I am a fish
Remove my first, and I might be a thief
Remove my second, and you will divide
Remove my third, and you will see much pain
Remove my fourth, and I am measured by metres
Remove my fifth, and nothing is left
Remove my fifth, and you see what I do
Remove my fourth, and you have space to think
Remove my third, and I will sound infantile
Remove my second, and things fall
Remove my first, and nothing is left
What am I?