Limestone Treatment of Whetstone Brook, Massachusetts. I. Treatment Methodology and Water-Chemistry Changes during Treatment

Whetstone Brook is a trout stream located in north-central Massachusetts that is degraded by acid precipitation. The stream was treated with 56 tonnes of powdered limestone by a prototype, water-powered doser as part of the U.S. Fish and Wildlife Service's Acid Precipitation Mitigation Program. The goal of liming Whetstone Brook was to raise the pH to 6.5 and acid neutralizing capacity (ANC) to at least 50 μeq/1 in a 3.2-km reach. This goal was achieved despite the fact that during the 31 months of treatment stream flow was 37% higher than during the pretreatment period. During the treatment period, pH averaged 6.54 and ANC averaged 69.75. During the pretreatment period average pH was 5.97 and average ANC was 20.26. In the control section of Whetstone Brook, both pH and ANC were lower during the treatment period than during the pretreatment period. During treatment, monomeric aluminum, a form toxic to fish, declined in the treated section and increased in the control section. Total calcium, sediment calcium, and pore-water calcium increased in the treated section during treatment but declined in the control section. The other base anions and cations, nutrients, and physical parameters were not significantly affected by liming.     

Limestone Treatment of Whetstone Brook, Massachusetts. II. Changes in the Brown Trout (Salmo trutta)and Brook Trout (Salvelinus fontinalis)Fishery

Density, age structure, and growth rates of wild brook trout (Salvelinus fontinalis)and brown trout (Salmo trutta)in Whetstone Brook in northcentral Massachusetts were monitored for 4 years before and 3 years during limestone treatment to mitigate acidic conditions. The population density of brook trout increased significantly during treatment. Liming did not have any significant effects on the growth rates of brook trout or brown trout. Actual survival rates of brook trout and brown trout were not calculated due to the low density of both species, but more older individuals of both species were captured during the treatment period. Fulton condition factors (an index of fish condition) increased significantly for both brook trout and brown trout during treatment. Seven-day in situ bioassays of brown trout and rainbow trout demonstrated that liming improved the chemical environment for fish in Whetstone Brook. During a pretreatment bioassay in 1987, 100% rainbow trout mortality was observed at both the control and treatment stations in Whetstone Brook. Brown trout mortality was 67% in the control station and 70% in the treatment station. The pH during the 1987 bioassay averaged 4.90 in the control station and 4.99 in the treated station. During a bioassay conducted in 1990 after treatment began, rainbow trout mortality was 100% in the control station and 0% in the treatment station. Brown trout mortality was 17% in the control station and 0% in the treatment station. The pH during the 1990 bioassay averaged 5.23 in the control station and 6.60 in the treatment station. Analysis of total aluminum in the gills of fish from the 1990 bioassay revealed higher levels in fish from the control station than in those from the treatment station.     

Black fly larvae facilitate community recovery in a mountain stream

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Diel foraging in relation to available prey in an Adirondack Mountain stream fish community

The diets of the fish community of Trucka Brook, a small stream located in the central Adirondack Mountains in northern New York, were examined in relation to the bottom fauna and invertebrate drift. Measures of overlap were calculated between the diets of each fish species examined, brook trout (Salvelinus fontinalis), blacknose dace (Rhinichthys atratulus), creek chub (Semotilus atromaculatus) and pearl dace (Semotilus margarita). Overlap was also examined between the fish diets and bottom and drift samples. Blacknose dace, pearl dace and brook trout had the most similar diets which were closely associated with the benthos. Creek chub had the most distinctive diets which did not compare well with any other fish species during either diurnal or nocturnal periods. The mayfly nymph Litobranchia recurvata was the most abundant bottom invertebrate and was the major prey of benthic feeding fishes. The invertebrate drift did not compare favorably with any of the fishes' diets because of the predominance of large cased limnephilid larvae (primarily Psychoglypha sp.) which were not readily consumed by fish.     

Spatial and temporal occurrence of invertebrates in a chalk stream,Berkshire, England

The invertebrate assemblages of the River Lambourn and its tributary, the Winterbourne stream, were investigated as part of a broad ecological study prior to water resource development in the catchment. The longitudinal distribution of the invertebrate fauna within the Winterbourne stream was examined in detail and supporting data for the R. Lambourn revealed that the upstream intermittent section of each water course had an invertebrate assemblage which was distinct from the fauna downstream where flow was permanent. Within the perennial zone taxon richness tended to increase downstream.A one-year programme of monthly quantitative sampling on five distinct biotopes (Ranunculus, Berula, Callitriche, gravel and silt) at two contrasted sites (shaded and unshaded) was undertaken in the lower perennial of the R. Lambourn below the confluence with the Winterbourne. On each study site, the taxon richness, numerical abundance and biomass of invertebrates were significantly higher on the three macrophytes than on gravel and silt. There were also statistically significant seasonal changes in the biomass of invertebrates on each site. Estimates of total biomass of invertebrates per site revealed a late spring peak (May/June) and a late autumn (November/December) peak, neither of which coincided with the summer peak biomass of macrophytes. This suggested that, in the lower perennial, the level of food resources (epiphytic algae in late spring and fallen tree leaves plus decaying macrophytes in autumn) rather than available habitat, were a major influence on population levels for most of the year.Quantitative sampling of each biotope on each site continued in June and December only for a period of 8 years (1971–78), during which time the river experienced a minor drought (1973) and a severe drought (1976). The Chironomidae showed a strong positive response to conditions of low flow in June of 1973 and 1976, when exceptionally high densities of larvae were recorded. Although further between-year differences were recorded in several other major components of the invertebrate fauna, which may have been related to conditions of low discharge, they did not have long-term consequences for the fauna in the lower perennial of the R. Lambourn.In contrast, in the upper perennial, the prolonged drought of 1976 resulted in the loss of wetted perimeter and macrophytes, coupled with deposition of silt, all of which had deleterious effects on the invertebrate assemblages. The following year, despite a normal discharge regime and the removal of silt, some submerged macrophytes were slow to return to their pre-drought condition. In the intermittent section, the drought of 1976 resulted in the total loss of flow for a 16 month period instead of a more typical four month period of water loss.Thus, chalk streams encompass within a single system both stable and extreme hydrological regimes which offer unique opportunities for investigating the processes of community formation and maintenance.     

Stream invertebrate communities of Campbell Island

Invertebrates at 20 sites on 19 Campbell Island streams were sampled over the Austral summer of 1996/97. Twelve of the 16 benthic invertebrate taxa known from the island were collected. The most abundant group was the Crustacea, which included an isopod (Notidotea lacustris) and two amphipods, one belonging to the family Eusiridae and one to the suborder Gammaridea. Five species of Diptera were found (three chironomids; Orthocladiinae sp., Chironominae sp. and Maoridiamesa insularis, as well as an empidid and a simuliid Austrosimulium campbellense). One trichopteran, the hydroptilid caddis Oxyethira albiceps and two plecopteran species Rungaperla campbelli and R. longicauda and unidentified Oligochaetes were also collected. In general, Campbell Island streams are stable, deeply incised, have unusually high salinity from wind-blown sea spray and a unique benthic invertebrate fauna. With the exception of high altitude streams with large boulders which had invertebrate communities dominated by Crustacea and the endemic stonefly of the genus Rungaperla, none of the measured environmental variables or geographic location could explain the distinctive communities found. The species-poor stream fauna and the absence of many invertebrate families commonly found on mainland New Zealand appears to be related to the extreme isolation and geological history of the island.     

Short term biotic response before and during the treatment of an acid mine drainage with sodium carbonate

The lower portion of Upper Three Runs, a woodland stream in central Pennsylvania, receives acid drainage from a strip mine. In 1974, the effect of this input on pH and benthic invertebrates was studied by Tomkiewicz & Dunson (1977). We sampled the same stations in 1986 and then treated the mine drainage with sodium carbonate for seven days in an effort to evaluate the short term colonization response of brook trout (Salvelinus fontinalis) and invertebrates. No differences in the pattern of pH and invertebrate distribution was found between the 1974 and 1986 results, although pH values and invertebrate densities were higher in 1986. Total number of invertebrates and number of taxa colonizing bricks during three pre-treatment time periods (8, 10, 18 days) did not differ from the single treatment period (7 days). However, two species of Baetis (Ephemeroptera: Baetidae) did increase in the treatment section during sodium carbonate application. The number of brook trout also increased in the treatment section, as compared to one pre-treatment estimate. These results indicate that motile species are able to respond within seven days, whereas, longer treatment may be required to produce community wide responses.Author to whom correspondence should be addressed     

Benthic macro- and meso-invertebrates of a sandy riverbed in a mountain stream, central Japan

Quantitative samples of benthic invertebrates were collected from a sandy riverbed of a mountainous stream (Kozu site of Takami-gawa stream, Nara Prefecture), central Japan by core samplers in five sampling occasions through the years 2008–2009. A total of 120 taxa were identified, representing 55 families and 97 genera. Insects formed about 92% of the total recorded taxa and 88% of individuals’ abundance. A total of 111 taxa of aquatic insects, belonging to 49 families and 92 genera, were identified and represented by ten orders. Oligochaeta and Acari were dominant non-insect invertebrates. Diptera was the most diverse insect group, followed by Trichoptera and Ephemeroptera. Dominant taxa were mesoinvertebrates, younger stages of macroinvertebrates, both of which predominantly inhabit the interstitial zone of a sandy riverbed. Both taxon richness and invertebrate abundance were higher in February 2009 and lower in April and August 2008. A few major invertebrate taxa demonstrated distinct seasonal trends; i.e. Nymphomyia alba, Rheosmittia, and Corynoneura were abundant in February 2009. Newly hatched larvae of Larcasia akagiae were abundant in May 2008. This study also demonstrated the effectiveness of core samplers to collect small-sized benthic fauna that inhabit the interstitial or hyporheic zone of the sandy riverbed.     

Changes in the benthic fauna and flora after application of temephos to a stream on Mt. Tsukuba

A dose of 2 ppm of temephos in emulsifiable formulation was applied to a mountain stream to observe its effects on the zoobenthos and the subsequent changes in benthic algae. Most zoobenthos in the treated region drifted but there were slight differences among taxa. Ephemeroptera and Plecoptera disappeared but some Trichoptera and Diptera survived. Chironomids recolonized earlier than other invertebrates and reached a higher density level than before the treatment. A bloom of benthic algae occurred following the destruction of fauna. The increase in the standing crop of algae was accompanied by an increase in the number of species. Among these, Achnanthes lanceolata, Meridion circulare and Tetraspora gelatinosa were predominant. The end of the bloom began with the recovery of the zoobenthos population.     

Stratigraphy and Palaeontology of mid-Carboniferous Sequences at Phu Bo Bit in Loei Province,Thailand

The rocks from the Phu Bo Bit section consist of shale and limestone along with an abundant and diverse invertebrate fauna consisting of brachiopods, corals, bryozoans and crinoids, interpreted as having been deposited in shallow marine or shelf environments. At Phu Bo Bit, thick limestone lenses in shale contain microfossils. Based on the foraminiferan and algae assemblage, the stratigraphic sequence of Phu Bo Bit extends from the late Bashkirian to the early Moscovian. According to lithofacies and palaeontology, the Phu Bo Bit section represents the change from carbonate to siliciclastic sedimentation, which provides new evidence on the marine regression during the mid-Carboniferous.     

Determinants of abundance and effects of blood-sucking flying insects in the nest of a hole-nesting bird

Compared to non-flying nest-dwelling ectoparasites, the biology of most species of flying ectoparasites and its potential impact on avian hosts is poorly known and rarely, if ever, reported. In this study we explore for the first time the factors that may affect biting midge (Diptera: Ceratopogonidae) and black fly (Diptera: Simuliidae) abundances in the nest cavity of a bird, the hole-nesting blue tit Cyanistes caeruleus, and report their effects on adults and nestlings during reproduction. The abundance of biting midges was positively associated with nest mass, parental provisioning effort and abundance of blowflies and black flies, while negatively associated with nestling condition. Furthermore, a medication treatment to reduce blood parasitaemias in adult birds revealed that biting midges were more abundant in nests of females whose blood parasitaemias were experimentally reduced. This finding would be in accordance with these insect vectors attacking preferentially uninfected or less infected hosts to increase their own survival. The abundance of black flies in the population was lower than that of biting midges and increased in nests with later hatching dates. No significant effect of black fly abundance on adult or nestling condition was detected. Blood-sucking flying insects may impose specific, particular selection pressures on their hosts and more research is needed to better understand these host–parasite associations.     

The Flora and Invertebrate Fauna of a Relocated Grassland at Thrislington Plantation, County Durham, England

In order to extend quarrying near Thrislington Plantation, County Durham, England, 8.5 ha of magnesian limestone grassland was relocated over a period of eight years from October 1982. The effects of this on the flora and invertebrate fauna were examined within the Festuca-Helianthemum community at five plots relocated at different times. Plants were sampled with a point-quadrat, and invertebrates by pitfall trapping. Comparisons were made between age of the relocation, numbers of species and individuals, and diversity of flora and invertebrates. The plots were examined using the percentage similarity measure. The plots showed an initial change in some aspects of community structure for flora and invertebrate fauna, followed by a “recovery” period. This was particularly evident in the numbers of species and species diversity of plants and in the numbers of individuals and species diversity of invertebrates. Bare ground, left by the relocation process, was still evident between relocated turfs in the early plots, but it was successfully colonized by resident species in later plots. These results have implications for the future management of this and similar sites, particularly with respect to the emphasis placed on subsequent monitoring and the need to consider invertebrate faunas when implementing management strategies.     

Birch leaf processing and associated macroinvertebrates in an acidified lake subjected to liming

In connection with the liming of an acid lake in southern Norway, a series of litter bags was placed in a pH-gradient in the limed lake and a nearby unlimed lake. During the experiments, which lasted two years, no significant differences in decomposition rates between the various localities at the same depth were noticed. The chironomid collector Tanytarsus pallidicornis was the dominant invertebrate species in the benthic samples. This demonstrates the importance of fine particulate organic matter as a food source in the lake. Collector dominance was lower in the leaf packs, which consisted mostly of coarse particulate organic matter. A poor fauna of detritus grazers probably contributed to the unchanged rates of decomposition of the leaves after liming.     

Disturbance to a stream food web by a bacterial larvicide specific to black flies: feeding responses of predatory macroinvertebrates

1. A field study was conducted to: (i) assess feeding habit changes of two predatory stoneflies following the loss of larval black fly (Diptera: Simuliidae) prey from two streams; and (ii) determine the relative importance of black fly larvae as prey for these and other selected predatory benthic macroinvertebrates. 2. Acroneuria lycorias and Paragnetina media (Plecoptera: Perlidae) diets were monitored in response to local reductions in larval black fly populations caused by Bacillus thuringiensis var. israelensis (B.t.i.) in two Michigan streams. These predators were collected from B.t.i.-treated and control sections of the streams, and their foreguts inspected for prey. 3. Black flies were the major dietary component of both predators collected from the control sections, but the number of black flies ingested was significantly less for predators collected from B.t.i.-treated habitats. Total number of prey ingested significantly decreased for A. lycorias, but not for P. media, and non-black fly prey consumption significantly increased for P. media, but not for A, lycorias, following B.t.i. applications. 4. In prey choice trials conducted in experimental channels, A. lycorias and P. media showed no preference between prey types (black flies and mayflies). Body mass gain of individual A. lycorias nymphs was measured, and was similar for nymphs in black fly-rich and black fly-poor environments. Conversely, Isoperla signata and I. dicala (Plecoptera: Perlodidae) ingested significantly more Simulium vittatum (Diptera: Simuliidae) than Baetis flavistriga (Ephemeroptera: Baetidae) or Epeorus vitrea (Heptageniidae) prey. Boyeria vinosa (Odonata: Aeshnidae) ingested significantly more B. flavistriga than S. vittatum prey. 5. Reducing black fly densities in these streams, using B.t.i., indirectly and differentially affected predators. In black fly-poor environments, feeding habits of specialist predators were most affected, and generalist predators least affected because the latter consumed alternative prey. Predator—predator and predator-prey interactions, and prey community structure may be affected indirectly by disturbances such as B.t.i. applications by reducing food resources and forcing predation onto less preferred prey.     

Long-term effects of local disturbance history on mobile stream invertebrates

The patchy distribution of benthic invertebrates in streams and rivers is an important and widely researched phenomenon. Previous studies on reasons for this patchiness have neglected the potential role of local disturbance history, probably because most lotic invertebrates are mobile and any effect of disturbance history was thought to be short-lived. Here we demonstrate for a New Zealand gravel-bed stream that local disturbance history can have long-term effects on the distribution of highly mobile stream invertebrates. Buried scour chains (100 at each of three 20-m sites within a 350-m reach) indicated that a spate with a return period of 5 months caused a mosaic of bed patches with different stabilities. More than 2 months after the spate, we took random, quantitative samples at each site from five patches that had experienced 4 cm or more of scour during the spate, from five patches with 4 cm or more of fill, and from five stable patches. Density of the dominant invertebrate taxon, the highly mobile mayfly Deleatidium spp., and densities of another three of the seven most common taxa differed significantly between patch stability categories. Larvae of Deleatidium, the black fly Austrosimulium spp. and the dipteran Eriopterini were most abundant in fill patches, whereas Isopoda were most abundant in scour patches. Total invertebrate densities and densities of six common taxa also differed between sites, although these were only 95–120 m apart. These results show that local disturbance history can have long-term effects on lotic invertebrates and be an important cause of invertebrate patchiness. The observed effects might have been even stronger had we sampled sooner after the spate or after a large flood. Disturbance history may influence invertebrates both directly (through dislodgement or mortality) and indirectly, through effects on the spatial distribution of their resources. Our results suggest that the role of disturbance in structuring animal communities dominated by mobile species may be more important than previously thought. Received: 25 January 2000 / Accepted: 14 April 2000     

Larvicidal potential of the polyol sweeteners erythritol and xylitol in two filth fly species

The house fly, Musca domestica (L.) (Diptera: Muscidae), and the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), are two filth flies responsible for significant economic losses in animal production. Although some chemical control products target adults of both species, differences in mouthpart morphology and behavior necessitates distinct modalities for each. For these reasons, larvicides are an attractive means of chemical control. We assessed the potential of the polyol sweeteners erythritol and xylitol as larvicides to the house fly and stable fly. LC₅₀ values of erythritol against 2^nd instar larvae were 34.94 mg/g media (house fly) and 22.10 mg/g media (stable fly). For xylitol, LC₅₀ values were 74.91 mg/g media (house fly) and 41.58 mg/g media (stable fly). When given a choice, neither species showed a preference for ovipositing in media treated with either sweetener at various concentrations or in media without sweetener. Significantly lower development from egg to adult was observed when the 2^nd instar LC₅₀ equivalent of each sweetener was present in the media compared to controls. Erythritol and xylitol both have larvicidal qualities, however their effective concentrations would necessitate creative product formulation and deployment methods to control all stages of developing flies.     

Effect of diet switch timing and food source on survival and growth of lake sturgeon

Studies were conducted to determine the effects of diet switch timing and food source on hatchery survival and growth of lake sturgeon (Acipenser fulvescens) during a 7‐ and 6‐week period in 2004 and 2005, respectively. Diet transitions to bloodworm (Diptera: Chironomidae) and black fly (Diptera: Simuliidae) larvae were undertaken 1, 2, 3 or 4 weeks after an initial diet of brine shrimp (Artemia spp.) in 2004, and 2 or 4 weeks after initiation of feeding in 2005. In 2004, mean (±SE) final survival was significantly lower following early (week 1, 50.8 ± 8.3%) vs late (week 4, 83.3 ± 3.9%) diet switches, regardless of diet type; however, rearing lake sturgeon on black fly larvae led to significantly higher mean survival rates (78.7 ± 3.3%) in comparison to bloodworm diets (56.5 ± 6.5%). Fish reared in 2005 on black fly larvae showed no significant differences in mean (±SE) final survivals when switched early (week 2, 96.7 ± 1.0%) vs late (week 4, 97.6 ± 0.5%), but those groups transitioned to bloodworm did significantly worse following the early diet switch (week 2, 91.9 ± 1.7%; week 4, 99.0 ± 1.0%). Final mean (±SE) mass was significantly higher for lake sturgeon reared on black fly larvae (0.63 ± 0.02 g) vs bloodworm (0.53 ± 0.02 g) at the end of the 2004 study period, despite having received fewer daily feedings; however, this difference was not observed the following year (bloodworm, 1.48 ± 0.07 g; black fly larvae, 1.43 ± 0.07 g). While there was no significant difference in final mean mass (±SE) of fish among the various diet switch points in 2004 (week 1, 0.54 ± 0.05 g; week 2, 0.57 ± 0.03 g; week 3, 0.60 ± 0.01 g; week 4, 0.59 ± 0.03 g), there was a significant advantage to transitioning fish early in 2005, regardless of food type (week 2, 1.60 ± 0.03 g; week 4, 1.31 ± 0.02 g). Given our results from both years, we conclude that transitioning larval lake sturgeon to black fly larvae following 2 weeks on an initial diet of brine shrimp can maximize survival rates without sacrificing final sizes, while reducing effort and cost associated with culturing brine shrimp and feeding bloodworm.     

Spatial and temporal patterns in the fish assemblages of individual pools in a midwestern stream (U.S.A.)

Synopsis The composition and consistency of fish assemblages in 14 adjacent pools (6–120 m long) of a clear-water, limestone and gravel creek in midwestern U.S.A. were quantified in eight snorkeling surveys over 19 months, to establish a baseline of natural variation in the system at this scale. The fauna of the stream was dominated numerically by minnows (Cyprinidae), sunfish and black bass (Centrarchidae), and topminnows (Fundulidae). The pool fish fauna of the total 1 km reach (including all 14 pools) was highly consistent throughout the study, despite two major floods. Assemblages in individual pools generally were consistent, but there was more variation within pools than at the scale of the entire reach. Throughout the study, most individual pools remained within discrete subsets of the total occupied multivariate space in a principal components analysis based on fish species abundances. Sunfishes (Lepomis spp.) and bass (Micropterus spp.) were more consistent in their distribution among pools than were minnows (Cyprinidae) or a topminnow (Fundulus). There were 25 significant correlations in occurrence of species pairs among stream pools, out of 91 possible comparisons of the 14 most abundant taxa in the reach. Many pools contained assemblages either dominated by large centrarchids or by abundant cyprinids and juvenile centrarchids, but intermediate assemblages also were observed. The dynamics of distribution of fish species and fish assemblages among individual stream pools are likely influenced by a combination of species-specific behaviors and habitat selection, predator constraints on use of individual pools by small fishes, riffles as size-selective barriers to fish movements between pools, dispersal of young-of-the-year fishes, and abiotic phenomena like floods. Individual stream pools appear to be discrete habitat units for fishes, and do represent an appropriate scale for biologically meaningful studies of fish assemblages or their effects on streams.Department of Zoology, University of Oklahoma     

Macrophytes in Urban Stream Rehabilitation: Establishment, Ecological Effects, and Public Perception

Efforts to rehabilitate degraded urban streams generally focus on improving physical habitat and rarely include reestablishing biota such as macrophytes. Our objectives in this study were to propagate and transplant native macrophytes into a South Island, New Zealand, urban stream undergoing rehabilitation, assess macrophyte survival and growth, and determine whether native macrophytes suppress non-native macrophytes and/or enhance stream invertebrate communities. Effects of native macrophytes on invertebrates and non-native macrophytes were assessed after transplanting patches of native macrophytes into a 230-m-long stream section. A 100-m-long section upstream was left unplanted for subsequent comparisons. Following the study, a survey was conducted to gauge public opinion about the rehabilitation project and determine whether macrophytes were prominent in perceptions of stream health. In the first growing season, native macrophyte cover in the planted stream section increased from 1.5 to 20%, and then decreased during winter. Regrowth from rhizomes led to rapid aboveground growth during the second year, when cover reached 51%. Non-native macrophytes colonized the stream the first year, but native macrophytes appeared to limit the spread of non-natives, which were absent in the planted section by the second spring. Native macrophyte establishment did not enhance invertebrate communities as predicted; few invertebrate metrics differed significantly between the planted and unplanted sections. Pollution- and sediment-tolerant invertebrate taxa were abundant in both sections, suggesting that invertebrate colonization was limited by water quality or sedimentation, not macrophyte composition. Survey respondents considered the stream to be visually and ecologically improved after rehabilitation, and macrophyte establishment was generally considered positive or neutral.     

Benthivorous fish reduce stream invertebrate drift in a large-scale field experiment

Drift as a low-energy cost means of migration may enable stream invertebrates to leave risky habitats or to escape after encountering a predator. While the control of the diurnal patterns of invertebrate drift activity by fish predators has received considerable interest, it remains unclear whether benthivorous fish reduce or increase drift activity. We performed a large-scale field experiment in a second-order stream to test if invertebrate drift was controlled by two benthivorous fish species (gudgeon Gobio gobio and stone loach Barbatula barbatula). An almost fishless reference reach was compared with a reach stocked with gudgeon and loach, and density and structure of the invertebrate communities in the benthos and in the drift were quantified in both reaches. The presence of gudgeon and stone loach reduced the nocturnal drift of larvae of the mayfly Baetis rhodani significantly, in contrast to the findings of most previous studies that fish predators induced higher night-time drift. Both drift density and relative drift activity of B. rhodani were lower at the fish reach during the study period that spanned 3 years. Total invertebrate drift was not reduced, by contrast, possibly due to differences in vulnerability to predation or mobility between the common invertebrate taxa. For instance, Chironomidae only showed a slight reduction in drift activity at the fish reach, and Oligochaeta showed no reduction at all. Although benthic community composition was similar at both reaches, drift composition differed significantly between reaches, implying that these differences were caused by behavioural changes of the invertebrates rather than by preferential fish consumption. The direction and intensity of changes in the drift activity of stream invertebrates in response to the presence of benthivorous fish may depend on the extent to which invertebrate taxa can control their drifting behaviour (i.e. active versus passive drift). We conclude that invertebrate drift is not always a mechanism of active escape from fish predators in natural streams, especially when benthos-feeding fish are present.