Pearl Culture

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Prepared for the Pearl Oyster Farming and Pearl Culture Training Course conducted by the Central Marine Fisheries Research Institute at Tuticorin, India and organized by the Regional Seafarming Development and Demonstration Project (RAS/90/002)

February 1991 Training Manual 8

PREFACEPearls, one of the highly esteemed gems, are very valuable due to the high demand and prices for them. Several countries bordering the Indian and Pacific Oceans and some countries along the Eastern Atlantic Ocean have pearl oyster resources. Many of these countries, particularly those in Asia, are very much interested in pearl oyster farming and pearl culture. Japan stands foremost in the two fields having developed technologies and innovations in the field. The techniques of pearl oyster farming and pearl culture are not widely known. There is a need to promote more widely the techniques and relevant information on the bionomics of pearl oysters. In India, interest in pearl culture began at the start of this century. Several studies have been conducted by the Madras Fisheries Department in the 1930s. In 1972, the Central Marine Fisheries Research Institute (CMFRI) took up intensive research on pearl culture at Tuticorin achieving a breakthrough in July 1973 when it produced free spherical cultured pearls by employing the mantle graft implementation technique. Since then intensive research has been carried out by the Institute on pearl formation, pearl oyster biology and ecology, and hatchery techniques for production of pearl oyster seed. Considerable information of applied value has been obtained. The development of the pearl oyster hatchery technology in India in 1981 opened the way for large and commercial scale culture of this bivalve species. Based on the technical know-how provided by the CMFRI, a company has been established at Tuticorin to produce cultured pearls. In view of the keen-interest shown by countries in the region, the FAO/UNDP Regional Seafarming Development and Demonstration Project (RAS/90/002) requested the Indian Council of Agricultural Research (ICAR), New Delhi to conduct a training programme on "Pearl Oyster Farming and Pearl Culture" at the Central Marine Fisheries Research Institute in Tuticorin, to train personnel from different countries. In line with this training course, this training manual was prepared. This manual deals with various aspects of pearl oysters, pearl oyster farming, pearl production technology, etc. The Manual is designed for technicians as well as entrepreneurs. The effort by Mr. A. Chellam, Dr. A.C.C. Victor, Mr. S. Dharmaraj, Mr. T.S. Velayudhan and Dr. K. Satyanaryana Rao in preparing and editing the manual is acknowledged. I would like to thank Mr. Chen Foo Yan, Coordinator of the Seafarming Development and Demonstration Project, and his staff, particularly Mr. Pedro Bueno, Mr. Alessandro Lovatelli and Prof. H.P.C. Shetty for further editing and publishing the manual. Dr. P.S.B.R. James Director Central Marine Fisheries Research Institute, Cochin, India National Coordinator Regional Seafarming Development and Demonstration Project (RAS/90/002)

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TABLE OF CONTENTSPREFACE LIST OF FIGURES LIST OF PLATES CHAPTER I Pearl culture in India 1.1 Introduction CHAPTER II Taxonomy and distribution 2.1 2.2 Distribution CHAPTER III Morphology and anatomy 3.1 Morphology 3.1.1 3.1.2 Shell structure 3.2 Anatomy 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 3.2.10 Reproductive system CHAPTER IV Biology and ecology 4.1 Biology Mantle Foot gland system system system system system system Shell features Taxonomy

Byssal Muscular Digestive Respiratory Circulatory Excretory Nervous

4.1.1 Food 4.1.2 4.1.3 Reproduction 4.2 Ecology CHAPTER V

and Age and


habits growth

Hatchery techniques for seed production 5.1 Artificially reared spat 5.1.1 5.1.2 5.1.3 Aeration 5.2 Live food production 5.2.1 Phytoplankton 5.3 Broodstock handling and spawning 5.3.1 Broodstock 5.3.2 5.3.3 5.3.4 Early development and larval rearing 5.4 Larvae and spat handling 5.4.1 5.4.2 5.4.3 5.4.4 5.4.5 Survival CHAPTER VI Pearl oyster farming 6.1 Selection of culture sites 6.2 Environmental conditions 6.2.1 6.2.2 6.2.3 6.2.4 6.2.5 6.2.6 6.2.7 Primary productivity Temperature Salinity Bottom Depth load current Larval Spat rearing conditions production Feeding Transplantation maintenance Spawning Fertilization Hatchery Seawater building management

Silt Water

6.3 Supply of oysters 6.4 Rearing methods 6.4.1 6.4.2 On-bottom culture 6.5 Rearing containers 6.5.1 Culture 6.5.2 Juvenile rearing CHAPTER VII Biofouling and predation 7.1 Biofouling organisms 7.1.1 7.1.2 7.1.3 7.1.4 7.1.5 7.1.6 Other organisms 7.2 Boring organisms 7.3 Predator organisms 7.4 Control measures 7.4.1 7.4.2 7.4.3 Predation CHAPTER VIII Culture system 8.1 Culture operations CHAPTER IX The mantle 9.1 Mantle structure 9.1.1 9.1.2 Marginal Mantle mantle isthmus Fouling Boring Barnacles Ascidians Bryozoans Molluscs Sponges of mother oysters Raft culture

