Made like a fin ring

The flounder - all information about fish

Only recently we dedicated a fish portrait to the plaice and took a closer look at this special flattened fish. With the flattened oval body, the clod actually floats on its side. It is similar with the flounder and both flatfish are very often confused with one another. In these fish with a risk of confusion, the dab also joins, which we will look at another time. Today it should be about the flounder, which was by the way fish of the year in 2017. We'll look at the predatory fish's appearance, habitat, reproduction, and diet, as well as giving you some fishing tips.

Flounder wanted poster

  • Synomyme: Butt in many anglers, flinders, ras
  • English name: European flounder
  • Scientific name: Platichthys flesus
  • Order: Flatfish (Pleuronectiformes)
  • Family: plaice
  • Size: 30 to 50 centimeters
  • Weight: up to 3 kilograms on average 300 grams
  • Age: up to 20 years
  • Physique: flat body, oval shaped
  • Scales: small, rough and knotty
  • Coloring: the side facing upwards is brownish, the side facing downwards is white
  • Eyes: on the right side of the body
  • Fin formula: 0 / 53-62, A 0 / 37-46
  • Maul: short
  • Food: crabs, mussels, shrimps, small fish, worms
  • Spawning season: February to May
  • Spawning location: water depths around 50 meters
  • Main fishing season: mid-June to the end of September
  • Fishing technique: surf fishing, boat fishing
  • Cord: monofilament

Occurrence and habitat

The flounder is particularly widespread in the European marine areas. You can find them in the Mediterranean, the Black Sea, the Baltic Sea, the North Sea and also in the waters around the British coast. She especially likes to be in brackish water and likes to live in fjords and bays. During the day they like to dig themselves in the sand and only their eyes peek out. But the predatory fish is also very happy to wander. Because the flounder does not prefer a high salt content, it can also be found in the fresh water of rivers. Flounders, for example, have already been sighted and caught in the Rhine or in Berlin. Hiking in sweet waters is primarily a fad of the young fish. After three to four years, however, they return to the sea. This is then also the time of sexual maturity of the animals.

The name flounder is derived from the Danish flynder, hence the name flinder. Many anglers also simply refer to the flounder as a flounder, usually in combination with the habitat such as sandbutt or elbutt. However, buttes are a completely different species of fish and should not be confused with flounder.

Appearance and characteristics of the flounder

The flounder belongs to the flatfish order and its most striking feature is the flat, brown to slightly greenish appearance of its body. It is oval and asymmetrical in shape and the body is framed on both sides by a fin ring. The body width of the flounder is slightly less than the body length. The flaky coat of the flounder is very rough. On the fully developed lateral line, the scales at the base of the dorsal and anal fin have thickened into small, thorny warts. If you stroke the flounder, it feels really rough and knotty.

The color of the flounder is mostly brownish on the upper visible side, but sometimes turns green. They are often decorated with brown, yellow or black spots. Sometimes the spots are also reddish, which significantly increases the risk of confusion with the clod. The color of the flounder, like the plaice, can adapt to the bottom of the water. The side facing down is usually white. The fins form a fringe that runs around the flounder. The dorsal fin is very long and extends from the eye to the tail stalk. It is not divided, nor does it have spiked rays.

Actually, the eyes are on the right side, as with the plaice, but a great many flounders are left-handers, so that one often assumes that this is one of the distinguishing features of the plaice. In fact, about a third of the flounders have their eyes on the left side of the body. The gap in the mouth is very small and does not reach the eye.

The differences between flounder, plaice and dab

We have now spoken very often about the likelihood of confusion with other flatfish. That is why we want to briefly mention the main distinguishing features between flounder, plaice and dab.

  • Flounders have very rough scales and nodular warts in the area of ​​the dorsal and anal fin. The clods are smooth and have 4-7 bones just behind the eye.
  • Flounders usually have darker, not as reddish spots as the plaice.
  • In contrast to the flounder, the dab has a strongly curved side line and a transparently shimmering underside. The side line of the flounder is only slightly curved, the underside white.

The special mutation of the flounder

In the fish portrait of the plaice, we briefly pointed out that for a long time the scientists could not explain why the fish are so flat and whether this has always been the case. In this context, fossil finds were discovered that show an intermediate stage in the development from laterally symmetrical to asymmetrical fish. The flounder, which belongs to the plaice family, also undergoes this evolution in a very short time in the development from larva to juvenile fish. The eyes move to one side and the right side of the body becomes the top of the fish.

Researchers at the University of Würzburg, together with Chinese colleagues, now want to find out which genes or actors are responsible for this development. They have deciphered the gene pool of the flounder and compared it with that of a distant relative, the sole, and found a major player in the radical body remodeling. On the one hand, the retinoic acid changes the pigmentation of the fish and, on the other hand, it also affects the thyroid hormone and causes one eye to wander to the other side. Light plays a major role in this transformation. The pigments in the eye of the flounder that catch the light are also found in the skin of the larvae. These perceive the differences in brightness, stimulate retin production and thus act on the thyroid hormone. The conversion to the asymmetrical fish is initiated.

Lifestyle and diet of the flounder

Flounders are nocturnal and rather sluggish during the day. When dusk falls, the schooling fish start catching prey. As a predatory fish, it mostly feeds on mosquito and other insect larvae and river fleas in fresh water. In the sea water she goes for small crabs, clams, shrimps and small fish. She loves worms, especially the lugworm and bristle worms.

Reproduction of the flounder

During spawning time, flounders migrate to the coasts of the seas because they need salt water in which the eggs can float. The animals living in freshwater, which become sexually mature at around four years of age, then migrate into the sea and do not return to the rivers. The exact time depends on the temperature. The spawning season of flounders in the southern and southeastern North Sea usually begins in February and continues into May. In northern Norway and on the Kola Peninsula, the fish spawn from late March to early June.

The female lays between 400,000 and two million eggs in an approximate water depth of 50 meters, but it can also be shallower and a little deeper. They are about a millimeter tall and float in salt water. A concentration of 10 o / oo is required for this, otherwise they will sink to the bottom and die. The young flounder feed first on the yolk sac and later on plant and animal plankton. As with the plaice, the transformation to flatfish begins from an approximate height of 1.5 to 3 centimeters. One eye wanders to the other side of the rather small head and the flounders begin to live at the bottom of the water.

The flounder as an edible fish

The flounder is, like the plaice, a very popular food fish, even if it is not found quite as often on our plates. The firm, protein-rich meat is very tasty and soft. The advantage for consumption is that the flounder does not have to be skinned and has very few bones. The preparation methods are very diverse. Flounders are fried, but they can also be cooked very tasty on the grill. The meat is particularly suitable for smoking. If you find great plaice recipes, then just do the same with your flounder. The flounders taste best in the summer months.

Fishing tips for the flounder

If you want to fish for the flounder, the best method is surf fishing. But the chances of success are also good from the boat. The best time to fish is from May to the end of September. But even in October and even November the chances of a flounder are still quite high. At this time, the fish have already migrated into deep waters, so you have to get on the boat. As already mentioned, the flounders are nocturnal animals, so the best time of day is the onset of dusk and night. Also read our post on night fishing.

Choosing the right spot for the flounder target fish depends heavily on the time of day. The fish is usually caught standing in waist-high water on beaches, in the brackish water bays or in the harbor basin. Since the animals migrate into the shallow water at dusk, sandbanks with throwing distances between 20 and 120 meters are ideal. Fairways can also be very catchy.

If you fish from the bank, the best way to do this is with a special surf rod with which you can cast long distances. Use a monofilament line or special surf lines such as club lines. A stationary reel or a good multiplier should be standard. When surf fishing you use special surf hooks, when fishing from a boat you use long-limbed hooks. Most anglers swear by the lugworm as bait, which the flounders just love to eat. But don't take specimens that are too large, because the mouth of the flounder is quite small. You will achieve particularly good results if you switch a bait spoon (butt spoon) or a few pearls behind the bait. From the boat you can also jig with rubber baits. As you know us, we will certainly also write a very detailed guide to flounder fishing with lots of tips on assemblies, trapping sites and baits.


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