Here is the law from DOJ concerning conceal carry while hunting fishing.
CARRYING A CONCEALED WEAPON WITHOUT A LICENSE
It is illegal for any person to carry a handgun concealed upon his or her person or concealed in a vehicle without a license issued pursuant to Penal Code section 26150 . (Pen . Code, § 25400 .) A firearm locked in a motor vehicle’s trunk or in a locked container carried in the vehicle other than in the utility or glove compart ment is not considered concealed within the meaning of the Penal Code section 25400; neither is a firearm carried within a locked container directly to or from a motor vehicle for any lawful purpose . (Pen . Code, § 25610 .)
The prohibition from carrying a concealed handgun does not apply to licensed hunters or fishermen while engaged in hunting or fishing, or while going to or returning from the hunting expedition . (Pen . Code, § 25640 .) Notwithstanding this exception for hunters or fishermen, these individuals may not carry or transport loaded firearms when going to or from the expedition . The unloaded firearms should be transported in the trunk of the vehicle or in a locked container other than the utility or glove compartment . (Pen . Code, § 25610
You can carry concealed per the above circumstances. California wardens are aware of this. Other LEO’s may not be. If you do this its a good idea to carry a copy of the law so as to avoid problems with an officer who is unaware of the law.