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The lower lethal temperature of the endangered Rio Grande silvery minnow, Hybognathus amarus, was estimated from survival rates of fish overwintered in above-ground tanks. Temperature went to 0.0°C both winters. In 2012–2013, survival of Age class 0 fish was 79.87%, and in 2013–2014, survival of Age class 1 fish was 97.1%, suggesting that if Rio Grande silvery minnow is subjected to seasonal temperature changes, lower lethal temperature is ≤0.0°C. Results show that heating hatchery water in the winter is unnecessary. Additionally, current management guidelines that preclude reintroduction of the species into river sections where winter temperatures are ≤1°C must be reevaluated. 相似文献
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Daniel J. McGarvey 《Ecology of Freshwater Fish》2012,21(4):617-626
Plots of local versus regional richness have been used to test whether assemblages are ‘saturated’ with species. However, the validity of these tests is limited by scale‐dependence and arbitrarily defined sampling units, statistical autocorrelation between local and regional richness data, and the confounding effects of propagule pressure. In this study, local versus regional richness plots were used to test the saturation hypothesis for Pacific Northwest and Southeast (USA) fish assemblages, taking care to account for each of the above problems. Specifically, longitudinal river zones were used to ensure that the regional sampling units were not scale‐dependent or biologically arbitrary. A log‐ratio transformation was used to remove autocorrelation from the local and regional richness data. And a comprehensive fish stocking database was used to account for propagule pressure. Results suggest that the Pacific Northwest fish assemblages, which have low native richness, are not saturated, but the species‐rich Southeast assemblages are at or approaching saturation. 相似文献
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We investigated how stream fragmentation affects local fish species persistence and extinction from three Rio Grande systems (Texas, USA) stream reaches with different levels of natural fragmentation. We examined species–volume (SV) relationships of fish assemblages in 42 pools across the watersheds and predicted greater fragmentation would correspond to an increase in the slope of the SV relationship due to decreased within‐reach rescue effects. In addition, we examined relationships among tributary‐specific nested subset patterns, local habitat features and spatial position of the reaches relative to the Rio Grande mainstem to better understand the importance of local and regional processes on fish species richness patterns in the stream reaches. Slopes of the SV curves did not differ among the stream reaches, but the intercepts of the SV curves were significantly different. These results indicated rescue effects among habitats within a stream reach were not apparent; however, rescue effects from the mainstem largely determined the species richness of a given stream reach. The nested subset patterns in all stream reaches were related to several local environmental factors, and large, deep pools provided important aquatic refugia in all three systems. We suggest declines in mainstem and tributary flows will likely continue to impact local and regional fish assemblage attributes. High flow events are important for dispersal and can reset tributary fish communities for the next extinction‐driven, successional cycle. 相似文献
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Fish assemblages and seasonal movements of fish in irrigation canals and river reaches of the middle Rio Grande, New Mexico (USA) 总被引：1，自引：0，他引：1
Abstract – Synoptic fish surveys of river and irrigation canal sites and a path-analytic approach evaluate seasonal changes in fish assemblages in canal systems and river reaches of the middle Rio Grande, NM (USA). The objective was to assess how fish assemblages within the Isleta Reach respond to irrigation season and off-season variations in water and fish contributions from upstream river channels (Albuquerque Reach) and from the Peralta irrigation system. Eighteen species of fish were found in the irrigation canals, 13 in the Isleta Reach and 15 in the Albuquerque Reach. The proportion of nonnative fishes was higher in canals (56%) than in the river (11%). Species rank abundances were used in path analyses of fish species compositions during the irrigation season and off-season. During the irrigation season, path coefficients indicated fish movements downstream from the Albuquerque Reach (0.55) to the Isleta Reach exceeded contributions by the conveyance-return (0.29) and drain-return (0.05) canals. However, as the river de-watered the return canals were important refuge habitats for native fishes. The 0.05 value represented a major decline relative to the path coefficient for the upstream Peralta drain canal (0.72). During the off-season path coefficients indicated fish movements of 0.47 downstream in the river and 0.59 in the conveyance-return canal but a negligible value for the drain-return canal (-0.06). Irrigation management could be modified to favour native fish ecology by controlling movement of nonnative predators in canal systems and in providing refuge habitats for native fish during periods when water demand exceeds the supply. 相似文献
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Francisca C. Aguiar M. Teresa Ferreira António Albuquerque Ilídio Moreira 《水产资源保护:海洋与淡水生态系统》2007,17(4):335-347
- 1. A comparison was made between a variety of alien and endemic plant species from 272 aquatic and riparian habitats in Portuguese Mediterranean‐type streams in reference condition — i.e. near‐natural river corridors — and non‐reference condition. The objective was to detect differences in relative proportion and cover between these species groups. The differences in endemic and alien flora from siliceous and calcareous river types were also analysed. Environmental and human disturbance factors were related with the richness and cover of both species groups.
- 2. A total of 568 species were found, of which 44 were alien and 28 were endemic. Alien species were present at 91% of the surveyed locations, and were consistently more widespread at non‐reference sites than at reference ones for both river types, with calcareous sites having a higher invasibility. Endemic species occurred at 45% of the sampling sites and displayed a significantly lower richness and cover than their alien counterparts.
- 3. Alien richness and cover were positively related to direct human disturbance within the river systems, and with floodplain uses such as urban occupation, intensive agriculture, and nutrient inputs. Endemic species also respond to anthropogenic variables, rather than to climatic and geographical ones, with richness and cover increasing as human impacts on fluvial systems and related floodplains decrease.
- 4. Comprehensive control of alien invasive species and the protection of endemic plant populations will require attempts at monitoring ecological river integrity, and the achievement of ‘good ecological status’ — one of the goals of the European Union's Water Framework Directive. Portuguese riparian areas must be managed in such a way as to protect the relatively few preserved riparian habitats by lowering the direct and indirect pressures in fluvial corridors and thus preventing future alien plant invasions.
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Nested patterns of spatial diversity revealed for fish assemblages in a west European river 总被引：1，自引：0，他引：1
A. A. Ibarra Y.-S. Park S. Brosse Y. Reyjol P. Lim S. Lek 《Ecology of Freshwater Fish》2005,14(3):233-242
Abstract – The longitudinal distribution of fish assemblages across a large west European river basin, the Garonne river (south-west France) were investigated using a self-organising map. This nonlinear statistical method was employed to classify sampling sites according to their species composition. We found three main nested patterns in an aggregated hierarchy: a replacement and succession of species along a gradient without defined boundaries, four main zones of fish assemblages and an upstream-downstream shift of fish communities. We suggest that fish assemblages are too complex to be identified with a single species as in the zonation model, and that the diversity patterns found might be part of the same ecological process influencing fish assemblages on different spatial scales. Thus, discrepancies in the analysis of longitudinal patterns of fish communities in streams may have been basically a matter of local conditions and of conceptual perception. 相似文献
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河岸带水-陆生态系统具有较高的生物多样性,是区域生物多样性保护和恢复的重要节点,选择成都市近郊的新津县为代表区域,沿其境内的西河、南河、羊马河、杨柳河、金马河及岷江河岸带设置15个样地,对其境内主要河网河岸带系统的植物组成、区系特点、群落类型及多样性特征进行调查分析。结果表明,新津县河岸带维管束植物共有64科、159属、212种,受生境异质性及人类活动干扰的影响,河岸带之间植物群落丰度及物种组成差异较大,尤其仅出现在某一条河流河岸带的物种达75种;从系统整体性看,由不同河流组成的河网河岸带系统能够支持更高的物种丰度,且湿生植物比例更大,对维持区域生物多样性更有价值;河岸带系统的植物区系成分复杂,以热带、温带及世界广布性成分为主,表明区域河网河岸带生境条件的复杂性;基于TWINSPAN分析将区域河岸带网植物群落分为12个优势类型,其中金马河段和羊马河群落类型有7~8个,西河、南河和杨柳河有3~4个,受人类活动干扰最强的岷江干流仅1个;金马河、西河河段植物的物种多样性指数较高,南河和羊马河次之,杨柳河和岷江段较低。不同河流之间群落相似性较低,对维持河网系统物种多样性具有重要意义。 相似文献
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Reducing bacterial density in the semen of rainbow trout (Oncorhynchus mykiss) by applying gradient centrifugation and swim‐up washing methods 
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下载免费PDF全文 The objective of this study was to demonstrate the effectiveness of disinfection procedures to reduce bacterial load of rainbow trout, Oncorhynchus mykiss (Walbaum 1792), semen. Fresh semen was obtained from 3–4‐year‐old male species by abdominal sampling of sperm into pre‐cooled test tubes. After sperm cryopreservation and thawing, experiments were accomplished at 4–9°C. ‘Swim‐up’ and gradient centrifugation were used as a sperm washing method with commercial kits. Phosphate buffered saline was also used as washing solution. Bacterial growth tests were employed before and after washing the semen samples. Samples were inoculated on tryptic soy agar (TSA), modified Anacker and Ordal agar (MAOA) as well as brain heart infusion (BHI) agar. After using ‘swim‐up’ method for washing the semen, many bacterial colonies were observed. However, after semen washing with gradient centrifugation, lower bacterial growth was observed on TSA, MAOA and BHI. Some motile (40%) spermatozoa were obtained doing gradient washing procedure. Although sperm motility was not satisfactory, apparently the gradient centrifugation method reduced bacterial contamination as known from the mammalians. 相似文献
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Salinity and geomorphology drive long‐term changes to local and regional fish assemblage attributes in the lower Pecos River,Texas 下载免费PDF全文
下载免费PDF全文 River systems throughout arid regions worldwide have been heavily impacted by human activities, resulting in long‐term ecological consequences. The lower Pecos River in the Trans‐Pecos region of Texas is no exception, having undergone anthropogenic changes that include decreased flow, elevated salinity, species loss and species invasion. We compared historical and contemporary fish assemblage attributes from the Pecos River at local (site‐specific) and regional (Trans‐Pecos region) scales across a 24‐year time period. Fish assemblage data were collected in October 1987 and 2011, by seining at 15 sites spanning 430 km of the river in Texas. Additionally, we examined contemporary environmental conditions to determine species–environment relationships. We found that fish assemblages were significantly different between time periods, likely due to increased salinisation in the upper half of the study region. Decreased species richness, species replacement and increases in euryhaline species were documented in the upstream sites. Freshwater springs lower the salinity and maintain flows in the downstream reach, allowing for maintenance of the native fish fauna. Careful management of regional aquifers, irrigation practices and petroleum waste water will be necessary for protecting biodiversity and environmental flows in the lower Pecos River. 相似文献
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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. 相似文献
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Michele Silveira Coelho Bruna da Silva Menezes Silvia Leticia Rivero Meza Bruno Lainetti Gianasi Myriam de las Mercedes Salas-Mellado Margareth Copertino 《Journal Of Aquatic Food Product Technology》2013,22(7):1096-1106
ABSTRACTThis study was conducted to evaluate the biochemical and nutritional characteristics of naturally occurring estuarine macroalgae in the Patos Lagoon (Rio Grande, Brazil). The study of these macroalgae, dominated by Ulva and Cladophora species, contributes to current research on the potential utilization of green tide-forming algae. Although high levels of carotenoids (378 ± 0.02 µg g?1) and antioxidant activity (75.0% for DPPH) were found in the naturally occurring macroalgae, these macroalgae cannot be used in the food industry due to the presence of toxic levels of arsenic (exceeding the thresholds of both French and Brazilian legislation for food). Regarding the potential of the studied macroalgae as a biofuel source, the low lipid and very high carbohydrate contents suggest a possible use in the fermentation of ethanol, butanol, or methane. 相似文献
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Spatial and temporal patterns in fish community structure and abundance in the largest U.S. river swamp,the Atchafalaya River floodplain,Louisiana 下载免费PDF全文
下载免费PDF全文 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. 相似文献
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Ecological traits of fish assemblages from Mediterranean Europe and their responses to human disturbance 总被引：2，自引：1，他引：1
T. FERREIRA & J. OLIVEIRA N. CAIOLA & A. DE SOSTOA F. CASALS R. CORTES A. ECONOMOU & S. ZOGARIS D. GARCIA-JALON M. ILHÉU F. MARTINEZ-CAPEL D. PONT & C. ROGERS J. PRENDA 《Fisheries Management and Ecology》2007,14(6):473-481
Abstract Mediterranean river systems are characterised by more diverse fish assemblages and regional ecological processes compared with the rest of Europe. A data set from Mediterranean France, Iberia and Greece (∼2000 sites) was used to describe the characteristics of fish assemblages, explore their responses to anthropogenic disturbance and analyse the implications for river quality assessment. There was a southwards decline in species richness per site, but endemicity and proportion of alien species increased. Sites in the eastern Mediterranean had higher endemicity, lower site richness and lower number of alien species than sites in western Mediterranean Europe. Assemblage composition differed between Mediterranean sub-regions, but was dominated by three major fish types: a salmonid fish type common throughout the study area and two cyprinid-dominated fish types (in some sub-regions, Salmo trutta L. is present but not numerically dominant), corresponding to a gradient in hydrological and temperature regimes. Metric responses to perturbation were compared with those found at the European (larger scale) and basin (smaller scale) levels. Overall metric response was weaker in this Mediterranean application. The best responses to human pressure were usually obtained with abundance-based metrics and included the contribution of naturalised alien species. Some widespread alien species contributed to the response to anthropogenic alteration (notably Cyprinus carpio L. and Lepomis gibbosus (L.)). 相似文献