Lowland · Mixed · East / Meath

Mongagh & Yellow Rivers

Mongagh & Yellow Rivers terrain map

Two small Boyne tributaries near Castlejordan — the Mongagh coming down from near Tyrrellspass, the Yellow from north of Daingean.

Prime · Brown Trout
Pheasant Tail Nymph · 14-18
Primelive now
About as good as it gets
Low and clear — careful approach country. Take your time — read the water before you cast.
90% confidence
What moved it
  • LevelProxyvia Boyne
  • Water temp13.0°C
  • ClarityClear
Today's fly
Pheasant Tail Nymph
Pheasant Tail Nymph14-18
Upstream
Conditions on the water
Proxy gauge
Level
Steady
Proxy
via Boyne
Water temp13.0°C
ClarityClear
Weather20°C
WindNW 18 km/h
Pressure1020 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

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

Water temperature for Brown Trout
Ideal
13°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
Excellent — water temperature is right today, though insect activity could be better.
Likely species
Mayflies
  • Blue-winged oliveMost likely
    #16–18 · Dun
    Duns are up; a sherry spinner fall may follow.
  • Anglers curse mayfliesAlso possibleLower confidence
    #20–22 · Spinner
    Go tiny: 20-22 spent spinner, single fly, long tippet.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 12 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 3 guilds with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 3 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
Other water nearby · 5
About this water

Two small Boyne tributaries near Castlejordan — the Mongagh coming down from near Tyrrellspass, the Yellow from north of Daingean. Both hold good stocks of small wild brown trout, with better fish to two pounds in the lower reaches below Clongall Bridge. Edenderry & Castlejordan Angling Association controls the fishing and runs it catch-and-release, with sanctuary areas in operation — so it pays to check which stretches are open before you set off.

Hatches & food

Two small mixed-geology Boyne tributaries with typical small-stream fly life — spring olives, summer Blue-Winged Olive and sedge, and a heavy reliance on black gnat and other terrestrials on the lower, slower reaches.

  • Mixed
The full read · show the working · for Brown Trout · confidence 90%
How the 85 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time70 × 13%9.1
Pressure80 × 7%5.6
Insect activity64 × 12%7.7
Conditions total= 85
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Boyneproxy
Prey activitysurvey-backed invertebrate datasurvey
Directions
Seasons & zones
  • Trout 1 March30 September
Related guides
Casting instructors near here
Booking & contacts
Permits & access