168 



NOAA Technical Report NMFS 140 



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Figure 173 

 Density and biomass of Amphipoda in each of the six geographic areas. 



era New England Slope area yielded an average of only 

 17 amphipods/m . 



Average biomass was very closely correlated with num- 

 ber of specimens and ranged from 8.34 g/m 2 in the 

 Southern New England Shelf area to 0.08 g/m 2 in the 

 Southern New England Slope area (Table 8; Fig. 173). 



Frequency of occurrence of amphipods was generally 

 high; they were found in 58 to 94% of the samples. In 

 the three shallow shelf areas their occurrence ranged 

 from 92 to 94% of the samples. Occurrence was lowest 

 (58 to 73%) in the Gulf of Maine and the two slope 

 areas (Table 10). 



Bathymetric Distribution 



Amphipods occurred at depths of 5 to 3,975 m. Their 

 densities were highest on the continental shelf and 

 decreased with increasing water depth (Table 11; Fig. 

 174). Usually high average densities (1,149 and 1,274 

 individuals/m 2 ) were encountered at depths between 

 25 and 100 m. In water depths greater than 100 m, 



amphipod densities dropped sharply. The average value 

 for the lower continental slope area was 12/m 2 , and on 

 the continental rise their density declined to an average 

 of only three specimens/m . 



Biomass values revealed distribution patterns in rela- 

 tion to depth similar to those described above for den- 

 sity (Table 13; Fig. 174). At depths less than 100 m, the 

 average biomass values were between 6 and 10 g/m 2 . In 

 water deeper dian 100 in, a pronounced decline in biom- 

 ass occurred; values ranged from 0.97. g/m 2 on the outer 

 continental shelf to 0.02 g/m 2 on the continental rise. 



Frequency of occurrence was moderate to high. In 

 the shallow and moderately shallow water (0-100 m) 

 amphipods occurred in 80 to 98% of the samples, but 

 in deeper water they were present in 44 to 77% of the 

 samples (Table 15). 



Relation to Sediments 



Amphipods were encountered in all of the different 



bottom types and revealed marked changes in density 



