Because it sometimes happens that vivacious fishes, or those capable of surviving a long time out of water, are conveyed to a distance by birds, and left without being killed, on rocks or fields. - Fleming.
Because of the quality of the food on which they have subsisted. This is only conjecture, but is supported by the history of the mussel and the oyster, which owe their occasional noxious qualities to the zoophytes on which they feed.
The poisonous qualities of some shell-fish are, however, attributed by writers on their dietetic properties, to other causes, as we have already shown.*
* See Domestic .Science, page 45.
Because, in forsaking the deep water, and approaching a suitable spawning station, they leave the sea altogether for a time, ascend the rivers and their tributary streams, and having deposited their eggs, return again to their usual haunts. Even certain species of fish, inhabiting lakes, as the roach, betake themselves to the tributary streams, as the most suitable places for spawning.
Because fish can bear cold much better than heat.
Because it is light, and easily digested; but, for the same reason, it is unsuitable food for those engaged in laborious occupations.
Because a great deal of the oxygen in the air contained in the water, is necessarily consumed by the germination and growth of the aquatic plants, and the respiration of the infusory animalculae. In all cases, when the air of the atmosphere, or that which the water contains, is impregnated with noxious particles, many individuals of a particular species, living in the same district, suffer at the same time.
Because the water is then deprived of its atmospheric air, by means of which fishes carry on their respiration.
Because the luminousness appears to be caused by the infusory animalculae, with which water abounds. - Canton, Phil. Trans.
Because the milt and roe are then ripening. After the fish have deposited the spawn, the flesh becomes soft, and loses much of its peculiar flavour. This is owing to the disappearance of the oil or fat from the flesh, it having been expended in the function of reproduction.
When in season, the thick muscular part of the backs, as it contains the smallest quantity of oil, is inferior in flavour or richness, to the thinner parts about the belly, which are esteemed by epicures, as the most savoury morsels.