From Holocron - Star Wars Combine
|Average Height||1.5 meters |
|Skin color||Blue or green |
|Distinctions||Venom-tipped claws |
|Average lifespan||Up to 100 standard years |
|Known Members||List of known Selkath|
Biology and appearance
Selkath are the native species of the planet Manaan. An amphibious species, they are excellent swimmers and have the ability to hold their breath for very long periods of time when under water. Though they resemble anthropomorphic catfish and have aqua-coloured skin, they do not have gills. All members of the Selkath race have venom-tipped, retractable claws. Similar to the Wookiees, the use of these claws in any form of combat is considered dishonourable and a sign of madness.
Their mouths are bracketed by cephalic lobes. They tend to stroke these during conversation, analogous to the Human habit of stroking facial hair, such as mustaches. 
Society and culture
In ancient times, their ancestors were slaves to the Rakata, but gained their independence after the Infinite Empire's collapse. Since then, the Selkath have opted to remain neutral in times of intergalactic conflict. Their laws are very harsh, and it is not uncommon for violence or attempts to compromise Manaan's neutrality to be punished by death. The Selkath haven't forgotten their time as slaves under the Rakatans either; most Selkath seem to have an innate hatred toward slavery and the subjection of weaker species to those who have the power to force their own will upon them.
On Manaan, the Selkath have only one city above land, the planet's capital, Ahto City. This was done so that foreign dignitaries and interstellar visitors would feel comfortable, as the rest of the cities the Selkath inhabit are protected by the vast seas in which they exist.
In Selkath culture, a large female firaxan shark, known as the Progenitor, is seen as either a religious deity, or even an early evolutionary step in the Selkath chain. While some hold a reverence or even worship her as a mother goddess, others have embraced some of the other religious thoughts that are present throughout the galaxy. One of such faiths rose to prominence after the events of the Jedi Civil War, a Force tradition known as the Order of Shasa. While they have many members in Manaan, galaxy-wide their numbers are very small.
References:  - http://starwars.wikia.com/wiki/Selkath