The green mussel (Perna viridis) is also referred as the green lipped mussel or the Asian green mussel. The shell

of P.viridis tapers to a sharp, down turned beak and has a periostracum that is dark green to dark brownish green. The

ventral margin of the shell is straight or weakly concave. The beak has interlocking teeth, one in the right valve and two

in the left. The wavy posterior end of the pallial line and the large kidney-shaped adductor muscle are diagnostic

features of this species.The native range of the green mussel is along the Indian coast and throughout the Indo-

Pacific. It occurs naturally and is widely distributed along the intertidal coasts of Indi

Asokan, P K

CMFRI Digital Repository

Course ManualCentral Marine  Fisheries Research Institute(Indian Council of Agricultural Research)P.B.No.1603, Marine Drive North Extension,Ernakulam  North ,P.O.Cochin, KERALA – INDIA - 682018Winter School  onRecent Advances in Breeding  and Larvicultureof Marine Finfish and Shellfish30.12.2008 -19.1.2009CMFRICompiled and  Edited byDr. K. Madhu, Senior Scientist  and  Director,Winter school&Dr. Rema Madhu, Senior  Scientist and Co-ordinatorCentral Marine Fisheries Research InstituteCMFRI - Winter School Course Manual on “Recent Advances in Breeding and Larviculture of Marine Finfish  and Shellfish”.30.12.2008 - 19.1.2009177PRESENT STATUS OF MUSSEL FARMINGP.K. Asokan,Senior Scientist, Calicut  Research Centre of Central Marine Fisheries Research Institute,P.O.West Hill, Calicut-5.E -mail : asokanpk@gmail.comIntroductionThe green mussel (Perna viridis) is also referred as the green lipped mussel or the Asian green mussel. The shellof P.viridis tapers to a sharp, down turned beak and has a periostracum that is dark green to dark brownish green. Theventral margin of the shell is straight or weakly concave. The beak has interlocking teeth, one in the right valve and twoin the left. The wavy posterior end of the pallial line and the large kidney-shaped adductor muscle are diagnosticfeatures of this species.The native range of the green mussel is along the Indian coast and throughout the Indo-Pacific. It occurs naturally and is widely distributed along the intertidal coasts of India.Sexes in this species are separate and the fertilization is external.  Spawning is closely related to the monsoonseasons and occurs twice a year during March-April and October-November. Sexual maturity typically occurs at 15-30mm shell length (corresponding to 2-3 months). The life span of P.viridis is typically 2-3 years.  Growth rates areinfluenced by environmental factors such as temperature, food availability and water movements.  First year growthrates vary between locations and range from 49.7 mm/yr in Honk Kong to 120 mm/yr in India.Spawning is initiated by either sex of the green mussel with each releasing two streams of gametes into thewater. Spawning has also been induced by the presence of other spawning individuals in the area and a drop insalinity. Females release about 5 lakh eggs. Seven to eight hours after fertilization, the zygote is completely transformedinto mobile, trochophore larvae. After 16 to 19 hours the veliger larval stage is reached with the larval shell coveringthe internal body parts and developing a strong ciliated velum.  The straight hinge D shaped larvae metamorphoses topediveliger with a pedal organ, the functional foot and descends to the bottom. The larvae completely metamorphosizein eight to twelve days. In 10-12 days the larva secretes the initial byssal threads and attaches itself. Changes in organsystem takes place and the post larvae with characteristics of adult mussel called spat are formed. Perna viridis hasthe greatest growth rate of the mussels studied to date. Maximum growth of the green mussel occurs 2m below thesurface because of the increased productivity of the water at that depth and a narrow area of temperature and salinityfluctuation.P. viridis is a suspension feeder. This species is an efficient filter feeder, feeding on small zooplankton, phytoplanktonand other suspended fine organic material. The high growth rate of the green mussel is related to high salinity and anabundance of phytoplankton. The green mussel has a high tolerance for reduced salinities, increased survival duringatmospheric exposure, and high survival rates in turbid water.Mussel culture Techniques:The world mussel production (FAO data) during 2006 was 1.89 million tons valued at 1.2 billion US dollars. Theworld production of Perna viridis during 2006 was 305,321 tons valued at 2.74 million US dollars. The total productionof green mussels in India (2008) is about 15,000 tons. Many culture techniques are used for growing mussels worldwide.Some of these are described below:Bouchot or Intertidal Pole CultureIn Europe, mussel culture is believed to have started in 1235, when an Irish sailor survived a shipwreck on theAtlantic coast of France. He found that the poles he had kept for trapping birds attracted mussel spat settlement.  