One method with considerable potential for understanding fishing and environmental impacts on fish assemblages is size spectra (SS) and diversity size spectra (DSS) analysis—a regression of Ln ...abundance or Shannon diversity against the natural logarithm of body size of fish assemblages. But the usefulness of this method for application to tropical freshwater fish assemblages is uncertain. Here, we assessed the extent to which SS and DSS analyses explained changes in the exploited fish assemblage related to fishing effort and river droughts. To do this, we used correlation analyses on historical datasets of river water level, fishing effort, and fish length measurements for 56 fish species in three of the largest rivers of the Amazon Basin. In calculating the SS and DSS analysis statistics, we found that linear regressions adjusted well to the diversity and Ln(abundance) data plotted against Ln(fork length). In analysing SS and DSS statistics in relation to fishing and environmental impacts, we found that the slope of SS was negatively correlated to drought intensity with a lag of zero years in all rivers. The slope of SS also was negatively correlated to fishing effort with a lag of three years in two rivers and a lag of two years in one year. The slope of DSS was not correlated to drought intensity and fishing effort in any of the rivers. Our results provide support for the use of SS analysis to investigate fishing and environmental effects on exploited fish assemblages in tropical freshwater environments.
This study investigated the environmental factors influencing the distribution of the endangered arapaima (Arapaima spp.) in floodplains of the Amazon. The abundance of arapaima was found to be ...positively related to the area and depth of the water column, and hence volume of lakes. Greater depth of water column also was related positively with the abundance and presence of arapaima in connecting channels. The abundance of arapaima was positively related to the connectivity of the lake with other water bodies. The principal reason for arapaima to prefer habitats that are deep, large, and connected to other water bodies appears to be increased survival through lower susceptibility to extreme drought events and increased mobility and availability of food resources. Deeper, larger, and more connected lakes and connecting channels sustain greater arapaima populations; they can now be used to prioritize conservation efforts.
Fishers and small-scale fisheries worldwide have been marginalized historically. Now it is clear that integrating fishers in management processes is key to resource conservation, but it is less clear ...how to do it. Here, based on a literature review and new information, we present and analyze a case in which the participation of fishers in the management process was crucial in recovering an overexploited small-scale fishery for the pirarucu (Arapaima spp.) in the Amazon Basin, Brazil. In 8 years of experimental management, from 1999 to 2006, the population of pirarucu increased 9-fold (from about 2200 to 20,650 individuals), harvest quotas increased 10-fold (from 120 to 1249 individuals), and fishers' participation in the management process increased and they benefited from increased monetary returns. Additionally, the number of communities conducting the management scheme increased from 4 in 1999 to 108 in 2006, following the demands of fishers and regional government agencies. Based on our analysis, we suggest that the participation of fishers in the management of other small-scale fisheries in the world can be improved by focusing on (1) applying the knowledge and skills of fishers in resource monitoring and management, (2) bridging knowledge systems among all involved stakeholders, (3) collaborating with fishers that are interested in, and capable of conducting, resource conservation schemes, and (4) conducting management under conditions of uncertainty.
The term “data-limited fisheries” is a catch-all to generally describe situations lacking data to support a fully integrated stock assessment model. Data conditions range from data-void fisheries to ...those that reliably produce quantitative assessments. However, successful fishery assessment can also be limited by resources (e.g., time, money, capacity). The term “data-limited fisheries” is therefore too vague and incomplete to describe such wide-ranging conditions, and subsequent needs for management vary greatly according to each fishery’s context. Here, we acknowledge this relativity and identify a range of factors that can constrain the ability of analyses to inform management, by instead defining the state of being “data-limited” as a continuum along axes of data (e.g., type, quality, and quantity) and resources (e.g., time, funding, capacity). We introduce a tool (the DLMapper) to apply this approach and define where a fishery lies on this relativity spectrum of limitations (i.e. from no data and no resources to no constraints on data and resources). We also provide a ranking of guiding principles, as a function of the limiting conditions. This high-level guidance is meant to identify current actions to consider for overcoming issues associated with data and resource constraints given a specific “data-limited” condition. We apply this method to 20 different fisheries to demonstrate the approach. By more explicitly outlining the various conditions that create “data-limited situations” and linking these to broad guidance, we aim to contextualize and improve the communication of conditions, and identify effective opportunities to continue to develop and progress the science of “limited” stock assessment in support of fisheries management.
