This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鮄 combines 魚 (fish) with 弗, which likely contributes a phonetic element. The exact historical development is uncertain.
With 魚 on the left, 鮄 likely relates to a type of fish, but its specific meaning is unclear. Picture a fish with the right side 弗 as a distinctive marking.
For フツ, imagine a fish with feet (フツ sounds like 'foots') walking out of water: foots -> フツ.