Thisbecame the basis for Bouchot method which is the oldest and the main method utilised in France. In this method,ropes with spat attached are wound around large vertical poles (bouchots) in the intertidal zone. A mesh netting isused to 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. This method of culture requires large tidal ranges, inorder to supply the densely packed mussels with food.CMFRI - Winter School Course Manual on “Recent Advances in Breeding and Larviculture of Marine Finfish  and Shellfish”.30.12.2008 - 19.1.2009178On-Bottom CultureThis method is widely used in Netherlands, Denmark and Germany. The culture is based on the principle oftransferring seeds from areas of great abundance where growth is poor to culture plots in lower density to obtain bettergrowth and fattening of the mussel.  The culture plots must have a firm substratum and less of drifting sand and siltparticles.  In Netherlands, the seeds are dredged from Waddenzee.  The seeds are laid in intertidal areas to producemussels with thick shells and strong adductor muscle.  In the subtidal areas higher meat yield and thinner shells areproduced fit for processing industry.  The production is about 22 tonnes per acre.  The whole process is highly mechanizedfrom collection of seeds to harvesting and marketing.Long line cultureThis method is becoming very successful in open sea mussel farming. A rope is stretched horizontally near thewater surface and maintained 1-2 m from the surface with buoys. Mussels are grown on vertical ropes known as‘droppers’ which hang from the horizontal rope for a length of 4m. Mussel seeds are collected from natural beds andtransplanted onto the ropes into a continuous sock-like cotton tube, which is approximately 17.5 cm in width. Smallmussels stripped from the collection ropes are inserted. This cotton sock is then wound around the dropper. Themussels grow and attach to the ropes using their byssal threads and the cotton sock slowly disintegrates and fallsaway. The droppers are placed a minimum of 0.5 m apart and have at least 4 m of free space from the bottom. Indeeper waters the gap between the bottom of the line and the sea floor is greater. Anchor ropes extend from each endof the horizontal rope to anchors buried in the mud of the bottom. As the ropes are kept taut, there is no movementaround the anchor to disturb the bottom as occurs when boats are anchored.The density at which mussels can be cultured on long lines could be about 300 per meter, but depends on thefood availability, which varies from site to site. Mussels grown on longlines can become smothered by naturally settlingjuvenile mussels and other fouling organisms. For this reason, most farmers prefer to position their farms away fromheavy spat settlement areas to avoid layers of spat attaching to larger mussels.Raft CultureThe basic principle of raft culture is similar to long line culture in that the mussels are suspended on droppers butthese are suspended from the raft instead of the long lines. The raft itself is anchored to the seabed removing the needfor several anchoring systems. Long line culture however, creates less of a visual impact, and the droppers can bespaced farther apart to maximize the use of the available phytoplankton. Raft culture is more suited to areas of densephytoplankton and to smaller operations, as there is less scope for mechanical harvesting. This method of culture isused in the Galician Bays in Spain, Saldahna Bay in South Africa but has been abandoned by the New Zealandindustry in favour of long lines.Fixed suspended 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 or kepthorizontally where the depth is a limitation.Indian experienceMussel culture is fast becoming popular in the Malabar area since 1997 following the success achieved byCMFRI in rearing green mussel by rack culture in the backwaters and popularizing through involvement of progressivefarmers who took up its culture in the backwaters and found it as profitable venture. As a result demands came fromnew entrepreneurs for training, and mussel farming spread from Kasaragod to Ponnani.  Backwaters Mussel culture inKerala was started first in Padanna and Cheruvattur Panchayats in Hosdurg Taluk of Kasaragod district.  Later it wastaken to Elathur in Calicut district and Vallikunnu and Ponnani in Malappuram district.  Initially the low cost technologydeveloped by CMFRI was transferred to five groups with 15 to 21 members at Cheruvattur and Valiyaparamba andprovided financial assistance through  North Malabar Gramin Bank and Cheruvattur Farmers Co-operative Bank.  Aloan of Rs.2,60,200/- was provided  with a subsidy component of 50%.  These groups harvested 67.4 tonnes ofmussels during May-June 1997.  