Beyond biodiversity: fish metagenomes

Biodiversity and intra-specific genetic diversity are interrelated and determine the potential of a community to survive and evolve. Both are considered together in Prokaryote communities treated as metagenomes or ensembles of functional variants beyond species limits.Many factors alter biodiversity in higher Eukaryote communities, and human exploitation can be one of the most important for some groups of plants and animals. For example, fisheries can modify both biodiversity and genetic diversity (intra specific). Intra-specific diversity can be drastically altered by overfishing. Intense fishing pressure on one stock may imply extinction of some genetic variants and subsequent loss of intra-specific diversity. The objective of this study was to apply a metagenome approach to fish communities and explore its value for rapid evaluation of biodiversity and genetic diversity at community level. Here we have applied the metagenome approach employing the barcoding target gene coi as a model sequence in catch from four very different fish assemblages exploited by fisheries: freshwater communities from the Amazon River and northern Spanish rivers, and marine communities from the Cantabric and Mediterranean seas.Treating all sequences obtained from each regional catch as a biological unit (exploited community) we found that metagenomic diversity indices of the Amazonian catch sample here examined were lower than expected. Reduced diversity could be explained, at least partially, by overexploitation of the fish community that had been independently estimated by other methods.We propose using a metagenome approach for estimating diversity in Eukaryote communities and early evaluating genetic variation losses at multi-species level.     

Landscape variables affecting fishery yield in lake systems of the Central Amazon region, Brazil

According to fisheries data, lakes are important systems for fish production in the Amazon basin. However, there is no information about the relationship between landscape variables and fishing yield that allows foresight into potential resource exploitation in this environment. The present study aims to evaluate this relationship with the hypothesis: lakes of different shapes give the same fishery yield in the Amazon, after considering the effects of lake size, distance to the river, fishing effort, fuel and ice used. Fishery data from 1994 to 1996 were analyzed with regard to 3228 trips on 50 lakes of the main white water tributaries of the Amazon basin. Analysis of covariance was applied to test this hypothesis. With variables such as fishing grounds access, fishing effort and lake shape the model explained a significant 72% of variabilities in the fisheries yield. Fishing yields among lake systems were different, thus the null hypothesis was rejected (P < 0.05). Results indicate that dendritic lakes far distant from the main river have greater productivity than floodplain lakes because there are more habitats of fish refuge for reproduction and feed available to the fish; there are also more limitations to access by predators.     

Species trait diversity sustains multiple dietary nutrients supplied by freshwater fisheries

Species, through their traits, influence how ecosystems simultaneously sustain multiple functions. However, it is unclear how trait diversity sustains the multiple contributions biodiversity makes to people. Freshwater fisheries nourish hundreds of millions of people globally, but overharvesting and river fragmentation are increasingly affecting catches. We analyse how loss of nutritional trait diversity in consumed fish portfolios affects the simultaneous provisioning of six essential dietary nutrients using household data from the Amazon and Tonlé Sap, two of Earth's most productive and diverse freshwater fisheries. We find that fish portfolios with high trait diversity meet higher thresholds of required daily intakes for a greater variety of nutrients with less fish biomass. This beneficial biodiversity effect is driven by low redundancy in species nutrient content profiles. Our findings imply that sustaining the dietary contributions fish make to people given declining biodiversity could require more biomass and ultimately exacerbate fishing pressure in already-stressed ecosystems.     

Fish functional diversity as an indicator of resilience to industrial fishing in Patagonia Argentina

The relationship between fish functional diversity and fishing levels at which its baselines shift is important to identify the consequences of fishing in ecosystem functioning. For the first time, the authors of this study implemented a trait-based approach in the Argentine Patagonian Sea to identify the vulnerability and spatiotemporal changes in functional diversity of fish assemblages incidentally captured by a trawling fleet targeting the Argentine red shrimp Pleoticus muelleri (Spence Bate, 1888) between 2003 and 2014. The authors coupled seven fish trophic traits to a reconstructed fish assemblage for the study area and by-catch and evaluated changes in fish species richness and four complementary functional diversity measures (functional richness, redundancy, dispersion and community trait values) along with fishing intensity, temporal use, latitudinal location and depth of fishing grounds, and vessel length. Resident fishes larger than 30 cm in length, with depressed and fusiform bodies, intermediate to high trophic levels, and feeding in benthic, demersal and midwater areas were vulnerable to by-catch. In addition, fish assemblages exhibited a low functional trait redundancy, likely related to species influxes in a biogeographic ecotone with tropicalisation signs. Significant increases in fish trait richness and dispersion poleward and deep suggested new functional roles in these grounds, matching trends in community body size, reproductive load, maximum depth and trophic level. Finally, a temporal increase in fish species and functional trait removal in fishing grounds led to trait homogenisation since 2003. The authors identified that tipping points in temperate fish functional trait diversity showed the importance of trait-based approaches within ecosystem-based fisheries management.     

When Does this Fish Spawn? Fishermen’s Local Knowledge of Migration and Reproduction of Brazilian Coastal Fishes

Fishermen’s local knowledge of fishing resources may be an important source of information to improve artisanal tropical fisheries management, such as those found in Brazil, where most data on fish biology is lacking. We aim to study the local ecological knowledge that Brazilian coastal fishers have about reproductive aspects (season, places and migration) of 13 coastal fish species of commercial importance. We selected fishermen with more than 30 years of fishing practice and we interviewed a total of 67 fishermen: 29 from the southeastern coast, from the communities of Puruba, Almada, Picinguaba and Bertioga, and 38 from the northeastern coast, from the communities of Valença, Arembepe and Porto Sauípe. In the interviews, we used standardized questionnaires and showed photos of fish species. Our results indicate some general patterns in fishes’ reproduction according to fishermen knowledge: fish species spawn in open ocean, near reefs or in coastal rivers (estuaries); some fishes reproduce during the summer and others in winter, while some have more defined spawning months. The main fish migratory patterns mentioned by interviewees were: long migrations along the coast, usually in the South to North direction, short migrations among reefs, fishes that do not migrate, migrations between the shore and open ocean and migrations between the sea and coastal rivers. Fishermen’s knowledge differed among fish species: most fishermen did not know spawning places or seasons of large pelagic fishes, which raised concerns of their possible depletion. We compared such ethnoichthyological information with available scientific data, indicating promising insights about reproduction and migration of Brazilian coastal fishes. Data gathered from local fishermen may provide inexpensive and prompt information, potentially applicable to fisheries management. Our approach might be useful to several other small-scale fisheries, especially the tropical ones, where there is a high diversity of target species and a low biological and ecological knowledge about these species.     

Within Flood Season Variation in Fruit Consumption and Seed Dispersal by Two Characin Fishes of the Amazon

Many Amazon River fishes consume fruits and seeds from floodplain forests during the annual flood season, potentially serving as important seed dispersers and predators. Using a participatory approach, this study investigated how within-season variation in flood level relates to fruit consumption and seed dispersal by two important frugivorous fish, Colossoma macropomum and Piaractus brachypomus , in two Lower Amazon River fishing communities in Brazil. Diets of both fish species were comprised of 78–98 percent fruits, largely dominated by a few species. Diets included fruits of 27 woody angiosperms and four herbaceous species from 26 families, indicating the importance of forest and Montrichardia arborescens habitat during peak flood. A correspondence between peak fruit species richness and peak flood level was observed in one of two communities, which may reflect higher forest diversity and/or differences in selection of fishing habitat. Both fishes are seed dispersers and predators, the relative role of which did not vary by flood level, seed size, or fish size, but may vary with seed hardness. Interspecific differences in diet volume and intact seeds suggest P. brachypomus are more effective seed dispersers than C. macropomum . Overall, the spatial and temporal variation in fruit species composition and richness demonstrate plasticity in fruit consumption in relation to flood level and locally available fruits. While such diets are adaptive to the dynamic changes of Amazon floodplain habitats, the high consumption of forest fruits and seeds from mid- and late-successional species suggests that floodplain forest degradation could disrupt seed dispersal and threaten local and regional fisheries.     

Movements of undersized spotted grunter (<Emphasis Type="Italic">Pomadasys commersonnii</Emphasis>) in the Great Fish Estuary,South Africa: implications for fisheries management

The purpose of this study was to test the hypothesis that an estuarine species as the spotted grunter Pomadasys commersonnii is evenly distributed within the estuary and uniformly exploited by different groups of fishers. This was done by investigating the movements and area use of spotted grunter in relation to the fisheries. The position of 20 acoustically tagged fish was recorded during 36 days in February and March 2003, by manual tracking and automated data logging receivers. Information on the fisheries in the estuary was collected through visual registration of fishing effort and interviews. The spotted grunter moved on average 1.0 km (SD ± 0.7) between positional fixes. Most of the fish were positioned in the lower part of the 12 km long estuary, as 70% of the positional fixes were within the first 3 km, and 89% within the first 6 km. Approximately half (49%) of all the fixes were between 1.0 and 1.5 km from the estuary mouth. The spotted grunter used on average 4.9 km (SD ± 4.9) of the length of the estuary, and there was no significant relationship between the length of the estuary used and the body length of the fish (26–39 cm TL). Subsistence fishers accounted for 73% of fishing lines in the water, while recreational fishers accounted for the rest. Ninety-three percent of the lines were recorded within the first 6 km from the estuary mouth, of which 80% were recorded within the first 3 km. Almost 1/3 of the fishing effort was recorded between 1.0 and 1.5 km from the mouth. The hypothesis that the estuarine dependent species spotted grunter was evenly distributed within the estuary was rejected. However, there was a significant relationship between the distribution of the fishing effort of the subsistence fishers and the fish, indicating that the spotted grunter was uniformly exploited within the estuary by this group of fishers. In contrast, there was no relationship between the distribution of fish and recreational anglers.     

Molecular differentiation of species of the genus Zungaro (Siluriformes, Pimelodidae) from the Amazon and Paraná-Paraguay River basins in Brazil

Fish species of the Zungaro genus (Siluriformes, Pimelodidae) are amongst the largest migratory fish in Latin America and have considerable economic importance for commercial fishing in Brazil. However, natural populations of this large catfish are experiencing a severe decline. There are significant taxonomical inconsistencies for this fish. Two geographically separated species of the fish were initially described, one endemic in the Amazon and another in the Paraná-Paraguay River basins. A taxonomic review had recently proposed that there is only one Zungaro species in Brazil, based on morphological data. We made a molecular study of Zungaro populations in an attempt to solve taxonomical inconsistencies and to analyze genetic diversity in natural populations of this genus. We analyzed two regions of the mitochondrial DNA (the control region and the ATPase 6 gene region) of individuals sampled from the Paraná-Paraguay River and Amazon River basins. Analyses based on p-distances and maximum likelihood phylogenetic models showed a genetic difference between populations corresponding to different species. Genetic differentiation between Zungaro populations was at the same level as that observed between other Siluriformes species, using the same DNA sequences. We conclude that Zungaro species of the Paraná-Paraguay River basin do not belong to the same species found in the Amazon basin. This finding has a significant implication for conservation of this fish, given that populations are disappearing at a high rate in the Paraná-Paraguay River basin, mainly due to impoundments.     

Gear selectivity of functional traits in coral reef fisheries in Brazil

Small-scale reef fisheries are important commercial and subsistence activities that support the livelihoods of millions of people in tropical regions. Tropical marine fisheries typically target a diversity of species caught with a matching diversity of fishing gears and practices. Here, we explored how multiple fishing gears select for distinct functional traits of fish assemblages inside a large multiple use marine environmental protected area off northeastern Brazil. In 1833 landing interviews with local fishers, we identified 101 species, which were categorized according to six traits: body size, schooling behavior, mobility, position in the water column, diet and period of activity. Our research is the first to explore the broad patterns of gear selectivity with regards to fish functional traits for different habitat types. While gears used in reef habitats were highly selective of sedentary and benthic species that form schools with few individuals, gears used in coastal lagoons were selective of highly mobile pelagic species that form large schools. We found a low competitive interaction between different gear types, meaning there was a low overlap in trait selectivity between fishing gears. We also found direct associations between gears and fish functional traits: hooks and line targeted species that exhibit limited mobility capabilities, making these species more vulnerable to local levels of fishing effort. In contrast, nets and fish corrals targeted mobile species that exhibited a greater diversity of functional traits. Some of our results contrasted with the current literature on the topic, with differences highlighting the need for more research to clarify global patterns of trait selectivity by gear type. Our results have implications for fisheries management in northeastern Brazil: gear bans and effort caps are commonly used management measures that can foster fisheries sustainability by minimizing impacts to fish assemblage functions.

