摘要:

We determined the abundance of the recently described brook darter,Etheostoma burri, in three tributaries of the Black River, Missouri, utilizing Petersen mark-recapture methods. In tributaries located in Johnson's Shut-Ins State Park and at Mill Spring,E. burrioccurred at estimated densities of 2.18 and 1.58 fish/m2, respectively. These densities were similar to those reported for orangethroat darters in an Ohio stream and were intermediate-to-high in comparison to other darter species. However, no brook darters were observed at our third study site, suggesting thatE. burrimay also be absent from other Black River tributaries.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663665

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We used drift fence arrays with pitfall traps to compare amphibian and reptile assemblages at the peripheries of beaver (Castor canadensis) ponds of two age-classes (“new”: ≤ 5 yr old, and “old”: ≥ 10 yr old) and unimpounded streams in the Piedmont of South Carolina. The richness and total abundance of amphibians were not significantly different among new beaver ponds, old beaver ponds, and unimpounded streams, although several species of anurans were captured predominantly or exclusively at beaver ponds. Amphibian community overlap and diversity also were similar among the three habitats. In contrast, the richness and total abundance of reptiles were significantly higher at old beaver ponds when compared to new beaver ponds and unimpounded streams. The degree of reptile community overlap also was relatively low, with significant differences in diversity among all three habitats. Differences in amphibian and reptile community attributes between beaver ponds and unimpounded streams likely were related to the lentic or lotic habitat requirements of individual species and the effects of beaver impoundments on surrounding upland habitats.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663666

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We monitored densities and growth of juvenile bluegills (< 45 mm sl) stocked in autumn into a coastal Georgia freshwater pond that was managed as a wood stork feeding habitat. Cage experiments were used to examine how fish stocking rates and detrital supplements affected fish survival, fish growth, and the availability of invertebrate food supplies. As fish became large enough (> 50 mm standard length) to be useful wood stork food, the majority sought refuge in beds of vegetation and were thus not readily available to storks until July when a complete drawdown concentrated them in residual water. Bluegill growth and survival were not affected by detrital supplements or fish stocking rates (even as high as 450,000/ha). However, detrital hay supplements increased densities of tadpoles and most invertebrates. Fish density did not significantly affect invertebrate abundance.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663667

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The phytoplankton and physicochemistry of the canalized lower Scarpe River in northern France were studied from April 1992 to October 1993. The phytoplankton was dominated by diatoms in spring and autumn and by chlorophytes in summer. There was an irregular occurrence of cyanophytes, which characterized a eutrophic river environment. Certain centric diatoms typical of eutrophic environments (Stephanodiscus hantzschii, Cyclostephanos dubius), which were present in a high proportion in 1992, were replaced in 1993 by other species characteristic of moderate to large size rivers (Asterionella formosa, Aulacoseira granulata). The seasonal variation observed on the lower Scarpe River was similar to that of the large European rivers. Changes in certain chemicals and the phytoplankton community indicated some improvement in river water quality subsequent to the start-up of a new sewage treatment facility in 1992.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663668

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The organophosphorus insecticide malathion has been used in insecticide-diffusing substrata (IDS) to reduce aquatic insect colonization and grazing activity, thereby facilitating study of stream ecosystem function. Although there has been some concern that malathion may provide a source of P, previous investigators have assumed that malathion has no direct inhibitory effect on algae. In a seasonal study of 12 New Zealand streams, malathion exposure frequently caused significant decreases in algal biomass accrual. Inhibition of algal biomass accrual by malathion was more severe under conditions of enhanced nutrient supply. Malathion exposure also substantially reduced insect densities. However, statistically significant invertebrate responses to malathion exposure were uncommon because of high variability of insect densities on IDS. These results suggest that 1) direct inhibition of algal biomass accrual by malathion in IDS should not be discounted, and 2) malathion-induced reductions in insect density and grazing pressure on IDS may be spatially variable and difficult to detect without extensive replication.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663669