Species of the genus Pseudoplatystoma, the long-whiskered catfishes, are important in commercial and recreational fisheries in South America, and some species have become key to regional aquaculture. ...Some species of the genus are under pressure due to overfishing and the negative impacts of dams. Six questions are asked in this review: (i) What species are in the genus, and where are they distributed? (ii) What are the life histories and ecologies of Pseudoplatystoma species? (iii) What are the patterns of somatic growth for these species? (iv) What is known about the biomass, production, and population dynamics of Pseudoplatystoma? (v) What is the geographic distribution of genetic variation within Pseudoplatystoma species? (vi) What are the threats to the conservation of these species? The taxonomy of the genus currently includes eight species, respectively, distributed over the Orinoco, Amazon, Paraná, and São Francisco basins. Pseudoplatystoma catfishes typically exhibit longitudinal migrations for reproduction and lateral migration for feeding, but these patterns may vary among populations. The size of the first maturation of these catfishes varies between 57 cm to 82 cm in total length. Five of the eight species spawn during the rising water season. Pseudoplatystoma species can grow to about 130 cm in total length and 100 Kg in weight and live until 30 years of age, depending upon the species. Biomass production and population dynamics of these catfishes have not yet been fully described. Their life-history characteristics indicate that they are periodic strategists with associated population recruitment dynamics. Population genetic patterning varies among Pseudoplatystoma species, with some degree of homing behavior and genetic differentiation among populations, indicating the need for management by applying the Management Unit and perhaps Evolutionary Significant Unit concepts. The main threats to the persistence of these catfishes are overfishing and alterations in and obstruction of river flow due to the construction of hydropower dams. After synthesizing existing information on species of the genus Pseudoplatystoma, we offer suggestions for future research to fill critical gaps in the knowledge of this group.
Energy development – as manifested by the proliferation of hydroelectric dams and increased oil and gas exploration – is a driver of change in Amazonian ecosystems. However, prevailing approaches to ...Amazonian ecosystem conservation that focus on terrestrial protected areas and Indigenous territories do not offer sufficient insurance against the risks associated with energy development. Here, we explore three related areas of concern: the exclusion of subsurface rights on Indigenous lands; the absence of frameworks for freshwater ecosystem conservation; and downgrading, downsizing, degazettement (loss of protection), and reclassification of protected areas. We consider these issues from the perspectives of multiple countries across the Amazon Basin, and link them directly to energy development. Finally, we offer suggestions for addressing the challenges of energy development for Amazon ecosystem conservation through existing policies, new approaches, and international collaboration.
Arapaima are listed as endangered fishes according to the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES), thus their international trade is regulated by ...non-detriment finding (NDF) procedures. The authors critically assessed Brazil's regulations for NDF procedures for Arapaima using IUCN's checklist for making NDFs, and found that those regulations cannot ensure the sustainability of Arapaima populations. Arapaima are among the largest fishes in the world, migrate short distances among several floodplain habitats, and are very vulnerable to fishing during spawning. They are threatened mainly by overfishing. The fishery is largely unregulated because government regulations on size, season, and even moratoriums on capture have been very poorly enforced. Arapaima remain poorly understood and the taxonomy and geographical distribution of the genus remain uncertain. There are no data on catch levels or status of wild populations, although available information suggests they are in decline. Brazil's NDF procedures for specimens originating in the wild are inadequate as they rely on 'technical opinion reports', which do not necessarily require scientific evidence. Furthermore, Brazil's NDF procedures exempt the need for NDF reports on 'captive' specimens; however, 'captive' specimens originating in the wild and raised in captivity can be exported because regulations do not specify that they must be 'captive-bred'. Six suggestions are offered to improve the reliability of NDF procedures for Arapaima in Brazil, emphasizing the utility of participatory monitoring and adaptive harvesting to strengthen much needed harvest control capacity in other tropical fisheries.
Fish in the South American genus Arapaima Müller, 1843 (hereafter referred to as arapaimas) have attracted interest for commercial aquaculture development thanks to their rapid growth rate and high ...market value. However, management agencies in the United States have expressed concerns about importing and culturing arapaimas due to records of non-native establishment in certain other countries where arapaimas were released or escaped from captivity. We used the Freshwater Fish Injurious Species Risk Assessment Model (FISRAM) to estimate the probability that arapaimas would be injurious (able to cause harm) to native ecosystems, humans, or the economy of the contiguous United States. Risk assessment model inputs were elicited from arapaima experts around the world. Model results were sensitive to the estimation of climate suitability for arapaimas within the contiguous United States, with predicted probability of injuriousness ranging from 0.784 down to 0.321 with different climate suitability inputs. Expert assessors predicted that competition and predation on native species would be the most likely mechanism of impact and expressed a high degree of uncertainty about potential for impacts from pathogens and parasites. We concluded that due to the cold sensitivity of these tropically adapted fish, establishment within the contiguous United States would be highly restricted geographically, limiting potential impacts if introduced outside climatically suitable areas. Existing regulations already mitigate risk of escape from aquaculture in areas where establishment is plausible, but further research into arapaima parasites and pathogens would help reduce uncertainties and suggest opportunities to enhance biosecurity measures if needed.
Information on natural resource exploitation is vital for conservation but scarce in developing nations, which encompass most of the world and often lack the capacity to produce it. A growing ...approach to generate information about resource use in the context of developing nations relies on surveys of resource users about their recollections (recall) of past harvests. However, the reliability of harvest recalls remains unclear. Here, we show that harvest recalls can be as accurate to data collected by standardized protocols, despite that recalls are variable and affected by the age of the recollecting person and the length of time elapsed since the event. Samples of harvest recalls permit relatively reliable reconstruction of harvests for up to 39 years in the past. Harvest recalls therefore have strong potential to inform data‐poor resource systems and curb shifting baselines around the world at a fraction of the cost of conventional approaches.
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