Fishers' ecological knowledge points to fishing-induced changes in the Peruvian Amazon.

Scientists increasingly draw on fishers' ecological knowledge (FEK) to gain a better understanding of fish biology and ecology, and inform options for fisheries management. We report on a study of FEK among fishers along the Lower Ucayali River in Peru, a region of exceptional productivity and diversity, which is also a major supplier of fish to the largest city in the Peruvian Amazon. Given a lack of available scientific information on stock status, we sought to identify temporal changes in the composition and size of exploited species by interviewing fishers from 18 communities who vary in years of fishing experience since the mid-1950s. We develop four FEK-based indicators to assess changes in the fish assemblage and compare findings with landings data. We find an intensification of fishing gear deployed over time and spatiotemporal shifts in the fish assemblage and reported declines in species weight, which point to a fishing-down process with declines across multiple species. This finding is reflected in a shifting baseline among our participants, whereby younger generations of fishers have different expectations regarding the distribution and size of species. Our study points to the importance of spillover effects from the nearby Pacaya-Samira National Reserve and community initiatives to support the regional fishery. Reference to fishers' knowledge also suggests that species decline is likely underreported in aggregated landings data. Despite the dynamism and diversity of Amazonian floodplain fisheries, simple FEK-based indicators can provide useful information for understanding fishing-induced changes in the fish assemblage. Fishers hold valuable knowledge for fishery management and conservation initiatives in the region.

Stable landings mask irreversible community reorganizations in an overexploited Mediterranean ecosystem.

Cumulative human pressures and climate change can induce nonlinear discontinuous dynamics in ecosystems, known as regime shifts. Regime shifts typically imply hysteresis, a lacking or delayed system response when pressures are reverted, which can frustrate restoration efforts. Here, we investigate whether the northern Adriatic Sea fish and macroinvertebrate community, as depicted by commercial fishery landings, has undergone regime shifts over the last 40 years, and the reversibility of such changes. We use a stochastic cusp model to show that, under the interactive effect of fishing pressure and water warming, the community reorganized through discontinuous changes. We found that part of the community has now reached a new stable state, implying that a recovery towards previous baselines might be impossible. Interestingly, total landings remained constant across decades, masking the low resilience of the community. Our study reveals the importance of carefully assessing regime shifts and resilience in marine ecosystems under cumulative pressures and advocates for their inclusion into management.

A classification framework for interspecific trade-offs in aquatic ecology.

In some cases, wildlife management objectives directed at multiple species can conflict with one another, creating species trade-offs. For managers to effectively identify trade-offs and avoid their undesirable outcomes, they must understand the agents involved and their corresponding interactions. A literature review of interspecific trade-offs within freshwater and marine ecosystems was conducted to illustrate the scope of potential interspecific trade-offs that may occur. We identified common pitfalls that lead to failed recognition of interspecific trade-offs, including, single-species management and limited consideration of the spatial and temporal scale of ecosystems and their management regimes. We devised a classification framework of common interspecific trade-offs within aquatic systems. The classification can help managers determine whether the conflict is species based through direct relationships (i.e., predator-prey, competition, other antagonistic relationships) or indirect relationships involving intermediate species (i.e., conflict-generating species) or whether the conflict is driven by opposing management objectives for species that would otherwise not interact (i.e., nontarget management effects). Once the nature and scope of trade-offs are understood, existing decision-making tools, such as structured decision-making and real-options analysis, can be incorporated to improve the management of aquatic ecosystems. Article Impact Statement: A synthesis of interspecific trade-offs in aquatic ecosystems supports their identification and resolution.

Un Marco de Clasificación para Compensaciones Interespecíficas en Ecología Acuática Resumen En algunos casos, los objetivos del manejo de fauna dirigidos a muchas especies pueden entrar en conflicto entre sí creando compensaciones entre las especies. Para que los manejadores identifiquen efectivamente estas compensaciones y eviten sus resultados no deseados, deben entender a los agentes involucrados y sus interacciones correspondientes. Se realizó una revisión literaria de las compensaciones interespecíficas dentro de los ecosistemas marinos y de agua dulce para ilustrar el alcance de las compensaciones interespecíficas que pueden ocurrir. Identificamos dificultades comunes que llevan al reconocimiento fallido de las compensaciones interespecíficas, incluyendo el manejo de una sola especie y sus regímenes de manejo. Diseñamos un marco de clasificación de compensaciones interespecíficas comunes dentro de los ecosistemas acuáticos. La clasificación puede ayudar a los manejadores a determinar si el conflicto está basado en las especies por sus relaciones directas (es decir, depredador-presa, competencia, otras relaciones antagonistas) o por relaciones indirectas que involucran a otras especies (es decir, efectos del manejo de especies que no son el objetivo). Una vez que se entiende la naturaleza y el alcance de las compensaciones, las herramientas de toma de decisión existentes, como la toma estructurada de decisiones y el análisis de opciones reales, pueden incorporarse para mejorar el manejo de los ecosistemas acuáticos.

