Mayflies
Stoneflies
Damselflies & dragonflies
Gammarids
- Ecology: Good
- Chemical: Unknown
WFD classification · HRCSRN0481_001
Rules at a glance
- Permit required
Water temperature for Grayling
Ideal8°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Excellent — water temperature is working for you, but time of day is the limiting factor today. Grayling is active in the cooler margins of the season.
Likely species
Damselflies & dragonflies
Hatch timeline · todayQuiet day
Hatch predictions
Today's headline hatch shown — see all 6 active hatches hour by hour as a supporter.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 4 guilds as a supporter.
Start free trial14-day free trial. Cancel anytime.
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
1
Grayling seasonSeason
1
2
2
2
2
1
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
2
2
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Fly box · Grayling
Hook 14–18 · Fly
in season · matches water height
Permits & access
Permit required — see local rules.
- Croatian fishing licence plus local permit
- Risnjak park section is catch-and-release, fly only, single barbless hook, no boats, and no night fishing
- Park entrance also applies.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 1
IMG 20180713 163857(fixed)
Water quality (WFD)
The full read · show the working · for Grayling · confidence 75%
How the 80 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time20 × 13%2.6
Pressure80 × 7%5.6
Insect activity47 × 12%5.6
Conditions total= 75
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 16 May → 30 September
- Grayling 16 May → 15 October
Conflicting sources for Kupa grayling season: Risnjak National Park (upper Kupa, C&R) lists grayling 16 May – 15 October; Kupa Fly Fishing operator lists 1 April – 15 October. Use the stricter May window until the specific beat/concession confirms otherwise. Croatian national rule: one rod, artificial fly or lure only in permanent grayling habitats.
Prime sport 1 August → 15 October
- 16 May → 15 Oct · Artificial fly or artificial lure
- Hucho 1 October → 28 February
Related guides
Booking & contacts
Boards & regulators
- Kupa Fly Fishing — RegulationsKupa system rules and permit information. Lists grayling season as 1 April – 15 October, but Risnjak NP rules show 16 May – 15 October. Use the stricter May window as the app default.
- Risnjak National Park — Sport FishingUpper Kupa / Risnjak National Park catch-and-release rules. Lists grayling from 16 May to 15 October — the conservative window used as the app default.
Kupa (Upper / Risnjak NP)
Water temperature for Grayling
Ideal8°C est.ideal 4–14°C
0°14°28°
How to fish it · for Grayling
When
Midday window — grayling feed best from late morning into early afternoon.
Where
Work runs and glides — grayling shoal in the bottom third of the water column.
Method
Tight-line nymph the bottom third with weighted patterns.
Kit
10 ft #3 rod, floating line, long leader to 4 lb fluoro for nymphs.
Why this works
Excellent — water temperature is working for you, but time of day is the limiting factor today. Grayling is active in the cooler margins of the season.
Likely species
Damselflies & dragonflies
Hatch timeline · todayQuiet day
Hatch predictions
Today's headline hatch shown — see all 6 active hatches hour by hour as a supporter.
Start free trial14-day free trial. Cancel anytime.
Sub-surface · on the nymphunder the surface
Hatch predictions
Top nymph shown — see all 4 guilds as a supporter.
Start free trial14-day free trial. Cancel anytime.
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
1
Grayling seasonSeason
1
2
2
2
2
1
Evening SedgeHatch
2
3
3
3
2
Large Dark OliveHatch
1
2
2
1
Iron BlueHatch
1
2
2
2
2
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Fly box · Grayling
Hook 14–18 · Fly
in season · matches water height
Permits & access
Permit required — see local rules.
- Croatian fishing licence plus local permit
- Risnjak park section is catch-and-release, fly only, single barbless hook, no boats, and no night fishing
- Park entrance also applies.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 1
IMG 20180713 163857(fixed)
Water quality (WFD)
- Ecology: Good
- Chemical: Unknown
WFD classification · HRCSRN0481_001
The full read · show the working · for Grayling · confidence 75%
How the 80 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time20 × 13%2.6
Pressure80 × 7%5.6
Insect activity47 × 12%5.6
Conditions total= 75
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Trout 16 May → 30 September
- Grayling 16 May → 15 October
Conflicting sources for Kupa grayling season: Risnjak National Park (upper Kupa, C&R) lists grayling 16 May – 15 October; Kupa Fly Fishing operator lists 1 April – 15 October. Use the stricter May window until the specific beat/concession confirms otherwise. Croatian national rule: one rod, artificial fly or lure only in permanent grayling habitats.
Prime sport 1 August → 15 October
- 16 May → 15 Oct · Artificial fly or artificial lure
- Hucho 1 October → 28 February
Related guides
Booking & contacts
Boards & regulators
- Kupa Fly Fishing — RegulationsKupa system rules and permit information. Lists grayling season as 1 April – 15 October, but Risnjak NP rules show 16 May – 15 October. Use the stricter May window as the app default.
- Risnjak National Park — Sport FishingUpper Kupa / Risnjak National Park catch-and-release rules. Lists grayling from 16 May to 15 October — the conservative window used as the app default.