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General infomation about white clam

I. Biological characteristics:

1. Living areas:

In Vietnam, clams lives mainly in GoCongDong (Tiengiang province), Batri, BinhDai, ThanhPhu (Bentre province), Caungang, Duyenhai (Travinh province), Tienhai (Thaibinh province), Nghiahung, Giaothuy (Namdinh province).

Clams live in the muddy sand beach near the mouths of rivers.

2. Breeding:

Clams have clear male and female sexual characteristics, no neuter clams have been found yet.

Clams breed all year round but the main breeding season is in June when the rainy season starts.

One mature female clam can produce from 3,168,000 to 8,650,000 eggs, but the average is approximately 5,362,000 eggs.

The mature female clam has shell height minimum of 28mm and the male 32mm.

During the breeding season, the mature male and female clams eject sperms and eggs, respectively, into the water. Fertilised eggs grow into larvae. Larvaes grow in the sea water and the shell develops to help it sink to the sandy bottom. It develops first into a very very small clam called a rice brain clam and it’s about half the size of a grain of rice. The shell is extremely thin and flat, weighing only 0.04 – 0.07g/pc (# 15,000 – 25,000 pcs/Kg), it buries itself into sand about 1cm. deep. By means of the tide movement, the rice brain clam is moved up and down and filters food from the sea water in order to grow. 

After 30 days or so the rice brain clam grows to become a rice clam with a weight of 0.16 – 0.20 gram/ pc ( 5,000 – 6,000 pcs/kg); the shell is now harder and this is the time when fishermen catch it and move it to a well care pond, which has conditions very similar to its natural living places.

3. Eating behavior:

The tide changes twice a day; when the tide is in, the clam floats up to absorb food and when the tide ebbs, the clam dives into the sand to avoid enemies as well as sunshine.

Clams eat by filtering the sea water.

4. Growing process:

In good conditions, clams will grow as follows:

-        From egg to rice brain clam: 2 months

-        From Rice brain clam to seed clam ( 800 – 1,000 pcs/Kg): 6 – 8 months

-        From seed clam to adult clam ready for harvesting: 10 – 11 month (approximate 50 pcs/kg).

5. Harvesting:

Every month (based on the Lunar calendar), there are two periods of higher tides, which are at the beginning and the middle of the month. At these times, the tide will fluctuate more than usual so the harvesting will be done when it’s at its lowest ebb..

Until now, the white clam has been harvested manually, using some simple utensils to dig the clam out of the sand.