Stoneflies
Gammarids
The Lennon fishes as a salmon and sea-trout river with a moderately responsive catchment. Spring salmon from February; grilse from June; sea trout abundant from May through September. The estuary of Lough Swilly is tidal — lower reaches of the Lennon are subject to tidal influence. Multiple named pools; public access to most sections. Salmon numbers have been recovering since the UDN outbreak of the 1970s, though the river remains less prolific than in its pre-disease prime. For 2026 this is a catch-and-release fishery under the Wild Salmon & Sea Trout Tagging Scheme — all salmon and grilse must be returned.
EPA monitoring on the Lennon (Leannan) confirms mayflies — including Ephemera danica — alongside stoneflies, a strong caddis assemblage, chironomids and blackfly larvae, and freshwater shrimp and hoglice, are all present in the river; this is food-presence evidence from kick sampling, not a record of emergence timing.
The Lennon near Ramelton is described as having "sea trout abundant from May through September" — one of the longer sea-trout windows claimed for any Donegal river. Tidal lower reaches via Lough Swilly. Moderate response time (8 hours) gives longer fishing windows than typical Donegal spate rivers.
- Mixed