With seven successful Melbourne Sea Slug Census events to date, our records of sea slug species found in Victorian coastal waters are continuing to grow. Collecting photos of sea slugs present at different times throughout the year will enable us to monitor these species and track any changes, but we’ll need your help!

The Eighth Melbourne Sea Slug Census will be held between Friday 5 and Monday 8 March. March proves to be a popular time for the Sea Slug Census project, with 4 separate Census events being held across the country and one in Vanuatu!

While our “official” Sea Slug Census identifier is Melbourne, we accept photos from all over the Victorian coast. See here for details on how to submit your photos.

If you are heading to the coast during this time, please remember to follow all advice from health and environmental authorities around current Covid-19 restrictions, access to sites and water quality. More information about current restrictions can be accessed at the Victorian government coronavirus page and Parks Victoria. Take care and stay safe while enjoying our wonderful wild spaces.


In Partnership with the Melbourne Sea Slug Census:-

The Sea Slug Census is supported by the Victorian Government.

Caption: Tambja verconis, a nudibranch commonly spotted in Port Phillip Bay. Photo Liz Harper

What is a sea slug and how will you know if you’ve found one?

Sea slugs are actually snails i.e. they are sea snails (marine gastropod molluscs) that have seemingly lost their shells. Also known as nudibranchs, they are found in most marine habitats, occurring in shallow rock pools and in the deep sea. Knowing when you find one can be easy when they are the size of a football, or extremely difficult when they are smaller than the nail on your pinkie finger. Generally, if it is in saltwater and it moves like a slug it is most likely a ‘sea slug’. If you are unsure, take a photo and we will let you know.

Sea Slugs are one of the most popular and most photographed groups of marine invertebrates, with ~400 species known in Victoria. They are excellent indicators of environmental change because they have rapid life-cycles (less than 12 months), very specific food requirements, and respond to changing oceanographic conditions.

Yet there is very little basic knowledge on their diversity, distribution and ecology. To learn more about them we teamed up with Southern Cross University to have Victoria’s first Sea Slug Census in Port Phillip Bay, Westernport Bay and surrounds. The information gathered during Sea Slug Censuses will help marine scientists to update knowledge about the diversity and distribution of this spectacular group of molluscs.

To learn more about sea slugs in Victoria, check out these links:

A Museum Victoria field guide – Nudibranchs and related molluscs

Port Phillip Bay Taxonomic Toolkit

Australian Geographic – Nudibranchs: indicators of climate change

Facebook group for nudi-nerds and info on SSC events around the country (and world!)

Contributing to this project is simple! All you need to do is take a photo of any sea slug you see if you’re out and about on the coast during Census times. Your photo will be identified by experts to confirm when and where we are seeing different species of sea slug in Victorian waters. All data from the Melbourne Sea Slug Census goes towards the Sea Slug Census project, a community based initiative to document the biodiversity of our oceans through collaboration between divers and scientists. See the Sea Slug Census facebook group for details on other Census activities being held all around Australia- and even further abroad!

Download guidelines for the March 2021 Census

If you are heading to the coast during this time, please remember to follow all advice from health and environmental authorities around current Covid-19 restrictions (including social distancing), access to sites and water quality. More information about current restrictions can be accessed at the Victorian government coronavirus page and Parks Victoria. Take care and stay safe while enjoying our wonderful wild spaces.


Photographing sea slugs for identification:

To help our experts with their identification, try to get a clear shot of the slug’s body from the side and/or include as many creature features (rhinophores, gills/cerata, oral tentacles) as possible. As always when out and about in nature, be mindful of limiting your impact on your subject and their surrounds.

A note on water quality if you’re out exploring our coast:

Heavy rain can impact water quality on our coasts, especially after fires and periods of smoke haze. In general the EPA recommends avoiding swimming near stormwater or river outlets 24–48 hours after heavy rain. Within Port Phillip Bay, you can check your local beach conditions at the Yarra and Bay Beach Report- https://yarraandbay.vic.gov.au/

We’re very pleased to share with you all the stunning entries we received in our Southern Sea Slugs Photo Competition. These talented photographers certainly met the brief by showcasing how wonderful and diverse our temperate species really are.

It might come as no surprise that the competition was dominated by those beautiful dorid and aeolid nudibranchs, but we did have one colourful headshield slug representing the non-nudi species!

Photos were judged by Dr Julian Finn of Museums Victoria. Julian is a researcher and museum curator focusing on marine invertebrates. He is also a talented photographer and cameraman, and his images are featured in many field guides as well as Museum Victoria’s Marine Life Exhibition. You can check out some of his work, both in marine science and visual storytelling, here.

Winning Photo

PT Hirschfield, Two Verconia verconis

The award for winning photo goes to PT Hirschfield, for this incredible shot of two Verconia verconis crawling over their food sponge. In his judging Julian noted:

This image features a pair of chromodorid nudibranchs Noumea [Verconia] verconis, that imitate the colour and shape of the sponge they feed on.  

A highlight of this image is the framing, with the forward-facing individual in the foreground and the rear-facing individual in the background. This framing produces a superb image that is both pleasing to the eye and extremely informative. By providing two perspectives of the same species, the viewer can gain a greater understanding of the morphology of this intriguing animal and fully appreciate its beauty.”

Congratulations PT, fantastic work!


Runners Up

Nick Shaw, Phyllodesmium macphersonae

A striking shot of this fascinating aeolid. Julian had this to say about Nick’s photo:

This image features an aeolid nudibranch Phyllodesmium macphersonae with deep blue, yellow-tipped cerata, each containing a duct of the digestive tract. 

The orientation of the subject in the frame makes this image a standout. With the nudibranch facing the lens, and with sufficient depth of field, the key features (i.e. the oral appendages, smooth rhinophores and anterior cerata) are all in focus. The rear of the animal blurs smoothly, giving the image depth. An impressive image.”

Astute readers may also recognise this one from way back in the very first Melbourne Sea Slug Census report from April 2018! Well done Nick.


Liz Harper, Ceratosoma brevicaudatum

This beauty was captured in fine detail here in Liz’s shot- you can clearly see even the minute eggs coiling around inside the egg ribbon that the slug is laying down. Julian notes:

This image features the chromodorid nudibranch Ceratosoma brevicaudatum, reportedly Victoria’s most common nudibranch and, on account of its large size, often the first nudibranch observed by new divers and snorkelers. 

Unlike most images of this species, this image includes both the animal and a coil of freshly laid eggs. The framing and exposure of this image draws the viewers eye from the nudibranch to the eggs. The orientation of the nudibranch in the image results in all of the key structures (i.e. rhinophores, gills and branchial appendages) being in focus. This makes for a very pleasing, informative and natural-looking image.

Well done Liz for an exceptional entry!


Please enjoy the full gallery of competition entries:

March 2020

Between 13-16 March 2020 people right across Port Phillip Bay, Westernport and beyond submitted their findings to the seventh Melbourne Sea Slug Census. All in all, we had submissions from 14 individuals or teams and as we’ve come to expect there were some fantastic finds. As Steve Smith of the SSC project put it, our “accomplished spotters and photographers…. makes viewing the report a real pleasure”. We hope you agree, and you can download the report for your own viewing below.

We recorded 61 species of sea slug for March 2020, up from the same time last year, and we’re expanding our list of recorded species with each new Census. Well done to everyone, but in particular, here are the winners of our regular Census awards!

Best photo: John Olden, Tambja verconis

What a fantastic shot of one of Victoria’s most iconic nudibranchs. In his letter to us with the results of his identifications Bob Burn stated “I keep going back to this shot because it clearly shows the internal detail of the ribbing within the accessory sensing organ. I know of only one other image showing this fully open and in use.” Great work John for capturing some science in your art.

Steve nominated Nick Shaw’s Trinchesia sp. RB2 as an honourable mention in this category. This is a great shot of this colourful aeolid, clearly showing detailed creature features such as the tiny eyespots and the striking, bright blue oral tentacles typical of this species.


Most interesting species: Rebecca Lloyd, Elysia sp. RB4

The most interesting species as judged by Bob Burn, Rebecca’s striking Elysia is the most easterly report of this species to date. Elysia sp. RB4 is known from South Australia and western Victoria, but Rebecca spotted it at Beaumaris in Port Phillip Bay. It is distinguished from the similar looking Elysia furvacauda by the presence of small white pustules on the parapodial margins (in E. furvacauda the margins are smooth). Great find Rebecca, and it goes to show how having the extra pairs of eyes (and cameras!) out in the water is expanding our knowledge of the behaviour and distribution of these animals.

An honourable mention in this category goes to Corinne Telford for her Tamanovalva babai. Steve Smith noted that this tiny species of sap-sucking slug is very hard to spot amongst its food source, and Corinne actually found 2 different individuals! It has been described by Bob Burn as having a limited range, endemic to eastern SA, central Vic and northern Tas, and Steve himself has never seen one. Well done Corinne.

Ultimate nudi hunters: Paul Sorenson and Rebecca Lloyd

Again the award for most species spotted is a tie between two enthusiastic divers- well done Paul and Rebecca for finding 30 species apiece.

Caption: Paul Sorenson’s shot of two Doriopsilla carneola side by side shows how much variation in colour (and size) we see in one of our favourite “orange blobs”!

Thanks again to everyone who contributed photos to the March Census, and for your understanding around the decision to cancel the July Census. COVID-19 is creating a lot of uncertainty, and while we are hoping to schedule another Census this year, we will continue to monitor the advice and regulations from health authorities before making a decision. Please stay safe out there.

March 2020

250 photos were submitted to the Census for March, and with everything going on we had to rely on snail mail to get them through to our expert Bob Burn for identification and judging. We ended up recording 61 species of sea slug! And we’re still adding species to our project records each new Census. Well done everyone.

Download full report for March 2020

January 2020

Smoke from the recent bushfires had severely impacted much of the Victorian coast this weekend, but around 100 intrepid nudi hunters made the best of conditions and submitted over 200 photos to the Census. We still recorded 72 species of sea slugs! And the quality of photos made Bob Burn’s judging of the competition a tricky task. Thanks to everyone who submitted to our first true summer edition of the Census.

Download full report for January 2020

October 2019

What can we say other than we were blown away by the number of nudis spotted this time! 88 species to be exact, some new additions to our records and a few entries that left our experts pleasantly surprised. October certainly seems like a busy time for both our nudis and the keen citizen scientists who search for them!

Download full report for October 2019

June 2019

Our winter wonderland edition of the Melbourne Sea Slug Census saw many people brave the cold water, but only 6 groups of nudi hunters managed to photograph slugs during that time. Still, 29 species of slug were sighted, with some really beautiful submissions and new species to add to the Melbourne census records. A commendable effort for a very chilly weekend!

Download full report for June 2019

March 2019 

Melbourne Sea Slug Census III was held over the 15-18 March. Many groups reported seeing far less slugs than expected, but all in all, over 100 nudi hunters that were out and about across the weekend recorded 48 individual species between them. Well done everyone!

Download full report for March 2019

October 2018 

The second Melbourne Sea Slug Census took place on the 12-15 October. Over four days, enthusiastic teams and individuals managed to find an incredible 75 species of sea slugs! It was a fantastic effort and the overall quality of images submitted impressed everyone involved in sorting and identification. Some of the species photographed during this Census have rarely been seen in Victoria, even by our leading experts!

Download full report for October 2018

April 2018

The first Melbourne Sea Slug Census was held on the on the weekend of 21-22 April. Thank you to the over 150 people who photographed different sea slugs (nudibranchs) in Port Phillip Bay, Western Port Bay and surrounds and submitted them to ReefWatch. Together, we found a total of 53 species of nudibranch!

Download full report for April 2018

Nicole Mertens, ReefWatch Project Officer