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1.
Abstract –  The objective of this study was to quantify fish species diversity in Terra firme streams of the Río Amazonas drainage. Fish diversity was quantified as the number of species collected or species richness in two sites of Yahuarcaca stream, a typical, first order tributary of the central Río Amazonas near Leticia (Colombia). The extremely high species richness recorded, 131 and 133 for the two study sites for a total of 171 species, was primarily due to species of low abundance (rare species) mostly with adults <5 cm in total length. The nonasymptotic tendencies of accumulated species richness over time for the 1999 samples at the two study sites and for the combined samples of 1999, 2001 and 2005 at site 2 suggested that the real number of fish species may be still greater. These findings emphasise the importance of long-term sampling designs to quantify species richness in these systems. Terra firme streams actually sustain greater fish richness than previously reported for similar sized streams that in turn, represent a substantial per cent of the total species richness reported for vast areas of the main stem of Río Amazonas including tributaries and lakes. Terra firme streams should be considered critical hotspots for conservation and management efforts which are urgently needed given the rapid development of ornamental fisheries on small streams throughout Río Amazonas drainage.  相似文献   

2.
Rotenone sampling is the most efficient method for assessing the fish assemblage structure and species abundance of low conductivity Amazonian streams. It does, however, cause fish mortality and disturb aquatic ecosystem. The aim of this study was to search for a non‐destructive alternative. The efficiency of electrofishing was compared against complete removal using rotenone. This procedure was repeated in 12 streams dispersed throughout French Guiana to test for environmental and biological effects such as water conductivity, stream depth, fish family membership and body size. This study revealed that the efficiency of electrofishing was influenced by stream conductivity and stream depth, but not by fish family or body size. The electrofishing method might constitute an efficient alternative to using rotenone in smaller streams (below 25‐cm depth and above 43 μS cm?1), whereas in deeper and/or slightly conductive streams, rotenone still remains the only method able to provide a quick and comprehensive picture of the fish assemblage.  相似文献   

3.
The EU Water Framework Directive (WFD) obligates authorities to assess the ecological status of rivers. The sampling of the fish assemblage must be based on a reliable and cost‐effective monitoring programme, and it should be optimised to measure the ecological quality cost‐effectively. The efficiency of single‐pass versus three‐pass backpack electric fishing was measured to assess ecological status. The data included 295 electric fishing samplings from 137 rivers in Finland and a 5‐year data series from six small forest streams in mid‐eastern Finland. Compared with three‐pass electric fishing, single‐pass electric fishing in the same area increased the risk of missing rare fish species and species with low catchability. The concordance of the calculated fish metrics (e.g. proportion of tolerant and intolerant species) between one‐ and three‐pass measurements was, however, high, suggesting that single‐pass electric fishing was a suitable sampling procedure to evaluate ecological status. Increasing the area sampled by single‐pass removals stabilised the variances in the fish metrics and similarity indexes. It was concluded that in small streams electric fishing an area 24–27 times the stream width and in general a minimum of 300 m2, but preferably more than 450 m2, was adequate to estimate fish assemblage attributes reliably in boreal streams.  相似文献   

4.
Electrofishing in streams of low water conductivity has technical limitations leading to the widespread use of poison fishing. In theory, provided a high enough voltage gradient can be created in water, electrofishing should be possible in all but the lowest of conductivities (<10 µS/cm). Using custom‐made equipment delivering up to 1,500 V DC, tests were carried out in French Guiana on 27 streams with water conductivity as low as 16 µS/cm. Approximately 5,800 fish of 93 species were captured, with an electrofishing mortality rate of 1.83%. Poison treatments were used within enclosed sections to assess how efficient multiple pass electrofishing removal is when assessing species richness and population number. The Chao II estimator on 2 electrofishing passes gave the best results for species richness, but rare species can elude electrofishing. Estimates of total fish abundance (i.e. all species pooled) were possible with the use of depletion models. Capture efficiencies by species were highly biased, however, and abundance could be underestimated for the most difficult species to catch. These results show that with the right equipment and settings, electrofishing can be an efficient alternative to poison fishing surveys in small tropical streams of low water conductivity but high biodiversity value.  相似文献   

5.
2013年7-8月对大别山皖河河源1～3级溪流的鱼类进行了调查,着重从河流网络体空间尺度研究了鱼类多样性及群落结构的空间格局,探讨了局域栖息地条件和支流空间位置对鱼类群落的影响.1～3级溪流间,鱼类物种数随溪流级别增大显著增多,但个体数无显著变化(P＞0.05);长河、潜水和皖水3条支流间鱼类物种数和个体数均无显著差异(P＞0.05).鱼类物种数受局域栖息地条件(海拔)和支流空间位置(河流级别和下游量级)的联合影响,但鱼类个体数仅受局域栖息地条件(海拔)的影响.不同溪流级别和不同支流间的群落结构均无显著差异(P＞0.05).同物种数类似,鱼类群落结构也受局域过程(海拔)和空间过程(汇合量级和下游量级)的联合影响.本研究表明,总体上皖河河源溪流网络体中的鱼类群落是局域过程和空间过程联合作用的产物.因此,为合理保护和管理皖河河源的溪流鱼类物种,有必要兼顾局域栖息地条件与河流网络连通性的保护和恢复.  相似文献   

6.
Hydropower plant operation can lead to direct impacts on fish near the dam, causing injuries and death. In Brazil, it is more common to observe these impacts in the tailrace. To understand temporal and spatial variations in fish abundance in the tailrace, to assist plant operation management, surveys were performed in Três Marias Hydropower Plant using hydroacoustics and multimesh gillnets. Data were collected in the tailrace backwater over 1 year, during 18 field trips, each covering a 24‐h cycle with six sampling intervals. A greater abundance of fish was found in the tailrace during the wet season, mainly explained by total discharge. More fish were detected by hydroacoustics and gill nets during night sampling. Siluriformes, which are known to exhibit nocturnal habits, were the predominant species in both dry and wet seasons. Thus, damaging operational procedures for fish should be planned in the dry season, low‐abundance period.  相似文献   

7.
Pires DF, Pires AM, Collares-Pereira MJ, Magalhães MF. Variation in fish assemblages across dry-season pools in a Mediterranean stream: effects of pool morphology, physicochemical factors and spatial context. Ecology of Freshwater Fish 2010: 19: 74–86. © 2009 John Wiley & Sons A/S
Abstract –  Knowledge of patterns of refuge use by fish is critical for maintaining biodiversity in drought-prone streams. In this study, the fish assemblages of 21 dry-season pools in a Mediterranean stream were characterised and related to three sets of factors reflecting pool morphology, physicochemistry and spatial context. Fish were associated with the three sets of variables, with variation partitioning indicating that overall species richness and abundance were primarily related to pool morphology but relative species abundances were mainly associated with physicochemical contexts. In general, species richness was the highest but overall fish abundance was the lowest in large pools. Pools well shaded by riparian canopy held the highest richness and abundance of native fish, but relative species abundances and assembly structure varied among pools contingent on canopy cover, substrate composition and spatial location. These results suggested that conservation of fish diversity in Mediterranean streams requires networks of pools with diverse sizes and physicochemical contexts.  相似文献   

8.
Invasive macrophytes usually increase the homogenisation of habitats and can affect local communities with negative effects on the food chain. We evaluated experimentally the composition, density, richness and diversity of the invertebrates in the invasive macrophyte Hydrilla verticillata and assessed the potential effects of this macrophyte on the diet and foraging efficiency of small native fishes. The native macrophyte Egeria najas was used as control, since it has very similar physical structure and physical complexity to H. verticillata. Macrophytes of both species were maintained separately in aquaria with the fishes, and the invertebrates richness and abundance associated with plants and within fish stomach were evaluated. No significant difference was found in the richness and diversity of invertebrates attached to macrophytes; however, the two macrophytes differed in regard to invertebrate composition, and the density was significantly higher in H. verticillata. The fish foraging efficiency was high in both macrophytes, and the difference between them was not significant. The fish diet did not differ significantly between the native and the invasive macrophyte in respect to invertebrate composition, abundance and richness, and trophic niche breadth. We found no evidence that H. verticillata negatively affects the density of associated invertebrates, and as a consequence, fish diet and foraging efficiency. Our results indicate that the replacement of E. najas by a similar biomass of H. verticillata does not affect the feeding behaviour of associated fish species.  相似文献   

9.
  • 1. The status of host fish populations and fish species richness was investigated at 36 sites of 20 extant freshwater pearl mussel populations, including the drainages of the Elbe, Danube, Rhine, Weser, Aulne, Kemijoki and Tuuloma in Germany, the Czech Republic, France and Finland, by carrying out comparative electrofishings.
  • 2. Brown trout (Salmo trutta f. fario) were found to be the available host fish for pearl mussels in all except one of the streams investigated with mean densities of 2861 ha?1 (range 0–8710 ha?1) and a mean biomass of 119 kg ha?1 (range 0–478 kg ha?1). Streams that had been frequently stocked with brown trout had higher trout biomass and densities of host fish than natural populations, but trout stocking had no positive effect in two of the streams investigated.
  • 3. Fish species richness ranged from 2 to 16 species per stream and showed a negative correlation with host fish biomass and host fish densities. Undisturbed oligotrophic pearl mussel headwater streams usually only yielded a low number of fish species. Habitat degradation can reduce competitiveness of specialized trout and result in an increased abundance of ubiquitous or atypical species.
  • 4. A link between the lack of juvenile pearl mussels and a lack of suitable host fish was only rarely observed. Functional pearl mussel populations with relatively high numbers of juveniles had significantly lower densities and biomass of host fish than pearl mussel populations without recent recruitment.
  • 5. This study suggests that 0+ host fish are not necessarily required to sustain functional pearl mussel populations. Low densities of host fish can be compensated by the higher glochidia carrying capacity of older host fish with limited previous contact with pearl mussel glochidia, by the long reproductive period of mussels, and by low mortality rates of juvenile mussels during their post‐parasitic phase.
Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

10.
Abstract Diel changes in littoral fish assemblage were studied in four reservoirs in the Czech Republic (Central Europe). The sampling was performed by beach seining in an unstructured littoral zone. Perch, Perca fluviatilis L., roach, Rutilus rutilus (L.), bream, Abramis brama (L.), carp, Cyprinus carpio L., ruffe, Gymnocephalus cernua (L.), pikeperch, Sander lucioperca (L.), eel, Anguilla anguilla (L.) and A. brama × R. rutilus hybrids exhibited higher densities at night. Only bleak, Alburnus alburnus (L.) exhibited higher densities during the day. The number of species was higher in night hauls, and mean body size of roach and bleak was also higher at night. Diel changes in fish densities resulted in the change in species composition between day and night. The study has implication for the sampling design to assess littoral fish assemblages using beach seine netting and recommends night sampling for a representative assessment or sampling during both diel periods for a robust assessment.  相似文献   

11.
Originally developed to assess the relative abundance of ≥1+ fishes in large rivers, point abundance sampling by electrofishing (PASE) was adapted for 0+ fishes in the mid‐1980s. Being both economical and widely applicable, PASE for 0+ fish has become a commonly used sampling approach in Europe, but its use for estimating 0+ fish density and species richness has attracted particular concern because of size and species selectivity. As such, this review is both timely and necessary. It summarizes the development of PASE and evaluates its various applications: studies of 0+ fish community composition, relative abundance and density, species richness (S), population size structure, larval and juvenile growth dynamics, microhabitat use, diel dynamics of species–species and species–microhabitat interactions, and the analysis of data emanating from PASE databases. The use and potential misuse of replicate sampling in estimates of S are examined, with PASE data from various European rivers re‐analysed to assess geographical patterns in 0+ fish S. Comparisons of PASE and other approaches for estimating 0+ fish density and species richness have all demonstrated PASE to be cost‐effective and relatively reliable, but sampling accuracy and precision do decrease as fishes enter the juvenile period of development.  相似文献   

12.
Few studies have been conducted to evaluate the effectiveness of nature‐like fishways, particularly in low gradient warmwater streams with diverse fish communities. We evaluated a nature‐like fishway that was installed to facilitate upstream passage at a low head dam on Indian Creek near Spencerville, Ontario, Canada. A passive integrated transponder (PIT) array was used to quantify attraction and passage efficiency for 391 PIT tagged warmwater fish, represented by seven species. Attraction efficiency for the three most common species, common shiner (Luxilus cornutus), creek chub (Semotilus atromaculatus) and white sucker (Catostomus commersonii), was 63.3%, 83.7% and 65.6%, respectively, and passage efficiencies were 5.1%, 38.4% and 25%, respectively. Creek chub were able to locate the fishway in less time than white sucker and common shiner; however, took longer to successfully pass. Manipulation of creek chub release locations was used to separate issues of attraction and passage and revealed that passage efficiency was highest (76.2%) for those released within the fishway and intermediate for those released at the entrance (42.1%). This multispecies fishway improved stream connectivity, but additional work is needed to fine tune its configuration. Similar projects that engage stakeholders in nature‐like fishway construction are a promising approach for the thousands of small dams that occur on low gradient streams around the globe, but those studies should incorporate a biological evaluation to ensure that attraction and passage efficiency are optimised.  相似文献   

13.
  1. The delimitation of conservation units may be supported by information on compositional (taxonomic), functional, and phylogenetic diversity of a given locality or region. In this context, systematic conservation planning and key biodiversity areas are promising approaches for biodiversity protection.
  2. Factors such as species representativeness and exclusivity may be used to identify geographical distribution patterns and select relevant areas for conservation at a local scale.
  3. This study aims to identify areas with rare and restricted fish species in mountain streams in Southern Brazil, using a method that unites ecological and biogeographical approaches.
  4. Seven river basins and 152 mountain streams in Southern Brazil were sampled to obtain data on the occurrence and abundance of 115 fish species. The rarity status of each species was determined and endemicity analysis was used to find areas of restricted species (ARS) with three cell sizes.
  5. Using larger cells, continuous areas were identified and supported by a higher proportion of rare fish species. Using smaller cells, discontinuous areas were identified within each of the river basins, where rare and endemic fish species occur. Most of the smaller areas relevant for protecting fish fauna were located outside of conservation units.
  6. Fundamental areas were selected for the protection of fish species in mountain streams in Southern Brazil. Both the method proposed and the areas with rare and restricted fish species identified may be used to support systematic conservation planning and to delimit new priority areas for conservation.
  相似文献   

14.
  1. Detecting rare species is often a necessity for conservation and management, yet challenging for many field survey methods. Environmental DNA (eDNA) is a highly promising solution that has been shown to outperform many established survey methods.
  2. Macquarie perch (Macquaria australasica) is an endangered native species that has declined significantly in range and abundance. Detection of M. australasica was compared with an abundant alien fish species (Oncorhynchus mykiss) using eDNA and three conventional survey methods: gill nets, electrofishing and fyke nets.
  3. eDNA occupancy estimates for both fish species were compared using four different models to investigate what effect these differences have on false positives and false negatives for the rare and common fish species. These models used unadjusted eDNA detections in water samples, eDNA detections that have been screened using a limit of detection method to remove potential false positives, eDNA data supplemented with a second survey method, or eDNA data augmented with sequencing of positive polymerase chain reaction replicates.
  4. eDNA surveying as a single detection method was found to be more efficient and sensitive compared with each capture method separately and combined. Occupancy estimates for the common and rare species did not vary significantly between the four site occupancy-detection models, suggesting that supplementary data may not have as much effect on occupancy estimates compared with other approaches such as temporal or spatial sampling.
  5. We conclude that eDNA outperforms the three established survey methods for both a rare and common freshwater fish species. Although there was no significant effect of augmenting eDNA survey methods with other survey data, additional data may improve confidence in detection, and provide confirmatory evidence for unexpected or new detections of a species.
  相似文献   

15.
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16.
Long‐term fish assemblage monitoring requires investigators account for within‐year variation in species' detection. An occupancy modelling framework is presented that accounts for variation in species presence and estimates the effort required to minimise within‐year variation. Species detections from snorkelling surveys and an electrofishing survey were used in single‐species occupancy models to determine the importance of site and sampling covariates on species' occupancy (psi) and detection probabilities (p). Community occupancy models estimated species richness in light of undetected species. For most species, models including patch size and reach as psi‐covariates had higher support whereas models including patch size and sampling method as p‐covariates had higher support. The number of sites and repeated surveys required to estimate occupancy accurately varied among fish species. Community models suggested that the observed number of species underestimated actual richness as much as 27% and the addition of an electrofishing survey increased estimated richness by 13%.  相似文献   

17.
Abstract  The effects of an extreme flash flood on the native fish assemblages across a Mediterranean catchment in Southwest Portugal were investigated. The fish community structure and habitat were surveyed at 10 sites pre- and post-flood. Overall species richness and rank abundances changed little after the flood, despite there being a consistent decline in the abundance of small cyprinids. Pre- and post-flood habitat correlates of abundance changed for at least some species, and variability in assemblage structure was associated with flood, depth and pH. These results indicate that extreme floods occurring early in the wet season may have little disruptive effects on the overall structure of native fish assemblages in Mediterranean streams, although may at least partially influence population dynamics for some species. Habitat quality and complexity are likely to play a role in mediating species responses to flooding.  相似文献   

18.
Studies of trait–environment relationships provide important tools for the prediction of the response of biological communities to environmental alterations. The Amazon basin presents enormous potential for the development of research on this type of relationship, given the diversity of both its fish fauna and the aquatic ecosystems this fauna inhabits. The present study investigated the association between local environmental variables and the functional traits of fish in 54 streams of six major Amazonian basins. We identified the relationship between the characteristics of the streams (channel morphology, channel habitat units, riparian vegetation cover, large woody fragments and instream cover for aquatic organisms) and fish traits related to locomotion, habitat use and feeding behaviour. The fish fauna of the broader, deeper and more slowly flowing streams was dominated by nektobenthic species that exploit autochthonous resources such as fish and invertebrates. In narrow, fast‐flowing streams, by contrast, there was a predominance of benthic fishes with varying feeding habits, including periphytivorous and invertivorous species. Narrow, shady streams were inhabited by nektonic species adapted for the exploitation of resources from the marginal vegetation. The results of this study contribute to the understanding of the association between the functional structure of fish assemblages and local environmental variables in Amazonian streams. We hope that these findings will stimulate further research into the natural variation in stream fish assemblages that will ensure the development of more effective management strategies that better protect these important aquatic ecosystems.  相似文献   

19.
Sound decisions on the management of fish stocks depend on knowledge about the species composition, number, biomass and size structure of existing populations. Accordingly, the ability to make solid population estimates is essential. In this study, a 2.15 ha lake was completely drained and the total number of fish was recorded and amounted to 180,915 individuals divided into seven species having a total weight of 1,395 kg. Before the draining, three commonly used methods in fish surveys were applied: multi‐mesh gillnets, point abundance sampling by electrofishing (PASE) and mark–recapture. Following the determination of the actual number and size distribution of each species, we evaluated the efficiency of the methods and found that gillnets caught a relatively high number of species (five out of seven) and thus proved to be the best tool for mapping species richness. However, gillnets were size selective towards larger individuals of perch (Perca fluviatilis) and did not catch roach (Rutilus rutilus) <5 cm. In contrast to gillnets, PASE was very effective at catching YOY fish in the shore zone but selected for larger‐sized roach. In sum, gillnetting proved to be the most accurate method for estimating species composition, PASE also being useful. Overall, mark–recapture provided relatively good estimates of population size but small‐sized (<11 cm) roach proved not to be well suited for mark–recapture surveys. We conclude that the best method(s) surveying fish stocks depends on various factors such as target species, size distribution and the purpose of the survey.  相似文献   

20.
  • 1. Studies dealing with the fish fauna of coastal streams are scarce in the scientific literature, particularly those from Mediterranean climates. Owing to their small size, these systems suffer extreme seasonal fluctuations, following the typical Mediterranean flood–drought cycle and leading to a high risk of extinction to freshwater fish.
  • 2. This work analyses fish distribution in 14 stream stretches belonging to eight basins in the northern sector of the Strait of Gibraltar (southern Spain). Fish–habitat relationships were studied through multivariate ordination techniques at two scales: basin and stretch.
  • 3. A principal components analysis clearly discriminated larger and more sinuous basins from smaller and steeper ones. This ordination was related to the non‐migratory freshwater fish species richness and to the total number of fish species present in the middle reaches of each basin.
  • 4. The main sources of variation in community composition and habitat characteristics in the different stretches were related to a clear upstream–downstream gradient, along which total species richness increased.
  • 5. These small coastal basins are inhabited by two highly endangered species, Andalusian toothcarp (Aphanius baeticus) and Iberian chub (Squalius pyrenaicus), and have similar or higher overall freshwater species richness than larger adjacent basins. The near absences of flow regulation and introduced species make these streams one of the few types of Iberian aquatic system where unaltered fish–habitat relationships can be studied.
Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

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