BAZ RATNER FISHERMEN on the shores of Kenya's Lake Turkana, the world's biggest desert lake, have no doubt about what is to blame for their dwindling fish stocks: a giant hydroelectric dam built by Ethiopia on the River Omo, which feeds the lake. "We are now seeing Nile perch stocks drastically reduce," said fisherman Fitbo Lalukol. He says boats must sail much further out into the lake to get a good catch. Officials at Ethiopia's ministry of water, irrigation and energy did not respond immediately to a Reuters request for comment on the fishermen's claims. Complaints about the Omo dam…