Foothill Stream Research Articles

О ДИСТАНЦИОННОМ ОПРЕДЕЛЕНИИ ОСНОВНЫХ ХАРАКТЕРИСТИК ЗАВАЛЬНЫХ ВОДОЕМОВ

In the channels of mountain and foothill streams, as a result of landslides (collapses) of coastal slopes, litter soil dams are often formed, blocking the watercourse channel. On the upper side of them, water masses accumulate, the over flow of which through the dam can lead to the destruction of the latter and the emergence of a catastrophic breakthrough mudfl ow that threatens the safety of life of the lower territories. In these conditions, it is important to quickly assess the extent of the risk, taking into account the existing hydrogeomorphological characteristics of the channel reservoir. The paper obtains calculated dependencies for the analytical finding of the necessary characteristics of the (full, partially fi lled) flood reservoir, as well as the values of the reserve volume and time of fi lling the reservoir, based on remotely determined parameters of individual points located on the dam and the adjacent channel of the watercourse.

Diversity and succession of riparian plant communities along riverbanks bioengineered for erosion control: a case study in the foothills of the Alps and the Jura Mountains

Soil bioengineering for riverbank stabilization involves the use of living plant materials to treat unstable or eroding riverbanks. These near-natural structures may harbor a higher plant richness and vegetation cover compared to classical civil engineering structures such as ripraps, but little information exists on vegetation dynamics during secondary succession on stabilized riverbanks. We hypothesized that soil bioengineering, by means of active introduction of early successional Salix shrubs, can foster successional trajectories of riparian plant communities, unlike civil engineering. We sampled three types of riverbank stabilization structures: pure bioengineering structures, mixed structures (combining riprap and bioengineering techniques) and ripraps, across a 14-year sequence on 42 sites located along 23 different streams running through the foothills of the Alps and the Jura Mountains (France and Switzerland). We quantified species richness and density and compared the temporal patterns of four groups of species that normally appear sequentially in natural succession on riverbanks (ruderal, hygrophilous, shade-tolerant, competitive species), as well as non-native species. Plant community composition differed greatly between ripraps and the two types of bioengineered sites, and ligneous species typical of advanced successional stages (Cornus sanguinea, Corylus avellana) spontaneously established in the oldest bioengineered sites. In general, richness of total species was higher in stabilization structures using soil bioengineering (including mixed structures) than in riprapped sites. In particular, the number of shade-tolerant and competitive species in bioengineered sites was double that found at ripraps after 14 years. Yet, richness of shade-tolerant species increased over time only on purely bioengineered sites, and their density there was almost twice that in mixed structures. Neither the type of stabilization structure nor time explained the variability in richness and density of non-native species across sites. Our study showed that along streams running through foothills, where erosion processes are usually intense, vegetation of bioengineered riverbanks exhibits successional dynamics similar to those theoretically found in natural conditions. Bioengineering can therefore foster ecological processes while stabilizing eroding riverbanks along foothill streams, thus satisfying human needs for infrastructure protection with less impact on the riparian ecosystem than riprap structures.

The distributional pattern of benthic macroinvertebrates in a spring-fed foothill tributary of the Ganga River, western Himalaya, India

Benthic macroinvertebrates play important ecosystem roles in the cycling and outflow of nutrients. The benthos transforms organic detritus from sedimentary storage into dissolved nutrients that can be mixed into overlying waters and used by rooted plants (macrophytes) and algae (phytoplankton) to enhance primary productivity. This study examined the distribution pattern of benthic macroinvertebrates in a lesser Himalayan foothill stream from the headwaters (2,200m) to mouth (375m). Five stations (S1 to S5) were established along the 43-km course of the stream. Samples were collected at bi-monthly intervals from January to December 2009. The total density of the benthic macroinvertebrate community increased with decreasing altitude and differed significantly among stations. Dominant orders were Diptera at S1 (Simulidae, 27%) & S5 (Chironomidae 24%), Trichoptera at S2 (Limnephilidae 16%) & S3 (Hydropsychidae 9.9%), and Ephemeroptera (Heptageniidae 9.2%) at S4. Principal component analysis revealed that the characteristic taxa were Simulidae at S1, Limnephildae at S2, Hydropsychiidae, Rhyacophilidae, Tipulidae, Perlodidae, Dryopidae & Notonectidae at S3, Heptageniidae at S4, and Chironomidae, Siphlonuridae, & Agrionidae at S5. Cluster analysis showed one large cluster comprising S1 and S2 as sub-groups with resemblance to S3-S4, and S5 as an outlier. The similarity between the stations S3-S4 was attributed to similar land-use pattern (agriculture) and stream order (II Order), while S1 and S2 were slightly similar due to partial similar forest type (oak forest at S1, pine-oak forest at S2) and stream order. At S5, however, the considerable change in forest type (mixed forest) land-use and stream order (III Order) caused S5 as an outlier in cluster. The variations in the abundant and characteristics taxon at different stations were attributed to change in substratum and land-use patterns. 

