How size is measured

[Daragh]

Just wondering how the size shown on the species pages are measured. Is it from the tip of the nose to the end of the caudal peduncle or to the centre of tail, e.g. if it is a forked tail it is measured to the centre of the fork???

Daragh

[Silurus]

Size is given as standard length, which is the distance from the tip of the snout to the base of the caudal fin (realistically, it's usually taken from the tip of the snout to where a crease forms at its base when the caudal fin is flexed).

[Suckermouth]

Actually, I don't think any of the measurements on this site are fork length...

[Bas Pels]

There is sl - standard length - which is bodylength, as Silurus described
Then there is also total length, which includes the tail fin as well. The fin, opened normally, extends itself to a certain distance from the tail - along the axis of the body

total length does seem the best for us, aquarists, but for scientists, working with dead, preserved fish, the tailfin is easily damaged, and therefore sl is the standard

In many cases tl is 20 % or so more then sl, unless we are talking about large finned fish or so - such as a sworttail (Xiphophorus helleri, not a catfish)

[Daragh]

Excellent, thanks for the replies, I just wanted to confirm my understanding of where the measure meant was to.

Daragh

[Coryman]

Daragh,

If you are looking at fishes to be presented at open shows, then the size standards used by the various associations are always in standard length (SL). Tip of snout to caudal peduncle.

Ian

[Daragh]

Yes Ian that is what I was looking for, but I just wanted to confirm that the definition here of SL was what I expected and it is. Happy days.

Daragh