92 



NOAA Technical Report NMFS 140 



Geograph ic Dis tribution 



The distribution of large free-living nematodes, although 

 occurring in all geographic regions, was patchy (Fig. 

 63). Thev were present in coastal areas, on the offslx >re 

 banks and basins, and on the continental slope and 

 rise. Thev were commonly absent in samples from a 

 number of areas: parts of the Nova Scotian shelf, large 

 portions of the Gulf of Maine and Georges Bank, as well 

 as many inshore bays and sounds. The pattern of their 

 distribution suggests that they are less common in sub- 

 strates where the overlying bottom current or wave 

 action is strong, for example, the northern section of 

 Georges Bank and at the mouth of the Bay of Fundy. 



The average density of nematodes in each of the six 

 standard geographic areas was roughly similar, ranging 

 from 0.9 to 4.0 indivi duals/ m 2 (Tables 6, 7; Fig. 64). 

 Their average biomass was very low, 0.01 g/m'- or less 

 (Tables 8, 9; Fig. 64). 



The percentage of samples containing nematodes 

 was low (5 to 9'i ) in the four geographic areas on the 

 continental shelf (Table 10), but their occurrence in 



the two continental slope areas was comparatively high 

 (15 and 39%). 



Bathymetric Distribution 



Nematodes were found at depths ranging from 23 to 

 3,975 m and were present in all depth classes sampled 

 (Tables 11, 12; Fig. 65). Average density was slightly 

 higher in the very shallow (0-24 m) and moderately 

 deep (200-1,000) water than in other zones. Average 

 density values ranged from 0.8 to 6.8 individuals/m-. 



Average biomass values were uniformly low (0.01 g/m 2 

 or less) at all depths (Tables 13, 14; Fig. 65). 



Frequency of occurrence of nematodes in the samples 

 was low (2%) in shallow water and generally increased 

 to moderately high levels (35%) in deep water (Table 

 15). 



Relation to Sediments 



Nematodes were present in all bottom types except 

 shell (Tables 16. 17; Fig. 66). Greatest density (8.7 

 individuals/m ) occurred in gravel substrates, whereas 



