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Journal ArticleDOI

Native and exotic fish species in the tiber river watershed (umbria - italy) and their relationship to the longitudinal gradient

TL;DR: The preliminary results suggest that characteristics of fish community alterations depend on the type of river sector involved; the small rivers of the basin are a refuge zone for the native community and are currently of fundamental importance for maintaining biodiversity.
Abstract: In this study we examine the spatial variations in the fish communities in the Tiber River watershed, including both native and exotic species. Its main objectives were to assess the quality of fish communities of this area and to verify if factors of fish community disturbance are constant over the basin or if they change along the river gradient. The level of degradation was evaluated according to the ratio between the number of native fish species and total number of species (ZIC = Zoogeographic Integrity Coefficient). A total of 37 fish species was found, 13 native and 24 exotic (64.86%). Cyprinid is the prevailing family with 15 species (7 native, 8 exotic). The species most frequently introduced are cyprinids, followed by salmonids (4 species) and gobids (3 species). Of the 24 exotic species only 11 (45.83%) can be considered intentionally introduced by man: the proportion of intentionally introduced transplanted species (66.67%) is considerably higher than the translocated species (33.33%). There is a correlation between the longitudinal gradient of the river, the morphological evolution of the riverbed and decline in water quality. High ZIC values were related to higher elevation, greater slope and better water quality. As the size of the river increases the fish communities appear to be ever-more dominated by species of exotic origin, whose number progressively increases with the worsening of the water quality and downstream movement. The number of native species is the greatest in the middle reaches of the rivers, and decreases both upstream and downstream. Compared to the introduced species, the native species tend to stay upstream and are often the only species found in the headwaters. The number of introduced species increases downstream. We have also found differences among translocated and transplanted species: the first ones tend to favor the middle reaches of the rivers, while transplanted species seem to prefer the downstream sectors. In almost all cases, the sampling station immediately below an impoundment has the lowest ZIC values in comparison to the river stretches above the dam. Our preliminary results suggest that characteristics of fish community alterations depend on the type of river sector involved; the small rivers of the basin are a refuge zone for the native community and are currently of fundamental importance for maintaining biodiversity.

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Journal ArticleDOI
TL;DR: Analysis of Lee’s phenomenon revealed the existence of differential mortality among younger individuals (1 and 2 years old) that favours larger individuals, and the sex ratio appears to be balanced, although females predominate in the younger cohorts, while the percentage of males increases among older specimens.
Abstract: The age and growth of the invasive black bullhead Ameiurus melas (Rafinesque, 1820) were studied in the Corbara Reservoir, an artificial lake located on the River Tiber in central Italy. The results of the research revealed that the population was made up of eight cohorts, the oldest specimens being spawned in 1999. The sex ratio appears to be balanced, although females predominate in the younger cohorts, while the percentage of males increases among older specimens. The differences between sexes in the slope of the length-weight relationship were not statistically significant; the slope for the whole sample (b = 3.055) was significantly greater than 3, indicating an allometric growth pattern of the black bullhead. There were no significant differences in mean back-calculated lengths at age between the sexes. Analysis of Lee’s phenomenon revealed the existence of differential mortality among younger individuals (1 and 2 years old) that favours larger individuals. The Von Bertalanffy growth function was TLt = 35.69 {1 – exp[–0.18 (t + 0.27)]}. The specimens caught displayed mean relative weight (Wr ) values distinctly below 100 at all ages, while no significant difference emerged between the sexes with regard to condition.

12 citations


Cites background from "Native and exotic fish species in t..."

  • ...melas is widespread in the River Tiber, one of its most abundant populations is to be found in Corbara Reservoir (Lorenzoni et al., 2006)....

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  • ...While A. melas is widespread in the River Tiber, one of its most abundant populations is to be found in Corbara Reservoir (Lorenzoni et al., 2006)....

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Journal ArticleDOI
TL;DR: Ozcan GAYGUSUZ*, Ozgur EMIROĞLU, Ali Serhan TARKAN, Hamdi AYDIN, Nildeniz TOP, Zeynep DORAK, Ugur KARAKUŞ, Sercan BAŞKURT.
Abstract: Ozcan GAYGUSUZ*, Ozgur EMIROĞLU, Ali Serhan TARKAN, Hamdi AYDIN, Nildeniz TOP, Zeynep DORAK, Ugur KARAKUS, Sercan BASKURT 1 Faculty of Fisheries, Istanbul University, Laleli, Istanbul, Turkey 2 Department of Biology, Science and Art Faculty, Eskisehir Osmangazi University, Eskisehir, Turkey 3 Faculty of Fisheries, Mugla Sitki Kocman University, 48000 Kotekli, Mugla, Turkey 4 Gazanfer Bilge Vocational School, Kocaeli University, 41500 Karamursel, Kocaeli, Turkey

11 citations


Cites background from "Native and exotic fish species in t..."

