Love and York Relationships between fish assemblages and bottom horizontal beams of oil platforms 



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Figure 2 



Examples of four types of bottom beam structure; (A) at least some of the beam was visible, but the full width of the beam 

 rested on the sea floor (greenspotted rockfish, Sebastes chlorostictus); (B) the beam was partially exposed, remaining in 

 contact with the sea floor at its bottom, not its sides (flag rockfish, S. rubrivincfus); (C) the beam was completely exposed 

 and formed an open crevice less than 0.5 m high (cowcod, S. levis); (D) the beam was completely exposed and formed an 

 open crevice more than 0.5 m high (vermilion rockfish, S. miniatus). 



Other extreme, most of the bottom beam at both Plat- 

 forms Holly in the central Santa Barbara Channel and 

 Harvest, off Point Conception, was completely buried. 

 We saw little relationship between geographic location 

 (or platform depth) and mean gap size. For instance, 

 Platforms Hidalgo and Harvest are located within 4.6 

 km of each other, yet have very different beam expo- 

 sures, as do Platforms Holly and Irene that are sited at 

 almost the same depth. A lack of relationship probably 

 reflects differences in oceanographic conditions, because 

 some of these structures are found in areas where strong 

 currents scour the bottom, whereas others are found in 

 areas where sediments have not been disturbed. 



Except for kelp greenling, all species exhibited some 

 beam habitat preference (Table 2). Species found more 

 often where the beam was completely buried (gap 0) 

 included greenstriped (S. elongatus), non-YOY lingcod, 

 rosy (S. rosaceus), sharpchin (S. zacentrus), and strip- 

 etail (S. saxicola) rockfishes, painted greenling, pink 



seaperch iZalembius rosaceus), and sanddabs iCithar- 

 ichthys spp.). Those that favored the presence of the 

 beam or some amount of exposure (exposures 1 and 2) 

 included calico (S. dallii), copper (S. caurinus), flag (S. 

 rubrivinctus), and pinkrose (S. simulator) rockfishes, 

 pile perch (Rhacochilus vacca), and sharpnose seap- 

 erch iPhanerodon atripes). Species that tended to in- 

 habit areas where there was a gap between beam and 

 sea floor (exposures 3 and 4) were blue (S. mystinus), 

 brown (S. auriculatus), canary (S. pinniger), green- 

 blotched (S. rosenblatti), halfbanded (S. semicinctus), 

 squarespot (S. hopkinsi) and vermilion (S. miniatus) 

 rockfishes, and both size classes of bocaccio (S. pau- 

 cispinis). The vast majority of cowcod (S. levis) were 

 found at beams that were scored as exposures 2 and 3. 

 Both greenspotted rockfish (S. chlorosticus) and YOY 

 lingcod appeared to prefer either soft bottom without 

 beam exposure or beam exposure without a deep gap 

 (exposures 1 and 2). 



