Diel patterns in spatial distribution of fish assemblages in lentic and lotic habitat in a regulated river

Fish assemblages in large rivers are governed by spatio‐temporal changes in habitat conditions, which must be accounted for when designing effective monitoring programmes. Using boat electrofishing surveys, this study contrasts species richness, catch per unit effort (CPUE), total biomass, and spatial distribution of fish species in the Saint John River, New Brunswick, Canada, sampled during different diel periods (day and night) and macrohabitats (hydropower regulated river and its reservoir) in the vicinity of the Mactaquac (hydropower) Generating Station. Taxa richness, total CPUE, and total biomass were significantly higher during night surveys, resulting in marked differences in community composition between the two diel periods. Furthermore, the magnitude of diel differences in catch rate was more pronounced in lentic than in lotic macrohabitats. The required sampling effort (i.e., number of sites) to increase accuracy and precision of CPUE estimates varied widely between fish species, diel periods, and macrohabitats and ranged from 15 to 185 electrofishing sites. Determining a correction factor to contrast accuracy and precision of day‐ with night‐time surveys provide useful insights to improve the design of long‐term monitoring programmes for fish communities in large rivers. The study also shows the importance of multihabitat surveys to detect differences in the magnitude of diel changes in fish community metrics.     

Fish assemblages and biotic integrity of a highly modified floodplain river,the Upper Mississippi,and a large,relatively unimpacted tributary,the Lower Wisconsin

The Upper Mississippi River is a dynamic floodplain river that has been largely transformed by navigational levees and dams since the 1930s. The pools upstream of each dam are lake‐like and only about the upper third of each reach retains a riverine character. In contrast, the Wisconsin River is not managed for commercial navigation and today its lower 149 km represent one of the least‐degraded large river reaches in central North America. Riverine reaches in both the Mississippi and Wisconsin rivers have similar macro‐habitats including numerous islands, large side channels, and connected backwaters and floodplain lakes. In this study, shoreline electrofishing samples were collected during summer 2002 and 2003 to characterize resident fish assemblages. We compared fish species abundance, biomass, and biotic integrity along main and side channel borders between the Upper Mississippi River and the Lower Wisconsin River. We expected that, in the absence of environmental degradation, fish composition and structure would be similar between the Mississippi and Wisconsin rivers, and between channel types within each river. Nonmetric multidimensional scaling and redundancy analysis revealed that fish species in the Mississippi River, unlike in the Wisconsin River, were characteristic of non‐riverine habitats. We consider non‐riverine fish assemblages indicative of environmental impairment. The main and side channel sites in the Mississippi River had more variable fish assemblages than the Wisconsin River. Analyses of fish index of biotic integrity scores showed that environmental condition was excellent for both channel types in the Wisconsin River, whereas in the Mississippi River the side channel was rated good and the main channel only fair. We conclude that differences between the two rivers and between channel types of the Mississippi River are consistent with direct and indirect effects of navigation. This study demonstrates the utility of a fish index of biotic integrity, an inexpensive and rapid bioassessment tool, for detecting change in ecological health on one of the world's largest rivers. Copyright © 2006 John Wiley & Sons, Ltd.     

Consistency of diel behaviour and interactions of stream fishes and invertebrates during summer

We examined the consistency of diel patterns observed in fish and aquatic invertebrates over three 24‐h cycles within a 10‐day period in summer (28–29 July, 4–5 and 7–8 August 1997) in the River Lee, Hertfordshire, England. We tested for temporal variations in epibenthos density and population size structure, age‐specific fish density, microhabitat use and contagion as well as for correlations between fish length and prey number (in the gut) per millimetre fish standard length, a surrogate of foraging success, and fish density in point samples (an estimator of shoal size). Consistent patterns were observed in invertebrates and fish, though variability was greater in the former. Epibenthic invertebrates (except Chironomidae) demonstrated few or no diel differences in density, but some differences in size (based on head widths) were found in larvae of Chironomidae and Ephemeroptera (mainly Baetis rhodani (Pictet) and Ephemerella ignita Poda) between times of day. Fish density varied consistently and diel variations were observed in fish shoaling behaviour, habitat use, prey size and prey composition. Prey numbers in the gut generally decreased with increasing shoal size, but this was significant in Gobio gobio L. only. In some fish species/size classes, prey numbers correlated either positively or negatively with habitat variables, in particular with the distance fish were captured from the bank. Despite relatively low epibenthic densities, Chironomidae larvae were a prominent and preferred food item in the diet of all fish species, followed by Ephemeroptera in some (0 + Barbus barbus (L.), 0 + and 1 + Barbatula barbatula (L.), 1 + and ≥ 2 + Cottus gobio (L.)) and Simuliidae in others (0 + and ≥ 1 +G. gobio, 0 + Leuciscus cephalus (L.), 0 + and 1 + Phoxinus phoxinus (L.)), with Trichoptera larvae, Asellus sp., Ostracoda and Annelida as tertiary prey taxa. The relatively consistent diel patterns observed suggest that data from single 24‐h cycles in late summer can be representative of daily patterns. Day‐time only surveys of European riverine fishes may give unreliable estimates of mean fish population size and abundance. Copyright © 2005 John Wiley & Sons, Ltd.     

EVALUATION OF RIPARIAN HABITAT RESTORATION IN A LOWLAND RIVER

For many years, navigable lowland rivers have been embanked artificially or suffered from substantial shipping wave action, leading to habitat degradation. Recently, riparian habitats were restored by creating foreshores and spawning grounds in the river Yser, a lowland river in Flanders, Belgium. The aim of this paper was to evaluate the role of these restored habitats for spawning and nursery of juvenile fish. To cover a wide range of anthropogenic disruption, four riparian mesohabitat types were selected and compared, ranging from semi‐natural over artificial spawning grounds and foreshores to artificial embankments. Juvenile fish were subjected to sampling by using electrofishing between June and September 2009 at different microhabitats located in five sites of each riparian mesohabitat type. Juvenile fish strongly preferred natural riparian habitats, whereas artificial embankments showed the lowest species richness, abundance and functional organization of juvenile fish species. Restored riparian habitats appeared to be an appropriate alternative for artificial embankments in navigable lowland rivers but still score significantly less than natural habitats. Juvenile fish avoided bare microhabitats but did not prefer any other microhabitat type (reed, woody or grassy vegetation), emphasizing the importance of microhabitat diversity. This paper provides valuable insights into riparian habitat restoration to river managers and stakeholders. Copyright © 2011 John Wiley & Sons, Ltd.     

Diel and lateral patterns of zooplankton distribution in the St. Lawrence River

While the four‐dimensional nature of river ecosystems has been recognized for nearly two decades, the role of lateral complexity has rarely been factored into studies of zooplankton ecology. We examined the importance of hydrologic retention areas (slackwaters) near islands and embayments of the St. Lawrence River for densities, fecundity, and diel migration of planktonic microcrustaceans. Densities of cladocera and copepods (nauplii and adult stages of cyclopoids and calanoids) were sampled from surface and deeper layers both at night (2100–0100 h, near the new moon) and during the day (1000–1400 h) for channel (deep‐fast), offshore (shallow‐slower), and inshore (shallow‐stagnant) habitats. Average zooplankton densities increased laterally from the main channel into the slackwaters with the exception of calanoid copepods, which peaked in the intermediate depths and flows of the offshore habitats. Although the ratio of males to females for the calanoid Eurytemora affinis and the cladoceran Bosmina spp. did not differ among habitats, a greater percentage of ovigerous cladoceran females were present in slackwaters than in channel habitats. Densities of microcrustaceans were generally greater during the night than day, suggesting diel vertical migration. By demonstrating both lateral and diel differences in the spatial distribution of riverine zooplankton, we refute the view of large rivers as well‐mixed homogenous systems. To the contrary, the two non‐random patterns that we document imply that there is an abiotic template that at least microcrustacean potamoplankton can exploit. In turn this suggests more research into the ecological significance of the pelagic structure of other large rivers like the St. Lawrence is justified. Copyright © 2007 John Wiley & Sons, Ltd.     

Large‐bodied fish assemblage characteristics in large rivers across Ontario

Large‐bodied fish assemblages were assessed in large rivers across Ontario. The objectives of this study were to (i) determine if there were relationships in large‐bodied fish species within rivers; (ii) determine what factors explain the variability in the abundance of large‐bodied fish within rivers across Ontario; and (iii) assessed variation in large‐bodied fish biodiversity among these river. Standardized index netting was conducted at 22 sites across 12 major rivers and sampled 3889 fish representing 26 species. Species associations were evident based on correspondence analysis. Walleye, Common White Sucker, Northern Pike and Lake Whitefish formed one group; Silver Redhorse, Shorthead Redhorse and Lake Sturgeon (adult and juvenile) formed another; Burbot, Longnose Sucker and Sauger were closely associated; and Cisco, Yellow Perch, Rock Bass, Smallmouth Bass and Brown Bullhead grouped. Canonical correspondence analysis was conducted to link species abundance patterns to environmental conditions. Walleye, Common White Sucker, Lake Whitefish and Smallmouth Bass were ubiquitous. Northern Pike abundance was negatively correlated with river discharge and longitude. Burbot, Sauger and Longnose Sucker abundance were positively correlated with deep rivers and discharge. Whereas Cisco, Yellow Perch and Rock Bass abundance were greater in wider rivers with lower discharge. Lake Sturgeon (adult and juvenile), Silver Redhorse and Shorthead Redhorse abundance were greater in narrow, longer rivers. Juvenile Lake Sturgeon abundance was positively correlated with longitude and river discharge. Mean species diversity and richness of large‐bodied fish among all sites was 1.58 (0.36 SD) and 7.7 (2.6 SD). Species diversity was not significantly related to any of the variables used in the Generalized Linear Model; however, species richness was significantly related to maximum depth. This study demonstrated subtle differences in environmental variables affecting large‐bodied fish at the landscape scale rather than those observed at the river scale.     

Performance of a Vertical‐Slot Fish Pass for the Sea Lamprey Petromyzon marinus L. and Habitat Recolonization

In 2011, a vertical‐slot fish pass was built at the Coimbra Açude‐Ponte dam (Mondego River, Portugal), approximately 45 km upstream from the river mouth. The performance of this infrastructure for sea lamprey passage was evaluated between 2011 and 2015 using several complementary methodologies, namely radio telemetry [conventional and electromyogram (EMG)], passive integrated transponder (PIT) telemetry and electrofishing surveys. During the study period, the electrofishing revealed a 29‐fold increase in the abundance of larval sea lamprey upstream of the fish pass. Of the 20 radio‐tagged individuals released downstream from the dam, 33% managed to find and successfully surpass the obstacle in less than 2 weeks, reaching the spawning areas located in the upstream stretch of the main river and in one important tributary. Fish pass efficiency was assessed with a PIT antenna installed in the last upstream pool and revealed a 31% efficiency, with differences between and within migratory seasons. Time of day and river flow significantly influenced the attraction efficiency of the fish pass, with lampreys negotiating it mainly during the night period and when discharge was below 50 m³ s^?1. Sea lampreys tagged with EMG transmitters took 3 h to negotiate the fish pass, during which high muscular effort was only registered during passage, or passage attempts, of the vertical slots. The use of complementary methodologies provided a comprehensive passage evaluation for sea lamprey, a species for which there is a considerable paucity of valuable data concerning behavioural, physiological and environmental influences on obstacle negotiation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.     

Fish community structure in natural and engineered habitats in the Kansas River

We investigated fish assemblage structure in engineered (rip‐rap) and natural habitats (log jams and mud banks) in the Kansas River USA to determine if natural structures had higher abundance and diversity of fishes at a local spatial scale. A total of 439 randomly selected sites were boat electrofished from May to August 2005 and 2006. Mean species diversity and richness were significantly higher in rip‐rap than log jams and mud banks. Mean relative abundance (CPUE; number of fish collected per hour electrofishing) of six of the 15 most common fishes (>1% of total catch) were most abundant in rip‐rap, two were most abundant in log jams, and none in mud banks. Rip‐rap had the highest relative abundance of fluvial specialist and macrohabitat generalists, whereas mean CPUE of fluvial dependents was highest in log jams. Although a discriminant function analysis indicated that nine size classes (eight species) discriminated among three habitat types, the high misclassification rate (38%) suggested a high degree of fish assemblage overlap among the habitats. Although previous work has suggested that engineered structures (rip‐rap) and urbanization are linked to reduced biotic diversity or reduced growth of fish species, our results suggest that at a local scale rip‐rap may not have the same negative impacts on fish assemblages. Published in 2009 by John Wiley & Sons, Ltd.     

Population Trends,Bend Use Relative to Available Habitat and Within‐River‐Bend Habitat Use of Eight Indicator Species of Missouri and Lower Kansas River Benthic Fishes: 15 Years After Baseline Assessment

A baseline assessment of the Missouri River fish community and species‐specific habitat use patterns conducted from 1996 to 1998 provided the first comprehensive analysis of Missouri River benthic fish population trends and habitat use in the Missouri and Lower Yellowstone rivers, exclusive of reservoirs, and provided the foundation for the present Pallid Sturgeon Population Assessment Program (PSPAP). Data used in such studies are frequently zero inflated. To address this issue, the zero‐inflated Poisson (ZIP) model was applied. This follow‐up study is based on PSPAP data collected up to 15 years later along with new understanding of how habitat characteristics among and within bends affect habitat use of fish species targeted by PSPAP, including pallid sturgeon. This work demonstrated that a large‐scale, large‐river, PSPAP‐type monitoring program can be an effective tool for assessing population trends and habitat usage of large‐river fish species. Using multiple gears, PSPAP was effective in monitoring shovelnose and pallid sturgeons, sicklefin, shoal and sturgeon chubs, sand shiner, blue sucker and sauger. For all species, the relationship between environmental variables and relative abundance differed, somewhat, among river segments suggesting the importance of the overall conditions of Upper and Middle Missouri River and Lower Missouri and Kansas rivers on the habitat usage patterns exhibited. Shoal and sicklefin chubs exhibited many similar habitat usage patterns; blue sucker and shovelnose sturgeon also shared similar responses. For pallid sturgeon, the primary focus of PSPAP, relative abundance tended to increase in Upper and Middle Missouri River paralleling stocking efforts, whereas no evidence of an increasing relative abundance was found in the Lower Missouri River despite stocking. Copyright © 2014 John Wiley & Sons, Ltd.     

Fish community structure associated with stabilized and unstabilized shoreline habitats,Coeur d'Alene River,Idaho, USA

Stabilization of riverbanks and lake shorelines has become widely used to reduce erosion. Studies on effects of stabilization on fish species and communities have indicated highly variable effects from beneficial to detrimental. Bank stabilization implemented to reduce shoreline erosion of metals‐contaminated sediments in the lower Coeur d'Alene River, Idaho, prompted concern of possible effects on the fish community. Fish sampling (electrofishing and gillnetting) and habitat assessment were conducted at 24 sites in the lower 54 km of river during 2005 and 2006 to assess differences in the fish community (relative abundance, species diversity and community composition) at stabilized and unstabilized shorelines. Within stabilized and unstabilized shorelines we evaluated seasonal differences as well as upstream and downstream differences. We captured 3511 fish from 17 species and 7 families; 83% of fish were captured by electrofishing. Fish relative abundance was significantly higher at stabilized than unstabilized sites for electrofishing. We also found positive correlations between relative abundance and diameter of rock at stabilized sites for both sampling gears. Three species (brown bullhead Ameiurus nebulosus, northern pike Esox lucius and pumpkinseed Lepomis gibbosus) were captured more readily at stabilized shoreline sites. Seasonally, the differences in relative abundance among habitat types indicate that stabilized structures are providing stable habitat year‐round. Overall, stabilized shorelines on the lower Coeur d'Alene River were not found to be adversely affecting overall fish relative abundance, diversity and species composition under the existing low fraction (2.5%) of bank stabilization. Based on these results and reviews of other studies, we suggest that two factors affecting the results of bank stabilization studies are (i) the habitat quality of the unstabilized river, and (ii) the percentage of the river that has been stabilized. Copyright © 2010 John Wiley & Sons, Ltd.     

Natal environments of age‐0 paddlefish in the middle Mississippi River inferred from dentary microchemistry

