Technical and economic feasibility of applying the Better Management Practices (BMP) to household aquaculture in Vietnam - MS2" potx

Ministry of Agriculture & Rural Development


002/05/VIE
Technical and economic feasibility of applying the
Better Management Practices (BMP) to household
aquaculture in Vietnam


MS2: BMP PROTOCOL REPORT


Nguyen Van Quyen, PhD
(1),
Nguyen Xuan Suc, MSc
(1),
Mai Van Ha, MSc
(1)
Le Van Khoa, PhD
(1),
Dinh Van Thanh
(1),
Virginia Mosk, MSc
(2)
(1): Research Institute for Aquaculture No.1
(2): Animal Biology, University of Western Australia

May, 2007

I. POND PREPARATION

1.1 Pond condition
The area of semi-intensive pond should
be from 0.5-0.7 ha, with well-
constructed and separated inlet and
outlet. Pond bottom should slope down
to outlet.


1.2 Pond cleaning
Before PL (Post-larva) releasing 25-30
days, draining out pond water and
drying pond bottom from 7-10 days.
Ploughing pond bottom after removing
mud top-layer. If acidic bottom,
repeating water flushing 2-3 times.

Ploughing on dry soil using tractor
If can not drying pond bottom due to
natural condition, wet cleaning method
should be applied. Using pump to drain
pond bottom then using high pressure
pump to remove mud top-layer. If acidic

bottom, repeating water flushing 2-3
times.


Removing mud layer manually
1.3 Pond liming
Use of CaO and CaCO
3
in the ratio of
2:1 for disinfection and bottom pH
increasing. Pond bottom needs wetting
and pH checking before lime
application in order to experience of
lime effectiveness and right application
amount. Refer to below table as a
reference

pH bottom
soil
CaO/ha CaCO
3
/ha
>6 1000 500
5-6 2000 1000
<5 3000 1500


Lime application to pond bottom

1.4 Water supplying

Water before pumping into culture pond
needs filtering and treating within
reservoir using permitted chemicals and
probiotics. Use of net bag fixed at 2
sides of pipe (small mesh size) for water
filtering, discarding unwanted foreign
objects and predators from ponds.
Suitable water depth is at least 1.0 m.

Water filtration by twin bag filter

1.5 Water color inducting
About 10 -15 days before stocking,
water color induction needs to be
implemented using inorganic fertilizer.
For example application:
- A complex of Nitrogen and
Phosphorus in the ratio of 2:1 dosing
20-30 kg/ha water surface.
- Utilization of NPK (3:5:1) dosing 20-
30 kg/ha.
If water coloration fails 3-4 days after
fertilization, an additional application of
3-5 kg/ha to get desired water color
soon.

Ideal green colored water after fertilization

1.6 Community involvement
In the step of pond preparation,

involvement of community can be as
followings:
- An agreement on culture time, pond
preparation, wise water tide and
pumping.
- Well-planed pond bottom cleaning,
avoiding negative impact onto wide
community.
- Cooperation in buying shrimp pond-
purposed materials and equipment like
lime, fertilization, probiotics so that
pond management and operation
expenses will be minimize (price
negotiation, feed transportation) and
maximize benefit as a result.


II. POST-LARVA SELECTION AND
STOCKING

2.1 Post-larva selection
Choosing a prestige PL production
station with certified quality of PL
granted. PL buyer should come to
supplier early to learn and study origin
and condition of PL that is to be bought.
Observations should be made on
activity, color, size, etc. from the
selected tanks in the hatchery.

The post larvae should be uniform in
size with relatively uniform body color
and should be actively swimming
against the swirling water current
produced in a round tub.

PL batch should be bred from one
brooder, not to be graded (physical
damage avoided). A PL15 should have a
critically suitable body length of 12 mm,
if not, PL is recognized to be stunt and
poor quality.

Healthy and active PLs uniform size

Good color of PL should be ashy grey
or bright transparency, telson should
open when swimming, clean appendices
while poor PL will appear to be milky
white.

2.2 Some suggested practices for PL
quality checking
1) When stop aeration PLs will jump
out of water surface, get some PLs into
bucket and swirling manually water in
order to create mediate water current,
good PLs will stay in the bottom and
swim counter clock wise with water
movement while weak PLs will

concentrate in the central of bucket-
reject this PL batch

2) Formalin concentration of 100 ppm
and the PL should be treated for above
30 minutes. It is essential that water in
the tank is well aerated; ideally using
oxygen cylinders. After this treatment
the water is stirred to concentrate all the
dead and weak seeds at the center-
bottom of the tank.
3) Formal sock: using 100 PLs into
white color bucket with 10 liter water
mixed with 2 ml formalin and aeration.
Giving an observation within 30
minutes for mortality, if it is more than
10 PLs the batch is in poor quality.
4) Freshwater sock: Getting 40 PLs into
a container with the nursery- origined
water, then adding the same volume of
fresh water into the container (ratio of
1:1). Giving an observation within 60

minutes for mortality, if it is more than
10 PLs the batch is in poor quality.
5) PCR testing: Sampling 30 PLs into a
prepared nylon bag (good water with
well-aerated), then transfer to Lab as
soon as possible for PCR and MBV
checking. Consulting PCR expert and

technician for the quality of tested PLs.


1.3 Stocking
Suitable time for PLs stocking into pond
is 5-6 am or 5-6 pm.
PLs should also have to be acclimatized
to pond water conditions like salinity
and temperature with gradual addition
of pond water to the tank.

Acclimatization of seeds to pond water
Temperature conditioning by gradually
pouring pond water onto PL bags, then
put these bags into the ponds within 10
minutes prior to releasing as long as
temperature is equal in between in bag
and out pond.

It is suggested that salinity in PLs
nursery station and ponds should be
similar in value, the difference should
not be more than 5 ppt. Salinity
adaptation needs conducting by slowly
adding pond water into PL bags or
putting al already temperature-adapted
in a big container and adding gradually
pond water accordingly.
2.4 Stocking density
Stocking density will completely

depend on investment and technical
know-how capacity of household.
However, suggested stocking densities
as given below:


Stocking
density
(PL15/m
2
)
Expected
productivity
(kg/ha/vụ)
10 - 25 3000 kg
25 - 30 4500 kg
30 - 40 6.000 kg

2.5 Community- based management
- Making groups for selecting and
purchasing PLs, gathering PLs prior
to PCR and MBV testing
- Concentrate PLs transportation and
acclimatization.
- Production grouping gives more
advantage with regard to price
bargain and PL quality.
III. POND, ENVIRONMENT AND
DISEASE MANAGEMENT
3.1 Water quality management

To void acute change of temperature
and shock to the animals, try to maintain
pond water level at least 1 m (ideal
suggested is 1.2-1.5m).

Pond water with a healthy
phytoplankton bloom is green. Suitable
transparency of pond water
phytoplankton is 30 - 40 cm. If
transparency is greater than 40 cm,
exchange 20% of pond water and then
inorganically fertilize 20 - 30 kg/ha. If
transparency is less than 30 cm,
exchange 20 - 30% of water volume.

If water color is dark and has low
transparency caused by dead algae,
exchange 20-30% water volume (using
reservoir water) till color improved and
lime using CaCO
3
at a dose of 50-100
kg/ha.

Black color water (poor quality)
Do not use any tool or facility (net, boat,
etc.) in more than one pond, in order to
avoid disease cross-contamination. If
you must share these tools, it is

necessary to disinfected or clean and
then dry for at least one day.

Poor pond management
Clear pond water indicates poor algae
community. Supplement fertilization
using phosphate at a dose of 2-3 kg/ha
every 2-3 days till getting desired color.

Good
Bad
Water color as an indicator for quality

3.2 Use of Paddlewheels
Paddlewheels should be used for a semi-
intensive shrimp culture pond in order
to increase dissolved oxygen and
decrease toxic gases (H
2
S, NH
3
, etc.). If
pond area is 0.5 ha and stocking density
is 20 PL/m
2
, 4 paddlewheels, with 8
propellers total, should be used.
Generally, aerators should be placed to
maximize circulation throughout the

pond and to avoid leaving any dead
areas. Time table for paddlewheel use is
below:

Shrimp
age (week)
Paddle-wheel using
1 – 4 4h30 - 5h30
4 – 6 2h - 5h30; 17h - 18h
7 – 11 2h-5h30; 8h30-9h30;
17h-18h; 20h30-21h30
12 – 14 0h-5h30; 8h30-9h30;
17h-18h; 2030-21h30
15 –
harvest
23h-6h; 7h-9h; 16h-
18h; 19h30-21h30



3.3 Feeding
In the first two months of culture period,
it is a habit of shrimp to locate near
shore, therefore feed should be casted
within the area accordingly. From 3
th

month onward feeding should be
homogeneous all over pond surface,
excluding dirty bottom area and too

close to pond bank. Stopping aeration
30 minutes prior to feeding, checking
feeding efficiency about 1 hr after
feeding and re-operate oxygenation.

Use of feeding tray to control feed
Poor quality feed including commercial
pellet is not advised to use, particularly
home-made feed using poor quality
materials like trash, crustacean as they
can be water-polluted cause and disease
infection.

Bottom algae and floating lab-lab need
manually removing using
Keep examining feeding area for
pollution condition, it is good if bottom
layer is brown color or thin brown
layer.


