Fr. Benedict Croell OP, another Dominican Friar has answered the question "Why is fish okay?" for me.
used to be that Fish was the cheapest food...not the case any more or in certain parts of the world...also the Lenten fast is only Ash Wed and Good Fri when it is obligatory...Fridays of Lent there is obligatory abstinence from meat
see Fr. Serpa's note on this page: http://forums.catholic.com/showthread.php?t=137581