Freshwater Pearl Production Integrated With Ornamental Fishes: For Profit Motive Aquatic Fish Database est. 1991

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1D.Linga Prabu, D., 2Arun Sudhagar, S and 1Ferosekhan, S.

1PG Scholar, Fish Nutrition and biochemistry Division

2PG Scholar, Aquatic Environment and Health Management Division

Central Institute of Fisheries Education, Mumbai, India






Integrated farming may be defined as a sequential linkage between two or more farming activities. The basic principles involved in integrated farming are the utilization of the synergetic effect of inter-related farming activities and the conservation, including the full utilization, of farm wastes. It is based on the concept that "There is no waste" and "waste is only a misplaced resource which can become a valuable material for another product (FAO, 1977)".


            Integration of fish-freshwater pearl mussel is practiced in Taiwan. It is not only an efficient way of recycling farm wastes but also produces high economic returns from ornamental fishes as well as from freshwater pearls. Fish excreta and other organic suspended materials are efficiently utilized by freshwater mussels hence, reduce water pollution and the waste becomes pearls. And also the freshwater pearl mussels can utilize the space in ornamental fish farm, without affecting the ornamental fishes.



            Pearls, especially those with a good lusture have been among man's favorite gems since ancient times. With the advance of scientific technology and the rising standard of living, pearls are now used in make-up and medicine. The result is that pearls have become even more precious, with the price rising remarkably. Today there is a great demand for cultured freshwater pearls and China produces 95% of freshwater pearls sold in the world market.


Important culture species of freshwater pearl mussels:


Triangle sail mussel                      -           Hyriopsis cumingii

Wrinkle comb mussel                    -           Cristaria  plicata

Indian Freshwater mussel            -           Lamellidlens marginalis

Freshwater pearl mussel              -           Margratifera margratifera


Distribution of freshwater pearl mussels:

            Fresh water pearl mussels are lived in lakes, rivers, fish ponds and irrigation canals. Typically it occurs in flowing waters with slightly firm and mud or mud bottom. It also can live in areas that have slow currents.


Feeding habit:

            Fresh water pearl mussels are filter feeders, removing phytoplankton and other suspended particulate matter from the water.


Life cycle:

            Mussels have a very unique life cycle. In order to maintain, mussel larvae (glochidia) need to attach to a fish and use some of the fish's energy to develop internal organs. They do parasitize the gills, fins or other external structures of fish, but usually don't hurt it. After a few weeks, the mussels drop off the fish and are now juveniles. Blue gill sunfish, Lepomis macrochirus, juveniles of salmonids and Oreochromics niloticus are the important host fishes of glochidia larvae. The juveniles can live by themselves in the substrate, eating algae and bacteria, and eventually grow until become adults.


From Pest to Profit:

            In actual fact, fresh water mussels are really a nuisance to fish farmers when they invade their fish ponds. The adults compete with cultured fish for oxygen and freshwater plankton which comprises their food. Mussel attaches themselves to the gills causing young and weaker fish to die. But because the epithelium of the mantle margin of freshwater mussels recreate a substance called nacre, the utilization of technology to implant  pieces of the epithelium in these mussels can result in the production of pearl farmers have thus been able to take a and use it to create a profit — making industry.


Suitable species for pond culture of ornamental fishes:

            Among the various ornamental fishes the koi carp varieties like kohaku, snake, showa, Bekko, shusui, koromo and Tancho are the gold fish varieties like common gold fish, shubunkin, fan tail, comet, veiltail, telescope, Moor, oranda, lionhead and celestial are reared in the pond ecosystem. These fishes are omnivorous and hence they feeding variety of feed items and have no dietary preferences. In commercial culture they are fed with artificial pellet feeds and flakes.


Integrated culture method:

            There are basically two methods of culturing pearls. One is scattering method another is net suspension method.


Scattering method:

            It consists simply of distributing the mussels in the pond where the part of water is derived from the ornamental fish pond through the central drainage outlet. This water contains lot of suspended organic material, faeces of fishes and plankton etc. This water mixed with adequate amount of pollution free aerated water in the freshwater mussel culture pond. The removal of suspended organic matter and algae through their filter feeding habit in the water derived from the ornamental fish farm.  Hence, the freshwater pearl mussels serve as biofilters or living filters. There by mussels reduce the utilization of water and recycling the waste. Mussels are collected by the nylon net screen fixed to check the entry of invading menaces such as crabs, fishes, macro vegetation etc. from the primary feeder canal. Since the seeds are collected from natural habitat it is impossible to segregate the sex. Because of this inconvenience, integration by this method additional requirement of land hence it is applicable where the abundant land facility exists.


Net suspension method:

            Net suspension method uses stainless steel wire mesh baskets to suspend the mussels in the water column of ornamental fish farm. The stainless steel basket can be kept in the water for 2-3 years before deteriorating. The baskets are 40 x 60 cm in diameter. A piece of netting is used to divide the inside of the basket into two levels, from which the mussels are suspended. The net has a mesh size of 2-3 cm netting is also used to wrap the steel basket. The baskets are then suspended at near bottom of pond, from the racks made from bamboo. The racks should be positioned in the central part of the pond, in case of fixed basket method and the pond designed in a manner to accumulate the wastes at the central position for efficient utilization of wastes by the mussels through their filter feeding habit. And if the organic load is very high the water should be drained out through the central drainage to another scattering method of mussel culture pond. The large fish ponds normally has the central parts as a waste / arid area since, the feeding and other activities are predominantly prevailing in the sides and around the central part of the pond. Hence, the central portion is utilized for mussel culture which reduces the additional requirement of land and water. The racks can be of floating type which is used in large ponds and reservoirs where the racks float in the entire pond and utilize the plankton rather organic load except the suspended materials.

In net suspension method hatchery raised monosex or triploid mussels are stocked to avoid unwanted reproduction in culture pond during culture period. The devoid of reproduction helps to prevent the culture fishes from glochidia infection and also considerably regress the energy wastage through reproduction. As this method needs additional cost for seed production or procurement of seeds, but is an effective method for places with land scarcity.


Captive breeding:

            Sex is separate. No sexual dimorphism. The matured conditioned males and females are kept in the same breeding tank and a slight rise in temperature of water by 30C above the ambient temperature induces spawning of mussels (thermal shock). The sperms are shed into the supra-branchial chamber and are passed out through the out going water. These sperms are taken into the inhalant siphon of the female by chance. The ripe eggs fall from the ovaries into the mantle cavity and then pass into the cloaca through the supra Đbranchial chamber. The eggs are fertilized in the cloaca and the fertilized eggs pass into the space of the gill chamber where development takes place.



Glochidium larvae:

            The zygote undergoes cleavage and develop first into a blastula and then into a gastrula. The gastrula finally develops into microscopic larvae called glochidium. It means "The point of an arrow". It lives in the water tubes of gills of female mussel. The size is about 0.1 to 0.5 mm wide. It is covered by a shell with incurved. The larvae feed on the mucus recreated by the gills of mother mussel. The fully matured larvae are passed out through the outgoing water. Then, they sink to the bottom of the pond. Further development takes place in a fish provided in the breeding tank. When a fish comes in contact with glochidium larvae, the larvae is attached to the fish and encysted by an over growth of the skin of the fish. The larval undergoes metamorphosis during its encysted ectoparasitic life. After metamorphosis the tiny young ones come out by the rupture of the cyst. It sinks to the bottom and developed into an adult. It is estimate that the survival rate from release of glochidia to juvenile settlement is well below 0.01percent in natural environment.


Culture of glochidia in artificial media:

            The glochidia can be cultured in artificial medium at 23 ±20c temperature. This media contain a mixture of M 199, fish (Oreochromis niloticus) plasma as a protein source, and antibiotic or antimycotics at a ratio of 2:1:0:5. The duration of glochidia development until the juvenile stage is 9-10 days in this media. After 1 month of controlled feeding with phytoplankton, the juveniles showed an elongate of shell with several growth lines. Survival from glochidia to juvenile stage is upto 85 ± 4% in fish plasma.  The transformation of glochidia to juvenile stage is upto 84 ± 3% in plasma.


Culture of Juvenile mussels:

            The juvenile mussels are cultured in a separate large tanks / smaller size ponds until they reach the adult stage. The juveniles are provided with adequate amount of phytoplankton for its accelerated growth. The matured mussels are used for pearl production through implantation.


Implantation procedure:

            The mussels from which the epithelial implants will be taken are collected and put in buckets of clear water to flush them. First, the adductor muscle is cut so that the shell may be easily opened. A pair of scissors is then used to cut strips of epithelial lining between the inhalant siphon and the adductor muscle. The epithelial strips are placed on the hard wooden board and the connective tissue is cleaned off the back of the strips. They are then cut into 3-4 mm long and 0.5-1mm thickness of prices.


