The Mekar River is a location from The Legend of Zelda: Breath of the Wild. It is a river surrounding the Lost Woods in the Great Hyrule Forest region of Hyrule. The Mekar Island can be found in the river. Link can fish Stealthfin Trout here.
The name for Mekar River along with Mekar Island like many locations come from someone or something from a previous installment. Mekar River and Mekar Island come from the sage Makar, from The Wind Waker.