The Basics of Pangasius Aquaculture, Part 4 Rearing

Food Source

Pangasius is an significant food fish and is farmed expansively in many parts of the world. It is one of the most important aquaculture species in Thailand, along with other farm-raised shark catfishes.

As stated earlier, it has caused much debate within the U.S., with legislation passed recently to prevent its imports from cutting into American farmed catfish sales. Prohibited to be labeled as “catfish” in the U.S., Pangasius is now labeled as “swai” (its Thai name), “sutchi catfish”, or “striped catfish”.

This fish is sometimes sold as the superior “basa”. Compared to the basa, this fish is thought to be inferior, as its meat is coarser and comes in thinner.

Despite this, swai is still common as it is much cheaper to maintain, easier to breed, and is also a faster-growing species. It is said that 90% of fish sold as basa is actually swai.

“BFAR’s concern is to study its difference from other catfish and other fish in general. They conducted a risk analysis on how safe is Pangasius as an aquaculture specie,” continued Palma.

It eats vegetable residues, rice grains (although it lowers the quality of water) It also eats fermented water hyacinth and commercial feeds. It grows bigger in a matter of six months, up to l kilo. It grows 5 to 6 grams per day. It was once called Baboy sa Tubig.

A critical stage in feeding is when it absorbs its own yolk. It becomes extra-cannibalistic when he eats all the yolk. After absorbing their own yolk sack, survival of all fries will be critical during the first three days. The cause of most mortality is cannibalism and unavailable natural plankton such as moina and artemia,

Social Behaviors

When they are young, they like to school up, but will become more and more solitary as the get older. They are generally a good community fish and can be kept with most size tank-mates.

Sexual Differences

Males are more slender than the females and have darker striping. Females have swollen round shape, soft and reddish vent abdomens, silver gray body color, and if slightly stripped, the mature female, which is ready to spawn, its yellow egg can be seen. Males have abdomens that are flat, smooth and not as big as female, vent is reddish color but not swollen. Matured male will show milt when stripped.

Reproduction

In 2005, the Mekong Delta produced 3 billion of larvae to be placed in their farms. In natural surroundings, the reproductive season starts from May to June. In artificial reproduction, the fish becomes full-grown and lush early through highly developed water temperature management and can lay eggs earlier than in the natural environment.

Each female Pangasius can have 67.000 eggs (taken a parent fish of around 7kg weight). The Pangasius strains used for farming have been developed out of existing wildstock. Today, the fish is fully incorporated in the farming process. Choosing the Parent Fish is most essential to ensure healthy juveniles afterwards. Strong fishes from good strains should be from 3-4 kg and namely 3 years old.

Then the sperm is stripped on top and is mixed mostly using a dry and clean chicken feather. After being stirred from 20-30 seconds, the eggs will be activated and inseminated. And at the end of the process, they will use tannin liquid or the juice of pineapple to separate the fertilized egg from the surrounding tissue.

The procedure of incubation will be in the cement tank for the eggs being separated. The density is about 20,000 to 30,000 eggs per liter for Pangasius hypophthalmus and about 500 eggs per liters for Pangasius bocourti. The size of the fish after 20 days will be around 3cm for Pangasius hypophthalmus. Before transporting to the farm sites, the juveniles are put into water managed by tanks and nylon packs with oxygen. The juveniles are ready to place into the farms at 3 centimeter and they cost the farmer around 1.300 Vietnamese Dong (around 10 US Dollar Cents) per fish.

Care and Feeding

Since they are omnivorous, the Pangasius Catfish or Iridescent Shark Catfish will generally eat all kinds of live, fresh, and flake foods. To keep a good balance, give them a high quality flake food or pellet everyday. Feed brine shrimp (either live or frozen) or blood worms. As they get older they lose their teeth, and like the Pacus, become more and more vegetarian. Keep in mind that the use of Insecticides, antibiotics, waste water and leftover food discharge to pond and other illegal chemicals will prevent progress.

Culturing

Pangasius can be cultured in fishponds, concrete fish tanks, fish cages and fish pens with the acceptable water conditions: Hardness of 2-200 dGH; Ph of 6.5 to 7.5, temperature of 72-79 °F (22-26 °C) and at least 4-5mg/l of dissolved oxygen in the pond from naturally producing oxygen from phytoplantons or mechanical aerator.

Rearing in Earthen Ponds

The pond should be roughly 1,600 square meters or at least 400 square meters. Growth of the Pangasius hypophthalmus is fast, which is why the appropriate depth is approximately 1.5 – 2 meters. The pond should be situated near a water source in order to fetch in and extract water. Pond preparation is the same as general preparation for other fish ponds. Water to be used in the pond must have a fitting pH value and a proper oxygen concentration. Fingerlings to be used should be selected based on the healthiness of the fish—without wounds, no abnormalities and no disease and approximately all same size to keep them away from fighting for food. Pellet feeds are advisable for feeding to ensure faster growth.

Stocking rate is about 10-15 fish per square-meter. Foods for feeding include pellets, trash fish, water plants and small animals such as insects and worms. Given the proper feeding and management, it can grow to 1 – 1.5 kilo in 5 – 6 months time. Catching the Pangasius can be conducted using suitable net.

Rearing in Floating Cages

Location of floating cages should be near flowing water like rivers, dams and lakes. Size of cages should be 10×10 meters by 5 meter depth. Stocking rate is about 30-50 fish per cubic meter. Food for feeding are pellets, trash fish including water plants and small animals such as insects and worms. Harvest is much easier in cages compared to earthen pond. Nets that are unknotted are advisable to lessen the spones being tangled that can damage the fish.

author: Hans Audrice B. Estalbo, Marid Digest

 

 

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