Lough Mask is the upper of two lakes, feeding through an underground stream into Lough Corrib, which in turn empties via the Corrib River into Galway Bay.
Lough Mask is the sixth largest lake in Ireland, measuring 16 km in length and 6.4 km in width, with a surface area of approximately 8218ha / 20,000 acres / 83 sq km / 32 sq miles, mainly in County Mayo with a corner in County Galway.
The main inflowing rivers into Lough Mask are the Rivers Cloon, Robe, Owenbrin, Finny, Glensaul, Glentraig and Keel (the outflowing stream from Lough Carra).
Lough Mask is generally a shallow lake with a mean depth of 5m. The shallowest area of the lake is along the eastern shore and it gradually gets deeper towards the western shore with a maximum depth of 57m occurring in a long narrow trench in the north western and western shore of the lake. The level of the lough varies by as much as 8ft from summer to winter.
Lough Mask is famed for its brown trout, and also holds ferox trout, salmon, pike, roach, bream, perch, arctic char and eel. The Western Fisheries Board has a development and information centre at Cughlough. There is a statutory 12-inch size limit for keeping trout caught on the lough.
Ballinrobe is the major angling centre for Lough Mask, but anglers also stay at Cushlough, Partry, Srah, Tourmakeady, Tream, Ferry Bridge, Clonbur and Ballinchalla. Access to the lough is very good with safe moorings and slipways in most areas. The chief points of access are Cushlough – where there is a large car park, anglers’ shelter, public toilets and a number of excellent guest houses, Cahir Bay, Ballinchalla Bay, Roshill, Ferry Bridge, Annagh, Churchfield, Tourmakeady, Srah, Ballygarry and Aughinish. Anglers should check, as local permission is required at some of the above.
Boats are available for hire around the lake. Lough Mask is a dangerous place with a hazardous shoreline and extensive reefs, capable of splitting a boat wide open, lying just under the surface. New-comers would be well advised to avail of the services of an experienced boatman.
Lough Mask has fewer islands than neighbouring Lough Corrib, and is not as shallow, so the mayfly hatches are later to start. It has a much greater hatch of caddis (sedge) fly throughout the summer months which can have an angler confused as to which trout to cover first. Mask is often referred to as the dangerous lough because of it’s and deep waters, but in reality it is just as safe as it’s neighbour Corrib, when using the services of a local guide or boatman.
Lough Mask’s islands, mostly in the central and southern part of the lake, have names such as Carrigeenagur, Carrigeenaweelaun, Carrigeendasvoe, Carrigeendauv, Inishocht, Devenish, Inishgleasty, Saint’s Island, Rams Island, Red Island and White Island.
Inishmaine / Inishmaan, by far the largest insular body on the lake, one of a cluster just off the southeastern shore, is technically no longer an island as it became joined to the mainland when the waters of Lough Mask were lowered on the construction of the Corrib/Mask Canal.
Inishowen contains the remnants of a large fort.
In 1338, at the end of the Burke Civil War (1333–38), Sir Edmond de Burgh was drowned in the lake by his cousin Sir Edmond Albanach Bourke of County Mayo.
The lough was the scene of the 1882 “Lough Mask murders”, when two bailiffs working for Lord Ardilaun were killed, described as “an old man and a lad”. Tensions had arisen in the area during the Land War and the proximity of land managed by Charles Boycott. The corpses were found in the lough itself. The controversial lack of credible witnesses led to four well-publicised trials of the accused in 1882-83.