摘要:

The Arkansas darterEtheostoma craginiis declining and now occurs in fragmented populations across its former range in the Arkansas River basin from Colorado to Arkansas. Regional surveys indicate that the Arkansas darter primarily inhabits small spring streams with dense aquatic vegetation, suggesting that specific habitat requirements may account for its widespread decline. Thermal tolerance and vegetation preference of the Arkansas darter from the western edge of its range in Colorado were measured in the laboratory and compared with those of the johnny darterE. nigrum, a more abundant habitat generalist from an adjacent basin. Critical thermal maxima of Arkansas darters acclimated to 20, 25, 27.5, and 30°C were higher than those forjohnny darters (35.0–38.4°C versus 34.0–37.4°C). In a modified upper incipient lethal temperature test, Arkansas darters acclimated to 27.5°C all survived 106 h at 30°C when the temperature was raised 1.5°C/h, but almost none survived more than 4 h of exposure to 34 or 36°C. Sixty percent survived 106 h at 32°C. In contrast, all johnny darters died within 17.5 h when exposed to 32°C and within 4.5 h when exposed to 34°C or higher. In behavioral choice trials in aquaria, Arkansas darters selected dense vegetation over open sand 72% of the time, with higher use during day (90%) than night (60%). In contrast, johnny darters showed little preference for vegetation (51% overall). Arkansas darters of the sizes we tested (28–55 mm total length) were able to withstand higher water temperatures than johnny darters (43–67 mm) and many other fishes of Great Plains streams, and they have an innate preference for aquatic vegetation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0676:TTAVPO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Growth and adult survival rates were estimated for the endangered Colorado squawfishPtychocheilus luciusinhabiting the upper Colorado River by using data from fish captured during 1990–1995. Mean annual growth rates of fish aged 3–6 years ranged from 32.2 (age 6) to 82.0 (age 3) mm/year. Growth rates for older fish were highest for fish 400–449 mm total length, TL, (42.7 mm/year) and declined to 19.8 mm/year for fish 500–549 mm TL. Fish 550 mm and longer grew an average 9.5 mm/year. Survival rates for fish 550 mm and longer were estimated by comparing measured size distributions with simulated stable age and size distributions; these ranged from 0.83–0.87, with the best fit at 0.85. Though lack of historical data precludes comparisons with past growth and survival rates, our data serve as a baseline for future population monitoring efforts.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0687:GASOCS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The South Fork basin of the Coeur d'Alene River, Idaho, has been an area of heavy mining activity since the 1880s. The mining operations have resulted in elevated concentrations of metals in surface water, most notably cadmium, lead, zinc, and, to a lesser extent, copper. The metals affected surface water quality downstream in the Coeur d'Alene basin and are suspected to be one of the primary reasons for the reduction in populations of native westslope cutthroat troutOncorhynchus clarki lewisi. The avoidance response of a surrogate species, Snake River cutthroat trout O. clarki (unnamed subspecies), was evaluated against conditions simulating those in the Coeur d'Alene River basin. Cutthroat trout avoided a metals mixture of these concentrations: Cd (0.30 μg/L), Cu (6.0 μg/L), Pb (0.6 μg/L), and Zn (28 μg/L). The avoidance response to either Cu or Zn alone was similar to the avoidance response to the mixture, suggesting that avoidance to the mixture was due to these metals. After acclimation to Zn at 55 μg/L for 90 d, cutthroat trout detected and preferred a lower Zn concentration of 28 μg/L. The lowest Zn concentrations avoided (28 μg/L) were 1/6 to 1/78 the Zn concentrations measured in the South Fork and lower Coeur d'Alene River basins. Avoidance of metals-contaminated habitats by cutthroat trout may be, in part, responsible for reduced fish populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0699:CTAOMA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Effects of transmitter attachment procedures on smolts of Atlantic salmonSalmo salarhave primarily been examined in the laboratory with hatchery-reared fish. Biotelemetry researchers must extrapolate findings of tagging studies to wild, migrating smolts. Because hatchery rearing can affect salmonid development and because field tagging procedures and environmental conditions can differ from those in the laboratory, we measured critical swimming speed of hatchery-reared Atlantic salmon smolts equipped with internal, external, or gastric dummy radio transmitters in the laboratory. We then repeated the experiment with wild, migrating fish in ambient environmental conditions. Swimming ability of hatchery smolts was not significantly affected by any attachment procedure, and no significant differences were found between fish tested 1 or 16 h after tagging. Similarly, wild smolts were not impaired by gastric transmitters; however, performance of wild fish tested 1 or 16 h after internal or external attachment was significantly lower than that of wild controls. Thus, reaction of hatchery-reared Atlantic salmon smolts to attachment procedures can differ from that of wild migrants. Biotelemetry researchers should exercise caution in interpreting data obtained from wild Atlantic salmon smolts equipped with internal or external radio transmitters during the first 16 h after tagging.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0707:IOTAPO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The recognition of bull troutSalvelinus confluentusand Dolly VardenS. malmaas separate species is a contentious issue in the state of Washington. Our analysis of 47 protein-coding loci indicated that at 5 loci fixed genetic differences exist between these species in the Olympic Peninsula and Puget Sound area of Washington. Samples from two Olympic Peninsula and two Puget Sound rivers contained only bull trout. A sample from a third Puget Sound river contained only Dolly Varden. A sample from a third Olympic Peninsula river contained both bull trout and Dolly Varden, but no evidence of hybridization or introgression existed. These results indicate these species are distinct and Sympatric in western Washington, and hybridization between them is not common. Thus, these fishes should be managed as separate species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0715:NGCOSB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.4.721

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor