Distribution of fish in the Virgin River,a tributary of the lower Colorado River

Synopsis The Virgin River, a major tributary of the lower Colorado River, contains a unique, though impoverished, native ichthyofauna (six species) that is largely intact despite the introduction of exotic fishes (13 species) and alterations of the river. The main conclusions of the study are: (1) The longitudinal distribution pattern of the native species does not follow theoretical expectations of a downstream increase in species richness; (2) for the size of the basin (>15,000 km²), the native ichthyofauna is extremely depauperate; and (3) most of the exotic fish are not established in the river, but persist through repeated invasions from downstream reservoirs.     

Reproduction, Growth, and Migration of Fishes in a Regulated Lowland Tributary: Potential Recruitment to the River Meuse

Many European rivers are characterized by a canalized main channel, steep stony embankments, the absence of aquatic vegetation, regulated flow dynamics, reduced hydrological connectivity to the floodplains and a lack of spawning and nursery areas for many fish species. In such regulated rivers, tributaries may be particularly important for recruitment of fish populations in the main channel. This paper describes the reproduction, growth and migration of fishes in the Everlose Beek, a regulated lowland tributary stream of the river Meuse (The Netherlands), using bi-weekly sampling from January to December 2002. A total of 8615 fishes were caught, belonging to 13 different species. The fish species were classified into three groups, viz., residents, migrants and transients, based on the presence of various life-stages in the tributary. Size-frequency data suggest that each group uses the Everlose Beek differently: (i) Stone loach (Barbatula barbatula), Gudgeon (Gobio gobio) and Three-spined stickleback (Gasterosteus aculeatus) were resident species using the tributary as a spawning, nursery and adult habitat; (ii) Bream (Abramis brama), Roach (Rutilus rutilus), Rudd (R. erythrophthalmus), Tench (Tinca tinca), and Pike (Esox lucius) were migratory species, using the tributary as a spawning area, as well as a nursery habitat during their first year of growth, but migrating towards the river Meuse typically at a length of 5–15 cm; and (iii) Bleak (Alburnus alburnus), Sunbleak (Leucaspius delineatus), Carp (Cyprinus carpio), Crucian carp (Carassius carassius), and Perch (Perca _,fluviatilis) were transient species, characterized by an absence of reproduction, ^.and the occurrence in very low densities of >age-1 juveniles and adults only. Lowland tributaries, such as the Everlose Beek, can contribute to the recruitment of particularly migrant species, hence contributing to fish populations of the regulated river Meuse.     

Using 18O/16O data to examine the mixing of water masses in floodplain wetlands

Oxygen isotopic data were used to assess how far waters from the Savannah River, a major river in the Southeastern United States, backed up and inundated the wetlands along a small Coastal Plain tributary during a flood. This approach worked because the water of this tributary, Unper Three Runs, had an oxygen isotopic composition (¹⁸O = –4.9 ) distinct from Savannah River water (¹⁸O = –3.2 ).Two sample surveys were taken from the mouth of Upper Three Runs to 2 km upstream. Waters were isotopically uniform along the length of the sample transect when both river and tributary water levels were below bankfull. Visual estimates of turbidity taken when both the river and tributary overflowed their channels and inundated adjacent wetlands indicated that Savannah River water extended about 300 meters up the tributary channel. In contrast, the isotopic data indicated that a mixing zone of river and tributary waters extended about 1100 meters upstream. Although this mixing zone was documented only in the channel of Upper Three Runs, it probably extended into adjacent parts of the riparian wetland, potentially affecting ecological processes due to the differing water quality. This study was conducted in a single river-tributary system and the approach is probably applicable in other large rivers.Corresponding Editor: R. SharitzTo Whom Correspondence should be sent     

Distribution,community structure and production of fishes in the upper Speed River,Ontario: a preimpoundment study

