This small river is actually called Þríhyrningsá because it flows from Þríhyrningsvatn, but its name changes before it flows into Jökulsá á Fjöllum. It has plenty of small char and there are some reports of bigger fish. There can be quite good fishing where Arnardalsá flows into Jökulsá. The char population in this area is not so large that it can withstand a lot of pressure and therefore it makes good sense to approach fishing with moderation in mind. Those who want to explore fishing possibilities in this area are advised to talk to landowners in Möðrudalur or at Brú in Jökuldalur.