1. It has already been observed that fish migrate from the deep water to the coast, and from the coast to the deep water, in order to avoid the excesses of cold and heat. Those that frequent the neighbourhood of the coast are better than those from deep water, for the feeding grounds are better and more abundant. For wherever the sun strikes the plants are more frequent, and superior, and more delicate, as in gardens, and the black shore-weed grows near the land, and the other kinds rather resemble uncultivated plants. The neighbourhood of the coast is also more temperate, both in heat and cold, than the rest of the sea; for which reason the flesh of fish which live near the shore is more compact, while that of fish from deep sea is watery and soft. The sinodon, cantharus, orphos, chrysophrys, cestreus, trigla, cichla, dracon, callionymus, cobius, and all the rock fish live near the shore. The trygon, selache, the white congers, the channa, erythrinus, and glaucus inhabit deep water. The phagrus, scorpius, the black conger, the muræna, and coccyx occupy either situation indifferently.
2. They vary also in different places; as in the neighbourhood of Crete the cobius and all the rock fish are fat. The tunny also becomes good again after Arcturus, for it is not tormented by the œstrus after that period; for which reason also it is inferior during the summer. In lakes near the sea also there are several kinds of fish, as the salpa, chrysophrys, trigla, and nearly all the rest. The amia also is found in such situations as in the vicinity of Alopeconnesus, and in the lake of Bistonis there are many fish. Many of the coliæ do not enter the Pontus; but they pass the summer and rear their young in the Propontis, and winter in the Ægean. The thynnus, pelamis, and amia enter the Pontus in the spring and pass the summer there, and so do nearly all the rhyades and the gregarious fish. Many fish are gregarious, and gregarious fish have a leader of the shoal.
3. They all enter the Pontus for the sake of the food (for the pasture is more abundant and superior, on account of the fresh water), and for fear of the large creatures, which are smaller there; and except the phocona and dolphin, there is no other found in the Pontus; and the dolphin is small, but when we leave the Pontus we find a larger dolphin. They enter this sea for the sake of food and rearing their young; for the situation is better for this purpose, and the fresh sweet water nourishes the young fry. When they have reared their young, and the fry begin to grow, they migrate immediately after the Pleiades. If the south wind blow during the winter, they leave the place more slowly; but with a north wind they swim faster, for then the wind helps them along. The small fry is captured in the neighbourhood of Byzantium, for they make no long stay in the Pontus.