Upstream and downstream responses of fish assemblages to an eastern Amazonian hydroelectric dam

相似文献   

Temporal patterns in a fish assemblage of a semiarid mangrove zone in Madagascar

Gillnet sampling was conducted for a year in a tropical mangrove creek (SW Madagascar), characterized by a limited freshwater influence, a high turbidity and a tidal range up to 3 m. Sixty species of juvenile fishes were caught, 44 species being of commercial interest. Catches were dominated by Gerreidae (27% of total abundance), Teraponidae (16%), Carangidae (13%) and Sparidae (12%). The temporary resident fishes in the mangrove zone represented 50% of the species and 97% of the total abundance, the other species being rare (less than five individuals). The species richness, abundance and biomass per netting were low in the middle of the cool season (July-August). Monthly changes in the fish assemblage were particularly complex, with three species groups displaying a clear seasonal pattern, some species succeeding one another in a rather unstructured way, and three species abundant throughout the year. There was no clear structuring effect of temperature, salinity and turbidity on the fish assemblage. However, tidal, lunar and diel effects on the composition of the fish assemblage were evident. The species overlap between the Sarodrano mangrove fauna and the adjacent coral reef fauna is particularly weak with six species in common and shows that the mangrove plays only a very limited nursery role for coral reef species.     

Impact of Beaver Dams on Abundance and Distribution of Anadromous Salmonids in Two Lowland Streams in Lithuania

European beaver dams impeded movements of anadromous salmonids as it was established by fishing survey, fish tagging and redd counts in two lowland streams in Lithuania. Significant differences in abundancies of other litophilic fish species and evenness of representation by species in the community were detected upstream and downstream of the beaver dams. Sea trout parr marked with RFID tags passed through several successive beaver dams in upstream direction, but no tagged fish were detected above the uppermost dam. Increase in abundances of salmonid parr in the stream between the beaver dams and decrease below the dams were recorded in November, at the time of spawning of Atlantic salmon and sea trout, but no significant changes were detected in the sections upstream of the dams. After construction of several additional beaver dams in the downstream sections of the studied streams, abundance of Atlantic salmon parr downstream of the dams decreased considerably in comparison with that estimated before construction.     

Contrasted impacts of climate change on stream fish assemblages along an environmental gradient

Aim To investigate the potential impacts of climate change on stream fish assemblages in terms of species and biological trait diversity, composition and similarity. Location One‐thousand one‐hundred and ten stream sections in France. Methods We predicted the future potential distribution of 35 common stream fish species facing changes in temperature and precipitation regime. Seven different species distribution models were applied and a consensus forecast was produced to limit uncertainty between single‐models. The potential impacts of climate change on fish assemblages were assessed using both species and biological trait approaches. We then addressed the spatial distribution of potential impacts along the upstream–downstream gradient. Results Overall, climate change was predicted to result in an increase in species and trait diversity. Species and trait composition of the fish assemblages were also projected to be highly modified. Changes in assemblages’ diversity and composition differed strongly along the upstream–downstream gradient, with upstream and midstream assemblages more modified than downstream assemblages. We also predicted a global increase in species and trait similarity between pairwise assemblages indicating a future species and trait homogenization of fish assemblages. Nevertheless, we found that upstream assemblages would differentiate, whereas midstream and downstream assemblages would homogenize. Our results suggested that colonization could be the main driver of the predicted homogenization, while local extinctions could result in assemblage differentiation. Main conclusions This study demonstrated that climate change could lead to contrasted impacts on fish assemblage structure and diversity depending on the position along the upstream–downstream gradient. These results could have important implications in terms of ecosystem monitoring as they could be useful in establishing areas that would need conservation prioritization.     

The influence of freshwater flows on two estuarine resident fish species show differential sensitivity to the impacts of drought,flood and climate change

Estuaries are particularly susceptible to climate change and drought resulting in atypical changes to freshwater flows. How such changes in flow impact on the ecology of estuarine fishes may depend on how a species moves in response to changing flow conditions. Acoustic telemetry was used to interpret fine-scale movements of two co-inhabiting estuarine fish species, black bream, Acanthopagrus butcheri and estuary perch, Macquaria colonorum in relation to freshwater flows, season and moon phase. We found black bream to be highly mobile, regularly travelling the length of the estuary and into the neighbouring estuaries. In contrast, estuary perch had particular home ranges and made occasional, upstream or downstream movements. Possibly influenced by freshwater flows, estuary perch moved at greater rates in the Tambo compared to fish in the Mitchell. Black bream resided in the upper estuary during winter and spring and the lower estuary during summer and autumn, whereas estuary perch remained in the upper estuary throughout the year, with occasional downstream movements in winter and spring. This study revealed 1) significantly large increases in freshwater flows result in mass downstream movements in both species, 2) fish moved upstream during full moons and 3) there are contrasting spatio-temporal patterns in movement between species. The results from this study highlight that estuarine fishes are likely to show differential sensitivity to the impacts of drought and climate change and illustrate how acoustic telemetry methods can be used to determine the environmental needs of fishes and help efforts to conserve and manage estuaries worldwide.     

