Múlaá falls from Skriðuvatn in Suðurdalur, in of Skriðdalur, and is called Grímsá after it and Geitdalsáin converge outside Þingmúli. There are nice brown trout in the river. In the lake, there are both brown trout and char.
The area of Skriðuvatn is on the east side in the land of Vatnsskógar. This is where Skriðuvatn falls into Múlaá and all the east shore of the lake, all the way up to Öxará. There are also fishing rights in the eastern part of Múlaá, from the source of the river, and 250 meters down the river to the marked border post. Fishing is allowed in Öxará, on the east side, where the river falls into Skriðuvatn and upstream. It is preferable to fish with a fly in the lagoon that falls from the lake and into Múlaá. The area is a part of Veiðikortið.