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The Loskop Dam is the most polluted impoundment in the Olifants River, because it receives pollutants from the entire mine-dominated upper catchment. However, histopathology of fish inhabiting this polluted dam is scantly explored. The current study aimed to investigate the histopathology of the gills and liver of Labeo rosae from Loskop Dam. Alkaline pH was observed throughout the study with most metal concentrations exceeding the water quality guideline for aquatic ecosystems. Regressive changes were the most prominent lesions for both organs with gills showing relatively more pathologies than the liver. Epithelial lifting was 100% prevalent during both seasons in the gills whereas a significant expansion of lipofuscin-laden melanomacrophages (MMCs) showed 100% prevalence in the liver. Gills were significantly different in their prevalence of histopathology between the two seasons, which was not the case for liver. The histopathology recorded in this study shows that the health of L. rosae at Loskop Dam was compromised. Given the exacerbating pollution level in the upper Olifants River, these findings serve as a warning to conservation authorities and emphasise the necessity for regular monitoring of fish health at Loskop Dam to assess pollution levels using fish health as a sensitive indicator to altering pollution levels. [ABSTRACT FROM AUTHOR]

The paper reports a study of the responses of fishing communities, Regência and Povoação, located at the mouth of the Doce River, to the collapse of the Fundão dam, owned by Samarco Mineração, in 2015. After the disaster, the fishermen's social and cultural practices have undergone drastic changes. The arrival of tailings in the river has impaired their routines and income. The fishermen and their families indicate a sense of loss of identity and insecurity because of the uncertainty. They do not know if they will be able to resume fishing in these waters. This feeling contrasts with the results of a study conducted before the disaster. [ABSTRACT FROM AUTHOR]

Sakarya River with a length of 824 km is one of the most important lothic ecosystems of Turkey. Sarıyar, Gökçekaya and Yenice Dams were constructed on the Sararya River for the purpose of electric supply and utility water for agricultural and fishery activities. In this study, sediment samples were collected from 14 stations selected on areas seasonally (2015–2016). Also, cyprinidae species (Carassius gibelio (Bloch, 1782), Capoeta baliki Turan, Kottelat, Ekmekçi & Imamoglu 2006) were caught from Dam Lakes and Sakarya River. Cr, Ni, Cu, Zn, Pb levels in sediment samples and in tissues (liver, gill and muscle) of fish were analyzed in samples by Analytic Jena ContrAA 700 (high-resolution continuum source atomic absorption spectrometer). The data observed were evaluated with national and international quality criteria. According to the data in the study results, heavy metal accumulations in the gill and liver of fish were determined higher than muscle. Zn levels in muscle of C. gibelio caught from Yenice Dam Lake were higher than the permissible limit stated by Turkish legislation and FAO. Also, Cr and Ni levels in sediment samples especially during rainy seasons were higher to dry seasons and Cr and Ni levels were detected higher than sediment quality guidelines. [ABSTRACT FROM AUTHOR]

The Pak Mun dam is among the most controversial hydropower projects in Thailand. However, the dam's impacts on upriver tributaries have been neglected. We engaged fishers living in three villages along the Sebok River – a major tributary of the Mun River, upstream of the Pak Mun dam – to collect fish catch data for 24 months between 2014 and 2016. Using these data and fishers' knowledge, the negative fishery impacts of the Pak Mun dam and the Ban Ot irrigation dam on the Sebok River were assessed. Both dams have negatively impacted Sebok River fisheries for migratory species. [ABSTRACT FROM AUTHOR]

The effect of seasonal changes and ecological aspects of Afrodiplozoon polycotyleus (Paperna, 1973) collected on Labeobarbus marequensis (Smith, 1841), Enteromius trimaculatus (Peters, 1852) and Enteromius radiatus (Peters, 1853) was investigated from January to October 2008. Fish were collected at the Nwanedi-Luphephe dams, Limpopo River System, South Africa using gill, cast and seine nets and electrofishing gear. Enteromius radiatus and E. trimaculatus were the most infested compared with L. marequensis. Seasonal changes had an influence on the intensity of A. polycotyleus, with infestation rates higher in spring, summer and autumn. The adults predominantly infected the medial region of the second gill arch, whereas diporpae were mainly found on the first gill. Neither sex nor water quality changes had an influence on the intensity of the parasite. The health condition of the hosts was not affected by the parasite. The different infestation rates of the parasite between the species could be attributed to host characteristics, behaviour and habitat preferences. The selection of a particular gill/region could be attributed to space for attachment organs and food supply, as well as flow and velocity of the water over the gills. The occurrence of A. polycotyleus on E. radiatus constitutes a new host record. [ABSTRACT FROM AUTHOR]

Low-head dams are a primary source of anthropogenic disturbance to river systems. They have the ability to change rivers from lotic to lentic habitats, affect sediment transportation, connectivity, water quality, linkages with wetlands and the quality of in-stream and riparian habitats. These changes can effect fish community structures and have the potential to alter the success of organisms in the system. However, there is no standard sampling protocol to assess dam impacts under varying flow regimes. The Vermilion River and its tributary, the North Fork Vermilion, are both impacted by low-head dams creating lentic habitats within each system. In October 2012 and May 2013, fish assemblages were sampled using direct current (DC) electrofishing at a total of 12 sites. Community composition at base flow responded strongly to both dams and differed between the two drainages. In sharp contrast, there was no effect of dams or differences between rivers during high flow. To adequately assess dam impacts on fish assemblages, we recommend sampling after base flow has been established. Sampling at high flow will reflect the homogenization of habitats and fish assemblages. [ABSTRACT FROM AUTHOR]

The ecological status of Hout River Dam was evaluated in 2011 by assessing fish health, based on condition factor (K), health assessment index (HAI) and inverted parasite index (IPI), which provided a simple and rapid means of establishing the health of fish. Surveys were conducted during summer, winter and spring 2011. To verify results, water quality was analysed during each survey.Clarias gariepinus,Oreochromis mossambicusandCyprinus carpiowere collected using conventional angling gear and gillnets. MeanKvalues of 0.6, 2.0 and 1.4, and HAI scores of 38, 41 and 35, were recorded for each species, respectively. The metrics that correlated best with fish health scores were haematocrit values and ecto- and endoparasite indices. Differences inK, HAI, and HAI using IPI determinations, were insignificant (p> 0.05) between species, while water contaminants, with the exception of ammonium (NH4), nitrate (NO3) and aluminium (Al) concentrations in summer, fell within the levels stipulated by the South African target water quality range guidelines for aquatic ecosystems. It was thus inferred that the dam was in a good ecological state. [ABSTRACT FROM PUBLISHER]

Comments on the plans to remove 63 dams in 15 U.S. states and the District of Columbia. Effect of the nation's aging dam infrastructure, combined with a growing understanding of the negative ecological impacts of dams; Problems presented by dams, including drowning valuable habitat under reservoirs and blocking annual migrations of fish; Benefits of dam removal, including better water quality and revitalized fisheries.