. Bulletin of the United States Fish Commission. Fisheries -- United States; Fish-culture -- United States. ELECTRIC FISH SCREEN 107 INFLUENCE OF WATER RESISTIVITY ON THE PARALYSIS-VOLTAGE GRADIENT A series of paralysis-voltage gradient tests were made with chinook-salmon fingerlings, using water varying in resistivity from to 10,030 ohms per inch cube to determine the influence of water resistivity upon the paralysis-voltage gradient. The results of these tests (Nos. 31 to 37, inclusive) are summarized in Table 3 and shown graphically in Figure 7. The water resistivity was adjusted to th
. Bulletin of the United States Fish Commission. Fisheries -- United States; Fish-culture -- United States. ELECTRIC FISH SCREEN 107 INFLUENCE OF WATER RESISTIVITY ON THE PARALYSIS-VOLTAGE GRADIENT A series of paralysis-voltage gradient tests were made with chinook-salmon fingerlings, using water varying in resistivity from to 10,030 ohms per inch cube to determine the influence of water resistivity upon the paralysis-voltage gradient. The results of these tests (Nos. 31 to 37, inclusive) are summarized in Table 3 and shown graphically in Figure 7. The water resistivity was adjusted to the desired value in these tests by first making a salt (NaCl) water solution that had the resis- tivity of sea water; fresh water was then added to obtain the desired increments in resistivity. These data show a rapid change in the voltage gradient required to paralyze fish at low values of water resistivity, a slower change at intermediate resistivities, and a rapid change again at high resistivities. Tlie range of resistivities covered by this investigation, it should be noted, is from sea water to high-resistivity mountain-stream water, and in this range the minimum paralysis-voltage gradient changes from to volts per inch, or times. It is necessary then to mtro- duce a water-resistivity correction factor in the previous equation. It may now be written „ TF 9 = —f where g = voltage gradient per inch to produce paralysis, L = length of fish in inches, and TF= correction factor for water resistivity. (See Table 4 for values of W for different water resistivities from 10 to 10,000 ohms per inch cube.) Table 3.—Influence of water resistivity on the voltage gradient required to paralyze chinook-salmon fingerlings inches long when subjected to a uniform electric field in water, the resistivity of which was adjusted to the desired value by adding fresh water to a salt (NaCl) solution having an initial resistivity of ohms per inch cube and at a temp
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