The Large Dark Olive (*Baetis rhodani*) is one of the most important early-season upwinged flies in the UK and signals the real beginning of the river trout season. Found on rivers throughout Britain, it is often the first significant hatch of spring and can produce some of the year's finest dry fly fishing. While individual insects may be seen during much of the year, the main hatches usually occur throughout March and April, with a smaller autumn brood often appearing in September and October. Large Dark Olives are particularly important because, during early spring, they are frequently the only substantial upwinged fly hatching in numbers.
The nymph is an agile swimmer that lives amongst weed, gravel and stones on the riverbed. As water temperatures begin to rise during spring, the nymphs become increasingly active before swimming towards the surface to hatch in open water. Unlike some later mayflies, the spinner fall is of relatively little importance to anglers, with trout tending to concentrate on the nymphs, emerging insects and freshly hatched duns.
Large Dark Olive hatches are often concentrated around the warmest part of the day, typically from late morning into the afternoon. On bright spring days it pays to watch the surface carefully, as trout may switch from feeding below the surface to confidently taking emerging duns within a matter of minutes. Cold north or easterly winds can suppress the hatch, making nymph fishing the more productive approach until conditions improve.
Before the hatch begins, a well-presented nymph is usually the most consistent tactic. As fish begin intercepting insects in the surface film, emerger patterns often outfish fully hatched duns. Once the hatch is in full swing and trout are rising confidently, accurate drag-free presentations with a well-presented dry fly can produce superb sport. Matching the stage of the hatch is usually far more important than changing between similar fly patterns.
At Peaks Fly Fishing, the Large Dark Olive hatch is one we always look forward to. It marks the transition from winter into spring and often provides the first memorable dry fly fishing of the season. Don't be tempted to fish dry flies too early though. We usually begin with a nymph, switch to an emerger as fish start to rise, and only move to a fully floating dun once trout are feeding confidently on the surface. That simple progression consistently catches more fish.
## Recommended Fly Patterns
### Nymphs
* Pheasant Tail Nymph
* Olive Hares Nymph
* Olive Copperhead Nymph
### Emergers
* Olive River Emerger
* Olive Klinkhammer Emerger
* Deer Hair Emerger
### Duns
* Large Dark Olive
* Olive Dun
* Greenwell's Glory
### Alternatives
* Hare's Ear Nymph
* Little Leggy F-Fly
* Kite's Imperial
## Peaks Fly Fishing Tips
* Expect the best hatches around the warmest part of the day.
* Cold north or east winds often reduce hatch activity.
* Fish a nymph before the hatch, an emerger as fish begin to rise and a dun once trout are confidently taking adults.
* A drag-free presentation is usually more important than the exact fly pattern.
* Don't pack your dry flies away after spring - a second brood often appears during early autumn and can provide excellent late-season sport.
