How to read an Adriatic fishing chart: depths, habitats, scores, and what it is not

An Adriatic fishing map shows three layers for the angler: depth contours from EMODnet Bathymetry, Folk-5 seabed class from EMODnet Geology, and a species habitat score by technique. It is a planning chart, not a navigation chart.

Written with the two Adriatic anglers who build it. Updated 2026.

What layers does an Adriatic fishing map show?

Three stacked layers: depth (contours, colour tint and soundings), Folk-5 seabed class (mud to muddy sand, sand, coarse, mixed, rock and boulders) and a species habitat score. Depth and seabed are free; most species scores need a pass. Read class, then metres, then score.

A fishing map is that stack on one base map. It is not a postcard of the coast and it is not the sheet you put under the helm. You read it at a tapped sea point: substrate class first, metres second, species habitat score third, for the technique you will actually fish.

The stack is produced that way because the two public layers have named sources and the third is computed from them. Depth is published as EMODnet Bathymetry. Seabed class is published as the geology substrate product in five Folk classes. The score is the planner model. The worked example on this page is what AlgoCatch is and who it is for.

Fishing layers cover Trieste–Ancona, Slovenian coast, Istria, Kvarner, Dalmatia. That box is the product, not a worldwide chart and not a request form. For the coast list, open which Adriatic coasts the map includes. Place guides live under the fishing coasts. Other overlays (sea temperature, currents, effort, 3D) have their own pages.

On Free you get depth, Folk-5 seabed and gilthead habitat. Other species layers need a pass. This page does not list plans. Tourist maps skip the stack. Nautical viewers give metres for the helm and skip class and score. That is what a fishing map shows that those pages do not: named layers, in a fixed reading order.

Read the Folk-5 seabed class first. If the class does not match the fish you came for, change place before you spend the evening on a beach that looked right from the road. Metres decide whether you are in the band. The score only ranks pins after those two reads are honest.

Where does the depth on an Adriatic fishing map come from?

From the EMODnet Bathymetry digital terrain model, gridded at 1/16 arc-minute (about 115 m), compiled from survey soundings and satellite-derived depth with gap fill. It is a planning number for reading structure, not a navigation depth.

Every contour and every tinted cell is a cell on that digital terrain model, not a skipper's sounding from this morning. The planner does not invent metres. It draws a published grid.

The DTM compiles survey soundings and satellite-derived bathymetry, then fills gaps, then samples the basin at 1/16 arc-minute, about 115 m. A contour is an average over that cell. A boulder or a 3 m ledge inside one cell will not draw. Two cells a short walk apart can look smoother than the rocks you can see from the mole. That is a grid, not a lie, and it is why a tap is a planning read.

When you stand on a mole and the water in front of you changes from 4 m to 9 m inside one boat length, the tint may still draw one colour. The cell is about 115 m across. Use the colour to find the step, then tap two or three points along it. The useful fact is the step, not the centimetre.

The product documentation states the grid size and the compilation mix. This page stops at dataset, grid and mix. It does not walk the update cycle or the data licence. Those belong on the provenance cluster.

Treat contours as structure indicators. Tight spacing means a slope. Wide spacing means flat bottom. Do not treat a tapped metre as a safe-water depth and do not steer by it. If you need the compilation story, open where the EMODnet depth data comes from.

How do you read depth contours in the planner?

Zoom to level 10 or closer: contours and the depth tint appear, with soundings as a third layer. Tap the water to read depth and seabed class at that point. Tight contours mean a slope; wide spacing means flat bottom.

The planner draws depth three ways once you reach zoom level 10: colour depth tint, chart contours, and depth soundings. Inspect is the tap on the water. It returns metres and class at that sea point. Tap the shoreline and the pin snaps to the nearest sea point, so you do not read a land cell as if it were a cast.

Zoomed out, the basin is a wash of colour and you cannot see a fishing edge. At zoom level 10 the tint separates shallow from deep and the contours start to show where the bottom turns. Soundings are the third check: a printed metre on the water, not a substitute for Inspect. If you tap a mole and the read jumps to 6 m of sea, that is the snap rule doing its job. You are planning a cast into water, not a walk on stone.

Those display rules are product facts. On 12 June 2026, west of Poreč, an Inspect tap at 7 m on a sand edge sat within a few metres of the fishfinder under the hull. That is the match you want on a first pin: close enough to trust the contour pattern, not identical to a single ping.

