FAMILY: Mytilidae
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NAME: Mytilus sp.- The mussels |
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Data provided courtesy of Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff - (Dr. Peter Perschbacher) |
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DISTRIBUTION:
The mussels are a widely distributed genera of molluscs existing primarily in large banks or shoals . They are located in the United States, Europe, and the Eastern countries in marine, brackish, and fresh water environments. HABITS: As one may expect, mussels are filter feeding organisms and tend to grow proficiently in areas where water currents assure a consistent supply of microalgae. Unlike some bivalves such as scallops, these organisms are primarily sessile. They firmly attach to the substratum such as rocks, stones, other bivalves, and threadlike materials via a byssus. This holdfast structure is secreted by the mussel early in lie, but can be detached if "migration" is necessary. If the food source in a given area is not adequate, the mussel detaches its byssus and secretes a gas bubble enabling it to haplessly drift in the ambient currents and relocate as its buoyancy is increased. SPAWNING: Most species of mussels such as Mytilus edulus reach sexual maturity during their first year of life. These animals are broadcast spawners meaning the male and females release their gametes into the water column and fertilization is more or less a fortuitous event. Eggs and sperm are released separately and the rising temperature of spring and summer – an example of dipause, triggers spawning. The resulting free-swimming veliger larvae are planktonic for 10-15 days post fertilization depending on temperature, food supply, and the availability of settling sites. This organism is very selective to the substrate which it settles. GROWTH: The culture of mussels in France is done using poles covered with plastic mesh bags. Mussels grow rapidly after settling on the poles and clusters may extend several inches from the pole within a few months time. Periodic removal of the outer mussels (2-3 times yearly) is necessary to assure good growth of the younger mussels. These bivalves generally grow 0.5cm/month and can be marketed at a length of 5cm; therefore, they reach a marketable size in less than a year. Mussels in Spain cultured on ropes have similar growth rates but are allowed to grow an extra summer such that a length of 7.5-10cm can be attained. USES: Mussels are primarily raised as a food source; however, some of the fresh water mussels may potentially be used as a biological removal system for phytoplankton. In the latter case mussels are seeded on vertically positioned partitions in a pond to maximize growing surface area. CULTURE: Most mussel culture takes place in France, Norway, Spain, and the Philippines. Four methods are commonly implemented. Bottom culture is practiced along the coastline of Germany and the Netherlands in water 3 to 6 feet deep. Along the Atlantic coast of France the bouchot method is very popular. For this method spat is collected by suspending loosely woven ropes in the inter-tidal zone near existing natural mussel beds during May and June. Mussels are very selective as to the substrate on which they settle and occasionally will not settle out on the ropes. In this case spat must be harvested from mussel beds and relocated. The ropes are wrapped around 4 meter long oak poles secured in the substrate of inter-tidal zones adjacent to harbors and river mouths. Poles are arranged perpendicular to the coastline and positioned for maximum growth. A third method can be observed in Spain in selected Galacian bays or rias. Basically, mussels are simply cultured on ropes suspended from rafts in this instance. The fourth method entails culturing mussels on long-lines. This technique has been adopted in Sweden and China where 21 foot long-lines made of straw, plastic, are traditional twine are suspended from floats rather than rafts. REFERENCES:
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