Five different teclmiques arc used in mussel culture (1) Sea bottom culture (2) Pole culture (3) Rack culture (4) Long line culture (5) Raft cultur

Kuriakose, P S

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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 \ • TECllro!..OGY OF }fJSSEL CULTUR" P.s.KURIAKCEE Five different teclmiques arc used in mussel cultlre (1) Sea bottom culture (2) Pole culture (3) Rack culture (4) Long line culture (5) Raft culture . Sea bottom culture This teclmique is widely practised in NethClI'lands and in a numba:' of Etropean courItrios including Denmark and W.est Get-uany. The principle of bott om culture is the transfClI' of seed (]I' juveiirl.le IlIUSsels from areas of gr eat abundance where growth is very poor due to over-crowding t o areas whOre mussels can grow fastClI'. The basic r equirancnt fer this teclmique is a firm substrat um fr oe from drifting sand and mu:i particles. Seed IlIUSsols arc dredged from public grounds and laid first, on shallow grounds wht:r e thCly will grow. They arc later transferred to deeper grounds for fattening . Mussel farma:s sow a thick layer in the shnllow grounds. When the mussels roach a length of about 25-1) mm they are thinned out by transferring the exccss pcrtion to deeper areas .for fast growth rurl fattening . · When IlIUSsels are 2 to 2t years old they at tain a size of about 60 to 70 mm and 1.9 r eady fer rorvest. The mussels are dredged and dumped in a thick l ayClI' in an aran of little tidal mov(lJlcnt free fr om drifting sand. They are left for 4B hours to rid thansol V3S of silt. The chief advantage of bottom culti vntion ~s th'lt tho IlIUSsels always r emnin undar watat' and therefor c feod l onger . The main drawbacks are expos 'Jr' c to bottom pr edator s l ike star fishes and crabs, and· need to cleanse tho mussols of silt . Pole cultlre or Bouchot method of Pole culturo :i.s the cil.dest and principal methoclLmuss el farming in Franc o . In this met hod mussels are gro1Oll on rows of poles in the intertidal area . The extrane tidal r ange i s advantageow to mussel grower. Muss ol seeds cr spat are collected on spat collector - C ' pales closer to the land . The poles are 75 cm apart, am are set in rows at right angle to the shore . The seeds are attached to the rearing pales in bags of fine netting which lI'ot and fall apart after t he mussels attach themselves t o the poles, by byssus threada . A13 the mussels groo,1 hCly!!I'e thinned out arrl transferred to other rearing posts . Another ' seed collection technique r ecently practised i~· :&anc e involves susperrlfug loosely wo~ I'"opes 13 mm in diameter and 3 metre long in t he i¢er ti dal region near natural beds . Within 3 'leaks a fter spmming s eed mussels of about 5 to 10 mm size att ach themselves in the crevices between the strands of t he ropes . " The ropes are then wrapped around pales driven in, the inter- tidal flats . The }X"0codtre is similar to the traditional IOOtlxld. The mussels are thinned out periodically as they grow and wrapped round other pales., By the end of second year' the mussels are harvestod, and marketed after reaching a size of about 5<Atm . The average }X"oduc-tion i s about 25 'kg of mussels each year fer every pole used and per hectare yield is about 4.5 tonnes per year . The main advantage of pole culture is that the mussel s are less eJIPoscd to tho bottan living predatery crabs and star fi.shes . , . Predation is further r educed by t he adoption of plastic sheaths around the base of tho pale . The main drawback however is that, the mussels are eJIPoscd at l ow tide especiaJ.J.y on spring tide . The poles are vulnerable to storms . Rack culttr e Hussel far!J:i.ng on r acks is practised in Italy . Though the mussel farmors do us·; nrussel seeds which s ettl e natU'aJ.J.y on rocks a!ld other h!!I'd substrates as prinRry materials by far the largest part of the seoo r equirement is met fr om nrtific:illl collectors . In the shclterod area ,1lleI'C the mussel farming is