Seasonal pattern of depth selection in smallmouth bass

The current study used a stationary acoustic telemetry array to monitor the depth selection of adult smallmouth bass Micropterus dolomieu in a large, oligotrophic lake in Ontario, Canada. At an annual scale, smallmouth bass demonstrated regular, seasonal changes in inhabited depths: fish occupied shallow water during the summer (2–5 m depth) and descended to deeper water (12–15 m depth) during winter under ice. Smallmouth bass remained above the thermocline in the summer, seasonal depth patterns did not vary across fish size and movements to and from seasonal depths were closely linked to the development and degradation of the thermocline. At finer time scales, smallmouth bass exhibited diel vertical migrations in summer, with fish moving to <2 m at night, and then descending to 3–5 m during the day. This pattern remained constant during the summer period examined, and varied with size such that larger fish remained deeper than smaller fish. During winter, depth did not vary across the 3-month monitoring period ( c . 14 m), but small (<2 m) changes in depth were observed periodically, suggesting limited movements were occurring. Results are further discussed in the context of climate change and reproductive success for this species.     

Response of Fish Assemblage Structure and Function Following Restoration of Two Small Bahamian Tidal Creeks

Disruption of hydrologic connectivity via road crossings is extremely common in Bahamian tidal creeks, resulting in increased sedimentation and decreased habitat quality and quantity for biota. We restored hydrologic connectivity (i.e., tidal flow) in two small Bahamian mangrove tidal creeks in May 2004 and 2005. We observed the characteristics of fish assemblage structure (species richness) and function (secondary production and transient species utilization of restored areas) before and after restoration, and compared these data with fragmented and unfragmented reference creeks. Restoration significantly increased species richness and secondary production of resident fish species in one of the two restored creeks. Increased utilization of the previously blocked wetlands by transient fishes was observed in both creeks. We suggest success could be attributed to the presence of adjacent nearshore recruitment sources, a more complex local seascape (i.e., high habitat heterogeneity in the creek and local nearshore), and the creation of deep upstream refugia pools. This is one of the first studies to use both structural and functional characteristics to monitor the success of restoration in mangrove ecosystems. Studies combining both structural and functional metrics in restoration monitoring are imperative in linking restoration ecology theory with practical ecological restoration efforts.     

Upstream-downstream movements of aquatic invertebrates in a Rocky Mountain stream

Simultaneous collections of drift and organisms moving either upstream or downstream in association with the substrate were made using a specially designed sampler. Samples were taken in a diel series along a transect across the study riffle of a Colorado foothills stream on six dates over an annual cycle. In addition to longitudinal movements, taxonomic composition and diel periodicity were evaluated. The insect-dominated fauna showed a net downstream displacement. Only the caddisflies Helicopsyche borealis and Hesperophylax occidentalis exhibited net upstream movement, primarily a result of low drift frequencies. The taxonomic composition of moving invertebrates differed from that of the benthos. Drift resembled downstream moving substrate-associated invertebrates in composition, but differed from that of the upstream directed fauna. Taxa collectively exhibited four types of diel patterns: 1) similar downstream (drift and substrate-associated movements) patterns, which generally differed from the upstream pattern; 2) similar benthic (upstream and downstream) patterns, which differed from that of drift; 3) aperiodic patterns; and 4) independent patterns for each type of directional movement. Analysis of size classes based on head capsule width for the mayfly Baetis tricaudatus showed significantly smaller size in stationary individuals compared with moving individuals in the population and revealed that nymphs moving during the day were smaller than those moving at night.     

