dried fish
鮝 centers on fish that has been preserved by drying, specifically dried fish.
鮝 combines 龹 (likely a phonetic component) with 魚 (fish) to express the idea of dried fish. The exact historical development is uncertain.
The top 龹 looks like a bundle of sticks tied together, and the bottom 魚 is a fish. Imagine fish tied to a drying rack: 鮝 is dried fish.
For ショウ, picture a dried fish being shown at a market: show -> ショウ, and the fish is displayed for sale.