Jansen’s Wrasse

Thalassoma Jansenii
Jansens Wrasse - Marinewise © 2024 MarineWise

Quick Facts

Scientific name Thalassoma Jansenii
Family Wrasse / Labridae
Size Up to 20 cm (7.87 in)
Weight Up to .25 kg (.55 lb)


Habitat & AU Distribution Shallower coastal waters amongst reefs on outer edges, slopes & drop offs
Depth Range 1 - 30 m (100 ft)
Jansen's Wrasse Distribution

Interesting Info

  • The Jansen’s wrasse is a species of marine fish found across Australia from Western Australia, the Northern Territory and Queensland. It is also well known in other parts of the Indo-Pacific region.
  • The Jansen’s wrasse can exhibit different colours and patterns depending on the region and the sex of the individual. While the species is typically described as having a greenish-blue head, yellow back, and pinkish-white underbelly, some individuals may appear black and white. Male Jansen’s wrasses also tend to be more colourful than females, with a range of hues from blue to green to yellow.
  • The species was named after the Dutch zoologist Pieter Bleeker’s friend, E. Jansen, who was an officer in the Dutch East Indies army.
  • The fish feeds on a variety of small invertebrates and crustaceans, including crabs, shrimps, and small snails.
  • The species is hermaphroditic, with females changing to males when the dominant male in a group dies.
  • During breeding season, which typically occurs during the warmer months of the year, males establish territories and engage in courtship displays to attract females. Once a pair has formed, the female will lay eggs in a nest that the male has prepared. The male will then fertilise the eggs and guard the nest until the eggs hatch.
  • The estimated lifespan is between 5 – 8 years in the wild.
Species Interaction

Aquarium, Snorkeling & Diving

Jansen’s wrasse is a popular aquarium fish due to its attractive appearance and active swimming behaviour. It is important to note that Jansen’s wrasse requires a large tank with plenty of swimming space. Jansen’s wrasse are also a relatively bold and curious species, and they may approach snorkelers and divers if they feel unthreatened.

Scientific Classification

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Family: Labridae

Genus: Thalassoma

Species: Thalassoma Jansenii

Conservation Status

Jansen’s wrasse is listed as a species of “Least Concern” on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. However, in Australia, the species is protected under various state and federal legislation, such as the Fisheries Management Act 1994 and the Environment Protection and Biodiversity Conservation Act 1999.

Jansen’s Wrasse
As Aquarium Fish

Care Level: Moderate to difficult

Temperament: Semi-Aggressive

Diet: Carnivore

Reef Compatible: Yes

Minimum Tank Size: 100 gallons

Recreational Viewing
- Snorkeling & Scuba

Finding: Easy

Temperament: Semi-Aggressive

Location: Inner Reef, Outer Reef, Lagoon

Danger: None