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Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions. 相似文献
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Fish nursery habitat function of the main channel,floodplain tributaries and oxbow lakes of a medium‐sized river 
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下载免费PDF全文 Small, adventitious tributaries (<3 orders of magnitude smaller than the stream it flows into) are a conspicuous feature of many river–floodplain systems, but their value as fish reproduction and nursery habitat is not well understood compared to oxbow lakes and the main river channel (MRC). Moreover, connectivity of tributaries to the MRC is often less impacted by anthropogenic modifications (e.g., dams and levees) compared to oxbow lakes. From April to July 2012, larval and juvenile fish were collected in the Fourche LaFave River (Arkansas, USA) system to better understand fish nursery habitat function of tributaries relative to oxbow lakes and the MRC. Nonmetric multidimensional scaling ordination of juvenile and larval fish genera revealed distinct fish assemblages in MRC and floodplain habitats. Ordination of juvenile fish at the species level resulted in distinct fish assemblages in tributary versus oxbow lake habitats. Tributaries had more unique species and higher abundance of shared species than oxbow lakes and MRC. Additionally, of the 46 species identified, all but six were collected in lower tributary reaches. Connectivity was strongly associated with both ordinations and was important in describing patterns of fish variation among habitats and between tributaries. Of the tributaries sampled, the least fragmented stream had the most similar fish assemblages between upper and lower sections. Findings of this study revealed tributaries are an important, yet overlooked, feature in the river–floodplain model. Especially in years of drought, channel–floodplain connectivity can be limited, but tributaries can be used by fishes for reproduction and nursery habitat. 相似文献
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Seasonal habitat use of alligator gar in a river–floodplain ecosystem at multiple spatial scales 下载免费PDF全文
下载免费PDF全文 Alligator gar (Atractosteus spatula) populations are declining throughout their range in the United States, even where considered stable. Similar declines in other riverine species are occurring worldwide due to alteration of habitat in river–floodplain systems. Most rivers in the world are highly regulated, resulting in departures from historic hydrology that provides connection to the floodplain habitats used by riverine fishes. Knowledge of the seasonal habitat requirements of alligator gar and similar riverine fishes at a watershed scale is limited, hindering management practices. We used radiotelemetry to monitor movements and habitat use of adult alligator gar (N = 32; 25.0–84.5 kg; 149–224 cm) at macro‐ and microhabitat scales during 2 years of varying hydrology. Fish showed seasonal differences in their use of main channel and floodplain macrohabitats. Floodplain tributaries and their upper reaches were especially important to reproductive ecology. Minimum distance travelled per day varied seasonally. While using the main channel Fourche LaFave River, gar selected low velocity, shallow depth and complex structure along channel margins. The Fourche LaFave River is unique in its connection to floodplain habitats on a relatively predictable basis, with frequent flooding during the spring and summer reproductive period. Our study emphasises the importance of connectivity between the main river channel and floodplain habitats to a floodplain‐obligate riverine species. An intact, heterogeneous riparian zone creates essential microhabitat for the species. Understanding habitat requirements of alligator gar at multiple spatial scales in a river–floodplain system is crucial to management of many other species and river systems. 相似文献
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The aim of this study was to describe the ontogenetic development of the testis and the alimentary tract in longnose gar (Lepisosteus osseus) related to fish size and age at the onset of exogenous feeding and late ontogenesis. Using light microscopy, testes were first detected histologically by the appearance of primordial germ cells 9 days after the first exogenous feeding [31–31.5 mm total body length(TL)] and presumptive seminiferous tubules (maleness characteristic) in fish of 107 mm TL. The present histological studies indicated that the alimentary tract of lepisosteids is completely functional at the beginning of exogenous feeding, several days before the completion of yolk absorption. Based on these results, we have concluded that garfish larvae/juveniles can be effectively trained to consume formulated diets at early stages, after an initial feeding of live food for 2–3 days (23.5 mm TL). Our findings provide evidence of the first controlled rearing of longnose gar using live and formulated diets, providing the possibility of experimental work with this non‐teleost fish. 相似文献
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Stimulatory effect of thyroid hormones improves larval development and reproductive performance in alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus) 下载免费PDF全文
下载免费PDF全文 Sergio Castillo Kent Bollfrass Roberto Mendoza Quenton Fontenot Juan Pablo Lazo Carlos Aguilera Allyse Ferrara 《Aquaculture Research》2015,46(9):2079-2091
Development of alligator gar (Atractosteus spatula) and spotted gar (Lepisosteus oculatus) larvae was evaluated after exposure of embryos to thyroid hormones (TH) by two different methods of administration. For the first method, alligator gar embryos were placed in a water bath with triiodothyronine (T3; 1 ppm for 2 h), and control treatment embryos were placed in a water bath without T3. For the second method, spotted gar adult males and females were injected with different TH during induced spawning: a group was injected with T3 [20 mg kg?1 body weight (BW)], a second group with thyroxine (T4; 20 mg kg?1 BW), a third group with thyroid‐stimulating hormone (TSH; 4 IU kg?1BW) and a control group with dimethyl sulfoxide. Both methods resulted in increases in the concentrations of T3 and T4 in embryos of both species. An increase in the alkaline enzymatic activity of TH‐treated larvae was observed as well as an increase in the RNA:DNA, RNA:Dry weight and DNA:Dry weight ratios at hatching. Some positive effects of TH application were: a significant increase in the hatching rate of spotted gar larvae from TH‐injected parents and a higher percentage of successful spawns. Evenness of larval sizes and a higher survival rate were observed in alligator gar larvae. Snout development was accelerated by TH treatment in both species. 相似文献
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Darwin Osorio John Terborgh Adriana Alvarez Hernán Ortega Roberto Quispe Vanessa Chipollini Lisa C. Davenport 《Ecology of Freshwater Fish》2011,20(4):619-627
Abstract – We report on lateral movements of fish between an Amazonian headwater river (Manu River in Manu National Park, Perú) and a 24‐ha oxbow lake (Cocha Cashu) in the adjacent floodplain. During wet season flood pulses, or ‘crecientes,’ fish can enter and exit the lake through a connecting channel that is normally dry. To investigate fish movements, we operated a bi‐directional funnel trap in the connecting channel during high water interludes. We captured 4090 fish of 60 species during the 2005 and 2006 rainy seasons and sub‐sampled the adults for gonadal state and stomach contents. We found that most exiting fish were gravid and that most entering fish had recently spawned, suggesting that fish were leaving the lake to spawn in the river or elsewhere. Entering fish had full stomachs more often than exiting fish and entering and exiting individuals of most species were of similar size. 相似文献
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Abstract – Spatial and temporal variation of species–environment relationships were evaluated for shallow-margin and deep-water fish assemblages in the Brazos River, a large floodplain river in Texas, USA. Total variation among the deep-water assemblages (11 species, 86% turnover across gill net samples) was greater than for shallow-margins (38 species, 64% turnover across seine samples). For both shallow-margin and deep-water assemblages, variation was greater among sites than between winter and summer seasons. Shallow-margin assemblage structure was related to depth, velocity and substrate, whereas for deep-water assemblages river discharge, temperature and velocity were important. Season itself accounted for little of the variation among either shallow (6.7%) or deep-water (2.3%) assemblages. Overall temporal patterns of shallow-margin samples appeared to show responses to juvenile recruitment, spates and migration of coastal fishes, whereas for deep-water samples, patterns related to use of reproductive habitats, juvenile recruitment and seasonal activity levels. Brazos River assemblages were less variable overall in comparison with studies along similar length of reach in headwater streams and wadeable rivers. The residual variation in species distribution (54% for shallow-margin and 67% for deepwater) that was not explained by instream variables and season suggests a greater influence of biotic interactions in rivers, particularly those across the spatially dynamic interface of main channel habitats and shallow river margins. 相似文献
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Roberto Mendoza Alfaro Carlos Aguilera González & Allyse M Ferrara 《Aquaculture Research》2008,39(7):748-763
Many lepisosteid populations in North America have declined and many are now threatened as a consequence of habitat loss and alteration and commercial and sport overfishing. Over the last two decades, morphological, histological and molecular studies allowed distinguishing between different phases of development and the nutritional condition of larvae. Ontogeny of the digestive enzymes of gar larvae indicated the possibility to feed them artificial feeds since early developmental stages. An in vitro digestibility system to test different feed ingredients has been used. Important characteristics of artificial diets were identified through different feeding experiments. Endocrinological studies showed the feasibility of altering larval development and the digestive capacity of larvae. Cloning of gar growth hormone opened new avenues to enhance growth in the gars. Plasmatic vitellogenin was isolated and purified, to develop a competitive enzyme‐linked immunosorbent assay, which allowed the straightforward separation of males from females to establish appropriate proportions for reproduction and also was used to evaluate hormonal protocols to induce gonad recrudescence and spawning. This review analyzes the biology, ecology and physiology of different gar species as a basis for their domestication, mass production of larvae for repopulation experiments and for the culture of commercial‐size gar. 相似文献
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对受损栖息地进行保护与修复是复苏河湖生态环境的重要举措。本文以赤水河河源段为研究区域，综合考虑区域内小水电拆除对鱼类栖息地的影响，依据AHP-熵权法，筛选了金沙鲈鲤、青石爬鮡、圆口铜鱼、岩原鲤、昆明裂腹鱼、长薄鳅六种优先保护鱼类，构建了基于河流地貌特征、水文、水质及鱼类等四方面的河道栖息地健康评价指标体系，建立了多尺度赤水河河源段栖息地综合评价标准。评价结果显示该河段仅30%河道栖息地为较好状况，50%河道栖息地处于一般状况，20%河道栖息地处于较差状况。小水电拆除可以有效恢复鱼类栖息地，但其质量仍需进一步提升，结合对研究区栖息地现状评估结果，可采取河道清理、卵砾石注入、河段平面形态修复等五种修复对策。 相似文献
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D. J. MURIE & D. C. PARKYN L. G. NICO J. J. HEROD W. F. LOFTUS 《Fisheries Management and Ecology》2009,16(4):315-322
Abstract Florida gar, Lepisosteus platyrhincus DeKay, were sampled in two canal systems in south Florida during 2000–2001 to estimate age, growth and mortality as part of the Everglades ecosystem-restoration effort. Tamiami (C-4) and L-31W canal systems had direct connections to natural wetlands of the Everglades and harboured large Florida gar populations. Of 476 fish aged, maximum ages were 19 and 10 years for females and males, respectively. Maximum sizes were also larger for females compared with males (817 vs 602 mm total length). Overall, female Florida gar from both Tamiami and L-31W were larger at age than males from L-31W that, in turn, were larger at any given age than males from Tamiami. Females also had lower rates of annual mortality ( Z = 0.21) than males from L-31W ( Z = 0.31) or males from Tamiami ( Z = 0.54). As a large and long-lived apex predator in the Everglades, Florida gar may structure lower trophic levels. Regional- and sex-specific population parameters for Florida gar will contribute to the simulation models designed to evaluate Everglades restoration alternatives. 相似文献
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Michael A. Nannini Jodi Goodrich John M. Dettmers Daniel A Soluk David H. Wahl 《Ecology of Freshwater Fish》2012,21(4):499-509
The spatial and temporal complexity of large river ecosystems likely promotes biological diversity within riverine larval fish assemblages. However, the focus of most previous riverine studies of larval fish distribution has tended to concentrate mainly on backwater habitats. There has been less focus on the value of the main channel for larval fishes. We sampled two habitats types (three main channel sites and three backwater lakes) along 20 km of the Illinois River ecosystem during 2 years to compare the larval fish distribution along both spatial and environmental gradients between these habitats. Across the 2 years of this study, we found similar trends in the spatial and temporal distribution of larval fish, although there were some differences in densities between years. The relative abundance and size of many of the different fish taxa varied among habitats. Centrarchids, clupeids, poeciliids, cyprinids (excluding common carp) and atherinids were more abundant within backwater lake habitat. In contrast, common carp (Cyprinus carpio), sciaenids, moronids and catostomids were more abundant in main channel habitats. Furthermore, sciaenid and clupeid larvae captured in the backwater lake habitat were larger as the season progressed than those captured in the main channel. Our study suggests that larval fish show habitat specialisation, similar to adults, indicating that both the backwater lakes and the main channel are both important for larval fish and preserving the diversity of the fish assemblages in large floodplain rivers. 相似文献
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- 1. Three classes of habitat used by groups of fish species classified as conservation and management priorities were developed for the Gerua River (also known as the Girwa River, Karnali River) in the Ganges river basin. This river is large (mean annual discharge ca 1500 m3 s?1, up to 900 m wide), surrounded by protected lands of India and Nepal, and upstream of major diversions and river alterations.
- 2. Fish and habitat sampling was conducted at 45 sites from 2000 to 2003. Data were analysed for 2172 fish of 14 species. Species and life stages found occupying a statistically distinct subset of the river habitats were grouped to identify classes of river habitat for conservation.
- 3. Most species and life‐stage groups specialized on specific habitat conditions revealed by multivariate analyses of variance and a principal component analysis. The most numerous and diverse group (six species, 15 life stages) was associated with deep depositional habitats with sandy substrate. Two species covering three life stages were primarily oriented to erosional habitat marked by fast current velocity with pebble and cobble substrate. A third group of three species of adults and juveniles were intermediate in habitat use.
- 4. River conservation for fish faunas should maintain both erosional and depositional channel habitats with depths, substrates, and current velocity inclusive of the ranges reported. The erosional and depositional nature of the key habitats requires that rivers be maintained with flows capable of channel‐forming functions.
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Emma G. Easterly Daniel A. Isermann Joshua K. Raabe Joshua W. Pyatskowit 《Ecology of Freshwater Fish》2020,29(2):311-324
Dam removals allow fish to access habitats that may provide ecological benefits and risks, but the extent of fish movements through former dam sites has not been thoroughly evaluated for many species. We installed stationary PIT antennas in 2016 and 2017 to evaluate movements and survival of brook trout Salvelinus fontinalis in the West Branch of the Wolf River (WBWR) in central Wisconsin following removal of two dams and channel modifications designed to promote fish movement. These changes provided access to lacustrine habitats that might provide suitable winter habitat or act as ecological sinks. We used multistate models to estimate transition probabilities between river sections, to determine whether brook trout: (a) moved between multiple river sections and (b) entered lacustrine habitats as seasonal refuges, but eventually returned to lotic habitat. We also used a Cormack-Jolly-Seber model to evaluate whether apparent survival of brook trout in the WBWR was comparable to other populations. Few fish moved among river sections or used lacustrine habitat (<5% of tagged fish); most brook trout remained in sections where they were initially tagged, potentially due to quality habitat located throughout the river. Like other studies, brook trout in the WBWR appear to experience high mortality based on low number of detections, few physical recaptures and an estimated eight-month apparent survival rate of 0.27. In scenarios where fish can already access suitable habitat, removal of dams may not result in substantial increases in fish movement and colonisation of newly accessible habitat may not occur immediately. 相似文献
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- 1. River restoration is now widely undertaken and may be considered an increasingly important aspect of river management. Recent developments in European legislation (Habitats Directive and the Water Framework Directive) should give further impetus to river restoration across EU member states, as this legislation places greater emphasis on the processes that support river ecology.
- 2. Traditional river restoration approaches have been reach‐focused and opportunistic, capitalizing on flood defence works and the cooperation of sympathetic landowners.
- 3. Furthermore, many schemes have been species‐ or habitat‐driven and, thus, have sought to recreate channel forms believed to be favoured by particular species or associated with particular habitats. Such approaches have not always given due attention to the underlying geomorphological processes that create channel form and, consequently, the schemes have not been self‐sustaining, requiring continued management input.
- 4. Consistent with the ethos of the Water Framework Directive, an eco‐hydromorphic approach to river restoration is proposed here. This approach views spatial and temporal heterogeneity as fundamental characteristics of fluvial systems and advocates recreating a framework within which natural processes, such as sediment transport and nutrient dynamics, can occur.
- 5. Mesoscale habitat approaches are considered as one possible way to plan and achieve this framework, providing the potential to link the wide range of spatial and temporal scales that characterize river systems.
- 6. It is argued that river restoration will only be sustainable if it is undertaken within a process‐driven and strategic framework with inputs from a wide range of specialists. Such an approach needs to be reviewed constantly in light of appraisal and monitoring of previous river restoration schemes.
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Environmental and spatial processes: what controls the functional structure of fish assemblages in tropical rivers and headwater streams? 下载免费PDF全文
下载免费PDF全文 In this study, we investigated functional structure patterns of tropical headwater and river fish assemblages. We hypothesised that environmental conditions are primarily structuring headwater streams leading to functionally clustered assemblages, whereas processes that favour functional overdispersion would guide river assemblages. For 27 headwater streams and 22 rivers, we used eight functional traits for calculating two functional indexes: mean pairwise distance (MPD) and net relatedness index (NRI). We performed linear regressions between indexes and species richness, a multiple regression between NRI and eight environmental variables and a variation partitioning to disentangle the role of environment and space on NRI. Our findings indicate that fish assemblages of headwaters are structured by environmental conditions as most assemblages in this habitat displayed a tendency to clustering and MPD/NRI were not correlated with species diversity, whereas the opposite pattern was observed for river habitat. Four environmental variables (channel depth, water velocity, dissolved oxygen and turbidity) explain 56% of functional structure variation. These variables seem to function as selective filters in headwaters, whereas channel depth may be determinant for functional overdispersion of river fish assemblages. Components associated with space are also influencing the functional structure. Limitations of species dispersal through space (between both habitat types) appear as a possible cause to this. In this sense, both environmental conditions and processes linked with space are capable of influencing the functional structure of tropical headwater streams and river fish assemblages. 相似文献
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Lateral migration of Arapaima gigas in floodplains of the Amazon 总被引：1，自引：1，他引：0
L. Castello 《Ecology of Freshwater Fish》2008,17(1):38-46
Abstract – This study deduced in detail the lateral migration –those between river channels and floodplain habitats – of the pirarucu ( Arapaima gigas ), a giant, obligate air-breathing species of the Amazon Basin. Over a thousand samples of the pirarucu were taken through counts of the individuals performed at the moment of aerial breathing; these samples were taken in eight habitats of a floodplain near the Amazon River every week throughout an entire flood cycle. The lateral migration of the pirarucu accompanied water level fluctuations closely. As water levels rose, the pirarucu migrated to increasingly higher habitats in flooded forests and remained there during high water levels. As water levels declined, the pirarucu migrated first back to lower habitats of flooded forests, then to communicating channels, and, eventually, to the lakes, where they remained during low water levels. These results allow for a conceptual model of lateral migration of floodplain fishes. 相似文献