Fish measurement
Measuring of individual fish and various parts of their anatomies
Fish and various parts of their anatomies are measured for data used in many areas of ichthyology, including taxonomy and fishery biology.
01Overall length
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. This measurement excludes the length of the caudal (tail) fin.
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. 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 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.
02Fin lengths and eye diameter
Other possible measurements include the lengths of various fins, the lengths of fin bases and the diameter of the eye.
Sources and credits
This article is adapted from the Wikipedia article “Fish measurement”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Grenadier basic external features.png by Thomas Linley, CC BY-SA 3.0
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