The ubiquitous spotty

by Dr Malcolm Francis

Spotty (male) by Malcolm Francis

Anyone who has snorkelled in New Zealand, or fished off a wharf, is likely to be familiar with the spotty (Notolabrus celidotus) – probably the commonest and most widespread of our reef fishes after the triplefins. Spotties are so common in places that people rarely take much  notice of them. Yet they are endemic to New Zealand (occurring nowhere else in the world), so they are as important to biodiversity as the kiwi or the silver fern.

The abundance of spotties in our coastal waters indicates that they are a very successful and fundamental part of our shallow reef ecosystem. They range from North Cape to Stewart Island and the Chatham Islands, and prefer areas that are sheltered from heavy swells and wave action (in exposed areas they are replaced by the related banded wrasse (Notolabrus fucicola)). Juvenile spotties feed mainly on small crustaceans which cling to kelp plants and other seaweeds, while larger fish eat a wide variety of small animals such as crabs, shrimps, shellfish, brittlestars and worms.

Like all members of the wrasse family, spotties usually swim by sculling along with their pectoral fins, which gives them a comical appearance when seen head-on. But when required, they can use their tails to generate an extra burst of speed. Another bizarre feature that spotties share with all other wrasses is that they can change sex. All spotties begin life as females, and then at a length of 13–19 cm and age of 3–4 years, the largest fish may turn into males. But not all spotties become males: a complex social structure controls this process. Males defend territories against each other, especially in winter–spring during the spawning period. They maintain a harem of females within their territories, so the sex ratio is strongly biased towards females. When a male dies, the dominant female in the harem changes sex over a few days and takes over control of the harem and territory.

Spotty female MF

Female spotty  Photo: Malcolm Francis

It’s easy for spotties (and us!) to tell males and females apart because they have different colour patterns. Females have a large central brown–black spot in the middle of the body (hence their common name) whereas males have an irregularly shaped row of blackish spots or blotches high up on the back.

Spotties can be infuriating to photograph because they are always moving. They are curious too, and will come and check you out, but they don’t stay long. A little knowledge of their behaviour can help you to study them more closely: male spotties continuously patrol their territories, swimming around their boundaries in a well-defined route. When you figure out part of that route, just stay in the same place for several minutes, and you should see him come swimming along past the same point.

Next time you see a spotty, spend some time studying it more closely: there is a lot more to spotties than meets the eye.