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The association of morphological divergence with ecological segregation among closely related species could be considered as a signal of divergent selection in ecological speciation processes. Environmental signals such as diet can trigger phenotypic evolution, making polymorphic species valuable systems for studying the evolution of trophic‐related traits. The main goal of this study was to analyze the association between morphological differences in trophic‐related traits and ecological divergence in two sympatric species, Astyanax aeneus and A. caballeroi, inhabiting Lake Catemaco, Mexico. The trophic differences of a total of 70 individuals (35 A. aeneus and 35 A. caballeroi) were examined using stable isotopes and gut content analysis; a subset of the sample was used to characterize six trophic and six ecomorphological variables. In our results, we recovered significant differences between both species in the values of stable isotopes, with higher values of δ15N for A. caballeroi than for A. aeneus. Gut content results were consistent with the stable isotope data, with a higher proportion of invertebrates in A. caballeroi (a consumption of invertebrates ten times higher than that of A. aeneus, which in turn consumed three times more vegetal material than A. caballeroi). Finally, we found significant relationship between ecomorphology and stable isotopes (r = .24, p < .01), hence, head length, preorbital length, eye diameter, and δ15N were all positively correlated; these characteristics correspond to A. caballeroi. While longer gut and gill rakers, deeper bodies, and vegetal material consumption were positively correlated and corresponded to A. aeneus. Our results are consistent with the hypothesis that morphological divergence in trophic‐related traits could be associated with niche partitioning, allowing the coexistence of closely related species and reducing interspecific competition. We assess the association between ecomorphological differences and trophic habits in two sympatric species. Both stable isotope signals (δ15N and δ13C) showed a strong correlation with the trophic morphology, supporting the hypothesis that morphological disparity in trophic‐related characters could be associated with niche partitioning.

The role of interspecific interactions in structuring low‐diversity helminth communities is a controversial topic in parasite ecology research. Most parasitic communities of fish are species‐poor; thus, interspecific interactions are believed to be unimportant in structuring these communities. We explored the factors that might contribute to the richness and coexistence of helminth parasites of a poeciliid fish in a neotropical river. Repeatability of community structure was examined in parasitic communities among 11 populations of twospot livebearer Pseudoxiphophorus bimaculatus in the La Antigua River basin, Veracruz, Mexico. We examined the species saturation of parasitic communities and explored the patterns of species co‐occurrence. We also quantified the associations between parasitic species pairs and analyzed the correlations between helminth species abundance to look for repeated patterns among the study populations. Our results suggest that interspecific competition could occur in species‐poor communities, aggregation plays a role in determining local richness, and intraspecific aggregation allows the coexistence of species by reducing the overall intensity of interspecific competition. The results of this work suggest that interspecific competition can occur in species‐poor, nonsaturated communities among specialist dominant species. Our analyses suggest also that aggregation is an important factor to determine local richness of parasites in fish populations and that intraspecific aggregation allows the coexistence of species in the same host population by means of reducing the overall intensity of competition.

Rainbow smelt (Osmerus mordax) have invaded many North American lakes, often resulting in the extirpation of native fish populations. Yet, their invasion is incipient and provides the rationale for identifying ecosystems likely to be invaded and where management and prevention efforts should be focused. To predict smelt presence and absence, we constructed a classification-tree model based on habitat data from 354 lakes in the native range for smelt in southern Maine. Maximum lake depth, lake area, and Secchi depth (surrogate measure of lake productivity) were the most important predictors. We then used our model to identify lakes vulnerable to invasion in three regions outside the smelt's native range: northern Maine (52 of 244 lakes in the non-native range), Ontario (4447 of 8110), and Wisconsin (553 of 5164). We further identified a subset of lakes with a strong potential for impact (potential-impact lakes) based on the presence of fish species that are affected by rainbow smelt. Ninety-four percent of vulnerable lakes in the non-native range in Maine are also potential-impact lakes, as are 94% and 58% of Ontario and Wisconsin's vulnerable lakes, respectively. Our modeling approach can be applied to other invaders and regions to identify invasion-prone ecosystems, thus aiding in the management of invasive species and the efficient allocation of invasive species mitigation and prevention resources.

The biological assessment of rivers i.e., their assessment through use of aquatic assemblages, integrates the effects of multiple-stressors on these systems over time and is essential to evaluate ecosystem condition and establish recovery measures. It has been undertaken in many countries since the 1990s, but not globally. And where national or multi-national monitoring networks have gathered large amounts of data, the poor water body classifications have not necessarily resulted in the rehabilitation of rivers. Thus, here we aimed to identify major gaps in the biological assessment and rehabilitation of rivers worldwide by focusing on the best examples in Asia, Europe, Oceania, and North, Central, and South America. Our study showed that it is not possible so far to draw a world map of the ecological quality of rivers. Biological assessment of rivers and streams is only implemented officially nation-wide and regularly in the European Union, Japan, Republic of Korea, South Africa, and the USA. In Australia, Canada, China, New Zealand, and Singapore it has been implemented officially at the state/province level (in some cases using common protocols) or in major catchments or even only once at the national level to define reference conditions (Australia). In other cases, biological monitoring is driven by a specific problem, impact assessments, water licenses, or the need to rehabilitate a river or a river section (as in Brazil, South Korea, China, Canada, Japan, Australia). In some countries monitoring programs have only been explored by research teams mostly at the catchment or local level (e.g., Brazil, Mexico, Chile, China, India, Malaysia, Thailand, Vietnam) or implemented by citizen science groups (e.g., Southern Africa, Gambia, East Africa, Australia, Brazil, Canada). The existing large-extent assessments show a striking loss of biodiversity in the last 2–3 decades in Japanese and New Zealand rivers (e.g., 42% and 70% of fish species threatened or endangered, respectively). A poor condition (below Good condition) exists in 25% of South Korean rivers, half of the European water bodies, and 44% of USA rivers, while in Australia 30% of the reaches sampled were significantly impaired in 2006. Regarding river rehabilitation, the greatest implementation has occurred in North America, Australia, Northern Europe, Japan, Singapore, and the Republic of Korea. Most rehabilitation measures have been related to improving water quality and river connectivity for fish or the improvement of riparian vegetation. The limited extent of most rehabilitation measures (i.e., not considering the entire catchment) often constrains the improvement of biological condition. Yet, many rehabilitation projects also lack pre-and/or post-monitoring of ecological condition, which prevents assessing the success and shortcomings of the recovery measures. Economic constraints are the most cited limitation for implementing monitoring programs and rehabilitation actions, followed by technical limitations, limited knowledge of the fauna and flora and their life-history traits (especially in Africa, South America and Mexico), and poor awareness by decision-makers. On the other hand, citizen involvement is recognized as key to the success and sustainability of rehabilitation projects. Thus, establishing rehabilitation needs, defining clear goals, tracking progress towards achieving them, and involving local populations and stakeholders are key recommendations for rehabilitation projects (Table 1). Large-extent and long-term monitoring programs are also essential to provide a realistic overview of the condition of rivers worldwide. Soon, the use of DNA biological samples and eDNA to investigate aquatic diversity could contribute to reducing costs and thus increase monitoring efforts and a more complete assessment of biodiversity. Finally, we propose developing transcontinental teams to elaborate and improve technical guidelines for implementing biological monitoring programs and river rehabilitation and establishing common Water 2021, 13, 371 3 of 45 financial and technical frameworks for managing international catchments. We also recommend providing such expert teams through the United Nations Environment Program to aid the extension of biomonitoring, bioassessment, and river rehabilitation knowledge globally.

An updated checklist of Mexican non-biting midges (Chironomidae) is presented. A total of 110 species of Chironomidae are known for Mexico: 52 species in 25 genera belong to the subfamily Chironominae, 30 species in 13 genera to Orthocladiinae, 21 species in nine genera to Tanypodinae, five species in two genera to Telmatogetoninae, and two species in one genus to Diamesinae. In addition, 41 genera without identified species are listed. The highest number of species (29) is recorded from the state of Campeche, while 19 species have been found in Veracruz and 15 in Nuevo León. Few or no records exist for states in Central and Northern Mexico, or those on the Pacific coast. The type localities for 34 species are in Mexico; of these, 27 species (25% of the total number of species recorded in the country) are endemic. Twenty-nine species recorded in Mexico have a Neotropical distribution, 15 a Nearctic distribution, and 39 species are distributed in both the Neotropical and Nearctic regions or more widely. It has been suggested that as many as 1000 species might occur in Mexico; so only a little more than 10% of the expected diversity has so far been recorded.

