摘要:

Zebra mussel veliger densities were monitored throughout 1996 at Lock and Dam 52 on the lower Ohio River near Brookport, IL. The spawning season occurred between mid June and early September with veliger densities peaking at 30,000/m3in late June. Veliger first appeared at a water temperature of 21° C. When spawning ended in September the water temperature was 22 °C. Veligers were found throughout November when the water temperature was 10 °C. The lowest temperature at which veligers were observed was 7 ° C in March 1996. These results show that the zebra mussels in the lower Ohio River are reproducing naturally and that spawning appears to be synchronous. The presence of larvae at low temperatures in March suggests that veligers are capable of delaying settlement and overwintering in the planktonic stage.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663617

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Radiotelemetry is a useful tool to describe habitat use by fish, but studies may inaccurately describe microhabitat use due to failure to account for errors when identifying fish locations. We developed a technique that identifies the extent of location errors of a hand-held radiotelemetry system. The ranges of location errors were determined among different observers, between land and water, and at an array of distances (5—125 m) between transmitters and receivers. No significant differences occurred among three observers at distances of 100 m or less or between transmitters on land or in water. Location error increased significantly with distance between transmitter and receiver; mean error was 0.5 m at 5 m and 4.5 m at 100 m. The 95th percentile of location errors was 1.5 m at 5 m and 10.5 m at 100 m. The number of trials needed to define location errors within 20% of the true mean (P≤ 0.05) was 109 at 5 m and 46 at 100 m. Determination of location error with radiotelemetry equipment can be conducted by two people on land with a relatively small amount of effort when the results are to be applied to relatively shallow waters.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663618

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We developed a 75th-percentile standard weight (Ws) equation to aid in the analysis of lake herring (Coregonus artedi) body condition over temporal periods and across populations. Weight-length data were obtained for 23,115 lake herring from 61 North American populations. The proposed equation is log10Ws= −5.517 + 3.224 log10TL, whereWsis the standard weight in grams and TL is the maximum total length in millimeters. The equation is valid for lake herring ≥ 100 mm and allows calculation of the relative weight (Wr) index. Significantly lower (P<0.001)Wrvalues were present for Lake Superior lake herring populations than for the “inland” populations, suggesting that Lake Superior herring weigh less at a given length. Based on the world record lake herring length (55.9 cm), we propose minimum standardized length categories of 13,20,28,35, and 43 cm for stock, quality, preferred, memorable, and trophy lengths, respectively. The length categories facilitate analysis across length groups and the calculation of stock density indices.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663619

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Occurrences of nymphs ofSeratella tibialisin streams of eleven western states were related to water quality and physical habitat parameters of stream stations. Nymphs were collected from only 182 of 903 stations sampled in nine states; the species was absent from all 50 stations in two other states.Seratella tibialisnymphs occurred mostly at stations with good water quality and stable stream banks. Absence of nymphs has limited predictive value since the distribution ofSeratella tibialiswas naturally spotty and the species was absent from the majority of stations.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663620

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The impacts of a large airport on the water quality and aquatic life of a small (94.8 km2drainage area) western Pennsylvania stream were examined. The principal adverse effects of airport runoff were related to runway deicing operations. Microbial metabolism of glycols and urea utilized as deicing reagents exerted a strong biochemical oxygen demand in receiving waters. Similarly, the breakdown of urea led to elevated concentrations of ammonia. The use of alkaline mill slag as a fill material in the construction of the runways was probably responsible for some elevated alkalinity and pH values from runway leachates. The organic waste load stimulated the growth of dense biological slimes on streambeds. Invertebrate communities in waters influenced by airport runoff were severely stressed and dominated by pollution tolerant Chironomidae and Oligochaeta. The fishery of the watershed was also impaired, although transient fishes from the nearby Ohio River apparently reinvaded the stream at certain times of the year.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663621

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Central stonerollers (Campostoma anomalum) were collected October 1994 through September 1995 from two third-order, warm-water Tennessee streams, Blackburn Fork and Spring Creek. Total lengths and numbers of externally-visible black-spot cysts were recorded for infected fish. Mean cyst densities, variance-to-mean ratios, and prevalence rates were consistently higher in Blackburn Fork than in Spring Creek. Peaks in prevalence and variance-to-mean ratios from Blackburn Fork occurred in September and January, respectively. Peak prevalence in Spring Creek occurred in October 1994. No trends in variance-to-mean ratios were observed in Spring Creek. Differences in black-spot metapopulations were due to cercarial transmission rates and undetermined abiotic factors.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663622

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of body size on fecundity, the gonadosomatic index (GSI), egg size, and timing of spawning of gizzard shad (Dorosoma cepedianum) was examined in two large Missouri reservoirs during 1987–1991. Fecundity significantly increased with both total length (TL) and weight of gizzard shad. However, neither GSI, mean egg diameter, nor variance of egg diameters were significantly related to either TL or weight. Rather, mean and variance of egg diameters significantly increased with GSI. Egg-diameter frequencies were not consistently different among TL groups of gizzard shad. There was no evidence that TL affected the timing of spawning. Body size may not affect the timing and duration of spawning of gizzard shad as previously suggested.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663623

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The presence of large numbers of adult goldeye (Hiodon alosoides) in backwater habitats of the upper Missouri River, combined with the presence of many other native fishes and their larvae, has raised questions about the predatory effect that goldeye may have on the larval fish community. Goldeye and larval fishes were sampled in backwater habitats during April, May, July, August, and September of 1997. Peak relative abundance of adult goldeye coincided with peak relative abundance of larval fishes in July. We examined the stomach contents from 161 goldeye collected in July and August to determine what proportion of the goldeye diet was composed of larval fishes. Only four stomachs contained larval fish (2.5% frequency of occurrence), and larval fishes composed less than 0.1% of the total number of food items. Corixidae, Coleoptera, and zooplankton (Copepoda and Cladocera) were the primary diet items.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663624

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Changes in attachment sites of a commensal chironomid,Nanocladius (Plecopteracoluthus) sp. (Diptera: Chironomidae), on the body of its host,Nigronia serricornis(Megaloptera: Corydalidae), were observed in laboratory streams over a 13-week winter period and a 6-week spring period to determine seasonal movement patterns and emergence success. All chironomid commensals were lost from their hosts by the end of the winter study and no emergence was observed. During winter, chironomids resided in the same tube location on hosts for approximately three weeks before changing positions or being lost from hosts. Vacated tubes remained attached to hosts for an average of 3.6 weeks. Eight re-position movements were documented on host bodies and six midges colonized new hosts in the stream. New colonizations occurred most frequently on previously colonized hosts. During spring observations, commensal midges migrated from the abdomen and ventral thorax to the lateral thorax prior to pupation. Emergence occurred between 6 June and 2 July in the laboratory streams. Emergence success was strongly influenced by commensal attachment site when more than one commensal resided on a host, but not when midges occurred singly. Overall, midges exhibited about 41% emergence success. Unsuccessful emergence was attributed to re-attachment failure following a host molt, host death, or unknown causes. These data suggest that commensal midges have high rates of movement after attaching to a host and attachment sites may determine, in part, emergence success.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663625

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Largemouth bass nesting disturbance significantly affected the distribution and abundance of macroinvertebrates in the littoral zone of Lake Wedington, AR. The total average densities and richness of benthic invertebrates were significantly greater outside than inside the nest areas throughout the reproductive period. Chironomidae, Oligochaeta, and Ephemeroptera dominated the samples, and densities of these invertebrates were consistently greater outside nests throughout this period. However, these alterations were transient and the recovery from the disturbance was observed within ten days following completion of largemouth bass nesting. The frequency and predictability of nesting disturbance and nature of disturbed substrate seem to be the factors affecting the persistence of the disturbance effects.

ISSN:0270-5060    

DOI:10.1080/02705060.1998.9663626

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor