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Predicting fish assemblages and diversity in shallow lakes in the Yangtze River basin
No full textHabitat modifications induced by humans severely impact biotic components of freshwater ecosystems. In China, shallow lakes in the Yangtze River basin are facing severe habitat degradation induced by pollution, habitat losing, macrophytes disappearing and fishery activities. Effectively modeling the fish communities on the basis of biotic and abiotic environmental descriptors would be helpful to understand the relationships between fish and their environment, and to develop suitable conservation strategies to sustain the biodiversity in these ecosystems. From 2007 to 2009, investigations were carried out on fish and their environment in 6 lakes distributed in the mid-reach of the Yangtze River basin. According to the CPUE values of each fish species from each sampling, 117 datasets were ordinated using self-organizing map (SOM). Fish communities were classified into three clusters of species assemblages, spatial and temporal distributions were showing in it. Seasonal changes in fish community were more obvious in vegetated habitats than in unvegetated areas. The total CPUE, fish diversity and species richness were significantly different among the assemblages (p < 0.01). Based on the indicative value of each species in each cluster calculated by Indval method, 16 species were identified as indicators: 13 indicators in cluster G1 are pelagic or benthopelagic fish, the only one indicator species in G2 is a tolerant species (Culter dabry B.), while the other two indicator species in G3 are demersal fish (Rhinogobius giurinus R. and Odontobutis obscurus T. & G.). These results are in agreement with the contributions of different ecological groups of fish in each assemblage in the trained SOM, pelagic and benthopelagic fish were found having more activities in spring and winter, while more activities of demersal fish were found in summer and autumn. Fish community assemblages, the total fish CPUE, diversity and species richness in those lakes were then predicted by 15 abiotic and biotic factors using random forest (RF) and classification and regression tree (CART) predictive models. The predicted assignment of each site unit to the correct assemblage had an average success of 74.4% and 60.7% in RF and CART models, respectively. The dominant variables for discriminating three fish assemblages were water depth, distance to the bank and total phosphorus. While the two important variables in prediction fish CPUE, diversity and species richness were lake surface area and water depth, density of rotifer and water depth, water depth and water temperature, respectively. The overall percentages of successful prediction varied from 56.5% to 67% utilizing leave-one-out for cross-validation tests. (C) 2011 Elsevier GmbH. All rights reserved.Habitat modifications induced by humans severely impact biotic components of freshwater ecosystems. In China, shallow lakes in the Yangtze River basin are facing severe habitat degradation induced by pollution, habitat losing, macrophytes disappearing and fishery activities. Effectively modeling the fish communities on the basis of biotic and abiotic environmental descriptors would be helpful to understand the relationships between fish and their environment, and to develop suitable conservation strategies to sustain the biodiversity in these ecosystems. From 2007 to 2009, investigations were carried out on fish and their environment in 6 lakes distributed in the mid-reach of the Yangtze River basin. According to the CPUE values of each fish species from each sampling, 117 datasets were ordinated using self-organizing map (SOM). Fish communities were classified into three clusters of species assemblages, spatial and temporal distributions were showing in it. Seasonal changes in fish community were more obvious in vegetated habitats than in unvegetated areas. The total CPUE, fish diversity and species richness were significantly different among the assemblages (p < 0.01). Based on the indicative value of each species in each cluster calculated by Indval method, 16 species were identified as indicators: 13 indicators in cluster G1 are pelagic or benthopelagic fish, the only one indicator species in G2 is a tolerant species (Culter dabry B.), while the other two indicator species in G3 are demersal fish (Rhinogobius giurinus R. and Odontobutis obscurus T. & G.). These results are in agreement with the contributions of different ecological groups of fish in each assemblage in the trained SOM, pelagic and benthopelagic fish were found having more activities in spring and winter, while more activities of demersal fish were found in summer and autumn. Fish community assemblages, the total fish CPUE, diversity and species richness in those lakes were then predicted by 15 abiotic and biotic factors using random forest (RF) and classification and regression tree (CART) predictive models. The predicted assignment of each site unit to the correct assemblage had an average success of 74.4% and 60.7% in RF and CART models, respectively. The dominant variables for discriminating three fish assemblages were water depth, distance to the bank and total phosphorus. While the two important variables in prediction fish CPUE, diversity and species richness were lake surface area and water depth, density of rotifer and water depth, water depth and water temperature, respectively. The overall percentages of successful prediction varied from 56.5% to 67% utilizing leave-one-out for cross-validation tests. (C) 2011 Elsevier GmbH. All rights reserved
Predicting assemblages and species richness of endemic fish in the upper Yangtze River
No full textThe present work describes the ability of two modeling methods, Classification and Regression Tree (CART) and Random Forest (RF), to predict endemic fish assemblages and species richness in the upper Yangtze River, and then to identify the determinant environmental factors contributing to the models. The models included 24 predictor variables and 2 response variables (fish assemblage and species richness) for a total of 46 site units. The predictive quality of the modeling approaches was judged with a leave-one-out validation procedure. There was an average success of 60.9% and 71.7% to assign each site unit to the correct assemblage of fish, and 73% and 84% to explain the variance in species richness, by using CART and RF models, respectively. RF proved to be better than CART in terms of accuracy and efficiency in ecological applications. In any case, the mixed models including both land cover and river characteristic variables were more powerful than either individual one in explaining the endemic fish distribution pattern in the upper Yangtze River. For instance, altitude, slope, length, discharge, runoff, farmland and alpine and sub-alpine meadow played important roles in driving the observed endemic fish assemblage structure, while farmland, slope grassland, discharge, runoff, altitude and drainage area in explaining the observed patterns of endemic species richness. Therefore, the various effects of human activity on natural aquatic ecosystems, in particular, the flow modification of the river and the land use changes may have a considerable effect on the endemic fish distribution patterns on a regional scale. (C) 2010 Elsevier B.V. All rights reserved
