...around eight oil and gas platforms off southern California as part of an assessment of the potential value of these structures as fish habitat. From these surveys, we estimated that there was minimum of 430,000 juvenile bocaccio at these eight structures. We determined this number to be about 20% of the average number of juvenile bocaccio that survive annually for the geographic range of the species. When these juveniles become adults, they will contribute about one percent (0.8%) of the additional amount of fish needed to rebuild the Pacific Coast population. By comparison, juvenile bocaccio recruitment to nearshore natural nursery grounds, as determined through regional scuba surveys, was low in the same year. This research demonstrates that a relatively small amount of artificial nursery habitat may be quite valuable in rebuilding an overfished species.

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Beginning in 1995, annual surveys of fish assemblages at oil and gas platforms and natural reefs throughout southern California were conducted with a research submersible (summarized in Love et al., 1999, 2000, 2003). Many California oil and gas platforms harbor three fish assemblages: those that occupy the shell mound area surrounding the base of the platform; those that occupy the waters adjacent to the platform bottom, and those that occupy the midwater. Rockfishes (genus Sebastes), of about 35 species, dominate these assemblages. The shell mound assemblage is composed primarily of juvenile rockfishes, dwarf rockfishes, and other species; the platform bottom assemblage is composed of adult and subadult fishes; and the midwater assemblage of most platforms (and the bottoms of some mid-depth platforms) is dominated by young-of-the-year (YOY) and older juvenile rockfishes that comprise at least 28 species. These fishes are rarely more than 20 cm long (total length). In the midwaters of most California platforms, there are only low densities of predatory reef fish species, such as kelp bass (Paralabax clathratus) and cabezon (Scorpaenichthys marmoratus), or semipelagic, large predatory species, such as Pacific barracuda (Sphyraena argentea) and yellowtail (Seriola lalandi). The proper disposition of the approximately 6000 marine offshore oil and gas platforms and associated structures now in service worldwide is in dispute. There are 27 platforms off California and, as in other parts of the world, there is considerable debate over the ultimate fate of these structures once they are uneconomical to operate (Schroeder and Love, 2004). In this article, we focus on the role that some artificial structures play as rockfish nursery habitat off California.

During some years, we have noted particularly high densities of YOY bocaccio (Sebastes paucispinis), widow (S. entomelas), squarespot (S. hopkinsi), and blue (S. mystinus) rockfishes around a number of these platforms. Similar high densities of young rockfishes were noted in the late 1950s at two nearshore platforms off Santa Barbara (Carlisle et al., 1964). The densities of YOY rockfishes are usually higher at platforms than at most natural outcrops (Schroeder et al., 2000; Love et al., 2003). As on natural outcrops, however, YOY rockfish recruitment to platforms is highly variable from year to year.

In 2003, while conducting fish surveys around eight oil platforms in southern California, we observed high densities of YOY rockfishes (e.g., bocaccio and widow rockfish), YOY lingcod (Ophiodon elongatus), and one-year-old vermilion rockfish (S. miniatus) (Fig. 1). Given the uncertainty regarding the role that platforms might play as fish habitat, we were interested in understanding how important young bocaccio, and by extension the platforms, might be to the stock and populations of this species in the region. Because of the severely overfished status of bocaccio and because a stock assessment model had been developed by NOAA Fisheries, we focused our attention on this species.

[FIGURE 1 OMITTED]

Along the Pacific Coast of...

NOTE: All illustrations and photos have been removed from this article.



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