In principle, the management of clams could be based upon optimum yields. 

 Conceivably, the leasing of clam areas by competitive bidding, a practice 

 common in Maryland, could motivate long term lessees to manage for optimum 

 yields in Maine. 



BLUE MUSSEL ( Mytilus edulis ) 



The blue mussel is a bivalve that attaches by its byssal threads to hard 

 substrates, and lives in the intertidal and subtidal zones of the marine and 

 estuarine systems. They can endure extensive variations in salinity, 

 temperature, and dissolved oxygen concentrations. 



Blue mussels have been cultured and harvested in western France and Spain for 

 hundreds of years. Although they have substantial commercial potential, blue 

 mussels have not been harvested as extensively in the United States. 

 Recently, the demand for mussels as fresh food has increased in the U.S. For 

 a detailed and comprehensive coverage of the mussel industry, see Lutz (1976). 



Distribution and Abundance 



In the western Atlantic the range of this species extends from the Arctic to 

 South Carolina (Abbott 1974). Blue mussels are also abundant on the West 

 Coast of the U.S. Commercial harvest occurs principally in Maine, 

 Massachusetts, Rhode Island, and Long Island, NY. Greatest abundances in 

 Maine (based on a survey of commercial-sized mussels between the Damariscotta 

 estuary and Jonesport; MARITEC 1978) occur in Frenchman Bay (region 3), and 

 the Blue Hill Bay - Deer Isle area (region 5). Mussel beds known to be 

 commercially harvested in Maine are depicted in atlas map 4. 



Life History 



Completion of the life cycle requires about one year. In the characterization 

 area, spawning occurs at low levels throughout the year, but the principal 

 spawning period is between mid-May and mid-June, with another spawning 

 possibly occurring in the fall (personal communication from L. S. Incze, 

 University of Maine, Orono, ME; June, 1978). 



Between 5 and 12 million eggs may be produced by a single female mussel in a 

 year (Field 1922). Sexes are separate and gametes are shed into the water 

 where fertilization occurs. Depending on environmental conditions, the larvae 

 are pelagic for approximately 19 days (personal communication from L. S. 

 Incze, University of Maine, Orono, ME; November, 1977). In the pelagic 

 environment, the larvae are subjected to biotic and abiotic stresses. 

 Mortality at this stage is believed to be very high. 



The larvae first settle on flexible substrate such as algae, hydroids, or 

 byssal threads but they may detach and resettle one or more times until they 

 find an appropriate substratum. The larva may delay metamorphosis for some 

 time if the appropriate substratum is not available; however, after about 8 

 weeks or when a length of 0.06 to 0.4 inches (1.5 to 10 mm) is reached the 

 larva will settle wherever it is at that time (Mason 1972). Upon 

 metamorphosis the mussel is considered a juvenile. 



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