Marine Reserve Networks Research Articles

Examining horizontal and vertical social ties to achieve social–ecological fit in an emerging marine reserve network

Abstract Most MPA networks are designed only with ecological processes in mind to increase their conservation utility. However, since MPA networks often involve large geographic areas, they also affect and involve multiple actors, institutions, and policy sectors. A key challenge when establishing an effective MPA network is to align the ‘social system’ with the biophysical MPA network (the ‘ecological system’). This challenge is often denoted as ‘social–ecological fit’. Facilitating collaborative social interactions among various actors and stakeholders (social connectivity) is equally as important as accomplishing ecological connectivity. New analytical approaches are required to effectively examine this ‘social’ dimension of fit. An emerging marine reserve network in Jamaica and the recent invasion of Indo‐Pacific lionfish are used as a case study to: (1) examine the extent to which horizontal and vertical social ties bring local and national actors together to collaborate, coordinate, and share knowledge; and (2) assess the extent to which different attributes and features of such multilevel social networks may enhance or inhibit particular aspects of social–ecological fit. Findings suggest that multilevel linkages have played the greatest role in relation to enhancing fit in the marine reserve network in the context of the recent lionfish invasion. However, the long‐term propensity of the multi‐actor and multilevel networks to enhance social–ecological fit is uncertain given the prevalence of weak social ties, lack of a culture of information sharing and collaboration, and limited financial resources.

An assessment of the efficiency and ecological representativity of existing marine reserve networks in Wales, UK

Marine Protected Areas (MPA) are one of the several means of protecting ocean biodiversity and are fundamental to the Aichi Biodiversity Target 11 of 2010. However, many existing reserves are inefficient in meeting current conservation goals and are questioned regarding their habitat representivity. This paper assesses the efficiency of existing Welsh reserves in meeting conservation goals, including implications of changing objectives. Marxan conservation planning software was used to determine 20 broad-scale habitat types found in territorial seas, using data obtained from the European Environment Agency's Level 3 Predicted EUNIS Habitats GIS dataset. Results demonstrated that the current Welsh MPA network, even at the lowest conservation targets (≤10%), fails to suitably represent more than two-thirds of the broad-scale habitats found in its coastal waters. Subsequently, a range of alternative reserve design scenarios was developed to reduce inefficiency opportunity costs. Analysis indicated that an increase of less than 5% in total reserve area, plus a retention of 75% of the current network area, would create a new network to meet or exceed all stated conservation goals. Therefore, existing reserves can be incorporated into an efficient, ecologically representative network that reduces international conservation opportunity costs.

Larval fish dispersal in a coral-reef seascape.

Larval dispersal is a critical yet enigmatic process in the persistence and productivity of marine metapopulations. Empirical data on larval dispersal remain scarce, hindering the use of spatial management tools in efforts to sustain ocean biodiversity and fisheries. Here we document dispersal among subpopulations of clownfish (Amphiprion percula) and butterflyfish (Chaetodon vagabundus) from eight sites across a large seascape (10,000 km2) in Papua New Guinea across 2 years. Dispersal of clownfish was consistent between years, with mean observed dispersal distances of 15 km and 10 km in 2009 and 2011, respectively. A Laplacian statistical distribution (the dispersal kernel) predicted a mean dispersal distance of 13-19 km, with 90% of settlement occurring within 31-43 km. Mean dispersal distances were considerably greater (43-64 km) for butterflyfish, with kernels declining only gradually from spawning locations. We demonstrate that dispersal can be measured on spatial scales sufficient to inform the design of and test the performance of marine reserve networks.

Reef-fish larval dispersal patterns validate no-take marine reserve network connectivity that links human communities

