bream
鯿 refers specifically to a bream, a type of freshwater fish. The meaning is narrow and concrete, without broader abstract extensions.
鯿 combines 魚 (fish) with 扁, which likely contributes the sound ヘン. The character was created to name a specific fish species.
The left side 魚 means fish, and the right side 扁 looks like a flat, wide shape. Picture a flat-bodied bream swimming in a pond.
For ヘン, imagine a hen pecking at a bream by the water's edge: hen -> ヘン, and the fish is the bream.