744 



Fishery Bulletin 100(4) 





Bottom Type 



Mud 

 /\/ Mixed 



Dover Sole 

 fish/hectare 







0-200 

 /\/ 200 • 300 

 /\/300  4.000 



--'/' 





£^ 



^ %^^ 



Rosethom Rockflsh 

 fish/hectare 







0- 200 

 /\/ 200- "WO 

 /\J^a  17.000 







i^£»jij. w- 



*' 





■f:e 



Figure 4 



Submersible transects in the middle portion of Heceta bank segmented by obsei-vations 

 of I A) bottom-type habitat, categorized by mud. mixed substrate, and rock ridge (B) den- 

 sity of Dover sole iMicrustonius pacificus ) and IC) density of rosethorn rockfish tScbastcs 

 helromaciilatusl. 



showed changes in seafloor texture. Borders of rock ridge 

 and mud observed in the submersible survey matched the 

 bathymetric data, indicating areas of high reHef for rocky 

 patches and low relief for areas of mud (Figs. 4A and 5). 

 Changes in backscatter also corresponded with changes 

 observed in bottom type from the submersible data (Fig. 5). 



It was noted consistently that high-backseatter areas 

 were associated with mixed substrate habitat, comprising 

 a combination of pebble, cobble, and boulder, which due 

 to their size and geologic composition have a relatively 

 high reflectivity. Mid-backscatter values were found to be 

 associated with rock ridge features. These are typically 



