Distribution of fishes in the floodplain-channel complex of the lower reaches of the Irtysh River

The composition of fish, their location and movements in the channel, channel depressions, and flood waters of the lower reaches of the Irtysh River are investigated. This study is conducted with computer sonar systems used for different purposes. Diurnal and seasonal dynamics of movements of the fish and the abundance and composition of fish aggregations are revealed in the studied sites. The biological unity of the fish community of the floodplain-channel complex is demonstrated.     

Distribution of fish in the complex of floodplain-riverbed biotopes of the Irtysh

Distribution, composition, and movements of fish within the floodplain-riverbed complex of the Lower Irtysh are investigated. The principal working tools were hydroacoustic computerized complexes for the detection of fish aggregations and of their movements in the floodplain water course. Twenty-four-hour hydroacoustic observations revealed the predominantly crepuscular-nocturnal type of activity of most fish and the mass downstream migration of juveniles at the onset of the night. Seasonal traits of formation of fish aggregations on key biotopes of the Irtysh are revealed, and their biological harmony is shown. The necessity that fish distribution should be analyzed as a dynamic phenomenon is shown.     

Distribution of fish in the river system of the Lower Irtysh

We report the results of investigation of fish distribution in water bodies of different types (open floodplain complex, closed lake, floodplain channels, and a riverbed depression) of the river system of the Lower Irtysh obtained by application of differently aimed hydroacoustic complexes and by traditional ichthyological methods. Distribution, composition, and abundance of fish aggregations and their diurnal movements are determined in different water areas. Periodicity, range, and direction of fish migrations, rhythm of downstream migrations of juveniles under various conditions are recorded. Distribution of fish is considered as a continual process controlling the biological integrity of the river system. Significant presence of nomadity (various migrations and local movements) is demonstrated in fish, reflecting multilevel lability of the environment in the floodplain-channel system of the Lower Irtysh. A set of notions is suggested defining application limits of principal terms characterizing fish movements of various scales: migrations, wanderings, and short-term movements.     

Biological significance of the Gornoslinkinskaya Riverbed Depression in the Irtysh

Distribution of fish in the Gornoslinkinskaya Riverbed Depression in the Irtysh is considered in relation to the time of day and to the season. Fish aggregations are characterized quantitatively and by their size and species composition. The major part of the fish population of the depression consists of fish juveniles. The biological significance of the riverbed depression is polyfunctional. The universal traits of the ecosystems of large river basins and mechanisms of their occupation by fish are discussed.     

Distribution of the fish rotan (Perccottus glenii Dybowski, 1877) in the Irtysh River basin and analysis of possible consequences for environment and people

Since 1916, rotan (Perccottus glenii Dybowski, 1877) has widely distributed in northwestern Eurasia. In 1973–1976, rotan populations were first detected in the basin of the Irtysh River: in Lake Peschanoe (Mertvoe) of Chelyabinsk oblast in the basin of the Tobol, a tributary of the Irtysh. In 1975, this fish was introduced to one of the ponds of the city of Chelyabinsk. Analysis of the spatiotemporal dynamics of findings shows that earlier records of the fish correlate with the network of roads, and later findings, with the river network. The results of a special inspection of isolated and floodplain water bodies (n = 77) performed within Chelyabinsk, Kurgan, Omsk, and Tyumen oblasts in 2006 indicate that at present this unwanted invader occurs in the major part of the Tobol basin. The northernmost finding of this species is from the floodplain of the Tobol in the vicinity of Tobolsk, from the Karachino oxbow (58°02′N, 68°10′E). Rotan has also been found at the Irtysh headwaters as well as in the basins of its other tributaries: Ishim and Om. The expansion of rotan threatens the floodplain water bodies of the middle Irtysh. This species carries diseases, competes with other fish species for food, and actively eats young fish of these species. Therefore, the data on rotan distribution in the tributaries of the Irtysh should be taken into account when analyzing the dynamics of the fish community of this river. Biology of rotan assumes its influence on the functioning of the natural foci of opisthorchiasis.     

Biogeography,ecoregions, and geomorphology affect fish species composition in streams of eastern Oklahoma,USA

Stream fish assemblages are structured by biogeographical, physical and biological factors acting on different spatial scales. We determined how physical factors, geomorphology and stream habitat, influenced fish species composition (presence–absence) in eastern Oklahoma, USA relative to the ecoregion and biogeographic effects previously reported. We sampled fish assemblages and surveyed geomorphology and habitat at 107 stream sites in the Boston Mountains, Ouachita Mountains, and Ozark Highlands ecoregions in eastern Oklahoma. Partial canonical correspondence analyses (pCCAs) and variance partitioning showed that patterns of endemism related to drainage basins and ecoregions explained important variation in fish species composition in all streams, but stream size and local channel morphology explained more variation overall. Stream size effects were most important in explaining variability in fish species composition in both northeastern and southeastern Oklahoma streams. Local channel morphology and substrate characteristics were secondarily important. Variables typically considered important as fish habitat (aquatic vegetation, etc.) had little effect on fish species composition.     

Gape Limitation, Prey Size Refuges and the Top–down Impacts of Piscivorous Largemouth Bass in Shallow Pond Ecosystems

Top–down control of phytoplankton biomass through piscivorous fish manipulation has been explored in numerous ecological and biomanipulation experiments. Piscivores are gape-limited predators and it is hypothesized that the distribution of gape sizes relative to distribution of body depths of prey fish may restrict piscivore effects cascading to plankton. We examined the top–down effects of piscivorous largemouth bass on nutrients, turbidity, phytoplankton, zooplankton and fish in ponds containing fish assemblages with species representing a range of body sizes and feeding habits (western mosquitofish, bluegill, channel catfish, gizzard shad and common carp). The experimental design consisted of three replicated treatments: fishless ponds (NF), fish community without largemouth bass (FC), and fish community with largemouth bass (FCB). Turbidity, chlorophyll a, cyclopoid copepodid and copepod nauplii densities were significantly greater in FC and FCB ponds than in NF ponds. However, these response variables were not significantly different in FC and FCB ponds. The biomass and density of shallow-bodied western mosquitofish were reduced and bluegill body depths shifted toward larger size classes in the presence of largemouth bass, but the biomass and density of all other fish species and of the total fish community were unaffected by the presence of largemouth bass. Our results show that top–down impacts of largemouth bass in ecosystems containing small- and deep-bodied fish species may be most intense at the top of the food web and alter the size distribution and species composition of the fish community. However, these top–down effects may not cascade to the level of the plankton when large-bodied benthivorous fish species are abundant.     

新疆阿勒泰地区额尔齐斯河和乌伦古河流域鱼类多样性演变和流域健康评价

为了解阿勒泰地区额尔齐斯河和乌伦古河流域的鱼类多样性现状和历史演变, 本研究于2013-2016年间在该流域的鱼类多样性进行了连续调查, 并结合历史资料和标本, 以Margalef丰富度指数、Shannon-Wiener多样性指数、Pielou均匀度指数分析评估了流域内鱼类的多样性水平和时空变化。该流域历史上分布有土著鱼类23种, 当前记录到19种, 流域内还有外来鱼类15种。阿勒泰鱼类的区系组成以鲤科种类为主, 其中特有和珍稀濒危物种占比高, 具有重要的保护价值。多样性指数计算结果显示, 2013-2016年鱼类多样性情况整体稳定, 额尔齐斯河鱼类物种数多于乌伦古河。研究还基于鱼类生物完整性指数(Fish Index of Biological Integrity, F-IBI)对34个采集点的河流健康状况进行了评价, 结果显示额尔齐斯河流域大多数调查点的健康状况处于“亚健康”或“一般”水平, 乌伦古河流域多数调查点的健康状况处于“健康”水平。水利工程、外来物种、过度捕捞是影响阿勒泰地区鱼类多样性的重要因素。未来应通过水利工程的联合调度、下泄合理生态流量、布设鱼类通道、规范养殖渔业、严控外来物种、本地土著鱼类的人工增殖放流, 以及合理的就地保护措施对阿勒泰地区的鱼类多样性加以保护, 提升水体健康程度。     

Irregularities of the bottom and fish aggregations on a stretch of the Irtysh

An original method for estimation of the effect of bottom irregularities on density of fish aggregations is elaborated. Calculation of the investigated relationship is based on material of surveys collected by an AsCor hydroacoustic complex and is made by means of special software. With reference to a deep-water stretch of the Irtysh channel, the quantitative parameters of the relationship between densities of fish aggregations and the index of bottom irregularity are revealed. The diagram of the relationship between bottom irregularities and density of fish aggregations, the three-dimensional model of bottom relief of the investigated water area, and echograms of fish aggregations on various stretches of the river are presented.     

Winter Fish Distribution in the Riverbed Depression in the Urtysh River

Journal of Ichthyology - Winter fish distribution is investigated by means of computerized hydroacoustic complexes in the largest riverbed depression in the Irtysh. Fish aggregations whose...     

Hydroacoustic investigation of taxonomic composition and of vertical distribution of fish in the riverbed depression

An original method of taxonomic identification of fish (at the family level) by means of hydroacoustic equipment is elaborated. The method is based on analysis of the form of instantaneous envelope of amplitudes of the acoustic signal reflected from fish. Analysis of distribution of mass fish of different size over horizons of the water column is made on the deep-water riverbed depression of the Irtysh and characteristics of their diurnal vertical migration are revealed.     

新疆布尔津盆地晚始新世一早渐新世岩石及生物地层

布尔津盆地中的第三纪地层过去被称为“乌伦古河组”。该套地层的岩性组合独特 ,不同于乌伦古河流域该组命名剖面的乌伦古河组。依据布尔津县城西北 2 0km处的额尔齐斯河北岸出露的地层剖面 ,建立两个岩石地层单位 :下部额尔齐斯河组和上部克孜勒托尕依组。额尔齐斯河组为一套富含铁质的色彩鲜艳的碎屑堆积 ,克孜勒托尕依组是一套浅黄绿色砂岩夹杂色泥岩地层。克孜勒托尕依村附近的建组剖面为一连续沉积剖面 ,含有 3个确切的哺乳动物化石层位、5个化石地点。最下部化石层含有典型的始新世Ergilian期哺乳动物 ,其余两个层位的化石均属早渐新世Shandgolian期哺乳动物。因此 ,该剖面为一Ergilian Shandgolian(晚始新世—早渐新世 )过渡时期的地层剖面 ,是进一步研究该过渡期哺乳动物群替代及Ergilian/Shandgolian地层界线的理想剖面。     

Feeding ecology of the tufted puffin (<Emphasis Type="Italic">Lunda cirrhata</Emphasis>) and the horned puffin (<Emphasis Type="Italic">Fratercula corniculata</Emphasis>) in the northern Sea of Okhotsk

The feeding of tufted puffin and horned puffin nestlings was studied on two islands of Tauyskaya Bay of the Sea of Okhotsk: at Talan Island in 1999–2004 and 2006 and Umara Island in 1994 and 1996–1997. The composition of the puffin diet during the breeding season was determined. The main fish species in the diet were determined and the seasonal and annual dynamics of the occurrence of the items was analyzed. Comparative data on biological characteristics, such as the size, weight and age of the fish caught by these birds, as well as the size and composition of food samples, were collected. Differences between the age groups of fish in the diets of the two puffin species were revealed. Conditions for forming of seabird feeding base in Tauyskaya Bay were described.     

