High temporal species turnover enhances the complexity of fish assemblages in Amazonian Terra firme streams

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.     

Effects of fish species richness and assemblage composition on stream ecosystem function

Abstract –  Biodiversity is declining across aquatic ecosystems because of biological invasions and species extinctions. Because fishes have pervasive effects on ecosystems through species-specific food web interactions, alterations to species and functional richness, and composition of natural assemblages could have negative effects on aquatic ecosystem function. In this study, I tested the effects of fish species and functional richness, and assemblage composition on primary production (PPR), benthic invertebrate density, and benthic particulate organic matter (BPOM) in a 42-day experiment in artificial stream mesocosms. I found that fish species richness and assemblage composition were important predictors of PPR in stream mesocosms. However, the effect of species richness on PPR increased with time, suggesting that richness-related effects might strengthen as the magnitude of community-level interactions increases in ecosystems. There was no effect of fish species or functional richness or assemblage composition on benthic invertebrate densities or BPOM. These data provide additional support that fishes can be important regulators of ecosystem function in aquatic systems, and suggest that positive effects of fishes on ecosystems can be strengthened by increased species richness and composition of the assemblage. This study broadens the applicability of the biodiversity ecosystem-function literature to a new suite of taxa, supporting the overall hypothesis that ecosystem functions and services are likely to decline in response to species extinctions.     

Electrofishing efficiency in low conductivity neotropical streams: towards a non‐destructive fish sampling method

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.     

基于CART算法的长江口鱼种丰富度预测

长江口是西太平洋最大的河口生态系统和典型的生态群落交错区,预测鱼类生物多样性对评价其生态系统有着重要的科学指示意义。结合2012―2013年长江口15个站点的渔业资源和环境调查数据,利用分类与回归树(CART)算法中的回归树算法,构建了长江口鱼种丰富度预测模型。基于1-SE准则,最优决策树的复杂性参数设置为0.067,结果表明,盐度、溶解氧和季节是影响长江口鱼类生物多样性的主要因子。此外,使用2014年的观测数据对回归树模型预测的长江口鱼种丰富度予以验证,均方根误差(RMSE)、平均相对误差(ARE)和平均绝对误差(AAE)值的统计结果显示,回归树模型在春、夏季的预测效能优于秋、冬季,模型总体上呈现出了较好的预测能力,表明利用CART算法对长江口鱼种丰富度进行预测是可行的。     

Patterns of diel activity and species richness in young and small fishes of European streams: a review of 20 years of point abundance sampling by electrofishing

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.     

Concurrent assessment of fish and habitat in warmwater streams in Wyoming

Abstract  Fisheries research and management in North America have focused largely on sport fishes, but native non-game fishes have attracted increased attention due to their declines. The Warmwater Stream Assessment (WSA) was developed to evaluate simultaneously both fish and habitat in Wyoming streams by a process that includes three major components: (1) stream-reach selection and accumulation of existing information, (2) fish and habitat sampling and (3) summarisation and evaluation of fish and habitat information. Fish are sampled by electric fishing or seining and habitat is measured at reach and channel-unit (i.e. pool, run, riffle, side channel, or backwater) scales. Fish and habitat data are subsequently summarised using a data-matrix approach. Hierarchical decision trees are used to assess critical habitat requirements for each fish species expected or found in the reach. Combined measurements of available habitat and the ecology of individual species contribute to the evaluation of the observed fish assemblage. The WSA incorporates knowledge of the fish assemblage and habitat features to enable inferences of factors likely influencing both the fish assemblage and their habitat. The WSA was developed for warmwater streams in Wyoming, but its philosophy, process and conceptual basis may be applied to environmental assessments in other geographical areas.     

