Love et al : Fish assemblages around oil platforms in the Santa Barbara Channel area 



97 



Irene .\ pt Argi"" 



72wyf 



Hidalgo-^ 



130m .^ 

 Harvest Hermosa 



176m 182m 



icep'""' 



Figure 1 



Locations of 19 oil platforms in the Santa Barbara Channel and off Pt. Conception. The seven platforms sur- 

 veyed in this paper are denoted with stars and labeled. 



bara Channel platforms (Love and Westphal, 1990), 

 no other research has been published on the fishes of 

 any California oil platform. 



In 1995, we began a survey of the fishes living 

 on and around several platforms in the Santa Bar- 

 bara Channel area. The surveys were of two t3^es: 

 a scuba-based study in the surface waters (to 30 

 m) of the platforms and a submersible survey that 

 examined the deeper sections of these structures. 

 However, in 1995, we could not survey any platform 

 bottoms because of inclement weather. This paper 

 discusses the results of the 1996 deep survey. 



Channel are typically cool because the California 

 Current flows equatorward from high latitudes year- 

 round and upwells in the Point Conception and Point 

 Arguello areas during spring and summer. At the 

 same time, the cyclonic circulation pattern in the 

 southern California bight brings warm water flow- 

 ing poleward along the coast from the east and south 

 of the Santa Barbara Channel. In general, water 

 is cooler and more productive in the area of Points 

 Arguello and Conception than in the Santa Barbara 

 Channel, particularly compared with the more east- 

 ern end of the channel. 



Materials and methods 



Study sites 



We surveyed fish assemblages around oil platforms 

 situated in and just northwest of the Santa Barbara 

 Channel. Surveys were conducted around the bottom 

 of six platforms and in the midwater of seven plat- 

 forms in 1996 (Fig. 1; Table 1). The bottom depth of 

 these platforms ranged from 49 to 224 m. The mid- 

 water depths ranged from 21 to 196 m. 



The platforms are situated in an area with a com- 

 plex oceanographic regime. The Santa Barbara Chan- 

 nel is semi-enclosed, faces east-west, and is bordered 

 by the Northern Channel Islands on the south and 

 the mainland on the west. It is embedded within 

 the much larger California-Baja California coastal 

 current regime (Brink and Muench, 1986; Hickey, 

 1992). Surface waters to the north and west of the 



Surveys 



Using the submersible Delta, we conducted belt tran- 

 sects around each platform. The submersible main- 

 tained a speed of approximately 0.5 knots and stayed 

 approximately 2 m from the structure. Transects 

 were made around the bottom of the platform (from 

 the substrata to approximately 2 m above the sub- 

 strata) and around each set of cross beams to a mini- 

 mum depth of about 20 m below the surface. Dives 

 were conducted during daylight hours, between one 

 hour after sunrise and two hours before sunset. 



During the transects, researchers made their 

 observations from the central starboard-side viewing 

 port. An externally mounted Hi 8-mm video camera 

 with associated lights filmed the same viewing field 

 as seen by the observers. Observers identified and 

 counted all fishes and verbally recorded those data 

 on the video. All fishes within 2 m of the submarine 

 were counted. Fish lengths were estimated by using 



