Consequences of alternative decommissioning options to reef fish assemblages and implications for decommissioning policy

Abstract

From Significant Conclusions: “Fish assemblages on the production platforms and nearby natural reefs we studied differed in species composition and relative abundance. These differences stem from differences in the structural features of these two habitats (e.g., absence and presence of macroalgae), the surrounding landscape (platforms are located in deeper water further from shore and are isolated by deep water from natural reefs), and the unique vertical extension of platform structure from the bottom to the sea surface. Vertical stratification of different species and life stages indicate that decommissioning options that reduce the height of platforms will alter the abundance of species and the overall fish assemblage associated with such structures. Patterns of size structure and movement of some species strongly suggests that these species may recruit to natural reefs and migrate to platforms as older stages. Other species (e.g., surfperch) have such limited movement that they do not appear to migrate to platforms. Patterns of movement in the opposite direction may be substantial as well, however we were not able to conduct extensive tagging efforts on our study platforms. This is another research effort that would be useful to better understanding the role of platforms to regional fish populations.

We show that state and federal decommissioning policymaking is based on economic and ecological factors that reflect particular regional and political settings. In the Gulf region, the rigs-to-reefs “idea” was less an invention and more a mutation of an old idea. The rigs-to-reefs idea represented the coupling of an already familiar activity of building artificial reefs in the Gulf to enhance commercial and recreational fisheries. The use of familiar ideas, such as the idea of artificial reef building in the Gulf, by policy entrepreneurs and experts is referred to as the “act of recombination”. The rigs-to-reef policy idea represented a recombination of an old solution (the reliance on artificial reefs to enhance fisheries) to a perceived new problem (the lack of natural habitat and potential economic impacts associated with complete removal of OCS oil and gas structures). The role of ecological research in the development of decommissioning policy in the Gulf region can be characterized as strongly supportive and directed at identifying the contribution of platforms to the enhancement of fisheries.

In southern California, the political debate over the decommissioning of oil and gas structures involves the intermingling of ecological information, economic factors, preferences and interests associated with OCS oil and gas activity. The southern California context is much different from that of the Gulf experience. Gulf states are willing to accept the rigs-to-reefs alternative, and have developed state policy and programs. Gulf state rigs-to-reefs programs continue to serve the needs and interests of commercial and sports fishing industries. In California, state legislation that could lead to the creation of a state rigs-to-reefs program under the California Department of Fish and Game has been introduced repeatedly. That legislation has been rejected for several reasons, political reasons and an expression of scientific uncertainty and mixed conclusions among marine ecologists in that region. We describe the ecological, economic and historical factors that are part of the California rigs-to-reefs debate and the roles that ecological information appears to have influenced the development of decommissioning policy.”