Variations of fish composition and diversity related to environmental variables in shallow lakes in the Yangtze River basin
No full textVariations in fish communities of shallow lakes in the Yangtze basins were investigated from September 2007 to September 2009. Six lakes were chosen for comparative study of species composition and diversity in relation to environmental variations. Lake heterogeneity was described with environmental physico-chemical variables, using principal component analysis. Sixteen families, composed of 75 species of fish were found in the studied lakes, Cyprinidae being the dominant group. Fish species were divided by habitat preference and trophic guild: benthopelagic and herbivorous fish were the most common guilds in all lakes. Species diversity and richness were significantly higher in spring, while the evenness, expressed by equitability of Simpson's index, was not significantly different among seasons. Species richness and diversity were significantly higher in vegetated lakes (e. g. Liangzihu Lake) than in non-vegetated lakes (e. g. Biandantang Lake), with the largest area (Liangzihu Lake) harbouring the largest species richness and the greatest diversity. The relationship between environmental variables and fish assemblage were analysed using canonical correspondence analysis (CCA). The dominant gradients describing species composition and abundance among the sampling sites were: total phosphorus, total nitrogen, chlorophyll a, transparency and water depth. Our study led to the following conclusions: 1) the water quality was better - i.e. high transparency, low total phosphorus (TP) and total nitrogen (TN) and chlorophyll a- in vegetated lakes than in unvegetated lakes; 2) vegetated lakes had higher fish diversity than unvegetated lakes; 3) fish relative abundance (CPUE: number of fish per fishing pass) was significantly related to water chemical parameters. Consequently, the details of the findings are useful and relevant for developing suitable conservation strategies to sustain the integrity of fish communities in these lakes
Fine scale changes in biodiversity in a soil-water ecotone: Collembola in two peat-bogs of Kabylia (Algeria)
No full textCollembolan communities in a peat bog versus surrounding forest analysed by self-organizing map.
No full textCommunity structure of small fishes in a shallow macrophytic lake (Niushan Lake) along the middle reach of the Yangtze River, China
No full textThis study describes the current status of the small fish community in Niushan Lake in China, and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on macrophyte cover conditions, the lake was divided into three major habitat types: (1) Potamogeton maackianus habitat, (2) Potamogeton maackianus and Myriophyllum spicatum habitat, and (3) uncovered or less-covered habitat. Fish were sampled quantitatively in the three habitat types by block nets seasonally from September 2002 to August 2003. A total of 10 469 individuals from 27 fish species were caught, among which 20 species were considered as small fishes. Rhodeus ocellatus, Paracheilognathus imberbis, Pseudorasbora parva, Micropercops swinhonis and Cultrichthys erythropterus were recognized as dominant small fishes according to their abundance and occurrence. It was noted that (1) small fishes predominated the total number of fish species in the lake, which reflected to some degree the size diminution phenomenon of fish resources; (2) many small fishes had plant detritus as their food item, which was consistent with the abundance of macrophyte detritus in the lake and implied the importance of detritus in supporting small fish secondary production. Canonical correspondence analysis suggested that the spatial distributions of most small fishes were associated with complex macrophyte cover conditions. Macrophyte biomass was positively correlated with species richness, diversity index and the catch per unit of effort (CPUE) of the fish community. Water depth had no significant effects on species diversity and distribution of the small fishes. Correspondence analysis revealed a higher occurrence of the small fishes and higher abundance of individuals in summer and autumn. Seasonal length-frequency distributions of several species indicated that more larval and juvenile individuals appeared in spring and summer. This study provides some baseline information which will be essential to long-term monitoring of small fish communities in the Yangtze lakes.This study describes the current status of the small fish community in Niushan Lake in China, and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on macrophyte cover conditions, the lake was divided into three major habitat types: (1) Potamogeton maackianus habitat, (2) Potamogeton maackianus and Myriophyllum spicatum habitat, and (3) uncovered or less-covered habitat. Fish were sampled quantitatively in the three habitat types by block nets seasonally from September 2002 to August 2003. A total of 10 469 individuals from 27 fish species were caught, among which 20 species were considered as small fishes. Rhodeus ocellatus, Paracheilognathus imberbis, Pseudorasbora parva, Micropercops swinhonis and Cultrichthys erythropterus were recognized as dominant small fishes according to their abundance and occurrence. It was noted that (1) small fishes predominated the total number of fish species in the lake, which reflected to some degree the size diminution phenomenon of fish resources; (2) many small fishes had plant detritus as their food item, which was consistent with the abundance of macrophyte detritus in the lake and implied the importance of detritus in supporting small fish secondary production. Canonical correspondence analysis suggested that the spatial distributions of most small fishes were associated with complex macrophyte cover conditions. Macrophyte biomass was positively correlated with species richness, diversity index and the catch per unit of effort (CPUE) of the fish community. Water depth had no significant effects on species diversity and distribution of the small fishes. Correspondence analysis revealed a higher occurrence of the small fishes and higher abundance of individuals in summer and autumn. Seasonal length-frequency distributions of several species indicated that more larval and juvenile individuals appeared in spring and summer. This study provides some baseline information which will be essential to long-term monitoring of small fish communities in the Yangtze lakes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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