     

Genetic variation among populations of the Antarctic toothfish: evolutionary insights and implications for conservation

Commercial fishing is having an increasingly negative impact on marine biodiversity, with over 70% of the world's fish stocks being fully exploited and, in many cases, overexploited. On top of this, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has granted commercial fishing permits in the most remote marine environment on earth, the high-latitude Southern Ocean. The primary target of these new commercial fishing ventures is the large pelagic piscivorous predator, the Antarctic toothfish (Dissostichus mawsoni). Unfortunately, little information is available on the demography, genetics, or life history of this large fish. Without such information we have little idea as to the effects of commercial fishing on the population structure and survival of this species. In this study, we focus on patterns of genetic diversity within and between geographically disparate populations of the Antarctic toothfish, using randomly amplified polymorphic DNA markers. Results of our study showed high levels of genetic similarity within and between populations. Despite high levels of genetic similarity, genetic analyses detected significant population structure, including fixed differences among populations, a significant fixation index (Fst) and between-population differentiation via a Mantel test. From a conservation perspective, low levels of genetic diversity may be indicative of relatively small populations that would not be able to withstand heavy commercial fishing pressures. Given that there is evidence for significant genetic structure, it will be important to manage these fisheries in a manner that will help prevent the loss of unique genetic variation from regional overfishing.     

Length–weight relationships for selected fish species of Rio Trombetas Biological Reserve: a reference study for the Amazonian basin

Length–weight relationships (LWR) are presented for 27 freshwater fish species representing 11 families captured in the Trombetas River, a clearwater left margin tributary of the Amazon River. The allometry coefficient (b) of the LWR (W = aTL^b) ranged from 2.51 to 3.49, with a median value of 3.00. This study represents the first reference on LWR for 23 species and new records of maximum lengths for 15 species.     

Genetic and morphometric evidence that the jacks (Carangidae) fished off the coast of Rio de Janeiro (Brazil) comprise four different species

Individuals of jacks that were captured off the Rio de Janeiro coast were characterized using multivariate morphometrics and allozymes molecular markers. The main objectives were to determine the number of fish captured and their species. Classical taxonomic classification and multivariate morphometry indicated the existence of three species in the landings from Rio de Janeiro State (Caranx crysos, Carangoides bartholomaei and Caranx latus). The results of the genetic analyses performed were consistent with these results. However, Bayesian analysis revealed the possible presence of a fourth species, which could not be discriminated by classical taxonomy. Caranx crysos possibly comprises two different species. Other population indexes, such as unique alleles, degree of structuring and genetic identity, also pointed to different species. Therefore, based on evidences from classical taxonomy, geometric morphometric analyses together with genetic data from allozymes molecular markers it is possible to support that at least four different Carangidae species are present in fish landings from Niterói, Rio de Janeiro State, Brazil, whereas fish capture records for the same location have recorded only two species. These results are important for not only developing fisheries management strategies but also providing general information regarding the ecology and evolution of the genus.     

Thyroid hormone levels in Atlantic salmon (Salmo salar) during the return migration from the ocean to spawn

Serum thyroid hormone levels were determined in adult Atlantic salmon ( Salmo salar ) of both sexes caught in the ocean and at a sequence of locations on their return migration to spawn. Tri-iodothyronine (T₃) levels were greatest in fish caught in coastal or estuarine waters or in a river near head-of-tide. T₃ levels were lower in fish caught in rivers throughout the angling season and lowest in those captured entering a tributary near spawning. Thyroxine (T₄) levels were lowest in immature fish captured in the ocean in winter but raised in fish captured in spring; many of the latter group showed endocrine evidence of their becoming sexually mature. T₄ levels were greatest in fish captured in coastal waters and progressively lower in fish captured in an estuary, near head-of-tide and in rivers. T₄ levels in fish captured at tributary entry near spawning exceeded those in fish caught in rivers earlier in the year. In general, these data support the hypothesis that motor activity level in migrant fish is a determinant of thyroid status.     