Influence of sediment on burrowing by the soldier crab Mictyris longicarpus Latreille

This study analyses the spatial distribution of burrowing by the soldier crab Mictyris longicarpus (Mictyridae) in relation to the topography of intertidal sandflats. Four different locations were sampled in Port Jackson and Botany Bay (Sydney, New South Wales, Australia). In each location, abundances of crabs and the proportion of juvenile crabs varied among sites 50 m² and tens of metres apart, but not between high- and lowshore levels, nor among shores. Topographic formations, referred to as humps and depressions, were common on the flats and were of the same order of size and spacing as the sites, which showed variation in numbers/sizes of crabs. Manipulative experiments were done in one of the locations to distinguish between the hypotheses that the spatial distribution of the crabs varied according to (1) topography, or (2) the composition of sediment in the different topographic features. In the first experiment, small plots (0.09 m² and 20 cm deep) of sediment were transplanted between humps and depressions, including appropriate controls for disturbance and translocation. The numbers and sizes of crabs colonizing the experimental plots were then measured. Differences in abundance among plots were found higher on the shore. Therefore, the experiment was repeated at highshore levels with increased replication. There were more crabs in depressions than in humps. The proportion of juveniles varied according to the type of sediment, but only in depressions. Heterogeneity and sediment were, therefore, important for explaining some of the spatial variability of the abundances of the crabs.     

Trophic Structure of Benthic Macroinvertebrate Communities from Lakes with Various Water-Salinity Levels

The trophic structure of benthic macroinvertebrate communities in lakes varying in salinity levels (from oligohaline to hyperhaline) in the southern Ob–Irtysh interfluve has been investigated. Four trophic groups of macroinvertebrates have been identified in 48 lakes: (1) predators, (2) grinders, (3) scrapers, and (4) collectors–detritophages and facultative filter feeders. It is found that the proportion of different trophic groups in taxonomic composition and biomass of macroinvertebrate communities changes with increasing water salinity in lakes.     

Urea is a dynamic pool of bioavailable nitrogen in coral reefs

Urea may be an important source of nitrogen in low nutrient coral reef environments because corals and other organisms can assimilate it easily and it is found throughout ocean waters. We measured the distribution and concentrations of urea in seagrass beds, areas of schooling fish, coral formations and bottom sediments in the Upper Florida Keys Reef Tract. The flux of urea from bottom sediments was also measured. Ambient concentrations of urea in the offshore reefs were similar to the concentrations of nitrate and ammonium. Seagrass beds, areas of schooling fish and coral formations had elevated concentrations of urea that were up to eight times higher than nitrate in the system. Numerous ephemeral hotspots of urea that were 8–20 times the ambient urea concentration existed in seagrass beds, areas of schooling fish, and above sediments. Coastal areas and inland canals had high urea concentrations where urban runoff and septic effluents were prevalent, but there was no anthropogenic influence in the offshore habitats. Urea concentrations above bottom sediments were not different from ambient concentrations and benthic flux chamber incubations showed biological activity in carbonaceous sediments but no net urea production. The decrease in urea concentrations from coasts and inland waterways to a consistent ambient concentration in the offshore reef system and ephemeral hotspots of high urea concentration suggest that urea is a dynamic pool of bioavailable nitrogen in the reefs of the Upper Florida Keys.     

基于周丛藻类群落结构的新疆额尔齐斯河生态健康评价

周丛藻类对水环境变化较为敏感,可迅速而灵敏的反映水质健康状况。本研究于2019年对额尔齐斯河周丛藻类群落结构和水环境特征进行了系统调查,并运用周丛藻类生物完整性指数(Periphytic algae index of biotic integrity, P-IBI)对生态健康进行了评价。结果表明:额尔齐斯河周丛藻类有6门41属102种,以硅藻门为主。周丛藻类密度和生物量的时间变化趋势为:9月>7月>5月,空间分布趋势为中下游>上游、支流>干流。主成分分析(PCA)与典范对应分析(CCA)显示,影响周丛藻类群落结构的主要环境因子有水温、溶解氧、高锰酸盐指数、氨氮、硝酸盐氮、pH、悬浮物,不同月份的环境影响因素有所差异。额尔齐斯河周丛藻类多样性指数(H′)、丰富度指数(D)、Pielou均匀度指数(J)的平均值分别为3.52、3.02、0.75,显示额尔齐斯河流域整体水质为寡污或无污。P-IBI分析结果显示:5个采样点为健康状态,1个采样点为亚健康状态,3个采样点为一般状况,1个采样点极差,表明额尔齐斯河整体生态健康状况趋于良好。本研究可为额尔齐斯河的水环境监测提供...     

Dynamics of biological parameters of nonmigratory and invader fish in the basin of the lower Tom’ River

The species composition and dominating complexes of fish in catches are considered. The fraction of mass fish species in catches is shown (for small rivers and the channel zone). The structural (size and age) and functional (fertility) parameters of some nonmigratory and invader fish species are characterized. Main biological parameters are considered in the time-space aspect over the widespread and numerous fish species.     

Fish assemblages of interior tidal marsh channels in relation to environmental variables in the upper San Francisco Estuary

Tidal marsh wetlands represent critical habitat for many estuarine fishes and are particularly important to conserving and restoring native and at-risk species. We describe the seasonal and regional variation in the composition and abundance of fishes in interior tidal marsh channels in the upper San Francisco Estuary (SFE), and relate these to variation in environmental conditions. Fish were sampled quarterly using modified fyke nets from October 2003 to June 2005 in 18 interior tidal marsh channels spanning 3 distinct river systems: Petaluma River, Napa River and West Delta. We collected 116 samples and 9452 individuals of 30 fish species. Four non-native species dominated—Mississippi silverside, western mosquitofish, yellowfin goby, and rainwater killifish—with an additional 13 species occurring commonly (represented equally by natives and non-natives, residents and transients). Large seasonal differences in composition and abundance of fishes occurred, with the lowest abundances in winter and spring and highest abundances in summer and fall. Correlation of ordination scores and environmental variables further supported the importance of season, as well as fish species’ status (native vs. non-native), feeding preference (pelagic vs. demersal), and marsh utilization (resident vs. transient), as factors influencing fish assemblage composition. The proximity of the marsh systems to freshwater and marine influences, which largely control salinity and temperature variation, explained 26% of the variation in fish composition, while channel geomorphology explained 22%. We recommend that both edge habitat (which may be beneficial to fish foraging success) and the extent of tidal connectivity (which allows access for fishes), in addition to location along the estuarine gradient, be considered in designing and managing tidal marsh restoration.     

Relationship between vegetation and environmental conditions in the northern Pantanal of Mato Grosso, Brazil

This paper analyses the relationship between the distribution of tropical floodplain vegetation and environmental factors such as the soil types, their physical‐chemical properties and inundation dynamics in the northern Pantanal of Mato Grosso, Brazil. Fifty‐four soil profiles of the four principal geomorphologic units of the lowland were classified into twenty‐one units of the FAO‐UNESCO system and related to eight vegetation formations. Under the deciduous and semideciduous woodland and forest formations on flood free riverbanks and relict dunes Arenosols, Solonetz and Alisols dominate. Inundation forests grow on a large variety of soil groupings such as Alisols, Solonetz, Fluvisols, Gleysols and Cambisols, mainly on fluvial deposits. Under the grassland formations of periodically flooded spreadings and depressions Planosols, Acrisols, Alisols, Fluvisols, Arenosols and Cambisols were cored, while Gleysols are common on swamps bearing Thalia geniculata or Cyperus giganteus. Canonical Correspondence Analysis was applied to study the influence of monitored environmental factors on spatial distribution of vegetation formations. Water regime and soil texture were found to define the grassland‐forest boundaries as well as the transition between different grassland formations and between seasonal as well as evergreen forests.