摘要:

Lower-lethal-temperature bioassays were performed with blue tilapiasTilapia aureato test the utility of a lethal-dose model for forecasting cold-kill events. We applied the model to predict resistance times of blue tilapias acclimated to 24°C upon exposure to lower lethal temperatures varying between 5° and 13°C. Regression of predicted versus observed logarithmic median resistance times was significant, and the line of perfect agreement fell within the 95% confidence limits on the regression line. However, the model consistently underestimated the resistance time in tests that lasted longer than a few hours, presumably because fish in these tests achieved some downward thermal acclimation. We also applied a second model, developed for predicting upper incipient lethal temperatures, to the cold-resistance data from blue tilapias in an attempt to estimate the lower incipient lethal temperature (LILT) of fish acclimated to 24°C. Although the model's estimate of LILT, 14. 1°C, is reasonable, there is still concern about the model's applicability to cold-resistance data.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0112:NPTLOF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Temperature-sensing ultrasonic transmitters were used to monitor the behavior of eight individual lake troutSalvelinus namaycushin two lakes: a shallow lake that becomes isothermal (15–20°C) during late summer and a typical dimictic lake with a cold hypolimnion. Use of a cool, nearshore groundwater discharge site, a behavior never before documented for lake trout, was observed among some fish in the shallow lake when ambient lake temperatures exceeded the species' preferred thermal range of 6–13°C. We suggest that during very warm years, groundwater refugia may be important habitat for lake trout and that these refugia should be protected.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0118:CWAWEB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Woody debris is an important feature of streams, and its presence and abundance have been correlated with the abundance, growth, and survival of juvenile salmonids. To investigate the proximate mechanisms linking brushy woody debris to salmonid fishes, we determined, over a 1-month period in summer, the spatial distribution of juvenile coho salmonOncorhynchus kisutchintroduced into an outdoor experimental stream containing riffle-pool units that had one of four different levels of instream brushy-debris complexity. We then equalized the fish density in each unit and monitored fish growth and survival over a 15-week period. Coho salmon distribution, growth, and survival varied greatly but were not consistently related to the complexity of brushy debris.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0124:SDSAGO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Many laboratories rely on periodic rereading of reference collections of scales or otoliths to ensure that their age readers remain consistent in their age interpretations, both through time and with other age readers. Measures of both systematic difference (bias) and precision are required for this purpose, because measures of bias are not suitable as measures of precision, and vice versa. Using data from an age comparison study of haddockMelanogrammus aeglefinusfor demonstration purposes, we evaluated a variety of graphical and statistical approaches for making paired age comparisons from the standpoint of both detecting age differences and assessing precision. Parametric and nonparametric matched-pair tests, regression analysis, analysis of variance, and age difference plots were all capable of detecting systematic over- or underaging. However, only the age bias plot was sensitive to both linear and nonlinear biases. The coefficient of variation (CV = SD/mean) was a robust measure of precision, whereas the widely used percent agreement statistic was not. The combination of an age bias plot, an age frequency table, and a CV provides a powerful and easily prepared comparison of matched pairs of age determinations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0131:GASMFD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Histological examination of formalin-fixed ovarian tissues from sexually mature red drumsSciaenops ocellatusand black drumsPogonias cromisrevealed abnormally shaped oocytes, modified histological staining properties, and infections of a large, gram-positive, rod-shaped bacterium. These conditions were encountered only during the species' respective spawning seasons and occurred at seasonal incidences of 0–33%. We have variously interpreted the abnormalities as artifacts of poor tissue preparation, as an unusual form of midseason atresia, as an epizootic, and as artifacts of delayed or incomplete preservation of tissues. While a definitive interpretation has yet to be reached, a return to and strict adherence to prompt and complete preservation of all ovarian tissues has drastically decreased incidences of the anomalies and bacterial infections in both species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0139:HAABPI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A simple method for initiating continuous cultures ofPerkinsus marinuswith hypnospores is described. The visceral mass of an infected eastern oysterCrassostrea virginicawas first incubated in Ray's fluid thioglycollate medium in order to produce large hypnospores from the smaller histozoic stages of the protozoan. Hypnospores were then purified and transferred into the culture medium JL-ODRP-1 where, within a relatively short period of time, they further divided by either progressive cleavage or successive bipartition. These divisions produced large numbers of merozoites and flagellated cells. This two-step procedure surpassed the previously described method of initiating cultures from hearts of infected eastern oysters because a much higher number of purified, largerP. marinascells could be obtained from a single infected eastern oyster.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0144:IMFTIO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-124.1.147

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor