Relative influences of catchment‐ and reach‐scale abiotic factors on freshwater fish communities in rivers of northeastern Mesoamerica

Esselman PC, Allan JD. Relative influences of catchment‐ and reach‐scale abiotic factors on freshwater fish communities in rivers of northeastern Mesoamerica. Ecology of Freshwater Fish 2010: 19: 439–454. © 2010 John Wiley & Sons A/S Abstract – While the abiotic factors important to freshwater fish assemblages at a reach scale are well understood, studies of larger scale constraints have yielded variable conclusions, spurring a need for further studies in new biogeographic contexts. This study investigated the importance of catchment‐ and reach‐scale abiotic factors to variation in freshwater fish assemblages in rivers of northeastern Mesoamerica. Abiotic variables and fish data from 72 sampling sites on main stem rivers of Belize were used with partial constrained ordination to determine the proportion of spatially structured and unstructured variation in fish presence and absence, relative abundance, and community metrics explained by catchment‐ and reach‐scale environmental factors. Results showed that, combined, catchment and reach variables explained a large portion of the total variation in the fish assemblage data (54–75%), and that catchment environment explained a greater portion of variation (42–63%) than reach environment (34–50%). Variables representing landscape position (local elevation, watershed area) and their reach‐level correlates (channel width, depth variation, and substrate) correlated strongly to the fish assemblage data. Our results suggest that landscape‐scale factors have a stronger relative influence on assemblages than environmental conditions at the reach scale within our study area. These results contrast with past findings that showed greater local scale influence in landscapes with low anthropogenic disturbance levels. Our findings suggest that biodiversity conservation efforts should consider assemblage variation across a longitudinal gradient, and that a multi‐catchment region is a biologically relevant scale for fish conservation planning and coordination in northeastern Mesoamerica.     

A comparison of electric fishing and gillnetting to examine the effects of anthropogenic disturbance on riverine fish communities

Abstract Quantitative electric fishing and multiple mesh-size gillnetting of fish communities in the Hawkesbury-Nepean River system, near Sydney, were carried out upstream of, within and well below each of three major points of treated sewage effluent discharge. Approximately half of the fish sampled were caught by electric fishing, comprising 515 individuals in 3 h of electric fishing (172 fish per hour). The remaining 439 fish were caught in 72 h of gillnetting (six fish per hour). In total, 16 fish species were collected by electric fishing and only seven species by the gill nets. Differences were found in the total abundances and numbers of species collected by each method in relation to points of treated sewage effluent discharge, but neither community variable showed consistent differences between the areas above, within and well below points of treated sewage effluent discharge in all three river regions. However, classification and ordination of electric fishing catch data produced distinct fish community groups in relation to sewage discharge, while similar analyses of the gillnetting data failed to reveal such differences in community structure. It was suggested that the increased sampling efficiency of electric fishing, both in terms of the number of fish sampled per unit effort and number of species collected, allowed for significant increases in the power of univariate and multivariate analysis methods in detecting such environmental disturbances in large rivers.     

Spatial and temporal patterns in fish community structure and abundance in the largest U.S. river swamp,the Atchafalaya River floodplain,Louisiana

Long‐term monitoring is critical for documenting population and community trends and for management, especially in large river‐floodplain ecosystems that provide important services. Levees have reduced active floodplains in most large rivers, but connectivity in some reaches could promote community resilience. Using multivariate tools and regression, we examined spatial and temporal structure in fish community samples from two decades (>1000 samples, >100 sites) in one of the largest relatively intact river‐floodplain ecosystems in North America – the Atchafalaya River (ARB), Louisiana. Assemblages exhibited significant structure temporally and spatially, with most substantial effects of year and hydrologic subdivisions; however, season and water level also influenced community structure. Temporal trends in communities were limited to few areas, while declines in species richness were more widespread; however, rarefied richness trends suggested that declines were slight. Recent and long‐term declines in abundance of economically important species (e.g., Black Crappie, Largemouth Bass, Bigmouth Buffalo) and increases in others (e.g., Smallmouth Buffalo, Blue Catfish, Freshwater Drum) drove differences among time periods. Our results suggest that the hydrologic subdivisions of the ARB may be an appropriate scale at which to manage fish populations, hydrology and water quality. Although we could not account for several important factors affecting fish communities in the ARB (e.g., hurricanes, major floods), and were limited by sampling variability, our findings highlight the utility of long‐term datasets from large river‐floodplain ecosystems for identifying important scales for management, determining species contributions to community change and forming hypotheses about anthropogenic and environmental drivers of variation in fish communities.     

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.     

Spatial and temporal patterns in fish communities along the Illinois River

Abstract –  Fish abundance data from a fish population study (1957–2000) on the Illinois River, IL, USA were used to assess community structure. There was considerable variability among reaches and years, but three distinct fish communities were identified encompassing both temporal and spatial aspects. Temporal community shifts in the upper half of the river created two distinct fish communities, one prior to 1983 and the other after 1983. This is believed to be in response to improved water quality, albeit the responses were delayed for several years after policy implementation. The third group (Lower River) was spatially separated from the two upper river groups. These differences may reflect a combination of water quality (e.g., pollution) and habitat issues (e.g., geomorphology), common to many regulated rivers. Fish community responses in larger rivers may have considerable temporal lags after implementation of management or restoration activities that warrant strong consideration during any planning process.     

Temporal dynamics of freshwater fish assemblages,their background and methods of quantifications—A synthesis

The temporal dynamics of biotic communities have been widely examined by ecologists. However, systematic reviews on how habitat features, sampling and data evaluation influence temporal patterns are rather sporadic. Here, we reviewed 307 peer-reviewed scientific articles to characterize the methods and the approaches, as well as to identify the knowledge gaps in the assessment of the temporal dynamics of freshwater fish assemblages with special regard to their stability patterns. The number of publications increased exponentially over decades. We revealed a highly uneven distribution of the studies among continents and ecosystems with a dominant number of papers derived from North America and Europe, and from lotic systems, especially. We also found large variability among studies even within similar habitat types in the examined spatial and temporal scales, sampling methods used, examined assemblage attributes, potential stressors and data analyses. Several knowledge gaps, such as the limited number of large-scale studies, the insufficient knowledge on the long-term dynamics of early life history stages and on trait-based assemblage organization, were highlighted. For enabling meaningful comparisons of fish assemblage dynamics in space and time, further developments in standardization procedures are needed across sampling and data evaluation possibilities. Publicly accessible long-term data sets with more details on sampling and environmental parameters would also be critically important to determine the effect of a variety of factors on the stability vs. variability of fish assemblages.     

Eff icacy of angler catch data as a population and conservation monitoring tool for the f lagship Mahseer f ishes (Tor spp.) of Southern India

相似文献   

Assessing electric fishing sampling effort to estimate stream fish assemblage attributes

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.     

Typology of historical sources and the reconstruction of long‐term historical changes of riverine fish: a case study of the Austrian Danube and northern Russian rivers

Historical data are widely used in river ecology to define reference conditions or to investigate the evolution of aquatic systems. Most studies rely on printed documents from the 19th century, thus missing pre‐industrial states and human impacts. This article discusses historical sources that can be used to reconstruct the development of riverine fish communities from the Late Middle Ages until the mid‐20th century. Based on the studies of the Austrian Danube and northern Russian rivers, we propose a classification scheme of printed and archival sources and describe their fish ecological contents. Five types of sources were identified using the origin of sources as the first criterion: (i) early scientific surveys, (ii) fishery sources, (iii) fish trading sources, (iv) fish consumption sources and (v) cultural representations of fish. Except for early scientific surveys, all these sources were produced within economic and administrative contexts. They did not aim to report about historical fish communities, but do contain information about commercial fish and their exploitation. All historical data need further analysis for a fish ecological interpretation. Three case studies from the investigated Austrian and Russian rivers demonstrate the use of different source types and underline the necessity for a combination of different sources and a methodology combining different disciplinary approaches. Using a large variety of historical sources to reconstruct the development of past fish ecological conditions can support future river management by going beyond the usual approach of static historical reference conditions.     

Comparison of three standardised fish sampling methods in 14 alpine lakes in Austria

Abstract Standardised fishing methods using gillnets (EN 14575), electric fishing (EN 14011) and hydroacoustics (WI 00230244 CEN enquiry) to estimate species composition, abundance, biomass and size distribution were compared in 14 alpine lakes >50 ha. More fish species were detected using benthic gillnets (mean = 72.7%) than electric fishing (mean = 59.5%) and pelagic gillnets (mean = 29.6%). For all but two lakes, additional information from a local fisheries manager was required to obtain a complete list of species. Biomass data generated by standardised gillnetting and hydroacoustic surveys were not fully comparable, but a positive correlation was found. Gill netting and hydroacoustics both indicated a nearly fishless habitat below 75 m, which confirmed the maximum required fishing depth according to the European Standard EN 14757. Size distributions obtained from gillnet and hydroacoustic surveys differed statistically for large fish (>40 cm). Each standardised method reflected typical shortcomings. The European standard (EN 14757) should be amended for pelagic fish habitat in deep alpine lakes to include sampling effort corresponding to water volume, and additional gillnets with larger mesh sizes (e.g. 70 mm). Furthermore, the electric fishing standard (EN 14011) should be extended to incorporate requirements of lake fish sampling.     

