摘要:

We assessed the influence of riparian disturbance on 26 stream variables in Linesville Creek and six tributaries, in northwestern Pennsylvania, USA. Redundancy analysis, a canonical ordination technique, was used in three separate analyses to test for significant relationships between riparian characteristics and the multivariate stream data (aspects of geomorphology, substrate composition, leaf litter processing and macroinvertebrate shredder species composition).

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663650

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Previous research on the distribution of Neosho madtoms, which are Federally-listed as threatened, indicated a positive relationship between density of Neosho madtoms and cumulative density of other riffle-dwelling benthic fishes. This suggested that interspecific competition was not limiting Neosho madtom populations. We provide further evidence that interspecific competition is not limiting Neosho madtom populations. Densities of fishes with habitat preferences similar to those of the Neosho madtom were positively correlated with Neosho madtom densities, whereas densities of fishes with different habitat preferences were negatively correlated. Slenderhead darter, suckermouth minnow, and juvenile channel catfish densities were positively correlated with Neosho madtom densities. Like the Neosho madtom, these species are found most often over gravel substrate with moderate flows; the suckermouth minnow is tolerant of high turbidities. Bluntnose minnow, western slim minnow, and bullhead minnow densities were negatively correlated with Neosho madtom densities. In contrast to the Neosho madtom, these species are found most often in pools or sluggish backwaters.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663651

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We investigated the roles of copper accumulated on leaves and in-stream copper concentrations in the inhibition of leaf decomposition in a copper-contaminated stream before and after treatment with a wetland passive treatment system. While post-treatment copper accumulations on leaves (CuL) were significantly related to in-stream copper concentrations (r2=0.42, p=0.0026), CuLwere not important determinants of the decomposition rate (r2=0.00053, p=0.92) or shredder abundance in leaf bags (r2= 0.003, p = 0.82), indicating that the inhibition of the decomposition rate in our study was not a response to CuLHowever, in a step-wise regression model that included leaf decomposition, CuL, in-stream copper concentrations, and shredders, in-stream copper concentration was the only significant effect and explained the most variation in the decomposition rate (r2=0.23, p = 0.02). The inhibition of leaf decomposition was a response to high (>10 μg/L) in-stream copper concentrations rather than CuLSince in-stream copper concentrations during most of the study were well above those known to affect microbial activity (≥ 22.5 μg/L), inhibition of leaf decomposition was probably due to effects of in-stream copper concentrations on shredding macroinvertebrates.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663652

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Thirty feeding trials were conducted using triploid grass carp (Ctenopharyngodon idellaVal.) fed hydrilla (Hydrilla verticillataRoyle) to establish feeding and growth rates as a function of fish size and water temperature. Size of fish ranged from 0.2 to 9.1 kg and water temperatures ranged from 17 to 27 C. Feeding trials consisted of fish and hydrilla housed in 4 m3wire mesh cages suspended at weekly intervals in an experimental pond. Utilizing pre- and post-weights of fish and hydrilla, weight gain, relative and absolute feeding rates, and feeding efficiency were found to increase with increasing water temperatures. Relative and absolute feeding rates for 0.2—0.4 kg fish at 17 C were approximately 25% of that for similar sized fish at 27 C. Above 25 C, these small fish consumed their body weight per day of hydrilla. While relative feeding rates (gm hydrilla/gm fish/day) declined with increase in fish size (at constant temperature), this was not the pattern for absolute feeding rates (gm hydrilla/fish/day) where consumption rates ranged from 750 to 1200 gm hydrilla/day for fish weighing more than 1 kg.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663653

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Lake and fish survey data (1991–1992) were compiled for 23 eastern South Dakota natural lakes to provide a basis for preliminary investigation of black bullhead (Ameiurus melas) populations. Survey data contained numerous physical and chemical variables describing lake environments and relative abundance and sue structure of the primary fish species present. Analyses indicated that abundance of black bullheads increased with decreasing lake size (area, depth and volume), increasing nutrients (e.g., total and dissolved phosphorus), and decreasing transparency. Overall, models of biotic variables indicated that black bullhead abundance was negatively associated with abundance of bigmouth buffalo (Ictiobus cyprinellus) and walleyes (Stizostedion vitreum), but positively associated with northern pike (Esox lucius) and common carp (Cyprinus carpio) abundance. Black bullhead sue structure was inversely related to the abundance of common carp, northern pike and yellow perch (Perca flavescens). Black bullhead population size structure was not related to any physicochemical variables. There appeared to be no regulation of black bullhead abundance or size structure by population size structures of other species.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663654

