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 harvested 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 28Â°C to 30Â°C while transporting. To reduce fish mortality and stress during the trip, place about 500 g of cracked ice between the two plastic bags. 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 plastic 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 haul in tank or box out of fiber glass, aluminum 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.
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.
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 following formula:
Average weight = Total weight of the fish sampled in kg / Total number of fish sampled
- 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 5Â°C from that of the holding water. Handle fish carefully to prevent shock and stress.
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.
source: STII and PCARRD