dried fish
鯗 centers on fish that has been dried for preservation, specifically dried fish as food.
鯗 combines 魚 (fish) with a component that likely contributed the sound and the idea of drying or preserving. The exact historical development is uncertain.
The bottom is 魚 (fish). The top looks like a rack or a drying frame. Picture fish laid out on a rack to dry in the sun: 鯗 is dried fish.
For ショウ, imagine a show of dried fish hanging on a rack: show -> ショウ, and the fish are drying in the display.