- Scientific name: Platichthys flesus (previously Pleuronectes flesus)
- Also known as: European Flounder, Fluke
- Size: Up to 1ft 8ins and 6lb (UK shore caught typically 1-2lbs), but see below.
- UK minimum size: 11inches (27cm) in length.
- UK shore caught record: 5lb 7oz
- IUCN Status: LC (Least Concern)
- Distribution: Common throughout UK and Irish waters. Live in shallow water often near to an influx of fresh water, favour clear sandy or muddy ground and can travel up rivers far into freshwater territory. Distribution extends into Northern European waters and into the Mediterranean and Black Sea. Also found in US and Canadian waters, although they are not native to these countries (see below).
- Feeds on: Young flounder will eat mostly marine worms and prawns, older fish will add crustaceans and molluscs to this.
- Description: Rounded diamond shape with rough surface along the lateral line. Colour can range from light brown to green to greyish, sometimes with dark orange spots. White underbelly in most flounder, although there can be freak fish with an underside the same colour as the back. The vast majority of flounder have eyes on the right side of their head but a minority have eyes on the left.
Flounder are a common flatfish species found around most of the UK. Due to their wide distribution, willingness to take most baits and the fact that they can come into very shallow water they are a common catch for many UK anglers, and provide many youngsters with their first experience of catching a sea fish.
Distribution and Habitat
Flounder can be found all around the UK and Ireland throughout the year, but in late winter/early spring they tend to move away into deeper water to spawn meaning they turn up in anglers catches less often at this time of year, although they still can be caught. Flounder are found around almost all of the UK and although they are more common in the cooler water around the British Isles and the Nordic countries they can be found in the warmer waters of the Mediterranean and along parts of the north coast of Africa. Flounder travel so far inland they have occasionally also been observed in land-locked Switzerland. Flounders have something of a reputation as an invasive species outside of Europe and are found in US and Canadian waters, including in the Great Lakes. Flounder are not native to the North American continent and it is assumed that they are present there due to being transported across the Atlantic in the ballast water of transportation vessels. Flounder are not thought to have a significant impact on the eco-systems of North America and are not considered a dangerous or damaging invasive species.
Flounder are happy to feed in very shallow water and can sometimes come so close to the shore they are in literally inches of water. Flounder can live in water with a very low salinity level and can travel very far up rivers to the extent that freshwater anglers using earthworms as bait sometimes catch them from locations very far inland. Many anglers looking at marks many miles inland simply do not believe that saltwater fish can be found there, only to be surprised when flounder are caught. Flounder prefer muddy and sandy ground and are usually found in estuaries, large shallow bays and sandy beaches close to where rivers join the sea. Muddy or sandy beaches that hold lugworm and ragworm offer higher chances of flounder catches, especially if they are next to a flowing river or estuary.
Reputation as a Table Fish and Conservation Status
The relative ease which with flounders can be caught make them a dependable catch for UK anglers and they are sought after in sea fishing matches where catching flounder can make the difference between winning or losing. Unlike the similar plaice, flounder are not held in high regard as a table fish and most anglers fish for flounder on a catch-and-release basis. Flounder are not commonly sold to UK consumers and their main use to commercial fishermen can be as bait for lobster and crab pots – in some areas of the UK flounder numbers have been badly hit by commercial fishermen taking excessive numbers as pot bait. However, elsewhere in Europe flounder are caught commercially and sold for human consumption. Due to its widespread distribution and relatively healthy numbers the flounder is considered a species of Least Concern by the International Union for the Conservation of Nature.
Flounder are usually modestly sized fish, with the vast majority being caught around the UK weighing up to 1lb. A 2-3lb flounder can be considered a good catch from the shore, although the British record is a specimen of 5lb 7oz, caught by B. Sokell on the River Teign in Devon in 1994. This is thought to be close to the maximum size which flounder can reach in the wild. However, the well-respected global fish species website FishBase.org states that flounder raised in fish farms have been able to reach 14kg (30¾lbs), a claim reiterated in the book Aquaculture: Farming Aquatic Animals and Plants (2nd Edition) by John S. Lucas and Paul C. Southgate which was published in 2012.
Confusion between Flounder and Plaice
Flounder can be distinguished from plaice as they are duller in colour, do not have the bony ridge on the back of their head and the tail is larger. See here for a detailed article on identification of the various flatfish found in UK waters. Confusingly, ‘plounders’ also exist. These are flounder/plaice hybrids that exist Scandinavian waters, although they are occasionally caught in the North Sea.
Methods and Techniques to Catch Flounder
Flounder are sometimes caught when going for larger species but specifically fishing for flounder on light gear can be fun, especially in estuaries and harbours where conditions are likely to be calm and having to deal with heavy and rough seas will not be an issue. Specialist flatfish rods are on the market which can be used specifically to fish for flounder and related flatfish species, although bass, spinning or even carp rods can be used instead. Since casting distance is not an issue when targeting flounder rigs with two or three flapping hooks are used and this allows a different bait to be used on each one, and also allows a stronger scent trail to be built up. A main reason for missing out on catching flounder is casting over the feeding fish. They come very, very close to the shore and casts just ten or fifteen yards (or even less) can locate flounder.
As flounder often seek out gullies in the seabed using a plain weight that will roll around and lie in these gullies can be a good tactic to seek out the flounder. The main bait when going for flounder is lugworm and ragworm, although they will also happily take mussel, mackerel and peeler crab. Harbour ragworm (maddies) are a top bait for flounder, with seven or eight of the small worms threaded onto a hook making a top flounder bait. Flounder have a fairly small mouth and often pull at a bait before full taking it in their mouth. Many anglers strike too early and are left confused and frustrated as to why they keep missing bites. Allow flounder bites to develop before striking and reeling in. Long-shanked hooks size 2 – 1/0 are best to use as they present worm baits well and are easier to remove from the flounders small mouth. Some anglers advise using smaller hooks down to sizes 4 or 6, but larger flounder can completely consume hooks this size and it becomes impossible to unhook and return these fish. Light gauge hooks are also the best choice as they cause less damage to the worm baits that are often used to fish for this species.
While the urban myth that cod are attracted to the colour white has been debunked as nonsense, there is plenty of evidence that using beads and sequins on hooklengths does indeed attract inquisitive flatfish such as flounder and also plaice. Anglers adding these to hooklengths often outcatch anglers who do not. Some anglers just put beads on the hooklength, while others alternate beads with sequins. A wide range of sequins and beads are available some of which are specially designed as sea fishing attractor beads, while sequins can be bought from any stationary shop. Similarly attractor spoons are also added to hooklengths. Spoons spin and turn in the tide and can also churn up the seabed which creates an added source of attraction for flounders.