Sludge on top soil layer of the pond bottom
If bottom soil is black, try to feed
offshore using distribution boat,
reducing feeding rate within 2 days and
exchanging water of 15-20 cm.


If acidic soil or yellow water color
observed, applying lime along pond

bank before and after raining.

Yellow water in acidic soil after raining
In normal condition (no disease
recorded), sampling some shrimp and
observing feed fullness in gut 2 hrs after
feeding, if not, apply more feed.


Quantity of feed depending on quantity
of shrimp in the pond. Normally, shrimp
is smaller rate of feed is higher. Refer to
below table as a reference
Good
Bad
Shrimp size
(g/shrimp)
Rate of feed
(%)
2 6.5
5 5.5
10 4.5
15 3.8
20 3.5
25 3.2
30 2.8
35 2.5

Good
3.4 Disease management

Making note daily for abnormal shrimp
health condition and syndrome, number
of death and disease infected near by
pond bank. Dead shrimp must be
remove out of pond and treated
correctly (bury them away from the
ponds).

Removal of dead shrimp from pond margin
Netting 10 shrimp weekly to check
cleanness of shell and gill. If dirtiness
found applying offshore feeding,
eliminating bloom algae using hand or
net with small mesh size. If possible
experiencing water exchange and
liming with a rate of 200-300 kg/ha

Shrimp with fouling on shell

About 3-4 week after stocking if shrimp
keeps swimming a long pond
bank/edge, pond bottom should be
checked whether bottom algae
occurrence or black mud layer
accumulation. If so, lessening feeding
amount and frequency, exchanging
water, dolomite or lime application.
If disease infected and dead shrimp
found nearby pond edge, cutting down
feeding rate and replacing water at 15-

20 cm height, applying CaCO
3
powder
or Dolomite (200-300 kg/ha).

Shrimp with black gill disease

If then high mortality in 2 consecutive
days, considering emergency harvesting
can be carried out.

If White Spot Disease (WSD) recorded,
not to discharge water and immediately
inform neighboring pond owners. Check
any abnormalities in water and soil
condition and take immediate action to
correct the problem.

In case of dead shrimp found after
raining, instantly liming pond water and
banks, best practice is to apply lime
before raining.

Shrimp with WSD infection



In early morning if swimming nearby
pond edge, feeding and oxygenation
need putting in to operation.

3.5 Community- based management
Working in group to choose feed,
probiotics and other materials
supplier/seller so as to purchase them
with suitable price, and lower
transportation cost.
Inter-supervising sanitation condition
and environment protection attitude in
term of waste water treatment, disease
report and putting out.
Timely report disease infection
condition to wide community. Giving a
capital assistance in disease control,
management, and zoning.
Sharing experience and technical know-
how in shrimp pond management and
operation.
In cooperation with neighboring
communities for the mission of water
quality protection and management,
disease control and quarantine.
Farming in groups/communities may be
economical by contribution in investing
environment and disease monitoring
devices like test kits, pH and DO
meters, PCR kit.
Community can also bring social
atmosphere that motivate significantly
culturists.

3.6 Frequently faced issues and its
remedies
1) Low transparency (less than 30-40
cm): water exchange (20-30 %),
application of Zeolite or Diatomite
(5-10 kg/100m
2
)
2) DO super-saturation (caused by
algae bloom, sunny) that may cause
air bubble disease: formalin spraying
or using Na
2
S
2
0
3
(3-5 ppm).
3) To dispose of excess Chlorine or
Ozone used for disinfection, using
Na
2
S
2
0
3
at the rate of 3- 5 ppm
4) Water with low pH (< 7): use of CaO
at the dose of 5-10 kg/100m

2
.
5) Water with high pH (>8.5):
application of fine sugar 10-12
kg/ha, or drive water through bio-
treatment system, or acid acetic
produced by fermenting 10-15 kg
rice bran in 1 m
3
pond water in 7
days (extract supernatant only).
6) Oil film can be eliminated and
skimmed using clean cloths or inner
part of maize
7) Temperature stratification (mainly
caused by heavy rain): draining out
top layer water, operating mixing
devices, and then Zeolite or
Dolomite applied.

IV. HARVESTING AND
MARKETING

4.1 Partial harvesting
When reaching individual size of 25-
30 g. If shrimp is not uniform in size
use of grading device to catch wanted
one.
4.2 At once harvesting
Drain out water for this method of

harvesting. Shrimp after smolting
should not be experienced with
harvesting due to soft shell.
4.3 Post-harvesting preservation
As soon as harvesting, shrimp have to
washed and iced (ice/shrimp ratio is
1/1), transportation to processing unit
directly.
4.4 Critical role of community
responsibility
Community based-market can give an
advantage in negotiation selling price
and choosing right buyer, particularly
when free disease shrimp produced.
Community plays an important role in
the production chain, from production
preparation to product marketing.