This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鱃 combines 魚 (fish) with 羞, which likely contributes the sound. The exact historical development is uncertain.
The left side is a fish 魚 and the right side 羞 looks like a hand offering something. Imagine a fish being offered, but its exact meaning remains unclear.
For シュウ, picture a fish being shooed away: shoo -> シュウ, as if the fish is being offered but then shooed off.