Synopsis The upper Speed River, on which a dam was under construction, was surveyed through fourteen qualitative and six quantitative collections to determine the distribution of fishes in the river above Guelph, Ontario and in a tributary, Luteral Creek. At the quantitative localities the removal method was used to estimate density and standing crop of all species. At three of these localities age and growth of the dominant species were determined and total ecological production calculated. Two approaches to the estimation of production for the 0–1 age class were compared and found to result in differences of 33–39% in the estimates of total production, thus illustrating the extent to which methodology may affect such estimates The dominant species in the river were, Semotilus atromaculatus, Notropis cornutus, Pimephales notatus, Rhinichthys atratulus, Hypentelium nigricans, Catostomus commersoni, Ambloplites rupestris, Micropterus dolomieui and Etheostoma flabellare. Density ranged from 11126 to 74765 individuals per hectare and standing crop from 32.4 to 190.0 kg ha⁻¹. Production values at the three localities were 15, 19 and 54 kg ha⁻¹ yr⁻¹ , and are low compared with estimates for other fluvial systems. Comparison with a 1951 survey of the Speed River revealed considerable changes in the composition and distribution of fish species. The ranges of several cold-water species had contracted towards the headwaters, whereas several warm-water species had extended their ranges up the river     

Studies on the Ephemeroptera of a Northumbrian river system

The River Coquet is a clean, fast flowing, moderately calcareous river. It is young to mature in development and supports a typical torrential fauna. Marked trends in successional replacement along the river course are confined to the scarce species of Ephemeroptera and the absence of longitudinal zonation in the distribution of some common species is related to the topographical characteristics of the system. A distinct successional trend by one species is attributed to its intolerance to the lower temperatures at high altitudes. Major discontinuities in distribution are found between the Ephemeroptera of the main river and certain tributaries. The paucity of certain otherwise abundant species in one region is related to silt deposition resulting from sand and gravel excavation.     

Fish behavioural responses to river discharge trends and the importance of habitat connectivity

Population behaviours associated with the migrations of coarse (non‐salmonid) fishes within river basins are amongst the most poorly understood dispersion mechanisms of temperate freshwater organisms, which in rivers are expected to be influenced by river discharge. We examined the timing and intensity of fish movements (via trapping) between the River Avon (Hampshire, England) and a small floodplain tributary, Ibsley Brook, and tested for correlations with trends in river discharge (i.e. mean cm of change in stage during trapping), water temperature and brook water velocity over twelve months in 1999–2000. 0‐group fishes dominated the catches. Intensities of movement between the brook and the river were similar in most months, but seasonal patterns were observed overall and for individual species. Few significant differences in overall numbers of fish were observed between the discharge trends, but many individual species demonstrated differences, mostly as more intense movement under fast rising discharge. Fish numbers in five species were correlated with river discharge trend, and movements in some species were correlated with the rate of temperature change (Δ° C 10 h sampling), and with changes in brook water velocity. Our results suggest daily movements between the river and small tributary brooks are triggered by changes in light intensity and water velocity, whereas seasonal movements of species between the river and brook are driven by changes in river discharge and water temperature, in particular associated with flood events. This study emphasizes the importance of connectivity in river systems, as fish movement between the Avon and its annexes occur under all flow regimes, but especially with rapidly rising discharge.     

Length–weight relationships of fish from Madeira River,Brazilian Amazon,before the construction of hydropower plants

Length–weight relationships (LWRs) are presented for 112 freshwater fish species representing 23 families and five orders captured in the Madeira River, the largest white‐water river tributary of the Amazon River. The allometry coefficient (b) of the LWR (Wt = aSL^b) ranged from 2.446 to 3.856 with a median value of 3.102. Eight new LWR records are presented for Amazonian species as information for FishBase. LWRs in the present study provide historical data on a and b coefficients prior to the damming of the Madeira River in November 2011, allowing comparison estimates of predicted future population parameters as influenced by human intervention.     

Occurrence of the Rhodophycean algaThorea ramosissima Bory in the River Meuse

Recently the red algaThorea ramosissima Bory has been found in three localities in the Dutch stretch of the river Meuse. The species was already known from a number of localities along the river Meuse and its tributary the river Sambre in Belgium. Consequently, the known northern border of the species has shifted considerably. In spite of this there are no clear indications that the species has extended its range. On the contrary it seems more likely that it has been overlooked in the past.Th. ramosissima occurs only on solid substrates in the lower part of theCladophora glomerata (L.) Kütz. belt or deeper, and is characteristic of well-aerated running water.     

鄱阳湖主要入湖段典型底栖动物体内微塑料累积特征

以鄱阳湖-饶河和鄱阳湖-赣江中支两个主要入湖段典型底栖动物(河蚬、圆顶珠蚌、中国圆田螺)为对象,通过组织消解、滤膜过滤分离和显微镜检筛分微塑料(粒径<5mm),分析底栖动物体内微塑料的累积特征。结果表明:三种底栖动物体内均有微塑料淀积且主要淀积于消化道组织中,不同物种淀积丰度表现为河蚬>中国圆田螺>圆顶珠蚌;淀积的微塑料类型包括颗粒类、碎片类、薄膜类和纤维类,其中以纤维类为主;微塑料颜色主要有透明、蓝、红、紫;粒径以<1 mm的丰度最高,且随粒径增大丰度呈递减的趋势;空间尺度上,饶河入湖段底栖动物体内微塑料丰度高于赣江中支入湖段。本研究表明,鄱阳湖微塑料污染已造成底栖动物体内微塑料的累积,湖水产品的食用需要谨慎,但与国内外其他研究相比,本次研究区域的底栖动物处于中等微塑料污染。     

The use of stable isotopes to trace small-scale movements by small fish species

Valuable biological information can be obtained by monitoring the movement of organisms. However, the choice of monitoring method becomes highly restricted when following small organisms (<100 mm), especially in aquatic ecosystems. Stable isotopes are being increasingly used in this respect but rarely at the local spatial scale, i.e. 10–1000 s of metres. We sought to identify movement of small fishes between a main river channel and its tributary. Little overlap in isotope baseline was detected between the two channels despite some temporal variability in δ¹⁵N of baseline indicator organisms in the main river. The individuals of two small cyprinid fish species (Leuciscus souffia and Alburnoides bipunctatus) of all the size classes (40–100 mm) caught within the tributary showed considerable heterogeneity in δ¹⁵N values. Classification and discriminant analysis on isotope-derived data distinguished two significantly different groups. Moreover, this result was supported by further sampling of fish caught in the main river (in May and December 2006). Alternative hypotheses, such as dietary differences, biological factors, temporal shifts and spatial differences in diet, did not explain δ¹⁵N variability. This application of stable isotopes at a relatively small spatial and temporal scales further demonstrates its potential as a tool for ecologists.     

How well are velocity effects on ∂13C signatures transmitted up the food web from algae to fish?

1. Benthic algae fractionate carbon isotopes less at low water velocities because of reduced boundary layer exchange, and this effect on δ¹³C is passed on to consumers via trophic transfer. This study examines the relationships between δ¹³C signatures of consumers (invertebrates and salmonid fishes) and water velocity in the Sainte Marguerite River, QC, Canada, and compares them to patterns for periphyton, both along the river main‐stem and in a small tributary. 2. Relationships of δ¹³C signatures of herbivore/grazers and collector/gatherers with water velocity were strong and similar to those of periphyton, but relationships for filter‐feeders were weak, probably reflecting the effect of spatial averaging of their food supply as a result of downstream transport. 3. Velocity effects on salmonid signatures were much weaker than those of lower trophic levels, being barely significant except in the small tributary where the fish were resident and isolated from the main river. In the river main‐stem, even when reach standardised (reach mean subtracted from each data point), fish signatures were only weakly related to water velocity. 4. The fidelity with which velocity effects are transmitted to consumers from benthic algae is highly variable, and depends on a combination of consumer and resource movements, in addition to the trophic position of the consumer.     

澜沧江梯级开发下鱼类支流生境替代效果

作为干流高坝水电开发导致鱼类生境丧失的一种补偿措施,支流替代生境近年来被广泛应用于受工程影响河段的土著鱼类保护,但替代支流发挥怎样的保护效果及干流对其的影响仍不清楚。以实施了澜沧江梯级生境替代的支流基独河与罗梭江为研究对象,并选择了邻近的对照支流,通过对鱼类调查数据的分析对比,揭示了各支流鱼类种类组成与群落结构的差异特征,初步阐明了梯级开发下鱼类支流生境替代效果以及干流工程建设对其的影响。结果表明：澜沧江支流替代生境对干流鱼类具有明显的保护作用,支流生境修复后鱼类物种丰富度明显提高,罗梭江土著鱼类、特有鱼类物种数分别增加了12种、7种,基独河则是7种、2种,替代生境能为澜沧江土著鱼类、部分濒危特有鱼类和洄游鱼类提供完成生活史的关键栖息地。干流对支流生境替代保护有着重要影响,罗梭江、基独河与邻近干流鱼类群落的Bray-Curtis相似性分别为21.76%、10.73%,支流河口段保持“河相”是支流生境替代保护效果可持续的关键。综合考虑生境替代保护的效益与投入,建议今后开展此类保护措施时优先选择库尾河相区的支流。     

Production of brook charr and ouananiche in a large rapid,tributary of the Caniapiscau River,northern Quebec

Synopsis The age structures of brook charr (Salvelinus fontinalis) and ouananiche (Salmo salar) stocks inhabiting a large rapid the river Méo, tributary to the Caniapiscau River were used to compare population stability and production of these species in north central Quebec. The brook chart stock was stable whereas ouananiche showed considerable variation in year class strength. Stock estimates were not significantly different for the two species although the brook charr estimate was 1.5 that of the ouananiche. Production estimates differed by a greater margin because of different growth patterns. Brook chair production was estimated at 19.4 kg ha⁻¹ yr⁻¹. Above age 2+ it was 11.4 kg ha⁻¹ yr⁻¹ which compares with 4.8 kg ha⁻¹ yr⁻¹ for the same age groups of ouananiche.     

On the spread of the Russian sturgeon Acipenser gueldenstaedtii (Acipenseriformes: Acipenseridae) in the Neotropics: A marine path to invade freshwater drainages in South America?

Acipenser gueldenstaedtii is a species of sturgeon described from Caspian Sea and Black Sea and their tributaries, occurring in the Eastern Atlantic, Europe and Middle East. This and other two sturgeon species have been accidentally introduced in the Rio Negro, Uruguay, a tributary of the Rio de La Plata. Recently, it has been demonstrated the presence and establishment of A. gueldenstaedtii widespread in the Rio Paraná basin, the largest tributary of the Rio de La Plata, corresponding to the second largest river drainage in the Neotropics. We herein register the presence of the species in the next northern freshwater drainage in South America, representing the first record for Brazil. We further discuss the possibility of dispersal through marine environments to other freshwater drainages in South America through the analysis of its documented occurrence and marine ecoregions in southwestern Atlantic.     

Preliminary data on rotifers in the interstitial of the Ninnescah river, Kansas, USA

One-hundred five rotifer species were identified from a sandy, plains river in Kansas, USA (the Ninnescah river). Of those rotifers identified, eighty occurred only in the interstitial sand, fifty-six in only the flow as plankton, and thirty-one from both habitats. Most species can be characterized as being more commonly found in littoral habitats, and not the interstitial or plankton. Lecane inermis (Bryce, 1892) had the highest density in the hygropsammon interstitial with an average 401 ind. 10 cm⁻³ at 1–3 cm depth in September 1993. New records for the US include Encentrum wiszniewski Wulfert (1939), E. longidens Donner (1943) ant E. (Parencentrum) longipes Wulfert (1960). A small form of Lecane levistyla Olofsson (1917) is further examined and discussed.     

