摘要:

Laboratory studies have not duplicated the structure and composition of egg pocket centrums in redds of large salmonids, and thus have not accurately modeled survival of embryos and alevins in natural egg pockets. Field studies of capped natural redds have related survival to conditions in the redds or surrounding areas but not demonstrably in egg pockets. These data probably do not accurately reflect conditions faced by embryos or emerging alevins. The few data on egg pocket characteristics indicate that geometric mean particle diameter, fredle index, and permeability are higher in gravel surrounding the embryos than elsewhere, Survival to alevin emergence usually regresses positively on each of these factors separately and on dissolved oxygen in intragravel water. Survival to emergence usually relates negatively to percentages of small fines. Quantitative predictors depend upon careful definition of egg pocket structure through field surveying of egg pocket centrum locations and on intensive study of pocket conditions. Laboratory duplication of egg pocket structure and physical variables will permit more accurate modeling of effects of fines on survival to emergence. Redd capping in natural redds can provide estimates of survival to emergence, which one may relate to average egg pocket conditions and to variates in the redd. After appropriate modeling, it may become possible to relate conditions outside of the egg pocket to the environment within it and to survival-to-emergence.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0001:CROVUT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In an artificial stream channel, the distribution of juvenile coho salmonOncorhynchus kisutchand chinook salmonO. tshawytschaat various water temperatures and average water velocities was monitored with respect to use by the fish of water velocities, cover objects, and a simulated side pond area in two successive years. In year 1, water temperature was manipulated and average water velocity was held constant. In year 2, both water temperature and average water velocity were manipulated. For both wild and laboratory-reared juvenile coho and chinook salmon, more fish were associated with cover objects (year 1 and 2) or areas of low water velocity (year 2) at 2°C than at 12°C. In year 2, increasing average channel water velocity increased use of cover objects by coho salmon but not by chinook salmon. Coho salmon were more associated with cover objects and were found at lower average water velocities than were chinook salmon at all water temperatures and velocities. Coho salmon apparently have a greater cover-seeking reaction to lowered water temperature and increasing water velocity than do chinook salmon. Both species increased their use of the pond area in response to low water temperature in year 1, but reduced their use of it at 2°C during year 2. I conclude that low water temperatures and, to some extent, increases in water velocity may be important stimuli for microhabitat shifts often reported in stream observations of juvenile salmonids during the fall–winter transition.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0022:WTAVAD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Niche relationships of fishes can be inferred from dietary analysis. Individual fish and their prey can be ordered along an underlying continuum that has ecological relevance, The specific arrangement is a function of the predator's behavior and the prey's spatial distribution. This distribution of prey eaten by predators conforms to the underlying assumptions of detrended correspondence analysis. This multivariate technique, designed specifically for discrete data, uncovers underlying resource gradients in the dietary data. We used it to analyse dietary information collected from banded sunfishEnneacanthus obesusand bluespotted sunfishEnneacanthus gloriosusand compared then the results with analyses by discriminant analysis, factor analysis, and principal component analysis. Detrended correspondence analysis was as effective in discriminating among species on the basis of diet as discriminant analysis, and was much better than either factor analysis or principal component analysis in producing a small number of interpretable resource axes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0029:DCAODD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Dissolved oxygen data obtained for the nearshore areas of the New York Bight during 1974–1983 were analyzed statistically for relationships between physical environmental factors and bottom dissolved oxygen concentrations ([DO]). A multiple linear regression expression was developed as an estimator for bottom [DO] both as a function of the depth of the pycnocline and as an index of wind energy and its persistence, This latter index is called the quiescence–constancy (QC) index. The estimator for [DO] explained 86% of the variability over the decade of analysis. The utility of the estimator was examined in the context of several years not included in the analysis. In general, we found that deep pycnoclines and strong persistent southerly to southwesterly winds were closely correlated with low bottom [DO] averaged over the region. Shallow pycnoclines and strong but variable winds were associated with higher values of regionally averaged bottom [DO].

