The impact of river regulation on the lotic macroinvertebrate communities of the lower rhǒne,France

Channelization and the construction of 12 dams on the Lower Rhǒne during the last 30 years increased the morphological and biological effects of 19th century embanking along the river. These trends were demonstrated on the main channel, i.e. the central axis of the alluvial floodplain, by the synchronic study of the benthic macrofauna of six lowhead hydroelectric impoundments. The variability of the most significant taxa was investigated by an ANOVA, and the data-samples matrix was processed with a Principal Components Analysis in order to analyse the communities organization and their significance. The benthic macroinvertebrate communities of the channel include some lentic potamic species topographically related with this kind of river (metapotamon), as well as eurytopic and pollution-tolerant species. Thus, the Lower Rhǒne has become a slow potamic river, in the same way as other large mid-European rivers. Flow velocity appears to be the most important structural factor in a large regulated river. The homogeneity of the macroinvertebrate communities and the absence of longitudinal typology show that, in a very intensely regulated river, the River Continuum Concept is too theoretical, and the disturbing effects of dams on longitudinal changes and species response to regulation must be taken into account.     

MACROINVERTEBRATE COMMUNITIES OF THE DOUBS RIVER PRIOR TO COMPLETION OF THE RHINE–RHONE CONNECTION

The Rhine–Rhône connection project concerns the part of the Doubs River between Montbéliard and Dôle (France), i.e. downstream from the confluence of the Allan River. In order to update our knowledge of the benthic macroinvertebrate communities of the Doubs River, three types of aquatic environments of this hydrosystem were sampled (main channel, backwaters and the Freycinet canal). Hydraulic characteristics are the most explanatory environment variables of lotic macroinvertebrate distribution of the Doubs hydrosystem. The aquatic fauna of the Doubs River is varied due to the diversity of biotopes, microhabitats and current velocities. The lotic aspect is well defined. Rheophilic taxa are present in the main stream in riffle areas or located downstream from weirs where the current velocity is rapid (>75 cm s⁻¹). The physics of flow (‘stream hydraulics’) create the richness of habitats and thereby the biological diversity. Backwaters have a relatively high richness, similar to that of stations in the main stream located in the same sector. Conservation management must be oriented towards the present ecological situation of the Doubs River, i.e. that of a lotic ecosystem with active connections with its backwaters. The primary goal from a conservation perspective must be the maintenance and the improvement of areas highly sensitive to disturbances.     

Fish and Macroinvertebrate Communities in Tributary Streams of Eastern Lake Erie with and without Round Gobies (Neogobius melanostomus, Pallas 1814)

Round gobies have had significant impacts on benthic fish and invertebrate communities in nearshore habitats of the Great Lakes. As round gobies have become more abundant in lake habitats, there has been an expansion of their populations into tributary streams and rivers. We compared stream invertebrate and fish communities in New York tributaries to Lake Erie with round gobies present and absent. Four of six benthic invertebrate metrics differed between streams with and without round gobies. Streams with round gobies present had reduced Shannon diversity, EPT richness, and EPT/chironomid ratios, and increased macroinvertebrate density relative to streams without round gobies, but there was no difference in non-Diptera density, or total taxa richness. None of the four fish metrics examined differed between streams with and without round gobies. However, darters occurred in all streams lacking round gobies, but did not occur in any streams with round gobies. Comparisons with historical fish and macroinvertebrate distributional data support our suspicion of goby-induced community changes. In these New York streams, round gobies seem to have had significant impacts on invertebrate communities via their consumptive behavior, whereas the impacts on fish communities are less evident. If round gobies continue to expand their distribution inland, the resultant alterations in macroinvertebrate communities may impact the suitability of tributary streams as spawning and nursery habitat for several sport fish species and for energy dynamics in tributary streams.     

水事活动对洪湖鱼类资源的生态影响

长江中游两岸绝大多数湖泊自20世纪50年代以来因水利工程建设，先后失去与长江的天然联系而产生一系列的生态问题。以洪湖为例开展江湖阻隔对单个湖泊鱼类资源所产生的生态影响进行研究，结果表明：江湖阻隔导致湖泊渔业生产经营方式改变，野生渔业的产量和在渔业经济结构中的比重不断降低；阻隔后湖泊鱼类品种由20世纪50年代的不下100种下降到现在的49种，其中，天然捕捞渔获物中洄游性和流水型鱼类比重由20世纪50年代初的60％降到现在几近为0，大型经济鱼类减少，鱼类多样性指数下降。因此，江湖阻隔对湖泊渔业具有明显影响。     

Influence of river plumes on the distribution and composition of nearshore Lake Michigan fishes

River plumes form in coastal areas where tributaries mix with their receiving waters. Plume waters are enriched with terrestrial-derived nutrients from their watersheds creating hotspots of biological productivity. The biological importance of plumes scales with the size and persistence of the plume; therefore, large, persistent plumes are more important than small, transient plumes. To date, most studies of plumes have focused on assimilation of terrestrial-derived energy by aquatic species or lower-level food web effects, primarily in marine systems. Few studies have described fish communities near plume habitats and compared them to non-plume areas, especially for the numerous small plumes in the Laurentian Great Lakes. Here we demonstrate that small plumes in the main basin of Lake Michigan enhance local primary productivity and influence distribution and abundance of nearshore Great Lakes fishes. We found that plume fish communities were relatively depauperate and did not support higher biological diversity of fishes compared to non-plume areas. However, individual species including rainbow smelt Osmerus mordax, spottail shiner Notropis hudsonius, and white sucker Catostomus commersonii were more abundant around plumes. Our results demonstrate that small plumes in the main basin of Lake Michigan support highly localized hotspots of biological productivity and fish abundance, primarily within 2?km of river mouths.     

Temporal shifts in the biodiversity of nearshore small fishes in Lake Simcoe

Nearshore small fish species represent a large proportion of fish biodiversity in Lake Simcoe, a large inland lake in southern Ontario, Canada. Over the past 30 years, Lake Simcoe has experienced several changes to its aquatic habitat, benthic invertebrate communities and predatory fish populations. This study compared samples of the nearshore small fish community in three geographic areas of Lake Simcoe. Fish community data were grouped into two time periods: a contemporary period (2007–2009) and a historical period (1982–1995). The fish community was compared across time periods for each area to assess if observed ecological changes had an impact on the small fish community. Species richness significantly declined between time periods in two areas (Cook's Bay and the southeast shoreline), the number of individuals captured declined between time periods in one area of the lake (Kempenfelt Bay) and Simpson's diversity index declined between time periods in one area of the lake (southeast shoreline). There were no significant differences in the Shannon–Weiner evenness index between time periods in any of the study areas. Additional analyses of intra- and inter-annual variation in fish sampling results generally supported the findings that shifts in the fish community occurred between time periods. Overall, this study suggests that the nearshore small fish biodiversity of Lake Simcoe has shifted over time but these shifts are not clearly related to recent increases in water clarity, macrophyte growth and nearshore benthic invertebrate densities.     

PATTERNS OF ICHTHYOFAUNAL DISTRIBUTION AND CONNECTIVITY IN NAVIGABLE AND FREE‐FLOWING REACHES OF A MAJOR RIVER SYSTEM: THE ALLEGHENY RIVER IN PENNSYLVANIA

Connectivity throughout large riverine networks is often compromised by lock and dam (L/D) structures designed to facilitate year‐round navigation. The resultant interruption of flow inhibits free passage of aquatic biota potentially isolating mainstem and tributary communities. Our objectives were (i) to evaluate the impact of a series of navigational L/D structures on two targeted fish assemblages (TFAs): large‐bodied (>250 mm total length) pelagic and benthic (darter) communities and (ii) to examine patterns of tributary and mainstem connectivity. We systematically captured fishes utilizing gillnets, benthic trawls and backpack electrofishers from an impounded and a free‐flowing reach extending over 203 km of the Allegheny River in Pennsylvania. Species richness among the large‐bodied targeted fish assemblage was distributed somewhat evenly throughout each pool, peaking near dams and in an undredged pool. Depauperate darter assemblages of low species richness characterized most of the navigable reach with diversity and abundance concentrated in L/D tailrace areas. By contrast, darter communities inhabiting the free‐flowing reach were more diverse, abundant and evenly distributed, indicating the influence of uninterrupted connectivity. Community similarity at mainstem/tributary junctions increased with increasing tributary size with 50% of the mainstem species complement also inhabiting the largest tributary. This study underscores the importance of dams as barriers to ichthyofaunal connectivity, particularly to those benthic fishes which are relatively immobile and habitat specific, and the importance of mainstem/tributary junctions as avenues of riverine connectivity. Copyright © 2013 John Wiley & Sons, Ltd.     

Ecological monitoring of fish assemblages downstream of a hydroelectric dam in French Guiana (South America)

Dam impacts on the downstream section of dammed rivers are known to be important for fish because of changes in the physical and chemical river characteristics. However, the available data seem to be insufficient to draw general conclusions regarding the transformation of fish communities. A hydroelectric dam was built on the Sinnamary River in French Guiana and closed in January 1994. From December 1991 to December 1996 fish collections were made from the downstream section. The results show a rapid decrease in fish abundance in the middle downstream course immediately after dam closure. This low abundance was observed until the end of the filling phase, when the flow was maintained at a minimum level. Afterwards, abundance returned to a level comparable with that prior to dam closure. Fish collection in different zones showed that the decrease in abundance was probably due to the escape of fish to shelter areas. Another marked effect was the reduction of sample diversity due to a decrease in species richness, as well as in the regularity of the distribution of species’ relative abundance. Examination of biological traits of species suggests that under these conditions feeding strategies could have been the most important factor affecting the abundance of populations. Copyright © 1999 John Wiley & Sons, Ltd.     

Condition of resident fish communities in the Eighteenmile Creek Area of Concern,New York

The lower 3.5 km of Eighteenmile Creek, a tributary to Lake Ontario in New York, was designated as an Area of Concern (AOC) in 1985 under the Great Lakes Water Quality Agreement due to extensive contamination of bed sediments by polychlorinated biphenyls (PCBs) and other toxicants. Five beneficial use impairments (BUIs) have been identified in this AOC, including degraded fish and wildlife populations. We surveyed fish communities in the Eighteenmile Creek AOC and in a comparable section of a nearby reference stream (Oak Orchard Creek) during June 2019 to infer whether legacy contaminants are currently impairing fish communities in the AOC to an extent that they differ from the regional reference condition. Estimates of community abundance, biomass, diversity, and fish condition from each system were compared using a noninferiority testing framework. Biomass, diversity, and fish condition in the Eighteenmile Creek AOC were similar or superior to that in Oak Orchard Creek, while abundance was 20% lower in the AOC. These findings and those of a 2007 sampling effort suggest that fish communities in the Eighteenmile Creek AOC are not impaired despite recent studies indicating that PCBs are bioaccumulating in fish tissues at 1–2 orders of magnitude above background levels. Future assessments in the Eighteenmile Creek AOC might focus on the condition of benthic macroinvertebrate communities and potential toxicity of local contaminants to piscivorous wildlife in order to fully address the remaining aspects of the fish and wildlife populations beneficial use impairment.     

Nearshore Community Characteristics Related to Shoreline Properties in the Great Lakes

Successful protection and restoration of Great Lakes nearshore ecosystems will likely rely on management of terrestrial resources along Great Lakes shorelines. However, relationships between biological communities and changing shoreline environmental properties are poorly understood. We sought to begin understanding the potential roles of shoreline geomorphological and land cover properties in structuring nearshore biological communities in the Laurentian Great Lakes. Despite high variability in densities (benthic macroinvertebrates and zooplankton) and catch per unit effort (CPUE, shallow water and nearshore fish) within and among lake areas, several biological community patterns emerged to suggest that nearshore aquatic communities respond to shoreline features via the influences of these features on nearshore substrate composition and stability. Benthic macroinvertebrate densities were not different between shoreline types, although they were generally lower at nearshore sites with less stable substrates. Shallow water fish CPUE and zooplankton densities were generally lower for nearshore areas adjacent to developed mid-bluff shorelines and sites characterized by less stable substrates. Larger fish CPUE appeared to be unresponsive to local shoreline and substrate properties of nearshore zones. The emergence of these patterns despite significant ecological differences among lake areas (e.g., productivity, community composition, etc.) suggests that shoreline development may have comparable influences on nearshore ecosystems throughout the Great Lakes, providing a terrestrialbased indicator of relative nearshore biological and ecological integrity.     

Towards improving an Area of Concern: Main-channel habitat rehabilitation priorities for the Maumee River

The Maumee River watershed in the Laurentian Great Lakes Basin has been impacted by decades of pollution and habitat modification due to human settlement and development. As such, the lower 35 km of the Maumee River and several smaller adjacent watersheds comprising over 2000 km² were designated the Maumee Area of Concern (AOC) under the revised Great Lakes Water Quality Agreement in 1987. As part of pre-rehabilitation assessments in the Maumee AOC, we assessed fish and invertebrate communities in river km 24–11 of the Maumee River to identify: 1) areas that exhibit the highest biodiversity, 2) habitat characteristics associated with high biodiversity areas, 3) areas in need of protection from further degradation, and 4) areas that could feasibly be rehabilitated to increase biodiversity. Based on benthic trawl data, shallow water habitats surrounding large island complexes had the highest fish diversity and catch per unit effort (CPUE). Electrofishing displayed similar fish diversity and CPUE patterns across habitat types early in the study but yielded no discernable fish diversity or CPUE patterns towards the end of our study. Although highly variable among study sites, macroinvertebrate density was greatest in shallow water habitats <2.5 m and around large island complexes. Our results provide valuable baseline data that could act as a foundation for developing rehabilitation strategies in the lower Maumee River and for assessing the effectiveness of future aquatic habitat rehabilitation projects. In addition to increasing in-channel habitat, watershed-scale improvements of water quality might be necessary to ensure rehabilitation strategies are successful.     

Changes in fish communities of the Shoalhaven River 20 years after construction of Tallowa Dam,Australia

This study was undertaken as part of a long‐term investigation of the ability of high‐level fishways to rehabilitate fish communities upstream of high dams. Effects of Tallowa Dam on fish of the Shoalhaven River system were studied by comparing species abundances, population size‐structures and the structure of fish communities above and below the dam. Fish were sampled twice yearly for two years at 12 sites throughout the catchment. Species richness was greater downstream of the dam, with 21 species, compared to 16 species upstream of the dam. Ten diadromous species are believed to be extinct above the dam because of obstructed fish passage. Another four migratory species capable of climbing the wall have reduced abundances upstream. Accumulations of fish, particularly juveniles, directly below the dam were evident for nine species. Fish communities upstream and downstream of the dam differed significantly, identifying the dam as a significant discontinuity in the available fish habitats within the system. Historical evidence suggests that before the dam was built, fish communities from the tidal limit to at least 130 m elevation were largely continuous. This study has demonstrated that Tallowa Dam is a major barrier to fish migration and has had adverse effects on the biodiversity of the system. The creation of Lake Yarrunga by Tallowa Dam has resulted in distinctive fish communities in riverine and lacustrine habitats. Populations of five species that occur both upstream and downstream of the dam have developed differences in their size structures. The fish community downstream of the dam also differs from its historical condition because of the virtual disappearance of Australian grayling (Prototroctes maraena) and the establishment of non‐native species. A high‐level fishway is now being designed for the dam to restore fish passage. Data from this study will serve as a baseline against which to assess the effectiveness of the fishway in rehabilitating fish communities of the river system. Copyright © 2002 John Wiley & Sons, Ltd.     

The benthic community of the Laurentian Great Lakes: Analysis of spatial gradients and temporal trends from 1998 to 2014

We used the results of seventeen years of Great Lakes benthic monitoring conducted by the U.S. EPA's Great Lakes National Program Office to describe the spatial and temporal patterns of benthic communities, assess their status, trends, and main drivers, and to infer the potential impact of these community changes on ecosystem functioning. Benthic abundance and diversity were higher at shallow (<70?m in depth) stations with chlorophyll concentrations above 3?μg/L than at deeper sites (<1?μg/L). We infer that lake productivity, measured by chlorophyll was likely the major driver of benthic abundance and diversity across lakes. Consequently, benthic diversity and abundance were the highest in the most productive Lake Erie, followed by lakes Ontario, Michigan, Huron, and Superior. Multivariate analysis distinguished three major communities shared among lakes (littoral, sublittoral, and profundal) that differed in species composition and abundance, functional group diversity, and tolerance to organic pollution. Analysis of temporal trends revealed that the largest changes occurred in profundal communities, apparent in significant shifts in dominant taxa across all lakes except Lake Superior. In lakes Michigan, Huron, and Ontario, the former dominant Diporeia was replaced with Dreissena and Oligochaeta. Profundal species, with the exception of dreissenids, became less abundant, and their depth distribution has shifted. In contrast, density and diversity of native littoral and sublittoral communities increased. The invasion of dreissenids was among the most important drivers of changes in benthic communities. Continued monitoring is critical for tracking unprecedented changes occurring in the Great Lakes ecosystem.     

