Project Progress Report:" Development of clam culture for improvement and diversification of livelihoods of the poor coastal communities in Central Vietnam - MS04 " pptx

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: 4
th
Six-Monthly Report

November 2007 to April 2008













1


2
Table of Contents
1. Institute Information 5
2. Contact Officer(s) 5
3. Project Abstract 6
4. Executive Summary 6
3. Project Implementation Progress 7
3.1. Key Highlights 7

3.2. Key outcome 7
4. Introduction & Background 7
4.1. Specific objectives 8
4.2. Outputs 8
5. Progress to Date 8
Implementation Highlights 8
5.1.1 Workshop to formalise the collaboration for ‘on farm’ trials 8
5.1.2 Expression of interest and feedback from farmers 17
5.1.3.Study tour 19
5. 2 Revised experiment on larval rearing. 23
5.2.1. Experiment 1: 23
Method 23
5.2.2 Experiment 2 26
5.2.3 Experiment 3 28
5.2.4 Discussion and conclusion 30
5.3 Propagation of the technologies (on farm trials level) 31
5.4 Smallholder Benefits 31
5.4.1 Opportunity to utilize the brackish water ponds for clam production 31
5.4.2 Increasing in production and benefit from clam culture in the intertidal areas32
5.5.3 Easily Applicable Farming Knowledge 32
5.4.4 Low Investment Risk 32
5.4.5 Maximizing Commercial Potential through Knowledge 32
5.5.Capacity Building 33
5.5.1. ARSINC 33
5.5.2. End-users 34
5.5.3. Enhanced reputation and relation ship with other institutions and collaborators
34
5.6. Publicity 34
5.7. Project Management 34
6. Report on Cross-Cutting Issues 34

6.1.Environment 34
6.2.Gender and Social Issues 34
7. Implementation & Sustainability Issues 35
7.1. Issues and Constraints 35
7.2.Options 35
7.3.Sustainability 35

3
8. Next Critical Steps 35
9. Conclusion 35
10. Statutory Declaration 35

4

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. Chu Chi Thiet (Project Director)
Ms. Le Thi Tinh (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 2007, April 2008
2. 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@saugov.
sa.gov.au
In Australia: Administrative contact
Name:

Telephone:

Position:

Fax:

Organisation

Email:


In Vietnam
Name:
Chu Chi Thiet
Telephone:
+84.383829884
Position:
Director
Fax:
+84.383829378
Organisation
Aquaculture Research Institute
for North-Central
Email:


5
3. Project Abstract

Last sixmont








4. 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. In the last six months, the focus of the project implementation is concentrated
in the following two aspects. (1) Preparing and facilitating the agreements between the
stakeholders and research institutions in order to undertake ‘on farm’ trials. (2) A revised
experiment on larval rearing was conducted to fine tune the larval rearing technique.
Details of these activities are reported in this report.
A hatchery manual was prepared and submitted
The preparation for the coordinating the ‘on farm’ trials included, a major workshop and
study tour. The detail of the workshop and study tour is included in this report.
Agreements with stakeholders were completed and the work associated with ‘on farm’
trials will start from May 2008

6
3. Project Implementation Progress
3.1. Key Highlights
Project progressed well in accordance with specified milestone. The focus of the project
during the last six months was to prepare the farmers and associated partners to
participate in the on farm trials and fine tuning the larval rearing technique. Key
activities include:

- Workshop on farmer participated on farm trials.
- Development of operational protocol for on farm trails

- Production of required number of spats: experiments on fine tuning clam larval
rearing and spat in hatchery
- Extension and trainings including in country study tour

3.2. Key outcome
The workshop was well received by the farmers, extension department and local
government officials and others who are associated with clam farming. The farmers,
expressed interest on participating in demonstration trials to be conducted in six
provinces. Based on the selection criteria, 6 farmers from each province have been
selected for the demonstration. A total of 36 lead farmers were selected for the trials
which would start in the month of May 2008.

There two larval rearing experiments are currently being conducted to fine tune and
enhance the survival rate of clam larvae. The spat production results were encouraging.
The details are included in this report.

A successful study tour was undertaken to understand the natural nursery areas (These
areas are known to be clam breeding and spawning locations) of clam and wiled spat
collection centers. A workshop was conducted to introduce the farmers in pond culture
practice. Traditionally these farmers are collecting spats from wild and culturing the
clam in inertial areas. A formal agreement with local extension departments, farmers and
ARSINC were finalized during this trip.

