On the ocean side, most saltwater fish with minimum size limits are measured to total length, but there are some that are measured to fork length instead (e.g. bonito, albacore, barracuda and yellowtail). Fork length is the straight-line distance from the tip of the head to the center of the tail fin (CCR Title 14, Section 1.62). So again, lay the fish flat on its side, pinch the mouth closed and take your measurement from the tip of the head to the center of the fork of the tail. These are the only two measurements that you will need to know for the purposes of the regulations when measuring whole fish.