What are biology characteristics of Tra and Basa fish?
Pangasius hypophthalmus – Tra
Tra is a fish with long body, grey black back, little white belly, big mouth and two pairs of barbells. The raising period varies from 6 to 8 months to reach the weight of 0,8 – 1,3 kg/fish. Tra fish mainly live in fresh water but also in blackish water (with salinity percent of 7 – 10‰), can bear in alum water (with pH level > 5), in hot tempreture up to 39oC but be easily died at tempreture below 15oC. The volume of red corpuscles in Tra fish are much more than other fish. As the fish has an accessory respiratory organ and can also breathe with air bladder and skin, they can bear in the water lacking dissolved oxygen. The oxygen consumption and activity level of Tra fish is three times lower that the ones of a silver barb.
Pangasius bocourti – Basa
Basa is also a fish with long body. The standard length of the body is equivalent to 2.5 times of the height of the body. It has a short, slight round and flat head, a wide forehead and a small mouth of which the width is less than 10% of the standard length and which is lightly askew the snout. Its teeth of the lower jaw are big and wide and can be seen when the mouth is close. It has two pair of barbells, the length of the pair at upper jaw is equal to the one of the head, and the whiskers are long to or over the end of pectoral fin. It has big eyes, belly and spleen, the back side of the body is flat, the back and the head have the grey green colour, and the belly has the silver-white colour. The height of the tail-end is more than 7% of the standard length of the body. The raising period varied from 10 to 13 months to reach commercial weight of 1 – 1.5 kg/fish.
As Basa fish has no accessory respiratory organ and requires an oxygen level higher than the one of Tra fish, it can poorly bear in water with low dissolved oxygen level. Basa mainly live in freshwater, can lightly bear in brackish water and in alum water with pH level > 5,5. The supported tempreture is from 18 – 40oC and the minimum oxygen level is about 1,1 mg/litre. In general, Basa fish can not support in severe environmental conditions as much as Tra fish. Therefore, they are mainly raised in floating cage.
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