A portion of the harvested and shucked meat (2000-Kg) was sold to the IntegratedFisheries Project, Cochin at a rate Rs.45/kg.   and the rest was sold in the domestic market. The groups could realizeRs.3,34,555/= from the harvest with a net profit of Rs.1,04,455/= within a period of 6 months.PRESENT STATUS OF MUSSEL FARMINGCMFRI - Winter School Course Manual on “Recent Advances in Breeding and Larviculture of Marine Finfish  and Shellfish”.30.12.2008 - 19.1.2009179Major areas of Mussel culture1. Kasaragod district:  The culture is done in the Padanna backwater systems in the Hosdurg Taluk.  Majorproducing areas are Thekkekad, Badakekad, Ori, Kavunchera, Valiyaparamba, Koyambaram, Padanna kadapuramand Madakkal. The total production from this area during this year is 11,000 tons.2. Cannanore district: Culture is restricted to Koduvalli and Dharmadom area. The total production is 1,900 ton.3. Malappuram district: TTC training was given to 45 trainees at Vallikunnu panchayat during September1999by CMFRI.  Subsequently, during January 2001, training was imparted to 60 trainees of Malappuram district under theself-help group (SHG) training programme of the State fisheries Department.  This training was conducted at Balathurithi.The total production from this area during this year is 1500 tons.4.Kozhikode district: Mussel culture is being done in the Korapuzha estuarine system.  Initially training wasimparted to 20 persons under the self-help group (SHG) training programme of the State fisheries Department.  Thetotal production is about 2,000 tons.Constraints1. Availability of seed:The seeds required for culture is presently collected from traditional fishing areas and these are often causingconflicts between farmers and mussel fishermen. This year has seen more conflicts than previous years.  Hence it isessential that additional spat collectors have to be established along the coast to ensure supply of seeds to thefarmers.Fig1. Typical mussel farm at PadannaFig 2. Mussel culture training at Elathur Fig.3. Collected seed of Green mussel P.virdisPRESENT STATUS OF MUSSEL FARMINGCMFRI - Winter School Course Manual on “Recent Advances in Breeding and Larviculture of Marine Finfish  and Shellfish”.30.12.2008 - 19.1.20091802. Marketing:The harvesting seasons of cultured mussels is mostly during April – May months and farmers are forced to selltheir crop before the onset of monsoon to avoid mass mortality of mussels due to freshwater influx into the backwatersystem.  At present only a few processing plants purchases cultured mussels from the farmers and as a result the localmarket are flooded with cultured mussels during these months resulting in fall in the prices and thereby affecting theprofitability of the operation.3. Depuration system:The main constraint in the export of cultured mussels is the lack of proper depuration techniques.  Depurationplants are needed at regular intervals along the coast so as to depurate the cultured mussels for export processing.4. Storage facility:If sufficient cold storage facility is provided, cultured mussels can be depurated, shucked and stored not only forexport market but also for local market throughout the year.  This will increase the profitability of the culture operation.5. 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 value addedproducts.  More studies are needed to develop ethnic cuisines with longer shelf life.6. Siltation of backwaters:Some areas in the backwater system have very high siltation levels especially during rainy season.  This oftenresults in mortality of mussels in the farms.  Hence scientific feasibility studies are required to demarcate potentialculture sites. Silting of the bottoms where culture is done may induce a problem for the benthic communities locatedunderneath. This should be solved by strong policies directed towards correct management of the fouling and siltaccumulated by the hanging ropes.Prospects:1. Backwater mussel culture is a decade old  phenomenon along the Malabar coast and opens immensepotential for resource and employment generation among coastal communities especially women living below povertyline.2. Mussel culture is a low investment activity with very good returns.  If promoted properly, mussel farming canbe used as a tool for women empowerment in the coastal areas and can stimulate a healthy socio-economic developmentin the area.3. Better post harvest technologies can develop attractive value added products. Since very good export marketsare available for mussels, they can be taken up as a challenging opportunity by technicians and scientists.4. In the western countries, mussel is considered as poor man’s oyster.  But in India, mussel can be consideredas tool for the upliftment of the poor people living in the coastal areas especially along the Malabar Coast.PRESENT STATUS OF MUSSEL FARMING

Present status of mussel farming- Winter School on Recent Advances in Breeding and Larviculture of Marine Finfish and Shellfish

http://eprints.cmfri.org.in/5367/1/31.pdf

Present status of mussel farming- Winter School on Recent Advances in Breeding and Larviculture of Marine Finfish and Shellfish

Abstract

Similar works

Full text

Available Versions

CMFRI Digital Repository