4. Introduction & Background
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

7
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
In accordance with expected output proposed, the last six months were focused on
following aspects related on the following
- Workshops conducted on farmer participated on farm trials.
- Developed operational protocol and agreements with farmers and local extension
department for on farm trails
- Produced and supplied required number of spats
- Completed the experiments on fine tuning clam larval rearing and spat in hatchery
- Undertaken extension and trainings including in country study tour
The visits by Australian Project Leader in November 2008 and April 2009 facilitated
• Selection farmers for on farm trials
• Conducting the workshop with stakeholders for transfer of technology
• Initiating the on farm clam production trials
• Establishing new clam hatcheries
• Evaluating the results revised larval rearing

5. Progress to Date

Implementation Highlights
5.1.1 Workshop to formalise the collaboration for ‘on farm’ trials.

In order to formalise the farmer participated on farm trials, a workshop was held at Giao
Te Hotel in Cua Lo Town, Nghe An Province from 28-28 March 2008.

Objective of the workshop was to formally introduce the clam production technology and
explain the operational procedure for on farm trials. Participants of the workshop
included Leader of the project from Australia and Project team from ARSINC, provincial

8
officers from local fisheries department, and farmers who interested in participating clam
culture from 6 North Centre provinces.

The content of workshop:
a. Introduction of the workshop:
i. Purpose of the workshop
ii. Expected out of this workshop
b. Introduction of the project and requirements for on-farm trials
i. Introduction of project
ii. Structure of farmer participated trial
iii. Role of farmer
iv. Role of ARSINC and collaborator
v. Farmer selection criteria
vi. Operational protocol
vii. Reporting requirements
viii. Feed back opportunity
c. Technical lectures
i. Inter tidal clam culture
1. site and seed selection and stocking size and density

2. monitoring
ii. Pond clam culture
1. site and seed selection
2. stocking size and density
3. monitoring
4. pond and water management
iii. Rotational culture of clam in prawn ponds
1. stocking size and density
2. monitoring
3. Pond management
iv. Data collection
1. structure of data sheet
2. parameters collected
3. frequency of data collection
v. culture techniques, husbandry guideline, data collection forms
d. Discussions: Participants
e. Program for on-farm trials
f. Closing session

Key presentation following:

1. Introduction of the workshop


9

2. Presentation of Introduction of the project and requirements for on-farm trials


10
ARSINC
Workshop
Clam Production:
Farmer participated Field Trial
Introduction of the Project and
Requirements for On-farm Trials








3. Lecture of clam culture technology
- Clam culture in pond


11



Pond selection

Pond selection
•
•
Site: pond located at high
Site: pond located at high
tidal to low tidal, which
tidal to low tidal, which
water supply available
water supply available
•
•
Substrata: clay
Substrata: clay
-
-
sandy
sandy
bottom (80% sand, 20%
bottom (80% sand, 20%
clay)
clay)
•
•
Salinity: range of 10
Salinity: range of 10
–
–
25
25
ppt

ppt
•
•
Pond should be avoided
Pond should be avoided
pollutants
pollutants

Pond preparation
Pond preparation
to apply prawn pond
to apply prawn pond
preparation:
preparation:
–
–
To dry bottom in 2
To dry bottom in 2
-
-
3
3
weeks
weeks
–
–
Liming: 7
Liming: 7
–
–

15
15
kg(CaO)/100 m
kg(CaO)/100 m
2
2
–
–
To eliminate predators
To eliminate predators
(crap, snail)
(crap, snail)

Seed selection
Seed selection
•
•
Clam species:
Clam species:
Meretrix
Meretrix
lyrata
lyrata
,
,
Sowerby
Sowerby
1851
1851
•

•
Seed size: 300
Seed size: 300
–
–
500
500
clams/kg
clams/kg
•
•
Seed source: from the
Seed source: from the
wild
wild


Monitoring and pond management
Monitoring and pond management
–
–
Algae production for
Algae production for
supply algae to clam
supply algae to clam
•
•
Fertilized: 150 g/m
Fertilized: 150 g/m
3

3
(NH
(NH
4
4
)
)
2
2
SO4: 76 g/m
SO4: 76 g/m
3
3
ure
ure
(NH
(NH
2
2
)
)
2
2
CO: 25
CO: 25
g/m
g/m
3
3
Superphotphat

Superphotphat
Calcium (CaHPO4)
Calcium (CaHPO4)
•
•
and 20kg Urea and
and 20kg Urea and
30kgNP/ha.
30kgNP/ha.


