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Map of the study region in the Northern Channel Islands, California (USA) (shading, binned number of Partnership for Interdisciplinary Studies of Coastal Oceans [PISCO] sampling events over the study period)

Map of the study region in the Northern Channel Islands, California (USA) (shading, binned number of Partnership for Interdisciplinary Studies of Coastal Oceans [PISCO] sampling events over the study period)

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Article
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Marine protected areas (MPAs) cover 3–7% of the world's ocean, and international organizations call for 30% coverage by 2030. Although numerous studies show that MPAs produce conservation benefits inside their borders, many MPAs are also justified on the grounds that they confer conservation benefits to the connected populations that span beyond th...

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... However, several factors can influence the relative performance of spatial management strategies, such as fishing effort, dispersal intensity and criteria for setting reserves (e.g., proportion, size and connectivity). Indeed, the spillover effect may not be sufficient in some cases to counteract the overexploitation of stocks outside the reserves due to displaced fishing effort (Hilborn 2018;Ovando et al. 2021). Moreover, marine dispersal capacity (especially larval dispersal) is likely to be higher than in freshwater habitats fostering the spillover effect of MPAs. ...
Article
Although the eco‐evolutionary consequences of dispersal and exploitation are increasingly recognised, consideration of these effects and how they interact for management and conservation remains limited. We addressed this gap by examining population exploitation within a metapopulation framework, using Atlantic salmon as a case study. We compared eco‐evolutionary consequences of alternative exploitation strategies by incorporating selective exploitation based on life‐history traits and spatial dimension of exploitation (i.e., whether populations were net exporters or importers of individuals). We used a demo‐genetic agent‐based model to examine demographic and evolutionary consequences of these strategies across a gradient of population‐specific exploitation rates. At the metapopulation scale, we found both lower abundance and earlier sexual maturation with increasing exploitation, particularly when fishing was selective on larger individuals. The spatial selectivity of exploitation had an overall additional detrimental effect on metapopulation performance and fisheries yield, and induced stronger evolutionary changes than when exploitation was evenly spread over all populations. We discuss the implications of metapopulation functioning for species management and how considering dispersal patterns and intensity might change how we apply harvest. Nevertheless, our findings suggest that the safest approach remains to distribute exploitation efforts evenly across all populations, especially in the absence of variation in intrinsic productivity. However, this strategy might not completely prevent negative consequences at the local scale. Therefore, we advise managers to critically assess the relevance of our results and dispersal assumptions in the specific cases they may have to deal with.
... Although MPAs are increasingly implemented to provide climate mitigation and resilience (Jacquemont et al., 2022;Roberts et al., 2017), or to increase fisheries yields or profits (Di Lorenzo et al., 2020;Gaines et al., 2010), many were originally envisioned primarily as tools to stimulate the recovery of overfished populations while protecting biodiversity and ecosystem functions (Salm & Clark, 1984). Whether MPAs promote climate resilience (Freedman et al., 2020;Johnson et al., 2022;Smith et al., 2023) or fisheries benefits (Ovando et al., 2021;Radici et al., 2023) is still a matter of debate (Arneth et al., 2023). By contrast, the conservation performance of MPAs-their ability to maintain higher biomass of harvested species, biodiversity, and ecosystem functioning relative to fished locations (Hernández-Andreu et al., 2024)-is widely documented (Claudet et al., 2008;Edgar et al., 2014;Gill et al., 2017;Lester & Halpern, 2008;Lester et al., 2009;Zupan et al., 2018) and remains the central objective of most MPA management plans . ...
... However, placement effects may provide other positive enabling conditions (such as more suitable habitat) that may be important in the design phase of networks. Furthermore, our finding of a positive (but lower relative to targeted species) increase in the biomass of nontargeted fish species supports an MPA effect because nontargeted species should not have a direct response to protection and, therefore, serve as a type of control measure (Caselle et al., 2015;Ovando et al., 2021). ...
