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Increasing social risk and markets demand lead to a more selective fishing across the Pantanal wetland
Abstract and Figures
Fishing connects people, aquatic systems, places, and fish consumer markets all around the world. Our understanding of the magnitude and intensity of these interactions are comparatively scarce for some regions, and to date have mostly yielded insights to understand socioecological linkages within marine fisheries. Here, we investigated how socio-demographic and economic factors are associated with fishing selectivity in the Brazilian Pantanal wetland using data from the continental commercial fishing sector from 18 fisher colonies. Our results show that increasing unemployment can lead to a more specialized or selective fishery. In addition, the watersheds where more selective fishing is practiced were those whose colonies are closer to the state capitals that make up the Upper Paraguay River Basin. The general results support that Pantanal wetland fishers do not follow the global pattern of fisheries in regions with low development, which tends to behave more as generalists than specialists. On the other hand, we provide evidence that specialized fishing selectivity is associated with external market demand in a socioeconomic coupling. We emphasize the importance of socioeconomic policies to reduce social vulnerability of fishers, and of management strategies to maintain fish stocks in wetlands.
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... Indigenous Peoples and Local Communities (IPLCs) of the Pantanal are mostly classified as commercial fishers, although they shift between commercial, subsistence and bait gathering depending on demand, opportunity and available tools (Chiaravalloti, 2019). Artisanal fishers are usually linked to fishers' associations, locally called 'Colonia de Pescadores', which help them gather the documentation to access the closed fishing season benefits ( Figure 1; Nunes et al., 2023). ...
A new policy in the Pantanal wetland, Brazil, aims to economically displace thousandsof artisanal fishers from one-third of the region. The legislation disregards severalFAO Voluntary Guidelines for Securing Sustainability in Small- Scale Fisheries' guidingprinciples (SSF guidelines). Considering that 2024 marks the 10th anniversary of theseguidelines, this policy represents a significant setback for fish and fisheries worldwide.In this paper, we show that the legislation is part of long-term agenda against small-scale fishers in the Pantanal, aiming to use narratives around overfishing to justifyphysical and economic displacements—albeit no empirical evidence showing impacton fish stocks. We also show that, as in many other small-scale fisheries worldwide,overfishing narratives are, in fact, used to open space for industrial activities and largeinfrastructure projects. The Pantanal is a telling story of that, since the new legislationwill likely open space for the construction of over 50 small hydroelectric dams in thePantanal and surrounding area. We argue that, first, it is urgent to abolish the newlegislation and promote a pro-fishers agenda in the Pantanal to protect the region.However, since this is not unique for the region, it is critical to implement internationalprogrammes that celebrate and support local fisheries worlwide and avoid physicaland economic displacements. Stands out turning SSF guidelines into internationalagreements, implementing citizens science programmes and expanding the fisher'stenure rights through innovative mechanizes of ownership. By better protecting localsmall-scale fishers in the Pantanal and worldwide we are more likely to guarantee asustainable future for ecosystems and its peoples.
Sub-Saharan Africa’s freshwater fisheries contribute significantly to the livelihoods and food security of millions of people within the region. However, freshwater fisheries are experiencing multiple anthropogenic stressors such as overfishing, illegal fishing, pollution, and climate change. There is a substantial body of literature on the effects of climate change on freshwater fisheries in Sub-Saharan Africa. This study reviews the existing literature and highlights the effects of climate change on freshwater fisheries, the adaptation strategies of fishery-dependent households in response to the effects, and fisheries’ management and mitigation efforts in the face of climate change. The general effects of climate change on freshwater environments include warming water temperatures, increased stratification, modified hydrological processes, and increased pollutants. These effects adversely affect the physiological processes of fish and the overall wellbeing of fishery-dependent people. To cope with the effects of fluctuating fishery resources due to climate change, fishery-dependent people have adopted several adaptation strategies including livelihood diversification, changing their fishing gear, increasing their fishing efforts, and targeting new species. Several management attempts have been made to enhance the sustainability of fishery resources, from local to regional levels. This study recommends the participation of the resource users in the formulation of policies aimed at promoting climate change adaptation and the resilience of freshwater fisheries for sustainable development.
Despite Amazonia possessing the highest freshwater biodiversity on Earth, urban landing data show how huge fishing pressure is placed on only a dozen species. However, truly characterising the fishery and understanding the drivers of species selectivity is challenging, given the neglect of artisanal fishing activity, who may catch most of the Amazon’s fish. We register the catch of 824 fishing trips by interviewing artisanal fishers in their rural riverside communities. We use these data to characterise the artisanal fishery of the Rio Purus, the main fish source sub-system for the Amazon’s largest city (Manaus), and investigate the factors determining catch composition. Fishers caught 80 fish species, yet just four species made up over half of the harvested biomass. Urban markets appear to drive greater selectivity, with a significantly lower species diversity in commercial compared to subsistence catches. Fish catch composition varied significantly both seasonally and with geographical remoteness from Manaus. The spatial turnover in catch composition appears to be driven by urban access, with more commercially important species dominating where Manaus-based fish-buyers frequent. Our data may partially explain observed overfishing in some commercially important species, particularly as most Amazonians now live in urban areas.
In attempting to predict the impact of major ecological or climatic change on livelihoods, insights can be gained by looking at communities who experience extreme seasonal or annual variation. Here, we compare the ecology, economy, and social network of a community of traditional fishers in the Brazilian Pantanal between the dry season and the flood season in which their wetland ecosystem is transformed. Using data derived from satellite imaging we show that during the flood season of 2019 the total amount of open water accessible to fishers more than doubled and led to drastic qualitative changes. We show that although fishers adapted to this extreme seasonality by changing where, how, and what they fish between seasons, the structure of the social network in our study community did not differ. We argue that strong networks are especially important in social-ecological systems with extreme seasonal changes. More generally, we suggest that case studies of seasonal adaptation such as ours can contribute to a broader understanding of how communities may be able to successfully adapt to novel social-ecological changes.
Macrosystems are integrated human–natural systems, in recognition of the fact that virtually every natural system on Earth influences and is influenced by human activities, even over long distances. It is therefore crucial to incorporate inherent properties of broad‐scale systems, such as human–nature connectivity and feedbacks at multi‐scales, into macrosystems biology studies. Here, we propose the “metacoupling” framework as a macrosystems biology approach. This framework incorporates the study of ecological and socioeconomic dimensions and their interactions within, between, and among adjacent and distant locations. We present examples highlighting that (1) human activities are increasing multi‐scale interactions; (2) the increase in frequency and intensity of distant interactions reduces the importance of proximity as a dominant factor connecting systems; and (3) metacoupling generates both ecological and socioeconomic feedbacks, with profound impacts. The metacoupling framework discussed here can advance macrosystems biology, create opportunities for innovative scientific discoveries, and address global challenges.
Building bridges between environmental and political agendas is essential nowadays in face of the increasing human pressure
on natural environments, including wetlands. Wetlands provide critical ecosystem services for humanity and can generate a
considerable direct or indirect income to the local communities. To meet many of the sustainable development goals, we
need to move our trajectory from the current environmental destructive development to a wiser wetland use. The current
article contain a proposed agenda for the Pantanal aiming the improvement of public policy for conservation in the Pantanal,
one of the largest, most diverse, and continuous inland wetland in the world. We suggest and discuss a list of 11 essential
interfaces between science, policy, and development in region linked to the proposed agenda. We believe that a functional
science network can booster the collaborative capability to generate creative ideas and solutions to address the big
challenges faced by the Pantanal wetland
Human health and livelihoods are threatened by declining marine fisheries catches, causing substantial interest in the sources and dynamics of fishing. Catch analyses in individual exclusive economic zones (EEZs) and the high seas are abundant, and research across multiple EEZs is growing. However, no previous studies have systematically compared catches, intranational versus international fish flows, and fishing nations within all of the world’s EEZs and across adjacent and distant EEZs and the high seas to inform “metacoupled” fisheries management. We use the metacoupling framework—a new approach for evaluating human–nature interactions within and across adjacent and distant systems (metacouplings)—to illustrate how fisheries catches were locally, regionally, and globally interconnected in 1950–2014, totaling 5.8 billion metric tons and increasing by 298% (tonnage) and 431% (monetary value) over this time period. Catches by nations in their own EEZs (largest in Peru) and adjacent EEZs (largest in Indonesia) constituted 86% of worldwide catches, growing in 1950–1996 but declining in 1997–2014. In contrast, catches in distant EEZs and the high seas—largest in Morocco, Mauritania, and Canada—peaked in 1973 and have since represented 9–21% of annual catches. Our 65-year, local–regional–global analysis illustrates how metacoupled fisheries governance—holistic management of multiscalar catches, flows, and tradeoffs within and among fisheries—can improve food and nutrition security, livelihood resilience, and biodiversity conservation across the world.
Resilience thinking has generated much interest among scientific communities, yet most resilience concepts have not materialized into management applications. We believe that using resilience concepts to characterize systems and the social and ecological processes affecting them is a way to integrate resilience into better management decisions. This situation is exemplified by inland recreational fisheries, which represent complex socioecological systems that face unpredictable and unavoidable change. Making management decisions in the context of resilience is increasingly important given mounting environmental and anthropogenic perturbations to inland systems. Herein, we propose a framework that allows resilience concepts to be better incorporated into management by (i) recognizing how current constraints and management objectives focus on desired or undesired systems (specific fish and anglers), (ii) evaluating the state of a system in terms of how both social and ecological forces enforce or erode the desired or undesired system, (iii) identifying the resilience-stage cycles a system state may undergo, and (iv) determining the broad management strategies that may be viable given the system state and resilience stage. We use examples from inland recreational fisheries to illustrate different system state and resilience stages and synthesize several key results. Across all combinations of socioecological forces, five common types of viable management strategies emerge: (i) adopt a different management preference or focus, (ii) change stakeholder attitudes or behaviors via stakeholder outreach, (iii) engage in (sometimes extreme) biological intervention, (iv) engage in fishery intervention, and (v) adopt landscape-level management approaches focusing on achieving different systems in different waters. We then discuss the challenges and weaknesses of our approach, including specifically the cases in which there are multiple strong social forces (i.e., stakeholders holding competing objectives or values) and situations where waters are not readily divisible, such as rivers or great lakes, and in which spatial separation of competing objectives will be difficult. We end with our vision of how we believe these types of operationalized resilience approaches could improve or transform inland recreational fisheries management.
Modeling scenarios can help identify drivers of and potential changes in land use, particularly in rapidly changing landscapes such as the tropics. One of the places where most of the recent anthropogenic land use changes have been occurring is the "arc of deforestation" of the Amazon, where several scenarios have been constructed. Such modeling scenarios, however, have been implemented less frequently in wetland areas, but these are also undergoing rapid change. An example is the Pantanal, one of the largest wetlands on the planet located in the Upper Paraguay River Basin (UPRB). The UPRB is formed by the lowland (Pantanal) and the plateau (Cerrado and Amazon where the spring-fed rivers are). We used a spatially explicit model to identify drivers of vegetation loss in the Pantanal and surrounding area (UPRB) and estimated potential vegetation loss for the next 30 years. The model is probabilistic and considers that vegetation loss is contagious, so that the local rate of deforestation increases over time if adjacent sites are deforested, also taking into account the drivers identified in those locations. Our study is the first to simulate vegetation loss at property-scale, over 20,000 properties, for the entire UPRB in Brazil, taking into account the relationship between the plateau, where headwaters are located, and the lowland, where flooded-areas are concentrated. The drivers of vegetation loss identified for the lowland (distance to roads and rivers and elevation) differed from those for the plateau (distance to cities), demonstrating the relevance of analyzing areas separately. The cumulative rate of native vegetation loss projected for 2050 was 3% for the lowland and 10% for the plateau, representing losses of 6045 km 2 and of native vegetation area decreasing from 87% to 83% and 7960 km 2 from 39% to 35% respectively by 2050, if changes continue at the same pace and if the environmental legislation is followed. The projected vegetation loss in the UPRB forms a geographical arc, very similar to that observed in the Amazon, from the plateau into the lowland. The arc is directly related to areas with no or low flooding frequency because they are suitable for agriculture. The identification of this arc of vegetation loss calls for urgent conservation policies for this wetland and new perspectives for management.
Dam construction comes with severe social, economic and ecological impacts. From an ecological point of view, habitat types are altered and biodiversity is lost. Thus, to identify areas that deserve major attention for conservation, existing and planned locations for (hydropower) dams were overlapped, at global extent, with the contemporary distribution of freshwater megafauna species with consideration of their respective threat status. Hydropower development will disproportionately impact areas of high freshwater megafauna richness in South America, South and East Asia, and the Balkan region. Sub-catchments with a high share of threatened species are considered to be most vulnerable; these are located in Central America, Southeast Asia and in the regions of the Black and Caspian Sea. Based on this approach, planned dam locations are classified according to their potential impact on freshwater megafauna species at different spatial scales, attention to potential conflicts between climate mitigation and biodiversity conservation are highlighted, and priorities for freshwater management are recommended.
