The Role of Oil and Gas Conductors as Fish Habitat at Two Southern California Offshore Platforms

Abstract

Abstract. Worldwide, all oil and gas offshore platforms contain conductors, a series of closely spaced vertical pipes, that carry oil and gas from the wells. During decommissioning, these conductors are usually removed. However, worldwide, there has been no research on the relationship between conductor arrays and fish densities. During summer and fall of 2017 and 2018, at Platforms Holly and A, in the Santa Barbara Channel, California, we conducted visual scuba surveys of the fish densities associated with 1) conductors, 2) crossbeams, and 3) blue (open) water under these platforms. A minimum of 14 species were observed at Platform Holly and 14 species at Platform A. Substantially more fishes, and higher densities, were observed at Holly (17,533, 636 per 100 m–2, respectively) than at A (1,185, 171 per 100 m2). Although there were similarities, the dominant species at the two platforms were distinct. Rockfishes (genus Sebastes), particularly Sebastes hopkinsi, dominated the Holly assemblage, while the damselfish, Chromis punctipinnis, was the most abundant at A. Overall, at both platforms, there was no statistical difference between fish densities at conductors and at crossbeams and fish densities were higher at both conductors and crossbeams when compared to those in blue water. The species assemblage among three habitats were similar, although there were two survey occasions where no fish were observed in blue water. Our research strongly suggests that, to the extent possible, retaining conductors during partial removal will likely have a positive influence on both fish diversity and fish abundance, during at least some years.