The Iron Blue is one of the UK's most distinctive mayfly hatches and has a reputation for producing some of the most selective trout of the season. Unlike many other upwinged flies that favour warm, sunny weather, Iron Blues often hatch during cool, overcast, wet or windy conditions. When other insect activity slows, an Iron Blue hatch can suddenly bring trout confidently to the surface, rewarding anglers who have the correct flies ready.
The name Iron Blue is used by anglers to describe several closely related species that are similar in appearance and behaviour. They are widespread throughout Britain and Ireland, particularly on faster-flowing rivers where their agile nymphs live amongst weed and gravel. Hatches are most common during late spring and early summer, with a second peak often occurring during the autumn months.
Iron Blue nymphs are active swimmers that leave the riverbed and hatch in open water. The adults are much smaller and darker than many other olives, making them easy to overlook. Trout, however, show a remarkable preference for them and will often ignore larger insects to concentrate solely on Iron Blues when a hatch is underway.
Because the insects are relatively small, presentation becomes critical. Trout feeding on Iron Blues usually inspect each insect carefully, making fine leaders, accurate casting and drag-free drifts essential. Long casts are rarely as important as placing the fly accurately and allowing it to drift naturally over the feeding fish.
Before the hatch, slim nymphs fished close to the riverbed are highly effective. As fish begin taking insects in the surface film, emerger patterns often produce the best results. Once trout are feeding confidently on the adults, a sparse dry fly that sits naturally in the surface film is usually all that is required.
At Peaks Fly Fishing, we always carry Iron Blue patterns, even when conditions appear poor. Some of our most memorable days have come during cold, grey weather when other anglers assumed nothing would hatch. An unexpected Iron Blue hatch can completely transform a difficult day into outstanding dry fly fishing.
## Recommended Fly Patterns
### Nymphs
* Sawyers Pheasant Tail Nymph
* Tactical PTN
### Emergers
* Small Black Klinkhammer
### Duns
* Iron Blue
### Alternatives
* Black Gnat
* Lunn's Particular
* Parachute Adams
## Peaks Fly Fishing Tips
* Don't assume poor weather means poor dry fly fishing - Iron Blues often hatch on cool, overcast days.
* Fish small, sparse patterns with fine leaders and accurate presentations.
* Watch for subtle rises rather than splashy takes.
* Match the size of the natural insect before worrying about exact colour.
* Always keep a few Iron Blue patterns in your fly box, even during the summer months - they're one of the hatches that regularly catches anglers by surprise.
Here's the revised version using correct UK terminology throughout.
