton (chlorophyll a) /L, Zooplankton /L, Zoobenthos no/m2 will be monitored
weekly. Clam were randomly sampled (30 inds for each pond) every 15 days for growth
evaluation. Experiment terminated after 105 days rearing. All data of the treatments were
tested for significant differences (P<0.05) using One-way ANOVA followed by Turkey test
for multiple comparisons of means. The data are expressed as Mean ± SD and statistical
analysed was performed using Graphpad Prism version 4.0 and Microsoft Office EXCEL.

Result and discussions
Clam growth rate including specific growth rate is presented in table 7 and fig.9 a &b. It was
clear from the table that clam growth was significantly higher in the 60ind/m
2
treatment
compared to 90ind/m
2
and 120ind/m
2
(P<0.05). However, the growth rates in 90ind/m
2
and
120ind/m
2
were not significantly different. Food and space availability may be the main
reason could be attributed to significantly higher growth rate in low stocking density.
Table 7. Growth of clam cultured in shrimp culture ponds in brackishwater (Mean ± SD)
Treatment
Length
Weight
SGRL

SGRW
60 ind/m2
26.20±0.62
7.58±0.37
0.47±0.01
0.88±0.01
90 ind/m2
24.86±0.59
6.99±0.35
0.42±0.02
0.80±0.02
120 ind/m2
23.93±0.60
6.80±0.26
0.39±0.03
0.77±0.05



The same result also reflected in the analysis undertaken to estimate survival rate (fig. 10 a).
Significantly higher survival rate recorded in 60ind/m
2
(P<0.05). However, the biomass rate
obviously higher in higher stocking density due more number of animals stocked (fig 10.b).
However, the average size of the animal is significantly smaller compared to higher stocking
densities.

60
90
120

6.0
6.5
7.0
7.5
8.0
8.5
a
b
b
Density
(ind./m
2
)
Figure 15. Weight of clam from polyculture
Gram

60
90
120
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Density

(ind./m
2
)
a
a,b
b
Figure 16. SGRW of clam from polyculture
gram

Fig.9 a
Fig.9 b

17
Table 8. Survival and biomass of clam cultured in shrimp culture

Density (Ind./m
2
)
60
90
120
Survival (%)
69.00±5.29
51.67±2.08
52.33±6.43
Biomas (kg/m
2
)
0.30±0.01
0.32±0.01

0.43±0.01















Fig.10 a: survival rate of clam in polyculture systems. Fig.10 b showing biomass of clam
cultured in polyculture system.

Comparison of final weight of clam cultured in effluent, influent and polyculture

Fig.11 (a&b) showing comparison of final weight of clam cultured in effluent, influent and
polyculture

A comparative analysis was made to understand the difference in growth performance in
different culture method. Figures 17and18 illustrated the difference in growth of clam
cultured in different culture systems. There were significant difference in final weight among
clam cultured in influent, effluent and shrimp cultured ponds (P<0.05). Figure 17a, 18a
shows that the final weights of clam were highest in the influent system and lowest in the
polyculture of clam with prawn ponds. The higher average weight in influent system could
be attributed to low number of survival in the effluent system compared to effluent ponds.
However, low growth rate in the polyculture with prawn could be attributed a number
60
90
120
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
a

a
b
ind./m
2
Biomass of clam cultured in shrimp culture ponds
Biomass (kg/m
2
)

60
90
120
0
25
50
75
a
b
b
Ind./m
2
Survival rate of clam cultured in shrimp culture ponds
Survival (%)

Fig.10 a
Fig.10 b
Influent
Efluent
Polyculture
5.0

7.5
10.0
12.5
15.0
a
b
c
Figure 17a. Weight of clam cultured
in different system at 90 ind/m
2
Gram

Influent
Efluent
Polyculture
5.0
7.5
10.0
12.5
15.0
a
b
c
Figure 18a. Weight of clam cultured
in different system at 120 ind/m
2
Gram

Fig.11 a
Fig.11 b

18
reasons including environmental conditions. In addition, the colour of clam cultured with
prawn look more dark compared to clam cultured in
the influent or effluent system (fig.12). Clam and
prawn are a bottom dwelling animals. Clam cultured
in shrimp cultured ponds might be disturbed by
shrimp activities. Furthermore, their activities might
reduce water transparency thereby reducing light
penetration which inturn can affect algal production.
which are regarded as mainly feed source for clam.
Another reason might affect the growth of clam in
shrimp culture ponds was the chemical used for water
treatment during shrimp culture period.
Fig.12 showing darker coloured clam cultured with prawn (polyculture).
A further comparison on the treatment at each density level for the three culture method
(influent water, effluent water and polyculture with prawn) showed a clear result (fig.13 (a-
d). The analysis indicated that at same density, survival rate and biomass were highest in the
effluent system followed by the influent system. The survival and biomass was relatively low
in the polyculture system.

Fig,13 ( a-d) showing comparison of survival rates and biomass of clam cultured in effluent,
influent and polyculture ponds


Effluent
Influent
Polyculture
0
10
20
30
40
50
60

70
80
a
b
c
Survival rate of clam cultured at 90 Ind./m
2
In different system
Survival (%)

Effluent
Influent
Polyculture
0
10
20
30
40
50
60
70
a
b
a,b
Survival rate of clam cultured at 120 Ind./m
2
In different system
Survival (%)

Effluent

Influent
Polyculture
0.0
0.3
0.6
0.9
a
a
b
Biomass of clam cultured at 90 ind./m
2
in different culture system
Biomass (kg/m
2
)

Effluent
Influent
Polyculture
0.0
0.3
0.6
0.9
a
b
c
Biomass of clam cultured at 120 ind./m
2
in different culture system
Biomass (kg/m

2
)

Fig.13c
Fig.13 a
Fig.13 b
Fig.13d

19
The conditions used in effluent pond appear to be more suitable for clam culture. It is
understandable that the effluent contains more nutrient ( (but well below the toxic level as the
nutrient content was maintained at below 1.5ppm N) than the others for algae to develop
which then becomes the main food for clam to grow. However, in the shrimp culture ponds,
the nutrient level could be high but comparatively low percentage of survival and low
biomass of clam suggested that the activities of shrimp might disturb the environment of
clams- shrimp is also a bottom feeders. In addition, the activities of shrimp might cause water
turbidity which is unsuitable for algae to develop due to lack of sunlight. A full detail of the
environmental report will be presented in the next report.

Conclusions
Following conclusion can be derived from the above trails.
 Clam production can be successfully undertaken in ponds. Currently clam culture is
practiced in intertidal area. Our experiments proved that clam culture could be expanded
and pond system could be utilised for successful operation.
 Clam can be cultured in three kind of substrate including clay, sandy and clay-sandy
substrate. However, the preferred substrate is clay-sandy especially in effluent pond
system.
 The clam cultured at lower density (90 ind./m
2
) showed faster growth rate compared to

higher density (120 ind./m
2
) in influent system. However, the growth of clam likely to be
same when cultured at the rate of 90 and 120 ind./m
2
.
 The size of clam determines the market price. Price of the clam greatly influences the
economics of the clam culture. Therefore, it is important to consider the growth rate and
the culture duration available for each type of culture practice before deciding appropriate
stocking density and size of the clam for initial stocking.

5.1.1.3. Experiment on clam culture in the inter-tidal areas
Traditional clam culture has been undertaken in the inter-tidal areas. The aim of this
experiment is to enhance the profitability of clam farmer. The key objective is to increase
productivity by determining the optimum stocking density. The other parameters within the
culture system can not be altered as it is a natural ecosystem highly connected to capture
fisheries which is one of the key industry for the fisher community.

Fig. 15 showing samples of clam
cultured in the inter-tidal system




Fig.14 showing intertidal clam culture monitoring.


20
Materials and method
The inter-tidal clam culture was undertaken in 24 plots of 50 m

2
each. Two sizes (1 cm and 2
cm) clams and 4 different densities: 60ind/m
2
, 120ind/m
2
, 240ind/m
2
and 360ind/m
2
were
used in these experiments. Culture duration of this experiment is 5 months and the.
completion date is May 2007. Presently this trial is progressing well. Final result will be
reported in the next report. In this report available information is included. Parameters
monitored include: the clam height, weight were measured fortnightly; temperature, DO, pH
of water were monitored daily at 3 designated points within the experimental area while
samples of water were analysed weekly for Total N, Total P, Ammonia and Nitrate.



Result

Figure shows the growth of the clams (for two starting sizes of 1 cm and 2 cm) over the
experimental period (7/12/06 – 7/3/07). Progressive results are presented in the figure to
The result, in particular the weight data showed that lower density treatment produced higher
average weight. Finla result will be included in the next report.

Growth of 1 cm Clam in Inter-tidal area, by Density
0
4
8
12
16
20
0 15 30 45 60 75 90 105
Culture period (days)
Clam Height (mm)
0
0.5
1
1.5
2
2.5
3
3.5
4
Clam Weight (g)
Weight 360/m2
Weight 240/m2
Weight 120/m2
Weight 60/m2
Height 360/m2
Height 240/m2
Height 120/m2
Height 60/m2

Fig 16. Growth data of 1 cm Clam cultured in an inter-tidal area at Thanh Hoa




21
Growth of 2 cm Clam in Inter-tidal area, by Density
3
8
13
18
23
28
0 15 30 45 60 75 90 105
Culture period (days)
Clam Height (mm)
0
2
4
6
8
10
Clam Weight (g)
Weight 360/m2
Weight 240/m2
Weight 120/m2
Weight 60/m2
Height 360/m2
Height 240/m2
Height 120/m2

Height 60/m2

Fig 17. Growth data of 2 cm Clam cultured in an inter-tidal area at Thanh Hoa

Figure Clam height to weight ratio during growth in inter-tidal area (starting with 2 cm high
clam)

5.1.1.4. Experiment on rotational culture of clam
Prawn farming in Central Vietnam normally occurs in April to September each year; the
rotation clam culture has to wait until September. Clam rotational culture is possible in
prawn farms between October and March.
The aim of this trial is to evaluate the
feasibility of an alternative clam crop in
prawn farms during October to March.
Based on the results from the other three
experiments (polyculture, clam culture in
effluent and clam culture in influent)
suitable substrata (sand bottom) and density
of 60ind/m
2
were selected from the existing
prawn farm. This experiment focused to
determine suitable stocking size for the
rotational culture of clam of which the two
sizes (2 cm, 3cm) clams were tested.
Materials and method
Two sizes of clams (2cm and 3cm) stocked
at the rate of 60ind/m
2
conducted in prawn

ponds using 3 replicates. Water quality
parameters such as temp, DO, pH, turbidity,
conductivity are being monitored daily. The
nutrient such as total N, ammonia NH3,
nitrate NO3 and total phosphorous being
monitored weekly. Biological parameters
including chlorophyll a /L, Zooplankton /L,
Zoobenthos no/m2 are being monitored
weekly. Clam growth measurements such as
March
February
January
December
November
October
September
August
July
June
May
April
Clam culture period
Prawn culture period
March
February
January
December
November
October
September

August
July
June
May
April
Clam culture period
Prawn culture period
Fig. 18 Prawn and
clam culture cycle

22
weight (g) and size (mm) are being recorded every fortnightly. The experiment started
7/12/06 to 7/3/07 and finishing by end of April 07.

Results:
Rotation culture clam recored encouraging growth rate. Progressive results of the clam
rotational culture are presented in figures 19 &20.
Rotational culture of Clam in Prawn farm
(2 cm high Clam)
4
9
14
19
24
29
0 20 40 60 80 100
Culture Period (days)
Clam Height (mm)
0
2

4
6
8
10
Clam Weight (g)
Height
Weight


Fig19 Clam Growth (starting with 2 cm high clams) in Prawn farm effluent during post
harvest rotational culture in Than Hoa )


Rotational culture of Clam in Prawn farm
(3 cm high Clam)
11
16
21
26
31
36
0 20 40 60 80 100
Culture Period (days)
Clam Height (mm)
0
5
10
15
20
25

Clam Weight (g)
Height
Weight


Fig 20 Clam Growth (starting with 3 cm high clams) in Prawn farm effluent during post
harvest rotational culture in Thanh Hoa



23

5.1.2

Hatchery production
Clam breeding season is restricted to warmer climatic condition prevailing during May to
September. November to April is a winter time with low water temperature when the
reproductive process ceased. This six month period was focussed on the preparation
including infrastructure and live
feed ( morcoalgae) for the hatchery
spat production trials. This was
done in accordance with
recommendation reported in the
first six monthly report. With
regard to live feed production the
expansion of intensive system for
algae was focussed which resulted
in very stable production of 4 algal
species: Nanochloropsis, Isocrysis,
Tetraselmis and Chaetoceros. The

success of Chaetoceros production
regarded as the main key for
survival improvement of clam spat.

Fig. 21showing outdoor algal culture systems.

5.2 Smallholder Benefits
5.2.1 Opportunity to utilize the brackish water ponds for clam production
The success that clam can survive and grow in pond opens opportunity for farmers to utilize
the brackish water ponds where the shrimp industry recently has been collapsed due to bad
management.

