Nine species from these phyla are discussed in this chapter. They were chosen 

 for the following reasons: they represent a relatively large proportion of 

 the overall benthic invertebrate production due to their abundance, size, and 

 widespread availability (i.e., found along much of the Maine coast); in 

 combination with fish, they are the basis of Maine's commercial fishery, and 

 sufficient information about them is available to develop meaningful accounts. 



The species selected are: (1) molluscs--soft-shell clam, blue mussel, and sea 



scallop; (2) crustaceans — lobster , jonah crab, rock crab, and northern 



shrimp; and (3) polychaetes—bloodworm and sandworm. The distribution of 



commercially harvested shellfish and marine worm areas is shown in atlas map 

 4. 



These species accounts for coastal Maine describe distribution and abundance, 

 life history, habitat preference, factors of abundance, importance to humans, 

 human impacts, and management. Data deficiencies and research recommendations 

 for the nine species named are given at the end of this chapter. In addition, 

 the red tide organism, Gonyaulux excavata , is discussed below. Common names 

 of species are used except where accepted common names do not exist. 

 Taxonomic names of all species mentioned are given in the appendix to chapter 

 1. 



SOFT-SHELL CLAM (Mya arenaria) 



The soft-shell clam is a bivalve that lives in sediment at both intertidal and 

 subtidal levels in estuaries and coastal regions of the ocean. This clam is a 

 hardy species and is found in a wide range of salinities, temperatures, and 

 sediment types. It tolerates long periods of ice cover as demonstrated in 

 Denmark (Rasmussen 1973) and is capable of anaerobic respiration (Newell 

 1970) , which means it can survive for limited periods of time in the presence 

 of little or no dissolved oxygen. Clams are harvested in abundance by 

 commercial clam diggers and, to a lesser extent, by the general public for 

 private use. 



Distribution and Abundance 



In the Atlantic Ocean, the range of the soft-shell clam extends from Labrador 

 to North Carolina and from Norway to France. It also occurs on the northern 

 Pacific coast. Greatest abundance, based on commercial landings, occurs on 

 the northeastern coast of the United States, particularly in New England and 

 Maryland. Clams are nonmigratory and in favorable habitats occur in high 

 densities. Commercially harvested clam flats are depicted in atlas map 4. 



Life History 



The soft-shell clam usually reproduces annually in Maine and semiannually 

 south of Cape Cod. Sexual maturation of the individual depends on growth rate 

 (i.e., the faster the growth, the earlier the maturation) but usually occurs 

 in approximately one year (personal communication from L. L. Loosanoff, 17 

 Ceross Drive, Green Brae, CA; November, 1973). 



In western Maine the species spawns during May to September, but along the 

 eastern coastline, they spawn from early June to mid-August. The warmer water 

 temperatures, which also occur earlier and for longer periods of time in 



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