摘要:

We conducted a relocation study of unionid mussels in Navigation Pool 7 of the upper Mississippi River (river mile 713.2) to evaluate survival after handling and aerial exposure. Two separate studies were conducted to compare seasonal differences in mussel survival; the first was initiated in June and the second in October.Amblema plicata plicata(subfamily Ambleminae) andObliquaria reflexa(subfamily Lampsilinae) were studied. Mussels were marked, held out of water for either 0, 1, 4, or 8 h, and then placed into a 3 × 3 m grid (divided into nine 1-m2units). The mussels were re-examined after four-five months to measure mortality in the control and treatment groups. Mussels of both species had >90% survival after aerial exposure up to 4 h in both studies. However, survival (number recaptured live/number recaptured live and dead) of mussels showed a decreasing trend with duration of exposure in the first study, but not in the second study. The overall recovery of marked mussels (number recaptured/number marked) was 91% in the first study and 87% in the second study. However, only 37% ofO. reflexamussels in the 8-h treatment were recovered in the first study; the adjusted survival (number live recaptured/number marked) of this treatment group was significantly (p < 0.05) lower (35%) than all other treatments.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663439

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The trophic ecology of five shredder taxa found in Mink Creek, Idaho was determined in laboratory food quality experiments to assess the obligate or facultative nature of resource utilization among lotic taxa commonly referred to as detritivores. The experiments tested resource assimilation for each taxon among three major resources available to primary consumers in streams; periphyton, fine particulate detrital material (FPM) and coarse particulate detrital material (CPM). Growth of each taxon was determined on each resource in laboratory experiments conducted at 10° C.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663440

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The benthic macroinvertebrates of Boomer Creek, Oklahoma, were surveyed in spring 1993, approximately four years after the complete drawdown of Boomer Lake, an impoundment of Boomer Creek. Drawdown restored the old stream channel within the lakebed to free-flowing conditions, which resulted in a temporary reestablishment of Boomer Creek through the lakebed site. Collections of invertebrates were made at eight locations in each of three stream reaches: upstream and downstream of the former impoundment, and in the stream channel within the former lakebed. Forty-three taxa were found in the stream, 33 of which occurred in the lakebed channel. Macroinvertebrate composition differed significantly among the three stream reaches, but macroinvertebrate densities did not. Dominant taxa in all areas were oligochaetes, chironomids, and a corixid predator of these groups.Trichocorixasp. Other common taxa found includedHyalella azteca. Procambarussp.,Physellasp., andSphaeriumsp. Thirteen taxa found in the lakebed channel were also found in an earlier (pre-draining) study of Boomer Lake macroinvertebrates.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663441

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We measured the feeding rate of individual (0.6–12.2 g) young-of-the-year ruffe (Gymnocephalus cernuus) on the live eggs of lake whitefish (Coregonus clupeaformis) at 3, 5, and 9°C in the laboratory. These temperatures were selected because they covered the range of lake temperatures over which eggs of most Great Lakes coregonines would be most vulnerable to predation by ruffe. Ruffe readily consumed lake whitefish eggs, and regression analysis showed consumption increased with ruffe size and water temperature. Mean daily egg consumption as a percent of mean ruffe body weight was 0.25% at 3°C, 0.59% at 5°C, and 1.00% at 9°C.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663442

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Samples of drifting American shad eggs were collected with 0.5 mm mesh nets at two transects in the Savannah River near industrial water intakes. At each transect the river was divided horizontally and vertically into four sectors that were sampled at two hour intervals for 24 hour periods to assess horizontal and vertical patterns of egg distribution that could affect vulnerability to entrainment. Egg densities varied by an average factor of 20 over a 24 hour cycle and were consistently highest between 2300 and 0300 and lowest between 1300 and 2000. We used two methods to separate spatial from temporal variance, analysis of covariance (ANCOVA) with a polynomial model for time of day as the covariate and a detrending technique in which diel variation was subtracted from each data point. These procedures resulted in substantially more sensitive tests of sector differences as indicated by minimum detectable ratios of sector means that were only half as great as for unadjusted data. Spatial patterns differed between transects but were generally consistent within transects where three to four-fold differences among sector means were common. The actual risk of entrainment was approximately 35–50% lower than if the shad eggs were uniformly distributed, and the risk of entrainment was lower at one intake than at the other. Our results indicate the importance of site specific assessments of ichthyoplankton distribution near existing or proposed water intakes using statistical designs that permit sensitive resolution of spatial patterns.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663443

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Algal bioassay tests were conducted withSelenastrum capricornutumand natural algae on inner Las Vegas Bay, Lake Mead, Nevada, from December 1992 through September 1993, to identify any nutrient limitation in an area of the reservoir that has experienced problems associated with severe nutrient enrichment. Three areas were sampled based on a gradient of water quality conditions that existed in Las Vegas Bay (LVB). Disodium ethylenedinitrilotetraacetate (EDTA) significantly stimulated algal growth compared to non-EDTA treatment. Algal bioassays indicated that phosphorus (P) was the primary limiting nutrient at all stations for most of the test dates. Chlaresponse with EDTA + phosphorus (EDTA+P) was significantly greater (p<0.05) than the control response. These tests suggest that continued P enrichment of lower LVB may well result in increased algal productivity.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663444

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The distribution, age structure, and movements of the unionid musselElliptio complanata(Lightfoot) were studied in a first-order stream in Virginia, USA. Mean density of the mussel in this low-gradient, sand-bottomed stream was 2.5 individuals/m2and biomass was 3.4 g dry mass/m2. About 87% of the population had a shell length of 6–9 cm, or age of 4–6 years. Only 11% of the population was less than four years old; the age of the oldest individuals encountered was only eight years. Distribution of the mussels was highly clumped, but no physical, chemical, or hydrologic factors examined were significantly correlated with mussel abundance. All young mussels (age < three years) were burrowed into the sediment, whereas older individuals occurred both below and at the sediment surface, depending on time of year. About 90% of the population was burrowed below the surface during the winter, but a high of 80% of the mussels moved to the surface in March and April, the time of peak reproductive activity. Tagged mussels moved an average of 2.9 m during one year. Although the direction of those movements was erratic, the overall movement of the population was a net 27 cm downstream, indicating no directed upstream movement to compensate for downstream displacement during storms.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663445

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We examined rates of internal phosphorus (P) loading from sediments in Lake Pepin, an impoundment on the upper Mississippi River. Laboratory-determined rates of P release from the sediment, measured using intact sediment core systems, were very high, with mean values ranging from 3.8 to 15 mg m−2d−1under oxic and anoxic conditions, respectively. Independently-determined Fickean diffusional fluxes (mean of 4.9 mg m−2d−1), measuredin situunder oxic conditions using sediment peepers, were not statistically different from those rates determined in the laboratory under similar temperature, pH, and oxygen conditions. The dominant inorganic P fractions in the sediments were NaOH-extractable P and HCl-extractable P. Under both oxic and anoxic conditions, significant correlations existed between rates of P release and the NH4Cl- and NaOH-extractable P fractions, suggesting mat loosely-bound and iron- and aluminum-bound sediment P contributed to P release from the sediments in this lake. Correlations between total sediment P and extractable sediment P fractions indicated that loosely-bound and iron- and aluminum-bound P increased, while calcium-bound P decreased, with increasing total P content of the sediment. Our results suggest that internal P loading from die sediments under oxic, as well as anoxic, conditions can play a very important role in the P economy of this system.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663446

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We sampled macroinvertebrate communities at six sites on the upper Clark Fork River, Montana, to determine relations between macroinvertebrate community structure and metals in invertebrates and the best benthic community metrics to use for ranking sites based on the relative severity of the effects of metals. Concentrations (μg/g) of six metals in invertebrates were determined: Al (range = 591–4193), As (2.7–34.1), Cd (0.13–8.38), Cu (26–1382), Pb (0.54–67.1), and Zn (212–1665). Concentrations of As, Cd, Cu, Pb, and total metals were significantly correlated with at least one benthic metric. Copper (r = 0.88–0.94) and total metals (r = 0.90–0.97) provided the most highly significant correlations. Based on longitudinal site comparisons of metals in invertebrates, benthic community structure, and differences between proportionally scaled ranks, five benthic metrics provided the best indicators of relative impact: taxa richness, Ephemeroptera-Plecoptera-Trichoptera (EPT) richness, chironomid richness, percentage of the most dominant taxon, and density. The two sites with the highest accumulations of invertebrate metals also demonstrated the greatest relative degree of impact based on these parameters. The most meaningful combinations of metrics indicate that the benthic community at the most upstream site is being severely impacted by metals. Two sites demonstrated little or no negative impact, and three sites demonstrated low or moderate levels of negative impacts, which may be due to a combination of metals and other factors such as organic enrichment. We recommend that benthic community structure and metals in invertebrates collected from riffle habitats be used to determine relative impacts in metals-contaminated river systems, owing to their close relation to metal availability and transfer to higher trophic levels.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663447

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Weight and length data were obtained from state, regional, and provincial biologists for 241 channel catfish (Ictalurus punctatus) populations, representative of the species geographic range. We randomly selected 60% of the populations to develop a new standard weight (Ws) equation and used the remainder as an independent test set. The regression-line-percentile (RLP) technique was applied to the development data set providing a 75th percentile-based metricWsequation of log10Ws(g) = −5.800 + 3.294 log10total length (TL, mm). The English equivalent is log10Ws(lb) = −3.829 + 3.294 log10TL (in). The remaining 98 populations were used to test both current and newWsequations for length-related changes in relative weight (Wr) values. Regression ofWrvalues on TL by population showed that the current equation produced 15% more slopes that were significant (H0: β = 0) than did the new equation. An analysis of significant slopes produced from the RLP-generated equation showed a ratio of 31 positive to 20 negative slopes. The current equation yielded a ratio of 58 positive to 7 negative slopes. Because of the length-related trends inWrvalues associated with the current equation we recommend that researchers apply the new RLP equation to field data for further testing and validation. The new RLPWsequation is valid for application to channel catfish having a TL of 70 mm or greater, as opposed to a minimum TL of 280 mm recommended for the current equation.

ISSN:0270-5060    

DOI:10.1080/02705060.1995.9663448

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor