Channel Border Research Articles

Le rôle de l'anthropisation des débits de l'Ariège dans son évolution morphologique

The impact of human intervention in the Ariège river flow on its morphological evolution. If one examines the present day flow of the Ariège River (central Pyrénées), one observes a mutation of its fluvial dynamics following the construction of several dams ; the sinuosity and the width of its channel have been reduced while its bed cuts deeper and its banks have become steeper. Vegetation has accentuated this evolution. By colonizing the minor bed, trees have closed the active band, thus favouring changes in the river. At the same time, analysis of hydrological readings over the past 100 years shows a weakening of high waters in the last decades. This diminution is largely due to the exploitation of dams. The reduction of hydrous constraints on channel borders has favoured the development of woody vegetation in the minor bed. We are faced with a process of de stabilization caused by human intervention in a fluvial system and in which vegetation plays a role both of catalyst and aggravating factor.

Diel Movement and Habitat Use by Paddlefish in Navigation Pool 8 of the Upper Mississippi River

Abstract We studied diel movement and habitat use by paddlefish Polyodon spathula implanted with radio transmitters in Navigation Pool 8 of the upper Mississippi River. We radio-tracked five paddlefish during three randomly chosen 24-h periods each month in May, Aug, and Oct 1995. Paddlefish were located by boat one to three times every 3 h during each 24-h period. At each location, geographic coordinates were determined with a global positioning system receiver using the Precise Positioning Service, and depth was measured with a depth sounder. Location coordinates were plotted with ARC/INFO software on a Geographic Information System land–water coverage. Movement distances were calculated as the linear distance between sequential locations. Radio-tagged paddlefish usually remained in a secondary channel that had low current velocity during all seasons, whereas main channel, main channel border, tailwater, and backwater habitats were seldom used. Paddlefish strongly selected areas that were deep; about 62...

Fish Assemblages of Natural and Artificial Habitats within the Channel Border of the Upper Mississippi River

Abstract The influence of specific types of habitat structure on fish assemblage structure, diversity and abundance in large rivers is largely unknown. This study determined whether fish assemblages differed among various artificial and natural habitats within the main channel border (shallow, nearshore areas) of the upper Mississippi River, and assessed whether different types of artificial structure influenced fish assemblage structure over long (>0.2 km) sections of shoreline habitat. Daytime electrofishing during August and October 1994 captured 31 different fish taxa from main channel border habitats in Pool 6 of the upper Mississippi River. Nine species of fish preferred specific types of nearshore habitat. Fish abundance and diversity measures differed little among habitat types, but significantly larger fish were present at locations with structure (wing dikes, woody snags) than at sites without (bare shore). Cluster analysis indicated that different fish assemblages occupied different habitat typ...

SAMPLING BENTHIC MACROINVERTEBRATES IN A LARGE FLOOD-PLAIN RIVER: CONSIDERATIONS OF STUDY DESIGN, SAMPLE SIZE, AND COST

Estimation of benthic macroinvertebrate populations over large spatial scales is difficult due to the high variability in abundance and the cost of sample processing and taxonomic analysis. To determine a cost-effective, statistically powerful sample design, we conducted an exploratory study of the spatial variation of benthic macroinvertebrates in a 37 km reach of the Upper Mississippi River. We sampled benthos at 36 sites within each of two strata, contiguous backwater and channel border. Three standard ponar (525 cm2) grab samples were obtained at each site ('Original Design'). Analysis of variance and sampling cost of strata-wide estimates for abundance of Oligochaeta, Chironomidae, and total invertebrates showed that only one ponar sample per site ('Reduced Design') yielded essentially the same abundance estimates as the Original Design, while reducing the overall cost by 63%. A posteriori statistical power analysis (α = 0.05, β = 0.20) on the Reduced Design estimated that at least 18 sites per stratum were needed to detect differences in mean abundance between contiguous backwater and channel border areas for Oligochaeta, Chironomidae, and total invertebrates. Statistical power was nearly identical for the three taxonomic groups. The abundances of several taxa of concern (e.g., Hexagenia mayflies and Musculium fingernail clams) were too spatially variable to estimate power with our method. Resampling simulations indicated that to achieve adequate sampling precision for Oligochaeta, at least 36 sample sites per stratum would be required, whereas a sampling precision of 0.2 would not be attained with any sample size for Hexagenia in channel border areas, or Chironomidae and Musculium in both strata given the variance structure of the original samples. Community-wide diversity indices (Brillouin and 1-Simpsons) increased as sample area per site increased. The backwater area had higher diversity than the channel border area. The number of sampling sites required to sample benthic macroinvertebrates during our sampling period depended on the study objective and ranged from 18 to more than 40 sites per stratum. No single sampling regime would efficiently and adequately sample all components of the macroinvertebrate community.

Foraging Characteristics of Larval Bluegill Sunfish and Larval Longear Sunfish in the Kanawha River, West Virginia

ABSTRACT We determined spatial and temporal foraging characteristics of larval bluegill sunfish (Lepomis macrochirus) and longear sunfish (Lepomis megalotis)in the upper Kanawha River, West Virginia during the summer of 1989. Stomach contents were examined among habitat types (i.e., main channel, main-channel border, and shoreline habitats) and depth (surface, middle, and bottom). Diet of larval bluegill sunfish was dominated by Chironomidae, temporally and spatially. Chironomidae dominated larval longear sunfish diet in main channel and main-channel border collections from all three depths. However, along the shoreline, larval longear sunfish diet was dominated by Cladocera.

The response of ostracod assemblages to recent pollution and sedimentary processes in the Huelva Estuary, SW Spain

By studying the ostracod assemblages in the Huelva Estuary, the impact of natural and human factors on the populations of these organisms can be determined. Three periods were defined in 12 cores collected along the estuary: (1) pre-industrial period (before 1966), with moderate pollution in some estuarine sectors because of prehistoric mining; (2) industrial period (1966–1985), with pollution increasing by wastes derived from industrial processes; and (3) post-industrial period (1991). No ostracods and live macrofauna were found in environments with extreme subaerial exposure (fluvial bars, meanders and salt marshes), even in pre-industrial sediments. During this period, the ostracod distribution was controled by the salinity tolerance in the main channel of the Odiel River, the euryhaline species being replaced by marine forms toward the estuary mouth. Acidic industrial wastes causes the disappearance of ostracod assemblages (mainly Loxoconcha elliptica) in this environment and the channel border. Fillings of some distributary channels have greatly affected the ostracod and macrofaunal assemblages in these zones, with a dramatic drop in the diversity and number of individuals. In April 1991, live ostracods were exclusively found in the Punta Umbría subsystem, a relatively protected environment because distance and salt-marsh barriers protect it from industrial effluents.

Habitat use and movements of shovelnose sturgeon in Pool 13 of the upper Mississippi River during extreme low flow conditions

We monitored habitat use and movement of 27 adult shovelnose sturgeon in Pool 13 of the upper Mississippi River, Iowa-Illinois, by radio-telemetry in April through August 1988. Our objective was to determine the response of this species to unusually low water conditions in the upper Mississippi River in 1988. Most (94%) telemetry contacts were made in 3 habitat types: main channel (50%), main channel border where wing dams were present (29%), and tailwaters of Lock and Dam 12 (15%). Habitat use in spring was affected by the extreme low flows. We often found tagged shovelnose sturgeon in the main channel and tailwaters during the spring period (11 March–20 May) where water velocities were highest. This was in contrast to other studies where shovelnose sturgeon did not occupy those areas during years with normal spring flows. Shovelnose sturgeon were typically found in areas with a sand bottom, mean water depth of 5.8 m, and mean bottom current velocity of 0.23 m sec-1. They occupied areas of swifter current but were not always found in the fastest current in their immediate vicinity. Tagged shovelnose sturgeon tended to remain in the upper, more riverine portion of the pool, and we observed no emigration from the study pool. Linear total range of movement from the tagging site ranged from 1.9 to 54.6 km during the study period.

Autumn use of woody snags by fishes in backwater and channel border habitats of a large river

Snags are important to fish communities in small rivers and streams, but their importance to fishes in large rivers has not been investigated. This study examined snag use by fishes during autumn in backwater and channel border habitats in the upper Mississippi River, and compared these to fish communities in reference sites without snags. Species assemblages differed significantly between backwater and channel border habitats, and between snag and reference sites within the channel border, likely responding to differences in substrate, depth, and current velocity. In both habitats, average fish biomass and abundance were higher (2 to 50 ×) at snag sites than at reference sites, but these differences were significant only for channel border biomass. Fish taxa richness differed between backwater and channel border habitats, but not between snag and reference sites. Most large piscivorous fishes (e.g., Micropterus spp., Stizostedion spp.), several insectivorous fishes (Lepomis macrochirus, Ambloplites rupestris, Minytrema melanops), and a few prey fishes (L. macrochirus, Notropis atherinoides) were significantly more abundant at snag sites than at reference sites, suggesting active selection of snags for foraging or protection. Snag quality, as assessed by a snag rating index, had a direct effect on attracting fish communities with greater biomass, especially within the channel border habitat. These results indicate that snags are important habitat for fish communities in both backwaters and channel border habitats of the upper Mississippi River.

Detecting an environmental impact of dredging on seagrass beds with a BACIR sampling design

The impact of maintenance dredging an access channel to a canal estate in Deception Bay, Australia, on the nearby seagrasses was monitored over 18 months with a Before/After, Control/Impact, Repeated measures (BACIR) sampling design. Three seagrasses were collected in the study area; Zostera capricorni Aschers., Halophila ovalis (R.Br.) Hook. f. and Halophila spinulosa (R.Br.) Aschers. All seagrasses were found less than 700 m offshore. The biomass of Z. capricorni, the numerically dominant seagrass, was significantly lower in the access channel border compared with the control area before dredging, which was attributed to direct or indirect effects associated with the channel. There was no significant effect of maintenance dredging statistically detected for Z. capricorni biomass in the access channel border even though seagrass was absent in the access channel 14 months after dredging. This was due to the high background variability of seagrass biomass in the control area. In contrast the biomass of H. ovalis declined at a significantly higher rate in the control area than in the access channel border but had also disappeared from the access channel border 14 months after dredging. Without a control we may have concluded that the disappearance of seagrass from the access channel border was due to the effects of dredging, whereas with a BACIR sampling program there remained a possibility that the decline in seagrass was due to larger scale changes in the bay.

Effects of Variable Annual Hydrology on a River Regulated for Navigation: Pool 26, Upper Mississippi River System

Abstract We investigated impacts of water level regulation for navigation on water quality, plant distribution and fish communities in Pool 26 of the upper Mississippi River during an extreme drought and following a return to typical flows. We also compared biological responses in three hydrologically distinct pool reaches. The third worst drought in 53 years occurred during 1989 and resulted in dam operations that created stable water surface elevations and low current velocities through the year. These conditions resulted in high water clarity that allowed development of submersed and floating-leaved aquatic plants in channel borders and backwaters; fish communities were dominated by centrarchids (lentic species). The drought was followed by two years of moderately high flow. Higher discharge resulted in lower water clarity and higher current velocity. When combined with drawdowns, such conditions limited submersed aquatic plant production and promoted mesic plant species. Centrarchid abundance declined, with the lower reach showing severe declines (from 95% of the catch in 1989 to 15% in 1991).

Distribución y ecologíade los foraminíferos y ostrácodos actuales del estuario mesomareal del río Guadiana (SO España)

In the Guadiana estuary, thirty-two recent samples were studied. The grain-size analysis differentiates between six distributions in the estuarine channel, four in the channel border and three in the salt marsh. The heavy metal concentration is low, with a maximum in the middle estuary, because of the floculation by water mixing. The three different estuarine zones (fluvial, middle and maríne) have been distinguished by the tidal-fluvial interaction and the microfaune (ostracoda and foraminifera). The biometry study of any species delimited the post-mortem transport of these organisms, mainly during the tidal reflux.

Improving Electrofishing Catch Consistency by Standardizing Power

Abstract The electrical output of electrofishing equipment is commonly standardized by using either constant voltage or constant amperage, However, simplified circuit and wave theories of electricity suggest that standardization of power (wattage) available for transfer from water to fish may be critical for effective standardization of electrofishing. Electrofishing with standardized power ensures that constant power is transferable to fish regardless of water conditions. The in situ performance of standardized power output is poorly known. We used data collected by the interagency Long Term Resource Monitoring Program (LTRMP) in the upper Mississippi River system to assess the effectiveness of standardizing power output. The data consisted of 278 electrofishing collections, comprising 9,282 fishes in eight species groups, obtained during 1990 from main channel border, backwater, and tailwater aquatic areas in four reaches of the upper Mississippi River and one reach of the Illinois River. Variation in p...

Ichthyoplankton abundance and variance in a large river system concerns for long‐term monitoring

AbstractSystem‐wide spatial patterns of ichthyoplankton abundance and variability were assessed in the upper Mississippi and lower Illinois rivers to address the experimental design and statistical confidence in density estimates. Ichthyoplankton was sampled from June to August 1989 in primary milieus (vegetated and non‐vegated backwaters and impounded areas, main channels and main channel borders) in three navigation pools (8, 13 and 26) of the upper Mississippi River and in a downstream reach of the Illinois River. Ichthyoplankton densities varied among stations of similar aquatic landscapes (milieus) more than among subsamples within a station. An analysis of sampling effort indicated that the collection of single samples at many stations in a given milieu type is statistically and economically preferable to the collection of multiple subsamples at fewer stations. Cluster analyses also revealed that stations only generally grouped by their preassigned milieu types. Pilot studies such as this can define station groupings and sources of variation beyond an a priori habitat classification. Thus the minimum intensity of sampling required to achieve a desired statistical confidence can be identified before implementing monitoring efforts.

Longitudinal Variation in Zooplankton Populations in Pool 19, Upper Mississippi River

ABSTRACT Zooplankton samples were collected in main channel and adjacent channel border habitat at eight transects in navigation Pool 19, Mississippi River. Rotifers dominated the system with the most abundant organism being Brachionus calyciflorus. Zooplankton densities were statistically higher at both the upper and lower ends of the pool. The lower end of the pool was lacustrine in nature, thus supporting higher zooplankton densities. These high densities are transferred to the upper part of the succeeding pool Such a sequence of populations may be typical of pool systems that result from navigation structures such as those on the upper Mississippi River.

The Development of an Aquatic Vegetation Community in Pool 19, Upper Mississippi River

ABSTRACT Sediments have accumulated in the main channel border area upstream of Lock and Dam 19 on the upper Mississippi River to the extent that water depth has decreased from 11.5 m to less than 2 m. Beginning in the 1950's, aquatic vegetation became established in the lower 3 km of the pool; community development through 1983 was primarily submersed vegetation (Potamogeton spp. and Vallisneria americana). Aerial photographs were used to document the expansion of plant beds from 19 ha (1956) to 80 ha (1978). In 1984, Nelumbo lutea invaded the plant bed and by 1987 occupied 26 of the 110 vegetated ha. Standing crop estimates showed that where N. lutea was present, standing crop biomass of V. americana was reduced by an average of 56%. Using existing conceptual models and estimated sedimentation rates, we predict that the study area will become a naturally leveed floodplain dominated by immersed vegetation. Species composition of the community will depend on elevation, nutrient status of the soils, and the degree of inundation, exposure, and disturbance.

Physical Factors and Their Influence on the Mussel Fauna of a Main Channel Border Habitat of the Upper Mississippi River

The habitats of mussel species in a portion of the main stem of Navigation Pool 10 of the upper Mississippi River were examined. Population composition, abundance, and sediment and current preferences were measured at 186 sites in the East Channel of the pool. Although total mussel abundance varied significantly as a function of sediment and current (p ≤ 0.05), abundance could be predicted in only 44% of sites by discriminant analysis models. Accurate prediction of abundance for most species also was poor. Species showed little discrimination in choosing main channel habitats, but could be broadly classified into species preferring fine to medium-fine sands (e.g., Truncilla truncata and Potamilus alatus) or coarser sands (e.g., Lampsilis cardium and Truncilla donaciformis). The endangered Lampsilis higginsi was found in a broad range of habitats similar to those occupied by many of the more common species, suggesting factors other than loss of adult habitat for the rarity of this species.

Summer bacterial populations in Mississippi River Pool 19: implications for secondary production

Bacterial populations were sampled at 37 sites in Mississippi River Pool 19. Bacterial biomass was calculated from direct epifluorescent cell counts. Bacterial production was estimated by incubating cells in situ in predator-free water inside membrane chambers and the frequency of dividing cells. Bacterial biomass in the water column ranged from 0.05 to 1.13 mg C l -1, biomass in the vegetated areas of the pool was significantly higher than that in other habitats (P < 0.05, ANOVA). Biomass in sediments (to a depth of 10 cm) ranged from 24 to 1,073 mg C m-2, biomass in muddy sediments was significantly higher (P < 0.05) than that in sandy sediments. Biomass on the submersed surfaces of hydrophytes was 0.06–4.90 mg bacterial C g-1 dry weight of plant material. The vegetated habitat (water column plus vegetation) contained approximately 45 times the concentration of bacterial carbon found in nonvegetated main channel border areas and more than 100 times the concentration in the main river channel. Bacterial production rates in the water column of a vegetated section of the pool ranged from 0.03 to 3.28 g C m -3 s d -1 ; production (m -3) in a vegetation bed was 5.5 times that in the adjacent nonvegetated channel border areas and approximately 50 times that in the main channel. Aquatic macrophytes and associated microorganisms may be capable of providing significant inputs of carbon to secondary consumers in the pool during the summer low flow.

Fish Species Associated with Revetted and Natural Main Channel Border Habitats in Pool 24 of the Upper Mississippi River

Abstract Two revetted and two natural main channel border sites within Pool 24 of the upper Mississippi River were electrofished over a 3-year period to determine the fish species and diversity of species associated with the two habitat types. Over the sampling period, 6,440 fish were collected of which 70% were taken from the revetted sites. One revetted site had larger diameter stones (≳ 2 feet) than the other; 40% of the fish collected were taken at the large-stone site. There were no differences in species numbers along the revetted and natural banks; each habitat produced 33 species. Thirty-eight species were taken collectively from all sites. Gizzard shad (Dorosoma cepedianum) and common carp (Cyprinus carpio) were the two most numerous species collected along both the revetted and natural shorelines; they accounted for 65% of the total number of fish caught. Catch per unit effort (C/F) for the four sites varied from 138 to 20 fish/h. The large-stone revetment area had a mean C/F of 98; C/F were 75,...

Fate of Navigation Pool on Mississippi River

Humans have altered streams and rivers for economic, commercial, and recreational uses. Low flow depths in navigable rivers have been increased by the construction of locks and dams to facilitate the movement of river traffic such as barge tows. Lock and Dam on Pool 19 on the Mississippi River near Keokuk, Iowa, is the oldest and one of the two highest dams on the Mississippi River. The high storage-capacity-to-inflow ratio causes a high trap efficiency for this pool. The pool is going through a successional change and ultimately will attain a dynamic volumetric equilibrium with an extensive formation of islands, shallow channel border areas, and plant beds. Interactions between the river and its tributaries have also changed, and these confluences are now more like estuaries than river junctions. The deltas, islands, and shallow wetlands near the confluences are the end products of these changing interactions. The dam has changed the Des Moines Rapids into a biologically productive pool with extensive beds of aquatic macrophytes and burrowing macroinvertebrates, which attract migratory waterfowl and fish.

White Catfish Growth and Life History in the Hudson River Estuary, New York

ABSTRACT The white catfish (Ictalurus catus) was studied in the upper Hudson River Estuary to describe its growth and habits at the northern edge of its range. Ages from pectoral spine examination showed annuli formed before June and the fish reach size of maturity after age three. Length at age was back calculated with a correction factor and by direct proportion; differences averaged only 4 mm and the correction method was favored. Spawning apparently occurred in June and July in sandy shoals and rock piles. Preferred habitats for catfish in other seasons were channel border or shoal and vegetated backwaters. Tag returns suggested a large population and indicated seasonal movements typical of this species.