they are all over the river but I have only ever caught them by the dashshield dam and on the lower side of the back channel. Its freaky as hell because they look so prehistoric and dinosaur like. Also sucks because the bigger ones will take your bait, hooks, weight and everything in one bite.
the most hilarious thing is watching people who have never seen a gar before catch them down there. People wig the fuck out because they think they caught the lock ness monster or something.