76 



NOAA Technical Report NMFS 140 



(Fig. 39). They were absent in the samples 

 from Georges Bank. Their average density in 

 all localities was between 1 and 15/m . Their 

 average biomass at all localities was 18.9 g/m 2 

 or less. 



Alcyonarians were present in approximately 

 the same quantities in all standard geographic 

 areas, except Georges Bank where they were 

 absent. Average densities in geographic areas 

 where they were present ranged from 0.7 to 

 1.5/m 2 , and average biomasses ranged from 

 0.03 to 0.43 g/m 2 (Tables 6-9; Fig. 40). 



In addition to number and weight per unit 

 area, another reasonably good index of abun- 

 dance is the percentage of samples contain- 

 ing alcyonarians (Table 10). All shelf areas 

 (Nova Scotia, Gulf of Maine, Georges Bank, 

 and Southern New England Shelf) had a fre- 

 quency of occurrence of 7% or less. The oc- 

 currence rates on Georges Slope and South- 

 ern New England Slope were 27% and 17%, 

 respectively. Alcyonarians formed a larger 

 share of the total benthic fauna in the latter 

 two (slope) areas than in the shelf areas. 



Bathymetric Distribution 



Alcyonarians were most common in deep wa- 

 ter habitats in the New England region. They 

 were not present in any samples taken at 

 depths less than 50 m but were represented in 

 all depths greater than 50 m (Tables 11-14; 

 Fig. 41 ). Although differences in average den- 

 sity and weight from one depth class to an- 

 other were small, the larger quantities were 

 most prevalent in deep water (100 to 2,000 

 m). Highest average density and largest aver- 

 age weight, 1.9/m 2 and 0.47 g/m 2 , respec- 

 tively, occurred at depths from 200 to 500 m. 

 The frequency of occurrence of alcyonar- 

 ians in our shallow water (<50 m) samples was 

 zero (Table 15). The occurrence was 5% at 

 moderate depths (50 to 200 m) and increased 

 to moderately high levels (22 to 29%) in deep 

 water areas. 



Relation to Bottom Sediments 



Alcyonarians occurred only in selected types of sub- 

 strate (Tables 1<>-19; Fig. 42). The Alcyonacea and 

 Gorgonacea were collected from gravel and rocky out- 

 crops, in contrast to the Pennatulacea, which inhabited 

 sand-silt and silt-clay sediments. No alcyonarians were 

 taken on substrates of till or shell, and they were present 

 in only 5 samples out of a total of 455 from sand 

 bottoms. Frequency of occurrence of this faunal group 



was highest (10 to 12%) in the silt-clay and sand-silt sedi- 

 ments and substantially lower (4%) in gravel (Table 20). 



Relation to Water Temperature 



Alcyonarians occurred only in areas where the annual 

 temperature range was moderate or small, and less 

 than 16°C (Tables 21-24; Fig. 43). The trends in both 

 quantitative measures and also in frequency of occur- 

 rence exhibited a bimodal relationship. 



