208 



NOAA Technical Report NMFS 140 



17% in the three classes between 0.01 and 

 1.49%, and was 7% in the 1.50 to 1.99% con- 

 tent class (Table 30). 



Hemichordata 



Representatives of the phylum Hemichordata 

 are all from one class (Enteropneusta, acorn 

 worms) and one genus (Balanoglossus). A to- 

 tal of 101 specimens, weighing 18.7 g, were 

 collected at 4 stations (0.4% of total); aver- 

 age density (0.1 individuals/m ) and biomass 

 (0.02 g/m 2 ) were very low (Table 5). 



Geographic Distribution 



The geographic distribution of acorn worms 

 was restricted to the Southern New England 

 Shelf (3 stations) and Southern New England 

 Slope (1 station). Mean densities were 0.3 

 individual/m 2 or less and mean biomass 0.06 

 g/m or less (Tables 6 and 8; Fig. 232). Fre- 

 quency of occurrence of hemichordates in 

 the samples was a very low 1% (Table 10). 



Bathymetric Distribution 



Acorn worms occurred in three depth range 

 classes: 50-99 m, 100-199 m, and 500-599 

 m, where their mean density ranged from 

 <0.1 to 0.5 individual/m and their mean 

 biomass was 0.01 g/m 2 in the two deepwater 

 ranges and 0.05 g/m 2 in the mid-shelf range 

 (Tables 11,13; Fig. 233). Five percent of the 

 samples in the 500-999 m depth range 

 yielded specimens, whereas the occurrence 

 in the other two was from <1 to 1% (Table 

 15). The depth range of our samples was 

 from 79 to 567 m. 



5 

 O 



u. uj 2 

 O 2 



a: uj 

 uj (£ 



CD < 



i § ' 



z in 



□ NUMBER 

 ■ WEIGHT 



[L 



U 



SAND- SILT- 



SILT CLAY 



S 



o 



<* u. 



<= o 



I UJ 



O 5 



UJ uj 



* rr 

 < 



t- z> 



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BOTTOM SEDIMENTS 



Figure 229 



Density and biomass of Asteroidea in relation to bottom sediments. 



Relation to Bottom Sediments 

 Acorn worms were found in low abundance 

 in sand, sand-silt, and silt-clay substrates. 

 Mean density ranged from <0.1 to 0.2 indi- 

 vidual/m 2 and mean biomass from <0.01 to 

 0.04 g/m 2 (Tables 16, 18; Fig. 234). Fre- 

 quency of occurrence in the samples was <1 

 to only 1% (Table 20). 



Relation to Bottom Temperature 

 Hemichordates were restricted to areas where 

 the annual range in water temperature was 

 less than 16°C. Mean density and biomass 

 were very low (<0.1/m 2 and <0.01 g/m 2 ) in 

 the lowest temperature range class; mean den- 

 sities of 0.2/m 2 occurred in each of the two 



