摘要:

We defined relations of environmental variables and fish community features to statistics of samples of rainbow troutOncorhynchus mykissfrom lakes and reservoirs in Wyoming. The mean length of rainbow trout in gill-net samples was most strongly related to physical features, including elevation, measures of water chemistry, and lake morphology. Indices of abundance and biomass of rainbow trout were related to the proportion of other fish species in gill-net samples, as well as elevation, water chemistry, and lake morphology. Environmental gradients associated with changes in elevation appeared to have substantial influence on the population structure and abundance of rainbow trout in lakes and reservoirs in Wyoming.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0925:EGARTP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Critical thermal maximum (CTM) and resistance time to high temperature were determined for juvenile Arctic graylingThymallus arcticusfrom the fluvial population of the Big Hole River, Montana. Grayling were tested after acclimation to 8.4, 16.0, and 20.0°C. Thermal tolerances increased with acclimation temperatures; mean CTM was 26.4°C for the 8.4°C acclimation group, 28.5°C for the 16.0°C group, and 29.3°C for the 20.0°C group; median resistance time at given test temperature also increased with acclimation. The upper incipient lethal temperature (UILT) was 23.0°C for fish acclimated to 8.4°C and 16.0°C, and was 25.0°C for those acclimated to 20.0°C, temperatures that were similar to the median tolerance limits of Arctic grayling in Alaska. Comparisons of mean CTM and UILT for juvenile Arctic grayling with levels and durations of maximum river temperatures recorded during summers 1992–1994 indicated that resident fish may occasionally be subjected to potentially lethal temperatures in the warmest reaches of the Big Hole River.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0933:HTTOFA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We determined prolonged swimming ability of larval and juvenile Colorado SquawfishPtychocheilas luciusat 10, 14, and 20°C. Fatigue velocity (velocity at which 50% of the fish failed to sustain swimming in 30-min tests) increased significantly with water temperature and fish length. Differences in swimming ability between 10 and 14°C became less pronounced as fish length increased, but differences remained substantial between the two cooler and the 20°C swimming experiments for all size-classes tested. We conclude that cold hypolimnetic releases from hydroelectric dams can significantly reduce prolonged swimming ability of young-of-year Colorado Squawfish, and may help explain the decline of this species in the Colorado River basin.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0940:TEOSPO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Some fishes, including bluegillsLepomis macrochirus, have highest critical swimming speeds at their preferred temperatures; however, it is not known why fishes select temperatures that are optimal for performance. This paper examines the relationship between selected temperatures and critical swimming speeds for bluegills to test the hypothesis that fishes select temperatures in response to available power. A rationale is presented that available power is a useful short-term measure of fitness among intraspecific competitors, that Fry's scope for activity is a measure of available power, and that critical swimming speed is a function of Fry's scope for activity and can be used as a measure of available power. Results of this study supported the hypothesis by demonstrating that for each acclimation temperature, critical swimming speeds of bluegills were highest at preferred temperatures, and decreased at other temperatures with frequency of time spent at those temperatures, although the exact nature of the relationship has yet to be determined. These results supported the concept that fishes select temperatures on the basis of available power and have implications for quantifying and predicting the energetic cost of exposure of fish to sublethal temperatures.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0948:TSAPBB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We investigated the feeding ecology of the tidewater gobyEucyclogobius newberryi, a California estuarine fish that is federally listed as an endangered species. We compared the diet during three seasons (April, August, and November 1992) in three habitats (lagoon, creek, and marsh). Tidewater gobies (N= 331; standard lengths [SL], 15–46 mm) fed on benthic invertebrates, principally ostracods, chironomid larvae, and the gammarid amphipodCorophium spinicorne. Other prey taxa included polychaetes, oligochaetes, isopods, the gammarid amphipodEogammarus ramellus, copepods, mysids, and invertebrate eggs. Diet variability within samples was low, but diet varied across seasons and sometimes habitats. The tidewater goby appeared to be a specialist that can forage opportunistically in some circumstances. Comparisons between the diet and available resources in August indicated selectivity in the lagoon and marsh (albeit for different prey), but general feeding in the creek. Laboratory observations of feeding behavior revealed preferences forC. spinicorneand chironomid larvae (without the mucus tube) and suggested that substrate differences among the habitats could influence the diet by altering the mode of feeding (sifting sand in mouth versus plucking prey from gravel). Comparison of the diets ofjuveniles (<27 mm SL) and adults did not reveal an ontogenetic shift in diet. Analysis of the daily feeding pattern in November showed that juveniles fed at all hours whereas adults fed principally at night. The tidewater goby's feeding ecology suggests that it is adaptable to a variety of habitats. Fish from the marsh were substantially larger than those from other habitats, suggesting that marshes provide better opportunities for growth. The tidewater goby's diet overlaps with those of other California gobies, including two introduced species that are potential competitors and predators.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0956:FEOTTG>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Using single-locus microsatellite markers, we have resolved higher levels of genetic variation than previously reported for northern pikeEsox lucius. We isolated 14 (AC)n·(TG)nmicrosatellite loci from a genomic library of northern pike. Primer pairs for the polymerase chain reaction (PCR) were developed for nine of these loci. With PCR, a DNA-amplifying technique, we were able to assess genetic variability using fish scales as our source of DNA. In four populations, we found four polymorphic loci with three or four alleles at each locus. Average heterozygosity at all loci was 0.075. Although this level of genetic variability is the highest reported for this species, it is much lower than that found for many other fish species by using microsatellite markers. Small numbers of founder fish, combined with loss of variation due to genetic drift in the small populations typical of northern pike, may explain the relatively low levels of genetic variation we found.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0971:NMDMRN>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The basis of behavioral differences between populations of river- and lake-spawning walleyeStizostedion vitreumwas evaluated. We used fish from one population that migrates up a river to spawn on gravel bars and from another that remains in a lake to spawn on rocky shoals as broodstock to produce genetically tagged fry of each stock. Offspring from these broodstocks were introduced into a system containing both habitats. When the stocked walleyes had reached sexual maturation 3 and 4 years later, adults in reproductive condition were collected throughout the impoundment–river system. Walleyes that were the offspring of broodstock from the river-spawning population were captured more frequently in lotic habitat well upstream from the impoundment, whereas offspring of the lake-spawning population were found more frequently in lake habitat. This result is consistent with the hypothesis that choice of spawning habitat has a heritable component: walleyes have a genetically based response to environmental cues that guides them to spawning habitat.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0978:EFHPFS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This study was designed to investigate the effects of embryonic exposure to methylmercury (meHg) on social behavior of larval mummichogsFundulus heteroclitus. Embryos from two sites (polluted and unpolluted) were exposed to 5 and 10 μg meHg/L during development; after hatching, the larvae were transferred to clean seawater. Testing was performed weekly for 4 weeks after hatching. The variables examined were distance between individuals, duration of parallel swimming, and number of collisions or repels. Data indicated that mercury exposure significantly increased the number of collisions by larvae from the unpolluted reference population but not from the polluted population. This effect disappeared by 4 weeks after hatching, indicating that the damage to the developing nervous system was reversible. No trends toward increased parallel swimming or decreased distances between individuals (behaviors that would reflect the beginning of schooling) appeared during the 4 weeks. This indicates that schooling behavior in this species develops when larvae are older than the ones tested.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1996)125<0983:DOSBIL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-125.6.988

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor