Stream bed organic carbon and biotic integrity

• 1. Allochthonous carbon is the basis of the detrital food web in low‐order, warmwater stream ecosystems, and stream‐bed sediments typically function as carbon reservoirs. Many of the same factors that govern carbon input and storage to streams (e.g. riparian vegetation, large wood, heterogeneous boundaries) have also been identified as key attributes of stream fish habitat.
• 2. Effects of channel incision on sand‐bed stream carbon reservoirs and indices of biological integrity (IBIs) based on fish collections were examined for four streams exhibiting a range of incisement in northern Mississippi. Observed mean C concentrations (mass percentage) ranged from 0.24±0.36% for a non‐incised stream to only 0.01±0.02% for a severely incised channel, and were not correlated with large wood (LW) density, perhaps because LW density at one site was elevated by a habitat rehabilitation project and at another site by accelerated inputs from incision‐related riparian tree fall. Fish IBI was positively correlated with bed C (r=0.70, p=0.003), and IBIs for reference streams were more than 50% greater than those computed for the most severely degraded sites.
• 3. More testing is needed to determine the efficacy of stream bed C as an indicator, but its importance to warmwater stream ecosystems, and the importance of covarying physical and hydrologic conditions seems evident.

Published in 2008 by John Wiley & Sons, Ltd.     

Fish use of ecohydraulic‐based mesohabitat units in a low‐gradient Illinois stream: implications for stream restoration

• 1. A classification scheme for ecohydraulic‐based mesohabitat units was developed for a summer low‐flow period. Mesohabitat unit designations were based on the integration of three‐dimensional channel hydraulics, geomorphic maintenance processes of bed morphology, and biological resource needs of fish. Ecological relevance of the units was evaluated by a study of fish mesohabitat use patterns, and species relationships to feeding guild. By portraying the stream as a mosaic of hydraulic habitat patches that provide specific biotic resource needs, this study's aim was to advance how ecological information may be incorporated into the stream restoration design process.
• 2. Nine mesohabitat units were designated, including pool‐front, ‐mid, and ‐rear units, scour pool, simple and complex riffles, glide, submerged point bar, and channel expansion marginal deadwater. Physical habitat structure differed among the nine mesohabitat units by length, water depth, and bed slope and complexity. Fish were collected in specific unit volumes by use of prepositioned areal electrofishing devices, in which distinct patterns of fish mesohabitat use were observed.
• 3. A key finding was the differences in fish assemblages among the pool units, in which fish densities were greatest in the pool‐front and scour pool units. Also, fish density in the pool‐front unit was positively correlated with pool entrance slope. Biomass was greatest in the pool‐front and ‐mid units, and it was correlated with maximum mid‐pool depth. Density and biomass were generally lowest in the pool‐rear unit. Other unique relationships were also observed among the mesohabitat units.
• 4. Based on feeding guild, patterns of fish mesohabitat use were observed for this summer low‐flow period; insectivores dominantly used pool‐front and scour pool units, herbivores dominantly used complex riffle units, and piscivores used pool‐front and ‐mid units.
• 5. Useful ecological information was derived from fish species‐habitat relationships observed in this study, linking mesohabitat units with species requirements for food resources. Such findings support advancements to ecological design strategies for stream restoration that promote hydraulic habitat diversity.

Copyright © 2008 John Wiley & Sons, Ltd.     

Associations between stream hydrogeomorphology and co‐dependent mussel–fish assemblages: evidence from an Ohio,USA river system

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Experimental provision of large woody debris in streams as a trout management technique

• 1. The natural stock of large woody debris (LWD) in the afforested Douglas River (Fermoy, Co. Cork) is very low relative to old‐growth forests, which seems to arise from deficiency both of supply and retention. Woody debris is important to the ecology and physical structure of forest streams, so its abundance is relevant to aquatic conservation and the maintenance and size of salmonid fish stocks.
• 2. The physical characteristics and fish stocks of 16 contiguous segments of two 200 m stream reaches were surveyed in spring 1998 prior to the installation of 12 partially spanning debris structures on four of the segments. This study investigated the effect of debris structures on the heterogeneity of flow and substratum, and the distribution of brown trout (Salmo trutta), and assessed the potential use of woody debris manipulation as a tool in the management of forest streams.
• 3. Surveys of stream habitat conditions over a 2 year period following the installation of woody debris showed a change in stream architecture. This created more suitable habitat for trout through development of additional pools in which beds of fine sediment developed, and constraining the main current, increasing the amount of eddies and slack water areas.
• 4. There were significant increases in trout density and biomass in the debris segments relative to control segments without debris dams 1 and 2 years after debris addition, although trout condition was not modified by the addition of LWD. These results suggest that the addition of woody debris offers a positive and practical management technique for enhancing fish in plantation forest streams.

Copyright © 2002 John Wiley & Sons, Ltd.     

Re-establishment of Danish streams: Restoration and maintenance measures

• 1. Prior to 1983 the Danish legislation concerning streams gave priority to drainage of water. The revision of The Watercourse Act gave balanced priority to drainage of water and environmental quality, focusing on an ecologically more appropriate maintenance practice and giving special provisions for stream restoration activities.
• 2. Different measures of single structure restoration have been used, the most common being replacement of weirs, dams or other obstacles by rapids, establishment of salmonid spawning grounds, and installation of new or improved fish ladders.
• 3. The most common stream channel restoration method is integrated use of a number of single structure measures. Establishment of a two-stage channel and re-opening of small piped streams have also been used. Stream valley restoration includes restoration of old meanders or establishment of a new sinuous channel and involves the adjacent riparian areas.
• 4. The changed stream maintenance practice involves a new strategy for dredging and cutting of weeds and bank vegetation in order to minimize the ecological damage caused by keeping a reasonable discharge capacity. In 1990, environmentally acceptable weed-cutting was performed in 37% of all municipal streams and the bank vegetation was left uncut in a third of the streams. Similarly, more than half of the county streams were maintained using hand scythes and in 74% of the streams the bank vegetation was left uncut.
• 5. Quantitatively, stream restoration has contributed little to the general improvement of Danish streams compared with changed maintenance practice. Stream restoration projects create public interest in the environmental quality of streams, but major improvements in the physical properties of Danish streams depend on future maintenance practice.
• 6. Due to major changes predicted in Danish agriculture many riparian areas and wetlands will reappear and the natural or semi-natural physical properties of streams will be re-established by natural processes or changed in maintenance practice. However, there will still be large areas with intensive agriculture, where environmental and agricultural interests must be balanced. The Danish experience has shown that this is possible.

     

Mixed stream channel morphologies: implications for fish community diversity

• 1. Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant.
• 2. Twenty‐five stream reaches in north‐western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool‐riffle, mixed (i.e. pool‐riffle/cascade, pool‐riffle/other) and forced pool‐riffle stream morphological groups. Stream reach surveys included cross‐sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys.
• 3. Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon–Weaver Index (H′); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P?0.05), with pool‐riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool‐riffle the lowest.
• 4. These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool‐riffle/cascade and pool‐riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool‐riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies.
• 5. These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional‐distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts.

Copyright © 2008 John Wiley & Sons, Ltd.     

The local responses of aquatic ecosystems to adjacent grassland conservation: Can streams of dreams exist in a degraded riverscape?

