Fishing district

Blava č. 3

Salmon – troutno. 2-0150-4-1BlavaDanube basin
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Fishing district boundaries: Blava od prameňov po pstruhové hospodárstvo Dechtice.

fishing district length
8,7km
district
Trnava
region
Trnava Region
Aerial image of fishing district Blava č. 3 with the line highlighted
Blue line: course of the fishing district (approximate). Orthophoto mosaic of Slovakia © GKÚ Bratislava, CC BY 4.0Mapy Google

By the water now

Fishing conditionsFish activity indexOur calculation (0–100): the base is set by water temperature, adjusted by light, turbidity, oxygen, weather and other factors according to how well they are supported by studies. For each factor you can see the confidence and the source. A planning aid, not a bite forecast.

The score, the best window of the day and what pushes it up or down

Fishing conditions

Fish activity indexOur calculation (0–100): the base is set by water temperature, adjusted by light, turbidity, oxygen, weather and other factors according to how well they are supported by studies. For each factor you can see the confidence and the source. A planning aid, not a bite forecast.

Loading data…

Water

Water level, temperature, modelled flow and gradient

Elevation profile of the watercourse

Elevation profileHow the altitude of the watercourse changes downstream. It is calculated from a digital relief model (tens of metres), not from a water-level measurement, so it is approximate, especially for narrow streams.

Brisk watercourse A foothill river with a gravel bottom and a fast current. Grayling and trout already thrive here.

1802002202402602800 km2 km4 km6 km8 km
Elevation profile of the fishing district downstream: from 264 to 193 m a.s.l. over 8.7 km.
Downstream, from the upper end of the fishing district (left) to the lower end
Highest point
264 m a.s.l.
Lowest point
189 m a.s.l.
FallFallThe difference in altitude between the upper and lower end of the fishing district in metres. The greater the fall over a shorter length, the faster the water.
75 m
SklonWatercourse gradientFall per kilometre in per mille (‰, metres per kilometre). Up to 2 ‰ is a slow lowland river, 5 to 10 ‰ a foothill river (grayling, trout), above 10 ‰ a fast stream.
8,7 ‰
SinuositySinuosityThe length of the watercourse divided by the straight-line distance between its ends. 1.0 is a straight watercourse; above 1.3 it meanders strongly. Meanders create pools under the banks and shallows in the reaches between.
1,13
Source: Open Topo Data (eudem25m)Updated 4 Nov 2026 11:03

Weather and forecast

Hour by hour, pressure and the next few days

Weather and forecast

Loading data…

Sky: sun, moon and solunar windowsSolunar periodsCalculated from the position of the Moon: major periods (about 2 h) around the Moon's passage above and below the horizon, minor periods (about 1 h) around moonrise and moonset. A scientifically unconfirmed theory: in a study of 361 fishing trips (Quigley et al. 2023) it did not predict bites. We treat it as a hypothesis with a weight of at most ±2 points.

Where the sun and moon are right now and when the best windows of the day will come

Sky: sun and moon

Solunar periodsCalculated from the position of the Moon: major periods (about 2 h) around the Moon's passage above and below the horizon, minor periods (about 1 h) around moonrise and moonset. A scientifically unconfirmed theory: in a study of 361 fishing trips (Quigley et al. 2023) it did not predict bites. We treat it as a hypothesis with a weight of at most ±2 points.

Drag along the axis to see where the sun and moon will be.

  • Sun
  • Moon
  • Golden hour
  • Main period
  • Minor period

Sun

  • Dawn06:12
  • Sunrise06:45
  • Sunset16:21
  • Dusk16:54

The day lasts 9 h 36 min.

MoonMoon phaseAt full and new moon the gravitational effect is strongest. On a clear full-moon night predators and carp often feed at night, and the day after may be weaker.

Waning crescent8% illuminated
  • Sunrise04:46
  • Sunset15:04

Full moon around 24 Nov, new moon around 9 Nov.

Windows of the daySolunar periodsCalculated from the position of the Moon: major periods (about 2 h) around the Moon's passage above and below the horizon, minor periods (about 1 h) around moonrise and moonset. A scientifically unconfirmed theory: in a study of 361 fishing trips (Quigley et al. 2023) it did not predict bites. We treat it as a hypothesis with a weight of at most ±2 points.

  • Minor solunar period04:16–05:16
  • Golden hour (morning)06:15–07:45
  • Major solunar period09:01–11:01
  • Minor solunar period14:34–15:34
  • Golden hour (evening)15:21–16:51
  • Major solunar period21:23–23:23

The solunar theory is not scientifically confirmed; we treat it as a supplement. The golden hour is the time around sunrise and sunset, when fish often bite.

Map and fishing district data

Course of the water, spots along the water, character and basic data

48.57806, 17.55298 OpenStreetMap

The line shows the course of the fishing district according to the "Rybárske revíry" data 2026. Verify access points and exact boundaries on site.

Fishing district details

Manager
Lesy SR, š.p. B.Bystrica
Fishing district user
LESY
Organization
OZ Smolenice
Area
Western Slovakia
Purpose
Fishing district
Minimal stocking
Pp1 1000 pcs

Law and fishing rules

Closed season, fishing hours, minimum sizes and daily limit. For guidance only: check them in the fishing regulations of the fishing district

Closed season for all fish

Section 13, paragraph 1 of the Act

1 Oct – 15 Apr

fishing for all fish prohibitedoutside this period

Exception: on waters where huchen occurs, from 1 Nov to 31 Dec fishing for huchen is possible only with a huchen fishing permit (§ 13, para. 4 and § 19 of the Act).

The protection periods by species (below) apply independently of this closed season.

Daily fishing hours

§ 11 of the Decree

Applies only outside the closed season. Outside these hours fishing is prohibited (§ 14(b) of the Act).

April, September6.00 – 20.00 h

May, August5.00 – 21.00 h

June, July4.00 – 22.00 h

November, December7.00 – 19.00 h

Months missing from the table fall within the closed season. The hours in November and December on trout and grayling waters relate to the exception for fishing huchen (§ 13, para. 4 of the Act); check in the fishing regulations what may be caught at that time. On border waters the hours in the permit or the fishing regulations apply (§ 11, para. 2 of the Decree). The Act regulates night fishing in two wordings that seem to contradict each other at first sight, so always ask about it in the fishing regulations of the district or the fishing guard.

Rods, baits and fishing days

§ 16 of the Act
Number of rods
1
Permitted methods
fly fishing, spinning
Hooks and baits
fly fishing at most 3 artificial flies, spinning one lure
Live or dead baitfish
prohibited
Fishing days of the week
most in 3
Ice fishing
prohibited
Other
prohibition of groundbaiting and of several baits (pastes, granules, pellets, cheese, worms, insects, roe)

This is a summary. For baits, hooks and groundbait also read the fishing regulations of the district, because the user may tighten the conditions.

How many fish you may keep per day

§ 14 of the Decree
  • 1ksBlue groupsterlet, Siberian sturgeon, wels catfish
  • 2ksGreen groupeel, carp, burbot, zander, pike, tench, barbel, lake brown trout, brown trout, grayling (combined)
  • 4ksYellow grouprainbow trout, brook trout, common nase, vimba bream; added to the green or blue group (at most 4 fish in total)
  • 5kgOther speciesfor example crucian carp, breams, dace and chub (combined); invasive species are not counted

The blue and green groups cannot be combined. The limit applies per day, also when fishing in several districts, and once it is reached, fishing for that day ends. The species groups follow the SRZ interpretation of January 2026, not the text of the section directly. The district user may set a lower limit in the permit, in which case the stricter one applies.

Protection periods by species§ 10 of the Decree

During this period the species must not be caught, even if the water type otherwise allows fishing at that time. It applies independently of the closed season for all fish.

1 Jan – 15 Mar
burbot
1 Jan – 31 May
grayling, spirlin, northern pike
1 Jan – 15 Jun
wels catfish, zander (pikeperch), Volga pikeperch
1 Jan – 31 Oct
huchen (in border waters 1 Jan – 31 Aug)
15 Mar – 31 May
common carp in carp waters (does not apply 1 – 31 May during competitions, nor on other water bodies); asp, chub, dace, ide, sterlet, Siberian sturgeon, tench, barbel, vimba bream, zope, white-eye bream, common bream, common nase
1 Sep – 15 Apr
brown trout, brown trout (lake form)
1 Sep – 28 Feb
peled

Some species are protected all year round (for example zingel and streber, lampreys, gudgeons, spined loaches, maraena whitefish, Carpathian barbel, sabre carp) and fishing for them is always prohibited. The full list of species is in the guide The fishing law, rule by rule.

Minimum sizes§ 12 of the Decree

The shortest length from which you may keep a fish. The district user may raise the size, so look for the valid value in the permit and the fishing regulations.

  • grass carp60 cm
  • black carp60 cm
  • asp40 cm
  • huchen (Danube salmon)80 cm
  • chub25 cm
  • dace20 cm
  • ide30 cm
  • sterlet45 cm
  • Siberian sturgeon45 cm
  • common carp40 cm
  • tench30 cm
  • grayling33 cm
  • burbot35 cm
  • barbel40 cm
  • vimba bream30 cm
  • zope (blue bream)25 cm
  • white-eye bream25 cm
  • common bream30 cm
  • silver bream15 cm
  • common nase30 cm
  • rainbow trout27 cm
  • brown trout (lake form)50 cm
  • brown trout27 cm
  • peled25 cm
  • brook trout27 cm
  • wels catfish70 cm
  • northern pike60 cm
  • silver carp45 cm
  • bighead carp45 cm
  • European eel50 cm
  • zander (pikeperch)50 cm
  • Volga pikeperch35 cm

Total length is measured from the front of the head to the end of the longest ray of the tail fin (§ 12, para. 4). No minimum size applies, for example, to sunbleak, Prussian carp, European perch, roach, loach (slíž severný) and invasive species.

