Mussel farming has a long history that dates back to the thirteenth century. Mussels are farmed in many

areas of the world with the most common species cultured being the blue mussel, Mytilus edulis. The main

producers of mussels are countries such as China, Korea, Spain, Netherlands, Denmark, France and New

Zealand. In 2012, 1.829 million tonnes of mussels were produced worldwide valued at 2.053 billion US Dollars

(FAO). The Indian mussel production is relatively small and the production is around 10,000 tonnes for the past

few years

Asokan, P K

Mohamed, K S

Sasikumar, Geetha

CMFRI Digital Repository

41Winter School on Technological Advances in Mariculturefor Production Enhancement and SustainabilityIntroductionMussel farming has a long history that dates back to the thirteenth century. Mussels are farmed in manyareas of the world with the most common species cultured being the blue mussel, Mytilus edulis. The mainproducers of mussels are countries such as China, Korea, Spain, Netherlands, Denmark, France and NewZealand. In 2012, 1.829 million tonnes of mussels were produced worldwide valued at 2.053 billion US Dollars(FAO). The Indian mussel production is relatively small and the production is around 10,000 tonnes for the pastfew years.In India, mussel culture (Perna viridis) is becoming popular in the Malabar area since 1996 following thesuccess achieved by CMFRI in rearing and popularizing green mussel in the backwaters. The simple methodsemployed for mussel farming was transferred to progressive farmers who took up mussel culture in thebackwaters.  Soon they found the venture profitable.  Demands came from new entrepreneurs for training andmussel farming spread from Kasaragod to Ponnani.Mussel culture in the backwaters of Kerala was first started in Padanna and Cheruvattur Panchayats inHosdurg Taluk of Kasaragod district.  Later it was taken to Elathur in Calicut district and Vallikunnu and Ponnaniin Malappuram district.Initially this low cost technology of farming was transferred to five groups with 15 to 21 members atCheruvattur and Valiyaparamba. Financial assistance was provided by the North Malabar Gramin Bank andCheruvattur Farmers Co-operative Bank.  They provided a loan of Rs. 2,60,200/= for the implementation ofthe project with a subsidy component of 50% subsidy.  These groups harvested 67.4 tonnes of mussels duringMay-June 1997. A portion of the harvested and shucked meat (2000-Kg) was sold to the Integrated FisheriesProject, Cochin at a rate Rs. 45 per Kg.  The remaining harvest was sold in the domestic market. The groupscould realise Rs. 3,34,555/= from the harvest with a net profit of Rs. 1,04,455/= within a period of 6 months.Many culture techniques are used for growing mussels worldwide and the most popular are describedbelow:Mussel Farming Methods and theProspects and Problems in IndiaP. K. Asokan, K. S. Mohamed and Geetha SasikumarCentral Marine Fisheries Research Institute,Ernakulam North P. O., P. B. No. 1603, Cochin - 682 018, Kerala, India42Course Manual1. Bouchot or Intertidal Pole CultureIn France, mussel culture is believed to have started in 1235, when an Irish sailor Patrick Walton surviveda shipwreck on the Bay of Aiguillon. He found that the wooden poles and nets that he had kept for trappingbirds attracted mussel spat settlement.  This became the basis for Bouchot method which is the oldest and themain method utilised in France on the Atlantic and English Channel coasts. This method, well suited to the largeintertidal mud flats facilitated the development of the blue mussel (Mytilus edulis) industry in France (Gosling,2007). The Bouchot method extended to other suitable intertidal areas along the Brittany and Normandy coast.The spats are collected on spat collecting ropes made of coir. These spat bouchots are situated offshore andconsists of parallel rows of poles with horizontal coir ropes for collecting seeds.When the seed are a fewmonths old, they are removed from the ropes, placed in mesh tubes and transferred to bouchots for growth.Mussel seeds are harvested from August – December depending on the size and density of settlement.The seeds are scraped from the poles using a steel blade attached to a metal wire to hold the scrapped offmussel. In this method, ropes with spat attached are wound around large vertical poles (Bouchots) in theintertidal zone. The line of poles mainly oak tree trunks 4-7 M long, 12-25 cm diameter at the wider end andabout 7 cm at the opposite end. The lower 3 meter of the pole is inserted in the seabed. Mesh netting is usedto cover the mussels to prevent them being detached and lost. A barrier is placed at the bottom of the pole toprevent predators such as crabs from reaching the mussels. Bouchot are placed perpendicular to the shorelineand consists of 125 poles running for 50-60m and spaced 15-25m from the next line. This method of culturerequires large tidal ranges, in order to supply the densely packed mussels with plankton.Marketable mussels of 4-5 cm shell length are harvested when they are 12-18 months old. On an average,25 kg of mussels are harvested from each pole annually. The entire produce is sold domestically. 4000 poles canproduce 100 tonnes of mussel per year.2. Stake cultureIn Thailand and Philippines, mussels are grown on bamboo poles (6-8m long) staked at half meter depthand one meter apart or in circle and tied at the top to form a wigwam structure in soft, muddy bottoms.Mussels (Perna viridis) settle on the submerged bamboo stakes. Bamboo poles are often observed to monitorgrowth as to eliminate predators like starfish and crabs. Bamboo stakes are placed in areas where naturalspatfall is expected. Mussels are harvested after a growing period of 6–10 months after stocking or when theanimals reach 5–6 cm in length. Each pole yields 8-12 kg of mussel. Harvesting is done by hauling up thebamboo poles and loading them into a raft. Divers are employed to pick out the larger mussels and the smallones left for the next harvest season. This selective harvesting results in two or more yields within the 6–8months of the farming period. Harvested mussels are cleaned and then placed in baskets and shaken vigorouslyin seawater until they are clean of barnacles and dirt. Bamboo poles that are worn out are removed while thegood ones are cleaned for the next culture season. The stake method is an economical and easy way of growingmussels but has also some shortcomings. The bamboos decay easily and it is at times difficult to match stakingoperations with spatfall. This culture system also facilitates siltation which makes bays and estuaries too shallowfor mussel farming. In Philippines a rope strung in a zigzag fashion or rope web method is used. Each unitconsists of two bamboo poles 5 meters apart are driven into the substratum. Two polypropylene rope, 2 meterapart are tied to the bamboo poles. 40 m rope of 10-12 mm diameter is used to connect in a zigzag manner.Pegs are inserted at 40 cm intervals (Joseph, 1998).43Winter School on Technological Advances in Mariculturefor Production Enhancement and Sustainability3. On-bottom cultureThis method is widely used in Netherlands, Denmark and Germany. The culture is based on the principleof transferring seeds from areas of great abundance where growth is poor to culture plots in lower density toobtain better growth and fattening of the mussel.  The culture plots must have a firm substratum and less ofdrifting sand and silt particles.  In Netherlands, the seeds are dredged from Waddenzee.  The seeds are laid inintertidal areas to produce mussels with thick shells and strong adductor muscle.  In the sub-tidal areas highermeat yield and thinner shells are produced fit for processing industry.  The whole process is highly mechanizedfrom collection of seeds to harvesting and marketing. Waddenzee and Zeeland are the important areas formussel (M. edulis) farming. In Zeeland, the town of Yerseke is the important mussel trading area. Waddenzee inthe northern part of Netherland was used as a source of seed. Since 1950, farming plots were also createdhere. The seeds which are which are fished from the seed beds during the short well defined period arescattered evenly on the beds allotted by the government to mussel farmers. The seeds are gathered by specialmussel boats. About 10 tonnes of mussel seed can be gathered in one hour of dredging operation. The seedsgathered are replanted the same day over the plot measuring 500 x 200 meters. 20 to 35 tonnes of seed areused per hectare for relaying depending upon the size of mussel seed. The mussels are distributed evenly bythe farmers if the stocking is found crowded. The starfish problem is managed by salt treatment or removalusing starfish nets. The filtering activity of the mussels produces silt which gets deposited under the musselcarpet. This hinders the growth of mussels. Chain harrow are used to level the ground. In the Waddenzee themussel are usually kept in the same area but in Zeeland the half grown mussels are relocated to deeper areaswhere conditions for fattening and growth are better. Waddenzee mussel being slightly larger are suitable forhalf shell trade and Zeeland mussels are preferred as raw material for canning factories fetching higher price.Themussels are marketable in the Dutch mussel farming areas when they are 2-3 years old. The production by onbottom culture is about 8 Kg per m2 of mussel plot or 80 tonnes per hectare. An essential part of the on bottomDutch mussel farming is the ‘re-watering’  process. Here before marketing the mussels, they are kept in speciallots for 10-14 days for the process of eliminating the weak and damaged mussel.4. Long line cultureThis method is becoming very successful in open sea mussel farming. A rope is stretched horizontally nearthe water surface and maintained 1-2 m from the surface with buoys. Mussels are grown on vertical ropesknown as ‘droppers’ which hang from the horizontal rope for a length of 4 m. Mussel seeds are collected fromnatural beds and transplanted onto the ropes into a continuous sock-like cotton tube, which is approximately17.5 cm in width. Small mussels stripped from the collection ropes are inserted. This cotton sock is thenwound around the dropper. The mussels grow and attach