Globally, our knowledge on lake fisheries is still limited despite their importance to food security and livelihoods. Here we show that fish catches can respond either positively or negatively to climate and land-use changes, by analyzing time-series data (1970–2014) for 31 lakes across five continents. We find that effects of a climate or land-use driver (e.g., air temperature) on lake environment could be relatively consistent in directions, but consequential changes in a lake-environmental factor (e.g., water temperature) could result in either increases or decreases in fish catch in a given lake. A subsequent correlation analysis indicates that reductions in fish catch was less likely to occur in response to potential climate and land-use changes if a lake is located in a region with greater access to clean water. This finding suggests that adequate investments for water-quality protection and water-use efficiency can provide additional benefits to lake fisheries and food security. Lake fisheries are vulnerable to environmental changes. Here, Kao et al. develop a Bayesian networks model to analyze time-series data from 31 major fisheries lake across five continents, showing that fish catches can respond either positively or negatively to climate and land-use changes.

Fish assemblages of lakes from central México have been altered as a result of water overexploitation, pollution, habitat ragmentation, and introduction of exotic species. Patterns and the extent of change in most of these systems are poorly documented. This paper presents a long-term study of changes in the fish fauna of Lago de Pátzcuaro (State of Michoacán, México). Long-term information (years 1900-2010) of fish communities was used to explore trends in the composition of the fish community and their ecological attributes. Trends across time for each fish guild were evaluated through a multivariate analysis of variance. Native species dominated total species richness over the entire study period, but exotic fish comprised 46% of the community in the 2010s. During the last 110 years, there has been a decline in the number of carnivore species and an increase of omnivore species in the Lago de Pátzcuaro fish community. Sensitive species have disappeared from the lake and species tolerant to environmental degradation have increased from 13 to 61%. The data suggest that anthropic effects on the environmental condition of Lago de Pátzcuaro are associated with the loss of ecosystem elements (fish species) and ecosystem processes (species interactions). Ecological restoration and conservation programs must include information of these long term studies to be more effective in their efforts.

The discipline of sustainability science has emerged in response to concerns of natural and social scientists, policymakers, and lay people about whether the Earth can continue to support human population growth and economic prosperity. Yet, sustainability science has developed largely independently from and with little reference to key ecological principles that govern life on Earth. A macroecological perspective highlights three principles that should be integral to sustainability science: 1) physical conservation laws govern the flows of energy and materials between human systems and the environment, 2) smaller systems are connected by these flows to larger systems in which they are embedded, and 3) global constraints ultimately limit flows at smaller scales. Over the past few decades, decreasing per capita rates of consumption of petroleum, phosphate, agricultural land, fresh water, fish, and wood indicate that the growing human population has surpassed the capacity of the Earth to supply enough of these essential resources to sustain even the current population and level of socioeconomic development.

Analyses of trophic structure and feeding habits of the fish community can provide information on the complex biotic and abiotic interactions in lake ecosystems. Based on stomach content and δ13C and δ15N stable isotope analyses, we conducted a comprehensive study of the diet of the fish community and its trophic structure in subtropical Lake Zacapu in central Mexico. Overall, there was good agreement between the results based on the diet and the isotope analysis. Fish diets consisted mainly of aquatic macroinvertebrates, which were abundant in the lake. Most species were secondary consumers and trophic generalists across the four sites and two seasons. The food web structure did not differ significantly between the sites or seasons. Our results suggest a low trophic position of native species having a wide spatial trophic niche and niche width. Trophic diet overlap was greater between native species (especially between species from the same family) than between non-native species. Our study provides new information on the trophic interactions in a subtropical lake, rich in endemic species and an important resource for human communities.

Inland recreational fisheries, found in lakes, rivers, and other landlocked waters, are important to livelihoods, nutrition, leisure, and other societal ecosystem services worldwide. Although recreationally-caught fish are frequently harvested and consumed by fishers, their contribution to food and nutrition has not been adequately quantified due to lack of data, poor monitoring, and under-reporting, especially in developing countries. Beyond limited global harvest estimates, few have explored species-specific harvest patterns, although this variability has implications for fisheries management and food security. Given the continued growth of the recreational fishery sector, understanding inland recreational fish harvest and consumption rates represents a critical knowledge gap. Based on a comprehensive literature search and expert knowledge review, we quantified multiple aspects of global inland recreational fisheries for 81 countries spanning ~192 species. For each country, we assembled recreational fishing participation rate and estimated species-specific harvest and consumption rate. This dataset provides a foundation for future assessments, including understanding nutritional and economic contributions of inland recreational fisheries. Measurement(s) inland recreational fisheries harvest Technology Type(s) Module 4: Literature References Sample Characteristic - Organism Osteichthyes Sample Characteristic - Environment inland waters Sample Characteristic - Location Global