Effects of a rock‐ramp fishway on summer fish assemblage in a Lake Huron tributary

The use of nature‐like fishways to increase ecosystem connectivity has increased in recent years, but their effectiveness has rarely been evaluated. A rock ramp was constructed in the Shiawassee River in 2009, and post‐construction effects (2011–2012) were evaluated on the summer fish assemblage by comparing fish assemblage composition to a nearby free‐flowing river and a nearby river with a dam. Patterns of fish species richness, mean catch‐per‐unit‐effort and proportional abundance in reaches upstream and downstream of the rock ramp, dam and comparable sites in the free‐flowing river were evaluated. Overall, species richness by site and proportional abundance in the rock‐ramp river were more similar to the free‐flowing river, while species richness by reach was more similar to the dammed river. These findings suggest that the rock ramp has improved connectivity for the summer fish assemblage, but has not fully restored conditions to the level observed in a free‐flowing river.     

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.     

Effects of within-patch habitat structure and variation on fish assemblage characteristics in the Bernecei stream, Hungary

Abstract –  Over a 3-year period we examined variability in physical habitat structure and species richness, abundance and assemblage composition of fishes in 13 habitat patches in the Bernecei stream, Hungary. Principal component analysis of habitat structure data from patches elucidated a riffle-run-pool habitat gradient across patches. Temporal habitat variability increased significantly from riffle to pool patches. Fish assemblage characteristics displayed relatively continuous change over the habitat gradient and were relatively stable within patches. Assemblage structure properties (e.g., species richness) displayed different responses to the habitat gradient and to within-patch habitat variability. In general, pool patches had more diverse assemblages and greater within-patch assemblage variability than riffle patches. However, within-patch dynamics were largely determined by the population dynamics of a habitat generalist (i.e., minnow). Broad scale environmental variability (i.e., a catastrophic 100-year flood) also appeared to affect within-patch fish assemblage characteristics. Our results demonstrate that fish assemblage structure is influenced by physical variability (i.e., both floods and spatio-temporal habitat variability) within the Bernecei stream.     

In‐stream structure alters density‐dependent fish effects in stream ecosystems

The independent effects of in‐stream structure (ISS) and fish foraging on stream properties have been well documented, but few studies have explored the interactive effects of ISS and fishes on streams. Herein, we tested the independent and interactive effects of ISS and a generalist fish (Blacktail shiner, Cyprinella venusta) on suspended organic matter (SOM), benthic algae, invertebrate density and fish growth using experimental mesocosms. We found that Blacktail shiner foraging affected all of the ecosystem properties; however, in some cases, the fish effects differed between mesocosms with and without ISS. Specifically, mesocosms with ISS provided greater surface area for invertebrate colonisation and enhanced food resources for Blacktail shiner. As a result, benthic foraging by Blacktail shiner was reduced in these mesocosms. The reduced benthic foraging in turn enhanced benthic algae and benthic invertebrates via a bottom‐up, nutrient excretion pathway. The ISS‐dependent effects of fish on these stream properties, however, were only evident at low and intermediate fish densities (1 and 2 fish·m^?2 respectively). This was likely because at the highest fish density (4 fish·m^?2) intense fish foraging overrode any mediating effects of ISS. Furthermore, fish growth decreased with fish density because of intraspecific competition, but this negative effect on growth was reduced in mesocosms with ISS because of the increased forage base. However, the positive effect on fish growth was weak and only marginally significant. Our data suggest that fish‐mediated effects on streams are context dependent, changing with microhabitat availability (e.g. ISS) and density of the fish population.     

Quantifying fish species richness and abundance in Amazonian streams: assessment of a multiple gear method suitable for Terra firme stream fish assemblages

A multigear sampling method to quantify fish richness and abundance in Amazonian Terra firme streams was assessed. This method is based on the four‐pass removal method using the combined application of different nets. The efficiency of the method was explored over 10 replicated sites along three streams over day, night and seasons. Use of four successive passes allowed both abundant and rare species to be collected and the abundance of common species to be estimated. On average, a high proportion (41%) of rare species was collected per sample (only one or two individuals) after four fishing passes. The efficiency of the sampling method to detect species richness per sample between successive passes was estimated using an autosimilarity approach. Although species richness and abundance increased with successive passes, no major differences were obtained between the third and fourth pass. A single pass considerably underestimated the richness and abundance of species in these type of streams, and night sampling also increased beta‐diversity by at least 20%. Abundance estimates demonstrated high efficiency with an overall sampling error of only 8 and 11% for samples and single species, respectively. Capture efficiency differed among fish species exhibiting different ecological traits and showed significant differences among seasons for total samples. Results supported the robustness of the method and its suitability to quantify fish richness and abundance in small, wadeable Amazonian Terra firme streams inhabited by highly diverse fish assemblages.     

Fish species richness in lakes of the northeastern lowlands in Germany

Fish species richness was assessed by electrofishing and gillnetting in 16 lakes of the northeastern lowland in Germany (the Schorfheide biosphere reserve). The lakes range from 0.03 to 10.55 km² and support between 5 and 14 fish species. Species richness is significantly correlated with lake area in an exponential and a power model. Richness is also correlated with shoreline development and total dissolved solids. This supports the hypothesis that larger areas contain more species within a taxonomic group due to increased habitat diversity. The slope of the species-area curve is low compared with most other studies of fish species richness in lakes, and the intercept value is high. This is interpreted as the result of high habitat and food diversity, lack of stress from abiotic factors, and the small regional species pool from which these lakes can be colonized. Two species inventories, one from the beginning of this century and one from the 1950s, are available for comparison. Average species richness did not change during the last decades. Species turnover rates were not related to the degree of anthropogenic eutrophication or to the intensity of fishery exploitation in these lakes. On the species level, however, one effect of accelerated eutrophication is apparent, the disappearance of 4 bottom-living species from one to 6 of the study lakes.     

Seasonal dynamics of fish assemblage in a pond canal

The annual dynamics of fish assemblage in a pond-connecting canal of a South Moravian pond aquaculture facility was studied to reveal potential assemblage effects on pond stocks and vice versa. The species richness of fish assemblage and seasonal dynamics of its development were predominantly dependent upon the fish stock of the interconnected ponds (particularly due to escapees during the period of pond harvesting), which contributed to a considerable increase of commercial fish species occurrence. Using a seasonal parameter, the season proved to have a major impact on fish assemblage dynamics (r = −0.71, P < 0.001). Spring samples were dominated by commercial fishes of aquaculture origin (mainly Cyprinus carpio). Occurrence of several fish species originating from the wild (bleak, Alburnus alburnus, chub, Leuciscus cephalus and roach, Rutilus rutilus) was also reported. The pond canal was found to be an important reservoir site of persistent survival and potential subsequent spreading of some undesirable alien fishes such as topmouth gudgeon (Pseudorasbora parva) and gibel carp (Carrasius auratus). Moreover, more attention should be paid to the potential negative impacts of all fishes of aquaculture origin upon the natural ecosystem and to the adverse effects due to the immigration of wild fish into aquaculture pond farming units.     

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。     

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.     

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.     

Effects of mangrove deforestation on fish assemblage at Pak Phanang Bay,southern Thailand

Daytime sampling using a seine net was conducted at Pak Phanang Bay (Nakhon Si Thammarat Province, Thailand) in February and July 2006, to determine differences in fish assemblage structures between a mangrove site and an adjacent site completely cleared of mangroves. The overall numbers of fish species and individuals were significantly higher at the mangrove site than the cleared site in both months. Although benthic crustacean feeders showed more species and individual numbers at the mangrove site in both months, the opposite was found for zooplankton feeders. A cluster analysis, based on the abundance of each species, demonstrated that the fish assemblage structures were distinctly different between the two sites. In addition, significant differences in length frequency distributions for each of the four most abundant species were found between the sites in February and/or July. Small individuals of Scatophagus argus, Ambassis nalua, and Tetraodon nigroviridis were more common at the mangrove site, and of Chelon subviridis at the cleared site. These results suggest that mangrove deforestation exerts marked effects on fish assemblages.     

Modelling stream fish species distribution in a river network: the relative effects of temperature versus physical factors

Abstract – The relative influence of temperature versus local physical factors on the spatial distribution of riverine fish species was investigated in a large watershed of south-western France. Using generalised additive models and hierarchical partitioning, we modelled the ecological responses of 28 fish species to a set of five environmental predictors, and we quantified the independent effect of each predictor. The spatial distribution of fish species was primarily determined by both mean temperature and position along the upstream–downstream gradient. However, responses to these environmental factors varied according to the species considered. Fish species with strong thermal requirements (e.g., common carp, black bullhead, Atlantic salmon) were mainly sensitive to temperature whereas longitudinal gradient was of primary importance for downstream species (e.g., common bream, largemouth bass, pike perch). Both the statistical methods used gave concordant results and appeared complementary. This dual-approach, quantifying the relative contribution of each environmental factor, appears particularly useful to understand the spatial distribution of stream fish species. Separating the effects of temperature versus habitat factors is crucial to accurately predict species distribution modifications in the current context of global change.     

