The Marine Life Society of SA was recently asked which species of sea slugs (which include nudibranchs) are found in the Port (Adelaide) River. We’ve only just started exploring the river underwater, so the list below is very much a work in progress. Prior to 2017, as far as we are aware, the river was largely unexplored (by divers at least). I suspect the primary reason for the Port River system remaining overlooked for so long, was its reputation for historically high pollution loads, which included sewage, industrial effluent and storm water. Since the closure of Penrice’s soda ash factory in 2013, water quality in the river has improved significantly. This has made exploration a far more attractive proposition, so much so that Experiencing Marine Sanctuaries even held group guided snorkeling sessions at Garden Island for the first time in February and March, 2019. From our short spate of explorations between 2017 and 2019, 14 species of sea slugs have been recorded in the “river” which includes all marine waters from the mouth at Outer Harbour past St Kilda, through the inner harbour and reaching to the southern extent of West Lakes.
I’ve chosen to lump the sea slugs into three categories: the native species, the established exotics and the seasonal bloomers based on observations of their distribution and seasonality. The data set is very small, so it may yet prove to be that some “season bloomers” are actually established in the Port River and populations are sustained year-round (just in places we don’t look regularly, like the inner harbour or West Lakes).
The sighting data supporting this list is available on iNaturalist, with plenty of photographic observations. The “species” tab is ideal for helping to identify a sea slug by quick visual comparison. Common names for each species are linked to corresponding pages on iNaturalist, where you’ll find photos, locations of sightings, taxonomic info and more. No use reinventing the wheel, hey!
|Air-breathing limpet||Siphonaria||diemenensis||Native, common at Outer Harbour|
|Black-margined sea slug||Elysia||expansa||Seasonal bloomer, seen in Spring in inner harbour and at Mutton Cove. First recorded in Port River by Steve Reynolds and Dan Monceaux, September 2018. Specimens collected and deposited at SA Museum.|
|Boodlea sapsucker||Ercolania||boodleae||Seasonal bloomer, only one bloom photographed. First recorded in SA by Dan Monceaux, August 2017.|
|Brazilian aeolid||Spurilla||braziliana||Established exotic, found in West Lakes and near Garden Island. First recorded in Port River by Dan Monceaux, April 2019.|
|Brown bubble shell||Bulla||quoyii||Shells sparsely distributed through system. No live specimens recorded yet.|
|Four-colour nudibranch||Godiva||quadricolor||Established exotic, distributed through the system. A specimen has been collected and is at the SA Museum awaiting genetic analysis. First recorded in SA in June 2017 by Dan Monceaux.|
|Hedgpeth’s dorid||Polycera||hedgpethi||Established exotic found near Garden Island and Mutton Cove|
|Onchidorididae (family)||?||?||Awaiting identification. Found at New Port. Photographed but not collected.|
|Saint Vincent’s Nudibranch||Hypselodoris||saintvincientius||Native, found in West Lakes.|
|Southern Baeolidia||Baeolidia||australis||Native, found in West Lakes.|
|Undescribed species||Sclerodoris||sp. RB1||Native, abundant in West Lakes. A specimen has been collected and is at the SA Museum awaiting description.|
|Verco’s chromodorid||Verconia||verconis||Native, found in West Lakes.|
|Winged thecacera||Thecacera||pennigera||Exotic, one sighting only at Outer Harbour.|