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Nudibranch on the rise in Tasmanian waters.

Tyson Jones @ Redmap, 01 Jun 2023.

Have you seen a Crowned Nudibranch in Tasmanian waters? You can help track the presence and distribution of this species around the state.

  • The first Crowned Nudibranch (Polycera capensis) officially recorded in Tasmania: located on the wreck of the Troy D by Redmapper Phillip White in 2014 - Phillip White

  • Polycera capensis - Adventure Bay, Bruny Island - Tarn Hingston

  • Polycera capensis - Blackmans Bay - Joel Williams

  • Polycera capensis - Blackmans Bay -Joel Williams

The Crowned Nudibranch (Polycera capensis), a species native to the southern coastline of Africa, appears to be taking up residency in the waters of Tasmania, Australia.

Believed to have been introduced to mainland Australia whilst attached to Bryozoans fouled to the hulls of ships, this hermaphroditic Gastropod’s population has largely been concentrated around the Central New South Wales coastline extending from Sydney in the south, to Port Stephens in the north. In recent years however, this Nudibranch appears to be extending it's southern Australian range.

In 2014, the first notable Tasmania detection of this species was made by Phillip White, who found the colourful sea slug whilst diving on the wreck of the Troy D, located off Maria Island on the states east coast.

Phillip’s sighting and submission to Redmap (find here) had been the first and only known record of this species occurring in the state until December 2022.

In the proceeding months of December 2022 and January 2023, Redmap had received a further 4 reportings (see: Sighting 1, Sighting 2, Sighting 3 & Sighting 4) of the species being sighted across various locations in Tasmania's Southeast.

We're interested to know: 1. Could this indicate a recent successful settlement of the Crowned Nudibranch to Tasmania? 2. Is this a persistent population, or will the presence of this species decline during Tasmania's colder months? 3. Do you have any knowledge of this species occuring in Tasmania prior to 2014?

To answer these questions, we need your help!

If you sight a Crowned Nudibranch, please log it with Redmap and help us track the movements of this species!

Things to look out for:

Habitat: Rocky reef structure, 0 – 30 m depth, in close proximity to Bryozoans (their primary food source).

Size: Up to 50 mm

Colouration: Colour variable, often grey or white base colour with black and yellow/orange longitudinal stripes. 6 yellow projections from the head with black gills and rhinophores. 2 yellow projections sit alongside the gills.

Location hotspots: South eastern Tasmania; Blackmans Bay, Kingston Beach, Tinderbox Marine Reserve, Bruny Island, Maria Island and surrounds.


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