I dont know how you could get them besides fishing ( I would check with your local Dnr), but have yhou thought of Sacramento Perch (awesome designs) or Sacramento Pikeminnows (Squawfish)? Both are Piscivores that get over 20 inches long and would be fun to watch and are native. I used to catch Sacramento Pikeminnows while fishing up north...pretty aggressive fish. California also has some large Sculpin and the Pacific Fat Sleepers.