Habitat use and fish activity of landlocked Atlantic salmon and brook charr in a newly developed habitat compensation facility

Degradation and destruction of valuable spawning and rearing habitat due to anthropogenic changes (e.g., flow modification and channelisation) is known to have dramatic impacts on fish populations. To compensate for habitat losses due to hydropower development, an artificial fluvial habitat channel (‘Compensation Creek’) was constructed in south-central Newfoundland, Canada. The creek was designed to include appropriate habitat features for the two dominant salmonid fish species, landlocked Atlantic salmon (Salmo salar L.) and brook charr (Salvenius fontinalis Mitchell). The study examines the habitat use of landlocked Atlantic salmon and brook charr in the Compensation Creek using electromyogram (EMG) radio telemetry. Ten landlocked Atlantic salmon and eight brook charr were captured and tagged with EMG transmitters. In laboratory swimming experiments, the EMG values were calibrated against swimming speed. Fish were then released in the Compensation Creek and tracked on a daily basis. The results show that (1) during residence in the creek, both species used preferentially the habitat features designed to match their rearing habitat preferences, and (2) swimming speed did not vary among habitat types for either species.     

Seasonal movements and residency of small-bodied fish in a north temperate urban watershed demonstrate connectivity between a stream and stormwater drain

Despite their often physical connection, neighbouring stormwater drains and urban streams are typically managed quite differently; with drains mostly regarded as poor fish habitat. The goal of this study was to evaluate the interconnectedness of an urban stream (Watts Creek) and adjoining earthen surface stormwater drain (Kizell Drain) from the perspective of fish residency and movements over an entire year. Using a stationary passive integrated transponder (PIT) array, we quantified and compared the direction of movements among Watts Creek, Kizell Drain, and the area downstream of their confluence (herein termed Main) for four common stream fishes. We also determined the residency time (percentage of total time in days) within each of these reaches by combining data from the array and recaptured (with electrofishing and identified with hand-held PIT reader) or portably detected (with mobile PIT reader) fish. While the movements of creek chub (Semotilus atromaculatus) and central mudminnow (Umbra limi) varied across seasons, creek chub resided significantly longer in Watts, while central mudminnow spent more time in Kizell and Main. Longnose dace (Rhinichthys cataractae) moved into and resided most often within Watts. The movements and residency time for white sucker (Catostomus commersonii) did not vary among the reaches. We conclude there is a high degree of connectivity between Watts Creek and Kizell Drain and that, with the exception of longnose dace, the three other species utilize the habitat available in Kizell. This study demonstrates the biological potential of earthen stormwater drains and as a result we recommend these systems be managed as a functional component of urban watersheds.     

Effects of hydrological variation and planktivorous competition on macroinvertebrate community structure in experimental billabongs

1. To study two factors which are predicted as causing changes to community structure in cut-off meanders (colloquially known in Australia as billabongs, a term of aboriginal origin), 16 experimental billabongs were constructed. These were designed to test two hypotheses: (a) that the structure of macrophyte and invertebrate communities within billabongs is altered by changing the pattern of flooding; and (b) that the presence of small planktivorous fish alters invertebrate community structure and diversity within billabongs.
2. An increase in the duration of flooding seems to favour animals better adapted to a greater availability of macrophyte habitat. Changing the seasonality of flooding resulted in prolonging of the time water was available over the summer months.
3. The presence of a planktivorous fish appears to affect macroinvertebrate communities through competition with other planktivores. Variable top-down pressure may create differing successional patterns and ultimately different communities at lower trophic levels.     

Managed flooding can augment the benefits of natural flooding for native wetland vegetation

Managed flooding is increasingly being used to maintain and restore the ecological values of floodplain wetlands. However, evidence for its effectiveness is sometimes inconsistent and water available for environmental purposes often limited. We experimentally inundated a floodplain wetland (or “billabong”) in late spring by pumping water from its adjacent creek, aiming to promote the native wetland flora and suppress terrestrial exotics. Vegetation was surveyed before (spring) and after (late summer) the managed flood in the experimental billabong and in three control billabongs. Floodplain water levels were continuously monitored. Wet conditions caused two of the control billabongs to also flood, but to a lesser extent than the experimental billabong. We therefore assessed vegetation changes relative to flooding duration. With increasing flooding duration, the cover of wetland vegetation (amphibious and aquatic species) increased and the cover of terrestrial and exotic vegetation decreased, with these effects largest in the deliberately flooded billabong. Flooding durations greater than 20 days generally resulted in increased cover of wetland plants and restricted the growth of terrestrial plants. Reinstatement of more appropriate flooding regimes can thus promote native wetland plants, while suppressing terrestrial exotic species. Our study also provides evidence for the use of modest water allocations to augment the benefits of natural flooding in the maintenance and restoration of native wetland plant communities.     