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0037:PEFCTR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Creek chubSemotilus atromaculatusfrom Rocky Fork, a metal-contaminated stream in north-central Ohio, and Clear Fork, a nearby uncontaminated stream, were studied to determine the effects of chronic heavy metal contamination from industrial and municipal sources on bone development. We examined bone development offish from two contaminated sites in Rocky Fork and from four reference sites – three in Clear Fork and one in Rocky Fork – to evaluate variability among reference sites, and to determine if the clean-water headwater site on Rocky Fork was a suitable reference site for the two downstream contaminated sites. Collagen composition, density, strength, and energy-absorbing capacity of bone were significantly higher in fish from the headwater site on Clear Fork (upstream from an impoundment) than in fish at the other three reference sites. In bones of creek chub from sites in Rocky Fork where the water contained high total concentrations of chromium, copper, iron, nickel, and zinc, the collagen content of bone was lower but density and strength were higher than in bone of fish from the reference site, Some fish also had deformed vertebrae in the caudal peduncle region of the spinal column, which is a condition characteristic of neuromuscular overload of vertebrae, The high concentrations of chromium and zinc in fish from the contaminated sites probably interfered with collagen metabolism and altered the density and mechanical properties of bone, Creek chub at the contaminated sites seem to be tolerant of heavy metal contamination and may be adapting physiologically to the chronic metal stress in their environment.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0048:BDICCF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We examined and measured cleithra, dentaries, opercles, and pharyngeal arches – bones found to persist during digestion of most prey fish – to identify 24 prey fish species and back-calculate their original fork length. Eighteen of the 24 species examined could be easily distinguished; however, for certain congenerics, identification was neither consistent nor reliable for all bones within the size ranges examined. Relations between bone length and fish length were linear for 14 species for which the sample sizes were adequate (N> 30); coefficients of determination (r2) ranged from 0.79 to 0.99. Diagnostic characteristics and measurements of these bones provided reliable identification of genera and species and estimates of original fork lengths of partly digested prey fish from three predators. This method, compared with that of examining only prey fish in a measurable condition, greatly increased the amount of dietary information available from gut analysis.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0055:UODBTI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Age structures of several populations of parasitic and nonparasitic lampreys were estimated from statolith band number and length-frequency distributions. In larval populations of the parasitic sea lampreyPetromyzon marinusand nonparasitic American brook lampreyLampetra appendix, which display strong seasonal patterns ofgrowth, one narrow dark band or annulus and one broad opaque band was produced each winter and summer, respectively. The formation of an annulus during slow growth was validated in two populations of sea lampreys with a chemical tissue marker, oxytetracycline. Length-frequency distributions required large samples to identify age groups, and the older age groups within a population were often difficult to distinguish because of overlap in size ranges. Thus, the assignment of age to an individual from its total length was likely to be imprecise unless that individual's length was close to the modal length of an age group. Some discrepancies in the assignment of population age structure were noted between the two methods. Annuli were not recognizable in the statoliths of larvae or adults from a population of southern brook lampreyIchthyomyzon gageithat displayed an even growth rate throughout the year, thus making length-frequency distribution analysis the only alternative.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0063:ADFL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Striped bassMorone saxatilisbreed in waters often affected by human activities that increase turbidity. Laboratory experiments were conducted to examine the effect of turbidity on the numbers and sizes of prey consumed by striped bass larvae during 25-min feeding trials. Larvae feeding on natural prey assemblages, primarily composed of copepods, consumed approximately 40% fewer prey in suspended solids concentrations of 200 and 500 mg·L–1than in 0 or 75 mg·L–1. In contrast, larvae feeding onDaphnia pulexcaptured the same average number of prey at all suspended solids concentrations tested. Turbidity also had no effect on the size of copepods orD. pulexeaten.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0072:EOTOPC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Efficiency of a 1.18-m3/min-capacity pump for sampling larval fishes quantitatively was compared with that of a 0.25-m2plankton net during monthly nighttime collections in a reservoir. Net samples contained seven fish taxa whereas only two were collected by pumps; however, gizzard shadDorosoma cepedianumand threadfin shadD. petenense(which usually could not be distinguished from each other as small larvae) accounted for more than 97% of the specimens caught in both samplers. Regression analyses indicated that pump catch rates (expressed as number per 1,000 m3) averaged 39.5% of the net catches for 3–6-mm shad larvae, 8.5% for 7–12-mm larvae, and 1.1% for 13–20-mm larvae. Coefficients of variation among triplicate pump samples averaged about 2.6 times higher than they did for net samples for 3–6-mm larvae, 4.5 times higher for 7–12-mm larvae, and 9.0 times higher for 13–20-mm shad. Although pumps usually provided density estimates that were lower and less precise than those obtained from nets, linear relationships between pump and net catch rates indicated that pumps can provide a measure of relative abundance useful for comparing densities of larval fish in habitats where sampling with nets is not feasible.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0078:REOAPF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Influences of inundated timber on distribution of larval fishes were evaluated during April–August 1982 in Lake Oconee, Georgia, by determining densities of larvae in two offshore timber plots and two adjacent open-water areas. Most (97%) of the larvae collected were gizzard shadDorosoma cepedianumand threadfin shadD. petenense, and these species were usually more abundant in or near the flooded timber than in nearby limnetic sites. Larvae of other fishes, includingLepomisspp.,Pomoxisspp., and white bassMorone chrysops, were rarely collected but occurred primarily at timbered sites. Higher abundance of larvae in the timber may reflect both extensive use of the flooded trees as spawning substrates and increased availability of food or shelter. Invertebrates and fish eggs collected incidentally during sampling for larvae were more abundant at timbered sites.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0084:ITANHF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor