Effects of coalbed natural gas development on fish assemblages in tributary streams of the Powder and Tongue rivers

1. Extraction of coalbed natural gas (CBNG) often results in disposal of large quantities of CBNG product water, which may affect aquatic ecosystems. We evaluated the effects of CBNG development on fish assemblages in tributary streams of the Powder and Tongue rivers. We used treatment and control, impact versus reference sites comparisons, surveys of CBNG product‐water streams and in situ fish survival approaches to determine if CBNG development affected fish assemblages. 2. Several of our results suggested that CBNG development did not affect fish assemblages. Species richness and index of biotic integrity (IBI) scores were similar in streams with and streams without CBNG development, and overall biotic integrity was not related to the number or density of CBNG wells. Fish occurred in one stream that was composed largely or entirely of CBNG product water. Sentinel fish survived in cages at treatment sites where no or few fish were captured, suggesting that factors such as lack of stream connectivity rather than water quality limited fish abundance at these sites. Fish species richness did not differ significantly from 1994 to 2006 in comparisons of CBNG‐developed and undeveloped streams. Biotic integrity declined from 1994 to 2006; however, declines occurred at both impact and reference sites, possibly because of long‐term drought. 3. Some evidence suggested that CBNG development negatively affected fish assemblages, or may do so over time. Specific conductivity was on average higher in treatment streams and was negatively related to biotic integrity. Four IBI species richness metrics were negatively correlated with the number or density of CBNG wells in the catchment above sampling sites. Bicarbonate, one of the primary ions in product water, was significantly higher in developed streams and may have limited abundance of longnose dace (Rhinichthys cataractae). Total dissolved solids, alkalinity, magnesium and sulphate were significantly higher in developed streams. 4. Biological monitoring conducted before the development of CBNG, and continuing through the life of development and reclamation, together with data on the quantity, quality and fate of CBNG product water will allow robust assessment of potential effects of future CBNG development worldwide.     

Low‐head dams induce biotic homogenization/differentiation of fish assemblages in subtropical streams

Extensive distribution of widespread species and the loss of native species driven by anthropogenic disturbances modify community similarity, resulting in a decrease or increase in community distinctiveness. Data from four basins in the Wannan Mountains, China, were used to evaluate the effects of low‐head dams on patterns of fish faunal homogenization and differentiation based on abundance data. We aimed to examine the spatial changes in taxonomic and functional similarities of fish assemblages driven by low‐head dams and to examine whether the changes in the similarity of fish assemblages differed between taxonomic and functional components. We found that low‐head dams significantly decreased the mean taxonomic similarity but increased the mean functional similarity of fish assemblages in impoundments using abundance‐based approaches, suggesting that taxonomic differentiation accompanied functional homogenization in stream fish assemblages. These results show the importance of population abundance in structuring fish faunal homogenization and differentiation at small scales, especially when the major differences among assemblages are in species abundance ranks rather than species identities. Additionally, we also found only a weak positive correlation between changes in mean taxonomic and functional similarities, and partial pairs exhibited considerable variation in patterns of fish faunal homogenization and differentiation for taxonomic and functional components. In conclusion, this study highlighted that the observed taxonomic differentiation of current fish assemblages (short‐term phenomenon) is probably an early warning sign of further homogenization in regions where native species are completely predominated and that changes in taxonomic similarity cannot be used to predict changes in functional similarity.     

Habitat Partitioning in a Patchy Environment: Considering the Role of Intraspecific Competition

Coexistence of many size groups of conspecifics in habitat patches may complicate resource partitioning and increase intraspecific interactions. The objectives of my study were to determine partitioning of habitat among age groups of rainbow trout, Oncorhynchus mykiss, coexisting in pool habitat of a headwater stream, and to determine the role of intraspecific competition for such resource partitioning. The trout population showed size and age specific patterns of habitat use, and trout selected locations based on depth and longitudinal position. This habitat use pattern decreased intraspecific overlap among the trout age groups for use of pool space. I used a removal experiment to determine if two-year old trout constrained habitat use by the smaller conspecifics. Although the experimental results imply that recent intraspecific competition was not present, the absence of competitive exclusion was not clearly demonstrated because of low experimental power. While this study identified habitat partitioning among the trout age groups, it remains unclear whether biotic interactions or size specific requirements were causing the habitat use patterns.     

Spatial and temporal variation of fish assemblage in two intermittent streams in north‐western Zimbabwe

This study examined the spatial and temporal variation in fish assemblage composition within two intermittent streams in north‐western Zimbabwe. Eight sites were sampled during three different periods of flow. Twenty‐five species in eight families, dominated by cichlids and cyprinids, were collected. Redundancy analysis (RDA) was used to explore the relationship between species and their environmental correlates. According to variation partition, 68.1% of assemblage variation was explained by both habitat and temporal variables. Most species were associated with large pools, whereas small species were associated with habitats that had gravel and boulders. The temporal aspect suggested a pattern associated with high catch per unit effort (CPUE) for the mormyrids, Clarias gariepinus and Labeo altivelis, during the early rain period. By comparison, the late rain period was associated with high CPUE for Labeo cylindricus, Labeobarbus marequensis, Chiloglanis neumanni and Oreochromis mortimeri, whereas the rest of the species had high CPUE during both the late rain and dry periods. The assemblage composition was more diverse during the late rain period. Refuge availability during the dry period appeared to be essential for the assemblage of the intermittent streams. Protection of these temporal habitats is therefore important in conserving fish assemblages within intermittent streams of the Lake Kariba area.     

Habitat quality affects the condition of Barbus sclateri in Mediterranean semi-arid streams

We investigated the site level relationships between fish condition and environmental variables in Sclater's barbel, Barbus sclateri, from semi-arid streams in the south-eastern Iberian Peninsula. These freshwater ecosystems are characterized by strong seasonal fluctuations in flow levels (droughts and floods) as a consequence of their irregular hydrological regime on both an annual and pluriannual scale. We analysed the relationships between 11 ecosystem variables [conductivity, oxygen concentration, water temperature, pH, seasonal water flow, dominant substrate, submerged vegetation, QBR (Riparian Ecosystems Quality Index), BMWP' (Spanish version of the Biological Monitoring Working Party), fish refuge index and fish density] and fish condition by comparing mass–length relationships of nine populations of Sclater's barbel located in five sub-basins with different environmental conditions. Fish condition differed between the populations studied and was mainly dependent on the ecological variables related with water flow and, consequently, the physical structure of the streams, which is directly related to substrate and fish refuge.     

Effects of reduced‐impact logging on physical habitat and fish assemblages in streams of Eastern Amazonia

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Spatial and seasonal patterns of fish assemblages in mountain streams of the Ren River,southwest China

The spatial–temporal patterns of fish assemblages in lotic systems can provide useful information in developing effective conservation measures. This study aimed to explore the spatial and seasonal changes in fish assemblages and their association with environmental factors in mountain streams of the Ren River, southwest China. Field investigations were conducted at 18 sites during the rainy and dry seasons in 2017. A total of 1,330 individuals, belonging to three orders, eight families, 19 genera, and 21 species, were collected. Analysis of similarities (ANOSIM) showed that the structure of fish assemblages varied significantly at the spatial scale, but not at the seasonal scale. In low‐order sites, fish assemblages were mainly dominated by cold‐water and rheophilic species (e.g., Rhynchocypris oxycephalus, Scaphesthes macrolepis, Metahomaloptera omeiensis, and Gnathopogon herzensteini), while those in high‐order sites were predominated by warm‐water and eurytopic or stagnophilic species (e.g., Squalidus argentatus, Hemiculter leucisculus, and Zacco platypus). Canonical correspondence analysis (CCA) showed that the fish assemblages were structured by a combination of large‐scale landscape factors (e.g., altitude and C‐link) and small‐scale habitat features (e.g., channel width, water temperature, and depth). Among these factors, landscape had the greatest influence on fish assemblages, while local habitat variables were less important or were only significant in certain seasons.     