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Bluespotted sunfish are diurnal foragers in coastal Mississippi preying mainly on cyclopoid copepods, amphipods, cladocerans, chironomids, ostracods, and gastropods. Cyclopoid copepods, cladocerans, chironomid larvae and oligochaetes were collected in submersed aquatic vegetation (SAV)/SAV-associated sediments throughout the year but were most abundant in the warm (April-September) months. Ostracods, amphipods, and hydracarinids were also collected in SAVISAV-associated sediments throughout the year but tended to be most abundant during fall, winter and early spring (October-April). Fish ≥ 20 mm standard length (SL) selected 87.5% of the available prey from SAV/SAV-associated benthos compared to fish < 20 mm SL, which selected only 40%. Mean annual electivity values suggested random prey selection. The only obvious difference in diet was that fish ≥ 20 mm SL consumed gastropods and amphipods while fish < 20 mm SL rarely consumed amphipods and never consumed gastropods. Bluespotted sunfish exhibit an opportunistic feeding behavior and apparently feed outside the SAV when small but shift into SAV as they grow.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663670

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We compared seasonal changes in tissue C, tissue N, C:N ratio, and total phenolic acids for five species of submersed plants from Fall River, California. Mean tissue C differed among the five species and was between 35 and 40%, except forRanunculus aquatilis, which was 26%. Mean tissue N differed among species;Ranunculus aquatilishad the lowest mean value (2.71%) andZannichellia palustrishad the highest (3.74%). Mean C:N ratio was between 9.7 and 12.7. Among the five species examined, mean phenolic acid content was greatest forMyriophyllum sibiricumand it was nearly seven times that for the species with the lowest phenolic acid content,Elodea canadensis. Regression analysis indicated positive relationships between phenolic acid content and tissue C for two species,Callitriche hermaphroditicaandRanunculus aquatilis. Regression equations relating phenolic acid content to tissue N were not statistically significant. ForElodea canadensis, the equation describing phenolic acid content as a function of the C:N ratio had a negative slope, while the equation forCallitriche hemaphroditica, had a significant positive slope. Knowledge of the relationships between plant nutrient content and phenolic acids may lead to better understanding of aquatic plant/herbivore/microbe interactions and might result in improvements in the timing of applications of biological control agents in aquatic plant management.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663671

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Field observations revealed cases of predation on horsehair worms by brown trout (Salmo trutta) in Maryland and Minnesota, a rock bass (Ambloplites rupestris) in Kentucky, and a crayfish in Wisconsin. Some fish contained more than one worm and may have consumed reproductive aggregations. In laboratory feeding trials withGordius robustus, most individuals of several fish species either ignored the horsehair worms or rejected them after taking them into their mouths briefly, but a green sunfish (Lepomis cyanellus) consumed both individual worms and a compact ball of 18 worms. A literature review yielded cases of predation on horsehair worms by at least 12 fish species. Horsehair worms usually were only a trace component of the diet, but some individual fish had eaten multiple worms.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663672

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We examined seasonal and diel variation in the diet and prey selection (Chesson's α) of field-collected predatory stoneflies (Acroneuria abnormis). In the laboratory, we investigated how stoneflies feed on two morphologically and behaviorally distinct prey types (Baetis sp.andHydropsyche sp.) commonly found in the diet ofA. abnormis. OneA. abnormiswas presented with either: (1) 20Baetis sp., (2) 20Hydropsyche sp.added 30 hours prior to stonefly addition, thus having time to construct retreats, or (3) 20Hydropsyche sp.added just prior to stonefly addition, thus having no time to construct retreats. Stonefly behavior was videotaped at night during 30 minute trials in circular, plexiglass streams illuminated by infrared light. Numbers of prey encounters, attacks, and captures were recorded, and handling time was determined.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663673

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Survival of five species of bacteria was determined in freshwater microcosms containing stream water, leaves, and sediments. Native stream species (Burkholderia cepaciaandAeromonas caviae) became established in sediment biofilms, but coliforms (Citrobacter freundiiandEscherichia coli) and an insecticide-producing bacterium,Bacillus thuringiensis, did not.A. caviaeandB. thuringiensiswere common on leaf surfaces, but population sizes were much lower than those ofB. cepacia. Population sizes of all species decreased substantially in the water column over the course of the seven day experiments. To examine the basis of this high mortality in the water column, the effects of predation, competition, and resource limitation were examined. Competition and predation attributable to smaller microorganisms (< 1μm) had the greatest impact on bacterial mortality. These results suggest that the overall significance of benthic habitats as sources of stream bacteria was enhanced by high rates of mortality in the water column. Bacteria that enter streams through human-mediated means (sewage in the case of coliforms, and insecticide application in the case ofB. thuringiensis) differed in their survival; biofilms enhanced the success ofB. thuringiensisbut not the coliforms.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663674

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor