The wrasse that’s worth its weight in gold

The wrasse thats worth its weight in gold

Of the eight species of wrasse in British waters the goldsinny is the one you’re most likely to recognize. It only takes a quick spot-check to be sure you’ve got the right wrasse. Its name comes from its coppery gold colour. Several other wrasse also display this skin shade — but the goldsinny has two features that distinguish it.

First, there is an eye-sized black spot on the dorsal fin between the first and fifth spines. Second, and even more distinctive, there is a black spot on the top of the tail stalk just in front of the tail fin. (The cork-wing wrasse also has a tail spot, but it is sited centrally on the tail stalk, not on the top. The much rarer scale-rayed wrasse has a black tail spot and a black spot on the dorsal fin at the back, but this fish is greeny-brown and larger than the goldsinny.)

The goldsinny uses its small forward pointing teeth to scrape tiny food creatures off rocks, seaweed and kelp holdfasts. Mostly these are small crustaceans such as young crabs and sandhoppers, but the fish also takes small mussels, various tube worms and brittlestars.

It also has the habit of picking parasites and loose skin from old wounds on larger fish. Because of these pest-control qualities, the goldsinny is sometimes used to ‘clean’ off fish parasites from salmon in farms off the coasts of Scotland, Ireland and Norway.

Survival strategy

Although some species of wrasse change sex as they grow older (all the young hatching as females, then some becoming male at the age of five to seven years), the goldsinny doesn’t undergo such a transformation. Goldsinnies are born as normal males and females, but some males have been found with female colour markings.

A possible explanation for this may appear if one looks at the habits of some corkwing wrasse. Each population contains males that adopt female markings. These fertile young males use this ‘sex-change’ disguise to sneak into egg-filled nests without arousing the suspicion of the guarding males, and then to fertilize some eggs. This breeding strategy ensures that as many eggs as possible are fertilized. It is possible that the colour-change goldsinny are doing much the same thing.

Spawn patrol

Goldsinny live on algae-covered rocks from low tide level down to about 50m (165ft). They choose rocky areas where they can find a shelter hole with more than one entrance. These often occur on steep, rocky slopes, so although their range is quite large, their choice of home is very specific.

Both sexes live in these rocky areas but the male is very territorial. It patrols around the shelter hole, defending this patch against intruders, and may live there for two or three years. Males have reddish-gold spots on their sides and belly.

Spawning occurs in the summer when the female joins the male in his territory and the pair swim vertically upwards to spawn in mid-water. The eggs hatch in two to four days; by the time they are eight days old, the young fish have eaten all the food in their yolk sac. The young usually live at depths of around 10m (33ft).

As a result of the goldsinny’s choice of habitat – mainly rocky areas – its population is dispersed over a vast area, which gives the impression that it is quite rare. In fact it is a locally common species.