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Predictions on the efficacy of marine reserves for benefiting fisheries differ in large part due to considerations of models of either intra- or inter-cohort population density regulating fish recruitment. Here, I consider both processes acting on recruitment and show using a bioeconomic model how for many fisheries density dependent recruitment dynamics interact with harvest costs to influence fishery profit with reserves. Reserves consolidate fishing effort, favoring fisheries that can profitably harvest low-density stocks of species where adult density mediates recruitment. Conversely, proportion coastline in reserves that maximizes profit, and relative improvement in profit from reserves over conventional management, decline with increasing harvest costs and the relative importance of intra-cohort density dependence. Reserves never increase profit when harvest cost is high, regardless of density dependent recruitment dynamics. I quantitatively synthesize diverse results in the literature, show disproportionate effects on the economic performance of reserves from considering only inter- or intra-cohort density dependence, and highlight fish population and fishery dynamics predicted to be complementary to reserve management.

Some studies suggest that fishery yields can be higher with reserves than under conventional management. However, the economic performance of fisheries depends on economic profit, not fish yield. The predictions of higher yields with reserves rely on intensive fishing pressures between reserves; the exorbitant costs of harvesting low-density populations erode profits. We incorporated this effect into a bioeconomic model to evaluate the economic performance of reserve-based management. Our results indicate that reserves can still benefit fisheries, even those targeting species that are expensive to harvest. However, in contrast to studies focused on yield, only a moderate proportion of the coast in reserves (with moderate harvest pressures outside reserves) is required to maximize profit. Furthermore, reserve area and harvest intensity can be traded off with little impact on profits, allowing for management flexibility while still providing higher profit than attainable under conventional management.

Lively debate continues over whether marine reserves can lead to increased fishery yields when compared to conventional, quota-based management, apparently driven by differences in the complexity and biological richness of the models being used. In an influential article, Hastings and Botsford used an analytically tractable, spatially implicit, non-age-structured model to assert that reserves are typically incapable of increasing yields relative to conventional management, regardless of the type (pre- or post-dispersal, involving adults and/or larvae) or functional form (Ricker or Beverton-Holt) of density dependence present. A recent numerical (simulation) model by Gaylord et al. concludes that reserves can enhance yield compared to conventional management, a result the authors attribute to their spatially-explicit evaluation of stage-structured adult growth, survivability and fecundity; and intercohort (adult-on-larvae) post-dispersal density dependent population dynamics. Here we demonstrate that the increased model complexity is not responsible for the different conclusions. We analyze a spatially-implicit model without stage structure that incorporates intercohort post-dispersal density dependence. In this simple model we still find annual extirpation of adult populations outside reserves due to fishing to enhance larval recruitment there, allowing for increased yields compared to those achieved when harvest is evenly spread across the entire domain under conventional management. Consideration of neither spatially-explicit dispersal dynamics nor stage-structure in adult demographics is required for reserves to substantially improve yield beyond that attainable under conventional management. In contrast, consideration of within cohort post-dispersal density dependence among larva during settlement in an otherwise identical model generates equivalence in yield between the two management strategies. These results recast a common message characterizing the relative benefit of reserve versus non-reserve management from "equivalence at best" to "potentially improved".

Periodically harvested closures are a widespread, centuries‐old form of fisheries management that protects fish between pulse harvests and can generate high harvest efficiency by reducing fish wariness of fishing gear. However, the ability for periodic closures to also support high fisheries yields and healthy marine ecosystems is uncertain, despite increased promotion of periodic closures for managing fisheries and conserving ecosystems in the Indo‐Pacific.We developed a bioeconomic fisheries model that considers changes in fish wariness, based on empirical field research, and quantified the extent to which periodic closures can simultaneously maximize harvest efficiency, fisheries yield and conservation of fish stocks.We found that periodic closures with a harvest schedule represented by closure for one to a few years between a single pulse harvest event can generate equivalent fisheries yield and stock abundance levels and greater harvest efficiency than achievable under conventional fisheries management with or without a permanent closure.Optimality of periodic closures at maximizing the triple objective of high harvest efficiency, high fisheries yield, and high stock abundance was robust to fish life history traits and to all but extreme levels of overfishing. With moderate overfishing, there emerged a trade‐off between periodic closures that maximized harvest efficiency and no‐take permanent closures that maximized yield; however, the gain in harvest efficiency outweighed the loss in yield for periodic closures when compared with permanent closures. Only with extreme overfishing, where fishing under nonspatial management would reduce the stock to ≤18% of its unfished level, was the harvest efficiency benefit too small for periodic closures to best meet the triple objective compared with permanent closures.Synthesis and applications. We show that periodically harvested closures can, in most cases, simultaneously maximize harvest efficiency, fisheries yield, and fish stock conservation beyond that achievable by no‐take permanent closures or nonspatial management. Our results also provide design guidance, indicating that short closure periods between pulse harvest events are most appropriate for well‐managed fisheries or areas with large periodic closures, whereas longer closure periods are more appropriate for small periodic closure areas and overfished systems. We show that periodically harvested closures can, in most cases, simultaneously maximize harvest efficiency, fisheries yield, and fish stock conservation beyond that achievable by no‐take permanent closures or nonspatial management. Our results also provide design guidance, indicating that short closure periods between pulse harvest events are most appropriate for well‐managed fisheries or areas with large periodic closures, whereas longer closure periods are more appropriate for small periodic closure areas and overfished systems. Editor's Choice [ABSTRACT FROM AUTHOR]

Abstract: Spatial variance in returns from natural resources, driven by resource dynamics and regulations, can have strong consequences for equitable delivery of value to individuals and communities. Yet resource management models implicitly weight returns equally across space, even when space is explicitly included in model dynamics and policy. Here we translate financial portfolio theory from the temporal to spatial realm and use it to quantify the inherent tradeoff between resource returns and social equity, defined as a more uniform distribution of resource value across space. We illustrate this approach with a marine case study of the Channel Islands, California, USA. Depending on the spatial distribution of resources, increasing spatial equity requires nonlinear reductions in resource returns. Realistic management options, such as effort-based fisheries regulations or marine protected areas, increase or reduce this tradeoff, respectively. We also quantify two critical advantages of portfolio approaches to management: they improve outcomes by avoiding false expectations and increase either resource return or social equity while maintaining the other. [Copyright &y& Elsevier]