Adaptive capacity of co-management systems in the face of environmental change: The soft-shell clam fishery and invasive green crabs in Maine

Co-management, or regulatory decision-making through collaboration among user-groups, government officials, and scientists, has been proposed as an effective marine management tool in the face of environmental change. One potential advantage attributed to co-management is that such systems may have greater adaptive capacity than more conventional top-down management regimes. However, it is difficult to empirically test the relative adaptability of co-managed systems in the real world. This research uses a case study of the soft-shell clam fishery in Maine to investigate the question: Are co-managed systems better able to adapt to environmental change than are conventionally managed systems? This fishery provides an ideal system with which to address this question because (1) it is differentially managed, with some municipalities engaging in co-management and some in state management and (2) it faces an imminent environmental threat in the form of invasive predatory green crabs. This research first explores the scope of the green crab invasion in Maine, showing that although there have been no detectible impacts of green crabs on clam harvests to date, geographic overlaps of highly productive clam fisheries and high crab densities suggest a high likelihood of future impact. Second, to assess relative adaptability to this threat, this study quantifies differences between state- and co-managed systems across three attributes: user group stability, resource productivity, and institutional capacity to respond to change. It finds that co-managed clam fisheries have a higher degree of stability (i.e., a well defined user group), higher and more consistent productivity (i.e., more resources and incentives for sustained management), and greater institutional capacity to respond to change in the form of “conservation hours,” a flexible management tool employed in co-managed fisheries. These results indicate that co-managed clam fisheries are better prepared to adapt to environmental change than are conventionally managed fisheries.