Composition and Distribution of Macrobenthic Invertebrate Fauna 



135 



tr uj 



UJ a: 



a) < 



3 o 



2 en 



o— -o NUMBER 



• * WEIGHT 



06 



cr u. 

 O O 



2 cr 



UJ o 



0-39 4-79 8-119 12-15.9 1619. 9 20-53 9 



ANNUAL RANGE IN BOTTOM WATER TEMPERATURE 



IN DEGREES CELSIUS 



Figure 127 



Density and biomass of Scaphopoda in relation to the annual range 

 of bottom water temperature. 



diminished in abundance where carbon content was both 

 higher than and below those values (Table 26; Fig. 128). 



Biomass peaked (0.48 g/m 2 ) in the 1.00-1.49% car- 

 bon content class with somewhat smaller amounts (0.31 

 g/m 2 ) in the 0.01-0.49% class (Table 28; Fig. 128); 

 biomass in the other classes was fairly uniform ranging 

 from 0.10 to 0.24 g/m 2 . 



Frequency of occurrence was moderately low in the 

 2.00-2.99% and 0.01-0.49% content classes (15 and 

 17%, respectively) but rose to moderate levels (20 

 to 32%) in samples in the other content classes 

 (Table 30). 



Cephalopoda — Representatives of the class Cepha- 

 lopoda were not commonly encountered; they ac- 

 counted for less than 0.1% of total biomass and density 

 (Table 3). This apparent rarity is due primarily to sam- 

 pling bias exemplified by the taxa represented in the 

 samples. The class Cephalopoda contains some of the 

 largest, most mobile, and most highly developed ma- 

 rine invertebrates known to science; further, many are 

 semipelagic or pelagic in habit and are therefore se- 

 verely undersampled by bottom grabs. The abundance 

 and distribution of the commercially important squids 

 inhabiting the study area in the order Decapoda, Illex 