Before and after fishing

  • Carry your fishing license and permit while fishing and show them when checked (§ 12 of the Act). Check that they are valid.
  • Before you start fishing, write down the date and the district number (no. 2-0150-4-1); after fishing, write down the number and weight of your catch (§ 14(d) of the Act). Fishing without a record is an offense.
  • Prohibited fishing methods, night fishing, competitions and other rules are covered in the guide The fishing law, rule by rule.

As of 6 Nov 2026: Act no. 216/2018 Coll. on fisheries (wording effective 1 Jan 2022) and Decree no. 381/2018 Coll. (wording effective 1 Jan 2019); we found no newer wording. The law may change; you can find the current wording on Slov-Lex (Act) and Slov-Lex (Decree).

News from the organization and catches from the fishing district

Catches from this fishing district

Nobody has recorded a catch in this fishing district yetBe the first: after approval it will also appear here in the ranking.

Terén v 3D

Loading the 3D terrain model…

Water according to public sources

Water quality, river basin, bottom, fish, aquatic insects, wildlife and hazards from open databases. Except for wildlife and hazards, they are also included in the activity score.

What follows from this

Public sources in the conditions scoreData on oxygen, nutrients, reservoir depth, watercourse size, bottom, fish species and insect swarming slightly adjust the "Fishing conditions" score. Each adjustment is shown separately in the score breakdown.
−14−40+4+12−1
Public data about this water hardly change the activity score.
  • Biggest deduction: Riverbed by geology −1

We assessed 16 factors; 2 of them change the score. The adjustments range from −14 to +12 points so that they do not outweigh the weather and water temperature. They are counted in the score, in the ranking and in the filters.

Watercourse, reservoir and bottom−1

  • Riverbed by geologyLevel of evidence: Hypothesis

    Clays and loams, ŠGÚDŠ

    A fine-grained bottom is not typical of trout waters; the water clouds more easily.

    What we know about it

    Trout production is higher in hard limestone waters (Almodóvar et al. 2006), but in Irish watercourses geology did not change trout density and the channel structure was decisive (Lehane et al. 2004). The evidence diverges; the weight is small.

    Sources: Almodóvar et al. 2006; Lehane et al. 2004

    −1

Life by the water0

  • Aquatic insect swarmingLevel of evidence: Angling practice

    0.0× the average month, 0 of 25 observations in the year, iNaturalist

    Aquatic insects are scarce this month; food near the bottom matters more.

    What we know about it

    Anglers fish “by the insects” (dry and wet fly). A measured dependence of catches on swarming is not documented in our sources.

    0

Do not change the score

Data for these factors is missing or within the normal range:

  • Dissolved oxygen
  • Nutrients in water
  • Water acidity (pH)
  • Ammonium ions in water
  • Water temperature for local species
  • Surface water (SHMÚ)
  • Nitrogen in groundwater
  • Harmful substances in groundwater
  • Iron in groundwater
  • Chlorides in groundwater
  • Cold groundwater
  • Wastewater treatment plants
  • Watercourse size
  • Invasive species nearby

The rules are indicative and based on fishing practice and scientific studies; for each factor you can see how well it is supported. Weather, air pressure and water temperature affect the score more than this data does.

Water pollution

Water pollution (SHMÚ)Water quality indicators that fail the standards at the nearest monitoring site on the same watercourse in the SHMÚ yearbooks for 2022 to 2025.
Groundwater nearby
0 of 3stations with substances from human activity, 2025
Nitrates in groundwater
7,1 mg/ltypical value from 3 stations within 10 km, within the standard, 2025
Polluted water in Slovakia: the worst places and polluters

The data comes from the SHMÚ yearbooks (surface waters 2022 to 2025). The yearbook lists the sites that failed the standard; a site missing from the yearbook is not considered clean. We determine the distance and the match of the watercourse name ourselves, so the assignment is indicative.

Groundwater nearby

Groundwater nearby (SHMÚ)Measured groundwater values from stations within 10 km of the fishing district (nitrates, harmful substances, ammonium, iron, chlorides) and the SHMÚ yearbooks.

Groundwater within 10 km (3 stations)

  • Chtelnica – VitekPiešťany district · spring · 4.0 km from the fishing district
    no exceedance in 2025
    2017 to 2025

    Last exceeded in 2024:

    • Conductivity at 20 °C

    Measured values, year 2025, sampled 10 Jun 2025:

    • Nitrates15,8 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron< 0.002 mg/l
    • Chlorides1,8 mg/l
    • Aluminium60% of the standard
  • Jablonica – StuzkovaSenica district · spring · 4.9 km from the fishing district
    no exceedance in 2025
    2017 to 2025

    In the yearbooks 2017 to 2025 no exceedance of the standard is recorded at the station.

