A modelling study of the role of marine protected areas in metapopulation genetic connectivity in Delaware Bay oysters

Abstract

Management decisions concerning location and extent of marine protected areas (MPAs) both for exploited and unexploited resources rely on understanding how populations are interconnected.The potential effects of MPA location and external fishing pressure on genetic connectivity of eastern oyster (Crassostrea virginica) populations in Delaware Bay were examined.An individual‐based metapopulation model that includes post‐settlement population dynamics, larval dispersal, and genetic structure was used to simulate four oyster populations for two periods (1970s and 2000s) with distinct population and environmental conditions. Sensitivity analysis examined the influence of larval dispersal, and simulations included combinations of MPA location (which population was protected) and three fishing mortality rates for non‐MPA populations: low (4%), medium (8%) and high (30%); no fishing was allowed in the MPAs.Results showed (i) salinity‐driven changes in larval dispersal led to relatively small, population‐specific connectivity changes, (ii) MPAs can enhance the frequency of genotypes originating within protected populations in unprotected populations when fishing rates are high (30%), and (iii) demographic shifts can impose temporal variability on the influence of MPAs on connectivity.These results suggest that genetic consequences of siting MPAs must be considered in terms of present population and environmental conditions, as well as allowing for changes in population and genetic connectivity that may shift fundamentally over time.Simulation results indicate that siting protected areas for oyster restoration in low salinity (<12ppt) regions may interact with development of disease resistance in the metapopulation by altering genotype transfer from protected to unprotected downestuary populations. Copyright © 2013 John Wiley & Sons, Ltd.

The Ecological and Evolutionary Consequences of Marine Reserves

“…Greater genetic diversity has been observed in reserves compared with harvested areas for a metric that did not naturally exhibit spatial structure in genetic variation (Pérez-Ruzafa et al 2006). For organisms with spatial genetic structure on the scale of reserve size, theory indicates that the heterogeneity in population size imposed by reserves can alter patterns of genetic connectivity and allele distributions in space and, therefore, genetic diversity on the metapopulation level (Munroe et al 2014). In addition to spatial patterns of genetic diversity, fisheries and marine reserves have the potential to alter the genetics and evolution of marine populations through changes in the selective pressures acting on heritable traits.…”

Variation that can be expected when using particle tracking models in connectivity studies

“…Where larvae in these early approaches have been treated generally as "passive" particles different shades of complexity have since then been included and now mimic behavior like selective tidal transport or stage related vertical distribution pattern (Fox et al 2006, van der Molenet al 2007Bolle et al, 2009;Savina et al, 2010;Lacroix et al, 2013), physiology Kühn et al, 2008;Fiksen and Jørgensen, 2011;Daewel et al, 2011a,b) or mortality (see review by Peck & Hufnagl, 2012). With respect to the connectivity criterion of marine protected areas, OCMs and Lagrangian models have recently been used to also advice spatial planning and management in different regions (Delpeche-Ellmann and Soomere, 2013; Munroe et al, 2014;Engie and Klinger, 2007;Koeck et al, 2015). Coastal and shallow areas, are often used by several species as juvenile nursery area while eggs are generally spawned further offshore or in different locations.…”

Oysters beget shell and vice versa: generating management goals for live oysters and the associated reef to promote maximum sustainable yield of Crassostrea virginica

“…These groups rest within the salinity gradient that drives mortality and productivity (Bushek et al 2012). The LM group was excluded from the following model simulations because recruitment in this region is limited to self-recruitment and minimal up-estuary transport of larvae, rather than available substrate for settlement (Narváez et al 2012a(Narváez et al , 2012bMunroe et al 2013Munroe et al , 2014Hemeon et al 2020). The singularity of SR, a one-bed group, originates from its high productivity.…”

“…Area management is essential for oysters due to the strong influence of the salinity gradient on growth, recruitment, and mortality, though it is challenging to accomplish, as all metrics used to evaluate stock status must be local. Growth rate and mortality are inherently local, but recruitment in its classic form (broodstock-recruitment) is evaluated for either the whole stock or within a connected component of the stock, though the region of connectivity is often hard to judge (Narváez et al 2012a(Narváez et al , 2012bMunroe et al 2013Munroe et al , 2014. The new formulation overcomes this impediment, as ESA is inherently local.…”