نتایج جستجو برای: Poisson’s Ratio

تعداد نتایج: 502658  

Journal: :Sciences, eaux & territoires 2023

S'il ne fait aucun doute que la biodiversité décline à l'échelle mondiale, il est surprenant de constater les dynamiques locales peuvent être contrastées. Nous possédons une compréhension encore incomplète façon dont écosystèmes évoluent sous l'effet du changement global. Ici, nous avons cherché caractériser dynamique temporelle récente des rivières en France, d'un point vue taxonomique et fonc...

2012
David C. Hardie D. N. Hebert

Fishes possess both the largest and smallest vertebrate genomes, but the evolutionary significance of this variation is unresolved. The present study provides new genome-size estimates for more than 500 species, with a focus on the cartilaginous and ray-finned fishes. These results confirm that genomes are smaller in ray-finned than in cartilaginous fishes, with the exception of polyploids, whi...

2009
S. V. LeBourdais D. Esler

We investigated interactions among harlequin ducks (Histrionicus histrionicus (L., 1758)), fish, and their shared aquatic insect prey. We measured flow variability, benthic aquatic prey abundance, fish presence, and breeding density of harlequins on eight rivers in the Southern Coast Mountain Range in British Columbia, Canada, in 2003 and 2004. Rivers with lower flow variability had higher abun...

2001
José Luiz Attayde

The effects of planktivorous fish on phytoplankton through nutrient recycling and zooplankton herbivory were experimentally separated and their relative importance quantified in a eutrophic humic lake. Natural phytoplankton assemblages were incubated in nutrient-permeable chambers placed inside enclosures with or without fish. Outside these chambers, phytoplankton were exposed to zooplankton he...

2003
Edward D. Weber Kurt D. Fausch

Competition between hatchery-reared and wild salmonids in streams has frequently been described as an important negative ecological interaction, but differences in behavior, physiology, and morphology that potentially affect competitive ability have been studied more than direct tests of competition. We review the differences reported, designs appropriate for testing different hypotheses about ...

2003
Carol Seals Price Carl B. Schreck

Two experiments were conducted to determine the effects of a mild or severe stressor on the saltwater preference of juvenile spring chinook salmon (Oncorhynchus tshawytscha). To observe the response of fish to an overhead threat, we presented stressed fish with an avian predator model in the second experiment. Experiments were conducted in 757-L tanks containing a stable vertical salinity gradi...

2013
Andrew T. Jackson Alphonse Adite Katherine A. Roach Kirk O. Winemiller

In the Ouémé River, Africa, whedo (artificial pond) aquaculture on the floodplain is an important method of fishery production. We surveyed fishes in whedos and adjacent main-channel and floodplain habitats during the receding-water period (December 2010 – January 2011) and analyzed carbon ( 13C) and nitrogen ( 15N) stable isotope ratios of fish and primary producer tissue samples to investigat...

2003
Alex De Robertis Clifford H. Ryer Adriana Veloza Richard D. Brodeur

Contrast degradation theory predicts that increased turbidity decreases the visibility of objects that are visible at longer distances more than that of objects that are visible at short distances. Consequently, turbidity should disproportionately decrease feeding rates by piscivorous fish, which feed on larger and more visible prey than particle-feeding planktivorous fish. We tested this predi...

2000
Bret C. Harvey Rodney J. Nakamoto Jason L. White

To improve understanding of the significance of large woody debris to stream fishes, we examined the influence of woody debris on fall and winter movement by adult coastal cutthroat trout (Oncorhynchus clarki) using radiotelemetry. Fish captured in stream pools containing large woody debris moved less than fish captured in pools lacking large woody debris or other cover. Fish from pools lacking...

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