Article
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Marine protected areas (MPAs) are widely implemented tools for long‐term ocean conservation and resource management. Assessments of MPA performance have largely focused on specific ecosystems individually and have rarely evaluated performance across multiple ecosystems either in an individual MPA or across an MPA network. We evaluated the conservation performance of 59 MPAs in California's large MPA network, which encompasses 4 primary ecosystems (surf zone, kelp forest, shallow reef, deep reef) and 4 bioregions, and identified MPA attributes that best explain performance. Using a meta‐analytic framework, we evaluated the ability of MPAs to conserve fish biomass, richness, and diversity. At the scale of the network and for 3 of 4 regions, the biomass of species targeted by fishing was positively associated with the level of regulatory protection and was greater inside no‐take MPAs, whereas species not targeted by fishing had similar biomass in MPAs and areas open to fishing. In contrast, species richness and diversity were not as strongly enhanced by MPA protection. The key features of conservation effectiveness included MPA age, preimplementation fisheries pressure, and habitat diversity. Important drivers of MPA effectiveness for single MPAs were consistent across MPAs in the network, spanning regions and ecosystems. With international targets aimed at protecting 30% of the world's oceans by 2030, MPA design and assessment frameworks should consider conservation performance at multiple ecologically relevant scales, from individual MPAs to MPA networks.
... As such, an experimental design approach to understanding what MPA network might achieve a given effect size for a given objective is not generally feasible. In the absence of experimental designs, observational studies lacking appropriate statistical controls can easily misdiagnose the effects of a spatial policy such as an MPA (Ovando et al. 2021;Ferraro et al. 2018). ...
... These results also only consider the simplest of economic dynamics (constant effort with or without MPA-driven effort displacement). Other works have shown that more complex fleet dynamics can greatly affect the outcomes of spatial policies (Ovando et al. 2021;Cabral et al. 2019;Miller and Deacon 2016). Violations of these assumptions used in this paper will further complicate the ability of a model to accurately predict the effects of an MPA on conservation and catch objectives. ...
... We have reached a point in quantitative ecology where our ability to model can far outpace our ability to monitor. The case of MPA science illustrates this challenge; while insidevs-outside gradients can be measured relatively easily (Lester et al. 2009), broader population-level effects of MPAs on conservation and fishery outcomes can span vast areas and take years to decades to fully evolve, constraining our ability to empirically measure their outcomes (Ovando et al. 2021;Fer-raro et al. 2018;Nickols et al. 2019). We must often depend on models for MPA planning without being able to confront them with data directly. ...
Article
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The use of marine protected areas (MPAs) is expanding around the world. MPAs can have a wide variety of objectives (e.g., science, conservation, food security, cultural value), and scientific guidance on how to design MPAs to achieve objectives is often based on simulation modeling. Many different models may all provide an answer to questions such as the predicted change in population biomass and fisheries catches resulting from th implementation of an MPA. When multiple levels of model complexity are all in theory capable of answering the same question, and the models cannot be confronted with data directly, the decision of what level of model complexity to use can be ad hoc. In this, paper I compare the predicted effects of MPAs on catch and biomass produced by a spatially explicit age-structured multi-species and multi-fleet (High-definition) model to the predictions generated by a two-patch surplus production (Low-definition) model, fitted to emulate the High-definition model. I found that in many cases, the predictions made by the two models were markedly different, with the Low-definition model frequently predicting substantially higher biomass benefits from MPAs than the High-definition model, and in some cases incorrectly estimating the direction (positive or negative) of the MPA effects. However, I also found that the Low-definition model has strategic value for broad classification and ranking exercises. My results show that care should be taken in selecting and interpreting the results of MPA simulation models and that research is needed to understand what models are best suited to what policy recommendations when multiple viable options exist.
... In the absence of appropriate controls, gradients could simply reflect pre-existing habitat gradients reflecting closed area placement choices. Ferraro et al. (2019) and Ovando et al. (2021) discuss these and other challenges of causal inference in spatial policies. ...
... Although the fishing pressure outside the closed area does increase when the closure is implemented, the effort does not continue to increase in order to try to catch the quota. This has been discussed in earlier papers on closed area modeling (e.g., Ovando et al. (2021)), but the key result relevant to the topic of this paper is that regardless of the dispersal rate or the level of fishing pressure, there will be gradients in abundance at the edge of a closed area. ...
... The results shown in Figs. 2 and 3 show that in a homogenous spatial environment, closing areas to fishing will lead to increases in abundance inside the closed area, net movement from inside the closed area to outside, and a density gradient at the boundary. This is totally consistent with all previous closed area models going back to Beverton and Holt's (1957) classic work and including Polacheck (1990), Hastings and Botsford (1999), White et al. (2011), andOvando et al. (2021). However, net movement from inside a closed area to outside does not necessarily demonstrate net benefits to either catch or CPUE (Tables 2 and 3). ...
