Fishing for Flounder

The shore angler often looks on a flounder as a consolation prize rather than a triumph. But the species has colonized the brackish fringes of our coast in a way that no other fish has.

There cannot be many shore fishermen who have not caught or at least seen a flounder, Platichthys flesus. Anyone who has fished an estuary or wide shallow bay will have encountered this flatfish which, while it has little reputation as a fighter, and even less as a fish to grace the table, is nevertheless a dependable catch.

From August to mid-winter the flounder will feed away from the sea, sometimes passing through the tidal reaches of large rivers to seek its food in freshwater. As a result of this there are many examples of coarse fishermen taking flounder on worms while fishing the East Anglian land drains and other slow-moving waterways.

Feeding habits

The flounder feeds on worms, some insect larvae, and small crustaceans. Most of its food is gleaned from the mudflats and areas of soft sand that border marshland. The current brings food to the invertebrates which live in mud and sand and the flounder takes constant advantage of this feeding pattern and crops these rich territories for food.

The flounder is a member of the plaice family. It belongs to the right-handed group of flatfish, having both its eyes and its mouth on the right side of the body. There is wide variation in colour but a dull brown is usual. Many flounders have orange spots, which lend it a plaicelike appearance. These spots, which are light in hue, should never be relied on to identify a flounder. Look instead for a line of raised tubercles, like small, domed scales, along the base of both the anal and dorsal fins. Behind the head there is another more pronounced line of tubercles which extends to the beginning of the lateral line. Both of the fins that edge each side of the body have a wide section at the back, which gives the flounder a definite angular shape, whereas the plaice and the dab have evenly tapered fins.

A further problem of identification arises from the fact that the flounder is not always coloured on the right side of the body. Examples with colouring on the left side only, and even fish that are brown on both sides, have been recorded. To complicate matters further, there is evidence from British and Scandinavian waters of hybridization between flounders and plaice. The Flounder hybrid is common in the North Sea and the Baltic. The fish looks more like a plaice, has diluted spot colour and a smoother skin than the flounder. Fin-ray counts in these hybrids fall between those of the plaice and flounder.

The flounder begins its journey from inlets, rivers and lagoons to the spawning grounds in late December. Spawning takes place in February in water of 10 fathoms or more. The females release up to two million eggs each and these, when fertilized, float to the upper layers of the sea. The eggs will hatch in about a week if the temperature is around 10 °C. Colder conditions prolong the process and slow developing.

When hatched, the tiny larvae resemble most of the round-bodied species, having an eye either side of the head. When the egg sac has been absorbed they take up an exclusively bottom-dwelling existence.

The curious change to the mature flatfish now begins. The symmetrically shaped body starts to broaden out and the anal and dorsal fins appear as fringes to it. An eye gradually moves from one side of the head to come to rest on the coloured side. Now, with the eyes in this position, and the anal and dorsal fins on the edge of the body and clearly separated from the tail or caudal fin, the metamorphosis is complete. It is difficult to generalize about the length of time this process takes as it depends on many factors, water temperature and the availability of food being the most significant.

If food is plentiful, flounders will grow quickly, to reach 3in-4in in length in their first year. Sexual maturity, when the fish should weigh about 10 oz, is reached in the third year in the male, and a year later in the female. As with all fish, growth is relative to feeding and other environmental conditions rather than to age.

To catch flounders the angler needs to identify their feeding territory. Shallow water, where the seabed is composed of the sand and mud mixture that offers a breeding ground to lugworm and ragworm, is likely to hold flounders. Patches of small stones that support weeds are ideal crab, and so flounder, habitats.

Tides that move surely but gently across mudflats provide the conditions that both flounders and their prey require.

During the day the flounder spends most of its time buried in the seabed, with only the swivelling eyes showing, ever searching for the movement of crab or worm. The tiny spurts of sand sent up in the quiet water as a crab scurries from one cover to another will alert the flounder to its food. This can be simulated by slowly reeling a baited hook across the sand or using a blade flounder spoon, which spins slowly, raising the sand in flurries.

In mudflats there are channels and gullies cut by the ebbing tide and the freshwater running out from the river. At low tide these channels are the only places holding water. The flounders retreat into them, lying along the edges of the fast water in anticipation of food being swept downstream. The angler’s tactics now must match the situation. It is very difficult to fish a static bait here or even to reel a baited spoon across stream, but a rolling ledger can be cast across the channel and the whole stretch fished by a series of tightly spaced arcs.

Successful flounder fishing depends a great deal on identification of the bite. With its small mouth, the fish takes the worm slowly. This takes time and is registered at the rod tip by a series of sharp jerks. It is easy at first to overreact, striking before the fish has taken a firm hold on the bait.

Using a crab as bait requires a different approach. A dead, hooked crab gives off a strong smell in the water, which attracts fish. Being fairly fragile, though, it can be torn off the hook easily. The bait can be made more secure by tying it on to the hook with elasticated thread, although striking becomes more difficult to judge.

Flounders can also be taken on float-fished baits, and the greater degree of control this method gives over the way the bait is presented is a strong reason for employing it. Flounders move with tidal currents, but they do not have to. Much of their food will be brought to them by the out-flowing stream of the river or on the flooding tide. If the angler’s bait can be trotted with the current flow it will reach the fish in a natural-seeming way.

There are times when the flounder is caught from open beaches and sandy strands. In the spring and early summer flounders feed close inshore to recover from the rigours of spawning. The bass fisherman will often have his bait stolen by a flounder which has ventured into the surf for the feed that washes about there. In times of stiff onshore breezes and pounding surf these flatfish will stay just outside the line of breakers, where the power of the driving surf has less impact on bottom-feeding fish.

Winter fishing on a cod beach also produces the occasional flounder. At this time the fish are setting off for deep water, prior to breeding, but will stop to catch an easy feed thrown up on to the shingles by winter gales.

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