Simulation of over-exploitation of ornamental fish and its consequences for the functional structure of assemblages of Amazonian streams

The consequences of over-exploitation may seriously impair the integrity and functioning of ecosystems. When loss of species is accompanied by the loss of ecological processes, the effects are no longer just taxonomic and may affect the stability of the environments. Ornamental fishing is one of the main economic activities of the middle Negro River. Such activity is directed to a small number of species and has the Cardinal Tetra (Paracheirodon axelrodi) as the main target species. Given the potential effects this pressure and the lack of information on its consequences, the present study analysed, through simulations, the possible effects of depletion of ornamental fish populations on the functional structure of fish assemblages, represented by functional diversity (FD) and functional redundancy (FR) indexes. We sampled 13 streams exploited by the ornamental fishery, where we collected 4,286 specimens of 110 species, of which 22 were targeted as ornamental fishing. We found that the ornamental species corresponded, on average, to 27.8% of the species and 33.3% of the FD of the assemblages. In a scenario of complete exclusion of ornamental species, local communities would lose 24.6% of the FD and reduce up to 12% of the FR. With these results, it is possible to infer that the local extinction of exploited species would cause negative impacts on the multifunctionality and the resilience of the streams ecosystems. In this way, we emphasise the need for proper management of the ornamental fisheries aiming to the sustainability of the activity and to the conservation of ecosystem functionality.     

The status of host fish populations and fish species richness in European freshwater pearl mussel (Margaritifera margaritifera) streams

• 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.     

Influences of local habitat and stream spatial position on fish assemblages in a dammed watershed,the Qingyi Stream,China

Abstract – Identifying the underlying mechanisms that explain the spatial variation in stream fish assemblages is crucial for the protection of species diversity. The influences of local habitat and stream spatial position on fish assemblages were examined from first‐order through third‐order streams within a dammed watershed, the Qingyi Stream, China. Based on linear regression models, the most important environmental variables influencing fish species richness were water temperature and wetted width, but stream spatial position variables were less important. Using canonical correspondence analysis, five environmental variables were identified to significantly influence fish assemblages, including three habitats (elevation, substrate and water depth) and two spatial variables (C‐link and Link). Our results suggest that, in a heavily dammed watershed, by blocking the migration routes of fishes, dams weaken the influence of stream spatial position on fish species richness. However, fish species compositions are significantly influenced by both local habitat environment and stream spatial position, which is perhaps owing to the distribution of fish species according to ecological requirements not related to spatial processes.     

利用非参数方法估计山东半岛南部海域秋季游泳生物群落物种丰富度

为减少渔业资源物种丰富度观测的偏差,以山东半岛南部海域为例,根据2016年10月对该海域进行的底拖网调查数据,运用Chao、一阶刀切(Jackknife1)、二阶刀切(Jackknife2)和自助法(Bootstrap)4种非参数方法估算了该海域鱼类群落物种丰富度,并探讨了影响非参数方法估算的因素及非参数方法的应用。结果表明,4种非参数方法估算鱼类群落物种数目呈现出Jackknife2ChaoJackknife1Bootstrap,依次为265种、248种、235种、206种;不同估算方法的标准差范围有较大差别,Chao最大,Jackknife居中,Bootstrap最小。通过MDS多维标度排序将该海域划分两个群落,两群落物种数有显著差异,群落Ⅰ物种数目估计值为250种、238种、219种、191种,群落Ⅱ物种数目为86种、100种,4种非参数估算方法在不同群落表现基本一致。综合比较不同群落的物种估算结果,认为采样强度是影响4种非参数估计方法表现优劣的主要因素,采样充足是使用非参数估计方法的前提。本研究为不同采样努力量下物种丰富度的比较提供了方法参考和比较标准。     

Restoring connectivity for migratory native fish in a New Zealand stream: effectiveness of retrofitting a pipe culvert

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Distribution and richness of diadromous fish assemblages in Western Europe: large-scale explanatory factors

Abstract –  The aim of this study was to analyse the distribution of 14 diadromous fish at the beginning of the 20th century in western Europe. This study was conducted on a set of 41 water basins. Five environmental variables were selected and we used generalised additive models for explaining the presence–absence of species. The richest basins were located in the centre of the study area. Six main assemblage types were identified along a latitudinal gradient; they were constituted of a common species basis but differed by the absence or presence of other species. The 10 single species models produced have moderate to very good discrimination level and they can correctly predict both absence and presence. Temperature is included in all but one model, response curves vary according to the species; surface area is included in six models.     