The Genetic Population Structure of Lake Tanganyika's Lates Species Flock, an Endemic Radiation of Pelagic Top Predators.

Understanding genetic connectivity plays a crucial role in species conservation decisions, and genetic connectivity is an important component of modern fisheries management. In this study, we investigated the population genetics of four endemic Lates species of Lake Tanganyika (Lates stappersii, L. microlepis, L. mariae, and L. angustifrons) using reduced-representation genomic sequencing methods. We find the four species to be strongly differentiated from one another (mean interspecific FST = 0.665), with no evidence for contemporary admixture. We also find evidence for strong genetic structure within L. mariae, with the majority of individuals from the most southern sampling site forming a genetic group that is distinct from the individuals at other sampling sites. We find evidence for much weaker structure within the other three species (L. stappersii, L. microlepis, and L. angustifrons). Our ability to detect this weak structure despite small and unbalanced sample sizes and imprecise geographic sampling locations suggests the possibility for further structure undetected in our study. We call for further research into the origins of the genetic differentiation in these four species-particularly that of L. mariae-which may be important for conservation and management of this culturally and economically important clade of fishes.

Designing combinatorial exchanges for the reallocation of resource rights.

We describe the design and implementation of a combinatorial exchange for trading catch shares in New South Wales, Australia. The exchange ended a decades-long political debate by providing a market-based response to a major policy problem faced by fisheries worldwide: the reallocation of catch shares in cap-and-trade programs designed to prevent overfishing. The exchange was conducted over the Internet to lower participation costs and allowed for all-or-nothing orders to avoid fragmented share portfolios. A subsidy was distributed endogenously to facilitate the transfer of shares from inactive to active fishers. Finally, prices were linear and anonymous to ensure that sellers of identical packages received the same payments. These features were crucial to mitigate economic distortions from introducing catch shares and to gain broad acceptance of the program. However, they led to computationally challenging allocation and pricing problems. The exchange operated from May to July 2017 and effectively reallocated shares from inactive fishers to those who needed them most: 86% of active fishers' bids were matched and their share deficits were reduced by 95% in high-priority share classes. Similar reallocation problems arise in fisheries with catch-share systems worldwide as well as in other cap-and-trade systems for resource rights, e.g., water and pollution rights. The implemented exchange illustrates how computational optimization and market design can provide policy tools, able to solve complex policy problems considered intractable only a few years ago.

Addressing Gaps in Small-Scale Fisheries: A Low-Cost Tracking System.

During the last decade vessel-position-recording devices, such as the Vessel Monitoring System and the Automatic Identification System, have increasingly given accurate spatial and quantitative information of industrial fisheries. On the other hand, small-scale fisheries (vessels below 12 m) remain untracked and largely unregulated even though they play an important socio-economic and cultural role in European waters and coastal communities and account for most of the total EU fishing fleet. The typically low-technological capacity of these small-scale fishing boats-for which space and power onboard are often limited-as well their reduced operative range encourage the development of efficient, low-cost, and low-burden tracking solutions. In this context, we designed a cost-effective and scalable prototypic architecture to gather and process positional data from small-scale vessels, making use of a LoRaWAN/cellular network. Data collected by our first installation are presented, as well as its preliminary processing. The emergence of a such low-cost and open-source technology coupled to artificial intelligence could open new opportunities for equipping small-scale vessels, collecting their trajectory data, and estimating their fishing effort (information which has historically not been present). It enables a new monitoring strategy that could effectively include small-scale fleets and support the design of new policies oriented to inform coastal resource and fisheries management.

Using fisher-contributed secondary fins to fill critical shark-fisheries data gaps.

Developing-world shark fisheries are typically not assessed or actively managed for sustainability; one fundamental obstacle is the lack of species and size-composition catch data. We tested and implemented a new and potentially widely applicable approach for collecting these data: mandatory submission of low-value secondary fins (anal fins) from landed sharks by fishers and use of the fins to reconstruct catch species and size. Visual and low-cost genetic identification were used to determine species composition, and linear regression was applied to total length and anal fin base length for catch-size reconstruction. We tested the feasibility of this approach in Belize, first in a local proof-of-concept study and then scaling it up to the national level for the 2017-2018 shark-fishing season (1,786 fins analyzed). Sixteen species occurred in this fishery. The most common were the Caribbean reef (Carcharhinus perezi), blacktip (C. limbatus), sharpnose (Atlantic [Rhizoprionodon terraenovae] and Caribbean [R. porosus] considered as a group), and bonnethead (Sphyrna cf. tiburo). Sharpnose and bonnethead sharks were landed primarily above size at maturity, whereas Caribbean reef and blacktip sharks were primarily landed below size at maturity. Our approach proved effective in obtaining critical data for managing the shark fishery, and we suggest the tools developed as part of this program could be exported to other nations in this region and applied almost immediately if there were means to communicate with fishers and incentivize them to provide anal fins. Outside the tropical Western Atlantic, we recommend further investigation of the feasibility of sampling of secondary fins, including considerations of time, effort, and cost of species identification from these fins, what secondary fin type to use, and the means with which to communicate with fishers and incentivize participation. This program could be a model for collecting urgently needed data for developing-world shark fisheries globally. Article impact statement: Shark fins collected from fishers yield data critical to shark fisheries management in developing nations.

Uso de Aletas Secundarias Proporcionadas por Pescadores para Llenar Vacíos Importantes de Información sobre las Pesquerías de Tiburones Resumen Con frecuencia no se evalúan las pesquerías de tiburones del mundo en desarrollo ni cuentan con un manejo activo de sustentabilidad. Uno de los principales obstáculos para esto es la falta de información sobre las especies y la composición de los tamaños en las capturas. Probamos e implementamos una estrategia nueva y potencialmente aplicable en todas partes para la recolección de estos datos: la entrega obligatoria de las aletas secundarias de bajo valor económico (aletas anales) obtenidas de los tiburones desembarcados por parte de los pescadores y el uso de estas aletas para reconstruir las especies y tamaños en la captura. Usamos identificaciones genéticas de bajo costo e identificaciones visuales para determinar la composición de las especies y aplicamos una regresión lineal a la longitud total y a la de la base de la aleta anal para la reconstrucción del tamaño en captura. Probamos la viabilidad de esta estrategia en Belice, primero en un estudio de prueba de concepto y después subiendo al nivel nacional para la temporada de pesca de tiburón 2017-2018 (1,786 aletas analizadas). Se registraron 16 especies en esta pesquería. Las más comunes fueron Carcharhinus perezi, C. limbatus, Rhizoprionodon terraenovae y R. porosus (consideradas como un grupo) y Sphyrna cf. tiburo. Las últimas tres especies fueron desembarcadas principalmente por encima del tamaño maduro, mientras que con las dos primeras especies lo hacían por debajo del tamaño maduro. Nuestra estrategia demostró ser efectiva en la obtención de información crítica para el manejo de la pesquería de tiburones y sugerimos que las herramientas desarrolladas como parte de este programa puedan ser exportadas a otras naciones en esta región y aplicadas casi de manera inmediata si existen los medios para comunicarse con los pescadores e incentivarlos a proporcionar las aletas anales. Fuera del Atlántico Occidental tropical, recomendamos una mayor investigación de la viabilidad del muestreo de aletas secundarias, incluyendo la consideración del tiempo, esfuerzo y costo de la identificación de especies a partir de estas aletas; cuál tipo de aleta secundaria utilizar; y los medios mediante los cuales comunicarse con los pescadores e incentivarlos a participar. Este programa podría ser un modelo para la recolección de información de necesidad urgente para las pesquerías del mundo en desarrollo.

Fishery reforms for the management of non-indigenous species.