12





13



- Clam culture in intertidal



Site selection
Site selection
•
•
Intertidal zones from

Intertidal zones from
high tidal to sub
high tidal to sub
-
-
intertidal
intertidal
•
•
Site for culture need
Site for culture need
to avoid stagnant
to avoid stagnant
water
water
•
•
Salinity in range of 7
Salinity in range of 7
-
-
35 ppt.
35 ppt.



14
Site selection
Site selection
•

•
However, clam grow
However, clam grow
better from middle tidal
better from middle tidal
are to sub
are to sub
-
-
intertidal area,
intertidal area,
where is submerged in
where is submerged in
longer time everyday
longer time everyday
•
•
Substrata appropriate for
Substrata appropriate for
clam culture is clay
clam culture is clay
-
-
sandy
sandy
(20% clay, 80% sand)
(20% clay, 80% sand)

Site selection
Site selection

•
•
Places for nursing seed
Places for nursing seed
should out of the wind,
should out of the wind,
gently wave and clear
gently wave and clear
water
water
•
•
Substrata of nursery place
Substrata of nursery place
should clay
should clay
-
-
sandy (70
sandy (70
-
-
80%
80%
sand and 20
sand and 20
-
-
30% clay)
30% clay)

•
•
Salinity at 19
Salinity at 19
-
-
26
26
‰
‰
, and
, and
fresh water should supply.
fresh water should supply.

Culture area preparation
Culture area preparation
•
•
To plough and turn
To plough and turn
bottom before
bottom before
stocking seed;
stocking seed;
•
•
To dig small irrigators
To dig small irrigators
to dry surface of

to dry surface of
bottom during low
bottom during low
tidal period
tidal period

Culture area preparation
Culture area preparation
•
•
Using net (4
Using net (4
-
-
5 mm) to
5 mm) to
fend surround culture
fend surround culture
area with 0.6
area with 0.6
-
-
0.7 m
0.7 m
height, under ground
height, under ground
about 0.4
about 0.4
-
-

0.6 m.
0.6 m.
•
•
To set bamboo poles
To set bamboo poles
equal distance of 1.2
equal distance of 1.2
-
-
1.5
1.5
m and conjunct together
m and conjunct together
by nylon net.
by nylon net.

Culture area preparation
Culture area preparation
Culture areas should be
Culture areas should be
designed to minimize strong
designed to minimize strong
waves, that directly crash in to
waves, that directly crash in to
the net fence:
the net fence:
–
–
If culture areas locates near

If culture areas locates near
to the beach should cut
to the beach should cut
intertidal zone into
intertidal zone into
rectangle shape as ladder
rectangle shape as ladder
along the beach.
along the beach.
–
–
If culture area locates in
If culture area locates in
within estuaries (bank)
within estuaries (bank)
should cut into square
should cut into square
areas.
areas.





15
Culture monitoring and management
Culture monitoring and management
•
•
3

3
-
-
4 months of the
4 months of the
beginning to 20 mm in
beginning to 20 mm in
size, seed were moved
size, seed were moved
by current of water
by current of water
(wave) to the fence
(wave) to the fence
bank. Therefore, bring
bank. Therefore, bring
them back to deeper
them back to deeper
water to avoid hot
water to avoid hot
water or shortage feed.
water or shortage feed.

Culture monitoring and management
Culture monitoring and management
•
•
Always checking fence
Always checking fence
to ensure clam could
to ensure clam could

not escape from fence
not escape from fence
by current of water
by current of water
•
•
If clam were
If clam were
concentrated at the
concentrated at the
corner of fence, move
corner of fence, move
them to opposite
them to opposite
places
places







16




5.1.2 Expression of interest and feedback from farmers
• Farmers showed keen interest in clam culture in the pond as well as in intertidal

areas. Farmers felt that clam culture in the pond would allow more poor farmers
in coastal village have the opportunity involve in clam culture as one of main
livelihoods.
• Farmers would also like to get clam seeds from hatchery as well as wild seed
collected from natural nursery areas. However, for the collection of wild seed,
local government need to develop a management plans including sustainable wild
seed collection strategy so that natural clam stock will not be adversely affected.
• Farmers suggested that research should be carried out on culture clam with others
species as fish and seaweed in pond.
• Farmer expressed concern on seed availability. Assured seed supply is an
important factor in any aquaculture business. In clam culture seed cost is 60-70%
of the total operational cost. Therefore researchers and local government should
develop a strategy for seed clam production for each place if possible.
• Farmers are please to note that CARD project not only provides them with culture
technology but also supply quality clam seeds.


