Butler et al : Multlbeam sonar mapping techniques for estimates of Haliotis sorenseni 



525 



-32'29'N 



■32-28'N 



-n9*l3'W -n9i2W -119 11 W 119 loW n99"W -ngsW -ng 7*W -119 6'W -1195W 



-118-40''W -I19 3HVV 118 in W llS2'iW -118-20'W 



32 SON 

 32 48N 

 32 46 N 

 32 44N 



-118'30'W IIS'JSW 118'20W 



Figure 1 (continued) 



algal cover in segments containing abalone, and those 

 where abalone were absent for the Tanner Bank 2002 

 survey. For the purposes of PCA, transects were divided 

 into 100-m segments. All PCA coefficients were plot- 

 ted initially to examine relationships between abalone 

 presence and absence and defined variables. Coefficients 

 from the most influential variables were then plotted to 

 examine these relationships more closely. 



Transects varied in length from 0.4 to 6 km, although 

 most transects were close to 1 km in length. To esti- 

 mate abalone densities we attempted to search within 

 a particular 10 m depth interval during each transect. 

 When this was not possible, transects were poststrati- 



fied by depth interval (10 m), because results of pre- 

 liminary surveys provided evidence of the prevalence of 

 white abalone within particular depth ranges. For the 

 few cases (2) where poststratification yielded a search 

 area of less than 100 m^, the data for these areas were 

 excluded from the analysis because densities would be 

 artificially inflated. We calculated density per unit of 

 area for each transect and stratified transects by three 

 depth intervals (30-40 m, 40-50 m, and 50-60 m) to 

 test for differences among depths and sites using Krus- 

 kal-Wallis nonparametric techniques on ranked data 

 (Systat vers. 11, Systat Software Inc., Point Richmond, 

 CA). The mean depth of abalone occurrence was tested 



