Tule Perch

A pregnant female tule perch, Hysterocarpus traskil (top), with her recently-birthed offspring (bottom). This fish was found May 2011 at Liberty Island, a flooded-agricultural tract in the northwest San Francisco Bay Delta. Tule perch do not lay eggs, but instead give live birth. The U.S. Geological Survey studies native species like this to evaluate the importance of tidal wetlands to native fishes.