hehe, this is a tough so here are a couple more hints. Its only found in California's Central Valley and its common name contains the name of a city in California, starts with an s.
You threw me with this statement, your fish was the Sacramento splittail (Pogocichthys macrolepidotus).
But aren't the clear Lake splittails (P. ciscoides) still around?
By the way, if you do a web search for splittail be very careful what you open, I am going to have to do a dump on my computer and reload from scratch as one site sent me an invasive program called spyfalcon or security center, it is a virus program selling antivirus ware.
Messiner, yours is the long-tail knifefish (Sternopygus macrurus) and the pic is by Galvus/Mojica/Camargo.
As I mentioned I am having problems with the computer so go ahead and post another.