Critical landscape attributes that influence fish population dynamics in headwater streams

Three landscape attributes are likely to have strong effects on the rate-dependent processes determining fish population dynamics in headwater streams: (1) functional interactions at terrestrial-aquatic ecotones and their influence on temporal and spatial variation in resource supply and predator-prey interactions, (2) large-scale spatial habitat relationships and their effect on resource use and fish movement, and (3) presence of refugia from harsh environmental conditions and their influence on fish survival and emigration/immigration rates. Elucidating how these factors interact over a range of temporal and spatial scales should be a major goal of lotic fish ecologists.     

Habitat diversity and fish assemblages in an African river basin (Nyagui River, Zimbabwe)

Little is known about the ecology of stream fishes in Zimbabwe and this study investigated fish communities in the Nyagui River basin and is one of the first to examine the relationship between fish assemblages and habitat diversity in Zimbabwe. Fourteen sampling stations were, for convenience, divided into three groups; upper (>1400 m above sea level), middle (1000–14000 m) and lower stations (<1000 m). A total of 24 species were collected, four of which were introduced, and the species composition differed according to the location of the stations. Species that favoured running water and/or rocks were generally absent from the upper stations, reflecting the fact that they were mostly sandy‐bottomed and still. Diversity and relative abundance increased in the mid‐ and low‐altitude stations, which were rockier and faster flowing. Both species diversity and relative abundance increased with the catchment area above each station, which was attributed to increased habitat diversity in larger streams. This view was supported by a strong correlation between habitat diversity and catchment area, and between habitat diversity and species richness and relative abundance. At present, the Nyagui system is relatively unregulated but the Kunzvi Dam, presently under construction, will change this situation and species diversity is likely to decrease owing to the loss of rheophilic species while other groups, notably cichlids and introduced species will increase.     

Habitat ecology of chironomid larvae of the Big Thicket streams

Chironomid larvae were collected from streams in the Big Thicket area of East Texas from November, 1981 to October, 1982. Primary stations were sampled monthly and secondary stations bi-annually. Samples of leaf debris, wood debris, and sand were taken from each station and the chironomid larvae occupying the substrates were analyzed.A total of 15 112 individuals including 87 species were collected. Four subfamilies of Chironomidae were represented: Tanypodinae (12 species), Diamesinae (2 species), Orthocladiinae (30 species), and Chironominae (43 species). The collections yielded a larger number of individuals and species than previous environmental studies in the Big Thicket. Twenty-two species are reported for the first time from Texas.The lowest number of individuals occupied the leaf debris with Rheotanytarsus sp. and Tanytarsus sp. 2 being dominant. The wood debris, probably the most stable of the substrates, contained the highest number of species with Tanytarsus sp. 2 being dominant. Most individuals occurred in the sandy bottom where Lopescladius sp. was dominant. Tanytarsus sp. 1 occurred in over 65 percent of the samples.The populations were generally higher during the autumn. This was probably a result of the life cycle and the effects of environmental factors. More younger instars occurred during the late summer and autumn. Also, water flow during the summer and autumn was low, providing a more stable environment, promoting chironomid population growth.     

Impact of drought upon fish assemblage structure in two South Carolina Piedmont streams

