- Ecology: Moderate
- Chemical: Unknown
WFD classification · HRJKRN0269_001
Water temperature for Brown Trout
Warm — slow18°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
Water at 18.1°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 6pm
Hatch predictions
Today's headline hatch shown — see all 11 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 3 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 3 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
ModelledModerate confidence
Modelled from regional ecology — no survey or occurrence data for this water 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
2
1
Grayling seasonSeason
1
2
2
2
2
2
2
1
Brown SedgeHatch
2
3
2
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Blue Winged OliveHatch
2
3
3
3
3
2
Mayfly (Green Drake)Hatch
2
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Brown Trout fly box
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
Water here around 18°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
Gacka Terrain map
Water quality (WFD)
The full read · show the working · for Brown Trout · confidence 90%
How the 39 is built — score × weight = contribution
Temperature54 × 28%15.1
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity66 × 12%7.9
Conditions total= 71
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
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 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
Booking & contacts
Gacka
Water temperature for Brown Trout
Warm — slow18°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
Water at 18.1°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 6pm
Hatch predictions
Today's headline hatch shown — see all 11 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 3 guilds with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 3 with Pro.
Start free trial14-day free trial. Cancel anytime.
Evidence
ModelledModerate confidence
Modelled from regional ecology — no survey or occurrence data for this water 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
2
1
Grayling seasonSeason
1
2
2
2
2
2
2
1
Brown SedgeHatch
2
3
2
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Blue Winged OliveHatch
2
3
3
3
3
2
Mayfly (Green Drake)Hatch
2
2
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Brown Trout fly box
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
Water here around 18°C. Nothing cooler within range — carry a thermometer.
Gallery · 2
Gacka Terrain map
Water quality (WFD)
- Ecology: Moderate
- Chemical: Unknown
WFD classification · HRJKRN0269_001
The full read · show the working · for Brown Trout · confidence 90%
How the 39 is built — score × weight = contribution
Temperature54 × 28%15.1
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity66 × 12%7.9
Conditions total= 71
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
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 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
Booking & contacts