96 



Abstract.-In 1996 we surveyed the 

 fishes living on and around seven olT- 

 shore oil platforms in the Santa Bar- 

 bara Channel area. We conducted belt 

 transects at various depths in the mid- 

 water and around the bottoms of each 

 platform using the research submers- 

 ible Delta. The bottom depths of these 

 platforms ranged from 49 to 224 m and 

 the midwater beams ranged from 21 

 to 196 m. We found that there were 

 several distinct differences in the fish 

 assemblages living in the midwater 

 and bottom habitats around all of the 

 platforms. Both midwater and bottom 

 assemblages were dominated by rock- 

 fishes. Platform midwaters were dom- 

 inated by young-of-the-year (YOY) or 

 juveniles up to two years old. Rockfishes 

 larger than about 18 cm total length 

 were rarely seen in the midwater. The 

 fish assemblages around the bottoms 

 of the platforms were dominated by 

 larger individuals, primarily subadults 

 or adults. Density of all fishes was sim- 

 ilar between the bottoms and midwa- 

 ter of any given platform. However, 

 the total biomass was much greater on 

 the bottoms, owing to larger fish living 

 there. There was a consistently greater 

 number of species on the bottom than 

 in the midwater of each platform, likely 

 because of a larger variety of habitat 

 types on the bottom. The fish assem- 

 blages also differed among platforms. 

 We found significantly higher densities 

 of young-of-the-year rockfishes around 

 platforms north of Pt. Conception com- 

 pared with those in the Santa Barbara 

 Channel, probably because the more 

 northerly platforms are located in the 

 more productive waters of the Califor- 

 nia Current. 



Fish assemblages around seven oil platforms 

 in the Santa Barbara Channel area 



Milton S. Love ^: 



Jennifer E. Caselle 



Linda Snook 



Marine Science Institute 



University ol California 



Santa Barbara, California 93106 



E-mail address (for M S Love) loveio'lifesci.ucsb edu 



Manuscript accepted 16 August 1999. 

 Fish. Bull. 98:96-117 (2000), 



Petroleum production has been a 

 part of the southern Cahfornia econ- 

 omy since the nineteenth century. 

 The earhest drilUng took place on 

 land, but by the early twentieth cen- 

 tury a large number of piers lined 

 the coast, tapping into offshore oil 

 deposits. Hazel, the first offshore 

 oil platform, was constructed off 

 Summerland in 1958 (Carlisle et 

 al., 1964). At the peak of oil drill- 

 ing in the early 1980s, there were 

 30 platforms operating in southern 

 and central California. Currently, 

 there are 19 platforms in operation 

 in the Santa Barbara Channel and 

 off Point Conception (Fig. 1). 



Oil platforms provide considerable 

 habitat for marine organisms. The 

 earliest structures were relatively 

 small (23 m long at the surface), 

 newer platforms, however, are over 

 100 m long (MBCi). Sessile inverte- 

 brates (primarily mussels, barnacles 

 and anemones) encrust the pilings 

 and well pipes and cover the bottom 

 to form additional habitat. 



Oil platforms have a finite eco- 

 nomic lifespan and a number of 

 them are becoming uneconomical 

 to operate. In 1996, four platforms 

 were removed from the Santa Bar- 

 bara Channel, although not without 

 controversy. There is considerable 

 debate regarding the fate of these 

 structures. Some interest groups 

 would like to leave part or all of 

 them in place, claiming protection of 

 fish habitat; others favor complete 



removal. Understanding the biologi- 

 ical communities on the platforms 

 is crucial to making rational deci- 

 sions regarding the fates of these 

 structures. In addition, research on 

 these platforms could also address 

 questions regarding the role that 

 artificial reefs might play in coastal 

 fish communities. Ultimately, this 

 research will allow us to contrast 

 the fish assemblages on platforms 

 with those of nearby reefs. 



Currently, very little is known 

 about the fish fauna around these 

 platforms. One relatively compre- 

 hensive SCUBA survey examined 

 fish populations around two shallow 

 inshore platforms. Hazel and Hilda, 

 during Hazel's first three years and 

 Hilda's first year of operation (Car- 

 lisle et al., 1964), Additional cur- 

 sory surveys were conducted around 

 these two platforms in 1970 and 

 1975; Bascom et al., 1976; Allen 

 and Moore'^). With the exception of 

 a short-term study of fishes around 

 platform Hidalgo using a remotely 

 operated vehicle (ROV) (Love et 

 al., 1994) and a survey of recre- 

 ational fishing around Santa Bar- 



• MBC( Marine Biology Consultants). 1987. 

 Ecology of oil/gas platforms offshore Cal- 

 ifornia. Outer Continental Shelf (OCS) 

 Studv Minerals Management Service (MMS) 

 86-0094. 



- Allen, M. J, and M.D.Moore. 1976. Fauna 

 of offshore structures. South. Calif Coast. 

 Water. Res. Proj. Annu. Rep., Long Beach, 

 CA, p. 179-186. 



