This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鯟 is a rare character combining 魚 (fish) with 東, which may have been used as a phonetic component. The exact historical development is uncertain.
The left side is a fish 魚, and the right side is east 東. Picture a rare fish from the eastern seas whose name is written with this kanji, but its meaning is unclear.
For トウ, imagine a fish from the east (東, とう) swimming in the ocean: 東 -> トウ, and the fish 魚 reminds you it's a fish-related character.