Dan Giammona, City of Sac Superintendant for Parks Maintenance (last time I checked) would be a good person to contact regarding the fish, other water life, and the water in Southside Park Lake: dgiammona@cityofsacramento.org. The State Dept. of Fish & Game used to be the ones stocking the lake, but that has been intermittent over the years. Not sure of current status. Contact (again, last I checked) was Joe Ferreyra (spelling?) 358-1644.
This story started as dummy content for a demo video. I got some response and now I think I will have to write a story about fishing in the lake. crazy.
I have a few stories gathered from old-time Southside Park residents on just that subject...there used to be fishing contests, with prizes for the biggest fish and smallest fish caught! Let me go check my files!