mandarin fish
鱖 refers specifically to the mandarin fish, a type of freshwater fish. The meaning is narrow and concrete, with no broader conceptual center beyond this single species.
鱖 combines 魚 (fish) with 厥, which likely provides the sound. The character was created to name a specific fish species.
The left side 魚 means fish, and the right side 厥 looks like a complex net or trap. Picture a special net used to catch the prized mandarin fish.
For ケイ, imagine a mandarin fish leaping out of the water like a graceful ray of light: the ray-like leap cues ケイ.