Pattern and prevalence of predator damage on adult Atlantic salmon,Salmo salar L., returning to a river system in north-east Scotland     

P. M. THOMPSON  F. MACKAY 《Fisheries Management and Ecology》1999,6(4):335-343

Abstract There remains considerable debate over the impact of predation upon Atlantic salmon, Salmo salar L., populations. The pattern and prevalence of predator damage on salmon returning to a river system in North-east Scotland were recorded. Overall, 214 (19.5%) out of 1099 fish sampled were damaged, and 10 distinct categories of damage were identified. Measurements of scratches indicated that the damage was caused by a number of different factors. In particular, damage typically attributed to seals was suggested to be the result of attacks by odontocete cetaceans. These results highlight the multispecies nature of interactions between salmon and their predators, but suggest that damage levels may be of limited use in assessing the impact of different predators on salmonid population dynamics.  相似文献   

Distribution of thiobacillus ferrooxidans and leptospirillum ferrooxidans: implications for generation of acid mine drainage   总被引：1，自引：0，他引：1  

MO Schrenk  KJ Edwards  RM Goodman  RJ Hamers  JF Banfield 《Science (New York, N.Y.)》1998,279(5356):1519-1522

Although Thiobacillus ferrooxidans and Leptospirillum ferrooxidans are widely considered to be the microorganisms that control the rate of generation of acid mine drainage, little is known about their natural distribution and abundance. Fluorescence in situ hybridization studies showed that at Iron Mountain, California, T. ferrooxidans occurs in peripheral slime-based communities (at pH over 1.3 and temperature under 30 degreesC) but not in important subsurface acid-forming environments (pH 0.3 to 0.7, temperature 30 degrees to 50 degreesC). Leptospirillum ferrooxidans is abundant in slimes and as a planktonic organism in environments with lower pH. Thiobacillus ferrooxidans affects the precipitation of ferric iron solids but plays a limited role in acid generation, and neither species controls direct catalysis at low pH at this site.  相似文献   

Design and fabrication of topologically complex, three-dimensional microstructures     

RJ Jackman  ST Brittain  A Adams  MG Prentiss  GM Whitesides 《Science (New York, N.Y.)》1998,280(5372):2089-2091

Two concepts for use in the fabrication of three-dimensional (3D) microstructures with complex topologies are described. Both routes begin with a two-dimensional (2D) pattern and transform it into a 3D microstructure. The concepts are illustrated by use of soft lithographic techniques to transfer 2D patterns to cylindrical (pseudo-3D) substrates. Subsequent steps-application of uniaxial strain, connection of patterns on intersecting surfaces-transform these patterns into free-standing, 3D, noncylindrically symmetrical microstructures. Microelectrodeposition provides an additive method that strengthens thin metal designs produced by patterning, welds nonconnected structures, and enables the high-strain deformations required in one method to be carried out successfully.  相似文献