This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 鮇 is uncertain. It combines 魚 (fish) with 未, but the original semantic or phonetic role of 未 in this character is not clearly established.
The left side is a fish 魚, and the right side is 未 (not yet). Picture a fish that has not yet been identified, so its meaning is uncertain.
For ビ, imagine a bee buzzing around the unidentified fish: bee -> ビ, and the fish remains a mystery.