Round Fish or Flat Fish or maybe both!!

You can see weird and wonderful fish on David Attenborough’s deep sea documentaries, but one of the most amazing groups of fish are those commonly seen on your dinner plate. Around the coast of the British Isles are many groups and species of fish, however, one of the most amazing are the Pleuronectiformes which are our very own flatfish. The commercially important species can be split into two sections – the left eye flat fish that include Turbot, Brill, Halibut and Megrim and the right eye flat fish incorporating the Dover Sole, Plaice, Lemon Dab (commonly called Lemon Sole) and Sand Sole.

Brill under cover - photo taken at the London Aquarium

But why are these fish amazing? Well they are born as round fish, in the shape of a salmon for example, then after several months of their larval development a staggering metamorphosis takes place. The gut twists 50 degrees whilst one eye migrates around the head leaving two on one side. The fish then leaves its pelagic environment, drifts to the bottom, and takes up its new demersal lifestyle. The pigment on the top skin can then adapt a colour to its surroundings to prevent detection from predators. The fish then spends the rest of its life flat. It is believed one mayor reason why these fish evolved this change was to take advantage of the sea bed, a less crowded and under utilised feeding ground niche.

A fairly simple explanation of a flatfishes lifestyle, but hopefully it may inspire all to look closely next time they are stood at their fishmongers.