A scientist made three observations: (1) in the world’s temperate zones, food is more plentiful in the ocean than it is in fresh water; (2) migratory fish in temperate zones generally mature in the ocean and spawn in fresh water; and (3) migratory fish need much nourishment as they mature but little or none during the part of their lives when they spawn. ██ ███ █████ ██ █████ █████████████ ███ █████████ ██████████ ███ ██████████ ████ ████ ████████████ ██ █ ███████████ ██████ ██ ███ █████████ ██ █████████ █████ ████████████ ███ █████████ ███████ ████ ██ ███ ███████ █████████ ████ █████████ ██████ ██ █████ █████ ███ █████ ██ ███ ██████