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The silverside (Odontesthes bonariensis), an introduced species, was studied in Laguna Grande of San Pedro (Laguna Grande) and Laguna Chica of San Pedro (Laguna Chica), both eutrophic lakes of the Biobío River basin in central Chile. The parameters analyzed were: biomass, production, length frequency, weight-length relationship, condition factor, age, and growthO. bonariensis, the most abundant fish species in the lakes, had high values of biomass and production, showing its adaptation to lakes of medium (Laguna Chica) and high (Laguna Grande) eutrophic status. Laguna Chica had greater biomass and production of silverside than Laguna Grande, confirming the hypothesis that the mesotrophic condition is more favorable than the highly eutrophic condition for certain species. In addition, the population of Laguna Chica reached an asymptotic length and a longevity that were greater than those of Laguna Grande. However, individuals of Laguna Grande were stoutter (better condition index), reflecting a higher availability of food in the eutrophic lake.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663655

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Immunological responses of fishes to glochidia were evaluated using glochidia of the rainbow mussel (Villosa iris) to infest a host species, rock bass (Ambloplites rupestris), and two nonhost species, common carp (Cyprinus carpio) and goldfish (Carassius auratus). Ouchterlony double-diffusion tests showed that host and nonhost species expressed a humoral defense factor specific to glochidial antigens after induced infestation with glochidia. Precipitin bands were observed in tests on infested fishes but not in tests on uninfested fishes. Microagglutination tests showed that host and nonhost species that were uninfested, infested, or reinfested with glochidia all expressed some agglutination response to glochidial antigens. Experimental fishes had specific humoral defense factors that reacted immunologically to glochidia tissue.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663656

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Spatial variability of aquatic macroinvertebrates was examined in riffles of second to fourth order streams in Onondaga Creek, in central New York, USA. Even with only small differences in stream sizes, aquatic macroinvertebrates were distributed primarily by a headwater-to-valley gradient as defined by mean stream width and water surface slope. Secondary and tertiary gradients were based on hydraulic character. Direct gradient analysis using canonical correspondence analysis (CCA) examined the common and rare (respectively, < 5—0.5% and 0.5—0.001% of total) macroinvertebrate assemblage among sites. The variables used in the analysis were mean wetted width, water surface slope, mean Froude number and Froude number variance. The first CCA axis explained 43.1% of the variability. Froude number variance and Froude number affected the second and third CCA axes most strongly. The gradients revealed by the second and third CCA axes did not influence lower gradient valley sites, but did separate the headwater sites based on hydraulic character. Taxa were also distributed by functional feeding groups (i.e., collector-gatherer). The headwater-to-valley gradient did separate taxa slightly by functional feeding groups; however, the hydraulic gradient clearly separated scrapers and shredders from collector filterers.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663657

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

When the riverweed darter,Etheostoma podostemoneJordan, was described in 1889, riverweed (Podostemum ceratophyllum) was abundant and the riverweed darter was closely associated with it. We compared current conditions ofP. ceratophyllumbeds to historical accounts, examined the association between the riverweed darter andP. ceratophyllum, determined substrate preferences exhibited by the riverweed darter during and after the spawning season, and compared habitat conditions in the North and South Forks of the Roanoke River.Podostemum ceratophyllumbeds were rare in the South Fork of the Roanoke River and nonexistent in the upper North Fork. Causes for the decline ofP. ceratophyllumare unknown, though sedimentation and reduced streambed stability are suspected. Median particle size was significantly lower in the North Fork compared to the South Fork. Riverweed darters were encountered in areas with a median particle size of 90mm, median depth-averaged velocity of 0.22m/s, and median depth of 24cm. Comparisons between microhabitat locations where riverweed darters were encountered and randomly chosen microhabitat locations revealed no significant differences; as a result, there is insufficient evidence to conclude that microhabitat selection by riverweed darters is non-random within shallow riffle habitats. However, spawning microhabitats of riverweed darters had higher velocities than randomly chosen microhabitats and higher velocities and depths than summer microhabitats.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663658

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Impacts of peaking generation on water quality in the tailwater of Lake Texoma, on the Texas and Oklahoma border, were evaluated during summer stratification in the lake. Sampling was conducted before, during, and after a daily generation cycle with measurements of temperature, dissolved oxygen, iron, manganese, and turbidity. Temperatures were near 25°C during generation, fluctuated 3–4°C during nongeneration, and increased in a downstream direction to near 28°C. Dissolved oxygen concentrations were between 4 and 6 mg L−1during generation and increased in a downstream direction. During nongeneration, concentrations in the upstream regon of the tailwater were near 2 mg L−1but were between 4 and 10 mg L−1in the rest of the study area. Maximum concentrations, 6 to 10 mg L−1, were observed prior to the hydrograph peak at each station, suggesting leading edge effects of increased flow and aeration as substrate was covered during river stage increases. Concentrations of metals increased in a downstream direction coincident with turbidity increases from near 3 to 25 NTUs, suggesting resuspension and possibly flocculation. Dissimilar patterns were observed for nongeneration when concentrations decreased in a downstream direction while turbidity was relatively constant and lower than generation values, suggesting settling with decreased flow.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663659

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor