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River estuaries are influenced by terrestrial and marine areas, and have a unique environment that is constantly fluctuating. They are also important habitats for biodiversity conservation. Tanegashima Island is significantly influenced by the Kuroshio Current. Although nearby Yakushima Island has been recognized as a World Natural Heritage site and information on many species has been collected, there is little information on species inhabiting the river estuaries of Tanegashima Island. In this study, the river estuarine ichthyofauna of 26 small and medium‐sized rivers on Tanegashima Island was surveyed and a total of 2758 individuals of 29 species and one genus belonging to 15 families were collected. The fish fauna of the river estuaries of Tanegashima Island were classified into three groups, namely the river estuaries where coastal terraces are underdeveloped and drowned valleys are formed, the river group where the riverbed gradient at the mouth is high, and other river groups. Environmental factors selected as being important for ordination of fish fauna were the altitude of the headstreams at the watershed scale, the gradient of the river estuarine area, and the presence or absence of rapids in the estuary. The importance of the geohistorical factor of drowned valley formation, in addition to habitat and watershed scale environmental factors, as a factor on river estuarine fish fauna is an important finding for future conservation of local biota diversity. [ABSTRACT FROM AUTHOR]

Climate change is one of the major threats to coastal fish biodiversity, and optimization of no‐take marine protected areas (MPAs) is imminent. We predicted fish redistribution under climate change in coastal China Seas with joint species distribution modeling and prioritized areas for conservation with Zonation, for which we used core area zonation (CAZ) and additive benefit function (ABF). Based on our results, we devised an expansion plan of no‐take MPAs. Under climate change, fish were redistributed northward along the coast. These redistributions were segmented by the Yangtze River estuary and its adjacent waters, indicating a possible biogeographical barrier. Under CAZ and ABF, significantly more fish habitat was conserved than under random prioritization (p < 0.001, Cohen's d = –0.36 and –0.62, respectively). The ABF better represented areas with higher species richness, whereas CAZ better represented core habitats for species with narrow distributions. Without accounting for species redistribution, the expanded MPAs were mainly distributed in the northwest of the South China Sea, the East China Sea, the north of the Yellow Sea, and the west of the Bohai Sea. When accounting for species redistribution, the proposed MPAs were mainly distributed in the north of the Bohai Sea and southwest of the Yellow Sea, corresponding to the northern species redistributions. These MPAs conserved less habitat for fishes at present but protected more and better quality habitat for fishes in 2050 and 2100 than those MPAs that did not account for species redistribution, indicating improved fish conservation under climate change. Incorporating species redistribution and trade‐offs between areas with high species richness and areas that contain habitats for rare species are suggested to address coastal fish conservation under climate change. This work provides valuable information for fish conservation and is a precursor to systematic conservation planning along the coastlines of China Seas. [ABSTRACT FROM AUTHOR]

Aim: Reef fishes are commonly recognized as sentinels of the ongoing tropicalization in biogeographic transition zones between temperate and tropical areas. Despite the reliance of these marine ectotherms on the benthos, the importance of benthic habitat has rarely been considered as a factor constraining fish distribution. Therefore, our study aims at examining the consequences of both temperature and benthic variations on the fish fauna and diagnosing potential sentinels of these environmental changes. Location: Taiwan, West Pacific. Taxon: Teleostei (184 species). Methods: We examined how the partitioning of habitats can influence the specialization of fish fauna along a latitudinal gradient. We diagnosed 'specialist' and 'generalist' fishes in this partitioning. For each specialist, we further evaluated whether its distribution is constrained by temperature, benthic habitat or both factors combined. The change in sea surface temperature over the last three decades was also monitored. Results: Fish fauna showed the highest specialization when tropical and subtropical partitions of habitat were considered. Fifty‐one tropical specialists, 7 subtropical specialists and 21 possible generalists were identified. Among specialists, 13 species were associated with temperature, 19 with habitat and 26 with both factors. Steady warming occurred across latitudes, but was accentuated in the winter of subtropical habitat. Main Conclusions: Our results suggested that the distribution of some specialist fishes was constrained only by temperature while the distribution of some others also depended on the availability of benthic habitats. Consequently, under global warming, the distribution of some specialists might shift in a manner that follows the movement of isotherms, while the distribution of others might also be conditioned by the poleward shifts of benthos. A temporal mismatch between the emergence of suitable thermal environments and the arrival of some specialists may exist. Therefore, the tropicalization of high‐latitude areas may be characterized by different waves of colonization. [ABSTRACT FROM AUTHOR]

Abstract: Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investigation was based on fish catch data from the Z‐31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin. [ABSTRACT FROM AUTHOR]

The feeding ecology of Great Cormorants (Phalacrocorax carbo) during the breeding season in the Kano River basin, central Japan, was examined to clarify the trophic relationship between the cormorants and ayu (Plecoglossus altivelis altivelis) reared for mass release in the river. The ayu was most frequently found in stomachs of cormorants culled during the breeding season, despite relatively poor catch in the year-round fish fauna research in the watershed. Carbon and nitrogen stable isotope ratios of some ayu individuals extracted from the stomachs of the culled cormorants were similar to the isotopic values of ayu caught in the watershed, whereas the other stomach-content ayu showed peculiarly high nitrogen isotopic values, clearly distinct from the values of the ayu caught in the watershed, and overlapped with the values of mass-release ayu. Furthermore, isotopic values of past diets inferred by the isotope analysis of livers of the culled cormorants were closer to the values of the mass-release ayu, relative to the past diet values inferred by the analysis of the cormorant muscles. This suggests that the food supply from the mass-release ayu had increased in the breeding season, since the isotopic turnover rate is faster in livers than in muscles. The huge number of formula-fed ayu released in the watershed create an anthropogenic food chain which is assumed to significantly support the breeding of the cormorants. [ABSTRACT FROM AUTHOR]

Abstract: Riverine environments have been threatened by anthropogenic perturbations worldwide, whereby their fish assemblages have been modified by habitat changes and nonendemic species invasions. We assessed changes in fish assemblages by comparing the species presence in historical and contemporary fish data in the Yellow River from 1965 to 2015. The temporal change in species assemblages was found with increased nonendemic species and fewer natives. Fish species richness of the river declined 35.4% over the past fifty years. Moreover, the decreased mean Bray–Curtis dissimilarity among reaches suggested that the fish assemblages of different reaches in the Yellow River were becoming more similar over time. However, temporal patterns of fish assemblages varied among reaches. In the upper Yellow River, higher species richness and more invasive species were found than those in the historical record, while the lower reaches experienced significant species loss. Dam constructions, exotic fish invasions, and flow reductions played the vital role in structuring the temporal fish assemblages in the Yellow River. It is suggested that river basins which experienced different types and levels of stressors by anthropogenic perturbations can produce varied effects on their temporal trends of species assemblages. [ABSTRACT FROM AUTHOR]

Discharge-mediated seasonal patterns of food web interactions were investigated in two streams in Sri Lanka; Eswathu Oya (a perennial wet-zone stream) and Yan Oya (a seasonal dry-zone stream). Based on volumetric proportions of diet composition, relative abundance of fish species and their daily food rations, the mean cumulative consumption of each prey taxon was estimated for each fish population. Food web diagrams were prepared using trophic index of fish, trophic class of prey and feeding interactions between fish and prey. Both streams showed seasonal patterns of discharge due to rainfall, but no significant effect was evident in the trophic index of most fish species. In both streams, cumulative consumption of prey taxa was highest during low discharge regime due to increased abundance of both prey taxa and consumers. In Eswathu Oya, diversity of prey taxa was higher during the low discharge regime, but in Yan Oya, high diversity occurred during the high discharge regime. Herbivorous and/or detritivorous fish species were rare in Eswathu Oya but dominant in Yan Oya. Complex food web structure in Yan Oya due to high fish species richness and high diversity of prey categories made it less sensitive to discharge extremes in contrast to relatively simple food web structure in Eswathu Oya. This study, therefore, highlights the importance of maintaining the quality of riparian environments for conservation of biodiversity. [ABSTRACT FROM AUTHOR]

The Aral Sea is a terminal lake lying within the deserts of Central Asia in Kazakhstan and Uzbekistan, draining the Amu Darya and Syr Darya rivers. Before the 1960s, it was a large brackish water lake with an average salinity of 10.3 g L−1. The anthropogenic regression and salinization of the Aral Sea at that time resulted from increasing water withdrawals from the Amu Darya and Syr Darya for irrigation purposes. The salinization resulted in the disappearance of most of its invertebrates and all freshwater fish. As a result of the water level decrease, the Aral Sea divided into a northern Small Aral and a southern Large Aral at the end of the 1980s, with the two having different hydrological regimes. After construction the first Kokaral Dam in 1992, the water level of the Small Aral Sea increased by >1 m, with a gradual decline in the salinity beginning. To date, the Small Aral has again become brackish. Its average salinity reached 5.3 g L−1 by April-May 2013, with the highest salinity of 9.9 g L−1 in Butakov Bay, whereas the salinity was very low at 1.2-2.0 g L−1 in the estuary zone of the Syr Darya. There is an ongoing process of restoration of the former biodiversity, with many fresh water and brackish water invertebrate species reappearing due to the decreasing salinity. Freshwater fish species (bream, roach, carp, asp, zander, wels, etc.) returned into the Small Aral from the Syr Darya River and lakes in its lower reaches where they survived. Fisheries are recovering and catches are growing. Continuing salinity decreases, however, may cause decreases in the numbers, or even disappearance, of marine and halophilic invertebrate species. This study summarizes the results of studies of the Small Aral zooplankton, zoobenthos and ichthyofauna carried out in the spring of 2013. An historical review of changes in the Aral Sea and its fauna also is presented. [ABSTRACT FROM AUTHOR]

Canyons play a fundamental role in enhancing the abundance and diversity of marine organisms through the transport of organic matter and food resources, the presence of complex physical habitats and the absence of trawl fishing. During four baited lander deployments carried out in the Bari Canyon (Southern Adriatic Sea, Central Mediterranean), at depths of 443-788 m, about 43 h of video records were taken, for a total of 619,200 video frames. A total of 12 benthopelagic fish species (five chondrichthyes and seven osteichthyes) were identified. The blackspot seabream ( Pagellus bogaraveo) was the most often observed fish species. The depth of 787 m represents a new depth record for this fish in the Adriatic Sea. Groups of up to 40 individuals of P. bogaraveo were attracted to the bait and were shown in single frames. The individuals were observed both exploring the area and feeding actively on the bait. The European conger ( Conger conger) was recorded at each deployment. Clear scavenger behaviour was also observed in this teleost fish and in the shark Etmopterus spinax. The shark species Centrophorus granulosus and Hexanchus griseus, which are considered 'vulnerable' on the published IUCN Mediterranean Regional Red List, were also recorded but, although attracted by the bait, they were never seen feeding on it. Other fish species, harvested on fishing grounds, such as Merluccius merluccius, Helicolenus dactylopterus and Polyprion americanus, were also recorded. This study represents the first in situ documentation, at very low impact, of the fish fauna in the Bari Canyon, providing new insights into its small scale distribution and behaviour, the first in situ direct observation of the variable feeding behaviour of P. bogaraveo and its gregarious habits, as well as indicating that this canyon could act as a refuge area for species that are vulnerable to fishing on the open slope. [ABSTRACT FROM AUTHOR]

While there is already a comprehensive understanding of the effects of environmental variables, such as dissolved oxygen, temperature and salinity, on the structure, biomass and metabolism of aquatic biota in estuarine habitats, the effect of sedimentation, a harmful underlying factor, remains unclear. The aim of this study was to assess the differences in fish assemblages along the freshwater to salt water gradient of a large tropical estuary, and to evaluate the effects on them of habitat disturbance associated with shallow water sedimentation in the intertidal areas. Fish and environmental variables were recorded in the upper, middle and lower salinity zones of the estuary at ebb tide in both the dry and wet seasons. Sediment samples associated with different levels of habitat disturbance were analysed using granulometry, and their organic content and dissolved oxygen levels were quantified. Water temperature, salinity, pH and dissolved oxygen levels were also measured. Habitat disturbance was found to be correlated with the density, biomass and richness of fish assemblages. A total of 77 species were recorded, forming two distinct fish assemblages, with the Eleotridae family dominating in the upper zone, and Gerreidae, Gobiidae and Tetraodontidae the most common in the middle and lower estuary. Changes in the structure of fish assemblages, including reductions in density, biomass and richness, were associated with disturbance to natural features, where muddy sediment was replaced by sandy sediment and the quantity of organic matter fell. Atherinella brasiliensis was the species which showed a preference for the disturbed areas in the middle and lower zones, while Dormitator maculatus showed a preference for them in the upper estuary. They may be taken as indicators of habitat disturbance due to shallow sedimentation. [ABSTRACT FROM AUTHOR]

Streams in North Rhine- Westphalia ( Germany) are frequently impacted by hydromorphological degradation leading to a loss of sensitive species and a reduction in diversity. These findings mean that the final objective of the European Water Framework Directive to achieve the good ecological status will be failed for a large number of streams. In a holistic approach, a new concept, considering the cost efficiency, has been developed to enhance habitats by morphological changes. This guide serves as a basis for stream restoration projects. The theoretical background is that near-natural sections influence adjacent sections of medium habitat quality positively by migration of type-specific sensitive organisms. The preconditions are a local taxa richness in the catchment area, the reduction of nutrients and organic matter, and the guarantee of free movement. This so-called 'spreading effect' can be measured upstream and downstream. The length of by these means valourized sections depends on the stream type and on the biological quality component. [ABSTRACT FROM AUTHOR]

Our objectives are to examine the influence of the difference in stress tolerance among species on patterns of nestedness and to test whether a set of several small ponds supports more species than a few large ponds of equal area. Although fish species assemblages for each group of all fish, tolerant and intolerant species were significantly nested, intolerant species showed stronger nested tendency than tolerant species, suggesting that the tolerance of species can influence the patterns of nestedness. These results suggest that the tolerance of species can influence the patterns of nestedness. As for the comparison of cumulative species richness in small ponds and large ponds, although small ponds supported more species for tolerant species, there was little difference for intolerant species. [ABSTRACT FROM AUTHOR]

The article discusses the management of the ponds within irrigation systems after the fish fauna have changed in Mount Iwate, Japan. It mentions that the ponds were monitored after the invasive piscivorous largemouth bass were eradicated. It states that species richness and diversity had increased in bass-eradicated ponds. It stresses the need for continuous monitoring and adaptive management of the ponds.

In Amazonia reduced-impact logging, which is meant to reduce environmental disturbance by controlling stem-fall directions and minimizing construction of access roads, has been applied to large areas containing thousands of streams. We investigated the effects of reduced-impact logging on environmental variables and the composition of fish in forest streams in a commercial logging concession in central Amazonia, Amazonas State, Brazil. To evaluate short-term effects, we sampled 11 streams before and after logging in one harvest area. We evaluated medium-term effects by comparing streams in 11 harvest areas logged 1–8 years before the study with control streams in adjacent areas. Each sampling unit was a 50-m stream section. The tetras Pyrrhulina brevis and Hemigrammus cf. pretoensis had higher abundances in plots logged ≥3 years before compared with plots logged <3 years before. The South American darter (Microcharacidium eleotrioides ) was less abundant in logged plots than in control plots. In the short term, the overall fish composition did not differ two months before and immediately after reduced-impact logging. Temperature and pH varied before and after logging, but those differences were compatible with normal seasonal variation. In the medium term, temperature and cover of logs were lower in logged plots. Differences in ordination scores on the basis of relative fish abundance between streams in control and logged areas changed with time since logging, mainly because some common species increased in abundance after logging. There was no evidence of species loss from the logging concession, but differences in log cover and ordination scores derived from relative abundance of fish species persisted even after 8 years. For Amazonian streams, reduced-impact logging appears to be a viable alternative to clear-cut practices, which severely affect aquatic communities. Nevertheless, detailed studies are necessary to evaluated subtle long-term effects. [ABSTRACT FROM AUTHOR]

Biotic homogenization, the process of gradual replacement of native biotas by nonindigeous and locally expanding nonnative species, is rapidly diminishing the regional distinctiveness of global terrestrial and aquatic ecosystems. Although the empirical study of biotic homogenization is substantial and growing, the mechanisms underlying its dynamics remain poorly understood. We recently developed a theoretical model that predicts levels of biotic homogenization or differentiation (i.e., decreased community similarity) according to a series of distinct mechanisms that describe the outcomes of various interactions between native species, nonnative species, and the environment. Here, we test this model using empirical data for freshwater fish faunas in the United States at three spatial scales: the entire continent, zoogeographic provinces in California, and watersheds within these provinces. Our analysis reveals that, in general, mechanisms depicting widespread introductions of cosmopolitan species and either no or differential spatial patterns of native- species extirpations explain fish-community homogenization across multiple spatial scales. Our results also highlight the potential effect of spatial grain on the perceived importance of different invasion-extinction scenarios shaping patterns of homogenization and differentiation. Next, we discuss the utility of the model for providing insight into the dominant ecological processes likely driving the homogenization of other major taxonomic groups that currently lack quantitative estimates of community change. Our study is the first to quantitatively examine the relative importance of different ecological mechanisms that can generate observed patterns of biotic homogenization. Using this model may allow advance prediction of future patterns of homogenization by explicitly considering underlying ecological processes and mechanisms. [ABSTRACT FROM AUTHOR]

To study (1) the large-scale distribution patterns of freshwater fishes in the Western Ghats of India; (2) the endemism and uniqueness of the fishes in various zones; and (3) the threat status of fishes by categorizing them under low risk (LR), vulnerable (VU), endangered (EN) and critically endangered (CR). The Western Ghats of India. The scientific literature describing the freshwater fishes of the Western Ghats was reviewed. Data describing the lists of the species were extracted and complied. The species accumulation curve was plotted using Michaelis–Menten-like equation. The Western Ghats was divided into six zones and similarity of the species was calculated using Jacquard's index. Literature to date records 288 species belonging to 12 orders, 41 families and 109 genera, of which 118 species are endemic and 51 are unique. However, the species accumulation curve shows that there might be 345 species in this region, indicating that 16% species have not been recorded to date. An analysis of the distribution pattern of fishes in the Western Ghats suggests that the southern region is more diverse than the northern and central regions. The southern region shows high endemism and high uniqueness while the northern region shows high endemism but less uniqueness. The similarity index between the zones indicates that as the distance between the zones increases similarity decreases. The status of 105 of 288 species was not known due to data deficiency but among the remaining 183 species, 58 species were categorized as LR, 41 as VU, 54 as EN, 24 as CR while the remaining six species were introduced. The distribution patterns of fishes in the Western Ghats are discussed in accordance with the geography of Western Ghats, its climatic conditions and ‘Satpura Hypothesis’. The threat status of fishes found in Western Ghats suggests that at least 41% of fish fauna is threatened by either being VU, EN or CR. Implication of potent conservation measures is necessary to conserve the fish fauna of Western Ghats. [ABSTRACT FROM AUTHOR]