Tissot et al Invertebrates on deep banks off souttnern California 



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Figure 1 



Locations of survey sites and dives (black dots) conducted inside and outside the cowcod conservation areas 

 (delineated by outlined boxes) off southern California in 2002 to ascertain patterns in the density, distribution. 

 and size of habitat-forming invertebrates. 



We documented dives continuously during daytime 

 hours with an externally mounted high-8 video camera 

 positioned above the middle viewing-porthole on the 

 starboard side of the submersible. The observer ver- 

 bally annotated all tapes with observations on fishes, 

 invertebrates, and physical habitats. Two parallel lasers 

 were installed 20 cm apart on either side of the external 

 video camera for estimating fish and invertebrate sizes 

 and delineating a 2 m-wide belt transect for counting 

 fishes and invertebrates. We used personal dive sonar 

 from inside the submersible to verify the width of swath 

 for the belt transects. Digital still and video cameras 

 were used inside the submersible to help document 

 fishes, invertebrates, and habitats. 



We defined "habitat" using a combination of nine dif- 

 ferent categories of substratum and standard geologi- 

 cal definitions (see Stein et al., 1992; Yoklavich et al., 

 2000). In order of increasing particle size or relief, these 

 substrata were the following: mud (code M), sand (S). 

 gravel (G), pebble (P), cobble (C), boulder (B), continu- 

 ous flat rock (F), rock ridge (R), and pinnacles (T). A 

 two-character code was assigned each time a distinct 

 change in substratum type was noted along the tran- 

 sect, thus delineating habitat patches of uniform type. 

 The first character in the code represented the substra- 



tum that accounted for at least 50% of the patch, and 

 the second character represented the substratum ac- 

 counting for at least 20% of the patch (e.g., "BC" repre- 

 sented a patch with at least 50% cover by boulders and 

 at least 20% cover by cobble). Each habitat patch also 

 was assigned a code based on the degree of its three- 

 dimensional structure as defined by the vertical relief of 

 the physical substrata from the seafloor. Habitats were 

 coded as l=low (<1 m), 2=moderate (1-5 m), or 3=high 

 relief (>5 m). Patches less than 10 seconds in duration 

 were not recorded. The area of each habitat patch was 

 determined by calculating the distance between the 

 beginning and end of habitat patches with ArcGISC© and 

 multiplying by the width of the transect (2 m). 



A total of 58 different types of habitat patches were 

 observed across all dives. These data were analyzed by 

 a cluster analysis (Euclidean distance, group average 

 method) by using the abundances of the 20 most com- 

 mon invertebrate species, and the resulting dendrogram 

 was used to pool the number of codes into the 17 most 

 distinct habitat types exhibiting a similarity of >50%. 



Direct counts of megafaunal invertebrates were made 

 from videotapes within each habitat patch; patch areas 

 varied from 12-1472 m-. Densities of invertebrates were 

 estimated by dividing the total number of individuals 