The loss of biodiversity, including the collapse of fish stocks, affects the vulnerability of social-ecological systems (SESs)and threatens local livelihoods. Incorporating community-centered indicators and SES drivers and exposures of change into coastalmanagement can help anticipate and mitigate human and/or coastal vulnerability. We have proposed a new index to measure the social-ecological vulnerability of coastal fishing communities (Index of Coastal Vulnerability [ICV]) based on species, ecosystem, and socialindicators. The ICV varies from 0 (no vulnerability) to 1 (very high vulnerability) and is composed of 3 components: species vulnerability,i.e., fish biological traits; ecosystem vulnerability, i.e., environmental indicators of ecosystem health; and adaptive capacity, i.e., humanability to cope with changes. We tested the ICV of Brazil’s 17 coastal states. The average ICV for the Brazilian coast was 0.77, andvariation was low among states. More than half of the coastal states revealed very high vulnerability (> 0.8). The ecosystem vulnerabilityvalues were worse than the adaptive capacity and species vulnerability values, and the North and Northeast regions were revealed tobe vulnerable hot spots. Additionally, we investigated how the ICV related to specific anthropogenic risks, i.e., fish landing richness,fishery instability, market, coastal extension, and coastal population, and found that states with fewer species landings and highercoastal populations presented higher ICVs. At a time when human impacts are overtaking natural processes, understanding how theseimpacts lead to coastal vulnerability can help improve conservation policies. For this case study, we suggest both fisheries managementmeasures and restoration of sensitive habitats to protect species and decrease vulnerability. The integrated evaluation developed here could be used as a baseline for coastal monitoring and conservation planning and be applied to coastal regions in which governments evaluate both social and biological aspects
Building bridges between environmental and political agendas is
essential nowadays in face of the increasing human pressure on natural
environments, including wetlands. Wetlands provide critical ecosystem
services for humanity, and can generate a considerable direct or indirect
income to the local communities. In order to meet many of the
sustainable development goals, we need to move our trajectory from the
current environmental destructive development to a wiser wetland use.
The current paper contain a proposed agenda for the Pantanal aiming
the improvement of public policy for conservation in the Pantanal, one of
the largest, most diverse, and continuous inland wetland in the world.
We suggest and discuss a list of 10 essential interfaces between science,
policy, and development in region linked to the proposed agenda. We
believe that a functional science network can booster the collaborative
capability to generate creative ideas and solutions to address the big
challenges faced by the Pantanal wetland.
Balanced harvest has been proposed to reduce fishing impact on ecosystems while simultaneously maintaining or even increasing fishery yield. The concept has attracted broad interest, but also received criticisms. In this paper, we examine the theory, modelling studies, empirical evidence, the legal and policy frameworks, and management implications of balanced harvest. The examination reveals unresolved issues and challenges from both scientific and management perspectives. We summarize current knowledge and address common questions relevant to the idea. Major conclusions include: balanced harvest can be expressed in several ways and implemented on multiple levels, and with different approaches e.g. métier based management; it explicitly bridges fisheries and conservation goals in accordance with international legal and policy frameworks; modelling studies and limited empirical evidence reveal that balanced harvest can reduce fishing impact on ecosystem structure and increase the aggregate yield; the extent of balanced harvest is not purely a scientific question, but also a legal and social choice; a transition to balanced harvest may incur short-term economic costs, while in the long-term, economic results will vary across individual fisheries and for society overall; for its application, balanced harvest can be adopted at both strategic and tactical levels and need not be a full implementation, but could aim for a “partially-balanced” harvest. Further objective discussions and research on this subject are needed to move balanced harvest toward supporting a practical ecosystem approach to fisheries.
Technology, transportation and global appetites have transformed trade relationships between near and distant countries. The impact of distant food demand on local agricultural production and trade has attracted considerable scientific scrutiny, yet little is known about how distant trade affects trade relationships and production between adjacent countries. In this paper, we explore this important issue by examining international food trade and agriculture production, which represent how distant places are connected through trade networks. By analyzing patterns of soybean, corn and wheat trading between 1991–2016 under the framework of metacoupling (human-nature interactions within, as well as between adjacent and distant systems), this study provides new insights into the spatio-temporal dynamics of trade flows. Results reveal that telecoupled (between distant countries) trade interacts with the geo-political landscape to enhance or offset intracoupled (within country) production and pericoupled (between neighboring countries) trade. Evidence from the literature and the results of autoregressive integrated moving average models indicate that when restrictions are placed on distant export routes, pericoupled trade increased. The extent to which the telecoupled food trade affected the pericoupled trade and intracoupled processes holds implications for the true extent of production driven by distant demands.
There is a widely acknowledged need to explicitly include humans in our conceptual and mathematical models of food webs. However, a simple and generalized method for incorporating humans into fisheries food webs has yet to be established. We developed a simple graphical framework for defining whole‐system inland fishery food webs that includes a continuum of fishery behaviors. This range of behaviors mimics those of generalist to specialist predators, which differentially influence ecosystem diversity, sustainability, and functioning. Fishery behaviors in this food‐web context are predicted to produce a range of “fishery types” – from targeted (ie specialist) to multispecies (ie generalist) inland fisheries – and relate to the socioeconomic status of fishery participants. Fishery participants in countries with low Human Development Index (HDI) values are highly connected through fisheries food webs relative to humans in more developed countries. Our framework shows that fisheries can occupy a variety of roles within a food‐web model and may thereby affect food‐web stability in different ways. This realization could help to improve sustainable fisheries management at a global scale.
Coastal communities are some of the most at-risk populations with respect to climate change impacts. It is therefore important to determine the vulnerability of such communities to co-develop viable adaptation options. Global efforts to address this issue include international scientific projects, such as Global Learning for Local Solutions (GULLS), which focuses on five fast warming regions of the southern hemisphere and aims to provide an understanding of the local scale processes influencing community vulnerability that can then be up-scaled to regional, country and global levels. This paper describes the development of a new social and ecological vulnerability framework which integrates exposure, sensitivity and adaptive capacity with the social livelihoods and food security approaches. It also measures community flexibility to understand better the adaptive capacity of different levels of community organization. The translation of the conceptual framework to an implementable method is described and its application in a number of “hotspot” countries, where ocean waters are warming faster than the rest of the world, is presented. Opportunities for cross-cultural comparisons to uncover similarities and differences in vulnerability and adaptation patterns among the study’s coastal communities, which can provide accelerated learning mechanisms to other coastal regions, are highlighted. The social and ecological framework and the associated survey approach allow for future integration of local-level vulnerability data with ecological and oceanographic models.
