Marcel says the Moustache is so yhat the rubber doesn’t larve a mark on the grey paint on navy vessels. The said the lower bars on the bow are for maneuvering the submarine’s as their hull is round.

@Ronald DON'T REMEMBER THE TECHNIACAL NAME BUT IT'S PURPOSE IS NOT TO DAMAGE THE PAINT WORK ON CANADIAN NAVAL SHIPS. THIS TUG IS USED TO DIRECT SHIP INTO HARBOUR AND DOCKING. COLD MOVE OF RCN SHIPS USE THIS TUG FOR CHANGE OF DIRCTION WHILE LARGER TUGS ADRE USED FOR MOVING POWER. PETTY OFFICER FIRST CLASS ELGIN SMITH CD RET'D

@Ronald
My guess is they're traction bars or grip rails to improve contact when pushing barges, preventing the tug from slipping sideways under heavy loads.
If not that, perhaps they're intended as ice-deflecting rails for operations in colder waters