Distribution of six species of bitterlings in a creek in Fukuoka Prefecture,Japan

Comparative study on the distribution of six species of bitterling in a creek in Fukuoka Prefecture was carried out. The upper part of the creek was fluvial, and the lower part stagnant.Acheilognathus lanceolatus, A. tabira subsp. (b) of Nakamura (1969),A. rhombeus andRhodeus atremius showed wide distribution in the creek throughout their life.A. limbatus seemed to be a fluvial species, andR. ocellatus smithii a lentic species. In the spawning season, however, all the species of bitterling, exceptingR. o. smithii, probably possess a common spawning ground in which mussels occur at a relatively high density. Adult females ofA. lanceolatus, A. tabira subsp. (b) andR. atremius without ripe eggs aggregated in the lower, stagnant parts of the creek. Most juveniles of these species and ofA. rhombeus seemed to grow in the lower part of the creek, and then migrate upward untill their spawning season. No species among the same phylogenetic group has the same set of the life modes (spawning season, spawning sites, aggregation of females without ripe eggs in the lower part of the creek and probability of upstream migration of 0-year-old fish toward spawning sites).     

A long-term study (1985–1995) of fish populations in the impounded Warta River,Poland

Three sites, two in the tailwater and one upstream of the backwater of a large man-made reservoir in the middle course of the 808 km long lowland Warta River (Oder catchment), were studied. The pre-impoundment study lasted one (1985), the post-impoundment one 10 yr (1986–1995). The dam contributed to the extinction of the anadromous Vimba vimba, and of the rheophilous Chondrostoma nasus, both cyprinids. A number of directly or indirectly negative changes related to the construction of the reservoir were recorded in the tailwater. These changes affected the species number, spawning groups, diversity, density, standing crop, mean body weight, ABC index, and proportional stock density – PSD. Numerous impacts related to engineering, water chemistry and climate were more negative for fish at the tailwater than at the backwater sites. The hydrology of the site upstream of the backwater continued to be dependent on natural factors. Fish populations there suffered only from accidental impacts of the construction of the dam, such as bank revetment or the clearance of trees and shrubs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diel shifts in the structure and function of nearshore estuarine fish communities

Day–night shifts in the nearshore fish fauna of a temperate microtidal estuary were assessed using a holistic suite of structural and functional community attributes. Mean fish species richness and diversity (taxonomic distinctness) were higher at night across all regions of the estuary and seasons, concurring with the findings of numerous comparable studies reviewed worldwide, while the diel period in which mean abundance was higher varied among seasons. Likewise, species and functional guild compositions (the latter based on feeding modes and habitat use) both differed significantly between day and night, with the extent of the diel shift again varying seasonally. Daytime fish communities were characterized by higher abundances of Atherinidae, Sillaginidae and Mugilidae, while Gobiidae were far more abundant at night. Marked shifts in size composition were also evident, with smaller fishes (<100 mm total length, L_T) being more prevalent during the day and larger fishes (≥200 mm L_T) proportionally more abundant at night. The above diel shifts were feasibly related to a range of predator–prey interactions and feeding‐related movements, namely a nocturnal decrease in top‐order avian piscivory coupled with an increase in invertebrate prey availability, resulting in changes in the presence and catchability of certain fish species in shallow estuarine waters.     

Moving Day and Night: Highly Labile Diel Activity Patterns in a Tropical Snake

Most animals have well established diel activity patterns (e.g., diurnal, crepuscular, or nocturnal), and changes in behavior from diurnal to nocturnal are rare in single species. We radio tracked 50 keelback snakes in a single population, locating them up to four times a day, over five periods of the year in the Australian dry tropics to describe temporal variation in diel movement patterns. Snake body temperatures were also recorded to determine the relationship between activity patterns and body temperatures. Season influenced diel activity patterns significantly. Keelbacks were more likely to move, and moved further in the daytime in the mid‐dry (June–July), and late dry (Aug–Sep) seasons. In the mid‐dry season, 87 percent of movements were diurnal, whereas in the mid‐wet (Feb–March) season, although snakes were much more likely to move, only 43 percent of movements were diurnal. In the late dry season, snakes were slightly more likely to move at night than at any other time of day, and so at this time of the year, snakes could be classified as nocturnal. Thus, overall increased movements in the mid‐wet season (austral summer) were associated with more crepuscular and nocturnal movement. There was a significant relationship between individual snake body temperatures and movement rates in all seasons. Changes in movement patterns may be related to body temperature, and this diurnal species becomes cathemeral in the tropics in summer, when it is possible to maintain high body temperatures both day and night.     

