Lowland · Mixed · East / Louth-Monaghan, IE

Monaghan Blackwater

Monaghan Blackwater — A river runs through it

The Monaghan Blackwater rises near the Bragan mountains and runs through Monaghan town toward the Ulster Blackwater at Caledon.

Tomorrow · Closed season
Czech Nymph
Forecast · Tomorrow
Closed season
Out of season. Try elsewhere.
90% projected
Today's fly
Czech Nymph
Czech Nymph
Conditions on the water · Tomorrow
Live gauge
Level
Steady
0.55 m
Water temp8.6°C
ClarityClear
Weather3°C
WindN 11 km/h
Pressure1018 hPa
Rain · recent0.0 mm
Rain · ahead0.0 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
Cool — slow
9°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.
Likely species
Gammarids
Hatch timeline · tomorrowPeak at 10am

12pm(now) — Autumn Olive

Stage: On emergersApproach: Emerger or dryActivity: 40%
Also:Black Midge40%
Peak emergence windowWeather boost5 food groups active

Peak activity at 10am — Black Midge (Black Midge, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 4 guilds as a supporter.

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 3 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 · November 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
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
Emy Lough
10 km
Brown trout · Pike
Lough Corry
20 km
Brown trout
Corranny Lake
22 km
Rainbow trout
Annagh Lake
35 km
Brown trout · Rainbow trout
Annaginny Fishery
35 km
Rainbow trout
Gallery · 2
  1. Monaghan Blackwater — A river runs through it
    A river runs through it
  2. Terrain map of the venue
    Terrain map
About this water

It carries wild and stocked brown trout, and increasingly the Dollaghan — the fast-growing migratory trout of Lough Neagh, which runs the river and is best fished after dark, much as you would fish for sea trout. A small salmon run arrives late in the season. Monaghan Anglers Association stocks and manages the water; day tickets are about €5.

Hatches & food

A limestone-influenced drumlin river with decent olive and sedge hatches; midges and sedges matter most after dark for the Dollaghan and sea trout, which behave like night-feeding sea trout rather than dry-fly risers.

  • Mixed
The full read · show the working · for Brown Trout · confidence 90%
How the 0 is built — score × weight = contribution
Temperature59 × 28%16.5
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity54 × 12%6.5
Conditions total= 71
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Warmer water — toward the 10–16 °C ideal band — would lift the temperature score.
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 March → 30 September

Sea trout: Variable seasonal (2026)

Related guides
ConnemaraIrish fishingEuro Nymphingsubsurface methods
Casting instructors near here
Booking & contacts
Permits & access
At a glance

Monaghan Blackwater is a lowland river in East / Louth-Monaghan, Ireland. It sits at about 70 m above sea level. Our data lists brown trout and sea trout here. The trout season is recorded as running from 1 March to 30 September. Core methods listed: upstream dry and nymph; wet-fly swing after dark for Dollaghan; floating-line sea-trout/Dollaghan night fishing. Level and flow data for this water is linked from 1 gauge. Access is recorded as a water managed by an angling association or club. Nearby waters in our listings include Emy Lough at 10 km, Lough Corry at 20 km and Corranny Lake at 22 km.