Fish measurement is the measurement of the individual fish and other parts of their anatomy . These data are used in many areas of ichthyology , including taxonomy and fisheries biology.
- Standard length ( SL ) is the length of a fish measured from the tip of the end of the last vertebra or the posterior end of the middle portion of the hypural plate. Simply put, this measurement excludes the length of the caudal (tail) end . 
- Total length ( TL ) is the length of a fish measured from the tip of the end of the caudal fin, usually measured with the lobes compressed along the midline. It is a straight-line measure, not measured over the curve of the body. 
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. 
Total length measurements are used in a slot and minimum landing size regulations.
In addition, fishery biologists often use a third measure in fishes with forked tails:
- Fork length ( FL ) is the length of a fish measured from the tip of the end of the middle caudal end rays and is used in fishes in which it is difficult to tell where the vertebral column ends. 
Other findings that may be taken include the lengths of various ends, the lengths of end bases, the length of the snout to various points on the body, and the diameter of the eye. 
- Ichthyology terms
- Standard weight in fish
- Jump up^ ” Term: standard length ” . FishBase.org . 2004-11-18 . Retrieved 2015-08-18 .
- ^ Jump up to:a b ” Term: total length ” . FishBase.org . 2004-11-18 . Retrieved 2015-08-18 .
- Jump up^ ” Term: fork length ” . FishBase.org . 2004-11-18 . Retrieved 2015-08-18 .
- Jump up^ “Standard Measurements of Bony Fish Diagram” . Florida Museum of Natural History Ichthyology Department . Retrieved 2007-06-06 .