Comparing Potential Larval Production of Bocaccio (Sebastes paucispinis) and Cowcod (Sebastes levis) around Oil Platforms and Natural Outcrops off California

There is increasing evidence that some central and southern California oil platforms form important habitats for a number of economically important fishes. Given the overfished status of several of these species, we asked to what extent might platforms be important as producers of larvae of these species on a local, or even regional, basis. Love conducted a pilot study that focused on bocaccio (Sebastes paucispinis Ayres, 1854) and cowcod (S. levis Eigenmann and Eigenmann, 1889), two overfished species, comparing adult densities and potential larval export of these species at platforms and natural outcrops in central and southern California. Densities of mature bocaccio and cowcod were highly variable among survey sites, but were generally very low at both natural reefs and platform habitats. However, the mean densities for both species around platforms were higher than at natural reefs. In addition, two of the three platforms (Gail and Hidalgo) that harbored mature bocaccio had larger mature individuals than did any natural reef. Platform Gail had by far the highest densities of both mature bocaccio and cowcod of any natural or human-made habitat. Because of these very high densities, the potential larval production of both species at Platform Gail was much higher than at any other site surveyed. We estimated that for bocaccio one hectare of sea floor at that platform was equivalent to 68 hectares at an average natural reef and for cowcod one platform hectare was equivalent to 26 at the average natural reef.

Status: Submitted to Bulletin of Marine Science

A comparison of the Fish Assemblages Associated with an Oil/Gas Pipeline and Adjacent Seafloor in the Santa Barbara Channel, Southern California Bight. This paper summarizes comparisons of the fishes that live on the platform Gail-Grace pipeline and the surrounding seafloor. Based on differences in fish assemblages, Love found there were four habitats (shallow and deep pipeline and shallow and deep seafloor). Fish densities along the shallow portion of the pipeline were about seven times higher than on the adjacent seafloor and densities along the deep pipeline portion were nearly six times that of the deeper seafloor. Along the pipeline, rockfishes comprised 84% of the fishes and included 22 species. Unidentified sanddabs (probably most or all Citharichthys sordidus), forming 33.2%, and combfishes (Zaniolepis frenata and Z. latipinnis), comprising 19% of the total, were most often observed on the seafloor. Most of the fishes living on the pipeline were either juveniles of such larger species, such as blackgill, flag, and vermilion rockfishes, cowcod, and lingcod or dwarf species such as halfbanded and stripetail rockfishes, combfishes, and poachers (Family Agonidae). Of particular interest were the relatively high densities of juvenile cowcod along the deeper parts of the pipeline, densities that were far higher than any seen at over 80 natural outcrops and at ten platforms.

Status: Bulletin of Marine Science, in press.

Do Oil and Gas Platforms off California Affect the Fate of Recruiting Bocaccio (Sebastes paucispinis)? An Analysis Based On High Frequency Radar Derived Surface Trajectories.

Does recruitment of high densities of many species of juvenile rockfishes (Sebastes spp.) from the plankton to some oil and gas platforms off southern and central California reduce recruitment to natural nursery habitat? To investigate the likelihood of a platform interfering with the transport of recruiting pelagic juvenile fishes to natural nursery habitat, Love’s group estimated the proportion of fish recruiting to a platform that would arrive at natural juvenile habitat in the absence of that platform. In this study, they simulated the surface current movements originating at Platform Irene, located west of Point Conception, during the bocaccio (Sebastes paucispinis) recruiting seasons, May through August, of 1999 and 2002 using high frequency radar current measurements. Their results from 1999 and 2002 indicate that 7% and 23%, respectively, of the young fishes would have survived to shallow water natural nursery habitat. Thus, they predict that the vast majority of the juvenile bocaccio settling on the platform during the recruitment season would have perished if that structure did not exist. If this is correct, the platform helped produce bocaccio.

Status: Submitted to Fishery Bulletin