Predicting community characteristics from habitat conditions: fluvial fish and hydraulics

1. One current approach to the prediction of community characteristics is to use models of key local-scale processes (e.g. niche dimensions) affecting individuals and to estimate the effects of these attributes over larger scales. We tested this approach, focusing on how the hydraulic habitat structures fluvial fish communities. 2. We used a recent statistical habitat model to predict fish community characteristics in eleven reaches in the Rhône river basin in France. Predictions were made ‘blindly’ since most reaches were not used to calibrate the model. The model reflects species preferences for local hydraulics. We made predictions of the fish community from the local hydraulic conditions found in the reaches under low flow conditions. The overall abundance and the relative abundance (both as indices) of fish species, specific size classes and species traits (i.e. reproductive, trophic, morphological and others) were predicted. We summarized our predictions of the relative abundance of species as two ‘community structure indices’ using Principal Component Analysis. 3. Our predictions from low-flow hydraulics were compared with long-term observations of fish communities. The relative abundance of species actually observed depended largely on zoogeographic factors within the Rhône basin which could not be predicted by the model. The model predicted 13% of the variance in the indices of relative abundance at the species level and 23% of this variance at the trait level for all zoogeographic regions combined. However, when focused on reaches within a geographic region, the model explained up to 47% of the same variance. Therefore, geographic regions act as ‘filters’ on the relative abundance of species, but hydraulics do affect fish communities within a given geographical context. 4. For the synthetic ‘community structure indices’, we obtained good predictions from hydraulics independently of the geographical context (variance explained up to 95%). These indices were linked to simple key hydraulic characteristics of river reaches (Froude and/or Reynolds number). The indices enabled interpretations of the links between hydraulics, geomorphology, discharge and community patterns. These links were consistent with existing knowledge of species and their traits. 5. In addition to the above validations, the habitat model partly explained the observed effects of impoundment on fish communities. 6. The present results show that stream hydraulics strongly impact fish community structure. Consequently, our findings confirm that community characteristics can be predicted using models of the local-scale habitat requirements of the species forming the community.     

Simple predictions of instream habitat model outputs for fish habitat guilds in large streams

1. In the context of a generalised modification of hydraulic conditions in medium to large streams, modelling the impacts of stream regulation on fish communities in multiple streams is an important challenge for basic and applied freshwater ecology. Conventional instream habitat models such as PHABSIM link a hydraulic model with preference curves for various species to estimate habitat value changes with discharge in stream reaches. Despite world‐wide applications, they have been scarcely used in multiple sites with multiple species. 2. We assigned 21 size classes of European fish species to four habitat guilds (cluster analysis grouping size classes with comparable microhabitat preference curves). Then, we ran a conventional instream habitat model on 28 French stream reaches belonging to the `barbel zone', to estimate habitat values versus discharge curves for the 21 size classes. We summarised the outputs as mean habitat values for guilds, and tested if they were predictable from average characteristics of reaches (discharge, depth, width, particle size). 3. As was obtained elsewhere for populations, habitat values for guilds were strongly related to average, dimensionless characteristics of reaches. The Reynolds number of reaches, equivalent to a discharge per width unit, reflected most of the discharge‐dependent changes in habitat values (within reaches). In particular, habitat values of species preferring bank (respectively midstream) microhabitats decreased (respectively increased) with increasing Reynolds number. The Froude number at median discharge was the major predictor of reach‐dependent but discharge‐independent variations in habitat values. Habitat values of species preferring riffle versus pool or bank microhabitats were higher in reaches with high Froude numbers. These relationships were consistent with existing knowledge on the different species. 4. Such results suggest that the input variables required to estimate habitat values for fish communities can be greatly simplified, as illustrated by a general estimation of the sensitivity of species preferring midstream habitats to discharge changes in any reach. Cost‐efficient alternatives to conventional instream habitat models should facilitate their validation in multiple sites, a point that remains critical in instream habitat modelling of fish communities.     

Habitat preferences of European grayling in a medium size stream, the Ain river, France

The three grayling Thymallus thymallus age-classes had strong preferences for their local habitat in the Ain river. All age-classes preferred high water velocities between 70 and 110 cm s^-1, confirming that grayling is a typical rheophilic species. An important intraspecific segregation regarding depth occurred, as large individuals preferred deeper water than small ones (optimal ranges=50–60, 80–120 and 100–140 cm for 0+, 1+ and adults respectively). The three age-classes had similar preferences for small substratum articles, with optimal values between 0·5 and 16·0 mm. Preference curves were generally comparable between the two sites, despite important differences in habitat availability. It is emphasized that grayling needs various habitat conditions to achieve its entire life cycle. The increasing scarcity of this species underlines the urgency of protecting lotic habitat integrity and diversity.     

枸杞岛潮下带沙地生境鱼类群落结构和季节变化

为了解岛礁水域沙地生境的鱼类群落结构特征,评估该生境对鱼类资源养护的潜在作用,于2009年采用多网目组合刺网对枸杞岛潮下带沙质区域进行了逐月采样,同步设置岩礁为对照生境.应用α和β多样性指数结合相对重要性指数、相对渔获率、ABC曲线和聚类排序方法对两种生境中的鱼类组成、多样性变化和群落格局与变化进行了全面探讨.全年在沙地和岩礁生境共采集鱼类63种,隶属11目38科56属,2种生境各自出现的鱼类皆为46种.受暖水种频繁出现在沙地生境的影响,潮下带沙质区域鱼类区系比岩礁生境略显丰富,且春夏季的渔获量普遍高于岩礁生境;由于种类组成均匀度较低,沙地生境各季节的α多样性普遍较低,夏季显著低于岩礁生境.日本须鳎是沙地生境的指示种,为早春、夏末和秋冬季沙地底层优势鱼种.5-7月鳀、多数月份鲻和10月份鳗鲇等种类对沙地生境的阶段性利用,使其形成了区别于以趋礁性鱼类为优势类群的岩礁生境的群落格局和季节动态.沙地是多种鱼类幼鱼阶段的庇护所和饵料场,是鲆鲽类的良好栖息地.沙地生境在维持鱼类区系和养护鱼类资源方面具有重要作用.     

Microhabitat use and preferences of the endangered Cottus gobio in the River Voer, Belgium

Microhabitat use and preferences of juvenile and adult bullhead Cottus gobio , from the River Voer, Flanders, were studied and compared across different seasons. Water depth, water velocity near the substratum, surface water velocity and substratum type used by C. gobio differed between seasons. These differences, however, were not attributable to differences in microhabitat availability. Adults appeared to prefer higher water velocities and coarser substrata than the average ones available in the basin. Although water depth appeared to have little influence on seasonal variation of microhabitat use in adult C. gobio , juveniles preferred deeper water and coarser substrata in winter, whereas in summer they appeared to use shallower water. There was a difference in microhabitat use between juvenile and adult bullhead only in summer.     

Relationships between fishes and habitat in rainforest streams in Sabah, Malaysia

Distinct fish assemblages were found at the mesohabitat scale in 14 streams in eastern Sabah, Malaysia. Sites were designated a priori as pool, run or riffle on the basis of physical habitat structure and properties. Principal components analysis of physical habitat data confirmed the validity of the a priori designation with a major axis of three correlated variables: water velocity, depth and substratum type. Canonical discriminant analysis on fish abundance and biomass data confirmed the existence of a specialized assemblage of fishes from riffle areas of all streams. Overall, pool and run assemblages were highly variable, dependent on stream size, but also variable between streams of the same size. Multiple regression of species richness, diversity, abundance and biomass data on principal components revealed significant but low correlations with measured habitat variables. Riffle habitats showed lower species richness and diversity but high abundance. The fish assemblage in riffles was dominated by balitorid species, specialized for fast-water conditions. Pool assemblages had the highest species diversity and were dominated by cyprinid species of a number of morphological and ecological guilds. Run assemblages were intermediate in assemblage characteristics between riffle and pool assemblages. Between-stream variation in assemblage composition was less than within-stream variation. Of 38 species collected, seven could be designated as riffle specialists, 18 as pool specialists and 13 as ubiquitous, although most of the latter showed size-specific habitat use with larger size classes found in slower, deeper water.     

Fish abundance and habitat relationships in forest and grassland streams, northern Hokkaido, Japan

The relationships between habitat variables and population densities of masu salmon (Oncorhynchus masou), rosyface dace (Leuciscus ezoe), Siberian stone loach (Noemacheilus barbatulus) and wrinklehead sculpin (Cottus nozawae) were examined by data collected at 55 reaches in forest and grassland streams in northern Hokkaido, Japan. Regression analysis suggested that salmon and dace densities were affected by water temperature (negative for salmon, positive for dace) and structural habitat factors (woody debris for salmon, pools for dace). Salmon density was higher in forest reaches than in grassland reaches, whereas dace density was higher in grassland reaches, suggesting that the removal of riparian forest had raised water temperature and allowed upstream invasions by dace. In contrast to salmon and dace, neither the density of loach nor sculpin differed between the forest and grassland reaches. For their densities, a negative effect of each on the other was most important, suggesting a strong effect of interspecific competition between loach and sculpin on their distributions. However, regression models also suggested that substrate heterogeneity mediated the outcome of their interspecific competition. On the basis of the results, a scenario is predicted for a fish-assemblage change with a typical land-development process in Hokkaido, and the importance of leaving or restoring riparian buffer for conservation and restoration of stream habitat is emphasized.     

Fish size and habitat depth relationships in headwater streams

Summary Surveys of 262 pools in 3 small streams in eastern Tennessee demonstrated a strong positive relationship between pool depth and the size of the largest fish within a pool (P<0.001). Similarly, the largest colonizers of newly-created deep pools were larger than the colonizers of shallow pools. We explored the role of predation risk in contributing to the bigger fish — deeper habitat pattern, which has been noted by others, by conducting five manipulative field experiments in two streams. Three experiments used stoneroller minnows (Campostoma anomalum); one used creek chubs (Semotilus atromaculatus); and one used striped shiners (Notropis chrysocephalus). The stoneroller experiments showed that survival of fish approximately 100 mm in total length (TL) was much lower in shallow pools (10 cm deep) than in deep (40 cm maximum) pools (19% versus 80% survival over 12 d in one experiment) and added cover markedly increased stoneroller survival in shallow pools (from 49% to 96% in an 11-d experiment). The creek chub experiment showed that, as for stonerollers, pool depth markedly influenced survival: the chubs survived an average of 4.9 d in shallow pools and >10.8 d in deep pools. In the striped shiner experiment in shallow artificial streamside troughs, no individuals 75–100 mm TL survived as long as 13 d, where-as smaller (20–25 mm) fish had 100% survival over 13 d. The results of the experiments show that predation risk from wading/diving animals (e.g., herons and raccoons) is much higher for larger fishes in shallow water than for these fishes in deeper water or for smaller fish in shallow water. We discuss the role of predation risk from two sources (piscivorous fish, which are more effective in deeper habitats, and diving/wading predators, which are more effective in shallow habitats) in contributing to the bigger fish — deeper habitat pattern in streams.     

Effects of habitat size and isolation on species immigration–extinction dynamics and community nestedness in a desert river system

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Population fluctuations in relation to seasonal habitat preferences of the Swainson's spurfowl, Pternistis swainsonii

Counts on Swainson's spurfowl Pternistis swainsonii were made during 1998–1999 within an intensive, fine‐grained, agricultural landscape to estimate population parameters, seasonal dispersion and habitat preferences. Radio‐transmitters were fitted to four birds to note habitat use and home ranges within the Summer breeding season. During Winter, population densities peaked, and birds exploited agricultural crops extensively. At the onset of Spring, densities dropped as birds paired to establish non‐overlapping breeding territories over a number of habitats with apparently sufficient cover and ‘natural’ food. Expanding grazed grassland appears to be the greatest threat to Swainson's spurfowl due to a lack of cover and food. The matrix of habitats within the landscape plays important roles in the success of this opportunistic spurfowl. Agricultural crops in the Winter sustain the population until the following Summer when natural savanna and ungrazed grasslands provide complementary foraging, nesting and roosting sites.     

Habitat preferences and habitat restoration options for small‐bodied and juvenile fish species in the northern Murray–Darling Basin

Degradation of instream habitats in the northern Murray–Darling Basin has occurred through numerous stressors, including siltation, clearing of bankside vegetation, intrusion of livestock and impacts of pest species. A better understanding of habitat preferences of native fish species could help guide future instream habitat restoration actions. The habitat choices of seven native fish species, juvenile Murray Cod (Maccullochella peelii), juvenile Golden Perch (Macquaria ambigua ambigua), juvenile Silver Perch (Bidyanus bidyanus), adult Murray–Darling Rainbowfish (Melanotaenia fluviatilis), adult Olive Perchlet (Ambassis agassizii), adult Un‐specked Hardyhead (Craterocephalus stercusmuscarum fulvus) and adult carp gudgeons (Hypseleotris spp.) were tested in preference troughs to help inform potential habitat restoration actions in the Condamine catchment. Each species was given a choice between pair combinations of open sandy habitat, submerged macrophytes, emergent plants and rocky rubble. Habitat preferences varied between species. Murray Cod, Golden Perch, carp gudgeons and Olive Perchlets preferred structure over open sandy habitat, whilst juvenile Silver Perch, Un‐specked Hardyhead and Murray–Darling Rainbowfish did not avoid open sandy habitats. Juvenile Murray Cod preferred rocky rubble habitat over all other habitat choices. Use of complex rock piles to provide nursery habitat for Murray Cod populations is a potential restoration option. Introduction of rock could also benefit Golden Perch and carp gudgeons. Use of emergent plants, submerged macrophytes and rocky rubble for habitat restoration all appear to have merit for one or more species of small‐bodied fishes or juvenile stages of larger sized fishes. Rocky rubble or floating attached macrophytes could be viable restoration options in areas too turbid to establish submerged macrophytes. These habitat interventions would complement existing actions such as re‐snagging and provision of fish passage to assist with sustainable management of native fish populations.     

Measurements of salmonid population performance in relation to habitat in eastern Newfoundland streams

The density, biomass and estimated production of brook trout Salvelinus fontinalis and Atlantic salmon Salmo salar were related to habitat factors in streams of Terra Nova National Park, Newfoundland, Canada. Fish communities at 29 sites (18 brooks; 15 watersheds) were sampled in the summer of 2002, 2003 and 2005. Salmonid density, biomass per unit area and production (derived from biomass and fish size using allometric P:B relationships) were compared with site habitat characteristics (wetted width, lactustrine habitat, per cent riffle habitat, canopy coverage and stream gradient), using an interactive stepwise multiple linear regression. Salmonid biomass (mean: 2·87 g m^?2; range: 0·33–10·88 g m^?2) and estimated production (mean: 3·05 g m^?2 year^?1; range: 0·32–10·98 g m^?2 year^?1) within the study area varied by an order of magnitude, however, habitat variables accounted for much of this variation. Specifically, wetted width and lacustrine area of the tributary played important roles in explaining density, biomass and production. Wetted width was important for all measurements of brook trout and total salmonids while lacustrine area was important for all measurements of Atlantic salmon and played a lesser role in total salmonid biomass. Other factors such as the percentage of riffle habitat, site gradient and canopy coverage provided modest improvements to the fit of some relationships. When models using the same environmental factors were compared, those using production estimates derived from allometric P:B equations in the literature provided improved predictive capability than did those from direct density and biomass estimates. It is proposed that allometric P:B relationships have utility in improving comparisons of stream fish communities, particularly in studies with insufficient resources to measure production directly.     