1. Landscape homogenization and the removal of riparian areas have altered stream ecosystems worldwide. Numerous conservation programmes attempt to improve water quality and increase instream habitat heterogeneity to elicit desired biological responses. However, the effectiveness of many conservation efforts on isolated stream fragments remains unknown, especially in grassland regions.
2. The effects of grassland conservation practices and the re-establishment of riparian corridors in the James River basin, South Dakota (USA) on stream water quality, habitat availability and aquatic macroinvertebrate and fish assemblages were studied in an agriculturally dominated prairie landscape.
3. Grassland conservation efforts may have repaired riparian condition, reduced turbidity and created more diverse instream habitat complexes at conservation sites based on comparisons with paired reference reaches. Reference sites were relatively homogeneous, with prevalent siltation, bank erosion and disturbances to the riparian vegetation. Owing to significant riparian vegetation development, overhanging and aquatic vegetation, benthic detritus and woody materials were significantly more common at conservation reaches.
4. Restoration efforts that assume ‘if you (re-)build it, they will come’ (i.e. the ‘field of dreams’ hypothesis) underestimate other important barriers to biodiversity restoration in dynamic, grassland riverscapes. Although aquatic organisms in grassland ecosystems are adapted to rapidly inhabit available habitats, the development of niche space at conservation reaches did not directly result in colonization by aquatic life.
5. Grassland management actions did not address stream connectivity issues or overcome land use influences elsewhere in the riverscape that may govern the responses of aquatic macroinvertebrates and fish. Stream fragmentation and continuing, damaging land use patterns seemed to exceed the positive effects of restoring isolated stream reaches in these heavily degraded catchments. Catchment-scale management strategies that combine reach-level restoration actions with efforts to improve connectivity are likely to be more successful in degraded riverscapes.

     

Floods,drying, habitat connectivity,and fish occupancy dynamics in restored and unrestored oxbows of West Central Iowa,USA

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Evaluating habitat associations of a fish assemblage at multiple spatial scales in a minimally disturbed stream using low‐cost remote sensing

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Country‐wide analysis of large wood as a driver of fish abundance in Swedish streams: Which species benefit and where?

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Factors associated with distributions of six fishes of greatest conservation need in streams in midwestern USA

1. Many fish species of greatest conservation need (SGCN) in Iowa and Minnesota, USA, have been in decline for decades. A key reason for the decline is the alteration and degradation of naturally flowing streams owing to land use changes resulting from agricultural practices. Populations of several fishes have been adversely affected by widespread stream channelization that has resulted in more homogeneous stream habitats throughout Iowa and Minnesota.
2. The goal of this study was to determine the abiotic and fish assemblage characteristics associated with the presence of these rare fishes. Electrofishing and seining were used to sample fish assemblages and 43 abiotic characteristics were measured at 111 sites in the North Raccoon and Boone River basins in central Iowa and the Rock River and Beaver Creek basins in north-west Iowa and south-west Minnesota during 2016 and 2017.
3. Six SGCN, including the federally endangered Topeka shiner (Notropis topeka), were included in statistical modelling to determine habitat and fish assemblage characteristics associated with their presence.
4. Species-specific nonmetric multidimensional scaling ordinations indicated that abiotic characteristics and fish assemblages often differed between sites where SGCN were present and absent. Random forest and logistic regression models suggested that the presence of four of six SGCN were positively associated with species richness, whereas all other 10 important abiotic and fish assemblage variables were unique to only one or two of the six SGCN.
5. Topeka shiners were present at 36% of sites and were positively associated with orangespotted sunfish (Lepomis humilis) catch per unit effort while being negatively associated with canopy cover and fantail darter (Etheostoma flabellare) catch per unit effort.

     

Effect of an intensive mechanical removal effort on a population of non‐native rainbow trout Oncorhynchus mykiss in a South African headwater stream

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Priority habitats for the conservation of large river fish in the Ganges river basin

• 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.

Copyright © 2006 John Wiley & Sons, Ltd.     

Fish assemblages of Red Sea backreef biotopes

• 1. Fish assemblages of shallow‐lagoonal biotopes (seagrass beds, coral patches, reef flat and sand) were examined within the Nabq Managed Resource Protected Area (MRPA), South Sinai, Egypt. This protected area supports a small‐scale artisanal Bedouin fishery, managed by gear restrictions and a network of no‐take zones (NTZs).
• 2. Coral patches showed highest species richness and diversity of fish, followed in order by the reef flat, shallow seagrass beds and sandy bottoms.
• 3. There were clear differences in fish assemblages between the biotopes surveyed, little differences between sampling areas and no significant differences in fish assemblages between no‐take and take zones, suggesting species characteristic of these shallow‐water biotopes are dispersed along the coast irrespective of fishing pressure.
• 4. Nine species (Acanthurus nigrofuscus, Asterropteryx semipunctatus, Cryptocentrus caeruleopunctatus, Cheilio inermis, Thalassoma rueppellii, Lethrinus mahsena, Lethrinus nebulosus, Parupeneus forsskali and Pomacentrus trilineatus) had a 95% correlation to the pattern of assemblage distribution, indicating these species are the most important determinants of the fish community.
• 5. Approximately one‐third of fishes recorded appeared to be juveniles, with seagrass beds having a particularly high proportion of juvenile fish, including several commercial species.
• 6. The structure of the fish assemblage and fish size suggests that shallow‐water biotopes in Nabq MRPA may be acting as nursery areas of commercial fish for the Bedouin fishery.

Copyright © 2006 John Wiley & Sons, Ltd.     

The effect of planting grass filter strips on fishes in agricultural headwater streams

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Influences of in-stream habitat and upstream land-use on site occupancy of the Kanawha darter (Etheostoma kanawhae): A narrowly distributed species from the New River (Upper Kanawha Basin)

1. Freshwater communities are threatened by the conversion of natural landscapes for urban and agricultural purposes. Changes to land use may disrupt stream nutrient and geomorphological processes and reduce water quality, increase sedimentation, and decrease habitat heterogeneity eventually leading to species loss and decreases in ecosystem productivity. Endemic species are frequently at greater risk of habitat-mediated fragmentation and extirpation due to their constrained distributions.
2. The Kanawha darter (Etheostoma kanawhae) is an understudied fish endemic to the New River Drainage in North Carolina and Virginia, USA. To investigate the potential effect(s) of land-use change on Kanawha darters, naïve occupancy was modelled using instream habitat characteristics and upstream forest cover.
3. Generalized linear models revealed that instream habitat and forest cover are reliable predictors of Kanawha darter site occupancy. Specifically, models demonstrated that occupancy increased in reaches with reduced stream width, velocity, and bedrock substrate but higher concentrations of coarse woody material. Kanawha darter occupancy was also positively associated with the extent of forest cover in upstream catchments.
4. Although Kanawha darters are not currently considered imperilled, most populations occurred in isolated reaches separated by large sections of unoccupied habitat. Continuing ex-urban development in riparian zones is likely to be the primary threat to Kanawha darters and other endemic species in this catchment. Resource managers and stakeholders should preserve forest cover in headwaters and occupied tributaries and protect or restore riparian zones along the main-stem South and North Forks of the New River to preserve high-quality habitat and enhance connectivity among isolated Kanawha darter populations.
5. As human populations in montane regions continue to grow, there is a need to understand how land-use change affects endemic freshwater species. This study further supports the importance of retaining forest cover as an effective strategy for protecting and restoring populations of endemic fishes in high-gradient streams.

     

Spatial extent and consequences of black bass (Micropterus spp.) invasion in a Cape Floristic Region river basin

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Fish–habitat relationships and fish conservation in small coastal streams in southern Spain

• 1. Studies dealing with the fish fauna of coastal streams are scarce in the scientific literature, particularly those from Mediterranean climates. Owing to their small size, these systems suffer extreme seasonal fluctuations, following the typical Mediterranean flood–drought cycle and leading to a high risk of extinction to freshwater fish.
• 2. This work analyses fish distribution in 14 stream stretches belonging to eight basins in the northern sector of the Strait of Gibraltar (southern Spain). Fish–habitat relationships were studied through multivariate ordination techniques at two scales: basin and stretch.
• 3. A principal components analysis clearly discriminated larger and more sinuous basins from smaller and steeper ones. This ordination was related to the non‐migratory freshwater fish species richness and to the total number of fish species present in the middle reaches of each basin.
• 4. The main sources of variation in community composition and habitat characteristics in the different stretches were related to a clear upstream–downstream gradient, along which total species richness increased.
• 5. These small coastal basins are inhabited by two highly endangered species, Andalusian toothcarp (Aphanius baeticus) and Iberian chub (Squalius pyrenaicus), and have similar or higher overall freshwater species richness than larger adjacent basins. The near absences of flow regulation and introduced species make these streams one of the few types of Iberian aquatic system where unaltered fish–habitat relationships can be studied.

Copyright © 2005 John Wiley & Sons, Ltd.