Platichthys flesus / Platichthys solemdali
European and Baltic Flounder
The Brackish-Water Specialist
This guide covers the European flounder (Platichthys flesus) and Baltic flounder (Platichthys solemdali). Both are flatfish of the family Pleuronectidae. They usually carry both eyes on the right side, but left-eyed individuals also occur. During metamorphosis one eye moves to the eyed upper side. That side is mottled olive-grey-brown; the underside is paler. Rough tubercles along the lateral line and fin bases help distinguish these flounders from typical smooth-skinned plaice. Appearance alone does not reliably distinguish the two Platichthys species.
In Finnish it is Kampela, and along the southwestern and Bothnian coasts it has been a quiet, dependable household fish for centuries - never the headline catch of the Baltic table, but a staple of small-boat coastal cooking from Pori and Rauma up to Vaasa and Kokkola. The classic preparations are simple: pan-fried whole with butter and dill, hot-smoked over alder (savukampela), or salted briefly and grilled over an open fire on a beach. The flesh is white, mild, slightly sweet - it absorbs butter and smoke beautifully, and the bone structure of a flatfish makes it one of the easier fish for a guest to eat with their hands.
European flounder (Platichthys flesus) and Baltic flounder (Platichthys solemdali) meet in the Baltic region. Historical genetic samples from the Gulf of Finland show that their relative proportions have changed over the decades. Different spawning strategies link their development to the Baltic's salinity and water conditions.
Season & activity
An editorial example for Baltic-coastal flounders in Finland. Feeding, coastal presence and seasonal movement depend on species, local temperature, depth and food; winter does not imply universal dormancy.
SourcesDiet Spectrum
Flounder are benthic-invertebrate specialists. The diet tracks what the soft bottom produces through the year - molluscs and polychaetes form the steady backbone, crustaceans peak in summer, small fish are an occasional summer bonus.
- Baltic clams (Macoma balthica)
- Polychaete worms
- Mysid shrimp
- Small benthic prey
Growth at a glance
Length and weight as the animal grows.
Sources| Age (Years) | Length | Weight | Size comparison |
|---|---|---|---|
| 1 | 8 cm | 5 g | |
| 2 | 15 cm | 37 g | |
| 3 | 22 cm | 120 g | |
| 4 | 28 cm | 270 g | |
| 5 | 33 cm | 450 g | |
| 6 | 37 cm | 650 g | |
| 8 | 42 cm | 970 g | |
| 10+ | 47 cm | 1.4 kg |
Habitat Requirements
Water Temperature
- Typical conditions
- Varies by species and locality
- Other influencing factors
- Heat and oxygen shortage
Water temperature affects feeding and growth. Look for temperature zones that suit the species and season, from shallow shores to deeper areas.
Oxygen
- Typical conditions
- Adequate oxygen supply
- Other influencing factors
- Prolonged oxygen shortage
Currents, wind and mixing bring oxygen into the water. Temperature and water exchange help you find suitable places for fish to feed and shelter.
Structure
- Typical conditions
- Sand, mud and mixed coastal bottoms
Flounders use soft, mixed and harder bottoms. Sandy patches are practical places to present bottom bait; rock and vegetation are not universal habitat exclusions.
Substrate
- Typical conditions
- Sand, mud and mixed coastal bottoms
Flounders use soft, mixed and harder bottoms. Sandy patches are practical places to present bottom bait; rock and vegetation are not universal habitat exclusions.
Water Depth
- Typical conditions
- Species- and season-dependent
Feeding areas and winter movements vary by species and locality. Do not apply European flounder offshore spawning to Baltic flounder, whose eggs develop on the coastal seabed.
Water Type
- Typical conditions
- Baltic coastal and marine waters
Adult salinity tolerance and successful reproduction are different questions. European flounder has pelagic eggs; Baltic flounder has bottom-developing eggs suited to less saline coastal water.
Fishing Techniques for Flounder in Finland
Flounder is one of the most accessible saltwater fish in Finland and one of the most overlooked by visiting anglers. A light spinning rod, a running ledger rig, and a tub of nereis worms from a Helsinki tackle shop will outfish most expensive setups. The bite peaks at dusk and through the first hours of darkness from late May into October, when flatfish move onto sandy flats in 2–6 metres to feed.
Casting-reel fishing is not free simple angling with one rod and hook without a casting reel. Check age-based state-fee liability and exemptions, plus the rights required for the method, extra rods and actual water. Extra rods on private or municipal waters can require owner permission; public state-owned sea waters have their own regime (Fisheries Act, sections 4 and 7–8; Eräluvat).