    Measured values, year 2025, sampled 10 Jun 2025:

    • Nitrates7,1 mg/l
    • Ammonium< 0.01 mg/l
    • Nitrites< 0.01 mg/l
    • Iron< 0.002 mg/l
    • Chlorides4 mg/l
    • Aluminium55% of the standard
  • Nizna – Huc-10/1Piešťany district · borehole or well · 6.5 km from the fishing district
    natural substances only
    2017 to 2025

    Exceeded in 2025:

    • Manganese
    • Total iron

    Measured values, year 2025, sampled 23 Sep 2025:

    • Nitrates< 1 mg/l
    • Ammonium0,05 mg/l
    • Nitrites< 0.01 mg/l
    • Iron2,88 mg/l
    • Chlorides39,4 mg/l
    • Aluminium10% of the standard
  • substances from human activity
  • natural substances only
  • no exceedance recorded

Groundwater reaches streams as base flow, so the connection to the stream at the fishing district is only indirect. Natural substances (iron, manganese, sulfates, conductivity) are not counted in the yearbook-based assessment.

The data comes from the SHMÚ yearbooks (groundwater 2017 to 2025).

River basin and reservoir

Reservoir depth (HydroLAKES)Average depth, volume and water retention time in the reservoir from the HydroLAKES database (WWF). The depth is estimated by a model from the surrounding terrain, so it is approximate.

Watercourse from the HydroRIVERS database matched with the fishing district, line deviation about 38 m

Catchment above the spotWatercourse size (HydroRIVERS)The catchment area above the spot, the stream order and the average flow from the HydroRIVERS database (WWF). It determines whether it is a stream, a river or a large river.
75 km²stream
Average flow
0.34 m³/smodel value
Stream order (Strahler)
1upper course, small tributary
Channel gradient
8,7 ‰Brisk watercourse

The data come from a global database with a coarser resolution (tens of metres), so they are only approximate for small waters. Depth and volume are model averages.

Bottom and bedrock

Bottom and bedrock (ŠGÚDŠ)The bedrock under the water according to the hydrogeological map of Slovakia at 1 : 50,000 (ŠGÚDŠ). It tells whether the surroundings are gravelly, sandy, clayey, muddy or rocky.

After rain the water quickly turns turbid and fish hunt more by smell.

  • Gravels 33%
  • Clays and loams 67%
Springs and outflows
0none within 1 km

According to the geological map: fluviálne sedimenty: litofaciálne nečlenené nivné hliny, alebo piesčité až štrkovité hliny dolinných nív a nív horských potokov, holocén

The map shows the bedrock geology, not the exact bottom at the spot. The actual bottom material may differ, especially where sediment has been deposited.

Aquatic insects

Aquatic insect swarming (iNaturalist)How many observations of mayflies, caddisflies and stoneflies people nearby recorded this month compared with the annual average. For fly anglers it hints at insect hatches.

Few insects November: 0.0× the average month

  • MayfliesMayflies0Mayflies: dry fly on the surface, especially at dusk.
  • CaddisfliesCaddisflies0Caddisflies: in the evening and at night by the bank; a nymph and a wet fly also work.
  • StonefliesStoneflies0Stoneflies: clean, cold streams, often already at the end of winter and in early spring.
Photo credits

0.0× the average month, 0 of 25 observations in the year, iNaturalist.

The observations are added by people from the surrounding area; they are not measurements at the water. They show when aquatic insects usually appear and are useful mainly for fly fishing.

Groundwater: measured values

Groundwater nearby (SHMÚ)Measured groundwater values from stations within 10 km of the fishing district (nitrates, harmful substances, ammonium, iron, chlorides) and the SHMÚ yearbooks.

A typical value from 3 groundwater stations within 10 km of the fishing district (nearest 4 km), measured in 2025. Closer stations carry more weight. This is groundwater near the district, not a measurement in the watercourse itself. The standard is the limit that SHMÚ gives for the indicator (for drinking water); a value equal to the standard counts as an exceedance, as it does at SHMÚ. The label "somewhere above the standard" means that the typical value is below the standard but at least one station exceeds it; which one is shown on the tile. Fish are more sensitive to some substances than people are.

00,75

Ammonium

0,005mg/l

far below the standard

Standard 0.5 mg/l. Range 0.005 to 0.05 mg/l, 3 stations.

00,75

Nitrites

< 0,01mg/l

not detected

Below the limit of quantification (0.01 mg/l), standard 0.5 mg/l. 3 stations.

075

Nitrates

7,1mg/l

far below the standard

Standard 50 mg/l. Range 0.5 to 15.8 mg/l, 3 stations.

012

Oxygen

2,76mg/l

low oxygen

Mark on the dial: 9 mg/l, the guideline for salmonid waters. Range 0.5 to 9.09 mg/l, 3 stations.

020

Water temperature

10,6°C

moderate

Range 10.5 to 10.8 °C, 3 stations.

510

pH

7,13

suitable for fish

Range 7.06 to 7.45, 3 stations.

08

Water hardness

3,9mmol/l

hard

Range 3.9 to 4.05 mmol/l, 3 stations.

00,3

Iron

0,001mg/l

above the standard somewhere

Standard 0.2 mg/l. Range 0.001 to 2.88 mg/l, 3 stations. Above the standard: 1 of 3 (Nizna – Huc-10/1, 6.5 km from the fishing district).

00,075

Manganese

0,001mg/l

above the standard somewhere

Standard 0.05 mg/l. Range 0.001 to 0.081 mg/l, 3 stations. Above the standard: 1 of 3 (Nizna – Huc-10/1, 6.5 km from the fishing district).

0375

Chlorides

4mg/l

far below the standard

Standard 250 mg/l. Range 1.8 to 39.4 mg/l, 3 stations.

0375

Sulfates

29,5mg/l

far below the standard

Standard 250 mg/l. Range 27.4 to 38.1 mg/l, 3 stations.

0188

Conductivity

66mS/m

close to the standard

Standard 125 mS/m. Range 64.9 to 71.7 mS/m, 3 stations.

0150 %

Metals and metalloids

55% of standard

close to the standard

Highest: Aluminium 0.12 mg/l (60% of the standard, 4 km from the fishing district). 3 stations.

How it affects fish and the water
Ammonium
Ammonium ions are not very toxic in themselves, but depending on pH and temperature part of them turns into ammonia (NH₃), which damages the gills and stresses fish. The higher the pH and temperature, the more ammonia there is (Emerson et al. 1975). The repealed Directive 2006/44/EC gave a guideline of at most 0.04 mg/l of ammonium for salmonid waters and 0.2 mg/l for cyprinid waters.
Nitrites
Nitrites are toxic to fish: they pass through the gills into the blood and turn hemoglobin into methemoglobin, which does not carry oxygen, so fish "suffocate" even in oxygenated water. Salmonids are the most sensitive; chlorides in the water reduce the toxicity (Lewis and Morris 1986). Directive 2006/44/EC gave a guideline of 0.01 mg/l for salmonid waters.
Nitrates
Nitrates do not harm adult fish immediately, but they feed algae and plants and so contribute to over-fertilization and nighttime oxygen crashes. For sensitive aquatic animals (salmonids, amphibians, some invertebrates) Camargo et al. (2005) recommend keeping nitrates below 2 mg of nitrogen per liter, which is about 9 mg/l of nitrates.
Oxygen
Fish, especially salmonids, need a lot of oxygen. Directive 2006/44/EC gave a guideline of 9 mg/l for salmonid waters (in at least half of the measurements) and never less than 7 mg/l. Groundwater from deeper layers often has less of it; in the stream it is re-oxygenated only after it emerges.
Water temperature
Groundwater has an almost constant temperature throughout the year. Inflow from springs can therefore cool a stream in summer and warm it in winter, and such sections often serve as refuges for cold-water fish (Hayashi and Rosenberry 2002).
pH
Fish tolerate a pH of roughly 6 to 9 (Directive 2006/44/EC). Outside this range the gills are damaged and the toxicity of ammonia and metals changes.
Water hardness
Harder water (more calcium and magnesium) is better for fish: calcium protects the gills and reduces the toxicity of metals such as copper and zinc (Pagenkopf 1983), and keeps the pH stable. Soft water is more sensitive to metals and to acidification.
Iron
Iron is dissolved in groundwater at depth. When the water reaches the air, it oxidizes and precipitates as brown flocs that clog gills, cover gravel with eggs and invertebrates, and destroy shelters (Vuori 1995).
Manganese
Manganese is natural in deeper groundwater. For fish it tends to matter less than iron; the standard applies mainly because of the taste and color of drinking water.
Chlorides
Chlorides come from road salt, fertilizers and waste. The US EPA (1988) set 230 mg/l for long-term protection of aquatic life and 860 mg/l for short-term.
Sulfates
Sulfates are common in groundwater; they come from rocks (for example gypsum), fertilizers and mines. Together with chlorides they raise the mineralization of the water; the standard of 250 mg/l is set for drinking water.
Conductivity
Conductivity shows the total amount of dissolved salts. A higher value in groundwater is often natural (limestone, gypsum), but a sharp increase in a stream points to an inflow of salts from roads, mines or waste.
Metals and metalloids
Copper, zinc, nickel, cadmium and mercury are toxic to fish even at low concentrations, more so in soft water than in hard water (Pagenkopf 1983). The groundwater standard is set for drinking water, not for fish.

