Big thanks to Emma Royer for sending this pic of a Common Violet Snail (Janthina janthina) found on Point Lonsdale dog beach on 26-11-2016. There were 30-40 or so washed up among their preferred prey: By-the-Wind-Sailors (Velella velella) and Bluebottles (Physalia physalis). These free-floating surface-dwellers are well out of reach for most marine snails that live on the sand or rocky seabed; but Janthina janthina secretes mucous containing air bubbles from their foot. This enables them to float just below the surface among their prey.
These species prefer warmer ocean waters; and according to the Atlas of Living Australia, only a couple of Common Violet Snails have been recorded previously in Victoria (between Lakes Entrance and Mallacoota). So what’s changed?
Figure 4 in the Australian Bureau of Meteorology Special Climate Statement 58 (October 2016) shows that May to September 2016 sea surface temperatures around 80% of the Australian coast (clockwise, roughly from Broome to the South Australian border) were either ‘highest on record’ or ‘very much above average’.