Recruitment of migratory Characiforms in the different wetland habitats of Central Amazonia: Subsidies for sustainable fisheries management

By promoting the biological recruitment of relevant natural resources, wetlands offer a major ecosystem service. This study investigates the importance of wetland habitats of the central Amazon basin as sites for spawning and/or initial development of seven of the most important commercial Characiforms fish species. In order to confirm this importance, samples of the eggs, larvae, and juveniles of these fish species were collected during the four seasonal phases of the hydrological cycles of 2010 and 2011, in different aquatic environments of the wetland ecosystem in the central Amazon. The results confirmed that the flooding phase is the most important for the spawning of these species, and that they preferred to use the marginal areas of the central Amazon as spawning grounds. The larvae of these species colonize the confluence zone of the rivers and the mouths of the floodplain channels, principally during the initial stages (pre-flexion) of their ontogenetic development. The channels that connect the lakes to the rivers are the main dispersal route for the larvae, especially those in advanced stages of development (flexion/post-flexion), towards the internal of the wetland habitats, such as the lakes and large mattresses of floating vegetation. The different wetland habitats of this region provide an extremely important ecosystem service, playing a critical role in the recruitment of commercially-valuable fish species, and thus require adequate protection and management to ensure the continuity of fisheries and natural stocks.     

Length–Weight relationships of 23 fish species from floodplain ecosystems of the Andean Amazon piedmont,Peru

Length–weight relationships (LWRs) for 23 freshwater fish species from the Andean Amazon piedmont in Peru are presented in this study. Fishes were captured between 2009 and 2010 on lagoons from three basins; Amazonas (Ampiyacu and Apayacu) and Ucayali (Pachitea) using gillnets. In this study, new LWRs are reported for 20 species of 23 species analyzed. The study provides new information on less‐studied species and can serve as a basis for management of fisheries and conservation of this area.     

Isolation by distance and Pleistocene expansion of the lowland populations of the white piranha Serrasalmus rhombeus

The genetic variability and distribution of Amazonian fish species have likely been influenced by major disturbance events in recent geological times. Alternatively, the great diversity of aquatic habitat in the Amazon is likely to shape ongoing gene flow and genetic diversity. In this context, complex patterns of genetic structure originating from a joint influence of historical and contemporary gene flow are to be expected. We explored the relative influence of Pleistocene climatic fluctuations and current water chemistry on the genetic structure of a piranha, Serrasalmus rhombeus, in the Upper Amazon by the simultaneous analysis of intron length polymorphism and mitochondrial DNA sequences. The Madeira river is well suited for that purpose as it is characterized by a great diversity of water types, the presence of one of the largest floodplain of the Amazon and the potential occurrence of two Pleistocene refuges. We found evidence of genetic structure even at a small geographical scale (less than 10 km), indicating that the floodplain is not a homogenizing factor promoting interdrainage dispersal in S. rhombeus. Likewise, the hierarchical genetic structure inferred was correlated to geographical distance instead of habitat characteristic. Our results also support the hypothesis that the area underwent population expansion during the last 800 000 years. In addition, a higher level of genetic diversity was found in the samples from the putative Aripuanã refuge. The present findings suggest that Pleistocene refuges contributed significantly to the colonization of the lowlands in the Upper Amazon valley during the Pleistocene.     

Ecological, environmental and socioeconomic aspects of the Lake Victoria's introduced Nile perch fishery in relation to the native fisheries and the species culture potential: lessons to learn

Inland fishery ecosystems in Africa are characterized by patterns of overexploitation, environmental degradation and exotic species introductions. Ecological complexity and diversity of aquatic habitats dictate that fishes in general are not evenly distributed in a water body. However, fisheries management regimes tend to ignore this basic principle, assume generalized conditions in a water body, and focus more on ‘desired’ objectives such as maximizing catch. The result is to disregard fish habitat boundaries and anthropogenic influences from the catchment that influence fish production. Overexploitation and environmental degradation disrupt sustainable socioeconomic benefits from the fisheries, create uncertainty among investors, but leave some managers calling for more information with the expectation that the fisheries will recover with time. Open access to the fisheries and full control of fishing effort remain challenges for managers. Exotic species introductions and fish farming can increase production, but such interventions require firm commitment to sound ecological principles and strict enforcement of recommended conservation and co‐management measures in capture fisheries. The general tendency to downplay fishing effort issues, other ecosystem values and functions or rely on temperate fisheries models until a new cycle of overexploitation emerges, characterizes many management patterns in inland fisheries. Aquaculture is not an option to challenges in capture fisheries management. Aquaculture should be developed to increase fish production but even this practice may have negative environmental impacts depending on practice and scale. Decades of information on Lake Victoria fisheries trends and aquaculture development did not stop the collapse of native fisheries. The successfully introduced Nile perch (Lates niloticus) has shown signs of overexploitation and aquaculture has again been considered as the option. By reviewing significant trends associated with Nile perch and its feasibility in aquaculture this paper uses Lake Victoria to illustrate ‘special interest management’ targeting selected species of fish rather than the fisheries.     