Sources

  1. Camargo, J. A., Alonso, Á., Salamanca, A. (2005): Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates. Chemosphere 58, 1255–1267.
  2. Lewis, W. M., Morris, D. P. (1986): Toxicity of nitrite to fish: a review. Transactions of the American Fisheries Society 115, 183–195.
  3. Emerson, K., Russo, R. C., Lund, R. E., Thurston, R. V. (1975): Aqueous ammonia equilibrium calculations: effect of pH and temperature. Journal of the Fisheries Research Board of Canada 32, 2379–2383.
  4. Directive 2006/44/EC on the quality of fresh waters needing protection or improvement in order to support fish life (repealed in 2013; we give its values here only as an expert guideline).
  5. Vuori, K.-M. (1995): Direct and indirect effects of iron on river ecosystems. Annales Zoologici Fennici 32, 317–329.
  6. Pagenkopf, G. K. (1983): Gill surface interaction model for trace-metal toxicity to fishes: role of complexation, pH, and water hardness. Environmental Science & Technology 17, 342–347.
  7. U.S. EPA (1988): Ambient Water Quality Criteria for Chloride. EPA 440/5-88-001.
  8. Hayashi, M., Rosenberry, D. O. (2002): Effects of ground water exchange on the hydrology and ecology of surface water. Ground Water 40, 309–316.

Fish, wildlife, plants and hazards around the waterWildlife and hazards by the water (GBIF)Game animals, birds, plants and hazards (bear, ticks, mosquitoes, giant hogweed) that people have recorded around the water. It is not part of the fishing conditions score and is for information only.

Species that have been observed or recorded around the water. Wildlife, plants and hazards do not enter the fishing conditions score and are for information only. The name of a species leads to its page.

CaddisfliesWildlife

Caddisflies

many records
Most records: July.
About the species

Insects whose larvae, in many species, build protective cases from pebbles, sand or plants.

MallardBird

Mallard

many records
Most records: May.
About the species

The most common duck; it nests by almost every water with bankside vegetation.

Grey heronBird

Grey heron

protected speciesmany records
Most records: September.
About the species

It stands in the shallows and lies in wait for small fish. It is easy to see along the banks of ponds and slow streams.

Mute swanBird

Mute swan

protected speciesmany records
Most records: September.
About the species

A large white waterbird that nests by slow waters, reservoirs and ponds with vegetation.

Common kingfisherBird

Common kingfisher

protected speciesquite a few records
Most records: December.
About the species

A small bird that dives for little fish. It nests in steep banks of clean streams.

MayfliesWildlife

Mayflies

quite a few records
Most records: July.
About the species

An insect with aquatic larvae. Adults live only briefly and hatch all at once in swarms.

Fire salamanderWildlife

Fire salamander

protected speciesquite a few records
Most records: September.
About the species

Black with yellow spots. Lives in deciduous forests by clean mountain streams; the larvae develop in the stream.

Common toadWildlife

Common toad

protected speciesa few records
Most records: June.
About the species

The largest native toad. In spring it migrates to water, where it breeds.

Eurasian beaverWildlife

Eurasian beaver

protected speciesa few records
Most records: October.
About the species

A herbivore that changes the stream and its banks with dams and burrows. It is protected. It creates shallows and pools where fish and insects thrive.

Grass snakeWildlife

Grass snake

protected speciesa few records
Most records: May.
About the species

A harmless snake with two yellow spots on the nape. It swims well and hunts frogs, fish and newts.

Eurasian otterWildlife

Eurasian otter

protected speciesa single record
Most records: November.
About the species

It hunts fish, crayfish and frogs. It is strictly protected, and its presence is considered a sign of fairly clean water with plenty of fish.

Pond sliderWildlife

Pond slider

invasive speciesa single record
Most records: August.
About the species

A non-native turtle from America that got into the wild from home pet keeping. It is invasive in Europe.

Black alderPlant

Black alder

quite a few records
Most records: August.
About the species

A riparian tree whose roots reach below the water surface.

Japanese knotweedInvasive plant

Japanese knotweed

invasive speciesquite a few records
Most records: October.
About the species

An invasive herb from East Asia that forms dense stands up to three metres tall.

Common reedPlant

Common reed

quite a few records
Most records: July.
About the species

Tall grass that forms extensive reed beds around ponds and on banks.

Himalayan balsamInvasive plant

Himalayan balsam

invasive speciesquite a few records
Most records: September.
About the species

An invasive plant from the Himalayas, up to two metres tall, with pink flowers. It overgrows the banks of watercourses.

Yellow flag irisPlant

Yellow flag iris

quite a few records
Most records: June.
About the species

A tall wetland plant with yellow flowers that grows on damp banks.

Broadleaf cattailPlant

Broadleaf cattail

quite a few records
Most records: July.
About the species

A wetland plant with a brown cylindrical fruiting spike.