太子河河流等级对鱼类群落结构及环境因子的影响

河流等级是一种用于评价河流生物多样性及环境特征的重要分类标准。以太子河流域为研究区域探究河流等级与鱼类群落分布之间的关系以及鱼类群落分布特征与环境因子之间的响应关系,并将太子河主要支流作为独立流域单元进行相同等级河流之间鱼类群落分布差异的比较。共设置125个点位,分3次调查鱼类群落和水环境理化特征,调查共采集到鱼类18 883尾,分属23科60种,洛氏鱥、宽鳍鱲、北方条鳅、棒花鱼为优势种,分别占鱼类总数的35.52%、8.58%、6.63%、5.53%。太子河流域鱼类群落结构在不同河流等级之间有显著差异,指示种分析表明洛氏鱥与北方条鳅是上游河段的指示种,短须颌须鮈与东北雅罗鱼是中游河段的指示种,?、大鳞副泥鳅及鰕虎鱼类是下游河段的指示种;摄食功能群在各级河流也有显著差异,杂食性鱼类的比例及物种数在三级河流和五级河流较高,昆虫食性的鱼类在一级河流和二级河流比例较高,昆虫食性鱼类的物种数在五级河流较高。河流等级对鱼类群落的物种丰富度和多样性水平有显著影响(F=3.644,P=0.008;F=2.543,P=0.043),最大值出现在三级河流。各等级河流之间总氮和氨氮有显著差异;相同等级河流...     

Variation in larval fish communities: implications for management and sampling designs in reservoir systems

Understanding spatial and temporal patterns in larval fish distributions is important for investigating factors related to recruitment variability and for developing sampling methodologies. Variation in species diversity (Shannon index) and density (number 100 m^?3) of larval fishes from nearshore and pelagic habitats in Glen Elder Reservoir, KS, USA, was assessed during 1999 and 2000. Species diversity and densities of individual taxa were significantly higher (P < 0.05) in nearshore habitats than pelagic habitats during both years. Larval fish densities were generally higher in the year 1999 with higher spring water levels. Gizzard shad Dorosoma cepedianum (Lesueur) was the most abundant taxon in nearshore and pelagic habitats during both years. In addition, larval gizzard shad was sampled for the longest duration in the upper water column and overlapped with all taxa collected. High densities of gizzard shad in both habitats suggested that the potential for competitive interactions was high, especially given the lack of aquatic vegetation and habitat heterogeneity in littoral habitats. Most of the variation in larval fish diversity and density was because of temporal variation. If sampling effort must be limited and the purpose of sampling is to monitor larval diversity or density, attention should focus on sampling the same location over long time periods rather than across a variety of sampling locations.     

基于鱼类体长频率分布和平均体长的采样站位数优化

鱼类体长数据较易获得,常用于数据有限的渔业资源评估和管理,且基于鱼类体长的指标可以作为渔业生态系统的生态监测指标。本文根据山东半岛南部海域底拖网季度调查收集的方氏云鳚体长数据,应用计算机模拟重采样方法,研究了调查站位数对估计方氏云鳚（Enedrias fangi）体长频率分布和平均体长的影响。结果表明,在各个季节,方氏云鳚体长频率分布离散指数（DI）变化范围为0~0.91,大部分站位的DI值为0.75~0.90,说明调查站位间体长频率分布较为相似,可以对调查站位数进行优化,提高采样效率;调查站位越多,体长频率分布和平均体长估计精确度越高;由于对不同体长数据指标估计的精度不同,用以估计体长频率分布和平均体长的样本量存在差异;20个和30个调查站位分别为估计方氏云鳚体长频率分布和平均体长的可接受样本量。本研究结果可为基于不同体长指标的渔业资源调查设计提供一定的理论支撑,有助于对基于体长指标有效站位数的初步了解,为山东半岛南部海域的鱼类资源科学调查和科学管理提供参考。     

Protected areas and frugivorous fish in tropical rivers: Small-scale fisheries,conservation and ecosystem services