Table 1: Name and address of farmers selected

No Name Address
1 Bui Manh Hung Extension Centre of Thanh Hoa Province
2 Nguyen Xuan Hung Extension Centre of Thanh Hoa Province
3 Nguyen Van An Farmer from Thanh Hoa Province
4 Truong Huu Thu Extension Centre of Quang Tri Province
5 Nguyen Van Ky Farmer from Trieu Phong District, Quang Tri
Province
6 Dang Ngoc Tho Technical of Fisheries Department of Quang
Binh Province

17

7 Hoang Thi Hoa Farmer from Ba Don Town, Quang Binh
Province
8 Nguyen Thi Ngoc Farmer from Ba Don Town, Quang Binh
Province
9 Nguyen Thi Thuan Farmer from Ba Don Town, Quang Binh
Province
10 Nguyen Van Tam Farmer from Ba Don Town, Quang Binh
Province
11 Le Thanh Nhat Technical of Extension Centre of Hue Province
12 Nguyen Ngoc Thuy Farmer from Phu Vang District, Hua Province
13 Nguyen Van Thanh Farmer from Phu Vang District, Hua Province
14 Le Van Hung Farmer from Phu Vang District, Hua Province
15 Tran Quoc Thanh Director of Fisheries Department of Nghe An
Province
16 Tran Van Cao Technical of Extension Centre of Nghe An
Province
17 Ngo Xuan Dai Farmer from Dien Chau District, Nghe An
Province
18 Le Thanh Tung Farmer from Quynh Luu District, Nghe An
Province
19 Tran Thi Van Technical of Fisheries Department of Nghi Loc
District, Nghe An Province
20 Phan Thi Thuan Technical of Fisheries Department of Dien
Chau District, Nghe An Province
21 Pham Phu Hoa Technical of Extension Centre of Ha Tinh
Province
22 Nguyen Van Hoa Technical of Extension Centre of Ha Tinh
Province
23 Nguyen Duc Long Farmer from Ha Tinh Province

Photos from the Workshop

Dr. Martin S Kumar is introducing to the participants about the requirements for on farm trial

18


Mr. Nhu Van Can, Director of Project is introducing about the project as well as of the workshop


Participants are attending the workshop; they are interested in clam culture in pond


5.1.3.Study tour

The study tour was conducted as part of the training programs for demonstration of the
clam culture trials by showing the lead farmers the natural nursery areas of clam and the
original place where from the clam, Mertrix lyrata has been translocated in the North and
Central part of Vietnam. Also, farmers were shown a newly established clam hatchery at
Ly Nhan, village, Can Gio district. This hatchery has been constructed by ARSINC in
collaboration with Van Xuan University.

List of the farmers who were involved in demonstration participated in the study tour is
provided in the Table 1.

19

10 farmers from 6 provinces participated in the study tour which began on 23 April 2008,
morning 8 am with the visit to newly established clam hatchery at Ly Nhan. The hatchery
has the capacity of producing 50 million spat in one season. ARSINC in collaboration

with University of Van Xuan resulted in the establishment of a modern clam hatchery
with technology developed by the CARD project. The establishment of this particular
hatchery is not included in our project activity; however, it was result of CARD project
implementation as farmers from south demanded it.

Farmers were taken to show the nursery areas where most of the wiled spat occurred.
Local farmers mainly depended on wild seed collected spat from these natural nurseries.
The estuarine conditions created by the river, Soai Rap joining the sea. A stretch of 2
kilometer, these estuarine conditions prevailing makes it an ideal ecology for clam larval
growth. Most of the wiled seed are collected from this stretch.

Farmers were shown intertidal culture in the local area and also visited clam pond culture
established by ARSINC.



