This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鰏 combines 魚 (fish) with 畐, which likely contributes the sound. The exact historical development is uncertain.
The left side is 魚 (fish), and the right side is 畐. Without a clear meaning, picture a rare fish with a full, rounded body like the shape of 畐.
For ヒョク, imagine a fish named Hyoku that is so rare, saying its name feels like a special hook: Hyoku -> ヒョク.