Get yourself a good road map that shows the aqueduct. Where it stops and goes under ground there is usually a pumping station. Also you can try Google earth. It is a virtual map you can use to get satellite views. Before the station and where the water comes out are good spots to try. I've never heard of a sturgeon in the duct but since it starts up at the Delta, who knows. My sons and I have caught stripers, cats, and carp.
If you need a specific spot catfisher, send me an email, addy listed in my profile, and I can help you out, don't want to post them in a public forum.