Tributary and mainstem benthic macroinvertebrate communities linked by direct dispersal and indirect habitat alteration

Benthic communities in tributary–mainstem networks might interact via downstream drift of invertebrates or material from tributaries and adult dispersal from the mainstem. Depending on the strength of these interactions, mainstem downstream communities are expected to be more similar to tributary communities due to drift or habitat alteration. Communities not connected by flow are expected to be similar due to adult dispersal but decreasing in similarity with distance from the mainstem. We investigated interactions between invertebrate communities of a 7th order river and 5th order tributary by comparing benthic community structure in the river upstream and downstream of the tributary confluence and upstream in the tributary. Non-metric multidimensional scaling showed invertebrate communities and habitat traits from river locations directly downstream of the tributary clustered tightly, intermediate between tributary and mid-channel river locations. In addition, Bray–Curtis dissimilarity increased between the mainstem and tributary with distance upstream in the tributary. Our results indicate that similarities between mainstem and tributary communities are potentially caused by direct mass effects from tributary to downstream mainstem communities by invertebrate drift and indirect mass effects by habitat restructuring via material delivery from the tributary, as well as potential effects of adult dispersal from the river on proximal tributary communities.     

Zooplankton in the Vychegda River

The species composition of plankton invertebrates was studied in the middle Vychegda River (the main tributary of the Northern Dvina River) in 2003–2005. A list of planktonic rotifers and lower crustaceans was made. The dominating complexes of zooplankton organisms were found. The quantitative characteristics of plankton communities in the river were described.     

Invertebrate drift in a glacial river and its non-glacial tributary

1. Invertebrate drift was studied in a glacially fed river and a non-glacial tributary in western Norway. Samples were taken during two consecutive 24-h periods in May, July and October 1997. The 3 months are characterized by snowmelt, ice melt and rainfall runoff, respectively. The main glacial river has colder, more turbid water, especially during the period of maximum ice melt during summer.
2. Chironomidae, especially the genus Diamesa , dominated the drift in the main river in May and October, constituting 97 and 99% of total numbers, respectively. Simuliidae, Plecoptera, Ephemeroptera and Trichoptera were the other main components.
3. A comparison of drift and benthos data revealed that the tributary was of little significance for colonization of the main glacial river. Only some additional species in very low numbers were recorded downstream of the confluence.
4. During July significant differences in diel drift pattern of Chironomidae and Simuliidae existed between the glacial and non-glacial reaches. There was a mid-day peak independent of discharge in the glacial river, but this peak was not noted in the tributary. Species of the genus Diamesa appear to be adapted for daytime drift, possibly evolved through the absence of predators and competitors that are typical of rhithral systems where nocturnal drift is more usual.     

Low tide distribution of wintering waders and shelduck on the Severn Estuary in relation to the proposed tidal barrage

Waders and shelduck were counted at low tide on 162 sectors comprising 85% of the intertidal area (21 467 ha) of the Severn Estuary on 12 occasions during winter 1987/88. On average, 50% of birds present at low tide utilized just 13 sectors (12% of the area); 90% of birds occurred on only 56 sectors, leaving large expanses of intertidal sand virtually devoid of birdlife. Dunlin, the numerically dominant species, occurred widely on the middle and outer estuary, whereas shelduck predominantly occurred on the outer estuary and redshank around many tributary river mouths. Curlew, the most ubiquitous species, was the only one concentrated on the inner estuary. Severe gales in both late December and mid-January concentrated all main species within fewer sectors, probably by the short-term removal of surface sediment from substantial areas. It is estimated that the proposed tidal barrage would eliminate intertidal areas accounting for between c. 40% (for shelduck and curlew) and 80% (for redshank) of current total low tide usage by the internationally important populations present.