Lowland · Limestone · Shannon / Offaly

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.

Marginal · Brown Trout
Pheasant Tail Nymph · 14-18
Marginallive now
Slow going — pick your moments
River temperature is the limiting factor today, not the flow. Fish dawn or dusk if you go at all, and handle everything with extra care.
80% confidence
What moved it
  • LevelProxyvia Shannon (Upper)
  • Water temp19.9°C
  • ClarityClear
Today's fly
Pheasant Tail Nymph
Pheasant Tail Nymph14-18
Upstream
Conditions on the water
Proxy gauge
Level
Steady
Proxy
via Shannon (Upper)
Water temp19.9°C
ClarityClear
Weather15°C
WindNW 14 km/h
Pressure1023 hPa
Rain · recent0.5 mm
Rain · ahead1.0 mm

No gauge on this water — conditions are inferred from Shannon (Upper). The trend transfers, the absolute level does not.

Water temperature for Brown Trout
Warm — slow
20°C est.ideal 1016°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
Water at 19.9°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 6am

Hatch predictions

Today's headline hatch shown — see all 4 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

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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 · August highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
Daddy Long LegsHatch
2
3
2
Terrestrial BeetlesHatch
2
3
3
2
Blue Winged OliveHatch
1
2
2
2
2
1
Black MidgeHatch
1
2
2
2
2
2
2
2
2
2
2
1

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
Cooler water nearby · 4
Water here around 20°C — probably warm enough to stress Brown Trout . These are likely cooler.
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 80%
How the 28 is built — score × weight = contribution
Temperature26 × 28%7.3
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time45 × 13%5.9
Pressure80 × 7%5.6
Insect activity58 × 12%7.0
Conditions total= 61
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Shannon (Upper)proxy
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
  • Trout 1 March30 September
Related guides
Casting instructors near here
Booking & contacts
Permits & access