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  • 1
    Electronic Resource
    Electronic Resource
    Variation in fish community composition along an Iberian river basin from low to high discharge: relative contributions of environmental and temporal variables (2000)
    Copenhagen : Munksgaard International Publishers
    Ecology of freshwater fish 9 (2000), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract – Factors associated with the spatial and temporal variation of the lower Guadiana basin (southern Iberia) fish community were determined using data from 20 sites sampled during the summer of 1994 (dry year following a period of low discharge, total discharge from 1992 to 1994=1.45×109 m3) and again during the summer of 1996 (wet year following a period of higher discharge, total discharge from January 1995 to August 1996=6.18×109 m3). From the 17 explanatory variables initially considered six were retained for analysis by a forward selection procedure: maximum depth, altitude, channel width, substrate coarseness, SALT (a dummy variable identifying sampling locations belonging to tributaries that discharge to the brackish Guadiana) and YEAR (a dummy variable identifying the sampling year). Further, we partitioned the total variability in the Guadiana fish community into that accounted uniquely by selected environmental variables (34.9%), uniquely by sampling year (4.1%), by both sampling year and environmental variables (0.3%), and unexplained (60.7%)./〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0633.2000.90104.x
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  • 2
    Electronic Resource
    Electronic Resource
    Composition and spatial organization of fish assemblages in the lower Guadiana basin, southern Iberia (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 6 (1997), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract— A survey of fish assemblages (composition and spatial organization) was made in the lower Guadiana basin (southern Iberia) during the summer of 1994. A total of 6937 specimens belonging to 18 species were collected in 44 channel units and 30 sites (i. c. a series of channel units), comprising all the freshwater species previously recorded in the area except the exotic Esox lucius and the endemic endangered cyprinid Anaecypris hispanica. The endemic cyprinids Chondrostoma lemmingii and Barbus sclateri were rarely encountered, whereas the exotic Lepomis gibbosus was the predominant species found. The lower Guadiana fish community changed in space from assemblages characterized by the high relative abundances of Leuciscus pyrenaicus, smaller size-classes of Barbus spp. and Tropidophoxinellus alburnoides (all Iberian endemisms), to assemblages characterized by the high relative abundances of L. gibbosus, Micropterus salmoides, Cichlasoma facetum (all exotic species) and the larger size-classes of Barbus comiza and Barbus microcephalus. The former assemblages used smaller (i. e., narrow and shallow) sites and channel units, usually in tributaries and closer to headwaters, with smaller L. pyrenaicus being dominant in sites located in the tributaries discharging to the brackish Guadiana. This group was also related to channel units rich in emergent macropthytes. The latter assemblages were related to the largest sites and channel units, typically found in the main river or in tributary sites far from the source. Besides these two groups, some species were associated to noticeable environmental conditions; Blennius fluviatilis to channel units with current velocity and heterogeneous substrate, typically found in the main river, and Cobitis paludica to channel units with heterogeneous substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.1997.tb00155.x
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  • 3
    Electronic Resource
    Electronic Resource
    Microhabitat use by Iberian nase Chondrostoma polylepis and Iberian chub Squalius carolitertii in three small streams, north-west Portugal (2004)
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 13 (2004), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract –  Microhabitat use of Iberian nase Chondrostoma polylepis (Steindachner 1865) and Iberian chub Squalius carolitertii (Doadrio 1988) was studied in three small streams of the Lima basin, north-west Portugal. Measurements were made for 210 and 248 individuals, respectively, distributed in two size classes, based on fish ages, during winter, spring, summer and autumn 1998. Both species moved to shallow and slow-flowing microhabitats in summer and autumn, but this mainly reflected seasonal variation in microhabitat availability. Larger individuals of both species used deeper and lower percentage cover areas than smaller conspecifics, however significant ontogenetic differences were only found for water velocity. Different patterns of nonrandom microhabitat use were displayed by both cyprinids. Larger I. nase were in deeper and more discovered waters than those available in the habitat, whereas I. chub was over-represented in slow-flowing areas. There was no evidence of interspecific competition for microhabitat, therefore it is unlikely that spatial resource was limited during the present study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.2004.00054.x
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  • 4
    Electronic Resource
    Electronic Resource
    Efficacy of a nature-like bypass channel in a Portuguese lowland river (2005)
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 21 (2005), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Throughout Europe in the last decade there has been a steady shift away from more technical fish pass designs to more nature-like passes, such as nature-like bypass channels. Upstream fish passage in a nature-like bypass channel was investigated in a lowland river, the Lima River, for 117 days from March 2000 to May 2002. Fish passage was recorded using an automatic video recording system. Electrofishing samples within the bypass and below the weir were compared with species abundance found on the tape recordings. More than 7500 individuals of eight species passed through the bypass channel. Species composition was dominated by striped mullet (65.3%) and potamodromous species (34.3%), which used the bypass mainly at night. Of the environmental variables considered, bypass discharge explained most of the variation in the number of cyprinids, whereas water temperature was more important for diadromous species. Comparing species composition below the weir using passage recordings provided a useful tool to assess species efficacy of the bypass, although biological requirements should also be taken into account. This study proved the efficacy of the bypass for passage of almost all occurring species and life stages and also for providing suitable habitat for fish fauna, highlighting the use of these facilities for river restoration schemes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0426.2005.00616.x
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  • 5
    Electronic Resource
    Electronic Resource
    Intrabasin variations in age and growth of Barbus bocagei populations (2002)
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 18 (2002), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The age and growth of the Iberian cyprinid Barbus bocagei Steindachner 1865, were studied in six different streams in the River Tagus basin. The fish were aged by scale reading and their lengths were back-calculated. Age structures were similar at four sites (R. Ocreza, R. Rio Frio, R. Sever and R. Canha), where six to seven age classes were present. In contrast, 10 age groups were detected in the R. Erges and 11 in the R. Nabão. The slopes (b) of the length–weight regressions did not differ significantly between the six populations. The growth of the populations was compared with that available throughout the study area (another two sites). Classification analysis of the lengths-at-age by sites matrix revealed three major groups (by decreasing order of growth rate): 1, Belver Reservoir; 2, R. Tagus, Nabão and Erges; 3, Rio Frio, Sever, Canha and Ocreza. We hypothesize that highly stressful conditions in the summer diminish growth rates and longevity in the Rio Frio, Canha and Ocreza rivers and that lower temperatures all year round could limit growth in the Sever. Higher growth rates were observed in warm-water streams with more stable environmental conditions (group 2) and in a highly productive lentic system (group 1). Among the sites that were studied, the one that revealed the highest growth performance by B. bocagei was the most polluted, the R. Nabão. This offers evidence of the species plasticity and of its successful adaptation to streams displaying significant degradation in water quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0426.2002.00333.x
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  • 6
    Electronic Resource
    Electronic Resource
    Performance of fish lift recently built at the Touvedo Dam on the Lima River, Portugal (2002)
    Berlin Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 18 (2002), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: From March 1998 to February 1999, upstream fish passage was continuously monitored by video tape analysis at the fish lift Touvedo Dam on the Lima River, northern Portugal. A total of 1194 individuals from seven species were transferred by the lift. Cyprinids were the dominant group collected, with Iberian nase Chondrostoma polylepis (Steindachner) (31.8%) being the most abundant species, followed by Iberian barbel Barbus bocagei (Steindachner) (21.1%), Iberian dace Leuciscus carolitertii (Doadrio) (19.2%) and Iberian red roach Rutilus arcasii (Steindachner) (7.1%). Brown trout Salmo trutta fario (L.) and European eel Anguilla anguilla (L.) accounted for 10.8%, whereas Atlantic salmon Salmo salar (L.) was rarely observed. Most cyprinid seasonal movements were observed in the spring and were associated with reproduction. The timing of the run varied and its beginning appeared to be mainly dependent on water temperature. Roach, dace and nase used the fish lift intensively from mid-April until the end of summer. Barbel use of the lift intensified in mid-May in association with warmer water. Salmonids migrated in June–July and autumn. Significant differences were not found in hourly activity, except for nase and barbel, in June and July, respectively. Fish passage was not related to river discharge. The relative effectiveness of the fish lift is discussed in relation to the various species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0426.2002.00309.x
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  • 7
    Electronic Resource
    Electronic Resource
    To be, or not to be, a non-native freshwater fish? (2005)
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 21 (2005), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We examine the evolving concept of what constitutes a non-native (or alien) freshwater fish. In an attempt to distinguish between biogeographical and socio-political perspectives, we review the patterns in the introduction and dispersal of non-native fishes in Europe and North America, and especially the recent expansion of Ponto-Caspian gobies in Europe. We assess patterns in the development of national policy and legislation in response to the perceived threat of non-native fish introductions to native species and ecosystems. We review, and provide a glossary of, the terms and definitions associated with non-native species. Finally, we discuss perspectives as regards the future treatment of naturalized species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0426.2005.00690.x
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  • 8
    Electronic Resource
    Electronic Resource
    River plants from an Iberian basin and environmental factors influencing their distribution (1999)
    Springer
    Hydrobiologia 415 (1999), S. 101-107 
    Details
    ISSN: 1573-5117
    Keywords: fluvial macrophytes ; anthropogenic factors ; Portugal ; Mediterranean rivers ; canonical correspondence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract River plants were studied at 119 sites from a southern Iberian river basin. A site length of 50-100 m was found to be adequate for characterising local plant richness in these rivers. Average number of river plant species per site was 48 (range 21-76). Species richness showed a maximum at mid-course, with considerable variation in the upper course and a decreasing trend towards the floodplain. Sixteen environmental variables were initially considered to explain the biological variability. Nine, retained by the forward selection procedure, were significant predictors of the species distribution. Canonical correspondence analysis was used to directly relate plant species composition to these environmental variables. Altitude, conductivity, river width, pH, percentage of hard substrates and fine particulate organic matter on the river bed, average rainfall and temperature, and human-related disturbance were significantly related to the species distribution. Species positioned at the axes extremes could be arranged into species groups related to different geographical areas of the river system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003837802366
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  • 9
    Electronic Resource
    Electronic Resource
    Environmental factors related to the establishment of algal mats in concrete irrigation channels (1999)
    Springer
    Hydrobiologia 415 (1999), S. 163-168 
    Details
    ISSN: 1573-5117
    Keywords: macroalgae ; periphyton ; concrete canals ; Portugal ; redundancy analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The establishment of algal mats in concrete irrigation channels presents a serious weed problem in Mediterranean areas. These periphytic growths can reach two meters in filament length, 20 cm in mat thickness, 100% cover and 1 kg of fresh weight per square meter. These biological characteristics of the algal mats, and also of the drifting mats, present important temporal and spatial variation in the channel system. The species richness of the algae mats was low and only two macroalgae species were present. The diatom Biddulphia laewis was dominant in most channels. The green Oedogonium sp. was predominant in one channel characterised by lower conductivity and alkalinity, but with higher nutrient levels and this species also dominated in drift samples. Redundancy analysis showed that channel width and the residence time of the water in the channels were the variables that explained most of the variability in the biological data. Some water characteristics were of secondary importance, especially pH and temperature. Biotic factors, such as grazing, were only locally determinant. Water velocity did not present enough variation to create a gradient significantly affecting the biotic variables, except at specific locations, such as the control-gates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003841903275
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