The effects of drought on fish assemblages were studied in the Indian Creek (228 km²) and Kings Creek (46 km²) watersheds located in the Piedmont Province of South Carolina. Water and fish samples were collected at 13 localities during drought conditions in 2000 and again under post-drought conditions in 2003. Abundance, species richness, and Simpson’s diversity were calculated for each locality, and the masses and lengths of individual fishes were measured to determine total biomass and length distributions for each species. Assemblages were significantly different from 2000 to 2003 at 10 of the 13 sample localities (χ² test for association; p < 0.05). The family Cyprinidae (minnows) was numerically dominant in both years and in both watersheds, but their dominance declined somewhat following the drought due to lower numbers of Nocomis leptocephalus and Notropis lutipinnis in 2003 collections. However, some cyprinids increased in abundance in 2003 collections, most notably Semotilus atromaculatus and Hybopsis hypsinotus. Abundance of catostomids (suckers) and ictalurids (catfish) was also decreased post drought. Conversely, centrarchids (sunfish) increased in dominance in 2003, especially the species Lepomis macrochirus and Lepomis gulosus. Many more juveniles and young of the year were observed in 2003 collections, suggesting that most species exhibited greater reproductive success following the drought. The significant differences in water chemistry observed between the two years were not associated with any change in fish community structure. Instead, we attributed the observed differences in fish assemblages to changes in habitat structure associated with higher rainfall during post-drought conditions. Finally, sample localities showed high variability in common measures of assemblage structure, including abundance, species richness, and diversity. We hypothesize that the observed variability in community structure is caused by the heterogeneous habitat structure and morphology of these small Piedmont Province streams.     

Reef fish assemblages in north-western Sri Lanka: distribution patterns and influences of fishing practises

The distribution and abundance of reef fishes in relation to habitat structure were studied within Bar Reef Marine Sanctuary (BRMS) and on an adjacent reef, disturbed by destructive fishing techniques, in north-western Sri Lanka, by visually censusing 135 species groups using fifty metre belt-transects. Two types of continental shelf patch-reefs are found in the study area: coral reefs and sandstone reefs, which are divided into distinct habitats, four for the coral reef (shallow reef flat, shallow patch reef, deep reef flat and Porites domes) and two for the sandstone reef (structured sandstone-reef and flat sandstone-reef). Fish assemblages varied in structure between reef types and among habitats within reef types. Functional aspects of habitat structure and composition, such as available food and shelter, seemed to be important factors influencing distribution patterns. The strongest separation in the organisation of fish assemblages in BRMS was between reef types: 19% of all species were confined to the coral-reef patches while 22% were restricted to the sandstone reef patches and 59% were represented on both reef types. In terms of distribution among habitats, 21% of all species were restricted to one habitat while only 1.5% were present in all. The highest density of fish was in the coral reef habitats while highest species diversity was found in the most structurally complex habitat: the structured sandstone-reef. This habitat also had the highest proportion of species with restricted distribution. Planktivores were the most abundant trophic group in BRMS, and the species composition of the group varied among habitats. The comparison of the disturbed reef with BRMS suggested that habitat alteration caused by destructive fishing methods has strongly influenced the fish community. Within the fished area the structure of the fish assemblages was more heterogeneous, fish abundance was lower by an order of magnitude and species numbers were lower than in BRMS.     

Climate change hastens the turnover of stream fish assemblages

Stream fish are expected to be significantly influenced by climate change, as they are ectothermic animals whose dispersal is limited within hydrographic networks. Nonetheless, they are also controlled by other physical factors that may prevent them moving to new thermally suitable sites. Using presence–absence records in 655 sites widespread throughout nine French river units, we predicted the potential future distribution of 30 common stream fish species facing temperature warming and change in precipitation regime. We also assessed the potential impacts on fish assemblages' structure and diversity. Only cold-water species, whose diversity is very low in French streams, were predicted to experience a strong reduction in the number of suitable sites. In contrast, most cool-water and warm-water fish species were projected to colonize many newly suitable sites. Considering that cold headwater streams are the most numerous on the Earth's surface, our results suggested that headwater species would undergo a deleterious effect of climate change, whereas downstream species would expand their range by migrating to sites located in intermediate streams or upstream. As a result, local species richness was forecasted to increase greatly and high turnover rates indicated future fundamental changes in assemblages' structure. Changes in assemblage composition were also positively related to the intensity of warming. Overall, these results (1) stressed the importance of accounting for both climatic and topographic factors when assessing the future distribution of riverine fish species and (2) may be viewed as a first estimation of climate change impacts on European freshwater fish assemblages.     

