Mussel Farming Methods
Mussel Farming Methods
How Do Mussels Grow Naturally
Mussel farming depends entirely on onenatural phenomenon: spatfall. This is the periodwhen mussel larvae are developed enoughto cease their floating existence, settle, andattach themselves to solid surfaces.
Successfulcollection of these spats is essential formussel farming. While the technology to artificially produce the spats in controlled conditionsis available, it is not yet economicallyviable and is probably not necessary consideringthe abundance of natural spats. Themussels need not be grown in the same areawhere the spats are collected, and in somecases it is actually more desirable to have aseparate growing area.
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Here in the Philippines,however, all successful mussel farmingventures have been conducted in the spatfallareas. Thus, at the moment, the presence ofnatural mussel spatfall should be considered aprimary criterion in determining the viability ofa potential mussel farming project.
Site selection
The following parameters must be considered in site selection:
1. Sufficient breeding stock and spatfall.
2. Protection from strong winds and waves. Area must be sufficiently enclosed to retain larvae.
3. Enough tidal range to change watercompletely and frequently; strong tidalcurrent (>2 cm/s); and depth of at least2 m at low tide.
4. Sufficient food in the water. (Generally,clear waters do not contain enough foodto sustain optimum growth. Greenishwater is one indication of food availability.)
5. Distance from river mouth as abrupt salinity changes is possible.
6. Proximity to market.
7. Absence of sources of pollutants.
Selection of suitable collector materials
Mussel farming depends largely onplacing the right type of collector in the rightplace at the right time or season to collectyoung mussels or spats. The material whichwas proven most effective is coconut huskbecause of its hairy, fibrous nature that is veryattractive for mussel larvae to settle on. Furthermore,coconut husks are readily availablein the Philippines and are easy to prepare. Thehusk is stripped from the coconut shell andshredded. The only difficulty with coconuthusk, however, is that it does not last long inthe water, so that usually the mussels will haveto be “re-laid” or transplanted.Other suitable materials as collectorsare cabo negro, old frayed ropes, etc.
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Farm construction and operation
Basic considerations
1. Cultures should always be underwater even at low tide. Mussels that attachand survive above the lowest tide level aregenerally stunted or deformed.
2. Cultures should always be in an offbottomposition to prevent potential predatorssuch as starfish, crabs, snails, and other organismsfrom crawling up the culture ropes.
3. Materials used should be durable enough to last at least until the mussels are harvestable.
4. Clusters of mussels on a rope shouldbe adequately spaced to avoid contact witheach other through wave action.
5. Structures must always be positioned so as not to obstruct navigation.
6. Cultures should be laid perpendicular to wave action and lined up in the direction of current flow.
7. The environment of a mussel farmdegrades with continued use. It is advisable to have an area 2-3 times larger than actualculture site to allow the farm to be moved fromone section to another.
Materials and design. Raft or suspensionculture of mussels consists of growingmussels on ropes hung from rafts or othersimilar floating structures. A basic raft designis sketched in Figure 1 and an attached culturerope in Figure 2. The method of mooring asingle raft or a series of rafts is presented inFigure 3.
Spat collectors (coconut husk) are insertedin the lay of ropes to collect musselspats. These spats are allowed to grow for 4-5 months and are harvested when they reach37-60 mm in length.
Spatfall period can be predicted with afair degree of accuracy after a few years ofobservation. Thus in Bacoor Bay, farmersgenerally lay their stakes before April and inNovember. In Sapian Bay, the periods ofhighest spatfall intensity are from February to March and again from September to October.
In Himamaylan River, the spatfall occurs inMarch with a lower-intensity spatting inOctober. Generally, for greater chances ofspat settlement, the collectors or ropes shouldbe installed not earlier than February and notlater than March to catch the first spatfall which is usually the heavier one. For the secondaryspatfall, ropes should be laid not earlier thanSeptember and not later than November.
Mussels Seed Collection For Beginners
The site selected for collection of seed should be free from pollutants. Seeds collected from the submerged (sub tidal) areas will be healthier. After removing other organisms and weeds, the seeds were washed thoroughly in sea water. About 500-750g of seed is required for seeding on one meter length of rope. The ideal size of the seed is 15-25mm 1ith 1-2g weight. The length of the rope is decided by considering the depth where the raft/rack is positioned. While suspending the seeded rope on rack it must be tied in such a way that the upper seeded portion of the rope should not get exposed during the low tide.
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Nylon rope of 12-14mm 0r 15-20mm coir rope can be used for seeding. Old cottonnet, cotton mosquito net or cheap cotton cloth are used for covering the seeds around the rope. Cotton netting of required width and length is placed on the floor and required quantity of seeds spread over the net from one end to the. The rope is kept above the net and is tightly stitched in such a way that the seeds spread uniformly around the rope. The cloth will disintegrate within 2-3 days. By this time seeds will secrete byssus thread and will get attached itself to the rope. To avoid slipping of the mussels, knots are made on seeded rope at the distance of 25cm. Placing split bamboo pegs in the rope(12-14mm) at regular intervals will also serve the purpose.
Growth-out-phase
The Seed, which get attached to ropes, show faster growth in the suspended column water. If the seed is not uniformly attached, crowded portion always show slipping. To avoid slipping, periodical examination of seeded rope and thinning of the same is essential. The ropes also should be suspended in such a way that it will not touch the bottom as well as the seeded portion is not exposed for longer period during low tide. Seeded mussel on the upper portion of the rope shows faster growth due to the abundance of phytoplankton. For better growth the seeded ropes should be spaced ata distance of 25 cm.
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Mussel Culture
Training Manual on Theeranaipunya - Equipping Fisherwomen Youth for Future 187In open sea – farming, growth of mussel is very rapid. They attain 80-110 mm in 5-6months with an average growth of 13.5mm/month and an average weight of 35-45g.This growth is observed in farms at various locations. In estuarine farming, mussels attain 75-90mm in 5 months with an average weight of 35-40g and an average production of 10 -12 kg/m rope.
Management:-Constant vigil is required to see that the raft/rack is in position. Thinning may be done if necessary to avoid loss of mussel and to provide enough growing space. Periodic removal of fouling organisms like barnacles, tubiculouspolycheates and ascidians is to be done for improved growth.
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