It would appear they do have the authority to check your boat, and or vehicle without a warrant.

Here is the text of RCW 77.15.080
Fish and wildlife officers -- Inspection authority.

Based upon articulable facts that a person is engaged in fishing or hunting activities, fish and wildlife officers have the authority to temporarily stop the person and check for valid licenses, tags, permits, stamps, or catch record cards, and to inspect all fish and wildlife in possession as well as the equipment being used to ensure compliance with the requirements of this title.

[2000 c 107 § 233; 1998 c 190 § 113.]

Wes