Changes in fish bycatch during the shrimp fishing season along the eastern coast of the mouth of the Gulf of California

One of the main concerns of shrimp fisheries is the associated impact on ecosystem biodiversity, particularly on fish assemblages that are poorly characterized yet likely very relevant to the health of the ecosystem. The continental shelf along the eastern coast of the mouth of the Gulf of California is a region of high biodiversity that harbors highly productive fisheries. This study aimed to analyze the changes in the soft bottom fish assemblages caught as bycatch in the shrimp fishery located in this region. Sampling was conducted with commercial trawls at 16 fixed stations during the 2006–2007 shrimp‐fishing season. A total of 103 fish species from 80 genera and 47 families were collected. The ecological and taxonomic diversity as well as the composition and abundance of the fish community caught as bycatch in the shrimp trawl fishery were found to be significantly different in the autumn and winter. Ordination and similarity analyses also revealed differing patterns. Species abundance was strongly associated with sea bottom temperature, depth and latitude. The effects of these abiotic variables on the observed diversity patterns and the possible influences of the fishery are discussed.     

Status of research on Yangtze fish biology and fisheries

The Yangtze is the largest river in China and the third largest river in the world. Being pregnant with plentiful fish resources, it is not only the representative of the areas with biological diversity, but also a cradle of freshwater fisheries in China. In the Yangtze, at present, the fishery resources are seriously depleted; the fishery yield by fishing is significantly reduced; significant changes have occurred on the structure of fish community, with decrease in migratory fish species, reduction in the quantity of the populations of rare, peculiar and economically important fish species and increase in the number of exotic fish species, and severe trend in fish stunting. Habitat fragmentation and shrinkage, resources overexploitation, water pollution and invasion of exotic species are the main causes for threatening fish stocks in the Yangtze River. Since 1950’s, a lot of scientific researches have been conducted on biology of fishes from the Yangtze River and its fisheries to provide scientific basis for their protection. In recent years, measures such as closed spring, fish reserves, artificial enhancement & release, ecological rehabilitation, fishery management and international cooperation have played important roles. Nevertheless, researches on fishes from the Yangtze cannot adequately meet the demand for their protection. Especially, those in the aspects of population ecology of Yangtze fishes, species endangerment mechanism, ecological effects of large hydraulic projects and protection strategy are not deep enough. It is recommended that scientific researches should be conducted in comprehensive survey of Yangtze fish resources, fish endangerment mechanism, techniques in artificial enhancement and release of key species, risk assessment of exotic species, ecological rehabilitation of major fisheries functional zones, etc.     

Co-management and Spatial Features Contribute to Secure Fish Abundance and Fishing Yields in Tropical Floodplain Lakes

Empirical data are needed to show the efficacy of co-management, which is regarded as a promising approach to achieve conservation goals. In this study, we addressed the potential influence of fisheries co-management to increase fish abundance and fishing yields in the lower Tocantins River Basin (Brazilian Amazon), downstream from a large dam. We analyzed 590 fish landings (6.7 t of fish) from five fishing villages and 48 fish samples obtained using gillnets (10,378 fish from 101 species) in 12 floodplain lakes in four regions: two with incipient co-management and two unmanaged. The fish species richness did not differ among the regions, but the lakes in the regions that were co-managed had higher fish abundance (biomass and number of individuals) and a higher mean proportion of fish reproducing during the high water season. Fishers had higher catches per unit of effort in the co-managed regions than fishers in the non-managed regions. These results were also influenced by geographic factors (distance and accessibility of lakes), as fish biomass was higher in lakes that were distant from the main river and from the main city in the region. Managers should thus consider strategic selection of the geographic locations of managed sites, even in remote areas. However, the fish biomass sampled in lakes was more related to region than to the lakes’ geographical location. Therefore, co-management has at least partially contributed to increased fish abundance and fishing yields in the studied region, through the protection of an important fish habitat (lakes). We provide empirical evidence that co-management can contribute to the maintenance of fish abundance, sustainability of fisheries, and food security in large tropical rivers impacted by damming.