The ballan is our largest and most heavily built wrasse and can reach up to 50cm long. It is closely related to the cuckoo (pictured) and goes through the same sort of sex change, but lacks the obvious colour coding that tells us casual observers the current state of play. Ballans occur in a variety of colours, seemingly independent of sex, but presumably other ballans know the score.

Groups of the little rock cook wrasse can often be seen accompanying much larger ballan wrasse. Rock cooks act as cleaner fish, nibbling off parasites or debris from the ballans scales, and also seem eager to wait for any scraps that arise from their larger companions feeding activities.

Despite all the variations in colour scheme, habits and size, the different wrasse share some common features. They all have bodies that are taller than they are broad, large prominent lips and a characteristic swimming motion. Unless in a particular hurry, their bodies and tails appear to remain quite stiff while their pectoral (shoulder) fins row them along.

Male corkwing wrasse, in their bright claret and blue breeding colours, can be found defending their nests. They invite females in to lay their eggs but some other males, posing as females, might try to sneak in and fertilise any eggs already laid, before the resident male gets the chance.

All cuckoo wrasse are born as females. Some later turn into males, changing from a pretty coral pink (with a row of distinctive black and white blotches) to a livery of yellows, oranges and a brilliant blue. The gaudy male usually has a harem of several females and, if he dies, one of them will change sex to replace him.

Five species of wrasse are abundant in our waters, the cuckoo, ballan, corkwing, goldsinny and rock cook. The cuckoo wrasse tends to inhabit slightly deeper water than the others but, in the summer months, it is common to see all five on a single dive.