dried fish
鱐 centers on dried fish as a preserved food. The meaning is narrow and concrete, referring specifically to fish that has been dried.
鱐 combines 魚 (fish) with 肅, which likely contributes the sound. The character is rare and its exact historical development is uncertain.
The left side is a fish 魚, and the right side 肅 looks like a hand holding a brush over a container, suggesting careful preparation. Picture a fish being carefully dried and preserved.
For シュク, imagine a chef saying 'shook' as he shakes salt onto the fish before drying it: shook -> シュク.