to the ropes using their byssal threads and the cottonsock slowly disintegrates and falls away. The droppers are placed a minimum of 0.5 m apart and have at least 4m of free space from the bottom. In deeper waters the gap between the bottom of the line and the sea floor isgreater. Anchor ropes extend from each end of the horizontal rope to anchors buried in the mud of thebottom. As the ropes are kept taut, there is no movement around the anchor to disturb the bottom as occurswhen boats are anchored. The density at which mussels can be cultured on long lines could be about 300 permeter, but depends on the food availability, which varies from site to site. Mussels grown on long-lines canbecome smothered by naturally settling juvenile mussels and other fouling organisms. For this reason, mostfarmers prefer to position their farms away from heavy spat settlement areas to avoid layers of spat attachingto larger mussels.44Course Manual5. Raft CultureThe basic principle of raft culture is similar to long line culture in that the mussels are suspended ondroppers but these are suspended from the raft instead of the long lines. The raft itself is anchored to theseabed removing the need for several anchoring systems. Long line culture however, creates less of a visualimpact, and the droppers can be spaced farther apart to maximize the use of the available phytoplankton. Raftculture is more suited to areas of dense phytoplankton and to smaller operations, as there is less scope formechanical harvesting. This method of culture is used in the Galician Bays in Spain, Saldahna Bay in South Africabut has been abandoned by the New Zealand industry in favour of long lines. This method has its origin in Spainin the Galician Bay. Mussel seeds (Mytilusgollo provincialis) settle profusely in the inter-tidal zone in the coastalwaters of Galicia. Rias are deep sunken river valleys upto 25 km in length ,2-25 km wide and 40-60m deep. Asthese rias are protected by islands at their mouth, these sheltered, nutrient rich rias with 3-4 m of tidal rangeprovide ideal environment for suspended mussel culture. The rafts are constructed using a wooden frameworkof timber and floats of concrete, steel, styrofoam or fiberglass material. The average size of the raft is 23×23meter which supports 700 ropes. The rafts are anchored along the sides with large concrete moorings. Thereare over 3000 rafts in the Galician rias. The rafts are spaced at a distance of 80-100m from each other andpositioned in groups called parks. These seeds are collected by scrapping the rocks with spade-like steel blades.Seeds can be collected by suspending ropes vertically from the rafts in December and January to catch seeds inFebruary and March. Seeds also settleon the mussel ropes. The length of the mussel ropes varies from 6-9meters according to the depth of the culture site. Pegs are used at 40 cm intervals to avoid slippage. Theaverage weight of seed per meter of rope is 1.5 to 1.7 kg. About 4600 t of seed per year are needed to maintainthe present level of production (Gosling, 2002).Thinning out of the mussel ropes are done in 3 to 6 months depending upon the growth. The ropes areremoved when the weight attain 10 Kg of mussel per meter. The ropes are hoisted and the mussel transferredto new ropes. About 3.5 Kg of half grown mussels are attached per meter of rope. After 8 to 12 months ofgrowth the mussels attain marketable size of 8-10 cm (Korringa, 1976). Growth of mussels on inshore rafts isless than on rafts in the mouth of the Rias, which demonstrates food constraint at inshore sites (Navarro et al.,1991). Temperature plays an important part on the growth as the mussels in the upper part of water column,above the thermocline (2.5m) were significantly larger than those cultivated in deeper waters (7.5 m) (Gosling,2002). Harvesting is done using mussel boats outfitted with power crane and metal baskets to collect themussel ropes. As the production is about 10 Kg of mussel per meter of rope, a raft having 600 to 1000 ropes of6-9 meter may produce 30000 to 90000 Kg of mussel per year.After harvesting, the mussels are kept fordepuration for 24-48 hours before they are marketed (Korringa, 1976).6. Rack cultureThis is the simplest of the rope method used for green mussel cultivation in India and Philippines. The mainpurpose of the pole is to support the structure.  In between these poles, ropes are suspended either vertically orkept horizontally where the depth is a limitation. The construction is labour intensive but the simplicity in harvestingand accessibility of local materials for farming purposes makes it very adaptable under local conditions. Musselculture is fast becoming popular in the Malabar area since 1997 following the success achieved by CMFRI inrearing green mussel by rack culture in the backwaters. The simple methods employed for mussel farming wastransferred to progressive farmers who took up mussel culture in the backwaters.  Soon they found the venture45Winter School on Technological Advances in Mariculturefor Production Enhancement and Sustainabilityprofitable.  Demands came from new entrepreneurs for training and mussel farming spread from Kasaragod toPonnani.  Mussel culture in the backwaters of Kerala was first started in Padanna and Cheruvattur Panchayats inHosdurgTaluk of Kasaragod district.  Later it was taken to Elathur in Calicut district and Vallikunnu and Ponnani inMalappuram district.  The total production in 2008 was 16,500 tonnes. Some of the constraints are regarding theavailability of seed. The seeds required for culture is presently collected from traditional fishing areas and theseare often causing conflicts between farmers and mussel fishermen. Hence it is essential that additional spatcollectors have to be established along the coast to ensure supply of seeds to the farmers.The harvesting seasons of cultured mussels is mostly during April – May months and farmers are forced tosell their crop before the onset of monsoon to avoid mass mortality of mussels due to freshwater influx into thebackwater system.  At present only a few processing plants purchases cultured mussels from the farmers andas a result the local market are flooded with cultured mussels during these months resulting in fall in the pricesand thereby affecting the profitability of the operation. Siltation in the backwaters is another problem. Thisoften results in mortality of mussels in the farms.  Hence scientific feasibility studies are required to demarcatepotential culture sites. Mussel farming is a decade and half old farming practice in India. This is a low investmentactivity with very good returns.  If promoted properly, mussel farming can be used as a tool for womenempowerment in the coastal areas and can stimulate a healthy socio-economic development in the area. Betterpost harvest technologies can develop attractive value added products. Since very good export markets areavailable for mussels there is further scope of extending the farming practice to suitable areas.Prospects:1. Backwater mussel culture opens immense potential for resource and employment generation among coastalcommunities especially women living below poverty line.2. Mussel culture is a low investment activity with very good returns.  If promoted properly, mussel farmingcan be used as a tool for women empowerment in the coastal areas and can stimulate a healthy socio-economic development in the area.3. Better post harvest technologies can develop attractive value added products. Since very good exportmarkets are available for mussels, they can be taken up as a challenging opportunity.Constraints:1. Availability of seed:The seeds required for culture is presently collected from traditional fishing areas and these are oftencausing conflicts between farmers and mussel fishermen.  Hence it is essential that additional spat collectorshas to be established along the coast to ensure supply of seeds to the farmers.2. Season of harvest:The harvesting seasons of cultured mussels is mostly during April – May months and farmers are at timesforced to sell their crop before the onset of Monsoon.3. Storage facility:If sufficient cold storage facility is provided, cultured mussels can be depurated, shucked and stored notonly for export market but also for local market throughout the year.  This will increase the profitability ofthe culture operation.46Course Manual4. Post harvest technology:Value added products of longer shelf life need to be developed from mussel meat to increase the revenuerealization from cultured mussels.  Mussel fry, mussel pickle etc. are some of the best examples for valueadded products.  More studies are needed to develop ethnic cuisines with longer shelf life.5. Siltation of backwaters:Some areas in the backwater system have very high siltation levels especially during rainy season. Thisoften results in mortality of mussels in the farms.  Hence scientific feasibility studies are required to demarcatepotential culture sites.For further reading1. AQUACOP, 1983. Mass production of spat of green mussel Mytilus viridis Linnaeus in French Polynesia. Proc. Symp. Coast. Aquac.,2, 539–5432. Appukuttan, K. K., Mathew,  Joseph, Thomas, K. J., 1987. Larval rearing and spat production of the brown mussel PernaindicaKuriakose and Nair at Vizhinjam, southwest coast of India. Nat. Sem. Shellfish Res. Farming, Tuticorin. CMFRI Bull. 42, 337–343.3. Gosling E. 2002. Bivalve Molluscs: Biology, Ecology and Culture. Blackwell Publishing Limited. 456 pages.4. Joseph, M. M.1998. Mussel and oyster culture in the Tropics. In: Tropical mariculture. Ed. by: Sena S. De Silva. Academic Press.487 pagers.5. Korringa, P. 1976. Farming marine organisms low in the food chain. A multidisciplinary approach to edible seaweed, mussel andclam production. Elsevier Sc. Publ. Co. 264 p.6. Navarro, E., J. I. P. Iglesias, A. Perez Camacho, U. Labarta & R. Beiras, 1991. The physiological energetics of mussels from differentcultivation rafts in the Ria de Arosa. Aquaculture, 94 (2/3): 197–212.

Mussel Farming Methods and the

Prospects and Problems in India

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Mussel Farming Methods and the Prospects and Problems in India

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