A practical introduction to effective population size for fisheries management

Objective So far, many of the texts describing effective population size (Ne) offer technical descriptions that limit accessibility to nonspecialized audiences, hindering widespread uptake into natural resource management and biodiversity conservation. Our aim is to provide a practical introduction to Ne that is accessible to a wide audience, especially natural resource managers and other practitioners who lead decision-making efforts in fisheries contexts. Methods We summarize key concepts related to measuring and monitoring Ne in managed fish populations. We primarily focus on widely used linkage disequilibrium methods for measuring contemporary Ne. Among other topics, we review the value of Ne for conservation and management, basic assumptions of this parameter, common estimation methods, important study design considerations, and representative empirical examples. Additionally, we use simulations to explore two practical elements of studies aimed at inferring Ne: identifying an appropriate number of individuals to sample per population and a suitable number of molecular markers to survey across populations. Results Using accessible language, we illuminate the important role Ne plays in conserving and managing wild fish populations and describe practical elements related to estimating this parameter. Further, our simulations demonstrate the relationship among numbers of surveyed individuals and molecular markers on the accuracy and precision of Ne estimates, highlighting critical elements in the design of studies to measure Ne. Conclusions Together with more widely appreciated and implemented metrics, Ne forms a vital part of a complete tool kit for conserving and managing wild populations, including in fisheries contexts. While not a comprehensive review, our aim is that by providing a practical introduction to the complex concepts underlying Ne, we will facilitate increased conversation among practitioners with diverse areas of expertise and ultimately support expanded integration of this and related parameters into fisheries conservation and management efforts.