Article
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Spillover is a term commonly applied to the dispersal of fish and/or larvae from inside a closed area to areas open to fishing. The presence of spillover is often quantified by measuring gradients in attributes such as abundance or catch rates near the boundaries of closed areas or by measuring higher abundance inside closed areas compared to outside. It is commonly assumed that such gradients or ratios indicate that the closed area has benefitted the fishery and the total abundance of fish. We explore this assumption using a spatially explicit model of closed areas with different intensities of fishing and fish movement, and we find that such gradients will be expected any time there is higher abundance inside the closed area. However, such gradients do not necessarily indicate a benefit to the fishery either in terms of total catch or catch rate, and unless pre-closure fishing was intense, total abundance is not expected to rise significantly. We examine case studies that argue that spillover exists and leads to fishery benefits. We then evaluate the evidence for net benefits in these case studies and find those with evidence of net benefits all come from places where fishing pressure was intense. While most analysis come from quite small coastal closed areas, two studies of very large open-ocean closed areas are discussed, and we find that both suggest little overall impact on the tuna populations that support the main commercial fisheries affected by the closures in question.
... This underscores the importance of considering multiple indices when implementing spatial fishing restrictions. Ultimately, understanding where fishing would increase after such an intervention, and how that would affect the total mortality rates from fishing, is one of the main challenges in designing protected areas successfully (Hilborn et al., 2004;Ovando et al., 2021). ...
Article
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Chondrichthyans (sharks, rays, skates, and chimaeras) make up one of the oldest and most ecologically diverse vertebrate groups, yet they face severe threats from fishing, necessitating improved management strategies. To effectively manage these species, we need to understand their spatial interactions with fisheries. However, this understanding is often challenged by limited data on chondrichthyan catches and species identification. In such cases, assessing potential risks from fishing activities can provide valuable insights into these spatial interactions. Here, we propose a method combining geostatistical models fitted to a fishery‐independent dataset with vessel monitoring system (VMS) data to estimate the spatial overlap between chondrichthyans and fishing. Our case study focuses on the western Adriatic Sea in the Mediterranean, examining the overlap between bottom trawling (including otter bottom trawling and beam trawling) and demersal chondrichthyans. We find that the northwestern part of the basin is a hotspot where threatened chondrichthyans (classified as Vulnerable, Endangered, or Critically Endangered by the International Union for Conservation of Nature Red List) greatly overlap with bottom trawling activities. Moreover, some areas, such as the northernmost part of the Adriatic and the “area dei fondi sporchi” in the north‐central offshore part, exhibit minimal overlap between threatened chondrichthyans and bottom trawling, potentially serving as refuges. We recommend prioritizing the management of otter bottom trawling in the northwestern basin to protect these threatened species, while also paying attention to the possible impacts of beam trawling on skates and chondrichthyan habitats. Despite certain limitations, our findings demonstrate that combining geostatistical models of species distributions with VMS data is a promising method for identifying areas of concern for species vulnerable to fishing. This approach can inform targeted management measures and cost‐effective onboard monitoring programs.
... Life-history theory suggests that FIE tends to favor individuals that grow slowly, mature early at a smaller size, and allocate more energy to reproduction (Jørgensen et al., 2007). With growing concerns surrounding the depletion of fishery resources, progress has been made in the restoration of specific fish populations through the implementation of science-based management, habitat preservation policies, fishing moratoriums, and fishery resource recovery strategies (Costello et al., 2016;Hilborn et al., 2020;Ovando et al., 2021;Zimmermann and Werner, 2019). However, FIE-induced changes have not been quantified for many depleted stocks and have not been integrated into fisheries management strategies. ...
... The first metric indicates that protection is occurring, relative to any larger-scale factors affecting both the MPA and the reference point, and the second metric indicates that there is successful long-term conservation of the local population. While more complex approaches can be used (e.g., Osenberg et al., 2011;Ovando et al., 2021), the effects of MPAs are often distilled into a response ratio value, typically calculated as the logarithm of the ratio of the response variable (e.g., population density) inside of the MPA to a reference site outside, to data collected before MPA implementation, or both. Positive log response ratios are typically taken to indicate success in achieving an MPA's conservation goals. ...
... The comparison approach used by MPA studies is based on the concept of detecting ecological impacts, such as the effects of a localized habitat disturbance (Schmitt & Osenberg, 1996). However, MPAs are not simple ecological experiments; by design, they have effects outside of their boundaries (Di Lorenzo et al., 2020;Grorud-Colvert et al., 2014;Ovando et al., 2021), are impacted by external factors (e.g., increased fishing pressure outside; Hopf et al., 2016b), and the dynamic responses can be nonlinear (Hopf et al., 2016a;White et al., 2013). For example, non-protected (reference) areas may be better off than expected due to larval export or adult spill-over from MPAs (e.g., Le Port et al., 2017), worse due to displaced fishing effort (e.g., Suuronen et al., 2010), or one may also off-set the other (Halpern et al., 2004). ...
Article
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Adaptively managing marine protected areas (MPAs) requires accurately assessing whether established MPAs are achieving their goals of protecting and conserving biomass, especially for harvested populations. Ecological MPA assessments commonly compare inside of the MPA to a reference point outside of and/or before implementation (i.e., calculating “response ratios”). Yet, MPAs are not simple ecological experiments; by design, protected populations interact with those outside, and population dynamic responses can be nonlinear. This complicates assessment interpretations. Here, we used a two‐patch population model to explore how MPA response ratios (outside–inside, before–after, and before–after‐control‐impact [BACI]) for fished populations behave under different conditions, like whether the population is receiving a sustainable larval supply or if it is declining despite protection from harvest. We then conducted a Bayesian evaluation of MPA effects on fish and invertebrate populations based on data collected from 82 published studies on 264 no‐take MPAs worldwide, using the results of an earlier global meta‐analysis as priors. We considered the effects of calculating different summary metrics on these results, drawing on the theoretical insights from our population model as a comparative framework. We demonstrate that not all response ratio comparison types provide the same information: For example, outside–inside and BACI comparisons can fail to detect population decline within MPAs, whereas before–after comparisons likely detect that pattern. Considering these limitations, we nonetheless found that MPAs globally are producing positive outcomes, with on average greater biomass, density, and organism size within their boundaries than reference sites. However, only a small portion of studies (18 of 82) provided the temporal data necessary to determine that protection, on average, has led to increased abundance of populations within MPAs over time. These findings demonstrate the importance of considering the underlying system dynamics when assessing MPA effects. Assuming that large outside–inside or BACI response ratios always reflect large and net positive conservation effects may lead to misleading conclusions, we recommend that: (1) when assessing specific MPA effects, empirical findings be considered alongside theoretical knowledge relevant to that MPA system, and (2) management should respond to the local conditions and outcomes, rather than a blanket expectation for positive MPA effects.
... To that end, marine protected areas (MPAs), where extractive activities such as fishing are restricted (Sala & Giakoumi 2018), are a common tool to reduce local impacts on marine systems (Selig & Bruno 2010;Halpern et al. 2010). Due to the interconnectedness of marine habitats, implementing groups of MPAs-an MPA network-can bridge the gap from local-to regional-scale conservation (Ovando et al. 2021;Colton et al. 2022). ...
... Guidelines for eco-evolutionary MPA network design suggest that protecting a diversity of environmental conditions can favor adaptation (Walsworth et al. 2019), partly because habitat representation of thermal regimes may be critical for maintaining the standing genetic variation of a coral reef network (Howells et al. 2013;Baums et al. 2019). However, few studies have explored the performance of MPA network designs on realistic seascapes (Mumby et al. 2011;Tong et al. 2021;Ovando et al. 2021), such that the effects of MPA network configuration on reef persistence remain unclear. Furthermore, while we understand which network attributes lead to persistence, there has been little to no attempt to apply those concepts to existing protection networks. ...