广西桂林青狮潭水库鱼类物种组成及多样性分析

2015年4月至2016年1月按季度对青狮潭水库库区鱼类资源进行了调查,采集鱼类样本3 750尾(153.28kg),经鉴定有鱼类32种,隶属于5目12科27属,其中以鲤形目鱼类为主,分别占总物种数和总个体数的53.13%和61.92%。相对重要性指数分析表明,鲫(Carassius auratus)、■(Hemiculter leucisculus)和鲤(Cyprinus carpio)为优势种;鱼类多样性分析结果显示,各季节丰富度指数(D)为2.58~3.52,Shannon-Wiener多样度指数(H')为1.62~1.92,Pielou种类均匀度指数(J')为0.53~0.63,其中夏季多样性最高、冬季相对较低;空间上,鱼类多样性呈现从河流入库口、近岛水区向湖心降低趋势。聚类及相似性分析(ANOSIM)表明,鱼类群落组成时空差异不明显。     

The effect of lakes on the stream fish fauna

The effect of natural lakes on the fish species distribution in surrounding streams was studied using electrofishing survey data from 3281 localities in streams throughout Sweden. The occurrence of lake fish (northern pike, European perch, roach and burbot) was significantly higher close to lakes, both up- and downstream, as compared to localities further up- or downstream of lakes. Correspondingly, the occurrences of stream fish (brown trout, grayling, European minnow and bullheads) were lower close to lakes. It is suggested that the lower occurrences of the latter close to lakes be due to biotic interaction with lake fish, especially predation from pike and burbot. The results strongly indicate that the effect of lakes on water temperature, drift of plankton and invertebrates or the moderating effect on water fluctuations and quality did not influence the stream fish fauna to the same extent as the presence of lake fish in a zone up- as downstream of the lakes. Lakes function as a reservoir of strong predators and competitors.     

枸杞岛筏式贻贝养殖海域鱼类群聚特征

为探究筏式贻贝养殖生境鱼类资源养护功能,于2020年9－12月对枸杞岛筏式贻贝养殖生境(分表层区和底层区)及周边岩礁生境的鱼类进行了多网目组合刺网采样。应用相对重要性指数IRI、多样性指数并结合等级聚类、非度量多维标度排序(nMDS)分析鱼类组成和群落结构。结果显示,在2种生境中共采集鱼类55 种,隶属于10目34科47属,其中贻贝养殖生境采集到37种(底层和表层分别为29和20种);岩礁生境共采集到40种。在鱼类组成上,中国花鲈和鲻是贻贝养殖生境表层区的典型优势种,而黄姑鱼和褐菖鲉是贻贝养殖生境底层区的典型优势种;褐菖鲉同时也是岩礁生境的典型优势种。多样性分析表明,贻贝养殖生境的总体鱼类多样性要高于岩礁生境,但尚不显著。多元分析显示,各月份2种生境中的鱼类群落格局均可分为3种类型,虽与养殖表层区、养殖底层区和岩礁区并非严格一致,但各群落间差异依然显著。研究表明,大规模筏式养殖设施的存在吸引了众多中上层鱼类及底层鱼类,也为岩礁生境优势鱼类提供了额外的栖息环境,发挥了近似于浮鱼礁系统的资源养护作用。研究结果可为岛礁海域海洋牧场目标种的选择和人工生境构建模式的应用提供重要参考。     

Effects of small dam condition and drainage on stream fish community structure

Low‐head dams are ubiquitous in eastern North America, and small dam removal projects seek to improve habitat conditions for resident and migratory fishes. Effects of small dams of varying status on local fish communities are poorly documented, and recent work suggests benefits of maintaining fragmentation. We sampled fish at 25 dams (9 breached, 7 relict, 9 intact) in three river basins in North Carolina, USA. Fishes were sampled at three reaches/dam from 2010 to 2011. Study reaches were located upstream (free‐flowing reaches), downstream (tailrace) and >500 m downstream of dams (n = 75 reaches). Analyses revealed significantly elevated fish CPUE, taxa richness and percentage intolerant taxa in intact dam tailraces suggesting small dams may improve conditions for resident taxa. Breached dam tailrace reaches exhibited lower fish CPUE, taxa richness and percentage intolerant taxa relative to upstream reference reaches. Relict dams exhibited no between‐reach differences in fish community metrics. Nonmetric multidimensional scaling revealed drainage‐specific stream fish responses across study drainages. Tar and Roanoke drainage streams with intact and relict dams supported fish assemblages indicative of natural communities, whereas Neuse Drainage streams with intact and breached dams contained disturbed habitats and communities. These data demonstrate fish community responses to dam condition are drainage specific but communities in streams with intact and relict dams are largely similar. Additionally, breached dams may warrant higher removal priorities than intact dams because they negatively influence fish communities. The variability in response to some dams indicates managers, regardless of region or country, should consider holistic approaches to dam removals on a case‐by‐case basis.     

