(Corrects name in paragraph 8, Hiroyuki Ukeda not Hideyuki Ukeda) By Kantaro Komiya NAKATOSA, Japan (Reuters) -For half a century, Takeo Nakajo has been catching katsuo, or skipjack tuna – indispensable in Japanese cuisine whether eaten raw, dried or used as a base for the broth. But he and other fishermen in Kure, in Kochi prefecture in southwest Japan, have seen something worrying in the past two years – an unprecedented number of unusually fatty katsuo. While heavier katsuo means more money, locals and experts say it indicates climate change and a risk for katsuo numbers already under threa…