loach (fish)
鰌 refers specifically to the loach, a small freshwater fish. The meaning is narrow and concrete, centered on this particular fish.
鰌 combines the fish radical 魚 with 酋, which likely provides the sound. The character was created to name the loach fish.
The left side is a fish 魚, and the right side 酋 looks like a container with a lid. Imagine a loach being kept in a special lidded container.
For シュ, picture a loach swimming into a shoe: shoe -> シュ, and the loach hides inside.
loach (any fish of family Cobitidae)
Japanese eight-barbel loach (Lefua echigonia)
blotched snakehead (Channa maculata)
Niwaella delicata (species of loach)
a fox is not taken twice in the same snare; there are no birds in last year's nest; there aren't always loach under the willow tree; good luck does not always repeat itself
a fox is not taken twice in the same snare; there are no birds in last year's nest; there aren't always loaches under the willow tree
Cobitis takatsuensis (species of loach)
Japanese striped loach (Cobitis biwae)