Lowland · Limestone · Shannon / Offaly, IE

River Brosna

River Brosna terrain map

A limestone river rising from Lough Ennell and running through Offaly to the Shannon, with wild brown trout, a croneen (migratory trout) presence and small summer salmon runs.

Tomorrow · About as good as it gets
Balloon Caddis
Forecast · Tomorrow
About as good as it gets
On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
90% projected
Today's fly
Balloon Caddis
Balloon Caddis
Conditions on the water · Tomorrow
Live gauge
Level
Falling
0.62 m
Dropping after lift
Water temp13.8°C
ClaritySlightly coloured
Weather12°C
WindN 17 km/h
Pressure1019 hPa
Rain · recent2.4 mm
Rain · ahead7.5 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Ideal
14°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Excellent — water temperature is right today, though time of day could be better.
Likely species
Mayflies
Stoneflies
Caddisflies
Gammarids
Hatch timeline · tomorrowPeak at 11am

12pm(now) — Black Gnat

Stage: On emergersApproach: Emerger or dryActivity: 95%
Also:Cinnamon Sedge58%Pale Watery47%Heather Fly47%
Peak emergence windowWeather boost11 food groups active

Peak activity at 11am — Black Gnat (Black Gnat, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 5 as a supporter.

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Evidence
Survey-backed · regionalHigh confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
Mayfly (Green Drake)Hatch
2
2
Large Cinnamon SedgeHatch
2
3
3
2
Daddy Long LegsHatch
2
3
2
CapererHatch
2
3
3
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Pallas Lake
13 km
Rainbow trout · Brown trout
Mount Dalton Lake
20 km
Brown trout
Lough Ennell
21 km
Brown trout · Pike
Camcor River
29 km
Brown trout
Lough Owel
30 km
Brown trout
About this water

A limestone river rising from Lough Ennell and running through Offaly to the Shannon, with wild brown trout, a croneen (migratory trout) presence and small summer salmon runs. Classic midland water, best before the summer weed.

Hatches & food

EPA river-invertebrate monitoring confirms mayflies, stoneflies, caddis, aquatic diptera and freshwater crustaceans are present across the Brosna's monitored segments. This is food-presence evidence only, drawn from kick samples, and doesn't establish emergence timing or the strength of any visible hatch.

  • Limestone
The full read · show the working · for Brown Trout · confidence 90%
How the 84 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity74 × 12%8.9
Conditions total= 84
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 March → 30 September
Related guides
ConnemaraIrish fishingEuro Nymphingsubsurface methods
Casting instructors near here
Booking & contacts
Permits & access