Standard length and Total length

When it comes to fish, we measure them in one of a few ways. The first is Standard length (or SL), which measures from the tip of the snout to either the posterior end of the last vertebra, or the midlateral portion of the hypural plate. In layman’s terms, it’s the length of the fish minus the tail fin.

The second is Total length (or TL) which goes from the tip of the snout to the end of the longest lobe of the caudal fin. Because some fish have elongated tail find (think swordtails) they might have an incredible TL but only a short SL.

A third method is Fork length (or FL) which measures from the tip of the snout to the end of the middle (short) caudal fin rays. Fork length is only really used in cases where it’s hard to tell where the vertebrae end.