Fish measurement

Standard length (SL) is the length of a fish measured from the tip of the snout to the posterior end of the last vertebra or to the posterior end of the midlateral portion of the hypural plate.

[1] Total length (TL) is the length of a fish measured from the tip of the snout to the tip of the longer lobe of the caudal fin, usually measured with the lobes compressed along the midline.

[2] Standard length measurements are used with Teleostei (most bony fish), while total length measurements are used with Myxini (hagfish), Petromyzontiformes (lampreys) and usually Elasmobranchii (sharks and rays), as well as some other fishes.

[2] Total length measurements are used in slot limit and minimum landing size regulations.

Fishery biologists often use a third measure in fishes with forked tails, called Fork length (FL), the length of a fish measured from the tip of the snout to the end of the middle caudal fin rays, and is used in fishes in which it is difficult to tell where the vertebral column ends.