9.1.3 9.1.4 Central mantle CHAPTER X The surgery 10.1 10.2 10.3 10.4 10.5 10.6 Surgery CHAPTER XI Pearl formation 11.1 Natural 11.2 Cultured pearl formation CHAPTER XII Post-operation culture 12.1 Culture conditions CHAPTER XIII Production of cultured pearls



Surgical Selection Graft Conditioning of tissue for

instruments Nucleus oysters preparation surgery



13.1 Development of implantation technique 13.2 Nucleus retention and pearl production 13.3 Pearl harvesting CHAPTER XIV Improvement of pearl quality 14.1 Measures for enhancing pearl quality 14.1.1 14.1.2 14.1.3 14.1.4 14.1.5 14.1.6 Tool maintenance Oyster Narcotization Graft Oyster of tissue selection oyster preparation Implantation convalescence

14.2 Colour of pearls APPENDIX I REFERENCES

LIST OF FIGURESFigure No. 1. World distribution of pearl oysters. 2. Section of the shell of Pinctada fucata. C.L.= conchiolin layer; P.L.= prismatic layer; and N.L.= nacreous layer. 3. Anatomy of Pinctada fucata. 1) Mouth; 2) oesophagus; 3) stomach; 4) left labial palp; 5) left inner labial palp; 6) crystalline style; 7) liver; 8) digestive diverticula; 9) descending intestine; 10) ascending intestine; 11) rectum; 12) anal papilla; 13) byssal gland; 14) nucleus implanted in the gonad. 4. (A) Culture raft constructed with teak poles; (B) A FRP styrofoam buoy; (C) A mild steel buoy, and (D) Oyster long-line culture system. 5. Section of oyster mantle. (1) Central mantle; (2) Pallial mantle; (3) Marginal mantle. I.F.= inner fold; M.F.= middle fold; S.F.= shell fold; P.G.= periostracal groove; and P.S.= periostracal secretion. 6. Steps in graft tissue preparation. (A) mantle tissue when removed from an oyster (p.m.= pallial mantle and m.m.= marginal mantle); (B) trimming of the margins to remove marginal mantle and inner muscular tissue; (C) further trimming to obtain ribbons of pallial mantle; and (D) cutting of the ribbon into small sections. 7. Process of pearl formation. (A) round and half natural pearls; (B) half cultured pearl; and (C) round cultured pearl with an artificially implanted nucleus.

LIST OF PLATESPlate No. I. (A) Pinctada fucata and (B) Pinctada margaritifera. Cont'd. (C) Pinctada chemnitzii and (D) Pinctada sugillata. Cont'd. (E) Pinctada anomioides and (F) Pinctada atropurpurea. II. (A) Inside view of the C.M.F.R.I. pearl oyster hatchery in Tuticorin, (B) Male oyster while spawning and (C) Pyriform oocytes. Cont'd. (D) Fertilized oocytes, (E) Early cleavage and (F) Morula stage. Cont'd. (G) Trochophore larvae and (H) Straight-hinge larvae. III. (A) Umbo larvae, (B) Eye-spot larvae and (C) Transitional stage.

Cont'd. (D) Pediveliger larvae, (E) Plantigrade larvae and (F) spat. IV. (A) A scuba diver diving to collect pearl oysters and (B) A culture raft floated with mild steel barrels. Cont'd. (C) A culture raft with FRP styrofoam buoys and (D) Oyster long-line culture. V. (A) A box-cage containing pearl oysters and (B) A frame netcage with oysters. Cont'd. (C) A netcage for rearing oyster spat of 310 mm in size and (D) Rearing netcage covered with velon screen. VI. (A) Fouling organisms on adult oysters and rearing cage and (B) Oysters heavily encrusted with barnacles. Cont'd. (C) Damage caused by a boring sponge and (D) Cymatium cingulatum, a major pearl oyster predator. VII. VIII. Pearl oyster surgical instruments. Implantation of a pearl oyster. (A) Opening of the oyster valves and (B) Insertion of the graft tissue. Cont'd. Implantation of a pearl oyster. (C) Implantation of the nucleus, and (D) General view o



Pearls have been known to mankind since the beginning of civilization. They are highly esteemed as gems for their beauty and splendour. These structures are secreted by the mantle (i.e., the skin) of pearl oysters in response to irritations caused by external or internal stimuli such as sand grains, molluscs eggs, parasites, detritus, and other foreign particles. Many attempts have been made to culture pearls in freshwater mussels. In the 13th century the Chinese fixed small Buddha figures inside freshwater mussels which