The tule perch Hysterocarpus traskii is a surfperch (Embiotocidae) native to the rivers and estuaries of central California, United States of America. It is the sole member of its genus, and the only freshwater surfperch. They are fish of the lowlands, inhabiting lakes, sloughs, streams, and rivers, generally in areas with beds of vegetation or overhangs. They generally gather in groups, sometimes in large numbers. Their diet is primarily small invertebrates sucked up from the bottom or picked from the midwater column. The two subspecies of tule perch recognized by FishBase are: