horse mackerel
鰺 centers on a specific fish: the horse mackerel. It is a narrow, concrete term without broader abstract extensions.
鰺 combines the fish radical 魚 with the phonetic component 參, which likely indicates the sound. The character was created to name the horse mackerel specifically.
The left side 魚 means fish, and the right side 參 looks like a complex net or trap. Picture a fish caught in an elaborate net: that's the horse mackerel.
For ソウ, imagine the horse mackerel being sewn (ソウ) into a net: sew -> ソウ, and the fish is trapped inside the complex right component.