172 



NOAA Technical Report NMFS 140 



1400 



1200 - 



OI000 



400 



200 



O O NUMBER 



•— — • WEIGHT 



- 10.0 



8.0 



2 



o 



K u. 



6.0 ° ° 



Z CC 



1 £ 

 UJ Ul 

 4.0*5 



t- 2 



8 



IE 

 Ul 



a 



2.0 



0.01 



0.5 



15 2 3.0 



PERCENT ORGANIC CARBON 



100 



Figure 177 

 Density and biomass of Amphipoda in relation to sediment organic carbon. 



Frequency of occurrence of mysids in samples was 

 low in all areas ranging only from 1 to 10% (Table 10). 

 Georges Bank had the highest occurrence frequency. 



Bathymetric Distribution 



Mysids occurred in the somewhat limited depth range 

 of 9 to 292 m. They were most abundant (densities of 

 3.8 to 6.5 individuals/m 2 ) at depths less than 100 m 

 (Table 11; Fig. 180). At depths greater than 100 m, 

 their density was only 0.1 or less/m 2 . 



Biomass, although very small, revealed a rather con- 

 stant diminution in quantity from shallow to deep water 

 (Table 13; Fig. 180). 



Mysids occurred in 13% of the samples from the 

 shallowest depth class, and their rate of occurrence 

 dropped with increasing water depth to 1% or less in 

 the deepwater classes (Table 15). 



Relation to Sediments 



Mysids were found in four of the six bottom sediment 



types (Table 16; Fig. 181). Their density (5 individuals/ 



m 2 ) in sediments composed of sand was substantially 

 higher than in the other sediment types. In gravel, 

 sand-silt, and silt-clay the densities were less than l/m\ 



Biomass was very low (0.02 g/m 2 ) even in sand sediments 

 where mysids were most abundant (Table 18; Fig. 181). 

 Values for the other bottom types were 0.01 g or less/m 2 . 



Mysids were present in a higher proportion of the 

 samples (6%) from sand sediments than from the other 

 bottom types (Table 20). 



Relation to Water Temperature 



Mysids exhibited a general trend of increasing in both 

 density and biomass as the annual range in tempera- 

 ture broadened (Tables 21, 23; Fig. 182). Average nu- 

 merical density increased from <0.1/m 2 where the tem- 

 perature range was <4°C, to 6.1/m 2 in localities where 

 the temperature range was over 20 9 C. Biomass ranged 

 from <0.01 to only 0.02 g/m 2 . 



Frequency of occurrence values varied in a similar, 

 but more consistent, manner to those of density and 

 biomass. The percentage of samples yielding specimens 



