[header] How to measure fish [title] Lay an extended tape measure on a flat surface. [step] Extend the tape measure so it's visibly longer than the fish you're measuring. Whenever you're measuring the length of a fish, you want to lay a tape measure flat as opposed to running it over the top of the fish. 
Going over the top of the fish with the tape measure can distort the measurement. [title] Lay the fish flat next to the tape measure.