Tule perch

The tule perch, Hysterocarpus traskii, is a surfperch of the family Embiotocidae and the only member of its genus. It is also the only freshwater surfperch, living in the streams, rivers, lakes and estuaries of central and northern California, with three subspecies in the Clear Lake, Russian River and Sacramento-San Joaquin drainages. It has a bluish or purple back, a pale belly and a pronounced hump in front of the dorsal fin, and it prefers cool, oxygenated water. It feeds on aquatic insects, crustaceans, zooplankton and plants. It is the only native freshwater fish of California that bears live young: females give birth to ten to sixty fully formed young each spring, after sperm stored from the previous summer fertilises the eggs in January. Most individuals live no more than five years, though some reach eight. Loss of habitat has reduced its abundance.