SB 2.10.42

sa evedaṁ jagad-dhātā
 bhagavān dharma-rūpa-dhṛk
puṣṇāti sthāpayan viśvaṁ
 tiryaṅ-nara-surādibhiḥ
Synonyms: 
saḥ — He; eva — certainly; idam — this; jagat-dhātā — the maintainer of the entire universe; bhagavān — the Personality of Godhead; dharma-rūpa-dhṛk — assuming the form of religious principles; puṣṇāti — maintains; sthāpayan — after establishing; viśvam — the universes; tiryak — living entities lower than the human beings; nara — the human beings; sura-ādibhiḥ — by the demigodly incarnations.
Translation: 
He, the Personality of Godhead, as the maintainer of all in the universe, appears in different incarnations after establishing the creation, and thus He reclaims all kinds of conditioned souls amongst the humans, the nonhumans and the demigods.
Purport: 

The Supreme Personality of Godhead Viṣṇu incarnates Himself in different societies of living entities to reclaim them from the clutches of illusion, and such activities of the Lord are not limited only to human society. He incarnates Himself even as a fish, hog, tree and many other forms, but less intelligent persons who have no knowledge of Him deride Him even if He is in human society as a human being. The Lord therefore says in the Bhagavad-gītā (9.11):

avajānanti māṁ mūḍhā
 mānuṣīṁ tanum āśritam
paraṁ bhāvam ajānanto
 mama bhūta-maheśvaram

As we have already discussed in the previous verses, it is concluded that the Lord is never a product of the material creation. His transcendental position is always unchanged. He is the eternal form of knowledge and bliss, and He executes His almighty will by His different energies. As such, He is never the subject of reactions for any of His acts. He is transcendental to all such conceptions of actions and reactions. Even if He is visible in the material world, the exhibition is only of His internal energy, for He is above the good and bad conceptions of this material world. In the material world the fish or the hog may be considered lower than the man, but when the Lord appears as a fish or hog, He is neither of them in the material conception. It is His causeless mercy that He appears in every society or species of life, but He is never to be considered one of them. Conceptions of the material world such as good and bad, lower and upper, important and insignificant, are estimations of the material energy, and the Supreme Lord is transcendental to all such conceptions. The words paraṁ bhāvam, or transcendental nature, can never be compared to the material conception. We should not forget that the potencies of the Almighty Lord are always the same and do not decrease because the Lord assumes the form of a lower animal. There is no difference between Lord Śrī Rāma, Lord Śrī Kṛṣṇa and His incarnations as a fish and hog. He is all-pervading and simultaneously localized at any and every place. But the foolish person with a poor fund of knowledge, for want of that paraṁ bhāvam of the Lord, cannot understand how the Supreme Lord can take the form of a man or a fish. One compares everything to one’s own standard of knowledge, as the frog in the well considers the sea to be like the well. The frog in the well cannot even think of the sea, and when such a frog is informed of the greatness of the sea, it takes the conception of the sea as being a little greater than the well. As such, one who is foolish about the transcendental science of the Lord will find it difficult to understand how Lord Viṣṇu can equally manifest Himself in every society of living entities.