Good numbers of clams are at present cultivated in a number of countries. It my be seen that clam/cockle culture is extensively practised in Japan, Korea, Taiwan, Malaysia and Thailand

Narasimham, K A

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• i . • • REFERENCE 0 Nly SUI-IMER INSTITUTE IN \ CULTTIRE OF rnIBLE MOLLUSCS HELD AT TurrCCRIN RESEARCH CENTRE OF CENTP.AL l-I.ARINE FISHERIES RESEARCH INsrITUTE trom 26 May to 24 June 1980 ,. , . ~ Centr a l ~!arinc Fis her ies Research Institut e P .B . 1912, COGHill - 682018 , I NDIA " Indian Council of Agri cult1Z'al Resoarch September' , 1980 \.If \ .. 1 • . .. TEX:HNOLOGY OF CLAl1S J.2ID COCKLES. CULTURE K .A. NAHAS IMHAM Cultivable species Geod number of cl ams 1l!'e at present cultivated ~ munber of cOUlltriest It my be seen that clatn/cockle culture is extensively L(Table 1) practised in Japan, Korea, Taiwan, 11a.laysi a and Thailand. True cockles belonging to the genus Cardium ar~ not commercially cultured but the blood cla'll Anar1..ara f'Fanooa which is referred to as cockle in the soutlreast Asia n countries is extensively cultured. In OIl[' country, apart from t he 4 speoies given in the table, Katelysia opirnn a nd Vallorita c:yprinoides var cochinensis have the potential for farming. Induced spawning ood.. hat chery pI' oduction of seed The procedure i s popularly lmown as the Milford method (Bardach et l&., 1972 ) and i s the s Dllle as followed for oysters. In short the adult clams are held at 10 'C and 1l!'e condi;tioned far spawning by slowl y raising the temperature to ab out 1S'C. For 2-4 weeks t h e t enp erature i s nnintained at this ~evel depending upon . t he time of the year . Then it is r aised to 25 ' C whicli induces spawning . The larne ore r eared in the hatchery supplied with steri-lised water . Alp l cultures of Monochrvsis l utheri !lIld Isochrysis galbana are givG.'1 l!S f e ed . When the larvae are ready to settle "hey are tra!1s fcrr ed to l 'r ger settling t~s for r eari ng the Sj:flt • fly this method t ho qU3hog, Mercenaria morconarin wa s spawned in' the lj :3. and the s eed r aised . A great advant age of this method is that the clams can be induced to spawn at any t ime of the year which would er.mr e continuous seed surPly. Se~ collection The size of t he seed collected fran t he wild varies even for tr.e same species at a gi vE!1 localit y depending upon the time of ccllection. In Taiw= (Chen, 1976 ) W!1(l[' O t here is a practice of • r - I I! ..J •. nUl'sery r aving of seed, seed measuring 0:5 mm length arnrards or':) collected. oth€l'wise for most of the commercial species 5. 25 DIm seed are collected. The oC]uipments requ:ired are a spade, r ack cr any implement suitable to dig the top l ayer of substratum . In mud ' . . flats, for Anadara seed, a small lr.nd net ,lith nylon mesh netting is -scooped in the mud or operat ed from a boat. Propuls ion on mud . flats may be 'on a 'wooden pla nk with one foot pushing through the ~trl while kneeling on t he pla nk ;lit h the other l eg. Sieves are used to separate the seed. &md picking is a common practice for slightly larger seed . Also a cont ro.ner like a bamboo basket, wooden box, trough etc.,is carried to hold the seed collected . Seed callect ion is usually dono at low tide . Nursery rearing of s eed .