Fisheries are coupled human and natural systems (CHANS) across distant places, yet fisheries research has generally focused on better understanding either fisheries ecology or human dimensions in a specific place, rather than their interactions over distances. As economic and ideational globalization accelerate, fisheries are becoming more globally connected via movements of fish products and fisheries finances, information, and stakeholders throughout the world. As such, there is a pressing need for systematic approaches to assess these linkages among global fisheries, their effects on ecosystems and food security, and their implications for fisheries science and sustainability. Use of the telecoupling framework is a novel and insightful method to systematically evaluate socioeconomic and environmental interactions among CHANS. Here, we apply the telecoupling framework to the Peruvian anchoveta (Engraulis ringens) fishery, the world’s largest single-species commercial fishery and a complex CHANS. The anchoveta fishery has diverse and significant telecouplings – socioeconomic and environmental interactions over distances – with the rest of the world, including fishmeal and fish oil trade, monetary flow, knowledge transfer, and movement of people. The use of the telecoupling framework reveals complex fishery dynamics such as feedbacks (e.g., profit maximization causing fishery overcapitalization) and surprises (e.g., stock collapse) resulting from local and long-distance ecological and socioeconomic interactions. The Peruvian anchoveta fishery illustrates how the telecoupling framework can be used to systematically assess the magnitude and diversity of local and distant fisheries interactions and thereby advance knowledge derived from traditional monothematic research approaches. Insights from the telecoupling framework provide a foundation from which to develop sustainable fisheries policy and management strategies across local, national, and international levels in a globalized world.
Human-nature interactions are complex and have important implications for achieving sustainable development goals and addressing other global challenges. Although numerous studies have explored human-nature (or human-environment) interactions and generated useful insights, they are largely disintegrated. Because conceptual frameworks are the foundation of quantitative and qualitative integration, many have been proposed but focus mainly on human-nature interactions within a specific system. To reflect human-nature interactions between distant coupled systems, the framework of telecoupling (socioeconomic and environmental interactions over distances) has been developed. However, no framework has explicitly integrated human-nature interactions between adjacent coupled systems, let alone within a coupled system as well as between adjacent and distant coupled systems simultaneously. To fill such an important gap, in this paper I present an integrated framework of metacoupling: human-nature interactions within a system (intracoupling), between distant systems (telecoupling), and between adjacent systems (pericoupling). A metacoupled system is a set of two or more coupled systems that interact internally as well as nearby and far away, facilitated by agents affected by various causes with various effects. By differentiating and integrating intracoupling, pericoupling, and telecoupling, the metacoupling framework advances a systems perspective on global sustainability and human well-being. The framework can help uncover hidden systemic connections such as spillovers and feedbacks that may not be apparent when focusing on a particular system. To demonstrate the utility of the metacoupling framework, I illustrate its application to human-nature interactions within a global flagship nature reserve as well as between the reserve and the rest of the world. The illustration suggests that the framework has the potential to help holistically understand and integrate human-nature interactions from local to global scales, over time, and among organizational levels. Finally, I offer suggestions for operationalizing the metacoupling framework and discuss the need for new policy, governance, and management for a sustainable future across the metacoupled world.
Mapping the spatial allocation of fishing effort while including key stakeholders in the decision making process is essential for effective fisheries management but is difficult to implement in complex small-scale fisheries that are diffuse, informal and multifaceted. Here we present a standardized but flexible approach that combines participatory mapping approaches (fishers’ spatial preference for fishing grounds, or fishing suitability) with socioeconomic approaches (spatial extrapolation of social surrogates, or fishing capacity) to generate a comprehensive map of predicted fishing effort. Using a real world case study, in Moorea, French Polynesia, we showed that high predicted fishing effort is not simply located in front of, or close to, main fishing villages with high dependence on marine resources; it also occurs where resource dependency is moderate and generally in near-shore areas and reef passages. The integrated approach we developed can contribute to addressing the recurrent lack of fishing effort spatial data through key stakeholders' (i.e., resource users) participation. It can be tailored to a wide range of social, ecological and data availability contexts, and should help improve place-based management of natural resources.
Following a precise evaluation protocol that was applied to a pool of 202 articles published between 2003 and 2014, this paper evaluates the existing evidence of how and to what extent capture fisheries and aquaculture contribute to improving nutrition, food security, and economic growth in developing and emergent countries. In doing so we evaluate the quality and scientific rigor of that evidence, identify the key conclusions that emerge from the literature, and assess whether these conclusions are consistent across the sources. The results of the assessment show that while some specific topics are consistently and rigorously documented, thus substantiating some of the claims found in the literature, other areas of research still lack the level of disaggregated data or an appropriate methodology to reach consistency and robust conclusions. More specifically, the analysis reveals that while fish contributes undeniably to nutrition and food security, the links between fisheries/aquaculture and poverty alleviation are complex and still unclear. In particular national and household level studies on fisheries’ contributions to poverty alleviation lack good conceptual models and produce inconsistent results. For aquaculture, national and household studies tend to focus on export value chains and use diverse approaches. They suggest some degree of poverty alleviation and possibly other positive outcomes for adopters, but these outcomes also depend on the small-scale farming contexts and on whether adoption was emergent or due to development assistance interventions. Impacts of fish trade on food security and poverty alleviation are ambiguous and confounded by a focus on international trade and a lack of consistent methods. The influences of major drivers (decentralization, climate change, demographic transition) are still insufficiently documented and therefore poorly understood. Finally the evaluation reveals that evidence-based research and policy narratives are often disconnected, with some of the strongest and long-lasting policy narratives lacking any strong and rigorous evidence-based validation. Building on these different results, this paper identifies six key gaps facing policy-makers, development practitioners, and researchers.
A global assessment of fishing patterns and fishing pressure from 110 different Ecopath models, representing marine ecosystems
throughout the world and covering the period 1970–2007, show that human exploitation across trophic levels (TLs) is highly unbalanced and skewed towards low productive species at high TLs, which are around two TLs higher than the animal protein we get from terrestrial farming. Overall, exploitation levels from low trophic species were
<15% of production, and only 18% of the total number of exploited groups and species were harvested >40% of their production.
Generally, well-managed fisheries from temperate ecosystems were more selectively harvested at higher exploitation rates than
tropical and upwelling (tropical and temperate) fisheries, resulting in potentially larger long-term changes to the ecosystem
structure and functioning. The results indicate a very inefficient utilization of the food energy value of marine production.
Rebuilding overfished components of the ecosystem and changing focus to balancing exploitation across a wider range of TLs, i.e. balanced harvesting, has the potential to significantly increase overall catches from global marine fisheries.
Here, we introduce a novel theory for multispecies fisheries that exploit fish stocks evenly within and across trophic levels in an entire ecosystem (i.e., fishery comprises all fleets). These “indiscriminate” fisheries may be common in developing countries where fish provide the main source of dietary protein. We show that simple food web modules, motivated by empirical patterns in body size and energy flow, yield general and robust predictions about the fate of such a fishery. Specifically, high and uniform fishing mortality modifies the fish community in a manner that leads to increased productive capacity from a low-diversity assemblage of small-bodied fish with rapid population growth and turnover (the productive monoculture effect). We then argue that catches are relatively indiscriminate in the Tonlé Sap, a highly productive inland fishery in Cambodia that feeds millions, and show consistent qualitative agreement between the theory of indiscriminate fishing and this existing empirical data. As the theory suggests, this indiscriminate fishery appears to be remarkably productive at the community level in the face of high fishing mortality; however, it tends to be unsustainable at the species level as the Tonlé Sap has a much depleted species diversity under its current high fishing mortality. We end by arguing that the reduced diversity of these types of fisheries likely put them at severe risk of being heavily impacted by changing environmental conditions such as climate change and hydroelectric development.
