Species focus: Sandager's wrasse

Eight facts you should know about the Sandager's wrasse

October 13, 2022
Arguably New Zealand's most noticeable fish species for all levels of diver
Arguably New Zealand's most noticeable fish species for all levels of diver
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Sandager’s wrasse (Coris sandeyeri)

The Sandager’s wrasse is one of around 30 labrid (or large family of fish) species that have been found in New Zealand with over 500 wrasse and related species known worldwide. This is arguably the most colourful and charismatic wrasse in our waters, with the large males displaying gaudy purple and yellow colours.

Like all labrids, Sandager’s exhibits strong sexual dimorphism, with the males not only being far more colourful than the cream and fawn coloured females, but also considerably larger, some reaching almost half a metre long.

Another quite remarkable trait shared by all labrids is the ability to change sex. All Sandager’s begin life as females, with some changing later to become males, a life history strategy termed protogynous hermaphroditism.

The male vigorously defends both his territory and his harem of females. The young “attendant” yellow-striped juveniles also hang around this territory. These young females regularly serve as cleanerfish for other fish species, and it is a common sight to see them being chased and pestered by legions of demoiselles or trevally looking for a parasite clean.

A juvenile Sandager's wrasse
A juvenile Sandager's wrasse

The interesting name of the Sandager’s wrasse has its origin with a former lighthouse keeper. Andreas Fleming Stewart Sandager who was the lighthouse keeper on the Mokohinau Islands in the 19th Century. Being a fond naturalist, it was he who first collected a specimen of the wrasse which, after being described all the way back in 1884, was named in his honour.

Sandager’s Wrasse main diet consists of small invertebrates such as brittlestars and shellfish that live in the shell and sand on the reefs edge. However, they have also been known to eat nesting fish eggs, such as those of demoiselles and triplefins.

The female Sandager's wrasse lacks the bright banding of the male.
The female Sandager's wrasse lacks the bright banding of the male.

They are also very attracted to divers, and will readily take food from anyone willing to offer it.

Another distinctive trait is that they spend the night buried in the sand, covered in a small coating of mucous, rising out of the sand as day breaks.

8 interesting things you should know about Sandager's wrasse

  1. Named for the former Mokohinau Islands’ lighthouse keeper, Andreas Sandager
  2. Exhibit extreme sexual dimorphism, in size and in particular colouration
  3. Males defend a territory and harem of females
  4. All Sandager’s start life as females, and some change sex
  5. Sleep under the sand each night
  6. Eat mostly small invertebrates and fish eggs
  7. Very diver positive!
  8. Wrasse is derived from the old Celtic word for “old hag”

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Paul Caiger

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