  • ...Nonnative freshwater fish introductions have been demonstrated to cause decline in native freshwater fish species (Byers et al., 2002; Tarkan et al., 2012b) and in some cases even extinction (Lorenzoni et al., 2006)....

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  • ..., 2012b) and in some cases even extinction (Lorenzoni et al., 2006)....

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Journal ArticleDOI
TL;DR: To preserve the native genetic diversity, stocking of non-native fingerlings should cease immediately and native Pearl River bighead and silver carp fish farms should be established, as this research demonstrates the danger to native biodiversity across China.
Abstract: Bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix have been two economically important aquaculture species in China for centuries. In the past decades, bighead and silver carp have been introduced from the Yangtze River to many river systems in China, including the Pearl River, in annual, large-scale, stocking activities to enhance wild fisheries. Nonetheless, few studies have assessed the ecological or genetic impacts of such introductions on native conspecific fish populations. An mtDNA D-loop segment of 978 bp from 213 bighead carp samples from 9 populations and a 975 bp segment from 204 silver carp samples from 10 populations were obtained to evaluate genetic diversity and population integrity. Results from a haplotype network analysis revealed that most haplotypes of the Pearl River clustered with those of Yangtze River origin and only a small proportion were distinct, suggesting that both the native Pearl River bighead and silver carp populations are currently dominated by genetic material from the Yangtze River. The genetic diversity of Pearl River populations is high in both species because of this inter-population gene flow, but the diversity of native Pearl River populations is low. To preserve the native genetic diversity, stocking of non-native fingerlings should cease immediately and native Pearl River bighead and silver carp fish farms should be established. This research demonstrates the danger to native biodiversity across China because of the substantial, ongoing stock-enhancement activities without prior genetic assessment.

11 citations

Journal ArticleDOI
TL;DR: Climate‐induced effects observed over time in the sites where trout were sampled have not yet led to local extinctions or distribution shifts, indicating a marked resilience of trout, probably due to the buffering effect of intrinsic population dynamics.
Abstract: Salmonids inhabiting Mediterranean rivers are of particular concern for biodiversity conservation, as they are threatened by various stressors, including habitat alterations, overfishing, climate change, and introgressive hybridization with alien species. In the Tiber River basin (Central Italy), genetic introgression phenomena of the native Salmo cettii with the non-native Salmo trutta hinder the separate analysis of the two species, which are both included in the S. trutta complex. Little is known about the factors currently limiting the trout populations in this area, particularly with respect to climate change. With the intention of filling this gap, the aims of the current study were to (a) quantify changes in the climate and (b) analyze the distribution, status, and ecology of trout populations, in the context of changing abiotic conditions over the last decades. Fish stock assessments were carried out by electrofishing during three census periods (1998-2004, 2005-2011, and 2012-2018) at 129 sites. The trend over time of meteorological parameters provided evidence for increased air temperature and decreased rainfall. Multivariate analysis of trout densities and environmental data highlighted the close direct correlation of trout abundance with water quality, altitude, and current speed. Climate-induced effects observed over time in the sites where trout were sampled have not yet led to local extinctions or distribution shifts, indicating a marked resilience of trout, probably due to the buffering effect of intrinsic population dynamics. Decreasing body conditions over time and unbalanced age structures support the hypothesis that variations in hydraulic regime and water temperature could overcome these compensatory effects, which may lead to a severe decline in trout populations in the near future. In a climate change context, habitat availability plays a key role in the distribution of cold-water species, which often do not have the possibility to move upstream to reach their thermal optimum because of water scarcity in the upper river stretches.

11 citations


Cites background from "Native and exotic fish species in t..."

  • ...…decreasing habitat availability seem to play a crucial role in the distribution and ecology of trout populations in the Tiber River basin, representing additional threats to native Mediterranean trout already endangered by the introduction of S. trutta (Caputo et al., 2004; Lorenzoni et al., 2006)....

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Journal ArticleDOI
TL;DR: The population structure, growth parameters and condition of chub, Squalius squalus, from the Assino Creek, a tributary of the River Tiber, were investigated by electrofishing and von Bertalanffy’s model.
Abstract: In this study, the population structure, growth parameters and condition of chub, Squalius squalus , from the Assino Creek, a tributary of the River Tiber, were investigated. A total of 1311 specimens were caught monthly from March 2008 to May 2009 by electrofishing. Total length (TL ± 0.1 cm) and weight (W ± 0.1 g) were recorded; age estimation was based on scalimetry and sex was determined by macroscopic observation of the gonads. Age composition ranged from 0+ to 11+ . Total length varied from a minimum of 4.1 cm to a maximum of 48.8 cm, for a weight of 0.5 g and 1233.0 g, respectively. Length-weight regression was log 10 W = −2.201 + 3.127log 10 TL for males and log 10 W = −2.273 + 3.190log 10 TL for females. Previous growth was determined with back-calculation from scale measurements using the non-linear Body Proportional Hypothesis. Theoretical length growth was estimated with von Bertalanffy’s model. Condition was evaluated by relative weight. In Italy there are few available data about the biology of Squalius squalus : the aim of this study was therefore to fill this lack of information by investigating some important aspects of the growth of the population in Assino Creek.