Giant hogweedRisk

Giant hogweed

to be reckoned withinvasive speciesa few records
Most records: January.
How to protect yourself

An invasive plant that grows along stream banks and on wet meadows. In sunlight its sap causes skin burns.

How to protect yourself: Do not touch it and do not walk through the vegetation. If the sap gets on your skin, wash it off with water and soap and protect the area from the sun. See a doctor for larger burns.

Wild boarRisk

Wild boar

to be reckoned witha few records
Most records: February.
How to protect yourself

It comes to the water to wallow and drink, mainly at dusk and at night.

How to protect yourself: A wild boar sow with piglets can be aggressive. Keep your distance, do not spend the night on a game trail and do not leave food scraps near the water.

HorsefliesRisk

Horseflies

to be reckoned witha few records
Most records: June.
How to protect yourself

Large biting flies. They are most active on hot, windless days near water and on meadows.

How to protect yourself: They sting painfully, especially in summer around midday. Light-colored clothing with long sleeves and repellent help.

Gray wolfRisk

Gray wolf

to be reckoned witha single record
Most records: March.
How to protect yourself

A shy predator of the forests. It comes to the water at night and at dusk.

How to protect yourself: Attacks on people are very rare. Keep your camp tidy, do not feed wildlife and keep your dog on a leash.

Wildlife, plants and hazards: records come from observations and also reflect where observers move around; they are not density measurements or a guarantee of an encounter. They apply to the surroundings of about 35 × 55 km.

Photo credits

Animal and plant catalog

Source: GBIFUpdated 6 Nov 2026 15:55

Ground under the water: geology, faults and radon

Bedrock, watercourse and springs on the map, values at the location of the water, geomagnetic activity and earthquakes. This is information about the environment; only small hypotheses marked with a confidence level (faults and rocks, geomagnetic storm) enter the score.

The bedrock map needs JavaScript to be turned on.

The map can be panned and zoomed; the ŠGÚDŠ layers are stored on this server. © Dionýz Štúr State Geological Institute. Base map scale 1 : 50,000 (faults and geology); radioactivity and magnetics are coarser.

Values at the water spot

Values at the water spotBedrock radon risk, uranium, thorium, potassium, gamma radiation and magnetic anomaly at a single spot by the water (marked with a dot on the map).

Bedrock radon risk

medium

Common for most of Slovakia.

08

Uranium (eU)

2,8ppm

common

Typical background of the rocks.

020

Thorium (eTh)

8,8ppm

around the crustal average

Natural background of the rocks.

04

Draslík (K)

1,30%

below the crustal average

Natural background of the rocks.

0150

Gamma radiation

55nGy/h

around the world average

Natural background of the bedrock.

SVJZ

Magnetic anomaly (ΔT)

12nT

above the average of the surroundings

Deviation of the magnetic field from the average of the surroundings.

The values apply to a single spot (marked with a dot on the map), not as an average of the whole watercourse or river basin. Radon is a natural tracer in groundwater; the map does not include radon in water, only the bedrock risk.

Mark on the dial: the average of the upper continental crust (uranium 2.7 ppm, thorium 10.5 ppm, potassium 2.3%; Rudnick and Gao 2003) and the world average of the natural outdoor dose 59 nGy/h (UNSCEAR 2000). The needle does not swing towards “good” or “bad”; it only shows where the value lies.

Elevated uranium or radon is only information about the rock. It has no proven significance for bites; it helps to read what bedrock the water comes from.

Faults and springs

Faults and springsThe distance to the nearest tectonic fault on the geological map and the number of springs nearby. Fissure groundwater flows out along faults.
250 m1 km3 km8 km

Nearest fault

up to 250 m

fault nearby

Tectonic fault on the geological map.

Springs and outflows

0

none marked

None within 1 km.

covered by younger sediments

Fissure groundwater flows out of the bedrock along faults and at springs. It tends to be cooler in summer and warmer in winter than the water in the stream, so according to anglers' experience fish stay near such places in extreme weather (summer and winter islands of a more suitable temperature).

However, fresh fissure water can have little oxygen. This is anglers' experience, not a phenomenon measured at this fishing district.

Faults are from the geological map at 1 : 50,000. Springs come from a hydrogeological map that covers only some regions, so zero does not mean there are no springs there.

Rocks and water chemistry

Rocks and water chemistryThe prevailing group of rocks at the water spot and what it usually means for the hardness, pH and richness of the water.

Bedrock at the water spot

Naplaveniny

The prevailing group of rocks according to the map.

Gravels, sands and loams in the valley tell about the valley floor, not about the rock in the catchment. The water chemistry is determined mainly by the bedrock higher up above the spot.

The rock at a single spot does not determine the chemistry of all the water: that depends on the bedrock across the whole catchment above the spot. The figure serves as a hint, not as a measurement.

