A decision tree to guide precautionary and adaptive tiering in marine nursery identification and management

Many marine species depend on nurseries during early life stages to promote growth and increase survival to maturity, supporting stock replenishment and stability. Since the nursery was first formally defined 25 years ago as a habitat that yields a greater-than-average contribution of juvenile recruits to an adult population, researchers have repeatedly revisited the concept and debated the best nursery identification approach to balance both ecological complexity and management practicality. The sustained research interest has produced several alternative frameworks broadly categorizable as production-, persistence-, or connectivity-oriented. However, existing frameworks remain difficult to apply in high-priority and data-poor contexts. While persistence metrics have been applied to site fisheries restricted areas in the Mediterranean, no proposed metrics have been incorporated into U.S. fisheries management plans. To address the definitional ambiguity and research-management disconnect, we review the major topics of nursery literature and synthesize the discourse and research with a decision tree to guide the adaptive designation of four nursery tiers—Candidate, Putative, Confirmed, and Refined Nurseries—where the degree of precaution scales with management urgency, socioeconomic importance, system uncertainty, data availability, population accessibility, research capacity, and species ecology. We then compile potential interventions for each nursery tier and list risk management tools with which they can be paired to support the socioeconomic and political viability of precautious approaches. Finally, we provide three hypothetical examples of the application of this novel tiered approach to nursery management for three shark taxa, considering examples from both biodiversity conservation and fishery sustainability contexts. This approach seeks to bridge the gap between research and management and realign the nursery concept with the core precautionary and adaptive principles of ecosystem-based management.