Scaled body‐mass index shows how habitat quality influences the condition of four fish taxa in north‐eastern Spain and provides a novel indicator of ecosystem health

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Assessing environmental conditions of the Río Champotón (México) using diverse indices and biomarkers in the fish Astyanax aeneus (Günther, 1860)

The upper reaches of the Río Champotón in southwestern Mexico are largely unknown to science. This river is sustaining anthropogenic and natural disturbances by deforestation, substitution of natural vegetation, and agricultural non-point source pollution. Furthermore, hurricanes provoke flooding of these areas, exposing the aquatic biota to pollutants. Several approaches were used to assess the effects of environmental conditions along the freshwater portion of the Río Champotón in the native fish Astyanax aeneus and to determine the feasibility of extrapolating responses between levels of organization, and to link spatial and seasonal fish responses with water quality features. A water quality index (WQI) was employed as an indicator of environmental conditions, a set of sub-organismal biomarkers in A. aeneus (lipid peroxidation, glutathione S-transferase, ethoxyresorufin-O-deethylase and lactate dehydrogenase) was monitored to determine the integrated biomarker response (IBR), and somatic indices (individual and population-level responses; gonadosomatic, hepatosomatic, and condition factor) were characterized. Canonical correspondence analysis revealed spatial and seasonal variations in all the approaches. The dry and the wet season (April and July) exhibited low WQI scores, but decreased hardness and conductivity values as well as increased WQI values occurred during the post-hurricane season when crop fields adjacent to the riverbed were inundated. Although the WQI suggested low levels of contamination, the biomarkers did not remain static; wide fluctuations reflected fish exposure to seasonal stressors that provoked impairments in biological responses. All biomarker values were high, mainly in the post-hurricane season (November). The IBR exhibited two peaks that may be related to stress periods (April and November), with decreasing post-stress values suggesting the existence of homeostatic processes in the fish. The somatic indices reflected some seasonal and spatial differences at the population level – the gonadosomatic and hepatosomatic indices peaked in the middle of July and November, respectively – but the condition factor remained constant among sites and study periods. Future studies are needed to explore the link between the fish biomarker responses and possible causal stressors (natural or anthropogenic).     

Habitat quality of estuarine nursery grounds: Integrating non-biological indicators and multilevel biological responses in Solea senegalensis

Estuaries are highly valuable ecosystems that provide various goods and services to society, such as food provision and supporting nursery habitats for various aquatic species. Estuarine habitat quality assessment is thus critical in managing both ecological and economic value. In this work, various biological and non-biological indicators of habitat quality in estuarine nursery areas were determined, encompassing local environmental conditions, chemical contamination, anthropogenic pressures, juvenile Solea senegalensis condition, biomarkers response to contamination and juvenile density. The various indicators provided an integrated view on habitat quality and their responses were broadly concordant. Nursery quality assessment based on anthropogenic pressure indicators and fish biomarker responses were very similar, signaling nursery areas with higher anthropogenic pressure in Tejo and Ria de Aveiro estuaries. Yet, favorable environmental conditions across all sites could have contributed to lessen the potential hazardous biological effects of exposure to anthropogenic stressors, resulting in soles’ fairly good condition and generally high juvenile density. Nevertheless, a mismatch between high juvenile density and high estuarine contribution to adult coastal populations was observed in areas with higher anthropogenic pressures. Although a causal relationship cannot be established, the results emphasize the need to fully understand how the estuarine period spent in estuaries and local processes determine the quantity and quality of juveniles exported to marine adult populations, which is critical to achieve the full potential of the fish production service of estuaries and coastal stock replenishment.     

Genetic effects of living in a highly polluted environment: the case of the silverside Basilichthys microlepidotus (Jenyns) (Teleostei: atherinopsidae) in the Maipo River basin,central Chile