Fig 1. Study tour team



20


Fig 2. Visit to calm hatchery Fig 3. Visit to clam culture ponds



Table 2: List of participants has participated in study tour in Ho Chi Minh City and
interested in on farm trial in clam culture (22 - 25 May 2008)

No. Full mane Address Registered for on
farm trial
1 Phung Van Dan Hoang Phu Commune, Hoang
Phu District, Thanh Hoa
Province
Mobile: 0913115955
Intertidal culture
2 Le Van Hoanh Hoang Phu Commune, Hoang
Phu District, Thanh Hoa
Province
Mobile: 0913026168
Culture in pond
3 Le Thanh Tung Quynh Thuan Commune,
Quynh Luu District, Nghe An
Provice
Phone: 038865886;
Mobile: 01685114406
Culture in pond
4 Le Xuan Hung Mai Phu Commune, Mai Loc
District, Ha Tinh Province
Phone: 039846217
Mobile: 0912487697
Culture in pond/
Intertidal culture
5 Pham Ngoc Lam Thach Bang Commune, Loc
Ha District, Ha Tinh Province
Mobile: 0935809496
Culture in pond/
Intertidal culture

21
6 Nguyen Duc Long e, Loc

Culture in pond Thach Bang Commun
Ha District, Ha Tinh Province
Mobile : 0986597840
7 Nguyen Van Tinh , Loc

Culture in pond Thach Bang Commune
Ha District, Ha Tinh Province
Mobile : 0914442684
8 Nguyen Van Tam Trach


Culture in pond/ Ba Don Town, Quang
District, Quang Binh Province
Phone: 052511466;
Mobile: 01684341624
Intertidal culture
9 Nguyen Van Ky ieu
88171028
Culture in pond Trieu An Commune, Tr
Phong District, Quang Tri
Province
Mobile: 09
10 Trung Huu Thu io Linh Culture in pond Gio Viet Commune, G
District, Quang Tri Province
Mobile: 0914178447
11 Nguyen Van Thanh g Culture in pond Farmer from Phu Van
District, Hue Province

12 Le Van Hung istrict, Culture in pond Farmer from Phu Loc D
Hue Province

n 24 April a workshop was conducted to discuss and clarify any issues related to
Farmers insisted that the quality and quantity of the seed supply should be
aff from ARSINC and extension department would periodically visit
farmers and provide technical guidance.
O
Farmers participation in the demonstration trials. It was a half day workshop involving all
10 farmers project Manager from ARSINC and Project leader from Australia. The main
issues raised include:

•
managed and controlled by ARSINC. The project Manager assured the farmers
that ARSINC in collaboration with extension department will ensure the quality
and the quality of the seed supplied to the farmers involved in the demonstration.
• The need for a three party (ARSINC, Extension department and framers)
agreement was emphasized by the farmers. This was agreed by the project
Manager. The extension department has already agreed for such an agreement.
• It was agreed that ARSINC would supply seed required for 2000 to 5000 m
2
pond
for demonstration. However, farmers can buy seed for meeting additional
demand.
• ARSINC would provide culture plan, procedure and reporting information to
farmers. St

22
• Farmers are required regularly report the progress of the culture through
prescribed reporting format. The extension officers will assist in reporting the

culture progress.

The study tour was ended in a positive note with confident farmers eager to start the
culture trials.

5. 2 Revised experiment on larval rearing.
ent was designed to fine tune the larval rearing technique. The revision
ing Australian project leader and the
ental results were reported in the
• to develop optimum water exchange procedure by determining suitable water

M
ent was conducted in three replicates for the following three stocking
s different treatments. Three stocking densities used are 5, 10 and 15 larvae ml
-
rom 2000L storage tank placed above the level the
A revised experim
was carried in consultation with project team includ
result is included in this report. The previous experim
milestone 7 report. The objectives of the revised experiment were:

• to get more accurate information on the stocking density of the larvae at
swimming stage in order to maximize survival rate;
exchange frequency; and
• to prepare suitable substrate for the larval settlement.

5.2.1. Experiment 1:

ethod
This experim

densities a
1
. The water supply was arranged f
experimental tanks. The water from the storage tank was supplied by gravity. The
selected larvae were transferred into experimental tanks containing 100 L of filtered
seawater at appropriate density specified for the three treatments. Average initial shell
length of D-larvae (n = 50) was 75.38 ± 3.82 µm. Larvae were reared in water flow-
through system. Water temperature was kept in range of 23 - 27
0
C; salinity was kept at
25
0
/
00
with continuous aeration to supply oxygen. Larvae were fed a combination of 3
algae species: Isochrysis galbana, Nanochloropsis oculata and Chaetoceros mulleri four
times a day at 100.000 cell ml
-1
of water. Duration of experiment was 9 days, when
larvae had reached metamorphosis stage. During the experimental period, shell length of
15 larvae was measured daily after feeding time for each replicate using an ocular
micrometer. Survival of larvae was calculated every three days culture till at the end of
culture period (at day 9 culture), when they had became the metamorphosis (post setting
stage). The environment factors in the system were recorded twice a day to ensure the
better control on the rearing conditions. Data was analyzed by ANOVA. Correlation
analysis was carried out between growths, survival and stocking density. Significant
difference between each treatment means were determined by Tukey test, using

23
Statistical for Graph-Pad Prism-4 Demo software. Data are presented as mean ± standard

deviation.

