Can I use a crossbow in a muzzleloader only season? If not why It is a lesser weapon

Answer:

It states in the Big Game Rules: During a muzzleloader-only season, it is illegal to pursue or kill a big game animal with any firearm, muzzleloading pistol, or weapon other than a muzzleloading rifle or musket. 

A crossbow isn't considered a "lesser weapon" according to Fish and Game rules.