11 citations


Cites background from "Native and exotic fish species in t..."

  • ...42” E) is a left tributary of the River Tiber, one of the main rivers in Italy in terms of length and area of its basin (Lorenzoni et al., 2006)....

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  • ...The Assino Creek (43◦ 45’ 09.99” N, 12◦ 22’ 01.42” E) is a left tributary of the River Tiber, one of the main rivers in Italy in terms of length and area of its basin (Lorenzoni et al., 2006)....

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References
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Book
01 Jan 1992
TL;DR: The most widely read reference in the water industry, Water Industry Reference as discussed by the authors, is a comprehensive reference tool for water analysis methods that covers all aspects of USEPA-approved water analysis.
Abstract: Set your standards with these standard methods. This is it: the most widely read publication in the water industry, your all-inclusive reference tool. This comprehensive reference covers all aspects of USEPA-approved water analysis methods. More than 400 methods - all detailed step-by-step; 8 vibrant, full-color pages of aquatic algae illustrations; Never-before-seen figures that will help users with toxicity testing and the identification of apparatus used in the methods; Over 300 superbly illustrated figures; A new analytical tool for a number of inorganic nonmetals; Improved coverage of data evaluation, sample preservation, and reagant water; And much more!

78,324 citations

Journal ArticleDOI
TL;DR: It is hypothesized that producer and consumer communities characteristic of a given river reach become established in harmony with the dynamic physical conditions of the channel.
Abstract: From headwaters to mouth, the physical variables within a river system present a continuous gradient of physical conditions. This gradient should elicit a series of responses within the constituent...

9,145 citations


"Native and exotic fish species in t..." refers background in this paper

  • ...Fish assemblage composition varied along the Tiber River according to environmental variables, a common feature of stream fish communities (HUET, 1949, 1954, 1962; VANNOTE et al., 1980; MINSHALL et al., 1985; CHANGEUX, 1995)....

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  • ...Habitat controls the longitudinal distribution of fish, and changes in habitat characteristics are often associated with changes in the composition of the fish assemblage (HUET, 1949, 1954, 1962; VANNOTE et al., 1980; MINSHALL et al., 1985; MORIN and NAIMAN, 1990; CHANGEUX, 1995; BELLIARD et al., 1999; ARUNACHALAM, 2000; BUNN and DAVIES, 2000)....

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  • ...…of fish, and changes in habitat characteristics are often associated with changes in the composition of the fish assemblage (HUET, 1949, 1954, 1962; VANNOTE et al., 1980; MINSHALL et al., 1985; MORIN and NAIMAN, 1990; CHANGEUX, 1995; BELLIARD et al., 1999; ARUNACHALAM, 2000; BUNN and DAVIES, 2000)....

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Journal ArticleDOI
TL;DR: Alkalinity measurements are used in the interpretation and control of water and wastewater treatment processes and can be interpreted in terms of specific substances only when the chemical composition of the sample is known.
Abstract: 1. Discussion Alkalinity of a water is its acid-neutralizing capacity. It is the sum of all the titratable bases. The measured value may vary significantly with the end-point pH used. Alkalinity is a measure of an aggregate property of water and can be interpreted in terms of specific substances only when the chemical composition of the sample is known. Alkalinity is significant in many uses and treatments of natural waters and wastewaters. Because the alkalinity of many surface waters is primarily a function of carbonate, bicarbonate, and hydroxide content, it is taken as an indication of the concentration of these constitutents. The measured values also may include contributions from borates, phosphates, silicates, or other bases if these are present. Alkalinity in excess of alkaline earth metal concentrations is significant in determining the suitability of a water for irrigation. Alkalinity measurements are used in the interpretation and control of water and wastewater treatment processes. Raw domestic wastewater has an alkalinity less than, or only slightly greater than, that of the water supply. Properly operating anaerobic digesters typically have supernatant alkalinities in the range of 2000 to 4000 mg calcium carbonate (CaCO3)/L. 1

7,510 citations

Journal ArticleDOI
TL;DR: Given their current scale, biotic invasions have taken their place alongside human-driven atmospheric and oceanic alterations as major agents of global change and left unchecked, they will influence these other forces in profound but still unpredictable ways.
Abstract: Biotic invaders are species that establish a new range in which they proliferate, spread, and persist to the detriment of the environment. They are the most important ecological outcomes from the unprecedented alterations in the distribution of the earth's biota brought about largely through human transport and commerce. In a world without borders, few if any areas remain sheltered from these im- migrations. The fate of immigrants is decidedly mixed. Few survive the hazards of chronic and stochastic forces, and only a small fraction become naturalized. In turn, some naturalized species do become invasive. There are several potential reasons why some immigrant species prosper: some escape from the constraints of their native predators or parasites; others are aided by human-caused disturbance that disrupts native communities. Ironically, many biotic invasions are apparently facilitated by cultivation and husbandry, unintentional actions that foster immigrant populations until they are self-perpetuating and uncontrollable. Whatever the cause, biotic invaders can in many cases inflict enormous environmental damage: (1) Animal invaders can cause extinctions of vulnerable native species through predation, grazing, competition, and habitat alteration. (2) Plant invaders can completely alter the fire regime, nutrient cycling, hydrology, and energy budgets in a native ecosystem and can greatly diminish the abundance or survival of native species. (3) In agriculture, the principal pests of temperate crops are nonindigenous, and the combined expenses of pest control and crop losses constitute an onerous "tax" on food, fiber, and forage production. (4) The global cost of virulent plant and animal diseases caused by parasites transported to new ranges and presented with susceptible new hosts is currently incalculable. Identifying future invaders and taking effective steps to prevent their dispersal and establishment con- stitutes an enormous challenge to both conservation and international commerce. Detection and management when exclusion fails have proved daunting for varied reasons: (1) Efforts to identify general attributes of future invaders have often been inconclusive. (2) Predicting susceptible locales for future invasions seems even more problematic, given the enormous differences in the rates of arrival among potential invaders. (3) Eradication of an established invader is rare, and control efforts vary enormously in their efficacy. Successful control, however, depends more on commitment and continuing diligence than on the efficacy of specific tools themselves. (4) Control of biotic invasions is most effective when it employs a long-term, ecosystem- wide strategy rather than a tactical approach focused on battling individual invaders. (5) Prevention of invasions is much less costly than post-entry control. Revamping national and international quarantine laws by adopting a "guilty until proven innocent" approach would be a productive first step. Failure to address the issue of biotic invasions could effectively result in severe global consequences, including wholesale loss of agricultural, forestry, and fishery resources in some regions, disruption of the ecological processes that supply natural services on which human enterprise depends, and the creation of homogeneous, impoverished ecosystems composed of cosmopolitan species. Given their current scale, biotic invasions have taken their place alongside human-driven atmospheric and oceanic alterations as major agents of global change. Left unchecked, they will influence these other forces in profound but still unpredictable ways.

6,195 citations


"Native and exotic fish species in t..." refers background in this paper

  • ...Another problem is the introduction of exotic species, which is considered as one of the most important but least studied factors that disrupt aquatic ecosystems (MILLS et al., 1993; LEACH, 1995; LODGE et al., 2000; MACK et al., 2000; BYERS et al., 2002)....

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  • ...Literature regarding the impact of exotic species reports numerous examples of the extinction of native species (COWX, 1997; LODGE et al., 2000; MACK et al., 2000)....

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Journal ArticleDOI
01 Oct 1986-Ecology
TL;DR: In this article, a new multivariate analysis technique, called canonical correspondence analysis (CCA), was developed to relate community composition to known variation in the environment, where ordination axes are chosen in the light of known environmental variables by imposing the extra restriction that the axes be linear combinations of environmental variables.
Abstract: A new multivariate analysis technique, developed to relate community composition to known variation in the environment, is described. The technique is an extension of correspondence analysis (reciprocal averaging), a popular ordination technique that extracts continuous axes of variation from species occurrence or abundance data. Such ordination axes are typically interpreted with the help of external knowledge and data on environmental variables; this two—step approach (ordination followed by environmental gradient identification) is termed indirect gradient analysis. In the new technique, called canonical correspondence analysis, ordination axes are chosen in the light of known environmental variables by imposing the extra restriction that the axes be linear combinations of environmental variables. In this way community variation can be directly related to environmental variation. The environmental variables may be quantitative or nominal. As many axes can be extracted as there are environmental variables. The method of detrending can be incorporated in the technique to remove arch effects. (Detrended) canonical correspondence analysis is an efficient ordination technique when species have bell—shaped response curves or surfaces with respect to environmental gradients, and is therefore more appropriate for analyzing data on community composition and environmental variables than canonical correlation analysis. The new technique leads to an ordination diagram in which points represent species and sites, and vectors represent environmental variables. Such a diagram shows the patterns of variation in community composition that can be explained best by the environmental variables and also visualizes approximately the "centers" of the species distributions along each of the environmental variables. Such diagrams effectively summarized relationships between community and environment for data sets on hunting spiders, dyke vegetation, and algae along a pollution gradient.

5,689 citations