Nasby Lucas et al : Use of submersible transect data and multibeam sonar imagery for habitat assessment 



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RR BB BC CB CC CM MB MC MP MtVI RR BB BC CB CC CM MB MC MP MM 



Bottom type 



Figure 6 



Percent cover of bottom types calculated from observations of all transects contained 

 within each of the eight habitat patches labeled A-H. Bottom types are listed from left 

 to right by decreasing relief and particle size, where the first letter is the dominant 

 substratum and the second letter is the second most prevalent substratum. Substrate 

 categories shown comprise only the 10 most dominant bottom types, consisting of com- 

 binations of R = rock ridge, B = boulder, C = cobble, M = mud. and P = pebble. 



Combining the sonar-derived habitat patches and sub- 

 mersible observations gave an indication of bottom-type 

 compositions for the defined patches. Of the eight habitat 

 patches analyzed, three of the habitat patches were pre- 

 dominantly rock ridge (patch A—63Vc RR and 14% RC/RB; 

 patch C— 55% RR and 3% RB/RC; and patch F— 66% RR), 

 two were predominantly mud (patch D — 98% MM; and 

 patch H— 60% MM and 36% MC/MP), and three were a 

 mixture of boulder, cobble, pebble, and mud (patch B — 

 75% BC/CB/MB/MC/MM/CM/MP/BM/BB; patch E— 83% 

 MC/MM/MP/CM/MB/CP/BM/BC/CB/PM/CC/BB/BP/PB; 



and patch G— 100% BC/CB/CM/CC/MP/MC/MM/PM/BB) 

 (Fig. 6). 



There were differences in fish density within the patch- 

 es between the three major habitat classification types, 

 as well as differences among patches of similar bottom 

 types (Fig. 7, Table 1). Species with the highest association 

 with rock-ridge habitat patches were yellowtail rockfish, 

 juvenile rockfish, and lingcod. Those primarily associated 

 with mud habitats were Dover sole, rex sole, and short- 

 spine thornyheads. Those associated with mixed substrate 

 patches were sharpchin rockfish, rosethorn rockfish, green- 