The wing morphology of limnephilid caddisflies in relation to their habitat preferences

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Fish habitat associations in a spatially variable desert stream

White sands pupfish Cyprinodon tularosa were sampled with minnow traps along the length of Lost River, a highly variable desert stream in New Mexico, to evaluate if their abundance, median standard length ( L _S) and sex ratio values differed by microhabitat variables. Habitat measurements were made in a 4 m² area around the minnow trap. White Sands pupfish populations were primarily structured by L _S. As specific conductance and surface area increased, median size of fish decreased. Shallow areas with higher specific conductance were correlated with an increased number of fish.     

Relationships between life-history strategies of European freshwater fish species and their habitat preferences

1. Focusing on the current environmental characteristics, the ‘habitat template’ theory proposes that life‐history strategies summarise how evolution has shaped species to cope with the temporal and spatial variability of their present environment. The hierarchical ‘landscape filters’ concept predicts that the distribution of species reflects their specific traits that allow them to pass through multiple habitat filters. Together, these theories showed the importance of identifying the functional relationships of species to selective habitat forces in order to predict the organisation and response of communities to the environment. 2. We test the relationships between life‐history traits of European freshwater fish species’ and their habitat preferences, to detect the strategies adopted by fish to cope with their current habitat. For this purpose, we use published data on species traits and habitat preferences (microhabitat hydraulics, temperature and oxygen level). We use multivariate analyses to classify fish species’ strategies and test the relationships between strategies and habitat preferences. 3. We identified a continuum of life‐history patterns between two extremes, with opportunistic and periodic species. Our study supports the idea that microhabitat hydraulics plays a more important role as a template for these species ecological strategies than temperature and oxygen level. Indeed, riffle habitats may select opportunistic species whereas weak relationships are found between species strategies and both their temperature and oxygen level preferences. In addition, the ratio between mortality and growth rate (dimensionless trait), reflecting a trade‐off between growth and survival, varied among species according to the use of their hydraulic habitat, with species using deep habitats exhibiting the highest values. 4. These general relationships between hydraulics and traits may be of importance in community ecology to develop predictive models to understand how fish communities change with the hydraulic environment.     

Sex and age differences in habitat use by invasive cane toads (Rhinella marina) and a native anuran (Cyclorana australis) in the Australian wet–dry tropics

Although generalized habitat use may contribute to the success of invasive taxa, even species that are typically described as habitat generalists exhibit non‐random patterns of habitat use. We measured abiotic and biotic factors in 42 plots (each 100 × 10 m) along a 4.2‐km long unpaved road in tropical Australia, at a site that had been invaded by cane toads (Rhinella marina Bufonidae) seven years previously. We also counted anurans at night in each of these plots on 103 nights during the tropical wet season, over a five‐year period, beginning soon after the initial toad invasion. Spatial distributions differed significantly among adult male toads (n = 1047), adult female toads (n = 1222), juvenile toads (n = 342) and native frogs (Cyclorana australis Hylidae, n = 234). Adult male toads were closely associated with water bodies used as calling and/or spawning sites, whereas adult female toads and native frogs were most commonly encountered in drier forested areas on sloping ground. Juvenile toads used the margins of the floodplain more than conspecific adults did, but the floodplain itself was rarely used. Understanding which components of the habitat are most important to specific age and sex classes within a population, or how invasive species differ from native species in this respect, can clarify issues such as the spatial and temporal location of ecological impact by an invader, and the most effective places for control of the invader with minimal collateral effects on the native biota.     

Changes in movement, range and habitat preferences of adult grayling from late summer to early winter

Radio‐tagged adult grayling Thymallus thymallus ( n  = 22), monitored from mid August to mid December 1999 in the River Kuusinkijoki, Finland, shifted by the end of September (water temperature 10·0–14·5° C) from riffle sites to deeper and slower pool sites 0·7–1·6 km up‐ or downstream. In early winter ( c . 0° C water temperature), eight of 13 fish still under study made a further shift into new pool sites, possibly triggered by ice formation. The summer range of grayling in the riffles was smaller (mean ±  s . d . length: 75 ± 146 m) than the autumn range (99 ± 46 m) in the pools, but gross daily movements were equally short in both the seasons (18 ± 34 m and 15 ± 7 m, respectively). In late summer, adult grayling preferred water depths 80–120 cm and mean velocities >40 cm s⁻¹. In autumn, the preferred ranges were 100–240 cm and <30 cm s⁻¹, respectively. Substratum was mainly boulders in the summer sites, and gravel or pebbles in the autumn sites.     

Feeding ecology and habitat preferences of the catfish genus Trichomycterus in low‐order streams of the Colombian Andes

Six lower order streams in the south‐west of Colombia were sampled on a monthly basis in order to determine the status of Trichomycterus species in relation to their food supply (macroinvertebrates), and physico‐chemical habitat. Fishes were sampled by electrofishing and samples taken for dietary analysis. Macroinvertebrates were collected using a Surber sampler. Trichomycterus spp. populations were present in all streams in habitats ranging from soft to hard substrata and from relatively stagnant waters to fast flowing streams. The average density of the fishes ranged from 0·06 to 1·14 individuals m⁻² with peaks in population corresponding to recruitment of individuals of <1 g. Trichomycterus spp. were found to be benthic carnivores with a diet mostly of aquatic insects. The index of relative importance for the dietary items was 35·0, 10·5, 1·9 and 7·8% for Chironomidae, Trichoptera, Ephemeroptera and Oligochaeta respectively. Combined with physical habitat data, ordinations of fishes and macroinvertebrate data suggested that differences in abundance among sites were driven by stream size and flow regime, indicating dominance of the physical habitat, although a high correlation between Trichomycterus spp. and Chironomidae abundances ( r  = 0·81, P  = 0·049) was also recorded.     

Effects of Predation Risk on Habitat Selection by Water Column Fish, Benthic Fish and Crayfish in Stream Pools

Predation risk can affect habitat selection by water column stream fish and crayfish, but little is known regarding effects of predation risk on habitat selection by benthic fish or assemblages of fish and crayfish. I used comparative studies and manipulative field experiments to determine whether, (1) habitat selection by stream fish and crayfish is affected by predation risk, and (2) benthic fish, water column fish, and crayfish differ in their habitat selection and response to predation risk. Snorkeling was used to observe fish and crayfish in, (1) unmanipulated stream pools with and without large smallmouth bass predators (Micropterus dolomieui >200 mm total length, TL) and (2) manipulated stream pools before and after addition of a single large smallmouth bass, to determine if prey size and presence of large fish predators affected habitat selection. Observations of microhabitat use were compared with microhabitat availability to determine microhabitat selection. Small fish (60–100 mm TL, except darters that were 30–100 mm TL) and crayfish (40–100 mm rostrum to telson length; TL) had significantly reduced densities in pools with large bass, whereas densities of large fish and crayfish (> 100 mm TL) did not differ significantly between pools with and without large bass. Small orangethroat darters (Etheostoma spectabile), northern crayfish (Orconectes virilis), and creek chubs (Semotilus atromaculatus) showed significantly greater densities in pools without large bass. The presence of large smallmouth bass did not significantly affect depths selected by fish and crayfish, except minnows, which were found significantly more often at medium depths when bass were present. Small minnows and large and small crayfish showed the greatest response to additions of bass to stream pools by moving away from bass locations and into shallow water. Small darters and sunfish showed an intermediate response, whereas large minnows showed no significant response to bass additions. Response to predation risk was dependent on prey size and species, with preferred prey, crayfish and small minnows, showing the greatest response. Small benthic fish, such as darters, are intermediate between small water column fish and crayfish and large water column fish in their risk of predation from large smallmouth bass.