This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鰑 combines 魚 (fish) with 昜, which likely contributes the sound. The exact historical development is uncertain.
The left side is a fish 魚, and the right side 昜 suggests a sound. Without a clear meaning, picture a rare, mysterious fish whose name is lost.
For ヨウ, imagine a yo-yo tied to a fish hook: yo -> ヨウ, and the fish 魚 on the left is caught by the yo-yo string.