By Ridzki R. Sigit CENTRAL ARU, Indonesia — One afternoon last November, Natanel Ginobal, 67, drove his motorboat to check the mud crabs caught by the traps he had installed earlier the day. He had to move quickly before the tide started receding and made it much more difficult for him to harvest his catch of the day. Natanel had set 15 traps between the roots of mangrove plants (Rhizophora) in a narrow river inlet that required him to switch from the motorboat and use a smaller boat to maneuver through the mangrove gaps. This is a common practice among the many mud crab fishers, like Natanel,…