Freshwater systems are one of the environments most impacted by human activity, with pollution being a highly important factor. In Chile, several rivers exhibit varied levels of pollution, one of which is the Maipo River basin where the city of Santiago is located. The silverside Basilichthys microlepidotus (Jenyns) is an endemic fish species that inhabits this basin, thus we hypothesized that pollution has affected gene diversity and migration in populations of B. microlepidotus from the Maipo River basin. The aim of this study was to identify the population structure of B. microlepidotus in this basin and to determine if the populations of the silverside inhabiting polluted sites present differences in gene diversity and gene flow compared to populations inhabiting non-polluted areas. Using the variability of eight microsatellites, five populations of silverside were detected; three inhabiting non-polluted sites and two inhabiting polluted sites. From this, it was inferred that B. microlepidotus has been able to tolerate pollution in the Maipo River basin. No differences in gene diversity or migration were detected between polluted and non-polluted sites but comparison with historical estimation revealed an increase in the current migration rate when all the data from the basin were compared. A reduction in current effective population size was also observed when compared to historical values, and this is probably due to river degradation. Despite the disappearance of other fish species recorded at this basin, our results suggest that B. microepidotus is tolerant to pollution, thus indicating that native species respond differently to this environmental factor.     

Putting pharmaceuticals into the wider context of challenges to fish populations in rivers

The natural range of fish species in our rivers is related to flow, elevation, temperature, local habitat and connectivity. For over 2000 years, humans have altered to varying degrees the river habitat. In the past 200 years, we added to the environmental disruption by discharging poorly treated sewage, nutrients and industrial waste into our rivers. For many rivers, the low point arrived during the period of 1950s–1970s, when rapid economic development overrode environmental concerns and dissolved oxygen concentrations dropped to zero. In these more enlightened times, gross river pollution is a thing of the past in the Developed World. However, persistent legacy chemical contaminants can be found in fish long after their discharge ceased. Changes in habitat quality and morphology caused and continue to cause the disappearance of fish species. The range of fish stressors has now increased as temperatures rise, and non-native fish introductions bring new diseases. The threat from pharmaceuticals to fish populations remains hypothetical, and no studies have yet linked change in fish populations to exposure.     

Effects of fish farm effluents on egg-to-fry development and survival of brown trout in artificial redds

Egg-to-fry development and survival of brown trout Salmo trutta were compared in two rivers of the Pyrenean piedmont, the Nive d'Arnéguy, with few human activities, and the Nive des Aldudes, with many anthropogenic activities including 11 fish farms and two sewage treatment plants (STPs). Survival was estimated between spawning (early December) and emergence time (early March) by means of capsules, 7 cm³ in volume, filled with green eggs then inserted into the gravel of artificial redds at spawning sites. In the Nive des Aldudes, three sets of conditions were studied: a fish farm near the springs, a fish farm and an STP in a village, and a series of fish farms and an STP in a village. In each situation, two artificial redds were created upstream and two others downstream from the fish farms. In the Nive d'Arnéguy, four sites were equipped: each of the two downstream sites with two artificial redds, and the two upstream sites with one redd. Substratum characteristics (proportion of fine particles) and the quality of surface and interstitial water (oxygen content, ammonia and nitrite nitrogen) were periodically measured. There was no redd substratum difference between sites upstream and downstream of fish farms. Survival to fry emergence was higher in the Nive d'Arnéguy (63·5%) than in the Nive des Aldudes (47·7%). In this latter river, the nitrogen released from the STPs was 0·5% that from fish farms. Fish farming impaired survival close to fish farm effluents (31·6%), as compared to survival upstream (63·6%), and induced a development delay during the yolk-sac fry stage. These differences were mainly linked to a drop in the dissolved oxygen content in interstitial water induced by the nitrogen flow in surface and interstitial waters.     

Population Substructuring in a Migratory Freshwater Fish Prochilodus argenteus (Characiformes, Prochilodontidae) from the São Francisco River

The construction of hydroelectric dams, pollution of rivers and other environmental changes are responsible for the disappearance of many natural fish stocks. The purpose of this work was to analyze the fish Prochilodus argenteus inhabiting the region of the Três Marias dam in the São Francisco River (Brazil) collected in two sites having distinct environmental characteristics. Three novel homologous and one known cross-specific microsatellites were used to assess genetic variation within and between the two collection sites (namely A and B) in order to confirm the occurrence of population substructuring previously suggested using RAPD markers. A higher number of exclusive alleles and a greater genetic variability in region B strongly reinforce the co-existence of different reproductive units in this area. F _ST estimates showed a significant population differentiation between the two sites, indicating the possible existence of distinct gene pools. Considering the economic importance of this fishery resource in the São Francisco River, these findings could provide very important information for fisheries management, aquaculture and conservation of the stocks of this species.     

Effects of pollution on macroinvertebrates and water quality bio-assessment

Many large rivers in China have an inflow of contaminated water. Water pollution caused by urban sewage and agriculture, and occasionally pollution events from industries have become a significant stress on aquatic ecology. Pollution affects the biodiversity of the aquatic community and the species composition changes from natural species to tolerant species. The species composition of aquatic animals may reflect water pollution level. Extremely non-uniform distributions of functional feeding groups occurred as a result of high nutrient levels. A combination of chemical and biological methods constitutes the best approach for biological monitoring studies that measure water quality. Macroinvertebrates were used as bio-assessment indicator to determine the environmental quality of given water body. In this study, samples of water and macroinvertebrates were taken from several dozen sites in 14 rivers in China with different pollution levels, including the Yangtze, East, Weihe, Songhua, Yongding, and Panlong rivers. Macroinvertebrates were identified to genus or family level. Water samples were classified into different water quality grades according to the concentration of different substances. Five biological indices: taxa richness (S), density (D), total BMWQ score (t-BMWQ), average BMWQ score (a-BMWQ), and the family biotic index (FBI) were used for biological assessment of water quality. Analyzing macroinvertebrates’ occurrence in different water quality levels, taxa-specific indicators, which are defined as the taxa of macroinvertebrates that live in a certain water quality level but do not exist in other water quality levels were proposed for water quality bio-assessment. Leptophlebiidae, Siphlonuridae, Arctopsychidae, Perlidae, and Antocha sp. are the taxa-specific indicators for very good or good water quality; Chironomidae, Lymnaeidae, Tubifex sp., Limnodrilus sp., Limnoperna lacustris, Corbicula sp., Macrobrachium sp., Planorbidae, Glossiphoniidae, and Branchiura sp. are the taxa-specific indicators for very poor water quality; and Psychomyiidae and Hydroptilidae are the taxa-specific indicators for moderate water quality.     

The combined effects of treated sewage discharge and land use on rivers

Freshwater ecosystems are increasingly threatened by multiple anthropogenic stressors. Release of treated sewage effluent and pollution from agricultural or urban sources can independently reduce water quality with implications for ecological communities. However, our knowledge of the combined effects of these stressors is limited. We performed a field study to quantify the combined effect of treated sewage discharge and land use on nutrient concentrations, sewage fungus presence and communities of macroinvertebrates and benthic algae. Over three seasons in four rivers we found that a model which included an interaction between sewage pollution and time of the year (i.e. months) was the best predictor of nutrient concentrations and the abundance of algae and sewage fungus. Both macroinvertebrate and algae communities shifted downstream of sewage input. Specifically, more tolerant groups, such as cyanobacteria and oligochaetes, were more abundant. The EPT (Ephemeroptera, Plecoptera and Tricoptera) water quality score was best explained by an interaction between month and agriculture in the surrounding landscape. Overall, our results show that sewage discharge has a significant impact on water quality and benthic riverine communities, regardless of the surrounding land uses. Agricultural inputs, however, could be more important than treated sewage discharge in reducing the abundance of sensitive invertebrate taxa. We need both improvements to wastewater treatment processes and reductions in agricultural pollution to reduce threats to vulnerable freshwater communities.     

Analysis of fish communities along a rural–urban gradient in a neotropical stream (Piracicaba River Basin,São Paulo,Brazil)

This study investigated the fish fauna of a stream in southeastern Brazil that runs through sugar cane-growing and urban areas that are subject to sewage discharge. It aimed to determine the importance of spatial and environmental factors on fish distributions and to assess the use of fish as indicators of the environmental conditions. A longitudinal pattern of chemical water quality was observed, with more disturbed conditions at the urban sites. Several opportunistic or tolerant and omnivorous species such as Astyanax altiparanae, Poecilia reticulata, and Astyanax fasciatus were numerically abundant at these urban sites, which resulted in a consistent increase in species density and biomass along the stream. Redundancy analysis extracted three axes, identifying a nutrient–productivity gradient associated with different species composition patterns, as also detected by the indicator species analysis. No species could be considered a potential indicator of the agricultural area in the dry season, whereas four different species were judged potential indicators of three urban sites. In order to explain species distribution, variation in species abundance was partitioned into spatial and environmental components. The latter was more important, explaining 25.4% of the variation. We concluded that the fish assemblage of the Guamium stream is undergoing the initial stages of disturbance, with pronounced effects at the urbanized area, but no detectable changes at the sugar cane sites. Therefore, fish assemblages might be used as ecological indicators to detect urban impacts in similar rivers. However, the potential use of fish to diagnose stressors in areas of sugar cane plantations should be complementary to more comprehensive studies aimed at understanding the influence of this crop on freshwater resources.     

Combined exposure to parasite and pesticide causes increased mortality in the water flea Daphnia

Organisms are exposed to multiple biotic and abiotic environmental stressors, which can influence the dynamics of individual populations and communities. Populations may also genetically adapt to both natural (e.g. disease) and anthropogenic (e.g. chemical pollution) stress. In the present study, we studied fitness consequences of exposure to both a parasite (i.e. biotic) and a pesticide (i.e. abiotic) for the water flea Daphnia. In addition, we investigated whether these fitness consequences change through time as a population evolves. Thus, we exposed Daphnia magna clones, hatched from dormant eggs isolated from different time layers of a natural dormant egg bank, to the parasite Pasteuria ramosa and the insecticide diazinon in a multifactorial experiment. While our experimental treatments for unknown reasons failed to induce disease symptoms in the Daphnia, we did observe a reduced survival of D. magna when simultaneously exposed to both the parasite and the pesticide. No increased mortality upon exposure to individual stressors was observed. We did not observe an evolutionary change in fitness response of the Daphnia clones hatched from different time horizons upon exposure to stressors.     

Effects of physico-chemistry, land use and hydromorphology on three riverine organism groups: a comparative analysis with monitoring data from Germany and Austria

The majority of studies comparing the response of biotic metrics to environmental stress in rivers are based on relatively small, homogeneous datasets resulting from research projects. Here, we used a large dataset from Austrian and German national river monitoring programmes (2,302 sites) to analyse the response of fish, diatom and macroinvertebrate metrics to four stressors acting at different scales (hydromorphology, physico-chemistry, riparian and catchment land use). Nutrient enrichment and catchment land use were the main discriminating stressors for all organism groups, over-ruling the effects of hydromorphological stress on the site scale. The response of fish metrics to stress was generally low, while macroinvertebrate metrics performed best. The Trophic Diatom Index (TDI) responded most strongly to all stressors in the mountain streams, while different metrics were responsive in the lowlands. Our results suggest that many rivers are still considerably affected by nutrient enrichment (eutrophication), which might directly point at implications of catchment land use. We conclude that monitoring datasets are well-suited to detect major broad-scale trends of degradation and their impact on riverine assemblages, while the more subtle effects of local-scale stressors require stream type-specific approaches.     

A fish index of biotic integrity for South Dakota's Northern Glaciated Plains Ecoregion

Ecosystem goods and services in streams are impaired when their biotic communities are degraded by anthropogenic stressors. An index of biotic integrity (IBI) translates community structure into a standardized ecoregion-specific stream health score. Documenting stream health is especially important in the Northern Glaciated Plains (NGP) Ecoregion, which is undergoing rapid landscape alterations through increased agriculture production. Our objectives were to develop a fish IBI and validate candidate reference sites for NGP wadeable perennial streams. Fish were sampled from 54 sites (consisting of reference sites, known-condition least and most disturbed sites, and random sites) during summers 2006–2011. Candidate metrics were sorted into nine metric classes based on attributes of fish assemblage form and function. Metric values were screened using metric range, signal-to-noise ratios, responsiveness to disturbance, and redundancy tests until each metric class contained only those metrics most responsive to anthropogenic stressors. The final IBI consisted of six metrics that were reflective of prairie stream fish assemblages, and differentiated between known-condition least and most disturbed sites. The mean reference sampling site IBI scores were found to be similar to both least and most disturbed sites (Mann–Whitney U-test; P < 0.05). Twelve reference site scores were below the NGP's median (69), whereas the other 11 sites were above the median and were representative of least disturbed conditions. We now have developed a standardized bioassessment tool for evaluating stream health, as well as a baseline for long-term monitoring in a dynamic ecoregion.     

Morphological and Genetic variations in the natural populations of Carinotetraodon travancoricus

Carinotetraodon travancoricus or Malabar puffer fish is an endemic species described from rivers originating from the Western Ghats in South India. This species is captured extensively as an aquarium fish and is having substantial demand in global markets. However, being prone to overfishing and impacts of anthropogenic alterations in its habitats, IUCN has categorized it as a threatened/vulnerable species. Since, knowledge on variability of wild populations could help in their conservation and management, morphometric and genotypic analyses were carried out in natural populations of C. travancoricus inhabiting two geographically separated rivers Pamba and Chalakkudy. Mean values of eleven length parameters measured in 456 males and 439 females inhabiting these rivers revealed significant difference (ANOVA, F = 10.2 p < .001) between sexes and between females inhabiting two rivers. Principal component analysis revealed two factors in males and three factors in females, explained variance of 83.62% and 89.94% in respective sexes. Results of both PCA and discriminant function analysis indicated perceptibly high degree of separation between individuals inhabiting the two rivers. A total of 25 COI sequences were generated from C. travancoricus collected from rivers Pamba (n = 14) and Chalakkudy (n = 11). Sequence alignment revealed considerable base substitutions between samples from both rivers, indicating possibility of population differences. AMOVA analysis also provided significant Fst value (0.622; p-value .00) in support of population difference between individuals of both rivers. Interpopulation genetic distance reached upto 2.50%, high enough to confirm genetic diversity among individuals, revealing perceptible population events within this species. The present results indicated high degree of population difference between C. travancoricus inhabiting geographically separated rivers Pamba and Chalakkudy as evidenced from both morphometric and genotypic analyses.     

鱼类生物群落对太子河流域土地利用、河岸带栖息地质量的响应

河流生态系统的退化是多空间尺度环境因子作用的结果。探讨不同尺度环境因子及水生生物之间的作用关系,识别影响水生生物群落完整性的尺度问题,是有效开展水生生物保护的基础。基于2009年对太子河流域15个样点的鱼类、河岸带栖息地质量评价,结合遥感影像解译的太子河流域土地利用情况(包括流域尺度和河段尺度),研究鱼类完整性指数(F-IBI)与两种尺度土地利用、栖息地质量参数之间的关系。结果表明太子河上游地区河岸栖息地质量较好,下游地区由于农业用地、城镇用地比例的增加河岸栖息地质量明显下降。F-IBI与自然用地比例呈正相关,与农业、城镇用地比例呈负相关。农业用地对F-IBI的影响体现在流域尺度,而城镇用地在两种尺度上都存在显著影响。相比于农业用地,城镇用地相同比例的增加会导致F-IBI更快的下降。底质、水质状况、人类活动强度是显著影响F-IBI的栖息地质量评价参数。3项参数均随农业和城镇用地比例增加而降低,农业用地主要在流域尺度上对3项参数产生影响,城镇用地主要影响底质和水质状况2项参数,而在两种尺度上的影响相差不大。     

Divergent reaction of fish metrics to human pressures in fish assemblage types in Europe

Using a large pan-European dataset, we compared least disturbed sites to sites impacted by human pressures across broad river types to assess which aspects of bio-ecological traits of the fish assemblage are most sensitive to alterations of the river ecosystem. To control for variation across river types and large-scale environmental gradients, we began by clustering the least disturbed sites (n = 716) into four homogenous fish assemblage types (FATs) differing by four fish metrics, i.e., lithophilic, rheophilic, omnivorous, and potamodromous fish. We predicted these FATs (headwater streams, medium gradient rivers, lowland rivers, and Mediterranean streams) using environmental variables, i.e., altitude, river slope, temperature, precipitation, latitude, and longitude for impacted sites in our dataset (n = 2,389). Using tests of sensitivity and intensity, 17 fish metrics showed a clear reaction to human pressures. However, 12 metrics responded exclusively within only one of the four FATs. Hence we observed a divergent reaction of fish metrics to human pressures in, e.g., headwater versus lowland rivers. Type-specific reactions are useful in customizing impact assessment for particular river types. It is of primary importance to understand the comparative sensitivity and efficiency of fish-based indicators of water quality for detecting human-induced degradation of river ecosystems.     

