Fish undergoing sex change

Visitors to Bristol Aquarium are having the unique opportunity of watching a fish change sex before their eyes.

The rarely-seen transformation is taking place to a native cuckoo wrasse in the Harbourside attraction’s UK Waters area.

The 40-centimetre-long fish is changing from a female to a male. The process, which is taking place over a period of days, is particularly spectacular as the male cuckoo wrasse is one of the marine world’s most brightly coloured fish.

Bristol Aquarium’s Liv Orchart said: “The wrasse family are highly unusual as they are one of the few fish able to change sex during their lifetime.

“All cuckoo wrasse are actually born female, however some females will turn in to males when they reach maturity depending on the proportion of the sexes in a population.

“The actual transformation is very rarely observed as the fish tend to go to deeper water during the change so it’s literally a once in a lifetime opportunity for us to chart the process.

“We are trying to take photos of the fish every day so we have a permanent record of the changes. The difference between the two sexes is so marked that people often think they are entirely separate species.

“You can see marked changes in colour and pattern from one day to the next and she has already developed the bright blue tail, which is one of the key indicators of a male,” she added.

Among Britain’s most colourful fish, the beautifully-marked cuckoo wrasse is one of seven members of the 300-strong wrasse family to be found in UK waters.

Males have a brilliant blue head with blue and orange markings down their flanks while the females are a coral pink colour with a row of black and white spots along their backs.

When courtship starts, the already colourful male cuckoo wrasse becomes even brighter in order to attract as many females as possible.

See more photos on Bristol Aquarium’s Facebook page.

Issued by Bristol Aquarium. For more information please contact Sarah Moore or Liv Orchart on 0117 929 8929.