1. Frugivorous fish provide often conflicting ecosystem services of seed dispersal and food provisioning in tropical rivers. Fishing may reduce the size and abundance of frugivorous fish, thus affecting their potential as seed dispersers, which could affect the conservation of these fish and of floodplain forests.
2. The goal of this study was to assess the influence of co-managed protected areas in the form of extractive reserves (RESEX) and small-scale fisheries on frugivorous fish in the Tapajós and Negro rivers, in the Brazilian Amazon. The study examined whether: (i) frugivorous fish are important for fisheries and selectively caught; and (ii) frugivorous fish abundance, size and fisheries catch per unit of effort are higher inside the RESEX than outside.
3. The analyses included fisheries-dependent data (3,753 fish landings) and independent data (12,730 sampled fish) collected in 16 fishing communities (eight for each river). In both rivers, frugivorous fish are among the 10 species caught the most and frugivorous biomass was proportionately higher in landings than in samplings, indicating fisheries selectivity towards these fishes.
4. In both rivers, catches of frugivorous fish were higher outside the RESEX than inside. Catch per unit effort and the proportion of frugivores in the catch were higher outside the RESEX in the Tapajós River but did not vary between sites inside and outside the RESEX in the Negro River. Frugivorous fish were larger inside the RESEX in the Negro, but smaller inside the RESEX in the Tapajós.
5. The results indicated that the ecosystem services of seed dispersal and food source provided by frugivorous fish are not in conflict in the tropical rivers studied. Therefore, these clearwater and blackwater rivers in the Brazilian Amazon show a balance between fisheries and conservation of frugivorous fish, which play an essential role in the functioning of tropical floodplain forest ecosystems.

     

Challenges in developing fish-based ecological assessment methods for large floodplain rivers

Abstract  Large European floodplain rivers have a great diversity in habitats and fish fauna, but tend to be heavily modified. The complexity of these river systems and their multiple human impacts pose considerable challenges for assessment of their ecological status. This paper discusses: (1) the application of historical information on fish fauna and habitat availability to describe reference conditions; (2) responses of fish assemblages to human disturbance by comparing various rivers and river segments with different impacts and/or time series within rivers; (3) the role of floodplain water bodies in ecological assessment; and (4) monitoring of large rivers using different gears and sampling designs for main channels and floodplain habitats. The challenge for the future is to standardise and calibrate sampling methods and data to enhance the potential for ecological assessment of large rivers.     

Offshore currents explain the discontinuity of a fish community in the seagrass bed along the Japanese archipelago

Oceanographic conditions can affect spatial variability in fish community structures by influencing the temperature‐dependent latitudinal distribution of adult fishes and transport during their young stages. In order to examine latitudinal variability in the fish community structure within a single coastal ecosystem, quantitative sampling was conducted in the sub‐tidal zone of seagrass Zostera marina beds over a broad latitudinal scale (31.31–43.0°N: from subtropical to sub‐boreal zones, covering 80% of the latitudinal range of seagrass distribution in Japan) in the western North Pacific based on a uniform methodology. Cluster analysis with the similarity of fish communities showed that 13 sampling sites were divided into two clusters. The border between the two clusters corresponded with the area of mixing of two dominant currents, Oyashio and Kuroshio, which form a border between the warm temperate zone and the cool temperate zone off the Pacific coast of Japan. Oceanographic properties, such as major currents off the coast, are suggested to affect the latitudinal variability in the fish communities in the coastal ecosystem in the western North Pacific.     

Organic matter derived from kelp supports a large proportion of biomass in temperate rocky reef fish communities: Implications for ecosystem‐based management

相似文献   

The effects of ecoregions and local environmental characteristics on spatial patterns in boreal riverine fish assemblages

The conservation, management and monitoring of aquatic resources should benefit from understanding their spatial structuring. In this paper, we used the reference condition approach (RCA) to test if the variability in biotic communities, riverine fish assemblages in the present case, is better controlled with a spatial delineation based on ecoregions or by grouping rivers with local catchment characteristics. Electrofishing data from 493 riffles in 99 rivers in Finland were used in the analysis. We completed multivariate analyses (nonmetric multidimensional scaling, multiresponse permutation procedures) to identify differences in fish community composition among groups based on ecoregions or catchment characteristics. We concluded that both regional processes and local environmental characteristics structured fish populations, and bioassessment of freshwaters should be based on regional spatial delineations, supported by local scale characteristics. Spatial delineations like ecoregions should be used to assist the bioassessment to improve the efficiency to detect the human impacts.     

Flow requirements of non‐salmonids

Research into the relationships between non‐salmonid fish population dynamics and discharge is in its infancy compared with salmonids, thus compromising the ability to manage flows in rivers and maintain ecological status. This study reviews the potential role of ‘natural’ hydrographical variability on fish life‐history characteristics and develops a fish typology based on flow preference and conservation importance criteria that can be used to underpin the needs of hydrological management to support these fish community types. It highlights important characteristics of the natural flow regime that need to be maintained to ensure sustainability of populations of these species and offers a mechanism to categorise the fish community types, thus allowing generic management scenarios to be developed rather than complex single‐species scenarios that are impractical.