Effective management and conservation of riverine fish species relies on identification of habitats that contribute recruits to fish populations. Paddlefish are an important commercial and recreational species inhabiting North American large rivers. However, despite the knowledge of adult paddlefish movement patterns in large rivers, their principal natal environments and early life dispersal patterns remain unknown. Paddlefish dentary microchemistry can be used to identify natal environment of fish in large river networks such as the middle Mississippi River (MMR) and tributaries. The goals of this study were to (a) use dentary microchemistry (strontium:calcium ratios; Sr:Ca) to determine natal environment and potential drift for age‐0 paddlefish collected from the MMR and (b) assess whether MMR reach or year of collection influenced the percentage of recruits originating from different rivers. Age‐0 paddlefish were collected during 2010–2011 from two reaches of the MMR (upstream and downstream of the Kaskaskia River confluence). Water samples from the MMR and tributaries (upper Mississippi, Missouri, Illinois, Osage, and Kaskaskia Rivers) were collected during 2006–2016. Water Sr:Ca differed among rivers, enabling identification of natal environment for individual fish using dentary core Sr:Ca. The MMR (44–69% of fish sampled) and Missouri River (25–45% of fish sampled) were the primary natal environments for age‐0 paddlefish across both river reaches and collection years. The upper Mississippi River and smaller tributaries contributed few recruits (<13% of fish sampled). Conservation of paddlefish populations should include maintenance or improvement of connectivity between river reaches used for spawning and juvenile rearing and stock assessments of riverine paddlefish may need to be conducted at a riverscape scale because multiple rivers can contribute to paddlefish recruitment in a particular river reach.     

Nature‐like fishways as compensatory lotic habitats

Damming of rivers disrupts migration of fish and results in lotic habitats being both scarcer and spaced further apart, ultimately affecting riverine fish communities. Nature‐like fishways are often designed as bypass channels, constructed with natural materials that reroute part of the water around weirs and dams, restoring longitudinal connectivity as well as forming nature‐mimicking habitats. We evaluated the potential of such bypasses to function as compensatory lotic habitats by comparing fish fauna in 23 bypasses to adjacent lotic stream habitats in a same‐river pairwise design. Bypasses were narrower, shallower, and less shaded than adjacent stream habitats, but very few significant differences could be detected in the fish communities, indicating the potential of such nature‐like fishways to constitute compensatory lotic habitats for fish. Analyses also indicated how bypass design may be altered to favour or disfavour certain target species. Generally, narrower and shallower bypasses with high gradient favoured brown trout (Salmo trutta), whereas European eel (Anguilla anguilla) were more abundant at sites with lower gradient. Finally, to increase the impact of these compensatory habitats on running water ecosystems, we suggest that the size of bypasses should be maximized in areas where natural stream habitats have been lost.     

INTRA‐ANNUAL VARIATION IN RIVER–RESERVOIR INTERFACE FISH ASSEMBLAGES: IMPLICATIONS FOR FISH CONSERVATION AND MANAGEMENT IN REGULATED RIVERS

While much is known about the fish assemblages, habitats, and ecology of rivers and reservoirs, there has been limited study of the fish assemblages in transitional habitats between these lotic and lentic habitats. Data about these river–reservoir interface (RRI) fish assemblages are needed to guide integrated management efforts of river–reservoir ecosystems. The aim of these efforts is to recommend flows for natural river function, conserve native riverine fish assemblages, and maintain reservoir sport fisheries. We used a multigear approach to assess the fish assemblages of four RRIs in the Colorado River Basin, Texas. In addition to characterizing RRI fish assemblages using species richness and evenness metrics, and habitat‐use guilds, we used a multivariate approach to evaluate intra‐annual shifts in species composition and abundance. All RRIs had high species richness and evenness values and included both macrohabitat generalist and fluvial species. RRIs also contained high proportions of the fish species available within each river–reservoir ecosystem, ranging from 55% to 80%. Observed intra‐annual shifts in RRI fish assemblages resulted from changes in abundance of dominant species rather than changes in species composition, with abundance of most species increasing from early spring to summer. Fish species responsible for intra‐annual shifts included mostly floodplain and migratory species, suggesting that species both used littoral habitats within RRIs and migrated through RRIs to river and reservoir habitats. The diversity of fishes found within RRIs highlights the importance of including these areas in future conservation and management efforts of river–reservoir ecosystems. Copyright © 2013 John Wiley & Sons, Ltd.     

A COMPARISON OF TWO ELECTROFISHING PROGRAMMES USED TO MONITOR FISH ON THE ILLINOIS RIVER,ILLINOIS, USA

The Illinois River Biological Station monitors fish communities in the Illinois River using two different electrofishing programmes, one using three‐phase alternating current [AC; The Long Term Illinois Fish Population Monitoring Program or long‐term electrofishing (LTEF)] and the other pulsed direct current [DC; The Long Term Resource Monitoring Program (LTRMP)]. In 2001, we replicated three‐phase AC sampling sites with pulsed‐DC electrofishing gear to test for differences between the two collection methods and programmes. Electrofishing runs at each site were standardized by length and time, with 48 samples collected for each gear. Our objective was to test for differences in fish catch rates using total catch, species richness, fish size ranges, and sample composition and structure. Total catch was significantly greater for LTRMP electrofishing (4368 total fish, mean = 91.0 fish per sample) compared with LTEF electrofishing (1423 total fish, mean = 29.6 fish per sample). Species richness also was significantly greater for LTRMP electrofishing (50 total species, mean = 12.9 species per site) compared with LTEF electrofishing (38 total species, mean = 7.9 species per site). Size ranges of fishes, composed of 100‐mm‐length groups, showed higher total catches for the LTRMP within all length groups. Although our analyses suggest that collections from the LTRMP were significantly greater in most instances, a consistent pattern of species composition between the two programmes was not evident. Our results suggest that caution must be taken when attempting to compare fish community composition and structure information between these programmes. Copyright © 2011 John Wiley & Sons, Ltd.     

Fish assemblage patterns across a gradient of flow regulation in an Australian dryland river system

Hydrological regime, physical habitat structure and water chemistry are interacting drivers of fish assemblage structure in floodplain rivers throughout the world. In rivers with altered flow regimes, understanding fish assemblage responses to flow and physico‐chemical conditions is important in setting priorities for environmental flow allocations and other river management strategies. To this end we examined fish assemblage patterns across a simple gradient of flow regulation in the upper Murray–Darling Basin, Australia. We found clear separation of three fish assemblage groups that were spatially differentiated in November 2002, at the end of the winter dry season. Fish assemblage patterns were concordant with differences in water chemistry, but not with the geomorphological attributes of channel and floodplain waterholes. After the summer‐flow period, when all in‐channel river sites received flow, some floodplain sites were lost to drying and one increased in volume, fish assemblages were less clearly differentiated. The fish assemblages of river sites did not increase in richness or abundance in response to channel flow and the associated potential for increased fish recruitment and movement associated with flow connectivity. Instead, the more regulated river's fish assemblages appeared to be under stress, most likely from historical flow regulation. These findings have clear implications for the management of hydrological regimes and the provision of environmental flows in regulated rivers of the upper Murray–Darling Basin. Copyright © 2010 John Wiley & Sons, Ltd.     

A Comparison of Electrofishing and Visual Surveying Methods for Estimating Fish Community Structure in Temperate Rivers

Studies attempting to describe fish community structure in shallow riverine environments typically rely on electrofishing and/or visual (snorkelling) surveys, but few have addressed the relative efficiencies of these two methods at estimating fish density and biomass across wide ranges of geography, taxonomy and life history stages. Multiple paired electrofishing and visual surveys were conducted in 18 temperate Canadian rivers in order to obtain community‐wide density and biomass estimates from both methods. Partial canonical multivariate analyses were applied to the paired fish community matrices comparing the results of both surveying methods at the taxonomic levels of family, genus and species, as well as size classes within families and species, to assess the particular effectiveness of each sampling method. Although electrofishing estimates of family and species richness were generally greater, snorkelling surveys tended to generate higher density and biomass estimates for different size classes of many salmonid and cyprinid species. Moreover, mean river biomass estimates derived from visual surveying matched those obtained from our best mean river biomass estimates arising from the two methods combined. This study provides empirical evidence that electrofishing and visual survey methods generate different types of information when assessing fish community structure at the family level or by size classes. Our results provide ample background information for determining the most accurate sampling method for a particular fish community assemblage, which is fundamental to fisheries management and research. Copyright © 2014 John Wiley & Sons, Ltd.     

Low‐Head Dam Impacts on Habitat and the Functional Composition of Fish Communities

The natural flow regime of many rivers in the USA has been impacted by anthropogenic structures. This loss of connectivity plays a role in shaping river ecosystems by altering physical habitat characteristics and shaping fish assemblages. Although the impacts of large dams on river systems are well documented, studies on the effects of low‐head dams using a functional guild approach have been fewer. We assessed river habitat quality and fish community structure at 12 sites on two rivers; the study sites included two sites below each dam, two sites in the pool above each dam and two sites upstream of the pool extent. Fish communities were sampled from 2012 to 2015 using a multi‐gear approach in spring and fall seasons. We aggregated fishes into habitat and reproductive guilds in order to ascertain dams' effects on groups of fishes that respond similarly to environmental variation. We found that habitat quality was significantly poorer in the artificial pools created above the dams than all other sampling sites. Fast riffle specialist taxa were most abundant in high‐quality riffle habitats farthest from the dams, while fast generalists and pelagophils were largely restricted to areas below the downstream‐most impoundment. Overall, these dams play a substantial role in shaping habitat, which impacts fish community composition on a functional level. Utilizing this functional approach enables us to mechanistically link the effects of impoundments to the structure of fish communities and form generalizations that can be applied to other systems. Copyright © 2017 John Wiley & Sons, Ltd.     

Coping with hydrogeomorphic variations in a prairie river: resiliency in young‐of‐the‐year fishes

Young‐of‐the‐year (YOY) fish in sand‐bed rivers of grassland ecoregions frequently encounter dynamic habitat conditions produced by highly variable flow and resulting changes in geomorphic complexity of the river. How these vulnerable life history stages cope with changes in habitat condition and location is largely unknown. Therefore, we examined biodiversity and abundance of YOY fish (larvae and juveniles) at two spatiotemporal scales in response to dynamic flow conditions in the Kansas River. During the summer of 2004, we collected and identified 13 745 YOY fish from various moderate to zero‐flow habitats. Patterns of community structure through time were compared with the river's hydrogeomorphic characteristics, as determined by aerial photographs and measurements of instream flow rate and other water quality characteristics. Our initial hypothesis was that species richness and total YOY abundance would be maximized in larger and longer‐lived slackwater habitats. In contrast, our data suggest that dominant fishes in these highly dynamic ecosystems have adapted to hydrological variations with a more generalist lifestyle by either: (i) temporarily using higher flow habitats (except possibly the thalweg) to cope with intermittent loss of prime habitat; or (ii) extending spawning through favourable and demanding conditions. In contrast to current theories, our results suggest that conditions for YOY success are optimized in dynamic prairie rivers during the intermediate flows that maximize habitat heterogeneity and availability. Copyright © 2007 John Wiley & Sons, Ltd.     

Fish Community Support in Wetlands within Protected Embayments of Lake Ontario

Fish community data were collected to investigate the role of wetlands in supporting fish communities of protected embayments in Lake Ontario. Wetland and deeper, more open, littoral sites were sampled in five protected embayments using gill nets, fyke nets, minnow traps, and electrofishing gear during the summers of 2001 and 2002. Pooled gear data were used to analyze community composition, size frequency, and species richness. We found that even within protected embayments where community composition of both habitats is similar, wetlands support a community of fish different in species dominance and size structure than littoral embayment habitats. The abundance of young-of-year fish suggests that wetlands support fish populations by providing important nursery habitat. The similarity in fish community composition between wetland and littoral habitats indicates that wetlands remain important in supporting a subset of the embayment fish community. These results demonstrate that both wetlands and littoral areas in embayments are valuable and intensively utilized fish habitats that should receive special consideration in ecosystem management plans for the Great Lakes.     

Effects of habitat enhancement on 0‐group fishes in a lowland river

Loss of habitat complexity through river channelization can have adverse affects on riverine fauna and flora through reductions in abundance and diversity of species. Habitat enhancement schemes are used to improve the physical and biological heterogeneity of riverine habitats. Between 1996 and 1997 the Environment Agency undertook a habitat enhancement scheme on the Huntspill River, Somerset, England to improve conditions for coarse (non‐salmonid) fishes. The scheme involved reducing bank gradients and the construction of off‐channel bays in parts of the channel, all of which were planted with willow (Salix sp.) and common reed (Phragmites australis). The effectiveness of the enhancement scheme was investigated by comparing 0‐group fish assemblages in manipulated and unmanipulated sites. Abundance and diversity of 0‐group fishes was significantly higher in manipulated habitats. There was no significant difference detected in the effects of the different types of enhancement measure used. The significance of microhabitats produced by habitat enhancement schemes is discussed with respect to spawning, nursery and refuge sites for 0‐group coarse fish assemblages. Copyright © 2001 John Wiley & Sons, Ltd.