Integrating remote sensing and species distribution modelling to predict benthic communities in a Great Lakes connecting channel

Species distribution models have become widespread in benthic ecology; however, they have mostly been applied to marine and lentic systems. In this study, we applied a maximum entropy model by using remote sensing‐derived environmental variables to predict the distribution of 4 major benthic communities dominated by Tubificidae, Naididae, Echinogammarus ischnus, and Dreissena spp, respectively, in the lower Niagara River, NY, USA. The model showed very good accuracy for benthic communities with a narrow distribution range (Tubificidae and Naididae) indicated by the area under the curve test values of 0.906 and 0.987, respectively. In contrast, the model showed poor performance for E. ischnus and Dreissena indicated by the low area under the curve values of 0.615 and 0.618, respectively. Both communities are known to cope with a wide variety of environmental factors and habitats, making their accurate predictions difficult using presence‐only data. Our results can further be used to locate important feeding grounds for higher trophic levels, to assess the potential spread of exotic species, and to identify areas for restoration.     

Grundlegende Erkenntnisse im Rahmen des Pilotprojekt Bad Deutsch-Altenburg – Die Bedeutung der Stromsohle und Uferzonen für ökologische Prozesse und Artengemeinschaften an einem stark regulierten Fluss,der Donau

To ensure a long-term ecological stability, rivers need areas that are available at different discharge situations as highly productive habitats which are connected with the river. These retention areas or biologically active zones are important for the riverine communities as refuge (e.g. benthic macroinvertebrates and fish) or the development of benthic algae communities as basis for the riverine food web as well as retention zones to perform various ecosystem services (e.g. nutrient retention). Especially during low water level situations, the river shorelines and the river bed itself are of significant importance, but highly degraded in intensely regulated river systems such as the Danube River. A basic understanding of the processes and functional correlations is required to avoid negative consequences of engineering measures applied and to improve the ecological conditions. In the framework of the pilot project Bad Deutsch-Altenburg in the Danube River east of Vienna not only monitoring the implementation of engineering measures is required, but also scientific knowledge gained about basic ecological relationships and potential responses of riverine communities. This article presents results of several years of investigations on the distribution and development of three organism groups (benthic algae, benthic macroinvertebrates and fish) along different riparian structures and in the river bed of the Danube River.     

The downstream impacts of the burgomillodo reservoir,Spain

The Burgomillodo Dam, located in the middle Rio Duraton (north Spain, Duero Basin), has created a small eutrophic reservoir with a capacity of 15 × 10⁶ m ³ and a maximum depth of 40m. Burgomillodo Reservoir is solely used for producing hydroelectric power. The regulated flow pattern of hypolimnial waters is characterized by higher daytime flows than those by night, with low flows at weekends all the year round. The environmental impact generated by this hydropower scheme on the river downstream was assessed by comparing physiochemical characteristics and aquatic communities of an upstream site (reference station) with those of three downstream stations, which were located 0–2, 2–5, and 7–6 km below the dam. Water temperature, pH and dissolved oxygen were significantly lower downstream from the reservoir. Hardness, alkalinity, suspended inorganic matter, and conductivity had reduced annual variability below the dam. Photosynthetic activity was directly involved in the recovery of dissolved oxygen and pH values. Species richness and abundance of macrophytes increased just below the dam. Macrobenthic and fish communities were composed of higher numbers of potamic species. Number of taxa, density, biomass, and diversity were higher at the reference site, recovering their values as the distance below the reservoir increased. Macrobenthic trophic structure was changed by an increase in predators and filter feeders and a decrease in shredders. Environmental impact values for the macrobenthic community living just below the dam were higher than those for the fish community. It is concluded that the main physiochemical factors involved in environmental impacts were dissolved oxygen deficit and short-term flow fluctuations for the macrobenthic community, and oxygen deficit for the fish fauna. Benthic macroinvertebrates appear to be the best aquatic organisms for detecting changes and for reflecting the spatial recovery of environmental conditions.     

