Composition and Distribution of Macrobenthic Invertebrate Fauna 



85 



in the moderately high (between the 2 and 3%) con- 

 tent class. 



Nemertea 



Nemertines, although widely distributed throughout the 

 study area, made up a rather small percentage, only 0.5% 

 of density and 0.4% of biomass, of the total benthic fauna 

 due to their low abundance and die small size of die majority 

 of specimens obtained (Table 3). Their greatest numeri- 

 cal density and biomass occurred on the continental shelf 

 and along the upper portions of the continental slope. 



Members of this group are carnivores which charac- 

 teristically burrow freely in the substrate. 



Specimens in our samples ranged in size from about 

 1 to more than 25 cm in length; however, some of the 

 larger ones, although rare, were not whole, represent- 

 ing only part of an obviously larger animal. These soft- 

 bodied, vermiform organisms easily break during the 

 collecting process and frequently fragment when placed 

 in formalin for preservation. 



A large proportion of all specimens were uniformly 

 tan or flesh colored. A few individuals had brownish or 

 tan bodies with distinctive bands or stripes of white, 

 yellow, or orange. 



Although nemertines were usually represented by 

 one or a few specimens per sample, some samples con- 

 tained over 100 individuals. They occurred in 405 

 samples (38% of total). Their density averaged 8.2/m 2 , 

 and their biomass averaged 0.71 g/m- (Table 5). 



Geographic Distribution 



Nemertines occurred over nearly the entire study area 

 (Fig. 57). Their numerical abundance was moderately 

 low, averaging between 1 and 9 individuals/m 2 over 

 most of their range. An extensive area of moderate 

 density ( 10 to 49/ m 2 ) extended along southern Georges 

 Bank, across Great South Channel, and westward to the 

 vicinity of Rhode Island. They were absent in a few deep 

 water sections of the Gulf of Maine and on the conti- 

 nental rise southeast of Long Island, New York. Density 

 (average number of specimens) was greatest (23 indi- 

 viduals/m 2 ) on Georges Bank (Tables 6, 7; Fig. 58). In 

 all other areas density averaged between 1.2 and 6.8 

 individuals/m 2 . 



Over the six standard geographic areas there was a 

 slight increase in biomass of Nemertea in the shelf 

 areas from northeast (about 0.6 g/m 2 ) to southwest, 

 with the southern New England Shelf having the largest 

 biomass (1 g/m 2 ). Both slope areas had very small 