Virtually all empirical ecological interaction networks to some extent suffer from undersampling. However, how limitations imposed by sampling incompleteness affect our understanding of ecological networks is still poorly explored, which may hinder further advances in the field.
Here, we use a plant–hummingbird network with unprecedented sampling effort (2716 h of focal observations) from the Atlantic Rainforest in Brazil, to investigate how sampling effort affects the description of network structure (i.e. widely used network metrics) and the relative importance of distinct processes (i.e. species abundances vs. traits) in determining the frequency of pairwise interactions.
By dividing the network into time slices representing a gradient of sampling effort, we show that quantitative metrics, such as interaction evenness, specialization ( H 2 ′), weighted nestedness (wNODF) and modularity ( Q ; QuanBiMo algorithm) were less biased by sampling incompleteness than binary metrics. Furthermore, the significance of some network metrics changed along the sampling effort gradient. Nevertheless, the higher importance of traits in structuring the network was apparent even with small sampling effort.
Our results (i) warn against using very poorly sampled networks as this may bias our understanding of networks, both their patterns and structuring processes, (ii) encourage the use of quantitative metrics little influenced by sampling when performing spatio‐temporal comparisons and (iii) indicate that in networks strongly constrained by species traits, such as plant–hummingbird networks, even small sampling is sufficient to detect their relative importance for the frequencies of interactions. Finally, we argue that similar effects of sampling are expected for other highly specialized subnetworks.
Globalization has increased the speed and flow of people, information, and commodities across space, integrating markets and increasing interdependence of geographically dispersed places worldwide. Places historically driven by largely local forces and market demands are now increasingly affected by drivers at multiple scales. Trade is particularly important in driving these changes and more fish is now exported to international markets than ever before. When small-scale fisheries are integrated into global markets, local social–ecological systems change with potentially both positive and negative impacts on livelihoods, economics and ecology, but few studies systematically investigate how and why the outcomes of market integration vary from case to case.
One contribution of 16 to a Theme Issue 'Marine regime shifts around the globe: theory, drivers and impacts'. Regime shifts have been observed in marine ecosystems around the world, with climate and fishing suggested as major drivers of such shifts. The global and regional dynamics of the climate system have been studied in this context, and efforts to develop an analogous understanding of fishing activities are developing. Here, we investigate the timing of pelagic marine regime shifts in relation to the emergence of regional and global fishing activities of the Soviet Union. Our investigation of official catch statistics reflects that the Soviet Union was a major fishing actor in all large marine ecosystems where regime shifts have been documented, including in ecosystems where overfishing has been established as a key driver of these changes (in the Baltic and Black Seas and the Scotian Shelf). Globalization of Soviet Union fishing activities pushed exploitation to radically new levels and triggered regional and global governance responses for improved management. Since then, exploitation levels have remained and increased with new actors involved. Based on our exploratory work, we propose that a deeper understanding of the role of global fishing actors is central for improved management of marine ecosystems.
The relationship between fish market price and body size has not been explored much in fisheries science. Here, the mean market prices and fish body size were collected in order to examine the hypothesis that large fish, both among- and within-species, are being selectively targeted by fisheries because they may yield greater profit. Trophic levels, vulnerability to fishing and global landings were also collected because these variables may also be related to the market fish price. These relationships were examined using generalized additive models (GAM), which showed that, among species, fish market price was positively dependent on maximum total length (P = 0.0024) and negatively on landings (P = 0.0006), whereas it was independent of trophic level (P > 0.05) and vulnerability to fishing (P > 0.05). When the fish price vs. size relationship was tested within-species, large individuals were consistently attaining higher market prices compared to their medium and small-sized counterparts. We conclude that the selective removal of the larger fish, which is driven by their market price and to a lesser extent by their availability, may contribute to their overfishing.
O recurso pesqueiro da bacia do rio Cuiabá, um dos mais importantes tributários da bacia do Alto Paraguai, formadora do Pantanal, foi estudado a partir dos dados de desembarque de pescado obtidos no Mercado do Porto de Cuiabá, Mato Grosso, Brasil. São descritas a composição e procedência das capturas para os anos de 2000 e 2001. O rio Cuiabá é a fonte dominante de pescado para a cidade de Cuiabá, mas uma parte do pescado comercializado localmente é oriunda do rio Paraguai. Além disso, atualmente o pescado vem de regiões mais distantes da zona urbana. Constatou-se que a pesca incide basicamente sobre espécies migradoras. As principais espécies capturadas foram os pimelodídeos pintado -Pseudoplatystoma corruscans, cachara -Pseudoplatystoma fasciatum e jaú -Paulicea luetkeni e os caraciformes pacu -Piaractus mesopotamicus, piraputanga -Brycon microlepis, piavuçu -Leporinus macrocephalus e dourado -Salminus brasiliensis. Os grandes bagres (Pimelodidae) foram os responsáveis por 70% do pescado desembarcado no período de estudo, dentre os quais o pintado foi a espécie mais capturada. Os dados indicam que as capturas atuais estão bem aquém daquelas registradas no início da década de 80. Além disso, apesar do número e composição de espécies capturadas serem similares àqueles da década de 80, a distribuição da abundância mudou. Atualmente a pesca captura mais espécies carnívoras do que espécies de níveis tróficos inferiores. Estes achados não podem ser creditados somente a sobrepesca, mas parecem resultar de uma complexa interação entre degradação ambiental, mudanças na preferência de mercado e medidas legais restritivas à pesca.
We present a comprehensive approach to detect pattern in assemblages of plant and animal species linked by interactions such as pollination, frugivory or herbivory. Simple structural models produce gradient, compartmented or nested patterns of interaction; intermediate patterns between a gradient and compartments are possible, and nesting within compartments produces a combined model. Interaction patterns can be visualized and analyzed either as matrices, as bipartite networks or as multivariate sets through correspondence analysis. We argue that differences among patterns represent outcomes of distinct evolutionary and ecological processes in these highly diversified assemblages. Instead of choosing one model a priori, assemblages should be probed for a suite of patterns. A plant–pollinator assemblage exemplifies a simple nested pattern, whereas a plant–herbivore assemblage illustrates a compound pattern with nested structures within compartments. Compartmentation should reflect coevolutionary histories and constraints, whereas differences in species abundance or dispersal may generate nestedness.
Anthropogenic global warming has significantly influenced physical and biological processes at global and regional scales. The observed and anticipated changes in global climate present significant opportunities and challenges for societies and economies. We compare the vulnerability of 132 national economies to potential climate change impacts on their capture fisheries using an indicator-based approach. Countries in Central and Western Africa (e.g. Malawi, Guinea, Senegal, and Uganda), Peru and Colombia in north-western South America, and four tropical Asian countries (Bangladesh, Cambodia, Pakistan, and Yemen) were identified as most vulnerable. This vulnerability was due to the combined effect of predicted warming, the relative importance of fisheries to national economies and diets, and limited societal capacity to adapt to potential impacts and opportunities. Many vulnerable countries were also among the world’s least developed countries whose inhabitants are among the world’s poorest and twice as reliant on fish, which provides 27% of dietary protein compared to 13% in less vulnerable countries. These countries also produce 20% of the world’s fish exports and are in greatest need of adaptation planning to maintain or enhance the contribution that fisheries can make to poverty reduction. Although the precise impacts and direction of climate-driven change for particular fish stocks and fisheries are uncertain, our analysis suggests they are likely to lead to either increased economic hardship or missed opportunities for development in countries that depend upon fisheries but lack the capacity to adapt.
The Pantanal of Mato Grosso, Brazil, is famous for its luxurious plant and animal life. We combine a literature review with
recent work and show that species diversity is large but that most major plant and animal groups contain a large number of
not wetland-specific species that depend on permanently terrestrial habitats within the Pantanal, or are restricted to dry
areas during the low water period. These species occur also in the neighbouring biomes of Cerrado, Amazon Forest or Chaco.
Until now, very few endemic species have been described, however, there are large populations of species in the Pantanal that
are considered rare or endangered in South America. The number of trees adapted to long term flooding is low in comparison
with the Amazon River floodplain. We hypothesize that the reason for the lack of local endemisms and the occurrence of a large
number of species with a large ecological amplitude is the climatic instability of the region of the Pantanal, which suffered
severe drought during glacial periods. The instability of the actual climate, which is characterized by multi-annual wet and
dry periods, has a strong impact on distribution, community structure and population size of many plant and animal species
and hinders spatial segregation of populations. The dependence of the system on the flood pulse makes the Pantanal very vulnerable
to human induced changes in hydrology and the predicted changes in global climate.
Time/area closures have been widely used in fisheries management to prevent overfishing and the destruction of marine biodiversity. To a lesser degree, such spatio-temporal management measures have been used to reduce by-catch of finfish or protected species. However, as ecosystem-based management approaches are employed and more fisheries are managed through multispecies, multiobjective models, the management of by-catch will likely become increasingly important. The elimination of by-catch has become a primary goal of the fishing policies of many countries. It is particularly relevant in the United States, as the deadline for setting annual catch limits (ACLs) in all fisheries passes in 2011. This will result in a dramatic expansion of the number of catch and by-catch quotas. Such catch measures may result in the early closure of otherwise sustainable fisheries when by-catch quotas are exceeded. To prevent such closures and the consequent economic hardship to fishers and the economy, it is imperative that managers be given the tools necessary to reduce by-catch and improve fishing selectivity. Targeted spatio-temporal fishery closures are one solution open to managers. Here, we examine how the spatio-temporal and oceanographic characteristics of by-catch may be used by managers to design fishery closures, and place these methods within a decision tree to assist managers to identify appropriate management measures. We argue that the Correspondence:
In this paper, we first look retrospectively at the perceptions embraced by academics, international agencies and practitioners of the relation between fisheries and poverty in developing countries and we try to identify the underlying paradigms which have structured these perceptions. The review reveals how the debate has focused on the economic (low income) and biological (overexploitation) aspects of the problem. We then revisit these perceptions in the light of the recent conclusions drawn from other sectors and in particular from the new “consensus” on poverty proposed by the international community. Incorporation of the recent research on poverty helps to show how socio-institutional mechanisms governing people’s access to fisheries resources––rather than the resources themselves––play such a critical role in vulnerability to poverty. Finally, a typology identifying four different categories of intrasectoral exclusion mechanisms is developed and illustrated through empirical studies derived from African and Asian fisheries.
Engagement in the market changes the opportunities and strategies of forest-related peoples. Efforts to support rural development need to better understand the potential importance of markets and the way people respond to them. To this end, we compared 61 case studies of the commercial production and trade of nontimber forest products from Asia, Africa, and Latin America. The results show that product use is shaped by local markets and institutions, resource abundance, and the relative level of development. Larger regional patterns are also important. High-value products tend to be managed intensively by specialized producers and yield substantially higher incomes than those generated by the less specialized producers of less managed, low-value products. We conclude that commercial trade drives a process of intensified production and household specialization among forest peoples.
Marine artisanal fisheries make vital contributions to food security, livelihoods, jobs, and income in coastal communities globally. However, resources vary as a result of changes in oceanographic conditions such as sea surface temperature or wind stress, which impacts communities and also makes them more sensitive to other stressors such as climate change. In Peru, small-scale fisheries are paramount to the country's economy and food security. They are also one of most globally affected by interannual changes and potentially impacted by climate change. Assessing their present and future vulnerability and finding adaptation strategies are key to the sustainability of the sector and the livelihoods of many. This study assesses the local vulnerability in the Huaura province, Peru, where three fishing communities of very different socio-economic characteristics share the same fishing ground. The region is very sensitive to changes associated with El Niño. We assess the ecological and socio-economic vulnerability using governmental and local information, to pinpoint the main drivers of vulnerability. We find stark differences between communities: Carquín shows the greatest dependence on artisanal fishing for income and a low adaptive capacity, whereas Huacho, a larger and more diversified economy, presents greater livelihood alternatives for the artisanal fishermen. The future vulnerability analysis highlights the need to implement adaptation measures, including: economic diversification; forms to add value to the artisanal fishing; sustainable management of fishing grounds; and actions that help manage shocks from interannual variations, such as monitoring and prediction systems, but also financing mechanisms that could attenuate the socio-economic impacts.
Literature in the vulnerability of socio-ecological systems has highlighted the need for considering Social Perception of Risk (SPR) as a determinant of social vulnerability. This paper combines quantitative and qualitative approaches for analyzing SPR in the context of a socio-ecological system. We analyze the SPR of loss or degradation of water provision and erosion control in the Northern Andes (Riogrande basin, Antioquia-Colombia). In our case study beneficiaries assign high importance to water provision and erosion control ecosystem services and recognize that in some cases their productive practices degrade the capacity of the ecosystems to provide such services. The results of the quantitative approach indicate that variables such as age, income, number of children in charge, size of the land, participation in environmental issues and knowledge of environmental topics influence on the level of perception of risk of loss or degradation of both ecosystem services. The economic activity, the number of years that the beneficiary has been in the study area and the relationship with institutions influence the perception of risk associated with erosion but not with water. Based on the results we propose strategies to cope with social vulnerability.
The analysis of vulnerability of socio-ecological systems to threats of different types such as extreme climate events or change in land use draws attention to the factors and processes that determine whether the ecological, social and integrated socio-ecological systems are likely to experience harm due to exposure to the threat. During the last years there has been an increasing attention to the analysis of the vulnerability of socio-ecological systems when facing the lost or degradation of ecosystem services. However, despite the existence of conceptual frameworks and empirical applications to evaluate vulnerability of socio-ecological systems some open questions and challenges still remain. How to conceptually differentiate key concepts such as sensitivity, exposition, vulnerability and threat? How to consider the differences in socio-economic characteristics of the beneficiaries and in their capacity to adapt to new conditions of the ecological system? How to link ecological vulnerability with the social system analysis to obtain an integrated risk assessment of the socio-ecological system? This paper presents a conceptual framework for vulnerability assessment of socio-ecological systems that addresses the mentioned open questions based on a review of both theoretical and empirical literature related to vulnerability and socio-ecological systems. The paper identifies the attributes and indicators of the dimensions of vulnerability for understanding both the social vulnerability and ecological vulnerability separately and then jointly, in interaction with each other. The framework offers a way to communicate with practitioners and policy makers on identifying and improving the factors that reduce vulnerability. It can thus serve as a tool for targeting the implementation of policies and practices aimed at reducing vulnerability.
What do telephones, televisions, and telescopes have in common? They are devices for transmitting sounds or images over distances. In much the same way, a new scientific paradigm – the telecoupling framework – enables simultaneous assessment of socioeconomic and environmental interactions among local and distant locations. The framework is revolutionizing the way social and natural scientists understand and provide for sustainable resource management over space and time in our increasingly connected world. The telecoupling framework was developed from the integration of two different but related concepts: teleconnections (i.e., environmental interactions among natural systems over geographic space and time) and globalization (i.e., socioeconomic interactions among human systems over distances). The framework focuses on the structure, functioning, dynamics, trade-offs, and synergies of “telecouplings”: socioeconomic and environmental interactions among human and natural systems over distances. Because fish promote global food and nutrition security and support a growing aquaculture sector and commercial, recreational, and subsistence industries, fisheries are ideal systems in which to apply the telecoupling framework to better understand the impacts of local and more distant socioeconomic and environmental interactions that alter fisheries productivity, thereby yielding insights for fisheries management.
Assessment of fisheries vulnerability to climate change is an important step for enhancing the understanding and decision-making to reduce such vulnerability. This study aimed to provide an analysis of country level vulnerability focusing on food security implications of climatic disturbances on marine fisheries. The comparative magnitude and distribution of potential food security impacts of climatic disturbances on marine fisheries were assessed for 109 countries by scoring and ranking countries against a set of vulnerability criteria including metrics of national exposure, sensitivity and adaptive capacity, highlighting the contribution of marine fisheries to national food and nutrition security. Results showed that developing countries in Africa, Asia, Oceania, and Latin America appeared to be most vulnerable, and the key sources of vulnerability differed considerably among the countries. For countries most vulnerable to climate-induced effects on marine fisheries, more than two-thirds of them depended on domestic marine fisheries as a main source of fish supply. Developing appropriate adaptation policies and management plans to reduce the impacts of changing climate is of great importance to sustain food security in these highly vulnerable and heavy marine fisheries-dependent countries.
Two disparate views of the sexual division of labour have dominated the representation of intra-household resource allocations. These . joint and . separate interests views differ in their interpretation of the relative roles of men and women, and make different predictions about the extent to which marriage promotes economic efficiency (i.e. maximized household production). Using an experimental distribution task stipulating a trade-off between household efficiency and spousal equality in allocating surpluses of meat and money, we examine factors influencing spousal distribution preferences among Tsimane forager-horticulturalists of Bolivia (n. =53 couples). Our primary goal is to understand whether and how access to perfectly fungible and liquid resources - which increases with greater participation in market economies - shifts intra-household distribution preferences. We hypothesize that greater fungibility of money compared to meat results in greater squandering of money for individual fitness gain at a cost to the family. Money therefore requires costly strategies to insure against a partner's claims for consumption. Whereas nearly all Tsimane spouses prefer efficient meat distributions, we find a substantially reduced efficiency preference for money compared to meat controlling for potential confounders (adjusted OR. =0.087, 95% CI: 0.02-0.38). Reported marital conflict over paternal disinvestment is associated with a nearly 13-fold increase in odds of revealing a selfish money distribution preference. Selfish husbands are significantly more likely than other husbands to be paired with selfish wives. Lastly, Tsimane husbands and wives are more likely than Western Europeans to prefer an efficient money distribution, but Tsimane wives are more likely than Western European wives to exhibit a selfish preference. In sum, preferences for the distribution of household production surplus support joint and separate interests views of marriage; a hybrid approach best explains how ecological-, family-, and individual-level factors influence spousal preferences through their effects on perceptions of marginal gains within and outside the household.
Network approaches have become a popular tool for understanding ecological complexity in a changing world. Many network descriptors relate directly or indirectly to specialization, which is a central concept in ecology and measured in different ways. Unfortunately, quantification of specialization and network structure using field data can suffer from sampling effects. Previous studies evaluating such sampling effects either used field data where the true network structure is unknown, or they simulated sampling based on completely generalized interactions. Here, we used a quantitative niche model to generate bipartite networks representing a wide range of specialization and evaluated potential sampling biases for a large set of specialization and network metrics for different network sizes. We show that with sample sizes realistic for species-rich networks, all metrics are biased towards overestimating specialization (and underestimating generalization and niche overlap). Importantly, this sampling bias depends on the true degree of specialization and is strongest for generalized networks. As a result, null models simulating generalized interactions may misrepresent sampling bias. We show that other methods used for empirical data may be biased in the opposite direction and strongly overestimate sampling completeness. Some network metrics are barely related between small and large sub-samples of the same network and thus may often not be meaningful. Small samples also overestimate interspecific variation of specialization within generalized networks. While new approaches to deal with these challenges have to be developed, we also identify metrics that are relatively unbiased and fairly consistent across sampling intensities and we identify a provisional rule of thumb for the number of observations required for accurate estimates. Our quantitative niche model can help understand variation in network structure capturing both sampling effects and biological meaning. This is needed to connect network science to fundamental ecological theory and to give robust quantitative answers for applied ecological problems.This article is protected by copyright. All rights reserved.
While previous research has documented marine fish and invertebrates shifting poleward in response to warming climates, less is known about the response of fisheries to these changes. By examining fisheries in the northeastern United States over the last four decades of warming temperatures, we show that northward shifts in species distributions were matched by corresponding northward shifts in fisheries. The proportion of warm-water species caught in most states also increased through time. Most importantly, however, fisheries shifted only 10–30 % as much as their target species, and evidence suggested that economic and regulatory constraints played important roles in creating these lags. These lags may lead to overfishing and population declines if not accounted for in fisheries management and climate adaptation. In coupled natural-human systems such as fisheries, human actions play important roles in determining the sustainability of the system and, therefore, future conservation and climate mitigation planning will need to consider not only biophysical changes, but also human responses to these changes and the feedbacks that these responses have on ecosystems.
The relations between hydrology, geomorphology and vegetation provide the basis for understanding the ecological processes in the floodplains of rivers. In this paper, long-term (1969-2009) local flood characteristics (magnitude, duration, frequency, return period) are quantified for the floodplain of the Cuiaba River (Pantanal wetland in Brazil), using a predictive model based on artificial neural networks (ANNs) with input given by the historic river-level record. Morphological features were then described and their relation to vegetation analyzed and used to reconstruct floods. In addition to the river-level data used to train and validate a three-layer ANN, data were also used from 11 floodplain gauges across a 12 km transect lateral to the river, which were monitored during the annual floods of 2004-2007. The resulting neural network gave satisfactory estimates of water depth over the floodplain, with an absolute error of 0.09 m not exceeded in 95% of occurrences. The ANN showed that in almost all years, the level reached by the river was high enough to flood the profile completely: the exceptions were 1971 and 2001 when only 50% and 58% was flooded, to mean depths of 0.34 and 0.48 m, respectively. The highest flood was that of 1995 when the floodplain was flooded to a mean depth of 2.56 m. The median flood event (return period 2 years) produced a mean flood depth 1.80 m and lasted 119 days. Among the most important morphological features is the presence of palaeo-channels which provide hydrological connectivity between the river and the floodplain. The distribution of phytophysiognomic units is significantly influenced by local geomorphology, which determines spatial variation in the magnitude, duration, and frequency of flooding. (C) 2011 Published by Elsevier B.V.
Over long geological time periods, South America offered a large variety of waterbodies and habitats to aquatic organisms. Large river systems and streams of different water quality, different types of wetlands and high-altitude lakes favoured the development of a species-rich fish fauna with a large variety of adaptations. Therefore, South America is today a centre of megadiversity of fishes. In large areas, aquatic habitat health is still intact but environmental degradation is accelerating with negative impacts on the fish fauna. Inland fisheries are of great importance for protein supply of the local population, but stocks are already depleted in some areas. Fish culture is becoming increasingly important to supplement decreasing catches but cannot prevent loss of biodiversity. Lack of knowledge about fishes and their habitats, inefficient management of aquatic resources, large-scale uncoordinated modification of catchment areas, and the low priority given by the governments to fisheries and the protection of aquatic and wetland systems are reasons for decreasing fish stocks, deterioration of aquatic habitat health, and decreasing species numbers. A summary of the status of fish biodiversity, fishery, fish culture and habitat health in major South American rivers systems, the Altiplano and Patagonia is provided and the possibilities for sustainable management of aquatic resources and the protection of fish biodiversity are discussed.
There appears to be considerable potential for further reduction in global by-catch. This reduction is most likely to be achieved by focusing even greater attention on the technical, regulatory and social approaches that are currently practiced. With respect to the technical approaches, meta-analysis indicates that overall reductions in by-catch of between 25% and 64% could be achieved if global fishing fleets could match somewhere between the minimum and median performance of gear modifications used in experimental studies. If such benefits are to be delivered, however, engaging fishers more comprehensively in solving the problems will be essential. Further developing legislative and institutional arrangements will also assist. However, notwithstanding the potential gains that can be achieved, it must be recognized that careful analysis will often be required to ensure that a proposed measure will achieve the desired objective at an acceptable cost.
This paper reviews the present state of reef fishing activities in Kenya and the tropics using the driver–pressure–state–impacts–response (DPSIR) framework. It identifies appropriate indicators that would evaluate the problem of overfishing and the use of destructive fishing gear, and discusses policy considerations for the Kenyan small-scale fishery. We conclude that the DPSIR framework works well at simplifying the complexity of reef fisheries management and serves to inform policy makers, scientists and general public on the relevance of indicators to monitor changes in the status of reefs.
Changes in the management of the fin fish fishery of the Great Barrier Reef motivated us to investigate the combined effects on economic returns and fish biomass of no-take areas and regulated total allowable catch allocated in the form of individual transferable quotas (such quotas apportion the total allowable catch as fishing rights and permits the buying and selling of these rights among fishers). We built a spatially explicit biological and economic model of the fishery to analyze the trade-offs between maintaining given levels of fish biomass and the net financial returns from fishing under different management regimes. Results of the scenarios we modeled suggested that a decrease in total allowable catch at high levels of harvest either increased net returns or lowered them only slightly, but increased biomass by up to 10% for a wide range of reserve sizes and an increase in the reserve area from none to 16% did not greatly change net returns at any catch level. Thus, catch shares and no-take reserves can be complementary and when these methods are used jointly they promote lower total allowable catches when harvest is relatively high and encourage larger no-take areas when they are small.
"Community initiatives to regulate the exploitation of lake fisheries have proliferated in the lower Amazon, and may now be legalised as co-management agreements whereby the government endorses and enforces community rules. Most agreements aim to raise stock abundance and thereby the productivity of lake fisheries by limiting exploitation by larger, often external commercial boats as well as by local fishers. This study evaluates the perceived and actual impact of co-management agreements on fisheries exploitation and productivity by comparing lake fisheries within and outside agreements. A survey was conducted in 18 paired communities with and without co-management agreements (i.e. 9 pairs of a co-managed and non-managed fishery each). Rules in comanaged fisheries typically comprised restrictions on the use of gill nets, daily catch limits and limits on the size of boats. A total of 259 households (13 or 18 per community) were surveyed to estimate local fishing effort and catch. Non-managed fisheries were subject to additional fishing by external commercial boats which could not be quantified independently, but has been accounted for in the analysis. Results showed a reasonable degree of perceived and actual compliance within the communities with comanagement agreements. The productivity (catch per unit of effort) of managed fisheries was significantly higher, by about 60%, than that of non-managed fisheries even though no significant difference in household fishing effort was detected. An empirical model relating fishing effort and yield per unit area was derived for a sub-set of lakes (both managed and non-managed) where lake area could be clearly delineated and fishing was carried out predominantly by communities covered in the survey (i.e. excluding lakes shared by several communities). Fishing effort explained much of the variation in yield between lakes. Managed lakes showed significantly higher levels of yield and productivity (by about 70%) than non-managed lakes for the same level of fishing effort. This difference is likely to reflect the additional, non-quantified fishing effort and catch by external commercial boats in non-managed lakes. We conclude that the comanagement agreements have brought significant yield and productivity benefits to the communities implementing them, largely as a result of reduced commercial fishing by outsiders. The yield predictive model derived in this study provides a quantitative tool for assessing effects of effort regulation within co-management fisheries."