Common all around the British Isles, the dab is easily distinguished from other right-eyed flatfish by its sharply curved lateral line and by finely serrated scales that feel rough when rubbed from tail to head. Another species, the long rough dab is a close relative, but it is fairly rare and has a straight lateral line.
The upper side of the dab is a sandy brown colour, which helps it to blend in well with its surroundings. Some fish may have a few orange speckles, but these are not as well developed as those of the plaice. Like most other flatfish, the dab’s anal and dorsal fins are long with jointed rays.
The type of sea bed determines whether or not dabs are to be found. They appear from the shore down to 150m (490ft), but sandy ground up to 40m (130ft) is their favoured habitat. Sandbanks, bays and generally flat ground attract them in their thousands, and they’re often found in the mouths of estuaries, though they cannot tolerate as much fresh water as flounders. Their habitat is also dependent on food supply – they eat anything that is small enough. Sandeels are plentiful around banks and this is their main food source.
The dab – and also the sole – has a curious way of feeding. The fish raises its head and the front part of its body and then waits for a worm or shellfish to emerge. Then it strikes rapidly, biting down on its prey. Dabs fatten up during summer and autumn and then move to deeper offshore marks with the onset of winter.
When and where
Sometime between January and June, according to the water temperature, mature fish of three years and older are ready to spawn. Those around Britain and Ireland do so in March and April. Unlike some species, dabs do not have specific spawning sites. The female lays 50,000-150,000 eggs, after which the adult fish move in towards warmer coastal waters to feed.
The eggs float near the sea’s surface and hatch after a week or two. Once they have absorbed their yolk sac, the fry feed on the plankton around them. When they reach a length of 12mm (/ain) they begin to move down to the sea bed. Here they change from being round-bodied fry to flatfish – the body flattens and the left eye migrates to sit next to the right. Although it is not unusual to find left-eyed flounders, dabs reversed like this are quite rare. Because of this unusual metamorphosis, flatfish have earned the name heterosomata, meaning twisted body. Although dabs are not as commercially important as plaice or halibut, they are often taken incidentally in a trawl, where a minimum size limit of 20cm (8in) applies.