Bottom Rig with Worm Cocktail
May - OctThe classic and the most productive method. A 2.4–3.0 m light rod (10–30 g), 0.20–0.25 mm mono or 0.12 braid, and a running paternoster with a 30–40 g flat sinker that holds bottom in mild current. Two size 4–6 long-shank hooks on 25 cm fluoro droppers. Bait the cocktail local anglers swear by: a piece of ragworm (nereis) threaded up the shank, tipped with a small peeled shrimp or a strip of herring belly. Cast 20–50 m, tighten the line, prop the rod, and wait. Bites are a slow nodding pull, not a slam - let it develop before lifting. Check that the actual permission covers this rig and casting-reel fishing; the method is not automatically free simple angling.
Light Drift Fishing from Boat
Jun - SepFrom a small boat, drift sandy 3–8 m flats between archipelago islands with a 20–30 g flat lead and a single baited hook trailing a metre behind. Drift speed under 0.8 knots is ideal - drop a drift sock if the wind is up. Watch the rod tip; flounder thump the bait once and chew. A drifted nereis-and-shrimp cocktail will also pick up perch and the occasional small cod as bycatch, which is part of the fun.
Pier and Jetty Fishing
Jun - SepThis is why flounder belongs on every visiting angler's list. Public piers in Helsinki (Lauttasaari, Vuosaari), Hanko, Turku, and the Pargas-Nauvo island chain hold flounder within casting range from the structure itself - no boat needed. Use a slightly heavier sinker (40–60 g) to hold against pier wash, fish two rods if local rules allow, and target the last two hours of daylight into dusk. Bring a small landing net; lifting a 30 cm flounder up a 2 m pier on light line ends in heartbreak otherwise. Extra rods in municipal or private shore waters need the relevant owner permission unless another explicit right applies; also check state-fee liability. Public state-owned sea-water rules are separate.
Ice Fishing on Sea Ice (Pilkki)
Jan - MarA small balance jig tipped with maggots or shrimp can be worked slowly just above a sandy bottom. Only consider fishing from ice with experienced local guidance and a safe, checked route. Sea ice can be weaker than freshwater ice and change over short distances. Clear, solid ice must be assessed along the entire route; a thickness such as 10 cm at one point is not a safety guarantee. Carry rescue ice picks (naskalit) around your neck, never go alone, and wait for open water if conditions are uncertain.
Where to Catch Flounder in Finland
Flounder thrives along the brackish southern and southwestern Finnish coast - the Gulf of Finland inner archipelago, the Archipelago Sea, and the southern Bothnian Sea - but is absent from the inner Bothnian Bay where salinity drops below this euryhaline species' tolerance.
Helsinki Inner Archipelago
60.1419°N, 24.9384°ECapital-city flounder from public piers and small boats
The sand and mud flats around Suomenlinna, Vallisaari, and Lauttasaari hold flounder from late May through October at 2–5 m depth. Tackle shops in central Helsinki sell fresh nereis worms, and tram-accessible piers put you on fish within an hour of landing at the airport. Evening and first-dark sessions outproduce daylight by a wide margin in summer.
Archipelago Sea (Pargas - Nauvo)
60.1800°N, 21.9000°EThe country's densest flounder water
The maze of channels and sandy bays between Pargas, Nauvo, and Korpo is the heartland of Finnish flounder. Drift the 4–7 m sand flats between islands or anchor over a clean bottom edge and fan-cast bait rigs. Larger, broader fish here than in Helsinki - 30 cm is average, 40+ shows up regularly in late summer.
Turku Archipelago (Airisto - Rymättylä)
60.4518°N, 22.2666°EEasy shore access, mixed-species sessions
The Airisto open water and the bays around Rymättylä combine sandy flounder bottoms with weed edges that produce perch and pike, so a flounder day rarely ends with only flounder. Pier fishing from Naantali and the Rymättylä bridges is reliable from June onward. Water clarity here is better than Helsinki, so fish a fraction of a metre longer leader and slightly smaller hooks.
Southern Bothnian Sea (Rauma - Pori coast)
61.4845°N, 21.4612°ENorthern edge of the range, fewer anglers
Around Rauma, Pyhämaa, and the southern Pori coast the population thins but the fish are unpressured. Salinity is right at the lower edge of flounder tolerance, so they concentrate in specific outer-archipelago bays with cleaner sand and slightly higher salt. Local knowledge matters more here - ask at the harbour. North of Vaasa, don't bother; the species runs out.
