Mask runs deeper and lies more exposed than its neighbour, which asks a measure of respect from anyone handling a boat on it, and the mayfly and olive hatches are as good as anywhere in the west. Ferox hold in the deep water, and plenty who fish both loughs rate Mask's trout the larger on average — when the conditions come together, which they don't always, the fishing can be as good as Irish lough fishing gets. Dapping earns its keep whenever the breeze allows it. As with Corrib, a boatman who knows the water is worth having rather than doing without; this is not water to learn the hard way.
Named among the western limestone loughs for duckfly from around 17 March for about three weeks, lake olives from late April to early May, and a mayfly period from after the first week of May into early June - regional guidance rather than a measured hatch on Mask itself. The same source places Caenis at first light and sedges late in the evening through the summer months.
- Surface area
- 78.0 km² (19,267 acres)
- Mean depth
- 15 m (49 ft)
- Area: EPA Ireland (CC BY 4.0). Mean depth: Mayo County Council.
- Lough system
- Limestone