The purpose of this study was to survey offshore oil and gas platforms in the Santa Barbara Channel/Santa Maria Basin and San Pedro Basin, other artificial structures, and natural reefs for the non-native species Watersipora subatra (previously identified as Watersipora subtorquata), measure the reproductive seasonality of this species, and identify potential vectors for dispersal among platforms and between platforms and natural habitat. The need for this information is to elucidate the role that offshore artificial structures may have in affecting biological communities for use by the State of California in evaluating decommissioning options under California legislation AB 2503 (the California Marine Resources Legacy Act) and to comply with the duties of Federal agencies that are outlined in Section 2 of Executive Order 13112 (Invasive Species). BOEM will use study results for environmental reviews pertaining to ongoing operations and decommissioning alternatives of offshore oil and gas platforms and potential marine renewable energy facilities. This study also developed results applicable specifically for BSEE management decisions so that BSEE can specify requirements to industry or other interested parties when decommissioning occurs. Using the results, the State of California can ensure proper evaluation under the California Rigs-to-Reefs Program law AB 2503 (the California Marine Resources Legacy Act) and BSEE can ensure that specified criteria can be properly evaluated during the decommissioning process pursuant to the federal regulations at 30 CFR 250.1730.