Conservation, Spillover and Gene Flow within a Network of Northern European Marine Protected Areas

Mats Brockstedt Olsen Huserbråten,Even Moland,Esben Moland Olsen,Nils Chr Stenseth,Halvor Knutsen,Carl André,Jan Geert Hiddink

doi:10.1371/journal.pone.0073388

Mats Brockstedt Olsen Huserbråten, Even Moland + Show 5 more

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https://doi.org/10.1371/journal.pone.0073388

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Abstract

To ensure that marine protected areas (MPAs) benefit conservation and fisheries, the effectiveness of MPA designs has to be evaluated in field studies. Using an interdisciplinary approach, we empirically assessed the design of a network of northern MPAs where fishing for European lobster ( Homarusgammarus ) is prohibited. First, we demonstrate a high level of residency and survival (50%) for almost a year (363 days) within MPAs, despite small MPA sizes (0.5-1 km2). Second, we demonstrate limited export (4.7%) of lobsters tagged within MPAs (N = 1810) to neighbouring fished areas, over a median distance of 1.6 km out to maximum 21 km away from MPA centres. In comparison, median movement distance of lobsters recaptured within MPAs was 164 m, and recapture rate was high (40%). Third, we demonstrate a high level of gene flow within the study region, with an estimated F ST of less than 0.0001 over a ≈ 400 km coastline. Thus, the restricted movement of older life stages, combined with a high level of gene flow suggests that connectivity is primarily driven by larval drift. Larval export from the MPAs can most likely affect areas far beyond their borders. Our findings are of high importance for the design of MPA networks for sedentary species with pelagic early life stages.

Highlights

Marine protected areas (MPAs) and marine reserves are increasingly recognised as tools to rebuild marine ecosystems and fisheries suffering from overexploitation [1,2]
Total recapture percentage within reserves was 40% and mean recapture percentage within the three reserves was 41%
Through a multidisciplinary empirical approach, this study aimed to quantify the level of protection, spillover, and gene flow of a harvested species, the European lobster, within a network of MPAs

Summary

Introduction

Marine protected areas (MPAs) and marine reserves are increasingly recognised as tools to rebuild marine ecosystems and fisheries suffering from overexploitation [1,2]. A measurable effect of a marine reserve is net export of adults and juveniles from reserves and into adjacent, fished areas (spillover) [5]. Protecting large, highly fecund individuals within reserves may lead to increased export of pelagic eggs and larvae (recruitment benefits) [6]. To ensure both conservation and fisheries benefits of reserves, there should be a balance between protection and spillover–a balance regulated by reserve design [7]. Measuring gene flow by genetic markers can elucidate both magnitude and distance of effective larval dispersal [8,9,10]. Estimates of larval dispersal distances can subsequently be used to optimise reserve placing within a network, ensuring connectivity among reserves [11], which in turn increases sustainability of reserves [12]

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