Diel variation in availability and vulnerability of fish to a survey trawl

The effect diel variation in availability and vulnerability has on the fish capture process of a groundfish survey trawl was examined from data collected during an experiment measuring fish escapement underneath the footgear. The survey trawl was significantly more efficient at night in capturing American plaice, Hippoglossoides platessoides, and yellowtail flounder, Limanda ferruginea, but no difference was found in catches of Atlantic cod, Gadus morhua. This increase in capture efficiency at night is related to an increase in availability and vulnerability associated with diel variation in light intensity. No evidence of diel vertical migration was found and changes in availability were linked to visual dependent gear avoidance by the fish. Regardless of light conditions, the survey trawl had a very low capture efficiency for juveniles of the three species studied. Escapement of this size group was extremely high during both day and night periods due to a fast towing speed, use of large bobbin gear, and possible mesh selection.     

Amphibian communities associated with billabong habitats on the Murrumbidgee floodplain,Australia

Abstract A study of frog species richness and abundance at four permanent billabongs located in and around the city of Wagga Wagga, southern New South Wales, was carried out from the spring of 1991 to the autumn of 1992. During the sampling period a total of 404 individual adult frogs from six species were recorded. No egg masses or tadpoles were detected during a total of 32 survey hours. Four species of the Family Myobatrachidae represented 81% of the total number of adult individuals sampled, the remaining species belonging to the Family Hylidae. There were significant differences in the mean species richness and mean total number of adult individuals among billabongs. Significant positive correlations were recorded between total adult individuals, total frog species richness and the number of riparian plant species recorded at all billabongs. There were no significant correlations between adult frog numbers and meteorological and water quality parameters. The adults of the four most abundant frog species exhibited significant association with particular microhabitats surrounding billabongs; Crinia parinsignifera was associated with the creeping grass Paspalum distichum, Limnodynastes fletcheri with the rush Eleocharis sphacelata, L. tasmaniensis with sedges Cyperus spp. and the grass P. distichum and Litoria peronii with red gum Eucalyptus camaldulensis and introduced tree species. Differences in adult frog abundance between billabongs appears to be related to the disturbance of riparian vegetation by domestic stock, while the absence of eggs and tadpoles from these permanent billabongs may be explained by the presence of abundant exotic fish species in the billabongs.     

Spatial and Temporal Ecology of Native and Introduced Fish Larvae in Lower Putah Creek,California

For two years we studied the distribution and abundance of native and introduced fish larvae in Putah Creek (Yolo County, CA), a low elevation regulated stream. We used light traps and conical drift nets to sample the fish larvae at two spatially separated sites from March through July 1997 and at four sites from February through August 1998. Native larvae occurred both earlier in the year and in higher abundance than those of introduced species. Both native larvae and overall numbers of larvae were more abundant at upstream sites in both years. Sampling of larvae appeared to be sensitive to the detection of rare species. Drift nets and light traps collected similar numbers of larvae, but each method tended to select for different taxa. There were significant trends in diel patterns of abundance, with more fish larvae being found during the hours of darkness. We suggest that differences between the sites were due to habitat changes resulting from an upstream dam that has created a refuge of diverse habitat and cool flowing water for native taxa.     

Space use and feeding patterns of an offshore fish assemblage in a shallow mesotrophic lake

Synopsis Diel and spring/summer space-use and feeding patterns were investigated in an assemblage dominated by five fish species occupying the offshore waters of Lake Opinicon, a shallow mesotrophic lake in southeastern Ontario. We assessed fish distribution and diel movement in May and July through the use of gill nets set at various depths in 1.5–7.0 m depth contour zones, supplemented by observations of fish reaction to the nets. Golden shiners and alewives occupied the upper part of the water column, with the former concentrated at the littoral zone-open water interface, and the latter in the open water. Yellow perch occupied the lower part of the water column in all depth contours. Bluegills were abundant in the upper to midwater depths in all contour zones; black crappies were concentrated in the 2.5–3.5 m zones. All of these species showed either a diel or a spring-summer change in distribution pattern. Bluegills were more abundant in offshore locations in July, whereas golden shiners and yellow perch were more abundant onshore in May. Alewives and black crappies showed distinct diel movements in July, as they were largely absent from the study area during the day, but returned at night to feed. In general, there was more spatial separation among the five species in July than in May.Patterns of spatial distribution among the species generally corresponded with the type and variety of prey consumed, and with diel movement of prey in the case of water column feeders. Other factors that apparently affected spatial distribution and seasonal shifts in this assemblage were risk of predation (golden shiner), spawning activity (alewife), and a decline in prey abundance from spring to summer (bluegill and yellow perch).