Periphyton Community Structure of the Spring-fed Foot-hill Stream Tamsa Nadi from Doon Valley, Uttarakhand, India

Periphyton Community Structure of the Spring-fed Foot-hill Stream Tamsa Nadi from Doon Valley, Uttarakhand, India

Check dams decrease the channel complexity of intermediate reaches in the Western Carpathians (Czech Republic)

Check dams can modify local channel and sedimentological characteristics through sediment deposition in upstream sedimentary wedges and scour processes downstream of individual check dams. However, research focusing on the channel reaches between subsequent check dams (referred to here as intermediate reaches) is limited. We evaluated channel complexity and its selected dimensions (longitudinal and cross-section heterogeneity, sediment characteristics and the presence of instream wood) in 30-m long intermediate reaches (n = 10) between subsequent check dams in comparison with channel reaches that were not treated with check dams (n = 10) in both a stepped-bed stream in a steep confined valley and an originally pool-riffle stream in an unconfined foothill valley. Check dams altered the channel complexity of intermediate reaches when compared with reaches of undisturbed streams. However, in contrast to foothills streams, check dams did not heavily affect longitudinal or cross-sectional heterogeneity of the intermediate reaches in the steep streams. Despite an increase in sediment homogeneity in steep reaches treated with check dams, the presence of coarse bed sediments helped to preserve their stepped-bed morphology. In contrast, the longitudinal profile of the treated foothill stream completely lost its vertical oscillations because of the transformation of pool-riffles to a uniform plane bed morphology. Similarly, cross-sectional heterogeneity in the foothill stream was degraded in comparison with those of untreated reaches. We did not observe differences in instream wood abundance between treated and untreated streams.

Concrete slab ford crossing – An anthropogenic factor modifying aquatic invertebrate communities

Unimproved fords provide an easy and inexpensive method of stream crossing. However, vehicles compact the stream bottom and flatten the banks. One simple and relatively permanent solution to this problem is the use of concrete slabs, which can hinder the movement of fish and invertebrates, especially in the presence of low water levels. Although the impact of fords on the stream invertebrate fauna seems clear, there is little available data on this topic, as most reports instead focus on water quality. The impact of a concrete slab ford on the invertebrate fauna of a foothill stream was examined which led to the hypothesis that the benthic invertebrates inhabiting the ford and stream sections immediately upstream and downstream of the crossing would differ significantly from those at a non-transformed natural site. Results revealed that the invertebrate fauna in the vicinity of the ford was altered over relatively long stream sections. The ford disrupted the natural balance between deposition and erosion, with the former dominating above the ford and the latter dominating below the crossing. In small streams, where there are often several similar crossings, this effect would likely be multiplied. The ford's interference in the stream's natural balance between deposition and erosion caused a change in the grain size of the substrate and altered the available organic matter, which directly affected the qualitative and quantitative composition of the macrozoobenthos. As the habitat becomes more homogeneous, the community of invertebrates becomes less diverse. Our results can support management decisions for erosion control.

Effects of the hydrological cycle on the phycoperiphyton assemblage in an Andean foothill stream in Colombia

The Guarinó River is a torrential system that is located in the foothills of the Colombian central Andean mountains that naturally experiences severe hydrological disturbances, which were higher during the Niño-Niña/Southern Oscillation (ENSO) between 2007 and 2010. The seasonal and interannual variabilities in the taxonomic composition, richness and density of phycoperiphyton assemblages (ecological descriptors) from the Guarinó River were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle between 2007 and 2010. The values of the ecological descriptors and environmental variables were analysed via ANOVA, ANCOVA and Canonical Discriminant Analysis to establish temporal patterns and relationships between the variables. Eighty-seven taxa belonging to Cyanobacteria, Chlorophyta, Charophyta, Ochrophyta, Cryptophyta, Euglenozoa and Dinophyta were identified. Flow, water temperature and dissolved oxygen corresponded with the hydroclimatic variation and allowed for the differentiation of the El Niño and La Niña periods. Phycoperiphyton density differences matched the environmental variation pattern with a significant annual increase in the number of individuals during El Niño, whereas annual differences related to richness were not evident. The replacement of genera according to their drag or desiccation tolerance and the persistence of genera tolerant to high hydrological disturbances, such as <em>Fragilaria, Nitzschia, Gomphonema, Navicula </em>and especially<em> Lyngbya</em>, was observed.

