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.

Marginal · Brown Trout
Pheasant Tail Nymph · 14-18
Slow going — pick your moments
River lifting fast on the rain. Slow going — pick your moments and do not force it.
45% confidence
limited data
What moved it
  • LevelProxyvia Boyne
  • Water temp13.9°C
  • ClarityVery colouredColouring up
Today's fly
Pheasant Tail Nymph
Pheasant Tail Nymph14-18
Upstream
Conditions on the water
Proxy gauge
Level
Rising
Proxy
via Boyne
Water temp13.9°C
ClarityVery coloured
Weather21°C
WindSW 12 km/h
Pressure1020 hPa
Rain · recent1.7 mm
Rain · ahead0.5 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
14°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
Poor — water temperature is working for you, but water clarity is the limiting factor today.
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 · todayPeak at 6am

Hatch predictions

Today's headline hatch shown — see all 9 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 2 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.

Updated 2 hours ago

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
Fishing better 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 45%
How the 30 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow55 × 22%12.1
Clarity15 × 18%2.7
Feeding Time65 × 13%8.5
Pressure80 × 7%5.6
Insect activity51 × 12%6.1
Limiting factor: Water is very coloured — too coloured for Brown Trout= 63
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowproxy via Boyneproxy
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
A drop and clear would lift the flow and clarity scores.
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