Find the slope with tight contours, then tap it. Confirm class and metres before you commit the session. If the pin is mute, shift ten to thirty metres and tap again. Do not turn contour spacing into a casting distance on this page. The full contour method, including drop-off edges and worked reads, is how to read depth contours for fishing.

What does the Folk-5 seabed layer show?

The EMODnet Geology substrate class at each point in five Folk classes: mud to muddy sand, sand, coarse substrate, mixed sediment, rock and boulders. Class tells you which species can hold there before depth tells you how deep.

The seabed layer is a Folk-5 substrate class, not a photo of the beach and not a skipper's "looks rocky". Each cell carries one of those five names. You read the name at the same tap that returns metres.

The source is EMODnet Geology: the public seabed substrate map, reclassified to the five Folk classes in that fixed order. Fishing pages that say "sandy" or "rocky" from a snapshot skip the standard. This layer names the standard and the source.

The five names, in order, are mud to muddy sand, sand, coarse substrate, mixed sediment, rock and boulders. That list is the layer. There is no sixth "weedy" class and no "harbour wall" class. If the tap returns sand, you plan a sand session. If it returns rock and boulders, you plan a rock session. The metres come after that decision, not before.

Read class before metres. Wrong bottom blanks the session even when the band looks perfect. A gilthead pin on rock is a wasted evening; a dentex pin on open sand is the same waste the other way. What each class means for a given species is what each Folk-5 seabed class means for fishing.

What is the species habitat score layer?

A habitat suitability score per species and technique, computed from depth, seabed class and species preference and shown Poor to Hot. Gilthead is free; 60+ gilthead spots and other species need a pass. Not a fish count.

The score measures habitat suitability. It does not mark fish under the pin and it does not log last week's catch. Depth band, Folk-5 seabed class and species preference (by technique) go in; a Poor to Hot tier comes out.

Species preference follows published ranges (FishBase, FAO; T2). The planner applies those ranges to the two layers under the pin. Gilthead habitat is on Free. Other species layers need a pass. This page does not explain weights or why 60 is the cut; that sits on the score pillar.

Poor to Hot is a suitability ladder, not a catch forecast. Poor means the band or the class (or both) miss the species. Hot means both line up for the technique you picked. The free gilthead layer lets you practise that read without a pass. Once you want the other species, you unlock them elsewhere; the definition of the score does not change.

A habitat suitability score that looks Hot on a phone in January is still only a match of depth, class and preference. Wind, pressure and whether anyone has fished the edge this week sit outside the layer.

Use the tier to shortlist. Then verify class and metres on the water. A Hot pin on the wrong bottom is still wrong. A Fair pin on the right edge can be the session. For the scale and the limits, read what the habitat score means.

Why does depth decide the technique and the species?

Each target holds in a depth band over a bottom type: gilthead seabream 2–30 m over sand and seagrass edges, common dentex 15–50 m on rock drop-offs, and a trolling route follows one contour band such as 20–35 m.

Depth band plus bottom decides the fish and the method. Species hold where both match. A trolling lure that leaves the band is fishing empty water even if the plotter still looks busy.

From the rocks, the decision is a cast: are you in 2–30 m on a sand or seagrass edge, or are you throwing onto a shelf that is already too deep and too hard? From a small boat the decision is a line: stay in one contour band, or sit the rock drop in 15–50 m. Mixing those two games on the same pin is how evenings die.

FishBase and FAO publish the ranges. The rows below add a dated session so the band is a place, not a slogan. Only these three uses sit on this page.

Use	Depth band	Bottom	Technique	Dated session
Gilthead seabream	2–30 m	Sand and seagrass edges	Shore or light boat	12 June 2026, west of Poreč, 7 m, sand edge, evening shore
Common dentex	15–50 m	Rock drop-offs	Troll or sit the edge	3 May 2026, Cres (Kvarner), 32 m, rock, boat
Trolling route	One band, e.g. 20–35 m	Follow the contour	Trolling	18 August 2026, Savudrija shoals, 24 m on that band

Those three dated reads are field notes, not catch reports. The Poreč sand edge was an evening shore session in the gilthead band. The Cres rock at 32 m was a boat session in the dentex band. The Savudrija 24 m run was a trolling contour inside 20–35 m. If your tap is outside the band or off the bottom type, change the mark.

Cast the sand and seagrass edge inside 2–30 m for gilthead. Hold a rock drop in 15–50 m for dentex. Keep a trolling contour band, for example 20–35 m, if that is the session. Then pick which technique fits the bay and check a spot for gilthead or dentex.

How does Adriatic depth change from Trieste to Dalmatia?

The northern shelf is mostly under 50 m and the Gulf of Trieste under 40 m, so structure is subtle. Jabuka Pit reaches about 270 m mid-Adriatic; the South Adriatic Pit is over 1,200 m, beyond shore and small-boat fishing.

The basin is shallow in the north and deep in the south. The same planner therefore reads as a sand-and-mud shelf from Trieste toward Poreč, then as steep rock edges from Kvarner into Dalmatia.

On the northern Adriatic shelf, mostly under 50 m, a drop-off is often a two-metre wrinkle that you will miss if you only look at the beach. The Gulf of Trieste, under 40 m, is flatter still: moles, seagrass edges and small colour changes do the work. That is gilthead and light-tackle water, not a canyon.

From Kvarner south the same colour scale starts to show real walls. Rock comes up next to deep water. A 15–50 m dentex edge can sit a short run from a harbour. You still do not fish the hole over 1,200 m. You fish the shoulder the island gives you. Mid-basin the pit named above is about 270 m; the southern basin is over 1,200 m. Those figures are published bathymetry, not folklore.

Expect flat, subtle edges and gilthead water on the northern shelf. Expect rock drop-offs and dentex water from Kvarner south. Do not plan a shore session around the basin maximum. Plan the local band on the map in front of the town where you sleep.

How accurate is the depth, and how do you check it?

Near-shore depth is mixed-resolution; small differences from a hull unit are normal. The planner asks "Does this depth look right?" so you confirm against a fishfinder, chart or anchor rope; it skips the prompt when GPS accuracy is worse than ±50 m.

The DTM is a mixed-source grid. Near shore, cells mix dense survey with thinner coverage. A few metres of disagreement with the unit under the hull is expected. A wildly different number is a reason to move the pin or to answer the prompt.

That mixed-resolution note is why two honest anglers can argue about a pin. One read the grid. The other read the unit under the hull. Both can be right inside a few metres. The planner's job is to collect the comparison, not to pretend the cell is a survey stake.

The in-app line is exactly "Does this depth look right?". The three references are the unit, a chart, or the anchor rope. The prompt is skipped when GPS accuracy is worse than ±50 m, because a confirmation tied to a bad fix would train the wrong cell. When the fix is worse than that, walk until it tightens, or tap again from a known mole, then answer the prompt.

Verify the first tap of the day against the unit, then trust the contour pattern more than any one cell. If you need error ranges by bay or the correction workflow, use the supporting pages linked in the FAQs. Do not treat a mixed-resolution cell as a navigation sounding.

What does an Adriatic fishing map not show?

It is not a navigation chart: no aids to navigation, no harbour approaches, no safety depths. It does not count fish or log catches, and it does not sell licences. Use a plotter and official charts on the water.

A fishing map is a planning surface with three plain non-claims. It carries habitat suitability, not a fish count. It carries planning depth, not a helm sheet. It does not sell a recreational licence.

It is a planning chart, not a navigation chart. That sentence is the whole helm rule. There is no list of lights or buoys here, and no safety depth you may lean on. Habitat suitability is not a fish count: a strong score is a match of band and class, not a promise that fish sit under the pin tonight.

The product statement is the first source. The official Croatian issuer for the sea licence is ribarstvo.mps.hr. This page does not list chart symbols, aids, or what to carry aboard; that comparison is fishing map vs nautical chart. Navionics for navigation, catch logs on the social pin app, this map for the bottom: AlgoCatch vs Navionics vs Fishbrain.

Plan the session here. Run the boat on a plotter and official charts. Buy the licence at the official shop. Do not steer by a tap, and do not skip the licence because the map opened.

Open the free map on the stretch you will actually stand on or drift over. Treat the class at that point as the go or no-go: if it is not the bottom your species uses, change place before you burn the evening. Then lock the depth band (2–30 m sand edge, 15–50 m rock drop, or one trolling contour). Only after that choice, see which AlgoCatch plan unlocks the species layers.