The pearl culture project (TCP/BGD 2308) was planned as a result of the survey on freshwater pearl mussel resources undertaken from April 19 to July 17, 1982. Mymensingh was particularly selected as the site for the pearl culture farm, firstly, for having the mussel resources and secondly for having the Aquaculture Experimental Station of the Directorate of Fisheries in the District. The project can be attached to AES so that its personnel and facilities could be availed of, rather than established an independent new project for this purpose. The project was not started until the arrival on March 11, 1984 of the pearl technician recruited by FAO.
It is popularly known that freshwater mussels (Lamellidens marginalis and Parreysia spp.) of Bangladesh produced natural pearls. Thousand of mussels are being collected to be searched for pearls, but not all have pearls as formation were only incidental. A collector may open a thousand mussels but if unlucky, may not get even one pearl. In order to induce the mussels to produce pearls therefore will necessitate the introduction of a foreign material to start the formation.
Pearl culture or the stimulation of a living molluscs to produce pearls is an old industry. The Chinese were reported to have produced images of Lord Buddha on freshwater mussels more than 2,000 years ago. Lately, it was the Japanese who perfected the technique and started the commercial production of pearls at the start of this century, using the Japanese pearl oyster ‘Akoya gai’, Pinctada martensii.
To produce round pearls, the gonad of the mussels is utilized. A round nucleus or irritant is inserted inside the gonad, together with a mantle piece. When inside the body of a living mussel, the piece of mantle will merge with the wall of the gonad through a connective tissue. Such is for biological needs to maintain a living state while performing all functions as when still part of the mantle. The mantle produce the shell of the mussel and when inside the gonad, the mantle piece will develop into pearl sac. What happened actually is that the mantle piece will first go on a series of cell division to enclosed the nucleus and forming a sac, which will secrete the nacre (calcium carbonate) to be deposited around the nucleus. The nucleus become the core of the pearl.
In case when the nucleus was expelled, the graft (mantle) will produce tiny seed pearl. But when the graft was expelled out by the mussel even though the nucleus remained, there will be no pearl formation.
The length of culture period in order to have enough coating, depend on the size of the nucleus inserted and the condition of the environment, such factors as temperature, availability of food, etc. The culturing of the mussels after the introduction of nuclei until harvest time is important. When not properly taken cared of, they may die and the whole effort will be gone into waste. Knowledge of the bioloby of the molluscs will therefor play an important role for the success of the pearl culture activities.
The author have an expertise on pearl culture having been trained in Japan and worked in government and private pearl culture farms in his country for more than 18 years. But having another project, an oyster farm at Cox's Bazar to supervised, the project manager had decided that it will be proper to recruite a pearl technician who will work and train the counterparts on pearl culture. The author then regularly visit the pearl culturesite to plan and give advice on the activities.
Mr. R. Ponteras, the pearl technician recruited by FAO, arrived in Dhaka on March 11, 1984, for one year assignment in Bangladesh. He had his experience on pearl culture while working in the Philippines with private and government farms from 1968 to 1981. Although his experience was on marine species of pearl oysters (Pinctada spp. & Pteria sp.) there will be not much problem adjusting on freshwater mussels as the principle of pearl culture will be just be the same. What will be needed is a little adjustment of the operating instruments, the mussels being smaller in size.
At present, the pearl technician is working closely with the counterparts, training the latter on the proper procedure of operating mussels to produce cultured pearls.
There are two (2) genera of freshwater mussels found in Bangladesh, the Lamellidens and Pavreysia, of which the most common are the Lamellidens marginalis (Lamarck) and Perreysia daccaensis (Preston). For the purpose, L. marginalis was selected being common thus redily available and bigger size reaching up to 10 cm. in length (measured from anterior to posterior end of the shell). P. daccaensis can produce golden coloured pearls but being smaller in size (6 cm.) will entail difficulty in operation.
The mussels are found in rivers, ponds and lakes at knee deep. They bury themselves in the muddy or sandy bottom except for a small portion of the posterior end.
To operate the mussels, there is a need for special instrument in order that the technician can insert the graft and nucleus which will later develop into pearl. The instruments are similar to those used in Japan. A set of instrument was brought by the pearl technician but more will be needed in training a number of government officials. It will be difficult to procure these instruments from Japan so it was decided that five (5) sets will be fabricated which was then accomplished in two weeks time.
The following are the instruments for pearl culture (see figure 10):
Note * - items fabricated in Dhaka
A piece of mantle when inserted into the gonad can produce pearl, but in order to produce bigger pearls in shorter period of time nuclei or irritants are needed. The best material for nuclei are made of shells. Round nuclei made of shells are readily available in Japan. The shells are imported and the Japanese manufacture them into spherical form. Size range from 3 mm. to 10 mm. Importing such from Japan will take time while producing locally is not possible due to non availability of equipment and the raw material (thick shells)
For the use in the project, substitute materials were procured. These are made of plastic and ceramics. Plastic round nuclei are locally produced as ordered from the factory. Ceramic are small beads with center hole, strung as neclaces. Ceramic material would be better than plastic as the former is harder and almost similar in weight with that of pearl. As the ceramic beads available in the market are not perfectly round and with center hole, a manufacturer was sought to produce (2, 2.5 and 3 mm. diameter) rounded ceramic nuclei.
The Aquaculture Experimental Station is a freshwater fish culture research station situated inside the Mymensingh Agriculture University. It has a series of ponds, hatchery, office building and residential quarters. Two ponds are presently used for pearl culture both of which measures 15 × 60 meters (900 square meters) and numbered as ponds 60 and 61. Pond no. 60 is used to stocked operated mussels while Pond no. 61 for newly collected (unoperated) mussels. Depth of water of both pond was maintained at 0.6 meter during summer and 1 meter in rainy season.
Due to renovation being undertaken at the Office and Laboratory building of the station, a space was provided at the west wing of the Officer's Quarter No. B1 Furnitures such as tables, chairs and cabinets were provided and operation of mussels for producing pearls is being conducted.
Mussels were gathered from lakes, river and pools. These includes some ponds of AES and that of the University. Gathering of mussels is easy. They are in knee-deep waters so they can easily be picked-up. While wading in a pond, a gatherer may step on them and felt their precence on the bottom. The posterior end of the mussels is not submerge in the mud so it is easy to locate them. Two laborer were assigned for gathering mussels.
Monsoon rain hampered the collection of mussels as the pond water got high. Presence of leech at the university pond affected the gatherers.
Below is a record of mussels collected monthly:
| Month | Quantity |
| March | 1,370 pcs. |
| April | 1,764 |
| May | 2,214 |
| June | 3,058 |
| July | 1,270 |
| August | 4,785 |
| T o t a l | 14,451 pcs. |
Four government officers operate on the mussels to produce pearls under close supervision of the FAO pearl technician. This author give some advice on the proper operation procedure, such as the location in the gonad where the nucleus and graft are to be inserted, the right size of nucleus to be used, etc. The operation was started in March 1984 and is continuously going on. The following is a record of the mussels operated:
| Month | Quantity |
| March | 176 pcs. |
| April | 611 |
| May | 873 |
| June | 1,209 |
| July | 1,011 |
| August | 1,047 |
| T o t a l | 4,927 pcs. |
The counterparts were trained on all activities of pearl culture. This includes the surgical operation of mussels and the proper cultural procedure to be undertaken until the mussels will be harvested.
In the early stage, the trainees were slow in operation of mussels being new in the line. After regular daily operation, they were able to improve, minimizing the mortality after the operation and the expulsion of nucleus. It will be necessary to operate on more oysters in order to perfect the technique in pearl culture.
