Modelling the habitat requirements of invasive Eastern Cottontail (<Emphasis Type="Italic">Sylvilagus floridanus</Emphasis>) introduced to Italy

We analysed the spatial distribution of Eastern Cottontail (Sylvilagus floridanus) and its relationship with the habitat attributes of the agro-ecosystems in north-western Italy. We used generalised linear models to analyse the relationship between the occurrence of the cottontail and a series of landscape-level variables. Hierarchical partitioning was used to estimate the independent contribution of these variables. Our analysis showed that cottontail is typically a lowland species, in that it selected municipalities below 400 m a.s.l. and avoided higher elevations. Cottontails were more likely to occur where the edges of meadows and crop fields were higher. This might indicate the importance of these herbaceous habitats in cottontail feeding behaviour and also the significance of edge vegetation in providing cover. In addition, the extent of the hydrographic network positively affected cottontail presence, probably due to the permanent vegetation cover associated with the banks of rivers, streams and channels of the otherwise intensively cultivated and densely inhabited Po Plain. On the other hand, a prevalence of woodlands, tree plantations and large pastures negatively affected cottontail presence. This is surprising, because these habitats usually encourage cottontail presence in their native range. In general, however, cottontails prefer small woodlots and utilise only the edges of forests, while in Italy forests and pastures are large and typically located in hilly and mountain areas generally avoided by this species. In conclusion, our results confirm that the cottontail is an edge species whose presence is encouraged by crop margins, natural herbaceous habitats and extensive hydrographic networks with the associated riverside vegetation. These characteristics are common in the Po Plain and are likely to facilitate a further expansion of cottontail.     

Habitat overlap between sympatric European hares (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) and Eastern cottontails (<Emphasis Type="Italic">Sylvilagus floridanus</Emphasis>) in northern Italy

In northern Italy, the range of the Eastern cottontail (Sylvilagus floridanus) largely overlaps with that of the native European hare (Lepus europaeus) on the Po Plain. Both species appear to have similar habitat requirements. We studied habitat selection by hares and cottontails during feeding activity from September 2006 to August 2007 in two areas where they occur alone (allopatry) and in one area where they occur together (sympatry). The three areas were basically similar, so that shifts in habitat use observed in sympatry should reflect the response to interspecific competition. Habitat selection was examined at micro- and macro-habitat levels throughout seasons. Habitat breadth of both species followed the change of resource availability through seasons in allopatry as well as in sympatry. No shifts in habitat use were evident at macro-habitat level, even during autumn which was the limiting season. Exploitation of shared habitats by the two species seems to be promoted by differential micro-habitat use within macro-habitat types. Cottontails used woods with dense understory in greater proportion than hares, and their present sites were concentrated within the maximum distance of 20 m of the nearest shelter site. Hares were more likely than cottontails to exploit crops, and their sites were distributed even greater than 80 m away from permanent cover patches. The habitat heterogeneity of agricultural ecosystems within the sympatry range could buffer the negative effects of external factors (climate, human disturbance and predation) on hares, and enhance the chances of exploitation of shared habitats by both species.     

基于生境可获得性的完达山地区马鹿(Cervus elaphus xanthopygus)冬季生境选择

于2004～2005年冬季研究了完达山地区马鹿的生境利用和选择。在野外调查的基础上,获取了研究地区马鹿种群水平上的生境利用数据;利用地理信息系统和遥感技术,从区域尺度上测度了各类生境因子的可获得性。通过比较被利用生境与可获得生境,测度了马鹿冬季对各类生境或生态因子的选择。结果表明,马鹿对植被类型、海拔、坡向、NDVI等级、到公路距离表现出非比例利用,对坡度的利用与其可获得性则没有显著性差异。马鹿选择采伐迹地,低郁闭度生境（第2、3NDVI等级）,200～300m海拔区间,南坡,距离公路600～700m的区间。马鹿采食生境和卧息生境对各类因子具有不同的选择性,表现出不同功能生境分离的特征。对于采食生境,马鹿选择采伐迹地、阔叶疏林,低郁闭度（第2、3NDVI等级）,南坡;对于卧息生境,马鹿仅选择采伐迹地,低郁闭度（第2、3、4NDVI等级）。根据马鹿活动样点的出现与否,建立了马鹿冬季生境选择的逻辑斯谛回归模型。模型回判结果表明,该模型对马鹿活动样方与对照样方的总体正确预测率为74．4％,对马鹿活动样方的正确预测率为84．2％,对对照样方的正确预测率为62．4％,能够较好的预测生境利用概率。     

基于逻辑斯蒂回归模型的鹭科水鸟栖息地适宜性评价

近年来湿地生态系统遭到不同程度破坏,湿地水鸟及其生存空间日益受到威胁。以香港米埔-后海湾湿地为例,收集2003年1月份与鹭科水鸟密切相关的15个自变量和鹭科水鸟实测数据作为因变量构建逻辑斯蒂回归模型,通过筛选获取9个变量因子,分别为土地利用,NDVI,坡度,降雨,TM4纹理,TM3纹理,道路密度,道路距离,人居密度。经Nagelkerke R2检验模型精度达到0.743,拟合度较高。利用模型结果快速聚类,对栖息地进行适宜性分级,分级结果与同期鹭科水鸟实测数据做拟合,精度达到77.4%。最后采集2009年1月份各变量因子数据对回归方程进行时间尺度检验,与同期实测鹭科水鸟数据拟合精度同样达到75.8%,模型具有较好的通用性。     

The modular habitat model (MHM) for the ide, Leuciscus idus (L.) - a new method to predict the suitability of inshore habitats for fish

Groynes are the dominant river engineering structures along the lowland section of large European rivers such as the Rhine, Danube and the Elbe. More than 6000 groynes structure the 400 km stretch of the potamal of the Elbe River. After 1945, destruction of the groynes increased through ice and flood events in the eastern part of Germany. In the past ten years, groyne reconstruction was accompanied by a controversial discussion in the context of the ecological integrity of the Elbe River. With the modular habitat model (MHM) a tool was developed to evaluate the suitability and to balance the availability of fish habitats in groyne fields of different conditions. The morphodynamic module produced a digital terrain model and a spatial model of flow velocity for each groyne field separately. Based on point abundance sampling by electro‐fishing, models of habitat preference were developed for different life history stages by logistic regression. Statistical models predicting the preference of fish‐environment relationships (Leuciscus idus) at different life history stages. The models were discriminated and validated by receiver operating characteristic (ROC) curves. The link between the statistical and the spatial model was realised in the suitability module. The suitability of microhabitats is expressed in classes for each species and life history stage separately. Habitat availability is balanced on the level of mesohabitat, e.g. different types of groyne fields. The temporal dynamics of habitat availability are analysed by considering different levels of discharge. For the stage ‘juvenile A’ and preadult the habitat suitability is better in fields downstream of destroyed groynes. For ‘juvenile B’ and adult stages of the ide, groyne fields in general constitute low habitat suitability. Differences in spatial availability are higher than the differences in temporal habitat availability.     

Habitat selection and segregation by two sympatric lagomorphs: the case of European hares (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) and Eastern cottontails (<Emphasis Type="Italic">Sylvilagus floridanus</Emphasis>) in northern Italy

In northern Italy, the native European hare (Lepus europaeus) and the introduced Eastern cottontail (Sylvilagus floridanus) can occur together at a local scale, as a result of cottontail introduction and expansion into the European hare range. Hare populations are limited in Italy by habitat loss, diseases, and most important by overhunting, and many areas within hare range in northern Italy are undergoing increasing anthropogenic impact. Therefore, quantitative studies on resource selection and exploitation by both species will be of great interest to evaluate the degree of habitat overlap and to search for exploitation competition evidences. We studied habitat selection during resting time by both species in two areas where they occur alone and in one area where they occur together. Habitat selection by the two species was examined at micro- and macro-habitat scales during autumn–winter and spring–summer. Both species selected ecotonal zones between arboriculture stands and crops and between arboriculture stands and spontaneous vegetation (i.e., herbaceous, bush, and woody permanent species), which were the less available in the area of sympatry. No habitat shifts were evident at macro-habitat level because the two species showed a differential micro-habitat use within patches. On the whole, it seems that habitat heterogeneity promoted daytime segregation between the two species. In particular, edges between crops and canopy habitats should be improved, thus reducing chance of intra- and inter-specific encounters.     

Seasonal habitat selection by adult female polar bears in western Hudson Bay

Individual variation in habitat selection has emerged as an important component necessary for understanding population ecology. For threatened species, where habitat loss and alteration affect population trends, understanding habitat use provides insight into mechanisms of population change. Polar bears, Ursus maritimus, in the Western Hudson Bay subpopulation have experienced declines in body condition, survival, and abundance associated with delayed freeze-up and earlier break-up of sea ice due to climate change. Although this subpopulation has been intensively studied, sea ice habitat selection remains poorly understood. We developed a habitat selection model using a mixed conditional logistic regression to determine habitat selection across seasons (freeze-up, early winter, late winter, break-up) and assess individual variation in habitat selection. We used 8487 locations collected between 2004 and 2010 from 64 GPS satellite linked radio-collars on adult females to compare habitat selected to habitat available. Selection changed across seasons and varied the most among individuals during the freeze-up and break-up seasons. During later winter, there was less variation in habitat selection among individuals and bears showed the least amount of selection in habitat use. Distance to the denning area, a core terrestrial refuge habitat, was the top-ranked covariate in all seasons suggesting site fidelity plays a role in habitat selection. Some individual variation may have been due to reproductive status, though we could not account for this directly. Recognizing individual differences, especially in a rapidly changing environment, allows managers to identify critical habitats instead of simply average resources, and may lead to more successful efforts to protect habitats.     

Breeding habitat preferences of the turtledove (<Emphasis Type="Italic">Streptopelia turtur</Emphasis>) in the Dadia-Soufli National Park and its implications for management

Forested areas provide important breeding habitats for the turtledove (Streptopelia turtur) in Dadia-Lefkimi-Soufli National Park, Northeastern Greece. We censused the birds in two forested habitat types using the point-count technique at 60 sites during the breeding season (from mid-April to mid-June) in 2001 and 2002. We sampled vegetation structure at the same sites by measuring horizontal (tree species and density in different size classes) and vertical (percentage canopy closure in dominant, intermediate, suppressed and shrub layer) characteristics within 0.04 ha circular plots centred on the established points. Univariate and multivariate statistical techniques were employed to examine the response of the turtledove′s presence to habitat differences between used and unused sites. The results of this study indicate that habitat structure influence the presence of the turtledove during the breeding season. Middle-aged forest stands particularly those dominated by pine trees with low percentage cover in understory are likely to be beneficial to breeding the turtledove population. A combination of multipurpose forestry operations allowing development of managed woodland in mosaics with other habitat types could provide high-quality habitats for a wide range of wildlife species including game and non-game species in the area. Silvicultural methods of maintaining appropriate breeding habitat for turtledove in Dadia-Lefkimi-Soufli National Park (DLS NP), which are in conflict with commercial forestry, are discussed.     