Evaluating habitat associations of a fish assemblage at multiple spatial scales in a minimally disturbed stream using low‐cost remote sensing

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Effects of small hydropower plants on fish assemblages in medium‐sized streams in central and northern Portugal

• 1. Over the last decade the development of small hydropower projects has been one of the most active areas of the energy sector. One of the main environmental challenges faced by such projects is related to fish passage.
• 2. The impact of 18 small hydropower plants (SHPs) with distinct levels of fish‐pass effectiveness was investigated in the summers of 1998 and 1999 by comparing fish assemblage composition and structure at 36 sites, above and below SHPs.
• 3. With regard to effectiveness, it was estimated that eight (44.4%) of the surveyed passage facilities were suitable for target species, whereas the remaining 10 (55.6%) were considered unsuitable. In neither case did the composition of fish assemblages upstream and downstream from SHPs differ significantly, while assemblage similarity was relatively high.
• 4. Multivariate techniques identified cover, depth and coarse substrate as the main parameters structuring fish assemblages. It is suggested that these variables have created a rich, patchy, heterogeneous habitat, thereby providing satisfactory resources and favourable conditions required by fish and contributing to the maintenance of assemblages.
• 5. Although populations of some species that occurred both upstream and downstream from SHPs have developed differences in their size structures, SHP‐induced fragmentation of fish populations may not necessarily result in genetic divergence among semi‐isolated populations.

Copyright © 2006 John Wiley & Sons, Ltd.     

Effects of littoral habitat complexity and sunfish composition on fish production

Carey MP, Maloney KO, Chipps SR, Wahl DH. Effects of littoral habitat complexity and sunfish composition on fish production. Ecology of Freshwater Fish 2010: 19: 466–476. © 2010 John Wiley & Sons A/S Abstract – Habitat complexity is a key driver of food web dynamics because physical structure dictates resource availability to a community. Changes in fish diversity can also alter trophic interactions and energy pathways in food webs. Few studies have examined the direct, indirect, and interactive effects of biodiversity and habitat complexity on fish production. We explored the effects of habitat complexity (simulated vegetation), sunfish diversity (intra‐ vs. inter‐specific sunfish), and their interaction using a mesocosm experiment. Total fish production was examined across two levels of habitat complexity (low: 161 strands m^?2 and high: 714 strands m^?2) and two sunfish diversity treatments: bluegill only (Lepomis macrochirus) and bluegill, redear sunfish (Lepomis microlophus), and green sunfish (Lepomis cyanellus) combination. We also measured changes in total phosphorus, phytoplankton, periphyton, and invertebrates to explain patterns in fish production. Bluegill and total fish production were unaffected by the sunfish treatments. Habitat complexity had a large influence on food web structure by shifting primary productivity from pelagic to a more littoral pathway in the high habitat treatments. Periphyton was higher with dense vegetation, leading to reductions in total phosphorus, phytoplankton, cladoceran abundance and fish biomass. In tanks with low vegetation, bluegill exhibited increased growth. Habitat complexity can alter energy flow through food webs ultimately influencing higher trophic levels. The lack of an effect of sunfish diversity on fish production does not imply that conserving biodiversity is unimportant; rather, we suggest that understanding the context in which biodiversity is important to food web dynamics is critical to conservation planning.     

黄海南部近岸海域鱼类群落结构与区系划分

黄海南部海域具有复杂的水团结构和海流环境,使该海域鱼类群落产生较为复杂的空间结构。为研究黄海南部近岸海域鱼类群落结构特征,实验根据2014—2015年对该海域进行4个季度的底拖网调查数据,利用多元统计方法分析了该海域鱼类群落的分布格局并比较了各群落的相对生物量、生物多样性、优势种等结构特征。应用聚类分析(cluster)和多维标度排序(MDS)分析将黄海南部近岸海域划分为海州湾群落与江苏近岸群落;海州湾群落的平均相对资源量和生物多样性均高于江苏近岸群落,而暖温性与暖水性鱼类所占比重相对较低;海州湾群落的优势种主要为方氏云鳚、大泷六线鱼和日本鳀等,季节变化显著;江苏近岸群落的优势种为短吻红舌鳎、途、棘头梅童鱼和黑鳃梅童鱼等,季节变化不明显。研究表明,黄海南部近岸海域可划分为海州湾区系与江苏近岸区系,其鱼类群落结构特征具有显著差异。海流、水团、底质类型及水深等环境因子是形成鱼类群落结构差异的主要因素。