Marine ecosystems are undergoing major transformations due to the establishment and spread of Non-Indigenous Species (NIS). Some of these organisms have adverse effects, for example by reducing biodiversity and causing ecosystem shifts. Others have upsides, such as benefits to fisheries or replacing lost ecological functions and strengthening biogenic complexity. Stopping the spread of NIS is virtually impossible and so the societal challenge is how to limit the socioeconomic, health, and ecological risks, and sustainably exploit the benefits provided by these organisms. We propose a move away from the notion that NIS have only negative effects, and suggest a turn towards an Ecosystem-Based Fishery Management approach for NIS (EBFM-NIS) in the Mediterranean Sea, the world's most invaded marine region. A structured, iterative, and adaptive framework that considers the range of costs and benefits to ecosystems, ecosystem services, and fisheries is set out to determine whether NIS stocks should be managed using sustainable or unsustainable exploitation. We propose fishery reforms such as multiannual plans, annual catch limits, technical measures for sustainable exploitation, and legitimization of unlimited fishing of selected NIS and introduction of a radical new license for NIS fishing for unsustainable exploitation. Depending on local conditions, investment strategies can be included within the EBFM-NIS framework to protect/enhance natural assets to improve ecosystem resilience against NIS, as well as fishery assets to improve the performance of NIS fisheries. Examples of the former include the enhancement of Marine Protected Areas, harvesting of invasive NIS within MPAs, and protection of overfished predators and key species. Examples of the latter include market promotion and valorisation of NIS products, development of novel NIS products, and innovative/alternative NIS fishing such as fishery-related tourism ('pescatourism'). The application of the suggested EBFM-NIS would create jobs, protect and enhance ecosystem services, and help to meet the United Nations Sustainable Development Goal 14: Conserve and sustainably use the oceans, seas, and marine resources for sustainable development.

Copy number variants outperform SNPs to reveal genotype-temperature association in a marine species.

Copy number variants (CNVs) are a major component of genotypic and phenotypic variation in genomes. To date, our knowledge of genotypic variation and evolution has largely been acquired by means of single nucleotide polymorphism (SNPs) analyses. Until recently, the adaptive role of structural variants (SVs) and particularly that of CNVs has been overlooked in wild populations, partly due to their challenging identification. Here, we document the usefulness of Rapture, a derived reduced-representation shotgun sequencing approach, to detect and investigate copy number variants (CNVs) alongside SNPs in American lobster (Homarus americanus) populations. We conducted a comparative study to examine the potential role of SNPs and CNVs in local adaptation by sequencing 1,141 lobsters from 21 sampling sites within the southern Gulf of St. Lawrence, which experiences the highest yearly thermal variance of the Canadian marine coastal waters. Our results demonstrated that CNVs account for higher genetic differentiation than SNP markers. Contrary to SNPs, for which no significant genetic-environment association was found, 48 CNV candidates were significantly associated with the annual variance of sea surface temperature, leading to the genetic clustering of sampling locations despite their geographic separation. Altogether, we provide a strong empirical case that CNVs putatively contribute to local adaptation in marine species and unveil stronger spatial signal of population structure than SNPs. Our study provides the means to study CNVs in nonmodel species and highlights the importance of considering structural variants alongside SNPs to enhance our understanding of ecological and evolutionary processes shaping adaptive population structure.

Spatially explicit modeling of metapopulation dynamics of broadcast spawners and stabilizing/destabilizing effects of heterogeneity of quality across local habitats.

Many coastal invertebrate species are broadcast spawners. These species have a highly sedentary adult stage and disperse by oceanic transport of planktonic larvae. One commercially important group of broadcast spawners is abalones, which live in suitable habitat patches of rock reefs that are discretely distributed. Because of these life-history and habitat characteristics, abalones tend to exhibit a metapopulation structure. Despite fisheries management and the release of juveniles, wild populations of broadcast spawners have undergone dramatic reductions in density due to overexploitation, which has been partly attributed to a failure to account for spatial structure. To clarify the relationship between the persistence of a metapopulation and the bottleneck that occurs during reproduction and dispersal processes caused by spatial structure, we developed a spatially explicit metapopulation model accounting for the effects of both life history and fishery pressure. By analyzing the model, we derived a metric to evaluate metapopulation quality as the leading eigenvalue of a non-negative matrix (the landscape matrix). Using this measure, we clarified that the effect of spatial structure on metapopulation stability is explained well by the mean and variance of parameter values across patches under the condition in which the heterogeneity of the metapopulation network is weak. In particular, the presence of both a higher average and higher variance of quality in the landscape could indicate stable fishery stocks under certain conditions. For example, when the decline in the mean longevity of local patch due to the fishery pressures gradually diminishes, the rescue effects by good patches would work more effectively than the negative effect of bad patches and then the stabilizing effect of spatial heterogeneity could be observed in a metapopulation. Furthermore, optimal patch characteristics for the improvement of quality strongly depend on specific parameter values. For example, when adult fertility is improved, a patch with higher "source" ability is more suitable. In contrast, when the settlement success of planktonic larvae is improved or fishery pressure is reduced, a patch with higher "buffer" ability is more suitable for the improvement of fishery management.