Networks of no-take marine reserves (NTMRs) are a widely advocated strategy for managing coral reefs. However, uncertainty about the strength of population connectivity between individual reefs and NTMRs through larval dispersal remains a major obstacle to effective network design. In this study, larval dispersal among NTMRs and fishing grounds in the Philippines was inferred by conducting genetic parentage analysis on a coral-reef fish (Chaetodon vagabundus). Adult and juvenile fish were sampled intensively in an area encompassing approximately 90 km of coastline. Thirty-seven true parent-offspring pairs were accepted after screening 1978 juveniles against 1387 adults. The data showed all types of dispersal connections that may occur in NTMR networks, with assignments suggesting connectivity among NTMRs and fishing grounds (n = 35) far outnumbering those indicating self-recruitment (n = 2). Critically, half (51%) of the inferred occurrences of larval dispersal linked reefs managed by separate, independent municipalities and constituent villages, emphasising the need for nested collaborative management arrangements across management units to sustain NTMR networks. Larval dispersal appeared to be influenced by wind-driven seasonal reversals in the direction of surface currents. The best-fit larval dispersal kernel estimated from the parentage data predicted that 50% of larvae originating from a population would attempt to settle within 33 km, and 95% within 83 km. Mean larval dispersal distance was estimated to be 36.5 km. These results suggest that creating a network of closely spaced (less than a few tens of km apart) NTMRs can enhance recruitment for protected and fished populations throughout the NTMR network. The findings underscore major challenges for regional coral-reef management initiatives that must be addressed with priority: (1) strengthening management of NTMR networks across political or customary boundaries; and (2) achieving adequate population connectivity via larval dispersal to sustain reef-fish populations within these networks.

<i>Eretmochelys imbricata</i>: Lessons to Learn from a Monitoring Program in the North of Mozambique

Monitoring programs for nesting turtles around the world have been important to build up a matrix of information for better comprehension of their behaviour and dispersion. The Western Indian Ocean has several monitoring programs that are being used to reveal migration routes, phylogenetic interconnections and nesting behaviour patterns. We determined the nesting parameters for 69 records of hawksbill turtles collected during the Vamizi Island monitoring program. We also determined carapace measurements parameters of the turtles caught by fishermen in the area and give some considerations to improve the conservation of this species. Results show that the island receives hawksbill females all year long. Vamizi is a small nesting ground for this species, with an incubation period of 60.9 ± 10.6 days and a high reproductive rate. The turtles’ carapace measurements (SCL 42.0 ± SD 9.0 cm) revealed the existence of young individuals, foraging near the island, and their vulnerability to the fishing practices. This study strongly defends the need to identify more developmental and nesting spots, to be protected near Vamizi, to establish a solid network of marine reserves and corridors in the north of the Mozambique Channel.

Trade-offs between data resolution, accuracy, and cost when choosing information to plan reserves for coral reef ecosystems

Conservation planners must reconcile trade-offs associated with using biodiversity data of differing qualities to make decisions. Coarse habitat classifications are commonly used as surrogates to design marine reserve networks when fine-scale biodiversity data are incomplete or unavailable. Although finely-classified habitat maps provide more detail, they may have more misclassification errors, a common problem when remotely-sensed imagery is used. Despite these issues, planners rarely consider the effects of errors when choosing data for spatially explicit conservation prioritizations. Here we evaluate trade-offs between accuracy and resolution of hierarchical coral reef habitat data (geomorphology and benthic substrate) derived from remote sensing, in spatial planning for Kubulau District, Fiji. For both, we use accuracy information describing the probability that a mapped habitat classification is correct to design marine reserve networks that achieve habitat conservation targets, and demonstrate inadequacies of using habitat maps without accuracy data. We show that using more detailed habitat information ensures better representation of biogenic habitats (i.e. coral and seagrass), but leads to larger and more costly reserves, because these data have more misclassification errors, and are also more expensive to obtain. Reduced impacts on fishers are possible using coarsely-classified data, which are also more cost-effective for planning reserves if we account for data collection costs, but using these data may under-represent reef habitats that are important for fisheries and biodiversity, due to the maps low thematic resolution. Finally, we show that explicitly accounting for accuracy information in decisions maximizes the chance of successful conservation outcomes by reducing the risk of missing conservation representation targets, particularly when using finely classified data.

A Genuine Win‐Win: Resolving the “Conserve or Catch” Conflict in Marine Reserve Network Design

AbstractTo support fishing communities, reserves should ensure the persistence of meta‐populations while boosting fisheries yield. However, so far their design from the onset has rarely considered both objectives simultaneously. Here we overcome this barrier in designing a network of reserves for the Caribbean spiny lobster, a species with long larval duration for which local management is considered pointless because the benefits of protection are believed to be accrued elsewhere. Our reserve design approach uses spatially explicit population models and considers ontogenetic migration, larval and adult movement. We show that yield and persistence are negatively related, but that both objectives can be maximized simultaneously during planning. Importantly, we also show that local efforts to manage spiny lobster, the most economically valuable marine resource in the Caribbean, can result in locally accrued benefits, overcoming a major barrier to investing effort in the appropriate management of this species.

