the sheat fish
鮧 refers specifically to the sheatfish, a type of catfish. Its meaning is narrow and concrete, centered on this particular fish.
鮧 combines the fish radical 魚 with 夷, which likely provides the sound. The character was created to name the sheatfish.
The fish radical 魚 on the left tells you it's a fish. The right side 夷 looks a bit like a catfish's whiskers and flat head, so picture a sheatfish swimming by.
For イ, imagine an eel-like sheatfish: the 'e' sound in 'eel' cues イ, and the fish shape reinforces the meaning.