~ -- "- . In Taiw:m t iny seeds (about 0.5 mm in length) of Mcret.r.ix l.uscria iU'e gathered from sa n:J.y fl ats in tidal areas by sieving the substratum (Chen, 1976) . They are stocked in milk fish ponds at 30 to 50 mill~on per hectere . Bnmboo sticks ere planted to serve as merkerD. If the product~vity in the pond is poar fertilisers like night s oil, hog = ure, chicken droppings, rice bran etc.,are applied. Pr·edat cr s arc r emoved periodically. After about 6 months nursery rearing they are harvested (s1%'vival 5()..60%) and sold far. stocking in clam farms . Similur nursery managanent of the seed clams of ! . . gr:MOS:J. is in vogue in Taiwan (Chen, 1976) wh€l'e tiley are reared fer a f el'l montp.s in mud fl~t enclos1%' es (erea 0 .1 to 0 . 3 ha) made of nylon netting supported by bamboe sticks . Site selection The cl :.un f.:lI'ms ar e locat ed in estuaries , bays and other sheltered FlI'CQS cles e t o the share having tidal influence. About 1-2 h e:xposure at each 101, tide hus the obvious advant~ of managing the farm ;lith ease . Too l ong, an e:xposure r esults, in poar growth due to reduced feeding and my cause mort<llity due to desiccation . Farms . . ' \ located farther in eub-tidnl area have thil disadvantage when preda-t<rs are to be eradicated . Clams arc rarely gr'own in ponds. In Taiwan (Chen, 1976) Mer etrix lusoria i s grown in ponds f<rmerly used fer milkfuh and als o in the outlet :llld inlet canals of milk fish ponds. The type of substratum preferr ed vnries with species cultU!'ed . For example Meretrix sp.,thrives Hell on sarrly bottom while Anadara • granosa prefers I!IUd flats containing upto 90% .silt . Also the range of salinity t olerat ed differs. FeH ~pecies tolerate prolonged low saline. conditions which are generally prevalent in areas subjected to heavy rains (I[' fr esh water drain from, the land . Clam farms should be located in areas where there is little wave action . Areas prcne to frequent changes of contmr and liable to pollution should be avoided. It is also desirable thcl. the clam seed is available close to the farm sit e • FiJuipment Very little equipment is requiX'ed f(l[' clam farming . Bamboo sticks are plant ed t o indicate the farm area . The mc.;ements of the clam are limit ed and fencing is not necessary. However synthetic. fibre nets ar e sometimes erected as in Taiwan (1976) and U.s).. (Bardach ~ al ., 1972) t o JI'event th ejr escape with the water current and/or to keep t he prodatars (crabs and fi1f1) mm.y . A watchman's shed am a bamboo r aft (I[' D. boat fer transpl1l.nting, harvesting and inspec-tion ore r equir ed depending on the s ize and location of tl).e form. Farming the cl ams for morket The gr'ound should be levelled alTd cleared of predat(l['s. The clam farm is gener all y stocked at high tide . The seed JIIay be sown fr om boats, taking car e to get even dispersal . Any irregularity observed in t hc distribution is set right at the next law tide . The ' stocking ·density varies generally depending upon s eed availability and the speCies cul tlr ed • In the case of ! . granosa . in Malaysia it . . 2 . JIIay r each 1000 t o 2000/ m and this may be thinned mere thM. once to .. 102 -,:. , . achieve 0. i'inal dcnsit y of 300 to ' 600/m 2 (Bardnch et al., 1972). The duration of the culture depends upon the species and the country where grown. !:!. mGt'cenaria when grown in ncrlharn waters of U.s .A. takes 5-S yoors to reach marketable si ze and the sama species when cultured , ~ F.lorida could be IJl3I'ketcd in 2 years (Bardach ~ & ., 1 '172) . Simil.:lI'ly! . I?l'anosu is cultured far .. 2 years in Taiwan, 8-9 months in Ihlaysia and at Knldnada it was harvested after 5 months cult\re (N:l.I' usimhum, 1900 •. Farm management and harvesting The natural enemies of the clams are the boring gastropods, starfishes, crubs, skates ani wild ducks . Therefore 0. close watch " for preduta-s is remunerntivc. The farm needs very littlc maintenance job . In clam cultUre fertilisers and feeds are not used. Care ' should be takEn to prevent poaching . lfru'vcsting is usually done by hand . SOIOO of the implElllents used in seed collection are EIJlployed in harvesting • . A dredge may also be used. The yield by clam culture varies widely in different countries, being invariably low in temperatc countries. Fa- ex::unple the prodmtion of ! . granosa is less than a tonne/ha/year in Taiwn, 20 .7 tonnes/lta/year in Kllaysic. and at Kakinada 0. very ldgh produdtion of 3S5. 3 kg/1 0()n2/5 months was obtained at a Stocking density of 140/ m2 '( ;>larasimham 1900) . In Malaysia usually clams are stocked, 300 to 600/ m2 . Economics • lAta on cost be.'lefit studi es are available fa- a few clams . In Malaysia a 16 ha Anadara farm showed a gross profit of 6333 to 7600 US dollars (Fisheries Division, 1972) am in Thailam a 1 .6 ha farm gave a net r eturn of 147S US dollars (Sribhibhadh, 1972) . In Korea the net income fran a 50 ha hard clam farm was estimated at 6S70 million wons. J ( I / • I • - 103 -Clam cultL () prOSp flC .... S in India en bottom clam cultJre is fairly simplll. ExperimElltal culture on the ' on bottom culture' of various clam species being 'lD'ldertaken at the Central ~hrine fisherie's Research Instituto . . .-indicat es that t he clams grow very fast and reach marketable size , . in 5-6 mcnths ond their prcxiuct10n per unit area is very high. As is t he case wit h oth(r I edible molluscs, clam culture offers imnense scope for coastal aqmculture. \ -:-, • I· :. It- , . ~ : .. , ~ ., .1 I'" ' ,1-; -' !!j i I 1-• -1°4 -Table 1. ImpOl"'Gant species of: clams ~_d cockles cuJ.tur ad ----------------Scientific name ------~fer etrix mer etrix t!.~ M. ~ var ~ Vanal" upis sem:tdooussata :y; dSlCussata y. i apanica Tapes . j'apanica Mer8enari.a mercenaria -Anadara granos a !. broughtoni .. !. ganosa bismansis Popular name Hard cla m Great clam Backwat or Clam • Family Veneridae " II " " " II " " , Littie neck clam II Short n ecked clam II ' .J. , i Hard clam, quahog Cockle, blood clam . , " II Arcidae " II " II " " " ------------------ - - - - -Country where cultivated - - - -Taiwan Jildia Kar ea . Japan Taiwan Jildia, -Jildia / Japan Partugal Karea Japan U.s .A. Malaysia Thailand Vietnam Taiwan Pbllippines Jildia . Japan Japan Extent of: developmEnt Area Ulder cuJ.ti-_ _ 'V!ot ,!o.!,l Extensive Experimental Extmsive Extensi v e Extensive Experimental Experimental Extmsive Moderate Extensi ve Extensi v e . Limit ad ext. EDt Ext ensi v e '. Extensivo , Mpderat e Moderate ExperimEntal Moderate Moderate --------3396 ha '5799 ha -888 ha 2000 ha 625 ha 200 ha -------------..,.. Ref:erence - - - - -Ling (1972) Of:fioe of: Fisherios ( 1972) Ling (1 972) Cllm (1976 ) '-~ I' . Ling (1972) . ,' r--: Karringa (1 976 ) Of:fic e of: Fis heries (1972) , -'- - . Bardarch at a1 (19722. I~erson (1976 ) : Fisherie s D:i:vision(-, 972-) Sribhibliadh (197~ ) Ling (1 972) -'- -. ' . Chen (1976.) __ _ _ Bardach at a1 ((972)-- --- - . .. -.~. -- -Ling (1~,72), Ling(1972) --------:! -.-..... -:.;;" ;-, .~.~. 

Technology of clams and cockles culture

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Technology of clams and cockles culture

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