Marine reserves solve an important bycatch problem in fisheries.

Management of the diverse fisheries of the world has had mixed success. While managing single species in data-rich environments has been largely effective, perhaps the greatest challenge facing fishery managers is how to deal with mixed stocks of fish with a range of life histories that reside in the same location. Because many fishing gears are nonselective, and the costs of making gear selective can be high, a particular problem is bycatch of weak stocks. This problem is most severe when the weak stock is long-lived and has low fecundity and thus requires a very long recovery time once overfished. We investigate the role that marine reserves might play in solving this challenging and ubiquitous problem in ecosystem-based management. Evidence for marine reserves' potential to manage fisheries in an ecosystem context has been mixed, so we develop a heuristic strategic mathematical model to obtain general conclusions about the merits of managing multispecies fisheries by using reserves relative to managing them with nonspatial approaches. We show that for many fisheries, yields of strong stocks can be increased, and persistence of weak stocks can be ensured, by using marine reserves rather than by using traditional nonspatial approaches alone. Thus, reserves have a distinct advantage as a management tool in many of the most critical multispecies settings. We also show how the West Coast groundfish fishery of the United States meets these conditions, suggesting that management by reserves may be a superior option in that case.

Automatic Bluefin Tuna Sizing with a Combined Acoustic and Optical Sensor.

A proposal is described for an underwater sensor combining an acoustic device with an optical one to automatically size juvenile bluefin tuna from a ventral perspective. Acoustic and optical information is acquired when the tuna are swimming freely and the fish cross our combined sensor's field of view. Image processing techniques are used to identify and classify fish traces in acoustic data (echogram), while the video frames are processed by fitting a deformable model of the fishes' ventral silhouette. Finally, the fish are sized combining the processed acoustic and optical data, once the correspondence between the two kinds of data is verified. The proposed system is able to automatically give accurate measurements of the tuna's Snout-Fork Length (SFL) and width. In comparison with our previously validated automatic sizing procedure with stereoscopic vision, this proposal improves the samples per hour of computing time by 7.2 times in a tank with 77 juveniles of Atlantic bluefin tuna (Thunnus thynnus), without compromising the accuracy of the measurements. This work validates the procedure for combining acoustic and optical data for fish sizing and is the first step towards an embedded sensor, whose electronics and processing capabilities should be optimized to be autonomous in terms of the power supply and to enable real-time processing.

Identification of a nursery area for the critically endangered hammerhead shark (Sphyrna lewini) amid intense fisheries in the southern Gulf of Mexico.

Since the 1980s, there has been growing concern in the Mexican Atlantic regarding high catches of neonate and juvenile sharks in small-scale fisheries. Fishery-dependent data from 1993 to 1994 and 2007 to 2017 and fishers' ecological knowledge from 2017 were used to identify nursery areas for scalloped hammerhead, Sphyrna lewini, in the southern Gulf of Mexico. Catch records and fishing areas of neonates, YOYs, juveniles and adults of S. lewini (N = 1885) were obtained from calcareous and terrigenous regions in the western Yucatan Peninsula. The results suggest that a nursery for scalloped hammerhead is found in the terrigenous region, characterized by relatively shallow and turbid waters due to rivers' discharges. Neonates and YOYs (96% and 86% of their total records, respectively) were commonly found there over the years in May-August in multiple fishing areas identified by fishers, although mainly between isobaths 10-30 m. The enforcement of management measures is necessary because the nursery is located in a region with intense fishing effort.

Comparative age-specific demography of four commercially important deep-water snappers: implication for fishery management of a long-lived lutjanid.

