摘要:

We investigated the interspecific interactions between the amphipod,Gammarus lacustris(Sars) and the cosmopolitan caddisfly,Ceratopsyche oslari(Banks). We believe this is an example of interference competition and may be one of several factors that limits the distribution ofC. oslarifrom the Colorado River below Glen Canyon Dam. Field observations indicated thatC. oslariwas associated with fewer food capture nets in the Colorado River than in the Paria River tributary. Laboratory experiments indicated the amphipodGammarus lacustris, which is abundant in the Colorado River but absent from the Paria River, had a detrimental effect on net-building success byC. oslari.Net numbers in laboratory chambers declined significantly after 6 d due to destruction by the swimming and feeding activities ofG. lacustris.Competition with the introduced, non-nativeG. lacustrisfor interstitial spaces along with several abiotic factors, may limit the distribution ofC. oslariin the Colorado River.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663681

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Between May 1994 and October 1995, 315 largemouth bass (Micropterus salmoides) and 170 northern pike (Esox lucius) were captured from three small impoundments in western South Dakota, tagged with Floy FD-94 (T-bar) anchor tags, fm clipped, and released. The number of days-at-large ranged from one to 512 days, with median time periods before final recapture of 63 days for 1994 and 376 days for 1995. No significant (P= 0.05) differences in growth or relative weight (Wr) were detected between tagged and untagged northern pike at-large from 345 to 387 days. Similarly, there were no significant (P= 0.05) differences in growth orWrof largemouth bass at large from 355 to 395 days. Tag retention was 88% for largemouth bass tagged and recaptured in 1994, and 92% for bass recovered in 1995 from the 1994 tagged group. Similarly, tag retention was 92% for northern pike tagged and recaptured in 1994, and 87% for pike recovered in 1995 from the 1994 tagged group. Floy FD-94 tag losses detected in this study were slightly lower for largemouth bass and slightly higher for northern pike in comparison with previous studies using similar anchor tagging systems.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663682

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Use of mark-recapture techniques to estimate the size of fish populations relies on several assumptions, one being that marked and unmarked fish have equal probabilities of capture. This requires that marked fish, if released at their site of capture, mix randomly with unmarked fish in the population before recapture. We tested whether marked fathead minnows (Pimephales promelas) in four wetlands mixed randomly 1) when released at the capture site and 2) when transported and released in the center of the wetland. We captured and marked fish at two locations on opposite sides of each wetland. We recaptured fish three weeks later at these two original capture stations and at two additional sites spaced equal distances from the two capture stations. Results using fish released at their original capture location and those released in the center of the wetland indicated no difference between the observed and the expected number recaptured, with the expectation being equal numbers caught at each station. Our results indicate that researchers using mark-recapture methods to estimate fathead minnow population size may release marked fish at the site of capture and obtain accurate estimates.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663683

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Winter distribution and diet ofPagastiella ostansa(Diptera: Chironomidae) were investigated in Big Brower Lake, Kent Co., Michigan. Big Brower Lake is a small (34.4 ha), shallow (Zmax=7.5 m), meso-to-eutrophic lake.P. ostansalarvae were found at only two littoral zone stations characterized by soft, organic sediments andCharasp. beds. LarvalP. ostansagut content analysis compared with sedimentary algal assemblages indicated selective foraging and ingestion of large, benthic, pennate diatoms. Winter diet included the diatomsNavicula oblonga, Navicula cryptocephala, Nitzschiasp. 2,Stauroneis anceps, Stauroneis phoenicenteron, andPinnularia maior, whereas more common blue-green algae and small and colonial diatoms present in the sediment assemblage were not ingested.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663684

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We determined effects of acidification on sediment aerobic heterotrophic exo-amylase and exo-protease producing microbial populations in addition to effects on the total microbial population. Acidification of microcosms to sediment pHs of 6, 5, 4, and 3 followed by plate counts showed that numbers of total aerobic heterotrophic microbes, as well as numbers exo-amylase producers and exo-protease producers, decreased at pH 3. It appears that pH 3 may represent a critical level of damage. Numbers of total aerobic heterotrophs also decreased at pH 4. Numbers of all groups increased at pH 6. An accompanying change in species composition was observed with acidification, in which a type of microbe with little production of exo-amylase or exo-protease became dominant in the microbial community as pH decreased. Analysis of three metals (Al, Pb, Cu) indicated an increased mobilization of metals from the sediments at low pHs.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663685

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Standards for the assessment of age and growth data for channel catfish (Ictalurus punctatus) were developed using published data. A representative set of 102 studies of individual populations from across the geographic range of channel catfish was selected. Percentile values (5, 10, 25, 50, 75, 90, and 95th) were computed from the distribution of estimated mean total lengths for fish three to ten years old. This approach for development of standards to assess data from age and growth studies of fish is proposed for consideration in development of standards for other species in addition to channel catfish.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663686

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We studied effects of chum salmon spawning activities on nutrients, epilithic algae, and benthic insect communities in a small stream of Pacific Northwest. The reach with salmon spawning had greater concentrations of Kjeldahl-N, NH4+-N, and total soluble P than the reach without salmon. However, chlorophyll a concentration was lower in the reach with salmon. In particular, chlorophyll a concentration was significantly lower during salmon spawning. Three caddisfly genera and two stonefly genera collected from salmon carcasses fed on salmon flesh. The total insect density in containers baited with salmon flesh was significantly greater than in containers without salmon flesh, but the difference was insignificant for the total biomass. Orthocladiinae andBaetissp. had significantly greater densities and biomasses in the containers with salmon flesh. These results support the notion that mass salmon spawning activities affect structure and dynamics of ecosystems.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663687

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Hexagenia bilineata, a large-bodied mayfly, provided a convenient model for the study of the physiological ecology of the Ephemeroptera. The thorax temperature (Tth) of free-flyingH. bilineatawas significantly different from ambient temperature (Ta), but the gradient between them was only about 1° C, which is probably not biologically significant.H. bilineatais clearly ectothermic, and low wing loading may explain the low Tth.H. bilineataemerges during warm and stable weather, when endothermy would provide little advantage.H. bilineatahad a very high ratio of flight muscle mass to body mass, which is expected to result from selection pressure on flight performance, yetH. bilineatais a poor flyer. This effect may be a result of freedom from weight constraints.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663688

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The larval habitat ofMonodiamesa ekmaniBrundin in Lough Neagh. Northern Ireland is shallow water. ≤5m depth, on a sandy substrate. Within that habitat, larval distribution is affected by the degree of disturbance of the sediment due to wave action. Larvae are most abundant generally at 4m depth, where disturbance is low throughout the year. In an area of sand bars, larvae are more abundant in the bar troughs than on the crests at times of high disturbance, but they are more evenly spread through the area in the summer when disturbance is less frequent. The life cycle appears to be of one year's duration, with emergence in May-June.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663689

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Nutrient-diffusing substrata were used to test for nutrient limitation of periphytic epilithon in North Boulder Creek. Green Lakes Valley, Colorado. Both N and P were co-limiting. In addition co-limitation by P and Si was observed. In a few experiments humic acid promoted biomass accrual, but more research is needed to discover its exact role in the growth of periphyton.

ISSN:0270-5060    

DOI:10.1080/02705060.1999.9663690

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor