ECOLOGY OF THE SEA SCALLOP PLACOPECTEN MAGELLANICUS 

 (GMELIN, 1791) IN THE GULF OF MAINE, U.S.A. 

 - A PRELIMINARY REPORT 



Richard W. Langton 

 Maine Department of Marine Resoruces 



Marine Resources Laboratory 

 West Boothbay Harbor ME, U.S.A. 04575 



William E. Robinson 



Edgerton Research Laboratory 



New England Aquarium 



Central Wharf 



Boston, MA, U.S.A. 02110 



ABSTRACT 



In 1984 a study of offshore scallop beds was initiated in 

 the Gulf of Maine using manned submersibles. To date, three 

 scallop populations have been surveyed and quantitatively 

 documented photographically. These populations occur on Jeffreys 

 ledge, Fippennies Ledge and Platts Bank. The three study areas 

 are physically and ecologically similar in many respects. At all 

 sites the depth ranges from 198 to 290 ft. and sediment types 

 range from sand to silty sand to cobbles and boulders. The 

 dominant macrobenthic invertebrate fauna is similar with the 

 sabellid worm, Myxicola infundibulum being numerically dominant. 

 The two other important invertebrates are the burrowing anemones, 

 Cerianthus sp. , and the sea scallop, Placopecten magellanicus . 

 Scallop density itself varies from a high of 0.98 + 2.19 scallops 

 per m on Fippennies Ledge to a low of 0.21 + 0.50 scallops per m 

 on Jeffreys Ledge with Fippennies Ledge being intermediate at 

 0.31 + 0.80 per m. The actual number of scallops per 35 mm photo 

 frame is extremely variable ranging from a density of to as 

 high as 19 scallops m~ 2 . The distribution of these data is best 

 described by a negative binomial equation. Our statistical 

 analysis has shown that the scallops are not randomly distributed 

 over the bed but, rather, occur in clusters or patches even at 

 the lowest densities observed on Jeffreys ledge. An analysis of 

 the association between the scallop and the two other dominant 

 macrobenthic invertebrates has shown a significant ( X z = 41.33, 

 P<0.05, 1 d.f.) positive association between Placopecten and 

 Myxicola and a significant (X 2 = 7.66, P<0.05, 1 d.f.) negative 

 association between Placopecten and Cerianthus on Fippennies 

 Ledge. On Jeffreys Ledge and Platts Bank the data does not 

 support the results described above for Fippennies, however, 

 scallop density is much lower and it is suggested that this 

 results in a breakdown of these faunal associations. On Jeffreys 

 Ledge, for example, scallop dredge tracks were quite evident and 

 it was observed that both Myxicola and Cerianthus occurred in 



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