Microzooplankton as a bioindicator of environmental degradation in the Amazon

Recent studies have assessed the impact of the discharge of untreated domestic and industrial effluents on aquatic ecosystems. In the 1980s, large industrial factories were set up in the municipality of Barcarena, Amazon, Brazil; however, this was not accompanied by investments to improve basic sanitation and housing structures in the region, resulting in deterioration of the surface water quality. The main aims of this study were to characterize the zooplankton community of surface water to elucidate the influence of unregulated territorial occupation and industrial development on ecosystem degradation of three rivers located near the industrial and port area of Barcarena. The physico-chemical and microbiological parameters linked to water quality assessment were also analyzed. In each river, three sites were selected for sampling, which was performed quarterly in 2012. The zooplankton community of the three rivers comprised 149 taxa, and the density of zooplankton varied among rivers; Arapiranga River had the lowest values, followed by Curuperê-Dendê and Murucupi Rivers. IndVal analyses show that Keratella lenzi and Anuraeopsis sp1 have elevated fidelity and specificity to the Curuperê-Dendê and Murucupi Rivers, both of which are strongly affected by anthropogenic forces. Difflugia distenda and Difflugia sp7 were associated with Arapiranga River, which has a well-conserved ecosystem.     

Larval fish assemblage recovery: a reflection of environmental change in a large degraded river

Estuaries are globally important to fisheries but face many anthropogenic stressors that reduce water quality and degrade benthic habitat. The Maumee River estuary has been degraded by industrial contaminants, high sediment and nutrient loads, channelization and elimination of surrounding wetlands, lessening its value as spawning habitat for fishes of Lake Erie. Regulation and better management practices (BMPs) in the watershed have improved the water quality in this estuary, which should result in a response of the biotic community. We compared recent (2010/2011) larval fish assemblage data to similar data from the 1970s (1976/1977) in order to identify changes due to improved water and habitat quality. Family‐level diversity was greater in recent study years compared to the 1970s and family richness increased from 6 to 10. In addition, the abundance of lithophilic spawning fishes was significantly greater in the recent study years. Increased diversity and family richness were consistent with increased water quality in the Maumee River whereas the observed increase in abundance of lithophilic spawners was consistent with an increase in the amount or quality of benthic habitat used by species in these families for spawning. Better wastewater management and agricultural practices in coastal watersheds can benefit the early life stages of fishes, thus benefitting coastal fisheries. Furthermore, larval fish assemblages may be useful indicators of biological integrity because of their sensitivities to environmental change. Routine sampling of estuarine larval fish assemblages could provide practitioners with insight into ecosystem changes and measure the response of the biotic community to restoration.     

Fish community response to the longitudinal environmental gradient in Czech deep-valley reservoirs: Implications for ecological monitoring and management

Ecological quality assessment of non-natural water bodies is, in contrast to natural systems, less developed and requires determining biological indicators that reliably reflect environmental conditions and anthropogenic pressures. This study was motivated to propose fish indicators appropriate for assessment of reservoir ecosystems in central Europe. We analysed changes in water quality, total biomass and the taxonomic, trophic and size composition of fish communities along the longitudinal axes of four elongated, deep-valley reservoirs. Due to high nutrient inputs from their catchments, the reservoirs exhibited pronounced within-system gradients in primary productivity and water transparency. Although fish communities were similar among the reservoirs and dominated by few native species, the community structure and biomass systematically changed along the longitudinal axes of the reservoirs. The biomass and proportion of planktivores/benthivores in the fish community were highest at eutrophic sites near the river inflow and declined substantially towards deep, more oligotrophic sites close to the dam. The biomass and proportion of piscivores significantly increased downstream within the reservoirs alongside improving water quality. At species level, perch Perca fluviatilis and bream Abramis brama responded most sensitively, although in opposite directions, to the longitudinal environmental gradient. The major longitudinal changes in fish community characteristics were found to be consistent between pelagic and benthic habitats. The results of this study suggest that fish communities are appropriate indicators of eutrophication and can be used for ecological quality assessment of non-natural lentic water bodies, such as reservoirs. Moreover, our results underline the necessity to consider within-system gradients in water quality and the fish community when planning sampling programmes for deep-valley reservoirs.