The role of the hydrological cycle on the temporal patterns of macroinvertebrate assemblages in an Andean foothill stream in Colombia

The seasonal and interannual changes in the structure, composition and functional feeding groups of the macroinvertebrate assemblage of the Guarinó River, a torrential system located in the Colombian Andean foothills, were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle and the El Niño-Niña/Southern Oscillation (ENSO) between 2007 and 2010. Benthic samples were collected at three sites in the lower sections of the river. A total of 127 taxa were collected in the study, with the total taxonomic richness per site ranging from 82 to 96 taxa and benthos density averaging 5.41 ind. m<sup>-2</sup>. The density showed a tendency to decrease in periods of maximum river level and flow, particularly during La Niña phenomena, and to increase in dry periods, especially in the third year (2009-2010) during El Niño phenomena. The presence and abundance of taxa, functional feeding groups and life habits were regulated by environmental parameters associated with hydrological variability, derived of ENSO phenomena, especially flow rate values. The assemblage showed high taxonomic and functional diversity, which is characteristic of ecosystems affected by recurrent hydrological disturbances, exhibiting differentiated responses based on adaptive strategies against the local hydrologic regime that allow fast recovery under conditions like ENSO phenomena. Such responses include composition changes according to adaptations to different hydrological scenarios, the predominance of generalist trophic guilds and taxa with plasticity in their habits and range of environmental tolerance.

Reference conditions for fish microhabitat use in foothill streams: A case study on undisrupted carpathian streams

ABSTRACTFoothill rivers characterized by a relatively high slope are frequently used for hydropower purposes or are highly regulated. These river sections are inhabited by many rheophilic species that are endangered by habitat degradation. Restoration/rehabilitation projects and fishway constructions could increase species favourable status, but relevant ecological requirements for several fish species are missing. We present a first insight into a complex microhabitat use of all species (excluding rare species) occurring within the model foothill stream and provide a comprehensive view on the most important microhabitat variables that influence the distribution of fish species within the model area. For two species, Balkan spined loach (Sabanejewia balcanica) and Carpathian barbel (Barbus carpathicus), we present the first description of such microhabitat use. The model we present (canonical correspondence analysis) significantly explains 64.5% (p < 0.01) of the variability, where water depth more than 40 cm, refuge stones and microhabitats in the bank area are the most influential microhabitat variables. Moreover, three species groups are apparent from the graphical expression of our proposed model, where species from the upper sites form the first group, young‐of‐the‐year, Balkan spined loach and common minnow (Phoxinus phoxinus) form the second group and abundant species inhabiting foothill river sections form the third group. In general, we assume that the preferences of a species for a given microhabitat are not only a function of, e.g. environmental variables or species length frequencies, but also strongly depend on the co‐occurring species. Copyright © 2010 John Wiley & Sons, Ltd.

The ciliate fauna of an unpolluted German foothill stream, the breitenbach, 2: Quantitative aspects of the ciliates (ciliophora; protozoa) in fine sediments

Summary Ciliata in sandy bedsediments of the Breitenbach were studied quantitatively. The Breitenbach is an unpolluted foothill stream in Hesse, Germany, which runs through an area of fine-grained sandstone. The stream lacks a porous, continuously oxygenated, hyporheic zone. Sediment cores were collected at monthly intervals, from September 1990 to August 1991, at four sites along the stream, to depths of 10 cm. They were subdivided into 2 cm layers, and live Ciliata were counted directly in diluted samples. Their abundance varied greatly, the observed maximum being about 4000/ml sediment in March 1991. There was no longitudinal gradient of ciliate abundance, and it showed no clear seasonal pattern at one site; but at the other three sites it peaked in spring and early summer. At two sites, bacterivorous Ciliata were normally dominant, but peak abundances resulted from increased numbers of herbivorous species. Depth distribution of Ciliata peaked in the 0–2 cm sediment layer. Some so-called sapropelic taxa (genera Metopus, Brachonella and Caenomorpha ) were normally observed only below 2 cm depth; but during periods of low discharge they also occurred in the top layer of sediment. Biomass was up to 170 μg wet weight/ml sediment. Small ciliata (

Ecosystem Engineering by a Dominant Detritivore in a Diverse Tropical Stream

Prochilodus mariae (Characiformes: Prochilodontidae) is a detritivorous fish distributed throughout the Orinoco river basin of South America. Spectacular migrations of these fishes occur at the end of the rainy season into the Andean foothills. Prochilodus ingest large quantities of sediments and may thereby modify habitats in neotropical streams. The major objectives of this study were (1) to explore experimentally the importance of Prochilodus in structuring a tropical stream in the Venezuelan Andean piedmont, and (2) to determine whether there was sufficient ecological redundancy in a diverse and abundant assemblage of epibenthic fishes to compensate for the removal of Prochilodus. Community structure was compared among three experimental treatments: (1) Prochilodus exclusion, (2) Prochilodus enclosure, and (3) the natural fish assemblage. Selective exclusion of Prochilodus resulted in striking changes in community structure as measured by patterns of sediment accrual and the composition of algal and invertebrate assemblages. Highly significant increases in total dry mass and in ash—free dry mass of sediments accruing on stream—bottom substrates were observed almost immediately following the exclusion of Prochilodus. Moreover, the composition of algal and invertebrate assemblages was significantly modified by Prochilodus. Taxa such as diatoms were reduced in number when Prochilodus was present; in contrast, Prochilodus appeared to facilitate nitrogen—fixing cyanobacteria. Total invertebrate densities were greatest in the Prochilodus removal treatment; however, a variety of responses to the experimental treatments was observed among different taxa analyzed individually, including density reductions, increases, and no measurable effects. This study suggests that the detritivore Prochilodus is a functionally dominant species in Andean foothill streams via sediment—processing activities. Moreover, it provides little evidence to support the notion that strongly interacting species are limited to simple systems with few food web components.

Biology of the cardinalfishGlossamia gjellerupi (Perciformes: Apogonidae) from the Sepik-Ramu River basin, Papua New Guinea

Glossamia gjellerupi forms a considerable part of the fish biomass (25%) and density (12%) in floodplain margin streams and lower foothill streams throughout the Sepik-Ramu basin where it occurs up to an altitude of 320 meters above sea level. It prefers habitats with slow flow rates: pools, alongside banks, under cover of vegetation, etc. Biomass and density decreased with increasing current speeds. Condition factor and fat deposits were negatively correlated to current speeds, with populations from floodplain margin streams having the highest averages for both these indices. Fluctuations in population size appeared to be related to the irregular occurrence of spates. No seasonality in reproduction, condition and fat deposits were noted although peaks occurred according to specific local conditions. Fecundity was found to be low, increasing with fish size. Eggs in a ripe ovary were all in the same stage of development, with sizes of around 3.3 mm.G. gjellerupi is a male mouth brooder. Mouth-breeding may restrict the species to well oxygenated waters. Reproductive activity takes place throughout the year but is not random since clear peaks in gonad development occurred within different populations. Reproductive activity and/or survival rate of juveniles are possibly directly related to floods. Prolonged periods of environmental stability, such as those occurring in periods of less rainfall, seem to be conditional for the survival of juveniles. Fish up to 30 mm length fed predominantly on small benthic insect larvae. Fish larger than 60 mm are carnivorous top-predators feeding predominantly on crabs, bottom dwelling fish and large terrestrial insects. Fish of all sizes, except the largest, fed on caridinid prawns. Feeding habits varied between different habitats depending on local environmental conditions.

Short-Term Colonization of Rough and Smooth Tiles by Benthic Macroinvertebrates and Algae (Chlorophyll a) in Two Streams

We examined the importance of substratum texture and the colonization dynamics of stream macroinvertebrates and algae (measured as chlorophyll a) using artificial substrata and two sampling designs in two ecologically different streams. Rough and smooth clay tiles were used in two short-term colonization studies, which were conducted in a 2nd-order Rocky Mountain foothill stream and a 2nd-order stream in the boreal mixed woodland of Alberta, Canada. At both streams, two sampling designs were used concurrently: (1) simultaneous placement and sequential removal of substrata, and (2) sequential placement and simultaneous removal of substrata. Three hypotheses were tested: there was no difference in the density of macroinvertebrates or quantity of chlorophyll a (1) on rough and smooth tiles, (2) for different colonization periods (1-14 d), and (3) for both sampling designs. Density of most macroinvertebrates and the quantity of chlorophyll a was greater on the rough tiles in both sampling designs and in both streams. Both sampling designs gave consistent results for the effect of texture for most taxa over eight colonization periods. Similar results for the sampling designs and in both streams provide strong evidence for the importance of substratum texture in streams. Some macroinvertebrate colonization patterns indicated early and late colonizers, while other patterns indicated no colonization trend. Several taxa showed similar trends in colonization to the quantity of chlorophyll a on the tiles. But after 1-4 d, when there was little chlorophyll a on the tiles (mean chlorophyll a < 0.1 μg/cm²), density of total number of organisms and most taxa was greater on rough tiles than on smooth tiles in both sampling designs. In contrast to most macroinvertebrates, Epeorus (Ephemeroptera: Heptageniidae) nymphs were more abundant on smooth tiles than on rough tiles.

Growth and production of filter‐feeding caddis fly (Trichoptera) larvae in a foothill stream in the Soviet far East

The paper deals with some aspects of larval biology in three species of filter‐feeding caddis flies: Stenopsyche marmorata, Arctopsychepalpata and Hydropsyche orientalis inhabiting the foothill river Kedrovaya (Southern Primorye, The Soviet Far East). Data are given on calorific value of wet and dry matter of the various stages. Parameters in equations of dependence of the absolute growth rate upon body weight and size are calculated. Production of larval populations and annual P/B‐coefficients were estimated. Taking into account the calorific value of larval dry matter and ratio of dry/wet weight, the annual production was equal to 56.14 kJ.m‐2 DM for S. marmorata 29.73 kj.m‐2 DM for A. palpata and 9.57 kJ.m‐2 DM for H. orientalis. The annual P/B‐coefficients for the three populations were 2.0,3.6 and 5.8, respectively.

Diel periodicity in density of Ephemeroptera nymphs on stream substrata and the relationship with drift and selected abiotic factors

The diel periodicity in density of Ephemeroptera nymphs on an undisturbed stream bottom was documented by direct observation. The study was conducted in a second-order Rocky Mountain foothill stream in Alberta. Observations were made for 24-h periods, twice during a new moon and twice during a full moon; the times of the dark and light periods were noted. Nocturnal observations were made using a red light. The abundance of drifting nymphs, incident light, percent cloud cover in the sky, and water temperature were recorded to determine if they were related to the observed diel periodicity on top of the substratum. The taxonomic groups of Ephemeroptera nymphs examined were Cinygmula, Heptageniidae (Cinygmula and Epeorus), Baetis, Baetis–Ameletus, Ameletus, Drunella coloradensis Dodds, and total fauna (all groups including minor taxa). In response to the artificial light used for observations, total fauna, Cinygmula, and Baetis nymphs were not affected by the light, and the nymphs were not found to be negatively phototactic. Total fauna and Heptageniidae nymphs exhibited a diel periodicity between 24-h periods; the Baetis–Ameletus group also had a diel periodicity. Cinygmula, Baetis, and D. coloradensis nymphs did not exhibit a diel periodicity. Most taxonomic groups were at greater densities on the top of the substratum in the dark period than in the light period. For small and large size classes of nymphs examined, only the small Heptageniidae and Baetis–Ameletus nymphs showed a diel periodicity in density. Drift of the common groups of nymphs was aperiodic and not statistically correlated with the diel density of nymphs on the substratum. In general, incident light, percent cloud cover, and water temperature were not correlated with the diel density of the taxonomic groups on the top of the substratum.

