Because it brings the fish up, who know when rain is coming; and likewise brings down food, and makes the fish feed. But when the water is raised by a strong wind, the fish never run, as they are sure to find no increase in the spring-heads, which are their objects in running. - Sir H. Davy.
Because, though inconvenienced by the light, they do not then alarm the fish; whereas, if they fished with their backs to the sun, and it was not very high, their own shadows, and those of their rods, would be thrown upon the water, and the fish would be alarmed whenever a fly was thrown.
Thus, Cotton wishes for
A day, with not too bright a beam ; A warm, but not a scorching, sun.
Because, even in summer, it is of very low temperature, approaching to 40°, and it contains little or no vegetable food or insects, which the smaller fishes search for; and the larger fishes follow the smaller. We cannot judge of the senses of animals which breathe water - which separate air from water by their gills; but it seems probable, that as the quality of the water is connected with their life and health, they must be exquisitely sensible to changes in water, and must have similar relations to it, that an animal with the most delicate nasal organs has to air. - Sir H. Davy.
Because it not only obscures the vision of the fish, but, in a river much fished, changes the appearance of their haunts; large trouts almost always occupy particular stations, under, or close to, a large stone or tree ; and, probably, most of their recollected sensations are connected with this dwelling. - Sir H. Davy.
Because those which leave a particular dwelling at stated intervals, measure the distance they ought to travel, and return with regularity to their home. The sun appears to be their great regulator, as they are influenced by the changes which take place with his light and heat. Fishes, and other animals, which live in the sea, or search for food on its shores, appear to regulate themselves by the motions of the tide. The regularity of the crowing of the cock, has been long admired; but it appears difficult to point out the measure of time by which it is governed.* - Fleming.
* See Origins and Antiquities, Part III. p. 38.