A small, very flashy spate river in south-west Donegal, rising near Lough Tamur, gathering the Tullinteane tributary, and entering McSwyne's Bay at Bruckless. For 2026 it is catch-and-release only with a zero harvest quota — a specialist's river rather than a mainstream destination. The catchment is EPA-designated high-status water: clean, acidic, oligotrophic, draining peaty upland over Donegal's Dalradian metasandstone (the Banagher Sandstone Formation — feldspathic sandstone and conglomerate). That makes it one of the flashiest rivers around — it rises and drops within hours of rain, so the fishing is entirely flood-dependent and the window after a spate is short. Grilse run from midsummer on flood water; sea trout are present, in the tradition of the renowned Inver/Frosses rivers next door. There is little commercial fishery infrastructure here — come prepared to fish a wild, modest spate river on its own terms, and return everything.
EPA sampling confirms the Oily River holds mayflies, stoneflies, a strong caddis assemblage, chironomids and blackfly larvae, and freshwater shrimp (Gammarus), though this is presence evidence only and says nothing about hatch timing or rise reliability.
- Sandstone