why do fishes have scales?

The main reason is probably to give them some protection - a bit like armour.

In some fish - sticklebacks are a good example - you find that scales are much more developed and armour-like in populations where there are predators. Of course there's also a lot of variation between species and higher order taxa (e.g. sharks and rays have very different sorts of scales to most other fish). Some fish have very small scales (e.g. salmon and trout) others have very big ones (e.g. carp), and some fish don't actually have any (e.g., gobies, loaches).

Last edited by Alistair Wilson (1st Feb 2008 13:50:40)