Preprint
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Ocean warming interacts with local stressors to negatively affect coral reefs. The adaptive capacity of reefs to survive these stressors is driven by ecological and evolutionary processes occurring at multiple spatial scales. Marine protected area (MPA) networks are one solution that can address both local and regional threats, yet the impacts of MPA network design on adaptive processes remains unclear. In this paper, we used an eco-evolutionary model to simulate hypothetical MPA configurations in the Caribbean, Southwest Pacific and Coral Triangle under projected warming. We found that protecting thermal refugia (i.e., cooler reefs) largely benefited corals inside the refugia while other reefs declined. In contrast, protecting a diverse habitat portfolio led to increased coral cover both inside and outside of the MPA network. We then quantified the thermal habitat and connectivity representations of reefs both inside and outside existing MPA networks across each region. Most strikingly, reefs in current MPA networks in the Southwest Pacific and Coral Triangle are approximately 2 °C cooler than reefs outside the MPA networks, while the Caribbean’s MPA network is approximately 1 °C warmer than reefs outside the network, based on mean temperatures from 2008-2018. These results suggest that the Caribbean MPA network is poised to protect sources of warm-adapted larvae but not destinations, and the opposite is true of the Southwest Pacific and Coral Triangle. Our results suggest that 1) by protecting sites with particular temperature and connectivity characteristics, marine spatial planning may alter eco-evolutionary processes to enhance or inhibit the adaptive capacity of a reef network and 2) the distribution, extent, and effectiveness of local interventions have the potential to affect regional distributions of coral cover beyond what would be expected from local benefits alone, due to the potentially wide-reaching effects of larval dispersal and gene flow.
... proportion, size, connectivity). Indeed, the spillover effect may not be sufficient in some cases to counteract the overexploitation of stocks outside the reserves due to displaced fishing effort (Hilborn, 2018;Ovando et al., 2021). Moreover, marine dispersal capacity (especially larval 462 dispersal) is likely to be higher than in freshwater habitats fostering the spillover effect of MPAs. ...
Preprint
Full-text available
While the eco-evolutionary consequences of dispersal and exploitation are increasingly recognized, consideration of these effects and how they interact for management and conservation remains limited. We addressed this gap by examining population exploitation within a metapopulation framework, using Atlantic salmon as a case study. We compared eco-evolutionary consequences of alternative exploitation strategies by incorporating selective exploitation based on life history traits and spatial dimension of exploitation (i.e., whether populations were net exporter or importer of individuals). We used a demo-genetic agent-based model to examine demographic and evolutionary consequences of these strategies across a gradient of population-specific exploitation rates. At the metapopulation scale, we found both lower abundance and earlier sexual maturation with increasing exploitation, particularly when fishing was selective on larger individuals. The spatial selectivity of exploitation had an overall additional detrimental effect on metapopulation performance and fisheries yield, and induced stronger evolutionary changes than when exploitation was evenly spread over all populations. We discuss the implications of metapopulation functioning for species management and how considering dispersal patterns and intensity might change how we apply harvest. Nevertheless, our findings suggest that the safest approach remains to distribute exploitation efforts evenly across all populations, especially in the absence of variation in intrinsic productivity and with the dispersal rates and spatial configuration simulated. However, this strategy might not completely prevent negative consequences at the local scale. Therefore, we advise managers to critically assess the relevance of our results and dispersal assumptions in the specific cases they may have to deal with.
... The effectiveness of MPAs globally has been widely debated for decades as the effect of MPAs depends on complex characteristics, including implementation period, size, level of protection, conformity with habitat boundaries, and regulation enforcement (Edgar et al., 2014;Strain et al., 2019). Compared to non-protected areas, MPAs enhance overall fish biomass (Motta et al., 2021), improve the presence of benthic, pelagic, and rare fish species (Boulanger et al., 2021), and positively influence targeted fin-fish populations (Ovando et al., 2021). No-take areas have shown a greater conservation impact on organism densities compared to partially protected areas (Lester & Halpern, 2008;Sciberras et al., 2015). ...
Article
Full-text available
Marine protected areas are set up across the globe to safeguard biodiversity and support coastal ecosystem functioning. In Hong Kong, partially protected marine parks and a no-take marine reserve have been managed under legislation for years. However, a comprehensive evaluation of their conservation impact is still pending despite the region's reputation for high marine diversity. Most studies assess conservation effectiveness solely in terms of taxonomic diversity without delving into the contributions of functional and phylogenetic diversity. In this study, we used environmental DNA combined with multifaceted diversity indicators to assess the impact of the level of protection on the fish community in Hong Kong waters. Our results indicated that the marine protected areas significantly contributed to fish community conservation. The no-take marine reserve exhibited the highest taxonomic and phylogenetic diversity, while partially protected marine parks showed the most balanced community composition. No significant increase in fish functional diversity was found in the protected areas. Water quality, hydrological condition, and protection level were the primary factors affecting community variation for taxonomic, functional, and phylogenetic diversity, respectively. Fish species composition significantly varied with different protection levels, and species turnover was the main component of the dissimilarity. Future management of marine protected areas should assess multifaceted biological indicators and establish a rational conservation scheme.