Linking trade-offs in habitat selection with the occurrence of functional responses for moose living in two nearby study areas

A species may modify its relative habitat use with changing availability, generating functional responses in habitat selection. Functional responses in habitat selection are expected to occur when animals experience trade-offs influencing their habitat selection, but only a few studies to date have explicitly linked functional responses to the underlying trade-offs faced by the animals. We used data from 39 female moose fitted with GPS telemetry collars in two nearby study areas in Canada to investigate if moose (1) were faced with a food/cover trade-off in habitat selection, as typically acknowledged in the literature, and (2) showed a functional response in their use of food/cover-rich habitats. We also examined how habitat selection patterns varied seasonally, and between study areas. The occurrence of functional responses varied strongly between study areas, and could not always be related to a measurable food/cover trade-off. Functional responses were observed more often in the study area where the environmental conditions were more severe (colder temperatures, higher precipitations, and lower food availability). Selection coefficients were also less variable among individuals in that study area, suggesting that severe environmental conditions may constrain individuals to a few selection tactics and promote the development of functional responses. Moose reacted to the availability of different habitat types in different seasons, reflecting the changing trade-offs faced by the animals. We found considerable behavioral differences between individuals from two adjacent study areas, and therefore recommend caution when extrapolating habitat selection results. We advocate for the wider use of functional responses to identify critical habitats for a species from a management or conservation perspective.     

Breeding population size and trends of American Oystercatchers on small islands of Bahía Santa María‐La Reforma,Sinaloa, Mexico

The islands of Bahía Santa María‐La Reforma, Sinaloa, Mexico, host the largest breeding population of the western race of American Oystercatchers (Haematopus palliatus frazari). This resident shorebird has a small breeding range restricted to northwestern Mexico and, although listed as endangered, little is known about their breeding biology. We estimated the number of pairs on the El Rancho and Melendres islands, the detection rate of pairs in different habitats, and the relationship between habitat length and number of pairs during three breeding seasons (2016–2018). In 2016 and 2017, the number of pairs peaked in mid‐April (97 and 95 pairs, respectively) at El Rancho, and in early May and early April (50 and 42 pairs, respectively) at Melendres. In 2018, both islands had the maximum number of pairs during mid‐May, with 109 pairs at El Rancho and 42 at Melendres. Detectability of breeding pairs in plots with sandy beach and dune habitats was higher (86–100%) than in those with mangrove habitat (22%). Detectability was associated with habitat type and should be considered in estimating the population size of this subspecies. We estimated that ~ 11% of the total frazari American Oystercatcher population breeds on these two small islands. The density of breeding pairs varied between habitats (range = 0–13 pairs/km). We also found a positive relationship between the number of pairs and plot length, suggesting that habitat availability might be a limiting factor for populations of American Oystercatchers in Mexico.     

Functional responses in polar bear habitat selection

Habitat selection may occur in situations in which animals experience a trade-off, e.g. between the use of habitats with abundant forage and the use of safer retreat habitats with little forage. Such trade-offs may yield relative habitat use conditional on the relative availability of the different habitat types, as proportional use of foraging habitat may exceed proportional availability when foraging habitat is scarce, but be less than availability when foraging habitat is abundant. Hence, trade-offs in habitat use may result in functional responses in habitat use (i.e. change in relative use with changing availability). We used logistic and log-linear models to model functional responses in female polar bear habitat use based on satellite telemetry data from two contiguous populations; one near shore inhabiting sea ice within fjords, and one inhabiting pelagic drift ice. Open ice, near the ice edge, is a highly dynamic habitat hypothesised to be important polar bear habitat due to high prey availability. In open ice-polar bears may experience a high energetic cost of movements and risk drifting away from the main ice field (i.e. trade off between feeding and energy saving or safety). If polar bears were constrained by ice dynamics we therefore predicted use of retreat habitats with greater ice coverage relative to habitats used for hunting. The polar bears demonstrated season and population specific functional responses in habitat use, likely reflecting seasonal and regional variation in use of retreat and foraging habitats. We suggest that in seasons with functional responses in habitat use, polar bear space use and population distribution may not be a mere reflection of prey availability but rather reflect the alternate allocation of time in hunting and retreat habitats.     

Determinants of the distribution of juvenile fish in the littoral area of a shallow lake

1. Research has often focused on the pelagic areas of lakes; the littoral zone has received less attention. The few studies concerning fish distribution in littoral habitats have concentrated on stands of submersed macrophytes, whereas other littoral habitat types have seldom been investigated. 2. This study aimed to predict the occurrence of juvenile fish in several littoral habitats of a shallow lake as a function of food availability, complexity of habitat structure, water depth and substrate. Habitats comprising reed, woody structures, and two open water areas differing in depth were sampled for fish and invertebrate biomasses on two shores, over 6 months and during both daylight and at night. 3. The juvenile fish community consisted almost exclusively of 0+ and 1+ roach and perch. There was a strong diel component in habitat use, with a predominant occurrence of fish in complex habitats (mainly woody structures) during the day, and a partial migration towards the open habitats at night, more strongly expressed in roach than in perch. 4. The diet of all fish groups was relatively constant over the seasonal cycle, and was independent of habitat. There was a higher degree of planktivory in roach than in perch, but both species fed on benthic macroinvertebrates to a substantial extent. 5. According to a logistic regression model, the biomass of potential food organisms in the different habitats had little predictive effect on the spatial distribution of the fish, whereas the structural complexity of the habitats combined with the diel cycle explained about 28% of the occurrence patterns in 0+ and 1+ perch and 1+ roach.     

Modelling habitat use of Tetrao urogallus L. in Austria for conservation issues

Loss and deterioration of habitats are major threats for Tetrao urogallus in central Europe, where forests are highly fragmented and forest practices have distinctly changed during the last decades. Habitat models are important tools for conservation planning, often relying on presence–absence data. We mapped indirect signs of Tetrao urogallus presence as well as habitat variables over a series of seven study areas in the Austrian Alps, situated on limestone and on silicate rock. We modelled habitat use of Tetrao urogallus with one parametric approach (binary logistic regression) and two machine learning classification algorithms (classification trees and random forests) for both geological substrata separately. All three modelling approaches performed equally well in terms of accuracy or predictive power, but differed in model calibration. Three variables significantly contributed to all three habitat models on limestone and on silicate substrate, respectively, i.e. the cover of field-layer, the cover of dwarf shrubs and the proportion of deciduous trees in forest stands on limestone and the cover of field-layer, the canopy cover and the occurrence of Abies alba and/or Pinus sylvestris in forest stands on silicate rock. Some variables like the cover of Rubus sp. appeared in several models, which are not frequently mentioned in other studies. There have been some explanatory variables, which would have been missed, when applying just one single modelling approach, for example the occurrence of forest edges, the availability of canopy gaps and the supply of ant hills. Our results suggest differing habitat management strategies on limestone and on silicate rock. Considering the large spatial requirements of Tetrao urogallus the necessity of active habitat management for Tetrao urogallus becomes obvious.     

Effects of arboriculture stands on European hare <Emphasis Type="Italic">Lepus europaeus</Emphasis> spring habitat use in an agricultural area of northern Italy

Habitat changes due to agricultural intensification is widely considered a main cause of European hare (Lepus europaeus Pallas, 1778) decline. We investigated the potential of arboriculture stands to enhance landscape diversity and increase farmland suitability for European hares in an intensive agricultural area of northern Italy. In spring 2005, we recorded hare habitat use during feeding activity and resting time by nocturnal censuses and searching for daytime resting sites, respectively. Hare presence/absence, based on faecal pellets, was assessed in 150 1-m radius plots. Hares positively selected edges and avoided woods and stubble during both feeding activity and resting time, which highlights the key role of permanent linear cover in providing the variety of vegetation types required by hares for shelter and feed. Forms were typically located in covered places, surrounded by denser vegetation than sample plots, in order to gain protection from avian and terrestrial predators. Arboriculture stands seem to be able to satisfy a part of hare habitat requirement, thanks to ground flora that provide tasty food, and tree cover that offers refuge against predators and bad weather conditions. However, more focused studies are necessary to improve knowledge of the long-term effects of these crops on farmland biodiversity.     

An appraisal of the fitness consequences of forest disturbance for wildlife using habitat selection theory

Isodar theory can help to unveil the fitness consequences of habitat disturbance for wildlife through an evaluation of adaptive habitat selection using patterns of animal abundance in adjacent habitats. By incorporating measures of disturbance intensity or variations in resource availability into fitness-density functions, we can evaluate the functional form of isodars expected under different disturbance-fitness relationships. Using this framework, we investigated how a gradient of forest harvesting disturbance and differences in resource availability influenced habitat quality for snowshoe hares (Lepus americanus) and red-backed voles (Myodes gapperi) using pairs of logged and uncut boreal forest. Isodars for both species had positive intercepts, indicating reductions to maximum potential fitness in logged stands. Habitat selection by hares depended on both conspecific density and differences in canopy cover between harvested and uncut stands. Fitness-density curves for hares in logged stands were predicted to shift from diverging to converging with those in uncut forest across a gradient of high to low disturbance intensity. Selection for uncut forests thus became less pronounced with increasing population size at low levels of logging disturbance. Voles responded to differences in moss cover between habitats which reflected moisture availability. Lower moss cover in harvested stands either reduced maximum potential fitness or increased the relative rate of decline in fitness with density. Differences in vole densities between harvested and uncut stands were predicted, however, to diminish as populations increased. Our findings underscore the importance of accounting for density-dependent behaviors when evaluating how changing habitat conditions influence animal distribution.     

Daytime habitat selection by introduced eastern cottontail Sylvilagus floridanus and native european hare Lepus europaeus in Northern Italy

We used radiotelemetry to investigate resting sites habitat selection by introduced eastern cottontail (Sylvilagus floridanus) and native European hare (Lepus europaeus) under sympatric conditions. We tracked 24 hares and 34 cottontails in a protected area of northwestern Italy. Hares were found in different sites every week, while cottontails used the same site for two weeks, and occasionally for longer. It is supposed that this periodic nest switching reduces the risk of predation and parasitism. Hares and cottontails forms were located in different habitats and characterized by dense vegetation cover near the ground. This cover increased from winter to summer in both species, while in autumn it continued to increase in cottontails only, and decreased in hares. Cottontails selected shrubby habitats near the river, and avoided crop fields in all seasons. Hares were more adaptive in their search, using high herbs and shrubs all year round, wheat fields in spring, maize in spring and summer, and stubbles in winter. Arguably, partial niche differentiation is necessary to allow the coexistence of similar species. In our study area, hares and cottontails differentiated in the use of resting sites habitats, presumably so as not to compete in this part of their ecological niche.     

Habitat associations of wild goat in central Iran: implications for conservation

Wild goat (Capra aegagrus) is one of the highly valued but threatened ungulates of Iran. Seasonal habitat use of wild goat was studied from October 2006 to September 2008 in Haftad Gholleh Protected Area, central Iran. We developed averaged logistic regression models based on Akaike Information Criterion weights for each season. The obtained habitat suitability models showed high sensitivity (greater than 88%) for all evaluation datasets. Wild goat habitat use was positively related with steep slopes, areas near rocky substrates and water sources, west-facing slopes and areas far from roads in all seasons. Core zones of protected area covered nearly 70% of suitable habitats for wild goats, predicted by logistic regression models. Northern core zone covered more than 61% of predicted suitable habitats, which should receive more attention in management actions. The southern core zone boundaries should be considered to increase the encompassed suitable habitats. There was a substantial overlap between seasonal suitable habitats with the highest overlap observed between spring and summer and summer and fall.     

Integrating individual habitat choices and regional distribution of a biodiversity indicator and top predator

Aim Habitat selection studies have mainly focused on behavioural choices of individuals or on the habitat‐related regional distribution of a population, with little integration of the two approaches. This is despite the fact that traditional biogeography theory sees the geographical distribution of a species as the collective outcome of the adaptive habitat choices of individuals. Here, we integrate individual habitat choices with regional distribution through a bottom‐up Geographical Information System (GIS)‐based approach, by using a 9‐year data set on a large avian predator, the eagle owl (Bubo bubo L.). We further examine the potential population level and biodiversity consequences of this approach. Location The study was conducted in the Trento Region (central‐eastern Italian Alps) and in six other areas of the nearby Lombardia Region in the central Alps. Methods We used stepwise logistic regression to build a habitat suitability model discriminating between eagle owl territories and an equal number of random locations. The model was applied to the whole Trento region by means of a GIS so as to predict suitable habitat patches. The predicted regional distribution (presence–absence in 10‐km grid quadrats) was then compared with the observed one. Furthermore, we compared estimates of biodiversity in quadrats with and without eagle owls, so as to test whether the presence of this top predator may signal macro‐areas of high biodiversity. Results The logistic habitat suitability model showed that, compared with a random distribution, eagle owls selected low‐elevation breeding sites with high availability of prey‐rich habitats in their surroundings. Breeding performance increased with the availability of prey‐rich habitats, confirming the adaptiveness of the detected habitat choices. We applied the habitat suitability model to the 6200 km² study region by means of a GIS and found a close fit between the observed and predicted regional distribution. Furthermore, population abundance was positively related to the availability of habitat defined as suitable by the above analyses. Finally, high biodiversity levels were associated with owl presence and with the amount of suitable owl habitat, demonstrating that modelling habitat suitability of a properly chosen indicator species may provide key conservation information at the wider ecosystem level. Main conclusions Our bottom‐up modelling approach may increase the conservation‐value of habitat selection models, by (1) predicting local and regional distribution, (2) estimating regional population size, (3) stimulating further hypothesis testing, (4) forecasting the population effects of future habitat loss and degradation and (5) aiding in the identification and prioritization of high‐biodiversity areas.     

Summer habitat relationships of barbels in south‐west Spain

An analysis was made of the associations with local habitat features of barbels ( Barbus sp.) of a Mediterranean river basin. The analysis was based on the presence data from sampling the upper, middle, and lower reaches of 31 rivers in the middle Guadiana River basin (south‐west Spain). Numerous local habitat variables were determined, including the river's size and substratum, physicochemical variables of water, and the aquatic and riparian vegetation. For each species, a univariate analysis was performed using preference indices, and logistic regression was used to construct a parsimonious multivariate model and Gaussian response models with the most influential variables, quantifying the species' limits of tolerance. Distinct habitat associations for every species were obtained, mainly relating Barbus comiza to the larger habitats and higher water levels, Barbus microcephalus to the maintenance of lotic conditions and Barbus sclateri to more fluctuating rivers. Barbus steindachneri showed a different habitat relationship from that of the genetically almost identical B. comiza . Cover played a significant role in all but B. comiza .     

Ephemeral floodplain habitats provide best growth conditions for juvenile Chinook salmon in a California river

We reared juvenile Chinook salmon for two consecutive flood seasons within various habitats of the Cosumnes River and its floodplain to compare fish growth in river and floodplain habitats. Fish were placed in enclosures during times when wild salmon would naturally be rearing in floodplain habitats. We found significant differences in growth rates between salmon reared in floodplain and river enclosures. Salmon reared in seasonally inundated habitats with annual terrestrial vegetation experienced higher growth rates than those reared in a perennial pond on the floodplain. Growth of fish in the non-tidal river upstream of the floodplain varied with flow in the river. When flows were high, there was little growth and high mortality, but when the flows were low and clear, the fish grew rapidly. Fish displayed very poor growth in tidally influenced river habitat below the floodplain, a habitat type to which juveniles are commonly displaced during high flow events due to a lack of channel complexity in the main-stem river. Overall, ephemeral floodplain habitats supported higher growth rates for juvenile Chinook salmon than more permanent habitats in either the floodplain or river. Variable responses in both growth and mortality, however, indicate the importance of providing habitat complexity for juvenile salmon in floodplain reaches of streams, so fish can find optimal places for rearing under different flow conditions.