Spring Fed · Karst · Lika-Senj / Otočac, HR

Gacka

Photo of Gacka

Croatia's flagship trout river — a classic karst spring creek rising fully formed from limestone near Otočac.

Today · About as good as it gets
Pink Shrimp
Forecast · Today
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
Pink Shrimp
Pink Shrimp
Conditions on the water · Today
Live gauge
Level
Falling
0.34 m
Dropping after lift
Water temp10.0°C
ClaritySlightly coloured
Weather13°C
WindN 12 km/h
Pressure1026 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
Ideal
10°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 — conditions well-balanced, with water temperature particularly in your favour.
Likely species
Mayflies
Stoneflies
Caddisflies
Damselflies & dragonflies
Gammarids
Hatch timeline · todayPeak at 12pm

12pm(now) — Autumn Olive

Stage: On emergersApproach: Emerger or dryActivity: 61%
Also:Black Midge38%Autumn Needle Fly36%
Peak emergence window9 food groups active

Peak activity at 12pm — Autumn Olive (Autumn Olive, 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 2 as a supporter.

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Evidence
Records-basedModerate confidence

Based on species-occurrence records, not local invertebrate surveys.

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
2
1
Grayling seasonSeason
1
2
2
2
2
2
2
1
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Brown SedgeHatch
2
3
3
3
2
Small SpurwingHatch
2
3
3
3
2
Small Dark OliveHatch
2
3
3
3
2

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

Ranked for today
Brown Trout fly box

Ultra-clear spring-fed rivers with large educated trout. Sight fishing, technical presentation, fine tippets. Euro-nymphing dominant subsurface method. Exceptional dry-fly windows during hatch periods. Gacka is the flagship water.

SW
Streamer / Woolly BuggerTop
6-10 · Pattern
High-confidence seasonal pick
Permits & access
Permit required — see local rules.
  • Croatian fishing licence required
  • Local concessionaire permit needed
  • Zone A is fly-only catch-and-release; wider Gacka rules vary by zone, so fish the named zone rather than the river name alone.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Dobra
48 km
0
Brown trout · Grayling
Korana
48 km
Brown trout
Una
50 km
83
Brown trout · Grayling · Hucho
Vitunjčica
54 km
Brown trout
Mrežnica
59 km
0
Brown trout · Grayling
Gallery · 2
  1. Photo of Gacka
    Gacka
  2. Terrain map of the venue
    Terrain map
About this water

Croatia's flagship trout river — a classic karst spring creek rising fully formed from limestone near Otočac. Crystal-clear, slow-moving water with large wild brown trout in weed beds and undercuts. The main course is managed through Zones A, B and C, with a separate Zone D lake/grayling area in the wider fishery structure. Spring-fed character gives constant temperature and gin-clear water year-round — extending the season well into summer when freestone rivers struggle. Technical dry fly and sight nymphing in true chalk-stream conditions. One of the few genuine spring creek ecosystems in Southern Europe. WFD ecological status is 'Moderate' — likely reflecting nutrient inputs or modified hydrology rather than poor fishing quality; the managed fly zones remain productive.

  • Karst
Water quality (WFD)
  • Ecology: Moderate
  • Chemical: Unknown

WFD classification · HRJKRN0269_001

The full read · show the working · for Brown Trout · confidence 90%
How the 87 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time85 × 13%11.1
Pressure80 × 7%5.6
Insect activity66 × 12%7.9
Conditions total= 87
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 March → 31 October
  • Grayling 15 May → 31 December

    Gacka is an iconic Croatian spring-creek fishery — catch-and-release only for both grayling and brown trout along the entire river. Retention of grayling is prohibited. Fishing downstream of the zero bridge is allowed subject to concession rules. One rod, artificial fly or lure only. Check current concession holder rules — the Gacka is a conservation-priority water.

    All grayling must be returned — retention is prohibited here.

Related guides
Chalkstream Playbookkarst spring river — same tacticsGrayling Playbookgrayling tacticsEuro Nymphingsubsurface methods
Booking & contacts