Effects of habitat and fishing on fish assemblages in a tropical reservoir: Lake Kariba,Zimbabwe

This study investigated the effects of habitat and fishing on fish communities along inshore areas of the Sanyati Basin, Lake Kariba. A one‐year experimental gillnet survey was carried out in 2007 from eight sampling sites located in two different habitats (river mouths and sheltered bays), and in areas open or closed to fishing. A total of 16 species were captured, although the numbers caught at each site varied widely, with only four species recorded at each of the eight sampling sites. The numbers of fish were higher in the fished areas, mainly because of large numbers of Synodontis zambezensis, although the differences were not significant. In contrast, there were significant differences in the abundance of all species between habitats, with the exception of Cyphomyrus discorhynchus and Marcusenius macrolepidotus. There were no significant differences in the diversity of fish in these areas, although mean diversity and evenness were slightly higher in unfished areas and in sheltered bays. Overall, 90% of the fish specimens caught were within a 10–25 cm size range, although there were no systematic differences in the mean length in relation to fishing. In contrast, most fish were generally larger in river mouth areas than in sheltered bays. These data suggest that fishing had little effect on fish communities. This is in contrast to general habitat, which had a significant effect, a finding consistent with earlier studies showing that vegetation, in particular, had a significant effect on fish stocks.     

Patterns of species richness and introduced species in native freshwater fish faunas of a Mediterranean‐type basin: the Guadiana River (southwest Iberian Peninsula)

In this study, we analysed the factors affecting species richness and introduced species component patterns in native fish faunas of 30 streams of the Middle Basin of the Guadiana River. From a principal component analysis and a stepwise multiple regression analysis performed on a data matrix composed of ten hydrological and biotic variables, we showed that: (1) fish species richness increased with stream length and watershed area, (2) the number of native species in a stream declined as channelizations and river regulation (constructions of dams) are higher, whereas introduced species increased in the same way, (3) the two main negative factors affecting native ichthyofaunas affected dissimilar ecological areas: channelizations, which depend on land‐use intensity of floodplain, mainly occurred in lower reaches of streams, but construction of dams mainly took place in upper sections of rivers, (4) the length of the remaining well‐preserved reaches in a stream appeared to be the only factor accurately predicting native fish species richness, and (5) native fish faunas of small isolated streams are more vulnerable to habitat alteration than those of large streams. Both isolation and fragmentation of populations were recorded, so the conservation status of native and highly endemic fish fauna of the study area is extreme. Protection of the few still extant, well‐preserved small streams and upper reaches, habitat restoration of channeled areas, and inclusion of the need for native fish fauna conservation in long‐term public planning of water use become a priority. Fish communities appear to be a sensitive indicator of biological monitoring to assess environmental degradation. Copyright © 2001 John Wiley & Sons, Ltd.     

Diet of Invasive Adult White Perch (Morone americana) and their Effects on the Zooplankton Community in Missisquoi Bay,Lake Champlain

White perch (Morone americana) became established in Missisquoi Bay, Lake Champlain in the mid 1990s. Since that time, cyanobacteria blooms have become common in summer. Although introduced planktivorous fish often impact plankton communities through a reduction in Daphnia density, such effects can be difficult to predict in an opportunistic species such as white perch. In this study, we examined the extent of zooplanktivory exhibited by adult white perch in Missisquoi Bay. Adult white perch were collected from Missisquoi Bay on ten dates in spring and summer of 2005. White perch diet consisted of large numbers of Daphnia on dates when Daphnia densities exceeded 20 individuals/L and when Daphnia comprised more than 50% of the zooplankton assemblage. When Daphnia densities were below these threshold values, adult white perch diet consisted predominantly of benthic prey. Our results show that white perch feed on large numbers of Daphnia in Missisquoi Bay and select Daphnia over other zooplankton taxa when they are abundant. It is likely that adult white perch grazing in Missisquoi Bay has contributed to a reduction in Daphnia density which in turn may be contributing to summertime cyanobacteria dominance in this bay.