Geomagnetic activity

Geomagnetic activity (Kp)The planetary Kp index (0 to 9) measures the fluctuation of the Earth's magnetic field. From 5 it counts as a geomagnetic storm. The last 48 hours and a forecast for 24 hours are shown.
09

Kp index

3,0from 9

quiet field

Latest measurement (7 Nov 2026 01:00). The dot on the dial is the highest forecast for the next 24 hours.

Highest forecast Kp in the next 24 hours: 5.0 (geomagnetic storm).

Kp (0 to 9) measures the fluctuation of the Earth's magnetic field caused by the solar wind. From 5 it counts as a geomagnetic storm. Fish, especially salmonids and eels, sense the magnetic field. That their bites depend on Kp has not been shown, though: these are anglers' observations and hypotheses.

The value is the same for the whole of Slovakia. It enters the activity score only during a strong geomagnetic storm (a hypothesis, −1 to −2 points).

Earthquakes nearby

Earthquakes nearbyTremors recorded within 150 km of the water in the last 30 days (GFZ GEOFON catalog).
S

Earthquakes nearby

0tremors

no tremors

Within 150 km over the last 30 days (from magnitude 1.0).

According to angling lore, fish (especially catfish and eels) react restlessly to tremors beforehand or stop biting. This is not reliably proven, and with weak tremors it is coincidence. People mostly do not notice deeper tremors from the Carpathians (for example near Komárno and Dobrá Voda) at all.

The GEOFON catalog is global; weak tremors near Slovakia may not all be in it. It is not counted in the activity score.

Data: © ŠGÚDŠ (geological, geophysical and hydrogeological maps), NOAA SWPC (Kp index), GFZ GEOFON (earthquakes). A link between the geomagnetic field, tremors or radon and fish bites has not been reliably proven, so they are not counted in the activity score. The method is described in Methodology.

From space: what the Copernicus satellites show

Sentinel-2 (optical) and Sentinel-1 (radar), updated roughly every 6 days

  • OvergrowthClean surface
  • ĽadNo ice

The watercourse is narrower than a satellite pixel (10 m). The values are therefore taken from a strip around the fishing district line and from pixels where water mixes with the bank, so they are only approximate and may also show the bank. The water surface area is not assessed for a watercourse, and estimates over the water appear in the image only where the watercourse is wider than a satellite pixel.

The last usable image is 36 days old (1 Oct 2026) because the fishing district was cloud-covered.

Sentinel-2 satellite image of the surroundings of watercourse Blava č. 3 from 1 Oct 2026, Water (NDWI)
Sentinel-2. Contains modified Copernicus Sentinel data 2026.

Surface overgrowth

Surface overgrowthThe share of the fishing district's area where the satellite sees green vegetation (NDVI index above 0.3): floating and emergent plants and reeds at the bank.
0 % of areaClean surface

The share of the area with green vegetation (plants on and just below the surface, reeds at the bank).

0,00,10,10,25 Mar14 May23 Jul1 Oct
Surface overgrowth trend: from 5 Mar 13:00 to 1 Oct 14:00. Latest 0%, lowest 0, highest 0%.

Since 5 Mar 2026: lowest 0% (5 Mar 2026), highest 0% (10 Mar 2026).

A strip of reeds at the banks may also be counted, so values on small areas may appear higher.

Sentinel-2, 1 Oct 2026, 99% of the area cloud-free

Ice on the surface

Ice on the surfaceThe share of the area where the satellite sees ice or snow. It cannot determine the thickness or load-bearing capacity of the ice.
0 % of areaNo ice

The share of the area where the satellite sees ice or snow. Over the last 20 days the highest was 0%.

The satellite cannot determine the thickness or load-bearing capacity of the ice. Never go onto the ice based on this figure.

Sentinel-2, 1 Oct 2026, 99% of the area cloud-free

Data have been stored since 1 Oct 2025 (59 periods of 5 days); the charts show how they develop. Download history (CSV)

Estimates from satellite images with a resolution of 10 to 20 m, not a measurement in the water. They are affected by clouds, shadows, wind and banks. Do not use them to decide about swimming or going onto the ice. Data: Contains modified Copernicus Sentinel data 2026, ESA, Copernicus Data Space Ecosystem. The procedure is described in the Methodology.

Historical images

Changes in the surroundings and nature from 2017 to 2023: how the banks, vegetation and landscape around the water change. The images switch automatically; you can also browse them by hand.

Aerial image of fishing district Blava č. 3 from 2017
2017imaged 22 May 2017
Aerial image of fishing district Blava č. 3 from 2020
2020imaged 22 Aug 2020
Aerial image of fishing district Blava č. 3 from 2023
2023imaged 14 Aug 2023

Orthophoto mosaic of Slovakia © GKÚ Bratislava, NLC Zvolen. The year and day of imaging depend on the location, so individual years may differ in season and weather.