            Healthy mussels are selected and put into a vise assembly that will force the valves open 1-1.5 cm apart, are made in the epithelium of the marginal zone. The previously cut epithelial pieces are then inserted into the holes, about deep, making sure they are firmly in place. About 25-30 slices can be transplanted into a mussel of 10 cm in length.


Care and culture of operated mussel:

            Operated mussel can be held in net bags, net cages and folders. Operated mussels should be reared in the water bodies free from pollution and disease. The water should contain adequate phytoplankton for its growth. The ideal temperature range for culturing mussel is 20 -300C. Temperature <100C will prevent the mussel from secreting nacre. If oxygen level is too low (<3mg/l) mussels will easily die. With in 2-3 weeks after transplantation, the wounds resulting from transplantation would have healed, but the mussels will still be weak. It is therefore easy for bacteria and parasites to infect the mussels. Dead mussels should be quickly removed. In the presence of any dead mussels in pond, high mortality is observed through spreading of infection.


Quality of Pearls:

            In order to stimulate more rapid secretion of nacre, the mussels should be suspended 20-30 cm below the water surface. The culture period of freshwater pearl is 2-3 years. About 6 months before harvest, they are lowered to 80-100cm  below the surface. Although during these last 6 months, the nacre will be secreted more slowly, the pearl will become denser and its colour lusture will improve. Culturing for more than 3 years, the pearls tend to become duller. Pearls cultured for just one year are small in number and size, asymmetrical and of bad quality.





Even though fresh water pearl production along with ornamental fish culture has much of benefits, which has some limitations too. While the mussels integrated with ornamental fishes, if it reproduces, the glochidia cause severe problems to ornamental fishes. To overcome these problems, the possible ways are,


(1)   Only one sex either male or female mussel used for pearl culture in the integration with ornamental fishes.

(2)   Triploid mussels can be used for this integration. Triploid mussels being a sterile animal; they could not reproduce in their life. (In fresh water pearl mussels tetraploid and triploid are reported in wild conditions by several authors and triploid mussel production technology is also established.)



            The culture of fresh water pearl mussels and ornamental fishes in the same pond improve the productivity and reduce the space requirement. It also minimizes the water requirement. The freshwater pearl mussels consume the excess amount of algae available in the fish pond and there by protect the pond from algal bloom formation. It reduces the feed cost of the freshwater mussels. And water exchange from ornamental fish farming is also minimized considerably by this integration which ultimately lowers the cost for power utilization. Fresh water pearls produced through this implantation method utilize the pest (F/W pearl mussel) to make profit by recycling the organic waste. If the seeds collected from the primary feeder canal through the screen, it is advisable to go for scattering method of culture where no contact between fish and mussel. The scattering method is possible if the farm yard with adequate land facility. The net suspension method is advisable for monosex or triploid mussels which produced through captive breeding not by natural collection. Here seed cost is also included as additional while comparing with the other method.   The farmers should earn additional income through the pearl production along with the ornamental fish production.


Literature cited:

1)     Taylor, J., 2007. Captive breeding and juvenile culture of the freshwater pearl mussel, 5 m enterprise Ltd., 4, Haywood house, Hydra business Park, Nether lane, Sheffield, England, 404 (1).


2)     Dan, H. and Ruobo, G.  2002. Freshwater pearl culture and production in china, Fresh water fisheries Research center, Chinese Academy of fisheries science, Chine. 7(1).

3)     Nair, N.C., Leelavathy, S., Pandian, N.S., Murugan, T. and Arumugam, N. 1997. A text book of invertebrates, Sara publications, Nagercoil, TN, PP 306-319.

4)     Hastie, L.C. and Young, M.R. 2003. Conservation of freshwater pearl mussel I: captive breeding techniques, conserving Natura 2000 rivers conservation techniques series No.2 English nature, Peterborough, SNIFFER 2003.

5)     Ahilan, B., Felix, N. and Sanjeeviraj, G. 2005. Integrated fish farming, Dept.of aquaculture, FC & RI, TANUVAS, Tuty -8. pp 82.

6)     Uthaiwan, K., Nopaxatnaraporn, N. and Machado, J. 2001. Culture of glochidia of the freshwater mussel Hyripsis myersiana (Lea, 1856) in artificial media, Elsevier science, B.V. Publishing.

7)     Tom and Lew, Fresh water pearl culture, 2008. Bureace of fisheries and aquatic resources, Entre pinoys Atbp, word press, Philippines,

8)     Lowery, L.R. and Dimock, R.V. 2006. Encapsulation of attached ectoparasitic glochida larval of freshwater mussels by epithelial tissue on fins of Naive and resistant hast fish, Biol.Bull.210.51-63.

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