190 



NOAA Technical Report NMFS 140 



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GRAVEL TILL SMELL SANO SAND- SILT- 



SILT CLAY 



BOTTOM SEDIMENTS 



Figure 205 

 Density and biomass of Echinodermata in relation to bottom sediments. 



Bathymetric Distribution 



Holothurians were collected at depths ranging from 6 

 to 3,820 m, and were present in all depth classes over 

 this broad depth range (Table 11; Fig. 210). Densities 

 were highest (average 4 to 10 individuals/ m ) at inter- 

 mediate depths (50 to 500 m) and somewhat lower (0.7 

 to 1.9/m 2 ) in both shallower and deeper bathymetric 

 classes. 



Biomass distribution of holothurians differed sub- 

 stantially from the depth-density relationship (Table 

 13; Fig. 210). Highest biomass averages (13 to 37 g/m 2 ) 

 were found in depths less than 100 m. Lowest biomass 

 (0.2 g/m 2 ) occurred at 500 to 999 m; intermediate 

 quantities (1 to 6 g/m 2 ) were found in other depth 

 classes. 



Individual holothurians from shallow water (0 to 21 

 m) were larger, averaging nearly 25 g each, and size 

 decreased with increasing depth to less than 1 g each at 

 depths greater than 500 m. 



The frequency of holothurian occurrence was highei 

 in samples from deep water than in those from shallow 

 water (Table 15). At depths less than 50 m they were 

 present in 8 to 9% of the samples, whereas, in water 



depths greater than 50 m they occurred in 14 to 33% of 

 the samples. 



Relation to Sediments 



Holothurians were relatively numerous in till substrates 

 and much less common in all other bottom types (Table 

 16; Fig. 211). Their average density in till was 25 indi- 

 viduals/m 2 , whereas, in the other types of sediments 

 their density was only 2.0 to 7.4/m 2 . 



The relationships of holothurian biomass to sedi- 

 ments were entirely different from those pertaining to 

 density. The biomass was high (25 to 29 g/m 2 ) in sand- 

 silt and silt-clay (Table 18; Fig. 211). In fact, holothuri- 

 ans accounted for from 15 to over 33%, respectively, of 

 the total benthic biomass in those two sediment types 

 (Table 19). In other types of sediments their biomass 

 was moderate to small (4.7 to 0.4 g/m 2 ). 



The presence of relatively fewer but larger specimens 

 in soft sediments and numerous small specimens in till 

 sediments accounts for the disparity - between the biom- 

 ass and density values in these substrates. In the other 

 sediment types they were generally more equally dis- 

 tributed in density and biomass. 



