In the first skanda, third chapter of Bhagavatha has the sloka
एते चांशकला: पुंस: कृष्णस्तु भगवान् स्वयम् ।
इन्द्रारिव्याकुलं लोकं मृडयन्ति युगे युगे ॥
ISKCON followers interpret this as below.
All of the above-mentioned incarnations are either plenary portions or portions of the plenary portions of the Lord, but Lord Śrī Kṛṣṇa is the original Personality of Godhead. All of them appear on planets whenever there is a disturbance created by the atheists. The Lord incarnates to protect the theists.
How do Shrivaishnavas and Madhvas interpret this sloka?