They would fall under fur-bearers regulations. Otters do require a CITES tag. If you shoot one, you have to take it to a TPWD law enforcement office and get the CITES tag (I want to say within 90, but I am not staring at the regulation).
Honestly, we don't know that much about their population. In general they are a species of concern, hence the CITES tag. They are pretty sensitive to water quality. They do seem to be expanding their range, but in reality, they may just be reinhabiting old range.
[This message has been edited by ursusguy (edited 1/28/2011 5:55p).]