基于多目标鱼种资源量指数估计的不同采样设计比较

经济高效的渔业资源调查采样有利于保证调查数据的质量,提高调查效率,从而为渔业科学研究提供可靠数据.根据2016-2017年山东近海渔业资源底拖网季度调查数据,以小黄鱼、矛尾虾虎鱼、方氏云鳚和星康吉鳗作为目标鱼种,使用Kriging插值法模拟了目标鱼种在4个季节的相对资源量分布,设置简单随机抽样(SRS)、常规系统抽样(...     

Controls of local young-of-the-year fish species richness in flood plain water bodies: potential effects of habitat heterogeneity, productivity and colonisation–extinction events

Abstract –  This study reports on the relationships between young-of-the-year (YOY) fish species richness and landscape and local factors in 20 backwaters of the Seine River flood plain. Using multiple linear regression, we tested the importance of three types of variable for explaining total species richness (TSR), phytophil species richness (PSR) and lithophil species richness (LSR): (1) colonisation–extinction processes, (2) habitat heterogeneity and (3) productivity. At the local scale, no variables describing habitat heterogeneity correlated with TSR, PSR or LSR. Productivity was correlated only with TSR according to a polynomial model. In contrast, variables relating to the colonisation–extinction process correlated with TSR, PSR and LSR: TSR varied mainly with backwater size, which is a surrogate of extinction, whereas PSR and LSR correlated with the relative longitudinal position of backwaters and the size of their connection to the main channel. In conclusion, it seems that the total fish richness varies as a function of local factors, whereas the components of fish diversity are rather influenced by landscape factors.     

Responsiveness of fish mass–abundance relationships and trophic metrics to flood disturbance,stream size,land cover and predator taxa presence in headwater streams

Characterisation of food webs, by summarising energy transfer and trophic relationships, allows more functional measurement of ecosystems and may reveal threats (e.g., land‐cover change) in sensitive environments that are not obvious from conventional biomonitoring. However, typical methods used to achieve this are time‐consuming and expensive. Therefore, we tested the usefulness of fish‐focused food‐web proxies as functional measures, specifically mass–abundance relationships of fish assemblages and stable isotope (SI)‐derived metrics in headwater stream reaches. These metrics have been trialled before for similar use in other settings, but have yielded varying results, and have not been employed in tandem in temperate freshwaters. Sampling reaches (N = 46) were spread across a variety of streams, and the effects of habitat predictors at multiple scales on metrics were assessed using model selection. We found that habitat size positively correlated with food‐chain lengths in streams, possibly because of increased abundance of fish at multiple trophic levels in habitats with more space. Additionally, flood disturbance was negatively associated with fish mass–abundance and carbon range, likely due to the harshness of flood‐prone streams. Riparian land‐cover variables were correlated with multiple metrics, indicating the importance of terrestrial–aquatic linkages. Additionally, variations in all metrics were influenced by the presence of native, predatory longfin eels. Overall, we conclude that mass–abundance relationships and SI‐derived metrics are sensitive to drivers of trophic organisation and likely reflect processes occurring at multiple spatial scales in freshwaters. Thus, these metrics could be an insightful monitoring tool for managers because they reflect functional measures of aquatic ecosystems.     

Interannual variability in the abundance and composition of spring larval fish assemblages in the Strait of Georgia (British Columbia,Canada) from 2007 to 2010

Spring larval fish assemblages in the Strait of Georgia (British Columbia, Canada) were characterized for the first time based on three spatially extensive field surveys in late‐April of 2007, 2009 and 2010, a period which spanned both warm and cold environmental conditions. The abundance, diversity and community structure of the assemblages were examined to investigate interannual variability, and responses to environmental fluctuations. A total of 49 taxa from 23 families were identified. The dominant taxa were Clupea pallasi, Gadus chalcogrammus, Merluccius productus, Leuroglossus schmidti, Lyopsetta exilis and Sebastes spp. Total larval abundance was much lower in 2009 (c. 32 per 1000 m³) than in 2007 and 2010 (c. 200 per 1000 m³). However, the mean size of individuals from several species was largest in 2009. Assemblage structure varied dramatically; from dominance by M. productus in 2007, to dominance by C. pallasi and G. chalcogrammus in 2009, followed by a shift to dominance by benthic species including Sebastes spp. and several flatfishes in 2010. Variability in assemblage structure among the three study years was primarily related to water temperature, whereas within‐year patterns were more closely associated with salinity and chlorophyll, both of which were affected by estuarine circulation. This study provides baseline information about the status of the larval fish community in the Strait of Georgia in recent years, and offers a better understanding of their short‐term dynamics and response to environmental fluctuations.     

Restoration of a Danish headwater stream: short‐term changes in plant species abundance and composition

1. This paper describes the short‐term effects (2 years) of stream restoration on vascular plant communities in a 1.4 km upper reach of the River Gudenå, Denmark. The effects of restoration were assessed in terms of the abundance and composition of plant species in the stream, on the banks and in the stream valley. 2. Total species richness was similar before and after restoration, and comprised approximately 150 species representing 12% of the entire Danish vascular plant flora. 3. In the stream, total plant cover had not recovered to pre‐restoration levels 2 years after restoration. Cover by submerged, amphibious and terrestrial species growing submerged decreased, as did the number of amphibious and terrestrial species growing submerged. 4. On the banks, total plant cover almost attained pre‐restoration levels the second year after restoration. The plant communities changed from dominance by non‐riparian species to more diverse communities with a greater number and increased cover of riparian gramineous species requiring a higher soil moisture content. 5. In the valley, the plant communities only changed slightly after restoration, although growth of riparian species was enhanced on the southern side of the stream. Copyright © 2000 John Wiley & Sons, Ltd.     

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Seasonal abundance and microhabitat use of bullhead Cottus gobio and accompanying fish species in the River Avon (Hampshire), and implications for conservation

• 1. Five side‐channels and small tributaries of the River Avon (Hampshire, UK) were examined between spring 1999 and spring 2000 using point abundance sampling by electrofishing to determine the status of fish listed in Annex II of the EC Habitats Directive prior to habitat management works to enhance spring feeding habitat of wading birds.
• 2. Seasonal patterns of abundance and microhabitat use of bullhead Cottus gobio and accompanying fish species were examined. Parr of Atlantic salmon Salmo salar were sufficiently abundant for microhabitat analysis at one site only. Only two specimens of brook lamprey Lampetra fluviatilis were observed, one at each of two sites. Bullhead was amongst the most abundant fish species at all five sites, 0+ bullhead predominating.
• 3. Bullhead microhabitat preferences were generally similar at all five sites, but seasonal variations were observed, as was the case for the accompanying fish species, which included dace Leuciscus leuciscus, chub Leuciscus cephalus, stone loach Barbatula barbatula, roach Rutilus rutilus, and threespine stickleback Gasterosteus aculeatus.
• 4. Bullhead conservation status is discussed, in particular the possible exemption of British bullhead populations, such as already granted for those of Finland, from Annex II of the Habitats Directive.

© Crown Copyright 2004 Reproduced with the permission of Her Majesty's Stationary Office. Published by John Wiley & Sons, Ltd.     

Is scuba sampling a relevant method to study fish microhabitat in lakes? Examples and comparisons for three European species

Abstract – We compared fish microhabitat use patterns in the littoral zone of a lake using a new direct method (point abundance sampling by scuba, PASS) and the widely used point abundance sampling by electrofishing technique (PASE). We collected microhabitat data for age 0+ roach ( Rutilus rutilus L.), perch ( Perca fluviatilis L.), and pike ( Esox lucius L.). The two methods yielded different results for fish assemblage structure and microhabitat patterns. Using PASE, fish were mainly found in "shelter habitats" such as shallow waters and dense vegetation. It is likely that this behavior is caused by the disturbance of the observer stamping around. Using PASS, fish escapement behavior was rarely observed. Therefore, we concluded that this direct and nondestructive sampling technique can be used to provide an accurate microhabitat estimation of a fish community and is assumed to be more suitable than PASE for fish habitat studies.