Lutjanid snappers belonging to the subfamilies Apsilinae and Etelinae are commercially valuable components of tropical deep-water fisheries throughout much of the Indo-Pacific region. Based on age assessment using sagittal otoliths, the age-specific demographic characteristics of four deep-water snappers, Etelis coruscans, Paracaesio caerulea, Pristipomoides filamentosus and Pristipomoides sieboldii, in the Okinawa Islands, southwestern Japan, were examined, and the results were discussed for fishery management. Age validation using edge-type analysis demonstrated that opaque zones in all species were formed once per year and were considered valid annual growth increments. The von Bertalanffy growth equations were also determined for each species. These snappers are long-lived (>50 years for E. coruscans and P. caerulea and >30 years for the two species of Pristipomoides) and relatively slow-growing. The age of acquiring sexual maturity in females was relatively later in E. coruscans, P. caerulea and P. filamentosus than in P. sieboldii. The results revealed differences in the biological traits among these four species; E. coruscans and P. caerulea with long life spans and late maturation are particularly more vulnerable to fishing impact than the two Pristipomoides species. Therefore, further approaches to decrease and control fishing intensity, such as networking of marine-protected areas and regulation to control the numbers of boats and/or the total allowable catch, are necessary for the management of the stock of these species, especially for E. coruscans and P. caerulea.

Missing link: California rock crabs serve as intermediate hosts for the parasite Helicometrina nimia.

Parasites can have strong effects on invertebrate host behaviour, fecundity and survival in marine ecosystems. However, parasites are often poorly documented and still rarely integrated into marine ecological modelling; comprehensive surveys of infection in marine invertebrates are sporadic at best. For example, rock crabs are an important part of Californian coastal ecosystems, both as regulators of mussel populations and non-native species, and as prey items for predators like sea otters, but their parasite communities and potential effects on crab population dynamics are seldom studied or understood. Here, we present the first report of infection by the trematode Helicometrina nimia in the economically and ecologically important red rock crab (Cancer productus) and Pacific rock crab (Romaleon antennarium). As intermediate hosts, they are a missing link for infection by H. nimia in Californian fish that was unreported until now. Based on these findings, we advocate for further research into parasite diversity and their potential effects on ecologically and commercially important species.

Catastrophic Mortality, Allee Effects, and Marine Protected Areas.

For many species, reproductive failure may occur if abundance drops below critical Allee thresholds for successful breeding, in some cases impeding recovery. At the same time, extreme environmental events can cause catastrophic collapse in otherwise healthy populations. Understanding what natural processes and management strategies may allow for persistence and recovery of natural populations is critical in the face of expected climate change scenarios of increased environmental variability. Using a spatially explicit continuous-size fishery model with stochastic dispersal parameterized for abalone-a harvested species with sedentary adults and a dispersing larval phase-we investigated whether the establishment of a system of marine protected areas (MPAs) can prevent population collapse, compared with nonspatial management when populations are affected by mass mortality from environmental shocks and subject to Allee effects. We found that MPA networks dramatically reduced the risk of collapse following catastrophic events (75%-90% mortality), while populations often continued to decline in the absence of spatial protection. Similar resilience could be achieved by closing the fishery immediately following mass mortalities but would necessitate long periods without catch and therefore economic income. For species with Allee effects, the use of protected areas can ensure persistence following mass mortality events while maintaining ecosystem services during the recovery period.

A management case study for a new commercial fishery: brine shrimp harvesting in Great Salt Lake, Utah, USA.

A fishery for brine shrimp (Artemia franciscana) cysts to supply the aquaculture industry considerably expanded in the late 1980s in the Great Salt Lake, Utah, USA. With this expansion, concerns emerged in the 1990s about the fishery's sustainability, especially its impact on the abundant western North American waterbirds that use the lake and feed on brine shrimp. We track the development of management strategies using adaptive management by the Utah Division of Wildlife Resources (UDWR), which focused on the biology of the system and development of biology-based harvesting models. The models and their rationale are presented, their success in forecasting is evaluated, and implications for managing the harvest and conserving waterbirds are examined. We view this as an interesting case study because it transpired over a short time in a relatively simple system. This permitted us to clearly track management from the onset of a harvest market, through realization that the harvest had to be managed in the absence of needed biological knowledge, to the adaptive development of management strategies as biological knowledge was accumulated. The outcome illustrates the success that harvest management can attain with careful monitoring of the resource and terminating the harvest when a necessary escapement stock is attained.

