| Autor: |
Mottley, C. McC., Rayner, H. J., Rainwater, J. H. |
| Zdroj: |
Transactions of the American Fisheries Society; January 1939, Vol. 68 Issue: 1 p336-343, 8p |
| Abstrakt: |
The volume and number of organisms per unit area of bottom is now widely used in determining the relative richness of streams. The food grade determined by the volume of organisms in square-foot samples is an important factor in the calculations used to determine the number of fish to plant per mile of stream. In spite of the fact that thousands of dollars may be wasted by making an incorrect estimate no one seems to have investigated some of the fundamental problems involved in the determinations. Some of these problems are: (1) What is an adequate sample; how many square-foot samples are needed to afford a reliable estimate? (2) What is the seasonal fluctuation in food organisms; can samples taken at different seasons be used as reliable estimates? (3) Do all the organisms taken in the samples become available to the same extent to the particular species of fish a stream is to support. Preliminary findings of the Laboratory have shown that there is considerable variation in the food grade as determined by a number of workers in one spot at one time and that floods and high water may completely alter the picture. |
| Databáze: |
Supplemental Index |
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