Conservation of marine biodiversity on a very large deep continental margin: how representative is a very large offshore reserve network for deep-water octocorals?

Aim: To evaluate the conservation performance of Australia's continental-scale network of marine reserves for deep-water octocorals using three criteria: (1) Representation: what fraction of the sampled deep-water octocoral fauna within Australia's marine jurisdiction is contained in reserves?; (2) Species turnover: to what degree do reserves share species with non-protected areas?; and (3) Biodiversity: do existing reserves spatially maximize protection of species richness? Location: Australia's continental exclusive economic zone and Norfolk Island region. Methods: A new Australia-wide, taxonomically consistent, dataset for distributions of deep-water octocorals (> 80 m depth) is used to calculate metrics of reserve performance for Australia's national marine reserve network. Results: Australia's reserve network represents 52% (270 of 518 species) of deep-water octocoral species. Coral representation is roughly proportional to spatial extent of reserves in different regions. The proportion of species with joint distributions in reserves and non-reserves ranges between 0% and 27% of the regional species pool; this may be a reflection of the high species turnover between sampling sites, and to some extent may also reflect sparse sampling coverage. Sites inside reserves have comparable species richness, contain similar numbers of rare species and do not differ in taxonomic diversity to sites outside reserves. Main conclusions: Australia's marine reserve network is a significant investment in conservation. The first broad biological evaluation of the network's performance, using deep-water octocorals, indicates that whilst the level of species representation is broadly proportional to the network's spatial coverage, reserves do not appear to be areas of significantly higher octocoral biodiversity compared to areas outside reserves and that there is low species representation within highly protected (IUCN I or II) zones. Considering constraints on reserve expansion and spatial re-configuration, ‘off-reserve’ management tools (e.g. fishery closures, environmentally responsible practices by extractive industries) are likely to be important to enhance overall conservation outcomes.

Uniting paradigms of connectivity in marine ecology.

The connectivity of marine organisms among habitat patches has been dominated by two independent paradigms with distinct conservation strategies. One paradigm is the dispersal of larvae on ocean currents, which suggests networks of marine reserves. The other is the demersal migration of animals from nursery to adult habitats, requiring the conservation of connected ecosystem corridors. Here, we suggest that a common driver, wave exposure, links larval and demersal connectivity across the seascape. To study the effect of linked connectivities on fish abundance at reefs, we parameterize a demographic model for The Bahamas seascape using maps of habitats, empirically forced models of wave exposure and spatially realistic three-dimensional hydrological models of larval dispersal. The integrated empirical-modeling approach enabled us to study linked connectivity on a scale not currently possible bypurely empirical studies. We find sheltered environments not only provide greater nursery habitat for juvenile fish but larvae spawned on adjacent reefs have higher retention, thereby creating a synergistic increase in fish abundance. Uniting connectivity paradigms to consider all life stages simultaneously can help explain the evolution of nursery habitat use and simplifies conservation advice: Reserves in sheltered environments have desirable characteristics for biodiversity conservation and can support local fisheries through adult spillover.

PRIVATE CONSERVATION IN TURF‐MANAGED FISHERIES

AbstractSpatial property rights in the ocean, such as territorial user right fisheries (TURFs), are increasingly used to overcome the tragedy of the commons. TURFs engender vastly different fishing incentives than in a common pool race; while this likely enhances conservation beyond an open access setting, conservation organizations may desire even greater protection. We argue that because TURFs are property rights, their implementation opens the door for “private conservation,” for example, where a conservation organization would purchase a set of TURFs to create an un‐fished marine reserve network. This possibility has interesting implications for biodiversity conservation, fishery management, and economic incentives, yet has received almost no attention in the literature. We examine this issue in a numerical spatial‐dynamic bioeconomic fishery model. Among other novel findings, we show: (i) Private acquisition of TURFs is likely to be a relatively inexpensive marine conservation strategy, particularly if the conservationist can capture some of the “conservation rents” that accrue due to spillover; (ii) Accounting for the strategic response of remaining fishermen can significantly reduce the cost of conservation; and (iii) The degree of fishing cooperation across TURFs plays a pivotal role in the costs of conservation; more‐cooperative TURF owners engage in more “free” conservation, dramatically reducing the overall costs of achieving a particular conservation target.

Marine systematic conservation planning for Rodrigues Island, western Indian Ocean

There is a growing number of Marine Protected Areas (MPAs) that have been selected and designed through participatory processes, following the recognition of the need to increase the involvement of local communities likely to be affected by such developments. In parallel with this shift has been the development of systematic conservation planning (SCP) tools that have increased our capacity to design MPAs to maximise biodiversity outcomes and to scale-up community-based initiatives into more comprehensive MPA networks. In Rodrigues, four Marine Reserves (no-take zones) in the north of the island were identified through participatory processes. A Marine Protected Area (multi-use), South East Marine Protected Area (SEMPA), has also been gazetted in the south of the island through a community-based approach. In order to verify and assess gaps in the stakeholder-based design, a Marine Reserve network was designed using the SCP tool Marxan using available spatial data on marine biotopes and fishing effort (FE) to achieve fisheries benefits and marine biodiversity protection. The Marxan analysis identified that only two of the four marine reserves achieve partly the objectives set and SEMPA contains planning units which can be considered as no take zones. This study shows the importance of using both stakeholder’s knowledge and scientific input for a better design of MPAs. The results from the analyses can be used by decision makers to inform decisions in a scientific way by providing a set of scenarios from the Marxan analysis.

Metapopulation dynamics guide marine reserve design: importance of connectivity, demographics, and stock enhancement

AbstractThe concepts of metapopulation persistence and source‐sink dynamics are central and often untested tenets of marine reserve networks. Effective application of these concepts to marine reserves is limited by data on demographic rates within reserves and larval connectivity among reserves. Using a network of reserves established to restore eastern oyster (Crassostrea virginica) in Pamlico Sound, North Carolina, USA as our model system, we integrated empirically based demographic rates and regional hydrodynamic‐based connectivity estimates within a metapopulation model to (1) evaluate the potential for the reserve network to function as a self‐persistent oyster metapopulation, (2) determine the relative importance of demographics vs. connectivity on reserve source‐sink dynamics, (3) assess the efficacy of stock enhancement in promoting metapopulation persistence, and (4) evaluate whether application of a Few Large or Several Small reserves—a modification of the Single Large or Several Small concept—promoted greater metapopulation retention of larvae within the reserve network (i.e., local larval retention within reserves + larval connectivity among reserves). The reserve network failed to function as a self‐persistent metapopulation, despite exceptional demographic rates within reserves. When considering only larval supply from reserves, local retention and connectivity were insufficient to provide annual replacement (≥~0.25 recruits per adult). Accordingly, reserves contributed to the metapopulation primarily via production, not dispersal, of larvae and reserve source‐sink dynamics were influenced more by demographics within reserves, particularly adult growth and survival, than larval connectivity among reserves. Addressing recruitment limitation via stock enhancement was not effective at augmenting projected metapopulation declines. Several small reserves initially promoted greater metapopulation retention of larvae than a few large reserves, however, as the number or area of reserves increased, metapopulation retention was equivalent among designs, suggesting that Few Large and Several Small reserves may be the best network design. Marine reserves can be an effective restoration tool for improving demographic rates within reserve boundaries, but designation of multiple reserves does not guarantee a functional reserve network metapopulation. Both demographics and larval connectivity are important considerations to successful application of metapopulation concepts to the design of reserve networks.

Planning Marine Reserve Networks for Both Feature Representation and Demographic Persistence Using Connectivity Patterns

Marine reserve networks must ensure the representation of important conservation features, and also guarantee the persistence of key populations. For many species, designing reserve networks is complicated by the absence or limited availability of spatial and life-history data. This is particularly true for data on larval dispersal, which has only recently become available. However, systematic conservation planning methods currently incorporate demographic processes through unsatisfactory surrogates. There are therefore two key challenges to designing marine reserve networks that achieve feature representation and demographic persistence constraints. First, constructing a method that efficiently incorporates persistence as well as complementary feature representation. Second, incorporating persistence using a mechanistic description of population viability, rather than a proxy such as size or distance. Here we construct a novel systematic conservation planning method that addresses both challenges, and parameterise it to design a hypothetical marine reserve network for fringing coral reefs in the Keppel Islands, Great Barrier Reef, Australia. For this application, we describe how demographic persistence goals can be constructed for an important reef fish species in the region, the bar-cheeked trout (Plectropomus maculatus). We compare reserve networks that are optimally designed for either feature representation or demographic persistence, with a reserve network that achieves both goals simultaneously. As well as being practically applicable, our analyses also provide general insights into marine reserve planning for both representation and demographic persistence. First, persistence constraints for dispersive organisms are likely to be much harder to achieve than representation targets, due to their greater complexity. Second, persistence and representation constraints pull the reserve network design process in divergent directions, making it difficult to efficiently achieve both constraints. Although our method can be readily applied to the data-rich Keppel Islands case study, we finally consider the factors that limit the method’s utility in information-poor contexts common in marine conservation.

Selective commercial line fishing and biodiversity conservation co-exist on seamounts in a deepwater marine reserve

Enhanced socio-economic and conservation outcomes for both an existing fishery and a new deep-water marine reserve off eastern Australia were achieved by research that identified additional options for conservation managers. Commercial power hand-line fishing was permitted to continue on productive seamount fishing grounds within the reserve because new information enabled boundaries and zoning proposed in the reserve’s draft Management Plan to be revised and consistent fisheries regulations to be formulated. The draft plan would have removed access to fishing grounds that provide approximately 25% of the annual regional Australian total allowable catch of the premium fishery species, Blue-eye Trevalla (Hyperoglyphe antarctica). Day-time power handline fishing in 280–550m depths on Taupo and Barcoo Seamounts avoided Harrisson’s Dogfish (Centrophorus harrissoni) – the primary species of conservation concern – because the shark is a diel vertical migrator, residing deeper than Blue-eye during the day before ascending to shallower depths at night to feed on micronekton. Harrisson’s Dogfish occurs on several other seamounts where it was previously unrecorded. These results, together with expectation of low mortality of any incidental dogfish bycatch and low impacts on benthic habitats, supported changes to management arrangements which preserve the seamount Blue-eye fishery worth approximately A$1M annually whilst protecting more seamounts and greater areas of benthic habitat in the restricted 200–700m depth range. Research uptake was facilitated by clarifying policy options at a critical stage in the planning process. This required having clearly articulated management objectives that aligned conservation and fishery imperatives, involving knowledgeable fishers in making robust field observations to address specific knowledge gaps and management needs, and identifying the requirements for ongoing fishery monitoring that addresses remaining management uncertainties. This potential to identify win-win outcomes in the Australian marine planning process provides some general signposts for future policy decisions as marine reserve networks are implemented and reviewed, and for scientists wanting to effectively engage in decision-making processes.

Spatio-Temporal Declines in Philippine Fisheries and its Implications to Coastal Municipal Fishers' Catch and Income

The problem of overexploitation in global fisheries is well-recognized. However, published assessment of fisheries spatio-temporal trends at the national scale is lacking for many high biodiversity developing countries, which is problematic since fisheries management is often implemented at the local or national levels. Here, we present the long-term spatio-temporal trends of Philippine fisheries production based on the landed national fish catch data (1980-2012) and fishers’ interviews. We found that the total Philippine fish catch volume (Metric Tons MT) of most capture fisheries throughout the country has either stagnated or declined over the last three decades. The decline is even more prominent when evaluating fisheries trends at the provincial level, suggesting spatial serial depletion of the country’s fisheries. In contrast, the total Philippine fish catch value (US Dollars US$ or Philippine Pesos PHP) has continued to increase over time, despite the declining fish catch volume. However, local municipal fishers are experiencing both low fish catch and income, contributing to observable poverty in many coastal communities in the Philippines. The various stakeholders of Philippine fisheries need to recognize the depleted state of Philippine fisheries, and learn from various experiences of collapsed and recovered fisheries from around the world, in order to recover the Philippines’ capture fisheries. Lessons from the literature on collapsed fisheries offer the following options for recovery: (1) regulate or reduce fisheries exploitation and other human activities impacting the fisheries to allow fisheries to rebuild or recover, (2) enforce effective networks of marine reserves, (3) engage fishers, consumers, and other stakeholders in fisheries management, (4) improve fisheries science, monitoring, and management capacities, and (5) provide alternative livelihood, skills, and improved education to fishers and their families.

Predicting reef fish connectivity from biogeographic patterns and larval dispersal modelling to inform the development of marine reserve networks

Developing networks of no-take marine reserves is often hindered by uncertainty in the extent to which local marine populations are connected to one another through larval dispersal and recruitment (connectivity). While patterns of connectivity can be predicted by larval dispersal models and validated by empirical methods, biogeographic approaches have rarely been used to investigate connectivity at spatial scales relevant to reserve networks (10's–100's of km). Here, species assemblage patterns in coral reef fish were used together with an individual-based model of dispersal of reef fish larvae to infer patterns of connectivity in a ∼300km wide region in the Philippines that included the Bohol Sea and adjacent bodies of water. A dominant current flows through the study region, which may facilitate connectivity among >100 no-take reserves. Connectivity was first investigated by analysing data on the presence/absence of 216 species of reef fish and habitat variables across 61 sites. Hierarchical clustering of sites reflecting species assemblage patterns distinguished a major group of sites in the Bohol Sea (Bray–Curtis similarity >70%) from sites situated in adjacent bodies of water (bays, channels between islands and a local sea). The grouping of sites could be partly explained by a combination of degree of embayment, % cover of sand and % cover of rubble (Spearman rank correlation, ρw=0.42). The individual-based model simulated dispersal of reef fish larvae monthly for three consecutive years in the region. The results of simulations, using a range of pelagic larval durations (15–45 days), were consistent with the species assemblage patterns. Sites in the model that showed strongest potential connectivity corresponded to the majority of sites that comprised the Bohol Sea group suggested by hierarchical clustering. Most sites in the model that exhibited weak connectivity were groups of sites which had fish assemblages that were least similar to those in the Bohol Sea group. Concurrent findings from the two approaches suggest a strong influence of local oceanography and geography on broad spatial patterns of connectivity. The predictions can be used as an initial basis to organise existing reserves to form ecologically meaningful networks. This study showed that species assemblage patterns could be a viable supplementary indicator of connectivity if used together with predictions from a larval dispersal model and if the potential effect of habitat on the structuring of species assemblages is taken into consideration.

Population Connectivity Measures of Fishery-Targeted Coral Reef Species to Inform Marine Reserve Network Design in Fiji.

Coral reef fish serve as food sources to coastal communities worldwide, yet are vulnerable to mounting anthropogenic pressures like overfishing and climate change. Marine reserve networks have become important tools for mitigating these pressures, and one of the most critical factors in determining their spatial design is the degree of connectivity among different populations of species prioritized for protection. To help inform the spatial design of an expanded reserve network in Fiji, we used rapidly evolving mitochondrial genes to investigate connectivity patterns of three coral reef species targeted by fisheries in Fiji: Epinephelus merra (Serranidae), Halichoeres trimaculatus (Labridae), and Holothuria atra (Holothuriidae). The two fish species, E. merra and Ha. trimaculatus, exhibited low genetic structuring and high amounts of gene flow, whereas the sea cucumber Ho. atra displayed high genetic partitioning and predominantly westward gene flow. The idiosyncratic patterns observed among these species indicate that patterns of connectivity in Fiji are likely determined by a combination of oceanographic and ecological characteristics. Our data indicate that in the cases of species with high connectivity, other factors such as representation or political availability may dictate where reserves are placed. In low connectivity species, ensuring upstream and downstream connections is critical.

Patterns, causes, and consequences of marine larval dispersal

Quantifying the probability of larval exchange among marine populations is key to predicting local population dynamics and optimizing networks of marine protected areas. The pattern of connectivity among populations can be described by the measurement of a dispersal kernel. However, a statistically robust, empirical dispersal kernel has been lacking for any marine species. Here, we use genetic parentage analysis to quantify a dispersal kernel for the reef fish Elacatinus lori, demonstrating that dispersal declines exponentially with distance. The spatial scale of dispersal is an order of magnitude less than previous estimates-the median dispersal distance is just 1.7 km and no dispersal events exceed 16.4 km despite intensive sampling out to 30 km from source. Overlaid on this strong pattern is subtle spatial variation, but neither pelagic larval duration nor direction is associated with the probability of successful dispersal. Given the strong relationship between distance and dispersal, we show that distance-driven logistic models have strong power to predict dispersal probabilities. Moreover, connectivity matrices generated from these models are congruent with empirical estimates of spatial genetic structure, suggesting that the pattern of dispersal we uncovered reflects long-term patterns of gene flow. These results challenge assumptions regarding the spatial scale and presumed predictors of marine population connectivity. We conclude that if marine reserve networks aim to connect whole communities of fishes and conserve biodiversity broadly, then reserves that are close in space (<10 km) will accommodate those members of the community that are short-distance dispersers.

Mapping Habitats and Developing Baselines in Offshore Marine Reserves with Little Prior Knowledge: A Critical Evaluation of a New Approach.

The recently declared Australian Commonwealth Marine Reserve (CMR) Network covers a total of 3.1 million km2 of continental shelf, slope, and abyssal habitat. Managing and conserving the biodiversity values within this network requires knowledge of the physical and biological assets that lie within its boundaries. Unfortunately very little is known about the habitats and biological assemblages of the continental shelf within the network, where diversity is richest and anthropogenic pressures are greatest. Effective management of the CMR estate into the future requires this knowledge gap to be filled efficiently and quantitatively. The challenge is particularly great for the shelf as multibeam echosounder (MBES) mapping, a key tool for identifying and quantifying habitat distribution, is time consuming in shallow depths, so full coverage mapping of the CMR shelf assets is unrealistic in the medium-term. Here we report on the results of a study undertaken in the Flinders Commonwealth Marine Reserve (southeast Australia) designed to test the benefits of two approaches to characterising shelf habitats: (i) MBES mapping of a continuous (~30 km2) area selected on the basis of its potential to include a range of seabed habitats that are potentially representative of the wider area, versus; (ii) a novel approach that uses targeted mapping of a greater number of smaller, but spatially balanced, locations using a Generalized Random Tessellation Stratified sample design. We present the first quantitative estimates of habitat type and sessile biological communities on the shelf of the Flinders reserve, the former based on three MBES analysis techniques. We contrast the quality of information that both survey approaches offer in combination with the three MBES analysis methods. The GRTS approach enables design based estimates of habitat types and sessile communities and also identifies potential biodiversity hotspots in the northwest corner of the reserve’s IUCN zone IV, and in locations close to shelf incising canyon heads. Design based estimates of habitats, however, vary substantially depending on the MBES analysis technique, highlighting the challenging nature of the reserve’s low profile reefs, and improvements that are needed when acquiring MBES data for small GRTS locations. We conclude that the two survey approaches are complementary and both have their place in a successful and flexible monitoring strategy; the emphasis on one method over the other should be considered on a case by case basis, taking into account the survey objectives and limitations imposed by the type of vessel, time available, size and location of the region where knowledge is required.

No-take marine reserves can enhance population persistence and support the fishery of abalone

A critical aspect in the design of a marine reserve (MR) network is its spatial configuration (i.e., the number, size, and spacing of the individual reserves), particularly how these features influence the effect on fisheries. Here, we derived a size-based, spatially explicit, stochastic demographic model to explore how different spatial configurations of MR networks can affect abundance and commercial yield of the green abalone (Haliotis fulgens), taking as a reference case the abalone fishery of Isla Natividad in Baja California Sur (Mexico). Our analysis suggests that a network of MRs can have a positive effect on abalone population abundance and a slightly negative effect on fishery output with respect to traditional maximum sustainable yield (MSY; i.e., with no reserves). Simulations show that maximum catches achievable with MRs are, under the best configuration, ∼2%–14% lower than traditional MSY depending on the total fraction of the fishing grounds protected. In the case of overexploitation, long-term yields can increase following the implementation of MRs. In addition, in the presence of MRs, abundances and yields are much less sensitive to systematic errors in the enforcement of the optimal harvesting rate compared with situations in which MRs are not present. Given the limited dispersal ability of the species, the best outcomes in terms of fishery output would be achieved with very small reserves — around 100 m wide — so to maximize larval export in the fishable areas. Our results indicate appropriately designed MR networks are an effective strategy for meeting both conservation and economic goals under uncertainty. While the size of the existing reserves in Isla Natividad seems adequate to protect the abalone stock, smaller reserves could maximize fishery benefits, although this poses challenges for enforcement.