Success of clam culture as alternative crop will provide new opportunity for the famers in to
utilise the prawm farm which normaly used only 4 months per year for shrimp culture
5.2.2 Increasing in production and benefit from clam culture in the intertidal areas
Appropriate stocking density and stocking size will provide higher productivity, reduce the
operation cost and bring in higher benefit.
5.2.3 Easily Applicable Farming Knowledge
Factors such as stocking density and salinity are within the capabilities of smallholder end-
users to monitor and manipulate. By focusing upon the research and understanding of the
impact of such factors on survival and growth of M lyrata and its larvae, the teams at
ARSINC are building the knowledge base for farming practices that can be applied by
smallholders.
5.2.4 Low Investment Risk
The focus on low-cost, reliable production and hatchery techniques and infrastructure
provide for low investment risk to the smallholder and smallholder communities.


24
5.2.5 Maximizing Commercial Potential through Knowledge

The following table summarizes the implications of the knowledge generated by this project
for the smallholder’s commercial production potential

Table . Technology Implications for M lyrata Commercial Production
Farming
Component
Knowledge
Implications for Commercial Production
Production
Density
 Farmers need to know optimum stocking density
that provide for maximum productivity per m
2

pond area

Substrate
 Farmers need to know which sediment substrate
clam can be grown on as this may affect farmers
of different regions where there is different soil
type

Influent / Effluent /
Polyculture Pond
System
 An influent pond system may be useful for water
treatment prior to prawn culture use in places
where water quality is not good enough for
prawn culture.
 An effluent pond system may be useful for

prawn culture to reduce pollution and enable
more sustainable prawn culture
 A combination of both pond systems
(polyculture) would be useful to supplement
farmer income (both prawn and clam) as well as
provide for sustainable aquaculture and/or bio-
remediation of prawn farming areas
Hatchery
Spat Production
Technology for M
lyrata clam culture
 Easy to use, low-cost indigenous (developed by
ARSINC) system that can be implemented on
farms or in regional cooperatives
 Reduce collection of spats from wild so as to
reduce ecological impact along Vietnam
coastline
Hatchery /
Broodstock
Conditioning
Algae feed
composition
 Enable hatcheries and regional cooperatives to
culture feedstocks (using pure cultures from
ARSINC and other government suppliers) for
hatcheries to use in their spat production
 Enable farmers to create their own broodstock
Hatchery /
Larvae Rearing
Stocking density

survival / growth
rates
 Enable regional hatcheries to achieve optimal
larvae rearing productivity

Salinity survival /
growth rates
 Enable regional hatcheries to achieve optimal
larvae rearing productivity, controlling salinity if
necessary

Stocking density
Days to Settlement
 Enable regional hatcheries to know how many
production cycles can be achieved per season
and how to increase frequency of spat production
Breeding /
Spawning
Breeding /
Spawning
Inducement Factors
 Enable regional hatcheries to know what factors
induce breeding and spawning, that can be

25
controlled by the hatchery

5.3 Capacity Building
5.3.1 ARSINC
At least 6 technical staff directly involved in the project activities have opportunities to

improve their knowledge, experience in both hatchery and grow out production of clam
culture

Researchers of ARSINC involved in this project have chance to approach updated research
methodology and gain more experience in research, design, implementation and reporting as
well as international communication.

Three technicians from ARSINC and 1 tecnician from Thanh hoa province have been sent to
SARDI for training course on live feed production, data processing, nutrientand water quality
management. Also integrated aquaculture system was demonstrated using waste water.

There were 2 students from University of Vinh have done their thesis on clam hatchery
production under ARSINC supervision. At the momment, they have been successfully
depended their BSc thesis and one of them achieved excilent results and was selected to be a
lecturer of the University. This year, two more students from Vinh University have been
selected to do their thesis on clam under the project and 2 lecturers from Vinh University
have proposed their MSc thesis on hatchery production of clam under supervision of
ARSINC
5.3.2 End-users
Due to this being the first research phase of the project, several farmers at the experimental
site were hired and trained for research activities participation
5.3.3 Enhanced reputation and relation ship with other institutions and collaborators
The project activities have been well introduced and have good comments from scientific
committee of ARSINC. This accelerates collaboration and contribution from other projects
implementing within ARSINC and RIA1 eg NORAD funded project and AIDA project
5.4 Publicity
Research papers will be prepared for Asian Fisheries Forum held at Cochin, on November
2007. Also articles will be prepared for CARD newsletter.
5.5 Project Management
Some staff from ARSINC will be leaving for higher studies. They will be replaced with

appropriately qualified researchers. There are no other issues to report on project
management.