Global fishery prospects under contrasting management regimes.

Data from 4,713 fisheries worldwide, representing 78% of global reported fish catch, are analyzed to estimate the status, trends, and benefits of alternative approaches to recovering depleted fisheries. For each fishery, we estimate current biological status and forecast the impacts of contrasting management regimes on catch, profit, and biomass of fish in the sea. We estimate unique recovery targets and trajectories for each fishery, calculate the year-by-year effects of alternative recovery approaches, and model how alternative institutional reforms affect recovery outcomes. Current status is highly heterogeneous-the median fishery is in poor health (overfished, with further overfishing occurring), although 32% of fisheries are in good biological, although not necessarily economic, condition. Our business-as-usual scenario projects further divergence and continued collapse for many of the world's fisheries. Applying sound management reforms to global fisheries in our dataset could generate annual increases exceeding 16 million metric tons (MMT) in catch, $53 billion in profit, and 619 MMT in biomass relative to business as usual. We also find that, with appropriate reforms, recovery can happen quickly, with the median fishery taking under 10 y to reach recovery targets. Our results show that commonsense reforms to fishery management would dramatically improve overall fish abundance while increasing food security and profits.

The right incentives enable ocean sustainability successes and provide hope for the future.

Healthy ocean ecosystems are needed to sustain people and livelihoods and to achieve the United Nations Sustainable Development Goals. Using the ocean sustainably requires overcoming many formidable challenges: overfishing, climate change, ocean acidification, and pollution. Despite gloomy forecasts, there is reason for hope. New tools, practices, and partnerships are beginning to transform local fisheries, biodiversity conservation, and marine spatial planning. The challenge is to bring them to a global scale. We dissect recent successes using a complex adaptive-systems (CAS) framework, which acknowledges the interconnectedness of social and ecological systems. Understanding how policies and practices change the feedbacks in CASs by altering the behavior of different system components is critical for building robust, sustainable states with favorable emergent properties. Our review reveals that altering incentives-either economic or social norms, or both-can achieve positive outcomes. For example, introduction of well-designed rights-based or secure-access fisheries and ecosystem service accounting shifts economic incentives to align conservation and economic benefits. Modifying social norms can create conditions that incentivize a company, country, or individual to fish sustainably, curb illegal fishing, or create large marine reserves as steps to enhance reputation or self-image. In each example, the feedbacks between individual actors and emergent system properties were altered, triggering a transition from a vicious to a virtuous cycle. We suggest that evaluating conservation tools by their ability to align incentives of actors with broader goals of sustainability is an underused approach that can provide a pathway toward scaling sustainability successes. In short, getting incentives right matters.

Genomics and telemetry suggest a role for migration harshness in determining overwintering habitat choice, but not gene flow, in anadromous Arctic Char.

Migration is a ubiquitous life history trait with profound evolutionary and ecological consequences. Recent developments in telemetry and genomics, when combined, can bring significant insights on the migratory ecology of nonmodel organisms in the wild. Here, we used this integrative approach to document dispersal, gene flow and potential for local adaptation in anadromous Arctic Char from six rivers in the Canadian Arctic. Acoustic telemetry data from 124 tracked individuals indicated asymmetric dispersal, with a large proportion of fish (72%) tagged in three different rivers migrating up the same short river in the fall. Population genomics data from 6,136 SNP markers revealed weak, albeit significant, population differentiation (average pairwise FST  = 0.011) and asymmetric dispersal was also revealed by population assignments. Approximate Bayesian computation simulations suggested the presence of asymmetric gene flow, although in the opposite direction to that observed from the telemetry data, suggesting that dispersal does not necessarily lead to gene flow. These observations suggested that Arctic Char home to their natal river to spawn, but may overwinter in rivers with the shortest migratory route to minimize the costs of migration in nonbreeding years. Genome scans and genetic-environment associations identified 90 outlier markers putatively under selection, 23 of which were in or near a gene. Of these, at least four were involved in muscle and cardiac function, consistent with the hypothesis that migratory harshness could drive local adaptation. Our study illustrates the power of integrating genomics and telemetry to study migrations in nonmodel organisms in logistically challenging environments such as the Arctic.