In addition to proper tissue transplantation, good pond management is very important.
The water should have enough phytoplankton in it to cause it to have a light green color. If the color becomes dark green, the water is too rich with plankton, which might deplete the oxygen content of the water at night. If this happens, the water should be changed or diluted as soon as possible. Checking the transparency of the water is an easy way to estimate the amount of phytoplankton in the water. Normally, the water should be transparent to a depth of 30-40 cm. If the water is too clear, it is low in nutrients. If it is too turbid, it is too nutrient rich. The color of the water will indicate how much fertilizer to add and weather or not to dilute the water.
The ideal temperature range for culturing mussels is 15-28°C. Temperatures lower than 10°C will prevent the mussel from secreting nacre. Too high temperature, on the other hand, will affect the physiological functions of the mussel. Oxygen is also very important to the mussels. If oxygen levels are too low, mussels will die easily. The oxygen level is related to the stocking density and the amount of natural food in the water. If the mussel population is dense, oxygen will be low. Too much zooplankton in the water will also cause oxygen to be low.
A one hectare pond can support 45,000-60,000 mussels. If the density is too high, there will not be enough oxygen or food, and there will be too much mussel excrement in the water. The mussels will then become weak, stop growing and stop secreting nacre. The mortality will also be high.
During the culture period, the growth rate, the rate of nacre secretion and the mortality rate should be checked once a month. The clams and the culture baskets are also cleared of algae and other growth regularly.
Within 2-3 weeks after transplantation, the wounds resulting from transplantation procedure would have healed, but the mussels will still be weak. It is therefore easy for bacteria and parasites to infect the mussels. Pond management is especially important during this critical period. Dead mussels especially must be quickly removed. If dead mussels are left in the pond, infection will spread ti the rest of the mussel population, causing high mortality.
The culture period for freshwater pearls is 2-3 years. During the second and third year, nacre is secreted most rapidly. After the fourth year, secretion is slower and mussels are weaker. Pearls cultured for 2-3 years are very round and lustrous. Culturing for more than 3 years will not improve lustre; on the contrary, the pearls tend to become duller after the third year. Pearls cultured for just one year are small in number and size, asymmetrical and of bad quality.
The Chu-pei branch of the Taiwan Fisheries Research Institute stocks about 3,000 mussels in an area of about 10,800 square feet. The mussels grow very well, each mussel producing 1.1 g of nacre after the first year, and 3.7 g nacre after the second. In the south of Taiwan, because of warmer temperatures and an abundance of natural food, each mussel can produce 3 g of pearl in seven months.
The production cost for freshwater pearls is low as cheap and naturally abundant freshwater mussels and simple bamboo racks are used. Before going into this business, however, there are still several questions to consider.
Although the investment is marginal compared to other fish farming business, one must wait at least two years for a return on the investment. Cash flow for these two years must therefore be considered. In addition, implantation is a special technique depending on skill, experience, patience and concentration; suitable training in the technique must therefore acquired. Through good quality product and proper promotion, domestic and foreign markets may be developed.
In order to improve the quality of the pearls, close attention must be paid ti the quality of the mussels. If one needs to import the mussels from abroad, one must make sure the breed is compatible with local environmental and climatic conditions. If some other species of mussels, such as Hydriopsis schlegelu is preferred, one should research the breed in depth beforehand.
Overall, the most important step to improve pearl quality is to perfect the implantation technique. If the quality of production is ignored in favour of quantity, the entire crop will be inferior and unmarketable. It is important to be realistic and acquire he skills and the knowledge first before going into the business.
For more information, contact
#103 J. Abad Santos cor. Lopez Jaena Sts.,
Little Baguio, San Juan, Metro Manila
Tel: (02) 727-6205
Bureau of Fisheries and Aquatic Resources
Philippine Coconut Authority (PCA) Building,
Elliptical Road Diliman, Quezon City
Tel No. : +63(2)929.9597; 929.8074
Email : [email protected]
D.A. Compound, Elliptical Rd.,
Tel. Nos. (632) 929-6065 to 67 / 920-3991 / 928-1134
photo from purepearls.com