Abstract
An improved version of rotatory-flow apparatus is described, allowing tests of fitness with fish of different size at constant temperature. Cod ( Gadus morrhua, L.) was used as experimental animal, and its treatment and behaviour during different phases of the test are described in some detail. Each test results in determination of the “critical rev min −1” at which the fish is just brought to rotate with the water. The mean of a series of 10 critical rev min −1 with the same fish, multiplied by the interior circumference of the rotational tube used, gives the “critical peripheral velocity” of the specimen. Critical peripheral velocities of a sample of fish, plotted against the standard length of the fish, arrange themselves along a straight line which intersects the vertical axis near the origin. Divided by the corresponding standard lengths the critical peripheral velocities give “reaction quotients”, the mean of which describe the reaction of the whole sample of fish. Optimal experimental conditions have been found by investigating the effects of systematic variation in streaming velocity, relationship between rotational tube diameter and fin-breadth, temperature, and effects of repetition of test-series on successive days etc. on the results of testing.
Published Version
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