Alterations in periphyton characteristics due to grazing in a Cascade foothill stream

SUMMARY 1. In situ experiments were conducted in a Washington stream to quantify the effects of grazing by a caddisfly larva, Dicosmoecus gilvipes (Trichoptera: Limnephilidae), and a mayfly nymph, Nixe rosea (Ephemeroptera: Heptageniidae) on periphyton biomass, structure, and function.2. Dicosmoecus gilvipes reduced periphyton biomass from 92 mg m−2(as mean chlorophyll a) to 33 mg m−2. The grazed assemblage was less diverse and composed of smaller, closely attached diatoms, whereas there was a higher proportion of overstorey and filamenttius algae in the diverse, ungrazed periphyton.3. By maintaining the periphyton community as a thin layer of diatoms, grazing by D. gilvipes appeared to promote a healthier, more vigorous community relative to the ungrazed mat, which became senescent in the latter part of the experiment.4. Nixe rosea had little measurable effect on any characteristics of the periphyton measured. These nymphs apparently preferred small diatoms, which resulted in only micro‐scale alterations in periphyton characteristics that were difficult to detect.5. Biomass accrual of ungrazed and grazed periphyton was described by the logistic growth equation. Loss of biomass due to grazing by D. gilvipesor to senescence and sloughing were incorporated in the model to account for changes in grazed and ungrazed periphyton. respectively. Proposed mechanisms which described biomass accumulation were largely sup ported by model predictions.

Critical Thermal Maxima of Nymphs of Three Plecoptera Species from an Ozark Foothill Stream

Prostoia completa, Isoperla namata and Phasganophora capitata nymphs captured from a second order stream in northeastern Oklahoma were exposed to a steady rise in temperature of 0.34°C/min to determine their critical thermal maxima (CTM). At a collection temperature of 6.5°C, the univoltine, winter emerging P. completa had a significantly lower mean CTM (31.5°C) than the univoltine, spring emerging I. namata and semivoltine, summer emerging P. capitata which had mean CTMs of 33.2 and 33.4°C, respectively. A one month age difference in I. namata (February to March) had no significant effect on mean CTM, and neither head capsule width nor sex of nymphs had a significant effect on the CTM within any of the three species. Phasganophora capitata nymphs collected at 6.5°C and acclimated to 17.0°C had a significantly higher mean CTM (36.3°C) than those maintained at the 6.5°C collection temperature (33.4°C). Isoperla namata treated similarly did not show a significant increase in temperature tolerance. Therefore...

The Effects of Washout in a Sierra Foothill Stream

The Effects of Washout in a Sierra Foothill Stream

Prey Selection by a Setipalpian Stonefly Nymph, Acroneuria (Calineuria) Californica Banks (Plecoptera:Perildae)

Predation by the stonefly nymph, Acroneuria (Calineuria) californica, was studied for 1 year in a Sierra Nevada foothill stream. Estimates of instantaneous consumption were obtained by analysis of the foregut contents of A. californica nymphs collected from the study stream at monthly intervals. The bulk of the prey items present in the guts consisted of chironomid larvae, baetid mayfly nymphs, and larvae of hydropsychid caddisflies. These three groups collectively made up &gt; 78% of all animal prey (by numbers) in the stonefly guts in each month except November. The stonefly nymphs were not strictly carnivorous. Detritus was consumed in all months, and Ulothrix, a filamentous green alga, was an important food source in the spring. Quantitative benthic samples were obtained at each collection date to determine prey availability. Electivity coefficients were calculated each month for each prey item. The electivity values, though somewhat variable, were generally positive for baetid mayfly nymphs and chironomid larvae, and negative for other prey. The most important factor determining prey selection appears to be prey availability. No great preference for any particular prey was apparent. Size considerations operate to limit the size of prey a stonefly can ingest but make larger prey more suspectible to discovery by the foraging stonefly.

Decline of the Native Fish Fauna of the Sierra Nevada Foothills, Central California

A survey was made of the fishes occurring in streams of the Sierra Nevada foothills above the San Joaquin Valley, California. Twenty-four species were collected, 12 native, 12 introduced. The pres- ent distributions of these fishes were' compared to their pre-1900 distribu- tions, as inferred from old records. Overall, the ranges of introduced species and rainbow trout ha,ve expanded while the ranges of native species, especially California roach, ha,rdhead, Sacramento squawfish and Sacramento sucker, have contracted. Healthy populations of native fishes were foundonly in a rather narrow middle elevation band of compara- tively undisturbed sections of foothill streams. The native fish popula- tions in different foothill stream systems are now isolated from each other and are., thus., in danger of local extinction as foothill development proceeds. The study indicates that populations of native stream fishes, even if they do not contain endangered species., should be protected, to make sure that severe natural conditions, when combined with human alterations of the streams, do not destroy unique assemblages of fishes.