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Handling
and Transportation of Fingerlings
Transporting live fish involves hauling
of a large number of fish into a small quantity of water. Unless
this is done properly, water quality deteriorates causing fish
mortality. The use of plastic and buri bag or hauling box with
aerators are new methods commonly used in transporting live fish.
The objective of having a good transport system for live fish
is to minimize stress on the fish and ensure a high rate of survival.
Conditioning Fish-prior to
Transportation
Place
fingerlings havested from brood ponds or nurseries in "hapa"
or aerated concrete tanks at least three days prior to disposal.
This process is called "conditioning". It allows the
fish to recover from handling stress at harvest time. Feed fingerlings
during conditioning, but stop feeding 24 hours prior to disposal.
If
the fish are held in tanks, supply these with sufficient aeration.
Tanks used for holding fish should be clean, leak-proof, and
glazed or painted with epoxy paint to discard rough surfaces.
Smooth surfaces reduce physical injuries to fish. One cubic meter
of water in tanks can hold approximately 4.4 kg of fish.
Avoid
overcrowding in holding "hapas" or tanks especially
in the early morning when dissolved oxygen level is low. If fish
go near the surface gasping for air, increase aeration or decrease
the holding rate. Well-aerated water could hold more fish.
Method of Transporting Live
Fingerlings
a.
Plastic bag method
The
most common size of plastic bags which can hold large quantity
is 20 inches x 30 inches x .003 gauze double seine. Use standard
sized "bilid-bilid" "bayong", or pandan bags
to support the plastic bags. Transport 400 pieces of fingerlings
of size 22 for a duration of 24 hours for long distances and
for short distances 800 to 1,000 pieces of the same size for
not more than 6 hours.
Maintain the temperature at 28°C
to 30°C while transporting. To reduce fish mortality and
stress during the trip, place about 500 g of cracked ice between
the two plastic bags (figure 8). This technique increases survival
rate of fingerlings.
Pointers in using plastic bags
- a set consists of one pandan
bag and two plastic bags.
- check the plastic bags carefully
for holes, put one bag inside the other
- fill the plstic bag with eight
liters of clean water
- water temperature in the holding
"hapa" or tanks should be the same as that of the bag
- load the fish in the bag. For
small deliveries, count fish individually. For big deliveries,
use the average weight or volumetric method
- use the recommended loading
capacity to reduce mortality
- fill the bag with 1.5 L of medical
oxygen immediately after it is filled with fish
- tie the oxygenated bag with
rubber immediately to avoid oxygen leakage
- icing is advisable when transporting
fish for more than six hours and if water temperature is 30°C.
b. Hauling box or tank method
Construct
the haulin tank or box out of fiber glass, alumimum sheet, marine
plywood, metal sheet, or stainless steel. Construct this such
that it can hold water. Provide a cover to prevent water from
splashing. The cover should be provided with hinges to make it
fold. Put holes exactly the size of the agitator. Paint boxes
of marine plywood with epoxy paint to make these durable. The
most common size of hauling boxes made of marine plywood is 3
feet long x 2 feet wide x 2 feet deep (Figure 9).
An agitator is basically mechanical
stirring blade. It is covered with a screen to keep the fish
from being hurt. The blade extends partially into the water and
its rotation produce air bubbles. Connect this to a 12-volt battery
of the delivery vehicle or provide extra battery for that purpose.
The capacity of the hauling box
is approximately 0.18 to 0.24 kg of fish (irrespective of size)
per liter of water 50-60 kg per 270 liter box.
Loading Techniques
Before
loading the fish in the hauling box or tank, know the total weight
of the fish. Do this by getting their average weight using the
followig formula:
|
Average weight = |
Total weight of
the fish sampled in kg |
| ------------------------------------------------------ |
|
Total number of
fish sampled |
| Example: |
|
| Total
weight of fish sampled |
= 1000 g or 1 kg |
| Total
number of fish sampled |
= 1000 |
| Using the formula: |
|
| Average
weight of fish |
= 1 |
| |
1,000 |
| Average
weight of fish |
= .001
kg or 1 gram |
| |
|
| Number
of fingerlings to be loaded
= |
Capacity of hauling box |
|
---------------------------------------- |
|
Average weight of fish |
| |
50
kg |
| |
.001
kg |
| Number
of fingerlings to be loaded
= |
50,000 |
| |
|
Fill the hauling boxes with water to
about one-half of the agitator's shafts and run the agitators
for 3 min. before loading the fish to provide oxygen while loading.
Water temperature of the hauling
box should not vary more than 5°C from that of the holding
water. Handle fish carefully to prevent shock and stress.
Unloading Techniques
Abrupt
changes in temperature cause thermal shock to the fish. Check
water temperature before releasing the fish into the stocking
pond to prevent thermal shock and stress.
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