Results

- Growth performance of larvae
able 3. Mean ± SD of length of larvae were reared at difference densities: 5 larvae ml
-1
,


T
10 larvae ml
-1
and 15 larvae ml
-1
.
Size (μ) at different stocking densities
Time
5 larvae ml
-1
10 larvae ml
-1
15 larvae ml
-1

123.7 ± 2.680
a
121.9 ± 2.160
a
118.7 ± 2.954

b
Day- 3
Day- 142.9 ± 2.39 ± 2.236
b

Day- 9 1 17 1
6 6
a
141.6 ± 2.714
a
138.8
74.4 ± 3.146
a
3.7 ± 1.951
a
71.2 ± 2.582
b


The average shell leng devi a larvae king
d are presented e resu t the gro e of
rvae varied between the different densities of 5 larvae ml , 10 larvae ml and 15 larvae
stocking densities: 5
- Survival rate of larvae stocked at different densities
ths with standard ation of M. lyrat at different stoc
ensities in Table 3. Th lts indicated tha
-1
wth performanc
-1
la

ml
-1
from day-3 cultured. Larvae reared at lowest density (5 larvae ml
-1
) had the mean
shell length highest compared to the larvae to other two treatments (10 and 15 ml
-1
.
However, the significant difference in growth was observed between the densities 5
larvae ml
-1
and 15 larvae ml
-1
(P<0.05); densities 10 larvae ml
-1
and 15 larvae ml
-1
. There
was no significant difference between density of 5 larvae ml
-1
and 10 larvae ml
-1
.with
regard to growth performance. In all the treatments the foot (metamorphosis occurred)
appeared at day-9, and then they were transferred to the settlement tanks.



Fig 4: Shows the growth of larvae at day-9 cultured at different
larvae ml

-1
, 10 larvae ml
-1
and 15 larvae ml
-1
.


24

Table 4. Mean ± SD o the densities 5
larvae ml
-1
, 10

larvae ml and 15 larvae ml
Survival % at different stocking densities
f survival rate of M. lyrata larvae was reared at
-1 -1


Time
65.67 ± 4.7
b
45.77 ± 6.1
c

5 larvae ml
-1
10 larvae ml

-1
15 larvae ml
-1

Day-3 80.00 ± 7.7
a

Day-6 64.67 ± 10.9
a
38.33 ± 5.0
b
22.44 ± 5.2
c

9.3 9.77 ± 3.2
a
3 ± 8.4
a
8.00 ± 4.2
a
Day 9

Data ble 4 showed ere reare sities in t t
had m ss similar su ± 4.200 00) from D
to me osis stage at d r results ed on hard r
aring studies .
n each treatment means were determined by Tukey test (P<0.005),
sing Statistical for Graph-Pad Prism-4 Demo software. However, on day 9 the

densities: 5 larvae ml

-
1
, 10 larvae m
metamorphosis.
from Ta that, larvae w d at these den he experimen
ore or le rvival rate (8.00 to 9.77 ± 3.2 -veliger stage
tamorph ay-9. Simila were report clam larva
re

The survival rate estimated on day 3 showed significance difference between treatments.
The survival rate on day 3 increased with decreasing stocking density. Significant
difference betwee
u
percentage survivals in all 3 treatments were more or less same. The survival rate in
terms of percentage, the results clearly indicated that the influence of density on survival
rate is significant up to day 3, the initial period of larval culture. However, if we convert
survival rate of larvae at the metamorphosis stage (see figure at day-9 rank in Table 4)
into number of larvae, the highest stocking density(15 larvae ml
-1
) had the highest had the
higher number of survival compared to other treatments.




Fig 5: Showed the survival rate of M. lyrata at difference stocking
l
-1
and 15 larvae ml
-1

at day-9 culture, when larvae had became


25