practised, the bottom is predominantly s oft and IIIUl.dy . The mussel f arJOOrs construct parks comprising net wcr ks of poles connect ed with horizontal ropes . From thus e ropes t hey swpend strings of mussels which are permanentl y :In sea water ab ove the bottom. A special type of rope is stretched - :11 -• around the park to collect the seed . Gt-ol;th is very rapid and tru mussels will be ready far harvest when they attain ,:1 size of 100 mm. Long line cultur e The l ong line method of mussel farming was introduced very recently in M opa . This matlxld is very successful in optn sea mussel ---farming. Long lines are 50 to 75 metre l~ng and consist of a pair of ropes strung betl,ICon two parallel pair of metal, wooden or st~pfoam floats. Each c.'1d of t he li"le portion is' (some times the middle also) I' is anchored. Floats are spaced 3 to 7 metr es apart. Mussel seeds are collected fr om natural beds a'ld transplanted on the ropes and suspended from lines about 0 .5 metre apart . The growth in this system is very rapid. Raft culture or suspended culture The r aft culbre technique has undergone great developmoot in r ecent years offering the best prospects f<r farming of mussels in sheltarod and OPE!'! coastal wuters . This method is genErally used in watars more than 3 metres deop. The modern r afts eanmoruy have four or m<re large ..,coden floats covered wi}h cement or fibre glass --- -to protect the wood from marine bcrers. On _the top: of the floats fr= work of 'Aooden beams are prOvided, about 50 to 60 em apart , fr om which the ropes fTe hung. T'ne r a ft is usually fitt ed: with a werking dock and shcl.tcr fer the oparaters . The size of the raft varies but an avero'";) r aft is 20 x 20 metrea and will accOlllliodate 500 r opes . Reci"ntly large-scal~ ~aters have constructed mOl'e rugged rafts :lbout 700 sq .m fer usc in dcepar and exposed lBters. m Such rafts can hold 1000 ropes and are s trootined to withstand strong currents. During the peak spawning period empty fibrous ropes arc hung -fran the rafts for collocting spat. The r opes are s oon crowded with young mussels. The mussels e,"I'OW rapidly and gen<rilly r each a si,;1;e of about 30 to 40 mm within five months . Thinning is done when the .> '. - }';:. -mussels are 25 to 30 mm l ong. The mussels are r emoved from the ropes and bound on to new r opes using thin l arge meshed cott en or r ayon notting . (he "Scrttlement" or "Collector" rope yields enough ---- - . mussels fer twelv9 to fifteen new r opes i Seed nrussels gat:her ed fr om the inter tidal r ocks· ar e wrapped round ropes and suspenElled ·fr om t ho r l1.fts. . At every 30 t o 40cm length • a wooden peg o f about 12 llIIl s quara is inserted between the strands on each r ope to prev'ert mussels from sliding . Whm the mussels reach · 11 si zc of 70 t o 90 mm they are harvested. A nrussd cult U'e raf't; of about 250 square metr~ SU' face area can hald 400 ropes. . . (he hectare arm. in the sea can casily accommodat o 30 such rafte with l?, OOO ropes. Ihe average production per rop e of 8 metres lmgth is about 30 kg of mussels . (In India experimental mussel cultU' e farms are mainly loca-ted in the coastal waters up t o a depth of 10 metres . Only raft @1tur~hod is fallowed . A r aft of the size 8 x 8 metres can • • sa faly hald up t o '100 mussel r opes . Teak-wood <r casurine poles are us ed for the mrin fr ame work ani bamboo poles far mare strength and suspending t he mussel r opes. Sooled ani anpty metal drums or high density plnstic drums arc . used ns floats. The r aft is aneharoo with 3 iron Mchers each of 100 kg weight. Knitted c~ton eloth having 0. mesh size of 5 rom is u!>ed for seediilg . t:rCMth ~ mussels is very quick at t aining mnrJ-::Jtable size of 75- 80 mm in 5 months . In the case of br own mussels t he harvest size of 60 mm is r cacmd in 8 months . I 

Technology of mussel culture

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Technology of mussel culture

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