Habitat use of the European mudminnow Umbra krameri and association with other fish species in a disconnected Danube side arm

Fish assemblages along the longitudinal course of an old, disconnected and modified side arm of the Danube floodplain downstream of Vienna, Austria, as well as habitat structure, hydro‐morphological and hydro‐chemical factors, were investigated in order to analyse the key environmental determinants of the European mudminnow Umbra krameri. Generally, U. krameri was the most abundant species in the system. It occurred in disconnected ditches, ponds and pools with dense reed belts and comparatively low nutrient content, indicating its natural association with marsh habitats. At infrequently disturbed sites it was associated with a small group of stagnophilious and highly specialized species with adaptations to strong oxygen fluctuations. At frequently flooded sites, the species was absent or occurred in low abundances, indicating its adaptation to water bodies in older successional stages and its low competitive power in permanently connected floodplain habitats.     

Habitat structure and invertebrate assemblages on stream stones: A multivariate view from the riffle

Abstract Highly structured habitats, those with complex or heterogeneous physical structure, commonly contain more species than simply structured ones. However, tests of this relationship have been hampered by habitat-specific definitions and measurements of habitat structure and, in stream studies, by insufficient information on spatial variation in faunal abundances. We sampled the fauna of 90 stones collected from an order 4 section of the Taggerty and Steavenson Rivers, southeastern Australia. The spatially nested sampling design encompassed three spatial scales (sites within the same stream order, riffles at the same site and groups of stones within the same riffle) but no temporal replication, as we were only able to sample once. Habitat structure of stones was quantified by measuring the amount and type of epilithon on stones, together with stone shapes, sizes, textures and surface complexities. For the latter two attributes, we used a new method, involving image analysis, which can be used to quantify habitat structure in comparable ways in other systems. Species richness (S) was related to some measures of habitat structure, being higher on stones with a rough texture and weakly related to the amount of epilithon present. Total numbers of individuals (N) were also higher on rough stones, and faunal composition (as quantified by hybrid multidimensional scaling) was related to abundance of epilithon. However, flow environments, as quantified by water velocities and depths, were also related to faunal composition. Riffles varied in both faunal densities and near-bed flow environment, but not in any consistent way. Such variability means that individual riffles cannot be reasonably used to ‘represent’ stream sections or orders, an assumption commonly made in stream studies. Neglect of such issues has also resulted in poor conceptual integration between large- and small-scale studies in stream ecology.     

Seasonal variation in the composition of fish assemblages in small Amazonian forest streams: evidence for predictable changes

1. The effects of seasonal inundation on the biology of fishes on floodplains of large Amazonian rivers are well studied. However, the small seasonal changes in headwater streams are generally considered to have little effect on fish assemblages. 2. In this study, we analysed seasonal changes in the species composition and abundance of fish in small Amazonian forest streams. We sampled fish with hand and seine nets in headwater streams in a 10 000 ha terra‐firme forest reserve near Manaus, Brazil. Each stream was surveyed at the end of the 2005 dry season, at the beginning of the 2006 rainy season and at the beginning of the 2006 dry season, by means of a standardized sampling effort. 3. The numbers of individuals and species caught were higher in the dry season, but rarefaction analyses indicated that greater species numbers could have been due simply to the larger number of individuals caught. 4. Between the dry and rainy season, the direction of changes in species composition in multivariate space varied among sites, especially for quantitative (abundance) data. However, the observed variation among sites was the less than expected if the directions of change were random. 5. Fish assemblages in the second dry season were more similar to those in the previous dry season than expected if changes in species composition among seasons were random. This indicates that a general seasonal pattern in fish assemblages can be detected, despite the existence of some erratic site‐specific changes. 6. Most of the species that showed large seasonal variations in density occupy temporary ponds during the rainy season, when much of the valley is inundated and pond networks form adjacent to streams. Short‐duration lateral migrations to these ponds may play an important role in the seasonal fish‐assemblage dynamics in Amazonian headwater streams. 7. Our results contrast with previous studies on small Amazonian streams, which have found little seasonal change in fish assemblages, and highlight the importance of the abundance of common species as an indicator of general fish assemblage structure in biological monitoring programmes.     

Rehabilitation of aquatic habitats in warmwater streams damaged by channel incision in Mississippi

Channel incision has major impacts on stream corridor ecosystems, leading to reduced spatial habitat heterogeneity, greater temporal instability, less stream-floodplain interaction, and shifts in fish community structure. Most literature dealing with channel incision examines physical processes and erosion control. A study of incised warmwater stream rehabilitation was conducted to develop and demonstrate techniques that would be economically feasible for integration with more orthodox, extensively employed watershed stabilization techniques (e.g., structural bank protection, grade control structures, small reservoirs, and land treatment). One-km reaches of each of five northwest Mississippi streams with contributing drainage areas between 16 and 205 km2 were selected for a 5-year study. During the study two reaches were modified by adding woody vegetation and stone structure to rehabilitate habitats degraded by erosion and channelization. The other three reaches provided reference data, as two of them were degraded but not rehabilitated, and the third was only lightly degraded. Rehabilitation approaches were guided by conceptual models of incised channel evolution and fish community structure in small warmwater streams. These models indicated that rehabilitation efforts should focus on aggradational reaches in the downstream portions of incising watersheds, and that ecological status could be improved by inducing formation and maintenance of stable pool habitats. Fish and physical habitat attributes were sampled from each stream during the Spring and Fall for 5 years, and thalweg and cross-section surveys were performed twice during the same period. Rehabilitation increased pool habitat availability, and made the treated sites physically more similar to the lightly degraded reference site. Fish communities generally responded as suggested by the aforementioned conceptual model of fish community structure. Species composition shifted away from small colonists (principally cyprinids and small centrarchids) toward larger centrarchids, catostomids, and ictalurids. Fish density and species richness increased at one rehabilitated site but remained stable at the other, suggesting that the sites occupied different initial states and endpoints within the conceptual model, and differed in their accessibility to sources of colonizing organisms. These experiments suggest that major gains in stream ecosystem rehabilitation can be made through relatively modest but well-designed efforts to modify degraded physical habitats. This revised version was published online in July 2006 with corrections to the Cover Date.     

When partitioning is not an option: Resource availability predicts intraguild interactions in two isolated Amazonian primate assemblages

Assemblage structure and acquisition of high-value resources will usually be affected by changes in resource availability and differential competitive abilities of assemblage members. In fragmented habitats where carrying capacity limits are exceeded due to high population densities and biomass, interspecific interactions can be expected to occur at a high frequency, potentially turning into an important cost for coexistence. We studied assemblage- and guild-level patterns of interspecific interactions in two highly diverse isolated primate assemblages in southern Amazonia. Specifically, we assessed the effects of temporal variation in fruit availability on the rates of interspecific interactions between gray woolly monkeys (Lagothrix lagotricha cana), one of the largest tree-dwelling mammals of the Amazon forests, and nine syntopic primate species. We found that fruit availability positively predicted rate of intraguild interactions in contrast to overall assemblage interaction rate. We did not find statistical evidence for the effect of fruit availability on the assemblage rates of type-dependent (i.e., agonistic or non-agonistic) and context-dependent (i.e., feeding or non-feeding) interactions. However, there was a clear trend toward increased feeding-related and agonistic-related interactions as fruit availability increased, with agonistic interactions mostly occurring at guild-level. These results provide support for a significant role of fruit availability in structuring spatial–temporal intraguild interactions at our study sites. Costly interspecific interactions and spatial habitat overlap can be expected to occur at a high frequency in highly diverse assemblages living in human-modified landscapes, which in turn, can have potentially negative impacts to the species involved.